JP7816624B2 - Electricity storage device and manufacturing method thereof, and exterior material for electricity storage device and manufacturing method thereof - Google Patents

Description

This disclosure relates to an electricity storage device and a manufacturing method thereof, as well as an exterior material for an electricity storage device and a manufacturing method thereof.

Various types of electricity storage devices have been developed to date, but in all of them, exterior materials are essential components for sealing the electricity storage device elements, such as electrodes and electrolytes. Traditionally, metal exterior materials have often been used as exterior films.

On the other hand, in recent years, with the increasing performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, and other devices, there has been a demand for energy storage devices to be thinner and lighter, as well as more diverse in shape. However, the metal exterior films that have been widely used up until now have the drawback of being difficult to adapt to the increasing variety of shapes, and there are also limitations to how light they can be made.

In recent years, therefore, film-like laminates in which a base layer, a barrier layer, and a heat-sealable resin layer are sequentially laminated have been proposed as exterior films that can be easily processed into a variety of shapes and can be made thinner and lighter (see, for example, Patent Document 1).

Patent Document 2 also discloses an example of an electricity storage device. This electricity storage device includes an electrode assembly and an exterior body that seals the electrode assembly. The exterior body includes an exterior film that wraps the electrode assembly and a lid that is joined to the exterior film. This electricity storage device is manufactured, for example, by housing the electrode assembly inside a cylindrical exterior film and closing the opening of the cylindrical exterior film with the lid. The side of the lid and the exterior film are joined, for example, by heat sealing.

Japanese Patent Application Laid-Open No. 2008-287971 Japanese Patent Application Laid-Open No. 2022-123686

An exterior body comprising an exterior film that encases an electrode assembly and a lid that is joined to the exterior film (exterior material for an electricity storage device), as disclosed in Patent Document 2, is useful, for example, as an exterior body for a large electricity storage device.

Such an exterior body has a sealing portion (joint) between the exterior film (exterior material for an electricity storage device) and the lid. Through research, the inventors of the present disclosure discovered a new problem: cracks occur in the sealing portion of the exterior film when the electricity storage device is repeatedly exposed to high and low temperature changes.

Under these circumstances, the primary objective of this disclosure is to provide an electricity storage device that uses an exterior body including an exterior film (exterior material for an electricity storage device) that encases an electrode assembly and a lid, and that is designed to prevent cracks from occurring in the sealing portion between the exterior film and the lid when the electricity storage device is repeatedly exposed to high and low temperature changes.

The present disclosure also aims to provide an exterior material for an electricity storage device that uses an exterior body including a lid and an exterior material for an electricity storage device that encases an electrode assembly, and that is capable of suppressing the occurrence of cracks in the sealing portion between the exterior material for an electricity storage device and the lid when the electricity storage device is repeatedly exposed to high and low temperature changes.

The inventors of the present disclosure conducted extensive research to solve the above-mentioned problems. As a result, they discovered that in an electricity storage device including an electrode assembly and an exterior body that seals the electrode assembly, the exterior body includes an exterior film that wraps the electrode assembly and a lid that, together with the exterior film, seals the electrode assembly; the exterior film is composed of a laminate including at least a barrier layer and a heat-sealable resin layer; and at a position where the heat-sealable resin layer of the exterior film is heat-sealed to the lid, a cross section obtained by cutting the barrier layer perpendicularly from the surface of the barrier layer in a direction perpendicular to the rolling direction of the barrier layer is subjected to crystal analysis using the EBSD method. The area-average angular difference of GOS (Grain Orientation Spread) is 2.50° or less, where the grain boundary of the barrier layer is defined as 5°. This suppresses the occurrence of cracks in the sealing portion of the exterior film with the lid when the electricity storage device is repeatedly exposed to high and low temperature changes.

The present disclosure has been completed based on these findings and further investigations. That is, the present disclosure provides the inventions of the following aspects.
An electricity storage device,
An electrode body;
an exterior body that seals the electrode body,
The exterior body is
an exterior film that wraps the electrode body;
a lid that seals the electrode body together with the exterior film,
the exterior film is composed of a laminate including at least a barrier layer and a heat-sealable resin layer,
the barrier layer has an area-average angular difference of GOS (grain orientation dispersion) of 2.50° or less, where the grain boundary is defined as 5°, obtained by performing crystal analysis by an EBSD method on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position where the heat-sealable resin layer of the packaging film is heat-sealed to the lid;
Energy storage device.

Furthermore, the inventors of the present disclosure conducted extensive research to solve the above-mentioned problems. As a result, they discovered that in an electrical storage device packaging material composed of a laminate including at least a barrier layer and a heat-sealable resin layer, at a position where the heat-sealable resin layer of the electrical storage device packaging material and a polypropylene plate are heat-sealed under conditions such that the thickness of the heat-sealable resin layer is 20% to 80%, the area-average angular difference of GOS (Grain Orientation Spread) obtained by performing crystal analysis using the EBSD method on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer is 2.50° or less, where the grain boundary is defined as 5°. This suppresses the occurrence of cracks in the sealing portion of the electrical storage device packaging material with the lid when the electrical storage device is repeatedly exposed to high and low temperature changes.

The present disclosure has been completed based on these findings and further investigations. That is, the present disclosure also provides the inventions of the following aspects.
An exterior packaging material for an electricity storage device, which is composed of a laminate including at least a barrier layer and a heat-sealable resin layer,
the barrier layer has an area-average angular difference of GOS (grain orientation dispersion) of 2.50° or less, when a grain boundary is defined as 5°, obtained by performing crystal analysis by an EBSD method on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer, at a position where the heat-fusible resin layer of the electrical storage device packaging material and a polypropylene plate are heat-fusible under conditions such that the thickness of the heat-fusible resin layer is 20% or more and 80% or less;
Exterior material for energy storage devices.

The present disclosure makes it possible to provide an electricity storage device that uses an exterior body including an exterior film that encases an electrode body and a lid, and that is capable of suppressing the occurrence of cracks in the sealing portion between the exterior film and the lid (more specifically, the occurrence of cracks in the barrier layer) when the electricity storage device is repeatedly exposed to high and low temperature changes. The present disclosure also makes it possible to provide a method for manufacturing such an electricity storage device.

The present disclosure also provides an electrical storage device exterior material that suppresses cracking in the sealing portion between the electrical storage device exterior material and the lid (more specifically, cracking in the barrier layer) when the electrical storage device is repeatedly exposed to high and low temperature changes in an electrical storage device that uses an exterior material that encases an electrode assembly and includes a lid. The present disclosure also provides a method for manufacturing the electrical storage device exterior material, and an electrical storage device that uses the electrical storage device exterior material.

1 is a perspective view illustrating an example of an electricity storage device according to the present disclosure. FIG. 2 is a cross-sectional view taken along line AA in FIG. FIG. 2 is a schematic diagram illustrating an example of a lid according to the present disclosure. 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior film of the present disclosure. 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior packaging material for an electricity storage device according to the present disclosure. 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior packaging material for an electricity storage device according to the present disclosure. 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior packaging material for an electricity storage device according to the present disclosure. 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior packaging material for an electricity storage device according to the present disclosure. FIG. 2 is a schematic diagram illustrating a method for housing an electricity storage device element in a package formed from the exterior packaging material for an electricity storage device of the present disclosure. 1 is a perspective view showing an example of an electricity storage device according to the present disclosure that uses an exterior material for an electricity storage device according to the present disclosure. 11 is a cross-sectional view taken along line AA in FIG. 10. FIG. 2 is a schematic diagram illustrating an example of a lid according to the present disclosure.

In the energy storage device of the present disclosure, the exterior film includes an electrode assembly and an exterior body that seals the electrode assembly. The exterior body includes an exterior film that wraps the electrode assembly and a lid that seals the electrode assembly together with the exterior film (exterior material for an energy storage device). The exterior film is composed of a laminate including at least a barrier layer and a heat-sealable resin layer. At the position where the heat-sealable resin layer of the exterior film is heat-sealed to the lid, the barrier layer has a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer (i.e., perpendicular to the surface of the barrier layer), and the area-average angle difference of the GOS (grain orientation dispersion) obtained by performing crystal analysis using the EBSD method, where the grain boundary is defined as 5°, is 2.50° or less. By having this configuration, the energy storage device of the present disclosure is able to suppress cracking at the sealing portion of the exterior film with the lid.

The electrical storage device packaging material of the present disclosure is composed of a laminate including at least a barrier layer and a heat-sealable resin layer, and the barrier layer is characterized in that, at a position where the heat-sealable resin layer of the electrical storage device packaging material and a polypropylene plate are heat-sealed under conditions such that the thickness of the heat-sealable resin layer is 20% to 80% or less, the area-average angular difference of the GOS (grain orientation dispersion) is 2.50° or less, when the grain boundary is defined as 5°, as obtained by performing crystal analysis using the EBSD method on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer. By having this configuration, the electrical storage device packaging material of the present disclosure is able to suppress the occurrence of cracks in the sealing portion of the electrical storage device packaging material with the lid.

The electricity storage device and exterior film (hereinafter also referred to as an exterior material for an electricity storage device) of the present disclosure are described in detail below. In this disclosure, numerical ranges indicated by "to" mean "greater than or equal to" or "less than or equal to." For example, 2 to 15 mm means 2 mm or greater and 15 mm or less. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Separately described upper and lower limits, upper and lower limits, or lower and lower limits may be combined to form respective numerical ranges. In the numerical ranges described in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.

In the case of exterior films and exterior materials for energy storage devices, the MD (Machine Direction) and TD (Transverse Direction) of the barrier layer 52 and barrier layer 3 (described below) during their manufacturing process can typically be determined. For example, when the barrier layer 52 and barrier layer 3 are each made of a metal foil such as an aluminum alloy foil or a stainless steel foil, linear streaks known as rolling marks are formed on the surface of the metal foil in the rolling direction (RD) of the metal foil. Because the rolling marks extend along the rolling direction, the rolling direction of the metal foil can be determined by observing the surface of the metal foil. Furthermore, during the manufacturing process of a laminate, the MD of the laminate typically coincides with the RD of the metal foil, so the MD of the laminate can be determined by observing the surface of the metal foil of the laminate and identifying the rolling direction (RD) of the metal foil. Additionally, since the TD of the laminate is perpendicular to the MD of the laminate, the TD of the laminate can also be determined.

Furthermore, if the MD of the exterior film cannot be determined due to rolling marks on the metal foil, such as aluminum alloy foil or stainless steel foil, it can be determined using the following method. One method for determining the MD of an exterior film is to observe the cross section of the heat-sealable resin layer of the exterior film using an electron microscope to confirm the sea-island structure. In this method, the direction parallel to the cross section where the average diameter of the island shapes in the direction perpendicular to the thickness direction of the heat-sealable resin layer is largest can be determined as the MD. Specifically, the sea-island structure is confirmed by observing the longitudinal cross section of the heat-sealable resin layer and each cross section at an angle of 10 degrees from the direction parallel to the longitudinal cross section (a total of 10 cross sections) using an electron microscope. Next, the shape of each individual island is observed in each cross section. For each island shape, the linear distance connecting the leftmost end perpendicular to the thickness direction of the heat-sealable resin layer to the rightmost end in that vertical direction is defined as the diameter y. For each cross section, the average of the diameters y of the top 20 island shapes in order of largest diameter y is calculated. The direction parallel to the cross section where the average diameter y of the island shape is largest is determined to be the MD.

<1-1. Configuration of the electricity storage device>
FIG. 1 is a perspective view schematically illustrating an electricity storage device 10. FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1. FIG. 3 is a schematic view showing an example of a lid body 60. FIG. 4 is a cross-sectional view showing an example of a laminated structure of an exterior film 50 included in the electricity storage device 10 of FIG. 1. In FIGS. 1 to 3, the arrow z direction (z1 direction and z2 direction) indicates the thickness direction of the electricity storage device 10, the arrow x direction (x1 direction and x2 direction) indicates the width direction of the electricity storage device 10, and the arrow y direction (y1 direction and y2 direction) indicates the depth direction of the electricity storage device 10. The directions indicated by the arrows x, y, and z are common to the subsequent figures.

The energy storage device 10 includes an electrode body 20, an electrode terminal 30, and an exterior body 40. The electrode body 20 includes electrodes (positive and negative electrodes) and a separator that constitute an energy storage component such as a lithium-ion battery, capacitor, all-solid-state battery, semi-solid battery, quasi-solid battery, polymer battery, all-resin battery, lead-acid battery, nickel-metal hydride battery, nickel-cadmium battery, nickel-iron battery, nickel-zinc battery, silver oxide-zinc battery, metal-air battery, polyvalent cation battery, or capacitor. In this disclosure, the shape of the electrode body 20 is, for example, an approximately rectangular parallelepiped. Note that "approximately rectangular parallelepiped" includes not only a perfect rectangular parallelepiped, but also a solid that can be considered a rectangular parallelepiped by modifying the shape of a portion of its outer surface, for example. The shape of the electrode body 20 may be, for example, a cylinder or polygonal prism.

The energy storage device 10 in Figures 1 and 2 includes two electrode terminals 30. The electrode terminals 30 are metal terminals used for inputting and outputting power to and from the electrode body 20. One end of the electrode terminal 30 is electrically connected to an electrode (positive or negative) included in the electrode body 20. The other end of the electrode terminal 30 protrudes outward from, for example, the edge of the exterior body 40. Note that the electrode terminal 30 need only be capable of inputting and outputting power to and from the electrode body 20, and does not, for example, need not protrude from the exterior body 40. For example, if the lid body 60 described below is made of a conductive material, the lid body 60 may also function as the electrode terminal 30. In this case, the lid body 60, which functions as an electrode terminal, may or may not protrude from the exterior body 40.

The metal material constituting the electrode terminal 30 is, for example, aluminum, nickel, or copper. For example, if the electrode body 20 is a lithium-ion battery, the electrode terminal 30 connected to the positive electrode is typically made of aluminum, and the electrode terminal 30 connected to the negative electrode is typically made of copper, nickel, or the like. The outermost layer of the electrode body 20 does not necessarily have to be an electrode, and may be, for example, a protective tape or a separator. The outer shape of the electrode body 20 is, for example, a rectangular parallelepiped.

The exterior body 40 seals the electrode body 20. The exterior body 40 includes an exterior film 50 and a lid 60. The exterior film 50 encases the electrode body 20. In Figures 1 and 2, the exterior film 50 is wrapped around the electrode body 20. The lid 60 is disposed on the side of the electrode body 20 in the y direction. In another example, the electrode body 20 may be housed inside an exterior film 50 configured in a cylindrical shape so that openings are formed at both ends in the y direction, and the openings may be closed by the lid 60. In yet another example, the electrode body 20 connected to the lid 60 may be housed inside an exterior film 50 configured in a cylindrical shape so that openings are formed, and the openings may be closed by the lid 60.

The exterior body 40 has a pair of main surfaces and a pair of side surfaces formed by the exterior film 50. In Figures 1 and 2, the pair of main surfaces are substantially the same size. The pair of side surfaces are also substantially the same size. The pair of main surfaces each have a larger area than the pair of side surfaces. The pair of lid bodies 60 are respectively disposed on the sides of the electrode body 20 so as to close the pair of openings. Note that in this disclosure, the main surfaces and side surfaces refer to the surfaces of the exterior body 40 excluding the lid bodies 60.

For example, one method involves cold-forming the exterior film 50 to form a storage section (recess) for accommodating the electrode assembly 20. However, forming a deep storage section using this method is not necessarily easy. Attempting to form a deep storage section (recess) using cold-forming (e.g., a molding depth of 15 mm) increases the likelihood of pinholes or cracks occurring in the exterior film 50, resulting in reduced battery performance. On the other hand, the exterior body 40 seals the electrode assembly 20 by wrapping the exterior film 50 around the electrode assembly 20, making it easy to seal the electrode assembly 20 regardless of its thickness. To reduce the dead space between the electrode assembly 20 and the exterior film 50 and improve the volumetric energy density of the energy storage device 10, it is preferable for the exterior film 50 to be wrapped so that it contacts the outer surface of the electrode assembly 20. Furthermore, in all-solid-state batteries, it is necessary to apply high pressure uniformly from the exterior surface of the battery to maximize battery performance. Therefore, it is necessary to eliminate the space between the electrode assembly 20 and the exterior film 50. Therefore, it is preferable for the exterior film 50 to be wrapped so that it contacts the outer surface of the electrode assembly 20. When wrapping the exterior film 50 around the electrode body 20, only one exterior film 50 may be wrapped, or multiple exterior films 50 may be wrapped. In addition to a mode in which the opposing surfaces of the exterior films 50 are heat-sealed, a mode in which the outer and inner surfaces of the exterior films 50 are heat-sealed is also preferred.

As shown in FIG. 4, the exterior film 50 is a laminate film having at least a barrier layer 52 and a heat-sealable resin layer 53. Details of each layer included in the exterior film 50 will be described later.

The lid body 60 may have any shape, such as a cylinder, prism, rectangular parallelepiped, or cube, and is made up of, for example, a resin material. Here, "made up of a resin material" means that, when the entire material making up the lid body 60 is taken as 100% by mass, the resin material content is 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. In other words, the material making up the lid body 60 can contain materials other than resin materials in addition to resin materials.

Specific examples of resins include thermoplastic resins such as polyester, polyolefin, polyamide, epoxy resin, acrylic resin, fluororesin, polyurethane, silicone resin, and phenolic resin, as well as modified versions of these resins. The resin material may also be a mixture of these resins, a copolymer, or a modified copolymer. Among these, heat-sealable resins such as polyester and polyolefin are preferred, with polyolefin being more preferred. When the resin material is a resin, the lid 60 may be molded using any molding method.

Specific examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymer polyesters. Copolymer polyesters include those in which ethylene terephthalate is the main repeating unit. Specific examples include copolymer polyesters in which ethylene terephthalate is the main repeating unit polymerized with ethylene isophthalate (hereinafter abbreviated as polyethylene (terephthalate/isophthalate)), polyethylene (terephthalate/adipate), polyethylene (terephthalate/sodium sulfoisophthalate), polyethylene (terephthalate/sodium isophthalate), polyethylene (terephthalate/phenyl dicarboxylate), and polyethylene (terephthalate/decane dicarboxylate). Among these, polybutylene terephthalate is preferred as the resin material, due to its enhanced heat resistance and pressure resistance.

Specific examples of polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; polypropylenes such as homopolypropylene, polypropylene block copolymers (e.g., propylene and ethylene block copolymers), and polypropylene random copolymers (e.g., propylene and ethylene random copolymers); propylene-α-olefin copolymers; and ethylene-butene-propylene terpolymers. When polyolefin resins are copolymers, they may be block copolymers or random copolymers. Among these, polypropylene is preferred as the resin material due to its excellent heat-sealing properties and electrolyte resistance.

The resin used as the resin material may contain a filler as needed. Specific examples of fillers include glass beads, graphite, glass fiber, and carbon fiber. By including the filler in the resin used as the resin material, the lid 60 can be made more resistant to deformation due to temperature changes.

The melt mass flow rate (measured at 230°C) of the resin material contained in the material constituting the lid 60 is preferably in the range of 1g/10min to 100g/10min, preferably in the range of 1g/10min to 80g/10min, preferably in the range of 1g/10min to 60g/10min, preferably in the range of 5g/10min to 100g/10min, preferably in the range of 5g/10min to 80g/10min, and more preferably in the range of 5g/10min to 60g/10min. The melt mass flow rate is measured in accordance with JIS K7210-1:2014.

The lid body 60 may be constructed to contain a conductive material. "Constructed to contain a conductive material" means that, when the entire material constituting the lid body 60 is taken as 100% by mass, the conductive material content is 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. In other words, the material constituting the lid body 60 can contain materials other than conductive materials in addition to conductive materials.

The conductive material that constitutes the lid body 60 is, for example, a metal material. The metal material that constitutes the lid body 60 is, for example, aluminum, aluminum alloy, nickel, copper, or copper alloy. For example, if the electrode body 20 is a lithium-ion battery, the lid body 60 connected to the positive electrode is preferably made of aluminum or an aluminum alloy. The lid body 60 connected to the negative electrode is preferably made of nickel, copper, or a copper alloy. The material that constitutes the lid body 60 connected to the negative electrode may be nickel-plated copper. The material that constitutes the lid body 60 may include recycled metal material. When the lid body 60 is made of a conductive material, the lid body 60 also functions as the electrode terminal 30, so the electrode terminal 30 can be omitted from the electricity storage device 10.

The lid body 60 may be configured such that at least a portion of the lid body 61 is covered with the covering body 62. In the lid body 60 of FIG. 3, the periphery of the lid body 61 (the periphery of the thickness portion) is covered with the covering body 62. The lid body 60 may be joined to the heat-sealable resin layer 53 of the exterior film 50 via the covering body 62. The covering body 62 is preferably configured to contain a resin material. The lid body 60 has the lid body 61 and the covering body 62 that joins the lid body 61 and the exterior film 50, and the covering body 62 may be configured to contain a resin (resin material). The definition of "comprising a resin material" with respect to the covering body 62 is the same as for the lid body 60.

When the lid body 60 is made of a conductive material, the lid main body 61 may be made of a conductive material, and at least a portion of the lid main body 61 may be covered by the covering body 62.

When the lid 60 contains a conductive material, the lid 60 may be bonded to the exterior film 50 via an adhesive film instead of a coating. Any adhesive film can be used as long as it can bond the exterior film 50 and the lid 60. The adhesive film is preferably a laminated film having at least a heat-sealable resin layer, a heat-resistant substrate layer, and a heat-sealable resin layer, in that order. The specifications for the heat-sealable resin layer of the adhesive film are the same as those for the heat-sealable resin layer 53. The materials constituting the heat-sealable resin layers on both sides of the adhesive film may be the same or different, and are selected appropriately based on the materials constituting the heat-sealable resin layer 53 of the exterior film 50 and the material constituting the lid 60. The material constituting the heat-sealable resin layer of the adhesive film on the side bonded to the lid 60 is preferably an acid-modified polyolefin resin graft-modified with an acid such as maleic anhydride. The heat-sealable resin layer of the adhesive film on the side that is bonded to the exterior film 50 is preferably made of the same type of material as the material that constitutes the heat-sealable resin layer 53 of the exterior film 50.

The heat-resistant substrate layer may be any film made of a heat-resistant resin, such as polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polymethylpentene (registered trademark), polyacetal cyclic polyolefin, polyethylene, or polypropylene, and may be unstretched or stretched. Polyethylene terephthalate is particularly preferred as it is inexpensive and strong.

The adhesive film preferably has adhesive properties. When the second sealing portion 80 (described below) is formed with the adhesive film disposed between the exterior film 50 and the lid 60, the adhesive film is less likely to shift position relative to the lid 60 and the exterior film 50. Adhesion can be imparted to the adhesive film by incorporating a tackifying resin into the heat-sealable resin layer of the adhesive film. Examples of tackifying resins include amorphous polyolefins. Examples of amorphous polyolefins include amorphous polypropylene and copolymers of amorphous propylene and other α-olefins. The content of the tackifying resin relative to the base material constituting the heat-sealable resin is preferably 10 to 20% by weight or less.

The lid body 60 has a first main surface located on the inside of the electricity storage device (the electrode body 20 side), a second main surface located on the outside of the electricity storage device, and four side surfaces that are heat-sealed to the heat-sealable resin layer 53 of the exterior film 50. The first main surface faces the electrode body 20. The second main surface is the surface opposite the first main surface.

When the lid body 60 is a cylinder, prism, rectangular parallelepiped, cube, or the like, it is preferable that the lid body 60 have a certain thickness in the thickness direction (y direction) so that deformation of the exterior body 40 is suppressed even when the energy storage device 10 is stacked. From another perspective, when the lid body 60 is a cylinder, prism, rectangular parallelepiped, cube, or the like, it is preferable that the lid body 60 have a certain thickness in the thickness direction (y direction) so that the lid joint of the lid body 60 can be suitably joined to the exterior film 50 when forming the second sealing portion 80. The minimum value of the thickness of the lid body 60 in the thickness direction (y direction) (the distance in the y direction between the first main surface and the second main surface) is, for example, 1.0 mm, more preferably 3.0 mm, and even more preferably 4.0 mm. The maximum thickness of the lid 60 in the y direction is, for example, 20 mm, preferably 15.0 mm, more preferably 10.0 mm, even more preferably 8.0 mm, and even more preferably 7.0 mm. The maximum thickness of the lid 60 in the y direction may be 10 mm or more. Preferred ranges for the thickness of the material constituting the lid 60 are 1.0 mm to 20.0 mm, 1.0 mm to 15.0 mm, 1.0 mm to 10.0 mm, 1.0 mm to 8.0 mm, 1.0 mm to 7.0 mm, 3.0 mm to 20.0 mm, 3.0 mm to 15.0 mm, 3.0 mm to 10.0 mm, 3.0 mm to 8.0 mm, 3.0 mm to 7.0 mm, 4.0 mm to 20.0 mm, 4.0 mm to 15.0 mm, 4.0 mm to 10.0 mm, 4.0 mm to 8.0 mm, and 4.0 mm to 7.0 mm. In this disclosure, when the lid body 60 is described as a cylinder, prism, rectangular parallelepiped, cube, or the like, this does not include embodiments in which the lid body 60 is made solely of a film as defined by the JIS (Japanese Industrial Standards) [Packaging Terminology] standard. The thickness of the lid body 60 may vary depending on the part of the lid body 60. When the thickness of the lid body 60 varies depending on the part, the thickness of the lid body 60 is the thickness of the thickest part.

1 and 2, the lid body 60 has a through-hole formed therein through which the electrode terminal 30 is inserted. The through-hole penetrates the first and second main surfaces of the lid body. When the electrode body 20 is stored, the electrode terminal 30 passes through the through-hole formed in the lid body 60 and protrudes to the outside of the exterior body 40. The small gap between the through-hole in the lid body 60 and the electrode terminal 30 is filled, for example, with resin. Note that in the energy storage device 10, the position from which the electrode terminal 30 protrudes to the outside can be selected arbitrarily. For example, the electrode terminal 30 may protrude to the outside from a hole formed on any of the six surfaces of the exterior body 40. In this case, the small gap between the exterior body 40 and the electrode terminal 30 is filled, for example, with resin. The electrode terminal 30 may protrude from between the lid body 60 and the exterior film 50, or from the first sealing portion 70 described below. In the electricity storage device 10, the lid body 60 and the electrode terminal 30 are provided as separate bodies, but the lid body 60 and the electrode terminal 30 may also be formed integrally. Note that if the electrode terminal 30 does not protrude from the edge of the exterior body 40, the lid body 60 does not need to have a through-hole formed therein.

In Figures 1 and 2, the exterior film 50 is wrapped around the electrode body 20, and the facing surfaces of the exterior film 50 (thermally adhesive resin layers 53) are heat-sealed to form the first sealing portion 70.

The first sealing portion 70 is formed by heat-sealing the heat-fusible resin layers of the exterior film 50 together. The first sealing portion 70 extends in the longitudinal direction of the exterior body 40. The position at which the first sealing portion 70 is formed on the exterior body 40 can be selected arbitrarily. As shown in FIG. 1, the base of the first sealing portion 70 is preferably located on the boundary between the main surface and the side surface of the exterior body 40. The base of the first sealing portion 70 may also be located on any surface of the exterior body 40. In FIG. 1, the first sealing portion 70 protrudes outward beyond the electrode body 20 in a plan view. The first sealing portion 70 may be folded, for example, toward the side surface of the exterior body 40 or toward the main surface.

The second sealing portion 80 is formed by joining the heat-sealable resin layer 53 of the exterior film 50 and the lid joint portion of the lid 60 (the portion where the heat-sealable resin layer 53 of the exterior film 50 and the lid 60 come into contact) by, for example, heat sealing. The exterior film 50 and the lid 60 can also be joined by any method, such as welding.

<1-2. Physical properties of electricity storage devices>
In the energy storage device of the present disclosure, the barrier layer 52 of the exterior film 50 is characterized in that, at the position where the heat-sealable resin layer 53 of the exterior film 50 is heat-sealed to the lid body 60, the direction is perpendicular to the rolling direction of the barrier layer 52, and the cross section obtained by cutting the barrier layer 52 in a direction perpendicular to the surface of the barrier layer 52 (i.e., a direction perpendicular to the surface of the barrier layer) is subjected to crystal analysis by the EBSD method, and the area average angle difference of the GOS (grain orientation dispersion) when the grain boundary is defined as 5° is 2.50° or less.

From the perspective of more optimally demonstrating the effects of the presently disclosed invention, the area-average angular difference of the GOS (crystal grain orientation dispersion) is preferably approximately 2.50° or less, more preferably approximately 2.00° or less, and even more preferably approximately 1.50° or less. It may also be, for example, approximately 0° or more, approximately 0.20° or more, and preferred ranges include approximately 0 to 2.50°, approximately 0 to 2.00°, approximately 0 to 1.50°, approximately 0.20 to 2.50°, approximately 0.20 to 2.00°, and approximately 0.20 to 1.50°.

The area-average angular difference of the GOS (grain orientation dispersion) of the barrier layer 52 is a value measured by the following method.

<Measurement of area average angle difference of GOS (grain orientation dispersion) of barrier layer>
For an electricity storage device, the barrier layer at the position where the heat-sealable resin layer of the exterior film is heat-sealed to the lid (sealing portion (second sealing portion)) is obtained, and crystal analysis is performed using the EBSD method to measure the area-average angle difference of GOS (crystal grain orientation dispersion) when the grain boundary of the barrier layer is defined as 5°. The specific measurement method is as follows.

Crystal analysis was performed by EBSD on a cross section of each barrier layer perpendicular to the rolling direction, and the area-average angular difference of GOS (grain orientation dispersion) was measured when the grain boundary of the barrier layer was defined as ⁵ °. The detailed measurement conditions are as follows: The area-average angular difference of GOS (grain orientation dispersion) is the area-average angular difference of GOS (grain orientation dispersion) of crystals contained in a measurement area of approximately 5,000 μm2 or more (the entire barrier layer in the thickness direction is the measurement area) obtained by connecting multiple images acquired by crystal analysis by EBSD.

(Measuring device)
A Schottky field emission scanning electron microscope equipped with an EBSD detector is used.

(Pretreatment)
As a pretreatment, the barrier layer is cut in a direction perpendicular to the rolling direction (RD) to obtain a cross section. The rolling direction of the barrier layer is the direction in which linear rolling marks extend when the shiny surface of the barrier layer is observed with a metallurgical microscope. Specifically, the barrier layer to be used as a sample is first cut into a 5 mm (perpendicular to the rolling direction) x 10 mm (rolling direction) piece using a trimming razor, and then embedded in resin. Next, the barrier layer and the resin are cut using the trimming razor in a direction perpendicular to the rolling direction of the barrier layer, perpendicular to the surface of the barrier layer, to expose the cross section of the barrier layer. Next, the obtained cross section is trimmed using a microtome. In this trimming, to reduce mechanical distortion of the cross section shape, the microtome is used to cut the embedded resin and the barrier layer in a direction perpendicular to the cross section by approximately 1 mm. Next, a measurement cross section is prepared by irradiating the cross section with a broad argon beam in a direction perpendicular to the cross section under conditions of a protrusion width of 50 μm, a voltage of 6 kV, and 4 hours. This is a process for precisely exposing the cross section of the barrier layer so as to minimize mechanical damage to the crystal structure that occurred in the previous process. In the present disclosure, the "perpendicular direction" when cutting the aluminum alloy foil is confirmed under a stereomicroscope, and therefore may include an error of about 10°. That is, the permissible range for the direction perpendicular to the rolling direction is 80 to 100° to the rolling direction, and the permissible range for the direction perpendicular to the surface is 80 to 100° with respect to the surface.

(SEM conditions)
The conditions of the scanning electron microscope (SEM) used in the EBSD method are as follows.
Observation magnification: 2000 times (the standard observation magnification when photographing is Polaroid 545)
Acceleration voltage: 15 kV
Working distance: 15mm
Sample tilt angle: 70°

(EBSD conditions)
The conditions for the crystal analysis by the EBSD method are as follows.
Step size: 150 nm
Analysis conditions:
The following analysis is carried out using crystal orientation analysis software OIM (Ver. 7.3) manufactured by TSL Solutions Co., Ltd.
Multiple images are joined together, and the measurement area is approximately 5,000 μm ^or more. The upper limit of the measurement area is, for example, approximately 30,000 μm ^or less. In this case, the measurement area is from the center of the barrier layer in the thickness direction to both ends, and areas where resin is attached to the cross section or where an acid-resistant coating is present are excluded from the measurement area.
The CI value is 0.1 or more, the grain boundary condition is 5° or more, and the minimum grain size is 3 steps or more.
After stitching the images, check the pole figures.
If the center of the pole figure is shifted by 10° or more, rotate the crystal data to ensure symmetry. The pole figure used as a reference is measured from the sample surface using XRD. When obtaining a pole figure from the surface using EBSD, the sample surface is mechanically polished, flat-milled, electrolytically polished, etc., before a wide-area measurement is performed to remove the influence of the mechanical crystal structure of the sample surface. The pole figure obtained from the surface direction is then rotated 90° so that it is the same as the pole figure obtained from the same orientation as the pole figure obtained from the cross section of the target sample. This pole figure is used as a reference.
The analysis is performed by excluding data with a CI value of 0.1 or less, which is defined by the crystal orientation analysis software OIM (Ver. 7.3) manufactured by TSL Solutions Co., Ltd. This makes it possible to exclude data based on the resin used in pretreatment present on the front and back of the sample, grain boundaries present on the cross section, and amorphous matter.

The area-average angular difference of the GOS (crystal grain orientation dispersion) of the barrier layer 52 can be adjusted by the material constituting the barrier layer 52, the thickness of the barrier layer 52, the material of the lid 60, and the sealing conditions (temperature, pressure, time) when the exterior film 50 and the lid 60 are heat-sealed to form the second sealing portion 80.

For example, by increasing the Young's modulus of the barrier layer 52 (i.e., by increasing the Young's modulus of the exterior film 50), the area-average angular difference of the GOS (crystal grain orientation dispersion) of the barrier layer 52 can be reduced. The preferred Young's modulus of the barrier layer 52 will be described later. For example, increasing the thickness of the barrier layer 52 or using a high-strength metal is effective.

For example, if the barrier layer 52 is made of aluminum alloy foil, and the aluminum alloy composition is in the 8000 series of the JIS standard, the strength can be increased by adding a small amount of Si to the aluminum base metal. Furthermore, if the aluminum alloy composition is in the 5000 series of the JIS standard, the strength of the soft foil can be increased by solid solution strengthening by dissolving Mg in the aluminum.

Refining the crystal grains of the metal forming the barrier layer 52 is also effective in increasing the ratio (R1/R2). For example, in the case of aluminum alloy compositions in the JIS 8000 and 5000 series, Al-Fe intermetallic compounds crystallize during casting, which then act as nuclei for grain refinement. Furthermore, when differential speed rolling (a method of rolling using rolls with different peripheral speeds) is employed, the rolled material undergoes shear deformation throughout the entire thickness in addition to the normal rolling deformation. This promotes crystal rotation and promotes the transformation of subgrain boundaries into high-angle grain boundaries, resulting in the formation of fine crystal grains. While this method is also effective in cold rolling, it is more effective with warm rolling. Furthermore, increasing the number of rolling passes in the hot rolling of aluminum alloy foil and increasing the final cold rolling reduction are also effective. The higher the final cold rolling reduction from the intermediate annealing to the final thickness (e.g., 80% or higher), the greater the amount of strain accumulated in the aluminum alloy foil, resulting in finer recrystallized grains after final annealing.

The rolling conditions for aluminum foil are adjusted by adjusting the rolling reduction, heating temperature, heating time, and other conditions. Examples of methods include a homogenization process for aluminum metal or aluminum alloy ingots at approximately 500-600°C for approximately 1-2 hours, a hot rolling process, a cold rolling process, an intermediate annealing process in which the ingot is held at approximately 300-450°C for approximately 1-10 hours, a cold rolling process in which the rolling reduction from the intermediate annealing to the final rolling is 80% or more, preferably 90% or more, and a final annealing process in which the ingot is held at approximately 250-400°C for approximately 30-100 hours, but the conditions for refining the crystal grains are not limited to these.

Furthermore, it is also effective to make the linear expansion coefficient of the barrier layer 52 closer to the linear expansion coefficient of the material used in the lid body 60 (lid body 61 or covering body 62).

<1-3. Manufacturing method of electricity storage device>
The electricity storage device of the present disclosure can be manufactured by assembling the electrode body 20, electrode terminal 30, exterior film 50, and lid body 60 of the present disclosure. These can be assembled using, for example, a known method. Specific examples of the electricity storage device of the present disclosure are shown below.

A pair of lid bodies 60 to which electrode terminals 30 are joined are placed on the electrode body 20, electrically connecting the electrode terminals 30 and the electrode body 20. The lid bodies 60 may also be joined to the electrode terminals 30 that are electrically connected to the electrode body 20.

Next, the electrode body 20 and the lid body 60 are wrapped in an exterior film 50. The exterior film 50 is wrapped around the electrode body 20 and the lid body 60 while tension is applied to the exterior film 50, while the movement of the electrode body 20 and the lid body 60 is restricted by a restricting means. The restricting means is, for example, a groove into which the electrode body 20 and the lid body 60 are fitted. The restricting means may be a device that applies an external force to the electrode body 20 and the lid body 60 to prevent them from moving. The restricting means may be a device that applies a force to the electrode body 20 and the lid body 60 in the direction opposite to the direction in which the exterior film 50 is pulled. The restricting means may include a roller that runs over the exterior film 50 while the exterior film 50 is being pulled, in order to remove wrinkles in the exterior film 50.

Next, the electrode body 20 is sealed with the exterior body 40. Specifically, the process involves heat-sealing the heat-sealable resin layers 53 of the exterior film 50 facing each other to form a first sealed portion 70, and heat-sealing the heat-sealable resin layers 53 of the exterior film 50 to the side of the lid body 60 to form a second sealed portion 80. The order of these processes is not particularly limited, but for example, the second sealed portion 80 is formed before the first sealed portion 70 is formed. The first sealed portion 70 and second sealed portion 80 can be formed by heat-sealing the heat-sealable resin layers 53 using a heat seal bar or the like.

<2-1. Laminated structure and physical properties of exterior film>
As shown in Fig. 4, for example, an exterior film (exterior material for an electricity storage device) 50 according to the present disclosure is composed of a laminate including a barrier layer 52 and a heat-sealable resin layer 53. In the exterior film 50, the barrier layer 52 is the outermost layer, and the heat-sealable resin layer 53 is the innermost layer. When assembling an electricity storage device using the exterior film 50 and electricity storage device elements (electrode body 20, electrode terminal 30, etc.), the electrode body 20 is housed in a space formed by heat-sealing the ends of the exterior film 50 together with a lid 60 while the heat-sealable resin layers 53 of the exterior film 50 face each other. In the laminate constituting the exterior film 50 according to the present disclosure, the side of the heat-sealable resin layer 53 relative to the barrier layer 52 is the inner side, and the opposite side is the outer side.

As shown in FIG. 4, for example, the exterior film 50 may optionally have a substrate layer 51 on the outside of the barrier layer 52. Also, as shown in FIG. 4, for example, the exterior film 50 may optionally have an adhesive layer 54 between the substrate layer 51 and the barrier layer 52 for purposes such as increasing the adhesion between these layers. Also, as shown in FIG. 4, for example, the exterior film 50 may optionally have an adhesive layer 55 between the barrier layer 52 and the heat-sealable resin layer 53 for purposes such as increasing the adhesion between these layers. Also, as shown in FIG. 4, for example, a surface coating layer (not shown) or the like may be provided on the outside of the substrate layer 51 (the side opposite the heat-sealable resin layer 53) as needed.

The thickness of the laminate constituting the exterior film 50 is not particularly limited, but from the viewpoints of cost reduction, improved energy density, etc., examples include approximately 250 μm or less, and preferably approximately 190 μm or less, approximately 180 μm or less, approximately 155 μm or less, and approximately 120 μm or less. Furthermore, from the viewpoint of maintaining the exterior film's function of protecting the electrode assembly 20, the thickness of the laminate constituting the exterior film 50 is preferably approximately 35 μm or more, approximately 45 μm or more, or approximately 60 μm or more. Furthermore, preferred ranges for the laminate constituting the exterior film 50 include, for example, approximately 35 to 250 μm, approximately 35 to 190 μm, approximately 35 to 180 μm, approximately 35 to 155 μm, approximately 35 to 120 μm, approximately 45 to 250 μm, approximately 45 to 190 μm, approximately 45 to 180 μm, approximately 45 to 155 μm, approximately 45 to 120 μm, approximately 60 to 250 μm, approximately 60 to 190 μm, approximately 60 to 180 μm, approximately 60 to 155 μm, and approximately 60 to 120 μm. In particular, approximately 60 to 155 μm is preferred when making the electricity storage device lighter and thinner, and approximately 155 to 190 μm is preferred when improving the conformability of the exterior film when wrapped around the electrode body.

In the exterior film 50, the ratio of the total thickness of the optional base layer 51, optional adhesive layer 54, barrier layer 52, optional adhesive layer 55, heat-sealable resin layer 53, and optional surface coating layer to the thickness (total thickness) of the laminate constituting the exterior film 50 is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. As a specific example, when the exterior film 50 of the present disclosure includes the base layer 51, adhesive layer 54, barrier layer 52, adhesive layer 55, and heat-sealable resin layer 53, the ratio of the total thickness of these layers to the thickness (total thickness) of the laminate constituting the exterior film 50 is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. Furthermore, even when the exterior film 50 of the present disclosure is a laminate including a substrate layer 51, an adhesive layer 54, a barrier layer 52, and a heat-sealable resin layer 53, the ratio of the total thickness of these layers to the thickness (total thickness) of the laminate constituting the exterior film 50 can be, for example, 80% or more, preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more.

From the perspective of more optimally achieving the effects of the present invention, the Young's modulus of the exterior film 50 is preferably 6,000 MPa or more, more preferably 8,000 MPa or more, and even more preferably 10,000 MPa or more, and is preferably 40,000 MPa or less, more preferably 35,000 MPa or less, and even more preferably 30,000 MPa or less. Preferred ranges include approximately 6,000 to 40,000 MPa, approximately 6,000 to 35,000 MPa, approximately 6,000 to 30,000 MPa, approximately 8,000 to 40,000 MPa, approximately 8,000 to 35,000 MPa, approximately 8,000 to 30,000 MPa, approximately 10,000 to 40,000 MPa, approximately 10,000 to 35,000 MPa, and approximately 10,000 to 30,000 MPa. In the present disclosure, the Young's modulus of the exterior film is a value measured by the following method.

<Measurement of Young's modulus of exterior film>
In accordance with the provisions of JIS K6251:2017, an S-S curve in the TD direction of the exterior film was obtained under the following measurement conditions, and the Young's modulus (MPa) was calculated from the maximum value of the slope of the S-S curve.
(Measurement conditions)
A tensile testing machine is used.
Shape of test piece: Dumbbell No. 7 Width of test piece: 2 mm
Test piece length: 35 mm
Thickness of test piece: measured with a thickness gauge. Gauge distance: 20 mm
Tensile speed: 50 mm/min
Test environment: 23±5°C, 50±30% RH
Number of measurements: Average value of 3 measurements

One effective method for increasing the Young's modulus of the exterior film 50 is to increase the Young's modulus of the barrier layer 52 as described above.

<2-2. Layers that make up the exterior film>
[Base material layer 51]
In the present disclosure, the substrate layer 51 is a layer that is provided as needed for the purpose of functioning as a substrate for the exterior film, etc. The substrate layer 51 is located on the outer layer side of the exterior film.

There are no particular restrictions on the material from which the substrate layer 51 is made, as long as it functions as a substrate, i.e., is at least insulating. The substrate layer 51 can be made using, for example, a resin, which may contain additives as described below.

When the substrate layer 51 is formed from a resin, the substrate layer 51 can be formed from, for example, a resin film. When the substrate layer 51 is formed from a resin film, a preformed resin film may be used as the substrate layer 51 when laminating the substrate layer 51 with the barrier layer 52 or the like to produce the exterior film 50 of the present disclosure. Alternatively, the resin forming the substrate layer 51 may be formed into a film on the surface of the barrier layer 52 or the like by extrusion molding, coating, or the like to form the substrate layer 51 formed from a resin film. The resin film may be an unstretched film or a stretched film. Stretched films include uniaxially stretched films and biaxially stretched films, with biaxially stretched films being preferred. Stretching methods for forming biaxially stretched films include, for example, sequential biaxial stretching, inflation, and simultaneous biaxial stretching. Resin coating methods include roll coating, gravure coating, and extrusion coating.

Examples of resins that can form the base layer 51 include polyester, polyamide, polyolefin, epoxy resin, acrylic resin, fluororesin, polyurethane, silicone resin, and phenolic resin, as well as modified versions of these resins. The resin that forms the base layer 51 can also be a copolymer of these resins, or a modified version of the copolymer. It can also be a mixture of these resins.

The base layer 51 preferably contains these resins as its main component, and more preferably contains polyester or polyamide as its main component. Here, "main component" means that the resin component contained in the base layer 51 contains, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more. For example, "the base layer 51 contains polyester or polyamide as its main component" means that the resin component contained in the base layer 51 contains, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more.

Of these, polyester and polyamide are preferred as resins for forming the base layer 51.

Specific examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymer polyesters. Copolymer polyesters include those in which ethylene terephthalate is the main repeating unit. Specific examples include copolymer polyesters in which ethylene terephthalate is the main repeating unit polymerized with ethylene isophthalate (hereinafter abbreviated as polyethylene (terephthalate/isophthalate)), polyethylene (terephthalate/adipate), polyethylene (terephthalate/sodium sulfoisophthalate), polyethylene (terephthalate/sodium isophthalate), polyethylene (terephthalate/phenyl-dicarboxylate), and polyethylene (terephthalate/decanedicarboxylate). These polyesters may be used alone or in combination of two or more.

Specific examples of polyamides include aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, and copolymers of nylon 6 and nylon 66; hexamethylenediamine-isophthalic acid-terephthalic acid copolymer polyamides such as nylon 6I, nylon 6T, nylon 6IT, and nylon 6I6T (where I represents isophthalic acid and T represents terephthalic acid), which contain structural units derived from terephthalic acid and/or isophthalic acid; aromatic polyamides such as polyamide MXD6 (polymetaxylylene adipamide); alicyclic polyamides such as polyamide PACM6 (polybis(4-aminocyclohexyl)methane adipamide); polyamides copolymerized with lactam components or isocyanate components such as 4,4'-diphenylmethane diisocyanate; polyesteramide copolymers and polyetheresteramide copolymers, which are copolymers of copolymerized polyamides with polyesters or polyalkylene ether glycols; and other polyamide copolymers. These polyamides may be used alone or in combination of two or more.

The base layer 51 preferably includes at least one of a polyester film, a polyamide film, and a polyolefin film, preferably at least one of a stretched polyester film, a stretched polyamide film, and a stretched polyolefin film, more preferably at least one of a stretched polyethylene terephthalate film, a stretched polybutylene terephthalate film, a stretched nylon film, and a stretched polypropylene film, and even more preferably at least one of a biaxially oriented polyethylene terephthalate film, a biaxially oriented polybutylene terephthalate film, a biaxially oriented nylon film, and a biaxially oriented polypropylene film.

The substrate layer 51 may be a single layer, or may be composed of two or more layers. When the substrate layer 51 is composed of two or more layers, the substrate layer 51 may be a laminate in which resin films are laminated with an adhesive or the like, or a laminate of resin films formed by co-extrusion of resin into two or more layers. Furthermore, a laminate of resin films formed by co-extrusion of resin into two or more layers may be used as the substrate layer 51 without being stretched, or may be uniaxially or biaxially stretched to form the substrate layer 51.

Specific examples of laminates of two or more resin films in the substrate layer 51 include a laminate of polyester film and nylon film, a laminate of two or more nylon film layers, and a laminate of two or more polyester film layers. Preferred are a laminate of stretched nylon film and stretched polyester film, a laminate of two or more stretched nylon film layers, and a laminate of two or more stretched polyester film layers. For example, when the substrate layer 51 is a laminate of two resin films, a laminate of polyester resin film and polyester resin film, a laminate of polyamide resin film and polyamide resin film, or a laminate of polyester resin film and polyamide resin film is preferred. A laminate of polyethylene terephthalate film and polyethylene terephthalate film, a laminate of nylon film and nylon film, or a laminate of polyethylene terephthalate film and nylon film is more preferred. Furthermore, because polyester resins are less likely to discolor when electrolyte solution adheres to their surfaces, it is preferable that the polyester resin film be the outermost layer of the substrate layer 51 when the substrate layer 51 is a laminate of two or more resin films. In the laminate of polyester resin film and polyamide resin film, preferred ranges of the thickness of the polyester resin film are about 2 to 33 μm, about 2 to 28 μm, about 2 to 23 μm, about 2 to 18 μm, about 2 to 11 μm, about 2 to 8 μm, about 10 to 33 μm, about 10 to 28 μm, about 10 to 23 μm, about 10 to 18 μm, about 10 to 11 μm, about 18 to 33 μm, and 18 to 28 μm. and approximately 18 to 23 μm. Preferred thickness ranges for polyamide resin films include approximately 2 to 33 μm, approximately 2 to 28 μm, approximately 2 to 23 μm, approximately 2 to 18 μm, approximately 2 to 11 μm, approximately 2 to 8 μm, approximately 10 to 33 μm, approximately 10 to 28 μm, approximately 10 to 23 μm, approximately 10 to 18 μm, approximately 10 to 11 μm, approximately 18 to 33 μm, approximately 18 to 28 μm, and approximately 18 to 23 μm.

When the base layer 51 is a laminate of two or more resin film layers, the two or more resin film layers may be laminated via an adhesive. Examples of preferred adhesives include those similar to those exemplified for the adhesive layer 54 described below. The method for laminating two or more resin film layers is not particularly limited, and known methods can be used, such as dry lamination, sandwich lamination, extrusion lamination, and thermal lamination, with dry lamination being preferred. When laminating using the dry lamination method, a polyurethane adhesive is preferably used as the adhesive. In this case, the adhesive thickness can be, for example, approximately 2 to 5 μm. Alternatively, an anchor coat layer can be formed on the resin film before lamination. Examples of the anchor coat layer include those similar to those exemplified for the adhesive layer 54 described below. In this case, the anchor coat layer thickness can be, for example, approximately 0.01 to 1.0 μm.

Additives such as lubricants, flame retardants, antiblocking agents, antioxidants, light stabilizers, tackifiers, and antistatic agents may also be present on at least one of the surface and interior of the base layer 51. A single type of additive may be used, or two or more types may be mixed together.

In the present disclosure, from the perspective of improving the conformability of the exterior film, it is preferable that a lubricant be present on at least one of the surface and interior of the base layer 51. The lubricant is not particularly limited, but preferably an amide-based lubricant is used. Specific examples of amide-based lubricants include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides. Specific examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Specific examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Specific examples of substituted amides include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, and N-stearyl erucic acid amide. Specific examples of methylolamides include methylol stearic acid amide. Specific examples of saturated fatty acid bisamides include methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene hydroxystearic acid amide, N,N'-distearyl adipamide, N,N'-distearyl sebacic acid amide, etc. Specific examples of unsaturated fatty acid bisamides include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipamide, N,N'-dioleyl sebacic acid amide, etc. Specific examples of fatty acid ester amides include stearamidoethyl stearate, etc. Specific examples of aromatic bisamides include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, and N,N'-distearyl isophthalic acid amide. The lubricant may be used alone or in combination of two or more types, with a combination of two or more types being preferred.

When a lubricant is present on the surface of the base layer 51, the amount thereof is not particularly limited, and may be, for example, about 3 mg/ ^m2 or more, preferably about 4 mg/ ^m2 or more, or about 5 mg/ ^m2 or more. The amount of lubricant present on the surface of the base layer 51 may be, for example, about 15 mg/ ^m2 or less, preferably about 14 mg/ ^m2 or less, or about 10 mg/ ^m2 or less. Preferred ranges for the amount of lubricant present on the surface of the base layer 51 include ^about 3 to 15 mg/m2, about ³ to 14 mg/m2, ^about 3 to 10 mg/m2, ^about 4 to 15 mg/m2, ^about 4 to 14 mg/m2, ^about 4 to 10 mg/m2, about 5 to 15 mg/ ^m2 , about 5 to ¹⁴ mg/m2, and about 5 to 10 mg/ ^m2 .

The lubricant present on the surface of the base layer 51 may be a lubricant exuded from the resin that makes up the base layer 51, or a lubricant applied to the surface of the base layer 51.

The thickness of the substrate layer 51 is not particularly limited as long as it functions as a substrate, but examples include approximately 3 μm or more, preferably approximately 10 μm or more. Furthermore, the thickness of the substrate layer 51 is, for example, approximately 50 μm or less, preferably approximately 35 μm or less, approximately 11 μm or less, or approximately 8 μm or less. Preferred thickness ranges for the substrate layer 51 include approximately 3 to 50 μm, approximately 3 to 35 μm, approximately 3 to 11 μm, approximately 3 to 8 μm, approximately 10 to 50 μm, and approximately 10 to 35 μm. In particular, for reducing the weight and thickness of the energy storage device, approximately 3 to 35 μm, approximately 3 to 11 μm, or approximately 3 to 8 μm is preferred, and for improving conformability, approximately 35 to 50 μm is preferred. When the substrate layer 51 is a laminate of two or more resin film layers, the thickness of each of the resin films constituting each layer is not particularly limited, but examples include approximately 2 μm or more, preferably approximately 10 μm or more, or approximately 18 μm or more. The thickness of the resin film constituting each layer is, for example, about 33 μm or less, preferably about 28 μm or less, about 23 μm or less, about 18 μm or less, about 11 μm or less, or about 8 μm or less. Preferred thickness ranges for the resin film constituting each layer include about 2 to 33 μm, about 2 to 28 μm, about 2 to 23 μm, about 2 to 18 μm, about 2 to 11 μm, about 2 to 8 μm, about 10 to 33 μm, about 10 to 28 μm, about 10 to 23 μm, about 10 to 18 μm, about 10 to 11 μm, about 18 to 33 μm, about 18 to 28 μm, and about 18 to 23 μm.

[Adhesive layer 54]
In the exterior film of the present disclosure, the adhesive layer 54 is a layer that is provided between the base material layer 51 and the barrier layer 52 as needed for the purpose of increasing the adhesion between them.

The adhesive layer 54 is formed from an adhesive capable of bonding the base layer 51 and the barrier layer 52. There are no limitations on the adhesive used to form the adhesive layer 54, and it may be any of a chemical reaction type, a solvent evaporation type, a hot melt type, a thermocompression type, etc. It may also be a two-component curing adhesive (two-component adhesive), a one-component curing adhesive (one-component adhesive), or a resin that does not involve a curing reaction. The adhesive layer 54 may be a single layer or multiple layers.

Specific examples of adhesive components include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymer polyesters; polyethers; polyurethanes; epoxy resins; phenolic resins; polyamides such as nylon 6, nylon 66, nylon 12, and copolymer polyamides; polyolefin resins such as polyolefins, cyclic polyolefins, acid-modified polyolefins, and acid-modified cyclic polyolefins; polyvinyl acetate; cellulose; (meth)acrylic resins; polyimides; polycarbonates; amino resins such as urea resins and melamine resins; rubbers such as chloroprene rubber, nitrile rubber, and styrene-butadiene rubber; and silicone resins. These adhesive components may be used alone or in combination. Among these adhesive components, polyurethane adhesives are preferred. Furthermore, the adhesive strength of these adhesive resins can be increased by using an appropriate curing agent. The curing agent is selected from polyisocyanates, multifunctional epoxy resins, oxazoline group-containing polymers, polyamine resins, acid anhydrides, and other materials depending on the functional groups of the adhesive components.

Examples of polyurethane adhesives include polyurethane adhesives containing a first part containing a polyol compound and a second part containing an isocyanate compound. Two-component curing polyurethane adhesives are preferred, with a polyol such as polyester polyol, polyether polyol, or acrylic polyol as the first part and an aromatic or aliphatic polyisocyanate as the second part. Examples of polyurethane adhesives include polyurethane adhesives containing a polyurethane compound obtained by reacting a polyol compound with an isocyanate compound in advance, and an isocyanate compound. Examples of polyurethane adhesives include polyurethane adhesives containing a polyurethane compound obtained by reacting a polyol compound with an isocyanate compound in advance, and a polyol compound. Examples of polyurethane adhesives include polyurethane adhesives obtained by reacting a polyurethane compound obtained by reacting a polyol compound with an isocyanate compound in advance with moisture, such as in the air, and curing the polyurethane compound. It is preferable to use a polyester polyol, which has hydroxyl groups on the side chains in addition to the terminal hydroxyl groups of the repeating unit. Examples of the second agent include aliphatic, alicyclic, aromatic, and araliphatic isocyanate compounds. Examples of isocyanate compounds include hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), hydrogenated XDI (H6XDI), hydrogenated MDI (H12MDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and naphthalene diisocyanate (NDI). Examples of polyfunctional isocyanate-modified compounds made from one or more of these diisocyanates include polyisocyanates. Multimers (e.g., trimers) can also be used as polyisocyanate compounds. Examples of such multimers include adducts, biurets, and nurates. The adhesive layer 54 is made of polyurethane adhesive, which gives the exterior film excellent electrolyte resistance and prevents the base layer 51 from peeling off even if electrolyte adheres to the side surface.

In addition, other components may be added to the adhesive layer 54 as long as they do not impair adhesion, and may contain colorants, thermoplastic elastomers, tackifiers, fillers, etc. By including a colorant in the adhesive layer 54, the exterior film can be colored. Known colorants such as pigments and dyes can be used. Furthermore, only one type of colorant may be used, or two or more types may be mixed together.

There are no particular restrictions on the type of pigment, so long as it does not impair the adhesive properties of the adhesive layer 54. Examples of organic pigments include azo-based, phthalocyanine-based, quinacridone-based, anthraquinone-based, dioxazine-based, indigothioindigo-based, perinone-perylene-based, isoindolenine-based, and benzimidazolone-based pigments. Examples of inorganic pigments include carbon black-based, titanium oxide-based, cadmium-based, lead-based, chromium oxide-based, and iron-based pigments. Other examples include finely powdered mica and fish scale foil.

Among colorants, carbon black is preferred, for example, to give the exterior film a black appearance. Furthermore, mica is preferred from the perspective of dissipating heat generated by the electricity storage device.

The average particle size of the pigment is not particularly limited, but may be, for example, approximately 0.05 to 5 μm, and preferably approximately 0.08 to 2 μm. The average particle size of the pigment is the median diameter measured using a laser diffraction/scattering particle size distribution analyzer.

The pigment content in the adhesive layer 54 is not particularly limited as long as it colors the exterior film, but can be, for example, approximately 5 to 60% by weight, and preferably 10 to 40% by weight.

The thickness of the adhesive layer 54 is not particularly limited as long as it can bond the base layer 51 and the barrier layer 52, but is, for example, approximately 1 μm or more, approximately 2 μm or more. The thickness of the adhesive layer 54 is, for example, approximately 10 μm or less, approximately 5 μm or less. Preferred ranges for the thickness of the adhesive layer 54 include approximately 1 to 10 μm, approximately 1 to 5 μm, approximately 2 to 10 μm, and approximately 2 to 5 μm.

[Colored layer]
The colored layer (not shown) is a layer that is provided as needed between the base material layer 51 and the barrier layer 52. When the adhesive layer 54 is provided, a colored layer may be provided between the base material layer 51 and the adhesive layer 54, or between the adhesive layer 54 and the barrier layer 52. Alternatively, a colored layer may be provided on the outer side of the base material layer 51. By providing a colored layer, the exterior film can be colored.

The colored layer can be formed, for example, by applying ink containing a colorant to the surface of the base layer 51 or the surface of the barrier layer 52. Known colorants such as pigments and dyes can be used as colorants. Furthermore, a single type of colorant may be used, or two or more types may be mixed together.

Specific examples of colorants contained in the colored layer include the same as those exemplified in the [Adhesive layer 54] section.

[Barrier layer 52]
In the exterior film, the barrier layer 52 is a layer that at least prevents the penetration of moisture.

Examples of the barrier layer 52 include metal foils, vapor-deposited films, and resin layers with barrier properties. Vapor-deposited films include metal vapor-deposited films, inorganic oxide vapor-deposited films, and carbon-containing inorganic oxide vapor-deposited films. Resin layers include fluorine-containing resins such as polyvinylidene chloride, polymers based on chlorotrifluoroethylene (CTFE), polymers based on tetrafluoroethylene (TFE), polymers containing fluoroalkyl groups, and polymers based on fluoroalkyl units, as well as ethylene-vinyl alcohol copolymers. The barrier layer 52 also includes resin films comprising at least one of these vapor-deposited films and resin layers. The barrier layer 52 may be formed of multiple layers. It is preferable that the barrier layer 52 include a layer composed of a metal material. Specific examples of metal materials that can be used to form the barrier layer 52 include aluminum, aluminum alloys, titanium, titanium alloys, steel (including stainless steel), copper, copper alloys, nickel, nickel alloys, magnesium, magnesium alloys, niobium, and iron. Of these, aluminum alloys, stainless steel, titanium steel, and steel plate are preferred. When used as a metal foil, it is preferable to use at least one of aluminum alloy foil and stainless steel foil.

In the barrier layer 52, layers made of the aforementioned metallic materials may contain recycled metallic materials. Examples of recycled metallic materials include recycled aluminum alloys, stainless steel, titanium steel, and steel plate. These recycled materials can be obtained by known methods. Recycled aluminum alloys can be obtained, for example, by the manufacturing method described in WO 2022/092231. The barrier layer 52 may be made entirely of recycled materials, or may be made of a mixture of recycled and virgin materials. Note that recycled metallic materials refer to metallic materials that have been made reusable by collecting, isolating, and refining various products used in the market or waste from manufacturing processes. Furthermore, virgin metallic materials refer to new metallic materials refined from natural metallic resources (raw materials) and are not recycled materials.

From the viewpoint of improving the conformability when wrapping the exterior film around the electrode body, the aluminum alloy foil is preferably a soft aluminum alloy foil made of, for example, an annealed aluminum alloy, and from the viewpoint of further improving the conformability, it is preferable that the aluminum alloy foil be an iron-containing aluminum alloy foil. In the iron-containing aluminum alloy foil (100% by mass), the iron content is preferably 0.1 to 9.0% by mass, and more preferably 0.5 to 2.0% by mass. By having an iron content of 0.1% by mass or more, an exterior film with better conformability can be obtained. By having an iron content of 9.0% by mass or less, an exterior film with better flexibility can be obtained. Examples of soft aluminum alloy foils include aluminum alloy foils having compositions specified in JIS H4160:1994 A8021H-O, JIS H4160:1994 A8079H-O, JIS H4000:2014 A8021P-O, or JIS H4000:2014 A8079P-O. Silicon, magnesium, copper, manganese, etc. may also be added as needed. Softening can be achieved by annealing or other methods.

From the perspective of improving the mechanical strength of the exterior film 50, it is more preferable that the aluminum alloy foil be a hard aluminum alloy foil composed of, for example, a work-hardened aluminum alloy. Examples of hard aluminum alloy foils include aluminum alloy foils having the compositions specified in JIS H4160:1994 A8021H-H18, JIS H4160:1994 A8079H-H18, JIS H4000:2014 A8021P-H14, or JIS H4000:2014 A8079P-H14. From the perspective of improving the mechanical strength of the exterior film 50, it is preferable that the aluminum alloy foil be an aluminum alloy foil containing magnesium. In the aluminum alloy foil containing magnesium (100% by mass), the magnesium content is preferably 0.2 to 5.6% by mass, and more preferably 0.2 to 3.0% by mass. Examples of aluminum alloy foils containing magnesium include aluminum alloy foils having compositions defined in JIS H4000:2017 A5005P-O, JIS H4000:2017 A5050P-O, and JIS H4000:2017 A5052P-O. Furthermore, from the viewpoint of improving the mechanical strength of the exterior film 50, the aluminum alloy foil is preferably an aluminum alloy foil containing manganese. In the aluminum alloy foil containing manganese (100% by mass), the manganese content is preferably 0.3 to 1.5% by mass, and more preferably 1.0 to 1.5% by mass. Examples of aluminum alloy foils containing manganese include aluminum alloy foils having compositions specified in JIS H4000:2017 A3003P-O, JIS H4000:2017 A3103P-O, JIS H4000:2017 A3004P-O, and JIS H4000:2017 A3104P-O.

Furthermore, examples of stainless steel foil include austenitic, ferritic, austenitic-ferritic, martensitic, and precipitation-hardened stainless steel foils. Furthermore, from the perspective of providing an exterior film with excellent conformability, it is preferable that the stainless steel foil be made of austenitic stainless steel.

Specific examples of austenitic stainless steels that make up the stainless steel foil include SUS304, SUS301, and SUS316L, with SUS304 being particularly preferred.

In the case of metal foil, the thickness of the barrier layer 52 should be sufficient to at least function as a barrier layer that prevents moisture penetration, and can be, for example, approximately 9 to 200 μm. The thickness of the barrier layer 52 is preferably approximately 200 μm or less, more preferably approximately 150 μm or less, even more preferably approximately 120 μm or less, even more preferably approximately 100 μm or less, and particularly preferably approximately 90 μm or less. The thickness of the barrier layer 52 is preferably approximately 10 μm or more, even more preferably approximately 20 μm or more, and more preferably approximately 25 μm or more. Furthermore, preferred ranges for the thickness of the barrier layer 52 include approximately 9 to 200 μm, approximately 9 to 150 μm, approximately 9 to 120 μm, approximately 9 to 100 μm, approximately 9 to 90 μm, approximately 10 to 200 μm, approximately 10 to 150 μm, approximately 10 to 120 μm, approximately 10 to 100 μm, approximately 10 to 90 μm, approximately 20 to 200 μm, approximately 20 to 150 μm, approximately 20 to 120 μm, approximately 20 to 100 μm, approximately 20 to 90 μm, approximately 25 to 200 μm, approximately 25 to 150 μm, approximately 25 to 120 μm, approximately 25 to 100 μm, and approximately 25 to 90 μm. When the barrier layer 52 is made of aluminum alloy foil, from the viewpoint of imparting high conformability and high rigidity to the exterior film 50, the thickness of the barrier layer 52 is preferably about 40 μm or more, more preferably about 60 μm or more, even more preferably about 70 μm or more, and even more preferably about 80 μm or more, and is preferably about 200 μm or less, more preferably about 150 μm or less, even more preferably about 120 μm or less, even more preferably about 100 μm or less, and even more preferably about 90 μm or less. Examples of suitable thickness ranges include about 40 to 200 μm, about 40 to 150 μm, about 40 to 120 μm, about 40 to 100 μm, about 40 to 90 μm, about 60 to 200 μm, about 60 to 150 μm, about 60 to 120 μm, about 60 to 100 μm, about 60 to 90 μm, about 70 to 200 μm, about 70 to 150 μm, about 70 to 120 μm, about 70 to 100 μm, about 70 to 90 μm, about 80 to 200 μm, about 80 to 150 μm, about 80 to 120 μm, about 80 to 100 μm, and about 80 to 90 μm. The high conformability of the exterior film 50 can contribute to increasing the capacity of the electricity storage device. Furthermore, while increasing the capacity of an electricity storage device increases the weight of the electricity storage device, increasing the rigidity of the exterior film 50 contributes to a high level of sealing of the electricity storage device. In particular, when the barrier layer 52 is made of stainless steel foil, the thickness of the stainless steel foil is preferably approximately 80 μm or less, more preferably approximately 70 μm or less, even more preferably approximately 65 μm or less, even more preferably approximately 60 μm or less, and particularly preferably approximately 50 μm or less. The thickness of the stainless steel foil is preferably approximately 10 μm or more, more preferably approximately 15 μm or more. Preferred thickness ranges for the stainless steel foil include approximately 10 to 80 μm, approximately 10 to 70 μm, approximately 10 to 65 μm, approximately 10 to 60 μm, approximately 10 to 50 μm, approximately 15 to 80 μm, approximately 15 to 70 μm, approximately 15 to 65 μm, approximately 15 to 60 μm, and approximately 15 to 50 μm.

Furthermore, when the barrier layer 52 is a metal foil, it is preferable to provide a corrosion-resistant coating on at least the surface opposite the substrate layer to prevent dissolution and corrosion. The barrier layer 52 may also be provided with a corrosion-resistant coating on both sides. Here, a corrosion-resistant coating refers to a thin film formed on the surface of the barrier layer, for example, by hydrothermal conversion treatment such as boehmite treatment, chemical conversion treatment, anodizing treatment, plating treatment with nickel or chromium, or corrosion prevention treatment such as applying a coating agent, to provide the barrier layer with corrosion resistance (e.g., acid resistance, alkali resistance, etc.). Specifically, a corrosion-resistant coating refers to a coating that improves the acid resistance of the barrier layer (acid-resistant coating) or a coating that improves the alkali resistance of the barrier layer (alkali-resistant coating). The corrosion-resistant coating may be formed by one type of treatment or a combination of two or more types. Furthermore, a single layer or multiple layers can be formed. Furthermore, among these treatments, hydrothermal conversion treatment and anodizing treatment dissolve the metal foil surface with a treatment agent to form a metal compound with excellent corrosion resistance. These treatments may also be included in the definition of chemical conversion treatment. Also, if the barrier layer 52 is provided with a corrosion-resistant coating, the corrosion-resistant coating is also included in the barrier layer 52.

The corrosion-resistant coating prevents delamination between the barrier layer (e.g., aluminum alloy foil) and the substrate layer during molding of the exterior film, prevents dissolution and corrosion of the barrier layer surface due to hydrogen fluoride produced by the reaction between the electrolyte and water, and particularly prevents dissolution and corrosion of aluminum oxide present on the barrier layer surface when the barrier layer is aluminum alloy foil, and also improves the adhesion (wettability) of the barrier layer surface, preventing delamination between the substrate layer and barrier layer during heat sealing and molding.

Various corrosion-resistant coatings formed by chemical conversion treatments are known, including those containing at least one of phosphates, chromates, fluorides, triazine thiol compounds, and rare earth oxides. Examples of chemical conversion treatments using phosphates and chromates include chromate chromate treatment, phosphate chromate treatment, phosphate-chromate treatment, and chromate treatment. Chromium compounds used in these treatments include chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium biphosphate, chromate acetylacetate, chromium chloride, and potassium chromium sulfate. Phosphorus compounds used in these treatments include sodium phosphate, potassium phosphate, ammonium phosphate, and polyphosphoric acid. Chromate treatments include etching chromate treatment, electrolytic chromate treatment, and paint-on chromate treatment, with paint-on chromate treatment being preferred. This paint-type chromate treatment involves first degreasing at least the inner surface of a barrier layer (e.g., an aluminum alloy foil) using a well-known method such as alkali immersion, electrolytic cleaning, acid pickling, electrolytic pickling, or acid activation, and then coating the degreased surface with a treatment solution containing, as its main component, a metal phosphate such as chromium (Cr) phosphate, titanium (Ti) phosphate, zirconium (Zr) phosphate, or zinc (Zn) phosphate, or a mixture of these metal salts, or a treatment solution containing, as its main component, a nonmetallic phosphate and a mixture of these nonmetallic salts, or a mixture of these with a synthetic resin, by a well-known coating method such as roll coating, gravure printing, or immersion, followed by drying. The treatment solution can be, for example, water, alcoholic solvents, hydrocarbon solvents, ketone solvents, ester solvents, or ether solvents, with water being preferred. The resin component used here may include polymers such as phenolic resins and acrylic resins, and examples thereof include chromate treatment using an aminated phenolic polymer having repeating units represented by the following general formulas (1) to (4). The aminated phenolic polymer may contain one repeating unit represented by the following general formulas (1) to (4) alone, or any combination of two or more repeating units. The acrylic resin is preferably polyacrylic acid, an acrylic acid-methacrylic acid ester copolymer, an acrylic acid-maleic acid copolymer, an acrylic acid-styrene copolymer, or a derivative thereof, such as a sodium salt, an ammonium salt, or an amine salt. Derivatives of polyacrylic acid, such as the ammonium salt, sodium salt, or amine salt of polyacrylic acid, are particularly preferred. In this disclosure, polyacrylic acid refers to a polymer of acrylic acid. The acrylic resin is also preferably a copolymer of acrylic acid and a dicarboxylic acid or a dicarboxylic acid anhydride, and preferably an ammonium salt, a sodium salt, or an amine salt of a copolymer of acrylic acid and a dicarboxylic acid or a dicarboxylic acid anhydride. Only one type of acrylic resin may be used, or two or more types may be mixed together.

In general formulas (1) to (4), X represents a hydrogen atom, a hydroxy group, an alkyl group, a hydroxyalkyl group, an allyl group, or a benzyl group. ^R1 and ^R2 , which may be the same or different, represent a hydroxy group, an alkyl group, or a hydroxyalkyl group. In general formulas (1) to (4), examples of the alkyl group represented by X, ^R1 , and ^R2 include linear or branched alkyl groups having 1 to 4 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group. Examples of the hydroxyalkyl group represented by X, ^R1 , and ^R2 include linear or branched alkyl groups having 1 to 4 carbon atoms and substituted with one hydroxy group, such as a hydroxymethyl group, a 1-hydroxyethyl group, a 2-hydroxyethyl group, a 1-hydroxypropyl group, a 2-hydroxypropyl group, a 3-hydroxypropyl group, a 1-hydroxybutyl group, a 2-hydroxybutyl group, a 3-hydroxybutyl group, and a 4-hydroxybutyl group. In general formulas (1) to (4), the alkyl groups and hydroxyalkyl groups represented by X, ^R1 , and ^R2 may be the same or different. In general formulas (1) to (4), X is preferably a hydrogen atom, a hydroxy group, or a hydroxyalkyl group. The number-average molecular weight of the aminated phenol polymer having repeating units represented by general formulas (1) to (4) is preferably, for example, about 500 to 1,000,000, and more preferably about 1,000 to 20,000. The aminated phenol polymer can be produced, for example, by polycondensing a phenol compound or a naphthol compound with formaldehyde to produce a polymer comprising repeating units represented by general formula ( ₁ ) or ^{(3), and then introducing a functional group (—CH2NR1R2) into the resulting polymer using formaldehyde and an amine (R1R2NH ) . The} aminated phenol polymer may be used alone or in combination of two or more types.

Other examples of corrosion-resistant coatings include thin films formed by a coating-type corrosion prevention treatment in which a coating agent containing at least one selected from the group consisting of rare earth element oxide sol, anionic polymer, and cationic polymer is applied. The coating agent may further contain phosphoric acid or phosphate salts, and a crosslinking agent for crosslinking the polymer. The rare earth element oxide sol contains rare earth element oxide fine particles (e.g., particles with an average particle size of 100 nm or less) dispersed in a liquid dispersion medium. Examples of rare earth element oxides include cerium oxide, yttrium oxide, neodymium oxide, and lanthanum oxide, with cerium oxide being preferred for improved adhesion. The rare earth element oxides contained in the corrosion-resistant coating can be used alone or in combination of two or more. Liquid dispersion media for the rare earth element oxide sol can include various solvents, such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester-based solvents, and ether-based solvents, with water being preferred. Preferred examples of cationic polymers include polyethyleneimine, ionic polymer complexes consisting of polyethyleneimine and a polymer having a carboxylic acid, primary amine-grafted acrylic resins in which a primary amine is graft-polymerized onto an acrylic backbone, polyallylamine or its derivatives, and aminated phenols. Preferred anionic polymers are poly(meth)acrylic acid or its salts, or copolymers primarily composed of (meth)acrylic acid or its salts. The crosslinking agent is preferably at least one selected from the group consisting of compounds having a functional group selected from isocyanate, glycidyl, carboxyl, and oxazoline groups, and silane coupling agents. The phosphoric acid or phosphoric acid salt is preferably condensed phosphoric acid or a condensed phosphate salt.

One example of a corrosion-resistant coating is one formed by applying a solution of fine particles of metal oxides such as aluminum oxide, titanium oxide, cerium oxide, and tin oxide, or barium sulfate dispersed in phosphoric acid to the surface of the barrier layer and then baking it at 150°C or higher.

If necessary, the corrosion-resistant coating may have a laminated structure in which at least one of a cationic polymer and an anionic polymer is further laminated. Examples of cationic polymers and anionic polymers include those described above.

The composition of the corrosion-resistant coating can be analyzed using, for example, time-of-flight secondary ion mass spectrometry.

The amount of the corrosion-resistant coating formed on the surface of the barrier layer 52 in the chemical conversion treatment is not particularly limited. For example, in the case of applying chromate treatment, it is desirable that the chromate compound be contained in an ^amount of, for example, about 0.5 to 50 mg, and preferably about 1.0 to 40 mg, calculated as chromium, the phosphorus compound be contained in an amount of, for example, about 0.5 to 50 mg, and preferably about 1.0 to 40 mg, calculated as phosphorus, and the aminated phenol polymer be contained in an amount of, for example, about 1.0 to 200 mg, and preferably about 5.0 to 150 mg, calculated as phosphorus, per 1 m2 of the surface of the barrier layer 52.

The thickness of the corrosion-resistant coating is not particularly limited, but is preferably about 1 nm to 20 μm, more preferably about 1 nm to 100 nm, and even more preferably about 1 nm to 50 nm, from the viewpoint of the cohesive strength of the coating and the adhesion strength with the barrier layer and the thermally adhesive resin layer. The thickness of the corrosion-resistant coating can be measured by observation with a transmission electron microscope, or by a combination of observation with a transmission electron microscope and energy dispersive X-ray spectroscopy or electron energy loss spectroscopy. Analysis of the composition of the corrosion-resistant coating using time-of-flight secondary ion mass spectrometry detects peaks derived from, for example, secondary ions composed of Ce, P, and O (e.g., at least one of Ce ₂ PO ₄ ⁺ and CePO ₄ ⁻ ) or secondary ions composed of Cr, P, and O (e.g., at least one of CrPO ₂ ⁺ and CrPO ₄ ⁻ ).

Chemical conversion treatment is performed by applying a solution containing the compound used to form the corrosion-resistant coating to the surface of the barrier layer using methods such as bar coating, roll coating, gravure coating, or immersion, and then heating the barrier layer to a temperature of approximately 70 to 200°C. Furthermore, before applying chemical conversion treatment to the barrier layer, the barrier layer may be subjected to a degreasing treatment using methods such as alkaline immersion, electrolytic cleaning, acid cleaning, or electrolytic acid cleaning. Performing such a degreasing treatment allows for more efficient chemical conversion treatment of the barrier layer surface. Furthermore, using an acid degreasing agent in which a fluorine-containing compound is dissolved in an inorganic acid not only degreases the metal foil but also forms a passive metal fluoride. In such cases, it is possible to perform only the degreasing treatment.

[Thermofusible resin layer 53]
In the exterior film of the present disclosure, the heat-sealable resin layer 53 corresponds to the innermost layer, and is a layer (sealant layer) that performs the function of sealing the electrode body 20 by heat sealing when assembling the electricity storage device.

The resin constituting the heat-sealable resin layer 53 is not particularly limited as long as it is heat-sealable, but resins containing a polyolefin skeleton, such as polyolefin and acid-modified polyolefin, are preferred. The polyolefin skeleton of the resin constituting the heat-sealable resin layer 53 can be determined by, for example, infrared spectroscopy or gas chromatography-mass spectrometry. Furthermore, when the resin constituting the heat-sealable resin layer 53 is analyzed by infrared spectroscopy, peaks derived from maleic anhydride are preferably detected. For example, when measuring maleic anhydride-modified polyolefin by infrared spectroscopy, peaks derived from maleic anhydride are detected near wavenumbers 1760 cm ⁻¹ and 1780 cm ⁻¹ . When the heat-sealable resin layer 53 is a layer composed of maleic anhydride-modified polyolefin, peaks derived from maleic anhydride are detected by infrared spectroscopy. However, if the degree of acid modification is low, the peaks may be small and not be detected. In such cases, analysis can be performed by nuclear magnetic resonance spectroscopy.

The heat-sealable resin layer 53 preferably contains a resin having a polyolefin skeleton as its primary component, more preferably a polyolefin as its primary component, and even more preferably polypropylene as its primary component. Here, "primary component" refers to a resin component whose content of the resin components contained in the heat-sealable resin layer 53 is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more. For example, "the heat-sealable resin layer 53 contains polypropylene as its primary component" means that the polypropylene content of the resin components contained in the heat-sealable resin layer 53 is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more.

Specific examples of polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); propylene-α-olefin copolymers; and ethylene-butene-propylene terpolymers. Of these, polypropylene is preferred. When the polyolefin resin is a copolymer, it may be a block copolymer or a random copolymer. These polyolefin resins may be used alone or in combination of two or more.

The polyolefin may also be a cyclic polyolefin. Cyclic polyolefins are copolymers of olefins and cyclic monomers. Examples of olefins that constitute the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, styrene, butadiene, and isoprene. Examples of cyclic monomers that constitute the cyclic polyolefin include cyclic alkenes such as norbornene; and cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these, cyclic alkenes are preferred, and norbornene is even more preferred.

The polyolefin may also be an acid-modified polyolefin. Acid-modified polyolefins are polymers modified by block polymerization or graft polymerization of polyolefins with an acid component. Examples of acid-modified polyolefins include the above-mentioned polyolefins, copolymers of the above-mentioned polyolefins with polar molecules such as acrylic acid or methacrylic acid, and polymers such as cross-linked polyolefins. Examples of acid components used for acid modification include carboxylic acids or anhydrides such as maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

The acid-modified polyolefin may be an acid-modified cyclic polyolefin. An acid-modified cyclic polyolefin is a polymer obtained by copolymerizing a portion of the monomers constituting the cyclic polyolefin with an acid component, or by block or graft polymerizing an acid component onto a cyclic polyolefin. The acid-modified cyclic polyolefin is the same as described above. The acid component used for the acid modification is the same as the acid component used to modify the polyolefin described above.

Preferred acid-modified polyolefins include polyolefins modified with carboxylic acids or their anhydrides, polypropylenes modified with carboxylic acids or their anhydrides, maleic anhydride-modified polyolefins, and maleic anhydride-modified polypropylenes.

The heat-sealable resin layer 53 may be formed from a single type of resin, or from a blend polymer of two or more types of resin. Furthermore, the heat-sealable resin layer 53 may be formed from only one layer, or from two or more layers of the same or different resins.

When manufacturing the exterior film 50 of the present disclosure by laminating the heat-sealable resin layer 53 with the barrier layer 52, adhesive layer 55, etc., a pre-formed resin film may be used as the heat-sealable resin layer 53. Alternatively, the heat-sealable resin that forms the heat-sealable resin layer 53 may be formed into a film on the surface of the barrier layer 52, adhesive layer 55, etc. by extrusion molding, coating, etc., to form the heat-sealable resin layer 53 from a resin film.

The heat-sealable resin layer 53 may also contain a lubricant, if necessary. If the heat-sealable resin layer 53 contains a lubricant, it can improve the conformability of the exterior film when it is wrapped around the electrode body. There are no particular restrictions on the lubricant, and any known lubricant can be used.

The lubricant is not particularly limited, but preferably an amide-based lubricant is used. Specific examples of lubricants include those exemplified for the base layer 51. One type of lubricant may be used alone, or two or more types may be used in combination, with a combination of two or more types being preferred.

In the present disclosure, from the viewpoint of improving the conformability of the exterior film when it is wrapped around the electrode body, it is preferable that a lubricant be present on at least one of the surface and interior of the heat-sealable resin layer 53. The lubricant is not particularly limited, but preferably an amide-based lubricant is used. Specific examples of amide-based lubricants include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides. Specific examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Specific examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Specific examples of substituted amides include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, and N-stearyl erucic acid amide. Specific examples of methylolamides include methylol stearic acid amide. Specific examples of saturated fatty acid bisamides include methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene hydroxystearic acid amide, N,N'-distearyl adipamide, N,N'-distearyl sebacic acid amide, etc. Specific examples of unsaturated fatty acid bisamides include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipamide, N,N'-dioleyl sebacic acid amide, etc. Specific examples of fatty acid ester amides include stearamidoethyl stearate, etc. Specific examples of aromatic bisamides include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, and N,N'-distearyl isophthalic acid amide. The lubricant may be used alone or in combination of two or more types, with a combination of two or more types being preferred.

When a lubricant is present on the surface of the heat-fusible resin layer 53, the amount thereof is not particularly limited, but from the viewpoint of improving the conformability of the exterior film, it is preferably about 1 mg/ ^m2 or more, more preferably about 3 mg/ ^m2 or more, even more preferably about 5 mg/ ^m2 or more, even more preferably about 10 mg/ ^m2 or more, and even more preferably about 15 mg/ ^m2 or more, and is preferably about 50 mg/ ^m2 or less, and even more preferably about 40 mg/ ^m2 or less. Preferred ranges include about 1 to 50 mg/ ^m2 , about 1 to 40 mg/ ^m2 , ^about 3 to 50 mg/m2, about 3 to 40 mg/ ^m2 , about ⁵ to 50 mg/m2, ^about 5 to 40 mg/m2, about 10 to 50 mg/ ^m2 , about ¹⁰ to 40 mg/m2, ^about 15 to 50 mg/m2, and about 15 to 40 mg/ ^m2 .

When a lubricant is present inside the heat-sealable resin layer 53, the amount thereof is not particularly limited, but from the viewpoint of improving the conformability of the exterior film, it is preferably at least about 100 ppm, more preferably at least about 300 ppm, and even more preferably at least about 500 ppm, and is preferably at most about 3000 ppm, more preferably at most about 2000 ppm. Preferred ranges include approximately 100-3000 ppm, approximately 100-2000 ppm, approximately 300-3000 ppm, approximately 300-2000 ppm, approximately 500-3000 ppm, and approximately 500-2000 ppm. When two or more types of lubricant are present inside the heat-sealable resin layer 53, the above amount of lubricant is the total amount of lubricant. Furthermore, when two or more types of lubricants are present inside the heat-sealable resin layer 53, the amount of the first type of lubricant present is not particularly limited, but from the viewpoint of improving the conformability of the exterior film, it is preferably about 100 ppm or more, more preferably about 300 ppm or more, even more preferably about 500 ppm or more, and is preferably about 3000 ppm or less, more preferably about 2000 ppm or less, and preferred ranges include about 100 to 3000 ppm, about 100 to 2000 ppm, about 300 to 3000 ppm, about 300 to 2000 ppm, about 500 to 3000 ppm, and about 500 to 2000 ppm. The amount of the second type of lubricant is not particularly limited, but from the perspective of improving the conformability of the exterior film, it is preferably at least about 50 ppm, more preferably at least about 100 ppm, and even more preferably at least about 200 ppm, and is preferably at most about 1500 ppm, more preferably at most about 1000 ppm. Preferred ranges include approximately 50 to 1500 ppm, approximately 50 to 1000 ppm, approximately 100 to 1500 ppm, approximately 100 to 1000 ppm, approximately 200 to 1500 ppm, and approximately 200 to 1000 ppm.

The lubricant present on the surface of the heat-sealable resin layer 53 may be a lubricant exuded from the resin that constitutes the heat-sealable resin layer 53, or a lubricant applied to the surface of the heat-sealable resin layer 53.

The thickness of the heat-sealable resin layer 53 is not particularly limited as long as it functions to seal the electrode body by heat-sealing the heat-sealable resin layers together, but examples include approximately 100 μm or less, preferably approximately 85 μm or less, and more preferably approximately 15 to 85 μm. For example, if the thickness of the adhesive layer 55 described below is 10 μm or greater, the thickness of the heat-sealable resin layer 53 is preferably approximately 85 μm or less, and more preferably approximately 15 to 45 μm. For example, if the thickness of the adhesive layer 55 described below is less than 10 μm or if the adhesive layer 55 is not provided, the thickness of the heat-sealable resin layer 53 is preferably approximately 20 μm or more, and more preferably approximately 35 to 85 μm.

[Adhesive layer 55]
In the exterior film of the present disclosure, the adhesive layer 55 is a layer that is provided as needed between the barrier layer 52 (or the corrosion-resistant coating) and the heat-sealable resin layer 53 in order to firmly bond them together.

The adhesive layer 55 is formed from a resin capable of bonding the barrier layer 52 and the heat-sealable resin layer 53. The resin used to form the adhesive layer 55 can be, for example, the same adhesive as exemplified for the adhesive layer 54.

In addition, from the viewpoint of firmly adhering the adhesive layer 55 and the heat-sealable resin layer 53, the resin used to form the adhesive layer 55 preferably contains a polyolefin skeleton, such as the polyolefins, acid-modified polyolefins, cyclic polyolefins, and acid-modified cyclic polyolefins exemplified above for the heat-sealable resin layer 53. On the other hand, from the viewpoint of firmly adhering the barrier layer 52 and the adhesive layer 55, the adhesive layer 55 preferably contains an acid-modified polyolefin. Examples of acid-modified components include dicarboxylic acids such as maleic acid, itaconic acid, succinic acid, and adipic acid, as well as their anhydrides, acrylic acid, and methacrylic acid. However, maleic anhydride is most preferred in terms of ease of modification and versatility. In addition, from the viewpoint of the heat resistance of the exterior film, the olefin component is preferably a polypropylene-based resin, and the adhesive layer 55 most preferably contains maleic anhydride-modified polypropylene.

When the resin used to form the adhesive layer 55 contains a polyolefin skeleton, the adhesive layer 55 preferably contains a resin containing a polyolefin skeleton as a primary component, more preferably an acid-modified polyolefin as a primary component, and even more preferably an acid-modified polypropylene as a primary component. Here, "primary component" refers to a resin component that accounts for, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more of the resin components contained in the adhesive layer 55. For example, "the adhesive layer 55 contains acid-modified polypropylene as a primary component" means that the acid-modified polypropylene content of the resin components contained in the adhesive layer 55 is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more.

Whether the resin constituting the adhesive layer 55 contains a polyolefin skeleton can be determined by, for example, infrared spectroscopy, gas chromatography mass spectrometry, or the like; the analysis method is not particularly limited. Furthermore, whether the resin constituting the adhesive layer 55 contains an acid-modified polyolefin can be determined, for example, by measuring maleic anhydride-modified polyolefin by infrared spectroscopy, whereby peaks derived from maleic anhydride are detected at wavenumbers of approximately 1760 ^cm and 1780 ^cm . However, if the degree of acid modification is low, the peaks may be small and not be detected. In such cases, analysis can be performed by nuclear magnetic resonance spectroscopy.

Furthermore, from the perspective of ensuring durability, such as heat resistance and resistance to contents, of the exterior film, and ensuring conformability while reducing the thickness, it is more preferable that the adhesive layer 55 be a cured product of a resin composition containing an acid-modified polyolefin and a curing agent. Preferred examples of acid-modified polyolefins include those listed above.

The adhesive layer 55 is preferably a cured product of a resin composition containing an acid-modified polyolefin and at least one compound selected from the group consisting of a compound having an isocyanate group, a compound having an oxazoline group, and a compound having an epoxy group. It is particularly preferably a cured product of a resin composition containing an acid-modified polyolefin and at least one compound selected from the group consisting of a compound having an isocyanate group and a compound having an epoxy group. The adhesive layer 55 preferably contains at least one compound selected from the group consisting of polyurethane, polyester, and epoxy resin, and more preferably contains polyurethane and epoxy resin. Preferred polyesters include, for example, ester resins formed by the reaction of epoxy groups with maleic anhydride groups, and amide ester resins formed by the reaction of oxazoline groups with maleic anhydride groups. If unreacted components of the curing agent, such as the compound having an isocyanate group, the compound having an oxazoline group, or the epoxy resin, remain in the adhesive layer 55, the presence of the unreacted components can be confirmed by a method selected from, for example, infrared spectroscopy, Raman spectroscopy, or time-of-flight secondary ion mass spectrometry (TOF-SIMS).

In order to further enhance the adhesion between the barrier layer 52 and the adhesive layer 55, the adhesive layer 55 is preferably a cured product of a resin composition containing a curing agent having at least one selected from the group consisting of an oxygen atom, a heterocycle, a C=N bond, and a C-O-C bond. Examples of curing agents having a heterocycle include curing agents having an oxazoline group and curing agents having an epoxy group. Examples of curing agents having a C=N bond include curing agents having an oxazoline group and curing agents having an isocyanate group. Examples of curing agents having a C-O-C bond include curing agents having an oxazoline group and curing agents having an epoxy group. Whether the adhesive layer 55 is a cured product of a resin composition containing such a curing agent can be confirmed by, for example, gas chromatography mass spectrometry (GCMS), infrared spectroscopy (IR), time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), or other methods.

The compound having an isocyanate group is not particularly limited, but from the viewpoint of effectively increasing the adhesion between the barrier layer 52 and the adhesive layer 55, a polyfunctional isocyanate compound is preferable. The polyfunctional isocyanate compound is not particularly limited as long as it has two or more isocyanate groups. Specific examples of polyfunctional isocyanate curing agents include pentane diisocyanate (PDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymers or nurates thereof, mixtures of these, and copolymers with other polymers. Other examples include adducts, biurets, and isocyanurates.

The content of the compound having an isocyanate group in the adhesive layer 55 is preferably in the range of 0.1 to 50 mass % of the resin composition constituting the adhesive layer 55, and more preferably in the range of 0.5 to 40 mass %. This effectively improves the adhesion between the barrier layer 52 and the adhesive layer 55.

The compound having an oxazoline group is not particularly limited as long as it has an oxazoline skeleton. Specific examples of compounds having an oxazoline group include those having a polystyrene main chain and those having an acrylic main chain. Commercially available products include the Epocross series manufactured by Nippon Shokubai Co., Ltd.

The proportion of the compound having an oxazoline group in the adhesive layer 55 is preferably in the range of 0.1 to 50 mass %, and more preferably in the range of 0.5 to 40 mass %, of the resin composition that constitutes the adhesive layer 55. This effectively improves the adhesion between the barrier layer 52 and the adhesive layer 55.

An example of a compound having an epoxy group is an epoxy resin. There are no particular restrictions on the epoxy resin, so long as it is a resin capable of forming a crosslinked structure via the epoxy groups present in the molecule, and any known epoxy resin can be used. The weight-average molecular weight of the epoxy resin is preferably approximately 50 to 2,000, more preferably approximately 100 to 1,000, and even more preferably approximately 200 to 800. In this disclosure, the weight-average molecular weight of the epoxy resin is a value measured by gel permeation chromatography (GPC) using polystyrene as a standard sample.

Specific examples of epoxy resins include glycidyl ether derivatives of trimethylolpropane, bisphenol A diglycidyl ether, modified bisphenol A diglycidyl ether, bisphenol F glycidyl ether, novolac glycidyl ether, glycerin polyglycidyl ether, and polyglycerin polyglycidyl ether. Epoxy resins may be used alone or in combination of two or more.

The proportion of epoxy resin in the adhesive layer 55 is preferably in the range of 0.1 to 50 mass % of the resin composition constituting the adhesive layer 55, and more preferably in the range of 0.5 to 40 mass %. This effectively improves the adhesion between the barrier layer 52 and the adhesive layer 55.

The polyurethane is not particularly limited, and any known polyurethane can be used. The adhesive layer 55 may be, for example, a cured product of two-component curing polyurethane.

The proportion of polyurethane in the adhesive layer 55 is preferably in the range of 0.1 to 50 mass % of the resin composition constituting the adhesive layer 55, and more preferably in the range of 0.5 to 40 mass %. This effectively improves the adhesion between the barrier layer 52 and the adhesive layer 55 in an atmosphere containing components that induce corrosion of the barrier layer, such as an electrolyte solution.

When the adhesive layer 55 is a cured product of a resin composition containing at least one selected from the group consisting of a compound having an isocyanate group, a compound having an oxazoline group, and an epoxy resin, and the acid-modified polyolefin, the acid-modified polyolefin functions as the base resin, and the compound having an isocyanate group, the compound having an oxazoline group, and the compound having an epoxy group each function as a curing agent.

The adhesive layer 55 may contain a modifier having a carbodiimide group.

From the viewpoint of more effectively achieving the effects of the present disclosure, the adhesive layer 55 is preferably formed from a resin composition that contains acid-modified polypropylene and an elastomer, and further contains at least one of block polypropylene and homopolypropylene. The resin composition may further contain random polypropylene, polyethylene, etc. Note that, from the viewpoint of improving adhesion to the barrier layer 52 and heat resistance, the adhesive layer 55 is preferably made of acid-modified homopolypropylene (i.e., acid-modified homopolypropylene).

From the perspective of more optimally achieving the effects of the present disclosure, the content of acid-modified polypropylene in the resin composition forming adhesive layer 55 is preferably about 5% by mass or more, more preferably about 10% by mass or more, even more preferably about 15% by mass or more, and is preferably about 90% by mass or less, more preferably about 80% by mass or less, and even more preferably about 70% by mass or less. Preferred ranges include approximately 5 to 90% by mass, 5 to 80% by mass, 5 to 70% by mass, 10 to 90% by mass, 10 to 80% by mass, 10 to 70% by mass, 15 to 90% by mass, 15 to 80% by mass, and 15 to 70% by mass.

From the perspective of more optimally achieving the effects of the present disclosure, the elastomer content in the resin composition forming adhesive layer 55 is preferably about 25% by mass or more, more preferably about 30% by mass or more, even more preferably about 35% by mass or more, and is preferably about 60% by mass or less, more preferably about 55% by mass or less, and even more preferably about 50% by mass or less. Preferred ranges include approximately 25 to 60% by mass, approximately 25 to 55% by mass, approximately 25 to 50% by mass, approximately 30 to 60% by mass, approximately 30 to 55% by mass, approximately 30 to 50% by mass, approximately 35 to 60% by mass, approximately 35 to 55% by mass, and approximately 35 to 50% by mass.

From the viewpoint of more optimally achieving the effects of the present disclosure, the elastomer contained in the resin composition forming the adhesive layer 55 is preferably a binary copolymer or a tertiary copolymer. Furthermore, the elastomer is preferably a propylene-based elastomer. Examples of propylene-based elastomers include binary copolymers and tertiary copolymers. Examples of binary copolymers include propylene-ethylene copolymer elastomers and propylene-butene copolymer elastomers, and examples of tertiary copolymers include propylene-ethylene-butene copolymer elastomers and ethylene-propylene-diene copolymer elastomers. Among elastomers, propylene-ethylene copolymer elastomers are preferred as binary copolymers, and propylene-ethylene-butene copolymer elastomers are preferred as tertiary copolymers.

From the perspective of more optimally achieving the effects of the present disclosure, the block polypropylene content in the resin composition forming adhesive layer 55 is preferably about 30% by mass or more, more preferably about 35% by mass or more, even more preferably about 40% by mass or more, and is preferably about 95% by mass or less, more preferably about 90% by mass or less, and even more preferably about 85% by mass or less. Preferred ranges include approximately 30 to 95% by mass, 30 to 90% by mass, 30 to 85% by mass, 35 to 95% by mass, 35 to 90% by mass, 35 to 85% by mass, 40 to 95% by mass, 40 to 90% by mass, and 40 to 85% by mass.

Furthermore, from the perspective of more suitably achieving the effects of the present disclosure, the content of homopolypropylene in the resin composition forming adhesive layer 55 is preferably about 20% by mass or more, more preferably about 25% by mass or more, even more preferably about 30% by mass or more, and is preferably about 80% by mass or less, more preferably about 75% by mass or less, even more preferably about 70% by mass or less. Preferred ranges include approximately 20 to 80% by mass, approximately 20 to 75% by mass, approximately 20 to 70% by mass, approximately 25 to 80% by mass, approximately 25 to 75% by mass, approximately 25 to 70% by mass, approximately 30 to 80% by mass, approximately 30 to 75% by mass, and approximately 30 to 70% by mass.

From the perspective of more optimally achieving the effects of the present disclosure, the content of random polypropylene in the resin composition forming adhesive layer 55 is preferably about 0% by mass or more, more preferably about 1% by mass or more, even more preferably about 2% by mass or more, and preferably about 30% by mass or less, more preferably about 25% by mass or less, and even more preferably about 20% by mass or less. Preferred ranges include approximately 0-30% by mass, 0-25% by mass, 0-20% by mass, 1-30% by mass, 1-25% by mass, 1-20% by mass, 2-30% by mass, 2-25% by mass, and 2-20% by mass.

From the perspective of more optimally achieving the effects of the present disclosure, the polyethylene content in the resin composition forming adhesive layer 55 is, for example, about 0% by mass or more, preferably about 1% by mass or more, more preferably about 2% by mass or more, and even more preferably about 3% by mass or more. It is also preferably about 30% by mass or less, more preferably about 25% by mass or less, and even more preferably about 20% by mass or less. Preferred ranges include approximately 0-30% by mass, 0-25% by mass, 0-20% by mass, 1-30% by mass, 1-25% by mass, 1-20% by mass, 2-30% by mass, 2-25% by mass, 2-20% by mass, 3-30% by mass, 3-25% by mass, and 3-20% by mass.

From the viewpoint of more suitably exerting the effects of the present disclosure, the specific composition of the resin composition may, for example, have an acid-modified polypropylene content of about 5% by mass or more (more preferably about 10% by mass or more, even more preferably about 15% by mass or more, and preferably about 90% by mass or less, more preferably about 80% by mass or less, and even more preferably about 70% by mass or less; preferred ranges include about 5 to 90% by mass, about 5 to 80% by mass, about 5 to 70% by mass, about 10 to 90% by mass, about 10 to 80% by mass, about 10 to 70% by mass, about 15 to 90% by mass, about 15 to 80% by mass, and about 15 to 70% by mass), and an elastomer content of about 25% by mass or more (more preferably about 30% by mass or more, even more preferably about 35% by mass or more, and preferably about 60% by mass or less, and even more preferably about 55% by mass). The content of block polypropylene is about 30% by mass or more (more preferably about 35% by mass or more, even more preferably about 40% by mass or more, and also preferably about 95% by mass or less, more preferably about 90% by mass or less, even more preferably about 85% by mass or less. Preferred ranges include about 30 to 95% by mass, about 30 to 90% by mass, about 30 to 85% by mass, about 35 to 95% by mass, about 35 to 90% by mass, about 35 to 85% by mass, about 40 to 95% by mass, about 40 to 90% by mass, and about 40 to 85% by mass). % or so), the homopolypropylene content is about 20% by mass or more (more preferably about 25% by mass or more, even more preferably about 30% by mass or more, and also preferably about 80% by mass or less, more preferably about 75% by mass or less, and even more preferably about 70% by mass or less, with preferred ranges being about 20 to 80% by mass, about 20 to 75% by mass, about 20 to 70% by mass, about 25 to 80% by mass, about 25 to 75% by mass, about 25 to 70% by mass, about 30 to 80% by mass, about 30 to 75% by mass, about 30 to 70% by mass, etc.), and the random polypropylene content is about 0% by mass or more (more preferably about 1% by mass or more, even more preferably about 2% by mass or more, and also preferably about 30% by mass or less, more preferably about 25% by mass or less, and even more preferably about 20% by mass or less. Preferred ranges include The polyethylene content is, for example, about 0 to 30% by mass, about 0 to 25% by mass, about 0 to 20% by mass, about 1 to 30% by mass, about 1 to 25% by mass, about 1 to 20% by mass, about 2 to 30% by mass, about 2 to 25% by mass, about 2 to 20% by mass), and the polyethylene content is, for example, about 0% by mass or more (preferably about 1% by mass or more, more preferably about 2% by mass or more, even more preferably about 3% by mass or more, and preferably about 30% by mass or less, more preferably about 25% by mass or less, even more preferably about 20% by mass or less; preferred ranges are about 0 to 30% by mass, about 0 to 25% by mass, about 0 to 20% by mass, about 1 to 30% by mass, about 1 to 25% by mass, about 1 to 20% by mass, about 2 to 30% by mass, about 2 to 25% by mass, about 2 to 20% by mass, about 3 to 30% by mass, about 3 to 25% by mass, about 3 to 20% by mass), etc. The resin composition preferably contains acid-modified polypropylene and an elastomer as resins (excluding additives such as lubricants, which will be described later), and is further formed from a resin composition containing only at least one of block polypropylene and homopolypropylene.

When manufacturing the exterior film 50 of the present disclosure by laminating the adhesive layer 55 with the barrier layer 52, the heat-sealable resin layer 53, or the like, a pre-formed resin film may be used as the adhesive layer 55. Alternatively, the heat-sealable resin that forms the adhesive layer 55 may be formed into a film on the surface of the barrier layer 52, the heat-sealable resin layer 53, or the like by extrusion molding, coating, or the like, to form the adhesive layer 55 from the resin film.

The thickness of the adhesive layer 55 is preferably approximately 50 μm or less, approximately 40 μm or less, approximately 30 μm or less, approximately 20 μm or less, or approximately 5 μm or less. The thickness of the adhesive layer 55 is preferably approximately 0.1 μm or more, or approximately 0.5 μm or more. The thickness of the adhesive layer 55 is preferably approximately 0.1 to 50 μm, approximately 0.1 to 40 μm, approximately 0.1 to 30 μm, approximately 0.1 to 20 μm, approximately 0.1 to 5 μm, approximately 0.5 to 50 μm, approximately 0.5 to 40 μm, approximately 0.5 to 30 μm, approximately 0.5 to 20 μm, or approximately 0.5 to 5 μm. More specifically, in the case of adhesives such as those exemplified for the adhesive layer 54 or a cured product of an acid-modified polyolefin and a curing agent, the thickness is preferably approximately 1 to 10 μm, and more preferably approximately 1 to 5 μm. Furthermore, when using a resin such as one of the examples for the heat-sealable resin layer 53, the thickness is preferably approximately 2 to 50 μm, and more preferably approximately 10 to 40 μm. When the adhesive layer 55 is an adhesive such as one of the examples for the adhesive layer 54, or a cured product of a resin composition containing an acid-modified polyolefin and a curing agent, the adhesive layer 55 can be formed, for example, by applying the resin composition and curing it by heating or the like. When using a resin such as one of the examples for the heat-sealable resin layer 53, the heat-sealable resin layer 53 and the adhesive layer 55 can be formed, for example, by extrusion molding.

[Surface coating layer]
The exterior film of the present disclosure may have a surface coating layer, if necessary, on the barrier layer 52, on the base material layer 51 that is provided as needed (on the side of the base material layer 51 opposite to the barrier layer 52), or the like, for the purpose of improving at least one of design, electrolyte resistance, scratch resistance, conformability, etc. The surface coating layer is a layer that is located on the outermost layer side of the exterior film when an electricity storage device is assembled using the exterior film.

The surface coating layer may be made of, for example, a resin such as polyvinylidene chloride, polyester, polyamide, epoxy resin, acrylic resin, fluororesin, polyurethane, silicone resin, or phenolic resin, or a modified version of these resins. It may also be a copolymer of these resins or a modified version of the copolymer. It may also be a mixture of these resins. The resin is preferably a curable resin. In other words, the surface coating layer is preferably made of a cured product of a resin composition containing a curable resin.

When the resin forming the surface coating layer is a curable resin, the resin may be either a one-component curable resin or a two-component curable resin, but is preferably a two-component curable resin. Examples of two-component curable resins include two-component curable polyurethane, two-component curable polyester, and two-component curable epoxy resin. Of these, two-component curable polyurethane is preferred.

Examples of two-component curing polyurethanes include polyurethanes containing a first component containing a polyol compound and a second component containing an isocyanate compound. Preferred examples of two-component curing polyurethanes include those containing a polyol, such as polyester polyol, polyether polyol, or acrylic polyol, as the first component and an aromatic or aliphatic polyisocyanate as the second component. Examples of polyurethanes include polyurethane compounds prepared by reacting a polyol compound with an isocyanate compound in advance, and polyurethanes containing an isocyanate compound. Examples of polyurethanes include polyurethane compounds prepared by reacting a polyol compound with an isocyanate compound in advance, and polyurethanes containing a polyol compound. Examples of polyurethanes include polyurethanes prepared by reacting a polyol compound with an isocyanate compound in advance, and polyurethanes cured by reacting the polyurethane compound with moisture, such as in the air, with moisture. Polyol compounds preferably include polyester polyols that have hydroxyl groups on the side chains in addition to the terminal hydroxyl groups of the repeating units. Examples of second components include aliphatic, alicyclic, aromatic, and araliphatic isocyanate compounds. Examples of isocyanate compounds include hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), hydrogenated XDI (H6XDI), hydrogenated MDI (H12MDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and naphthalene diisocyanate (NDI). Also included are polyfunctional isocyanate-modified compounds of one or more of these diisocyanates. Furthermore, polymers (e.g., trimers) can also be used as polyisocyanate compounds. Examples of such polymers include adducts, biurets, and nurates. Note that an aliphatic isocyanate compound refers to an isocyanate that has an aliphatic group but no aromatic ring, an alicyclic isocyanate compound refers to an isocyanate that has an alicyclic hydrocarbon group, and an aromatic isocyanate compound refers to an isocyanate that has an aromatic ring. The surface coating layer is made of polyurethane, which gives the exterior film excellent electrolyte resistance.

The surface coating layer may contain additives such as lubricants, flame retardants, antiblocking agents, antioxidants, light stabilizers, tackifiers, and antistatic agents, as needed, on at least one of the surface and interior of the surface coating layer, depending on the functionality to be provided by the surface coating layer and its surface. Examples of additives include fine particles with an average particle size of approximately 0.5 nm to 5 μm. The average particle size of the additive is the median diameter measured using a laser diffraction/scattering particle size distribution analyzer.

Additives may be either inorganic or organic. There are also no particular restrictions on the shape of the additive, and examples include spherical, fibrous, plate-like, irregular, and scaly shapes.

Specific examples of additives include talc, silica, graphite, kaolin, montmorillonite, mica, hydrotalcite, silica gel, zeolite, aluminum hydroxide, magnesium hydroxide, zinc oxide, magnesium oxide, aluminum oxide, neodymium oxide, antimony oxide, titanium oxide, cerium oxide, calcium sulfate, barium sulfate, calcium carbonate, calcium silicate, lithium carbonate, calcium benzoate, calcium oxalate, magnesium stearate, alumina, carbon black, carbon nanotubes, high-melting-point nylon, acrylate resin, cross-linked acrylic, cross-linked styrene, cross-linked polyethylene, benzoguanamine, gold, aluminum, copper, and nickel. The additives may be used alone or in combination. Among these additives, silica, barium sulfate, and titanium oxide are preferred from the viewpoints of dispersion stability and cost. Furthermore, mica is preferred from the viewpoint of heat dissipation from the power storage device. The additives may also be subjected to various surface treatments, such as insulation treatment and high-dispersion treatment.

The method for forming the surface coating layer is not particularly limited, and examples include a method of applying a resin that forms the surface coating layer. If an additive is to be blended into the surface coating layer, a resin mixed with the additive may be applied.

In the present disclosure, from the viewpoint of improving the conformability when wrapping the exterior film around the electrode body, it is preferable that a lubricant be present on at least one of the surface and interior of the surface coating layer. The lubricant is not particularly limited, but preferably an amide-based lubricant is used. Specific examples of amide-based lubricants include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides. Specific examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Specific examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Specific examples of substituted amides include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, and N-stearyl erucic acid amide. Specific examples of methylolamides include methylol stearic acid amide. Specific examples of saturated fatty acid bisamides include methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene hydroxystearic acid amide, N,N'-distearyl adipamide, N,N'-distearyl sebacic acid amide, etc. Specific examples of unsaturated fatty acid bisamides include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipamide, N,N'-dioleyl sebacic acid amide, etc. Specific examples of fatty acid ester amides include stearamidoethyl stearate, etc. Specific examples of aromatic bisamides include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, and N,N'-distearyl isophthalic acid amide. The lubricant may be used alone or in combination of two or more types, with a combination of two or more types being preferred.

When a lubricant is present on the surface of the surface coating layer, the amount thereof is not particularly limited, but may be, for example, about 3 mg/ ^m2 or more, preferably about 4 mg/ ^m2 or more, or about 5 mg/ ^m2 or more. The amount of lubricant present on the surface of the surface coating layer may be, for example, about 15 mg/ ^m2 or less, preferably about 14 mg/ ^m2 or less, or about 10 mg/ ^m2 or less. Preferred ranges for the amount of lubricant present on the surface of the surface coating layer include ^about 3 to 15 mg/m2, about 3 to 14 mg/ ^m2 , about 3 to 10 mg/ ^m2 , about 4 to 15 mg/ ^m2 , about 4 to 14 mg/ ^m2 , about 4 to 10 mg/ ^m2 , about 5 to 15 mg/ ^m2 , about 5 to 14 mg/ ^m2 , and about 5 to 10 mg/ ^m2 .

The lubricant present on the surface of the surface coating layer may be a lubricant exuded from the resin that makes up the surface coating layer, or a lubricant applied to the surface of the surface coating layer.

The thickness of the surface coating layer is not particularly limited as long as it exhibits the above-mentioned functions as a surface coating layer, but may be, for example, approximately 0.5 to 10 μm, and preferably approximately 1 to 5 μm.

<2-3. Manufacturing method of exterior film>
The method for manufacturing the exterior film is not particularly limited as long as it can produce a laminate in which the layers of the exterior film of the present disclosure are laminated, and examples include methods that include at least a step of laminating a barrier layer 52 and a heat-sealable resin layer 53.

An example of a method for manufacturing an exterior film according to the present disclosure is as follows. First, a laminate (hereinafter sometimes referred to as "laminate A") is formed in which a substrate layer 51, an adhesive layer 54, and a barrier layer 52 are laminated in this order. Specifically, laminate A can be formed by a dry lamination method in which the adhesive used to form the adhesive layer 54 is applied to the substrate layer 51 or to the barrier layer 52, the surface of which has been chemically treated as necessary, by a coating method such as gravure coating or roll coating, and then dried. After that, the barrier layer 52 or substrate layer 51 is laminated, and the adhesive layer 54 is cured.

Next, a heat-sealable resin layer 53 is laminated on the barrier layer 52 of the laminate A. When the heat-sealable resin layer 53 is laminated directly on the barrier layer 52, the heat-sealable resin layer 53 may be laminated on the barrier layer 52 of the laminate A by a method such as thermal lamination or extrusion lamination. When an adhesive layer 55 is provided between the barrier layer 52 and the heat-sealable resin layer 53, the adhesive layer 55 and the heat-sealable resin layer 53 may be laminated by, for example, (1) extrusion lamination, (2) thermal lamination, (3) sandwich lamination, or (4) dry lamination. Examples of the (1) extrusion lamination method include a method of laminating the adhesive layer 55 and the heat-sealable resin layer 53 by extrusion onto the barrier layer 52 of the laminate A (co-extrusion lamination, tandem lamination), etc. Examples of the (2) thermal lamination method include a method of separately forming a laminate in which an adhesive layer 55 and a heat-fusible resin layer 53 are laminated, and laminating this on the barrier layer 52 of the laminate A, or a method of forming a laminate in which an adhesive layer 55 is laminated on the barrier layer 52 of the laminate A, and laminating this on the heat-fusible resin layer 53. Examples of the (3) sandwich lamination method include a method of pouring a molten adhesive layer 55 between the barrier layer 52 of the laminate A and a heat-fusible resin layer 53 previously formed into a sheet, and bonding the laminate A and the heat-fusible resin layer 53 via the adhesive layer 55. Examples of the (4) dry lamination method include a method of solution-coating an adhesive for forming the adhesive layer 55 on the barrier layer 52 of the laminate A, drying the adhesive, or baking the adhesive, and laminating the heat-fusible resin layer 53 previously formed into a sheet on the adhesive layer 55.

When a surface coating layer is provided, the surface coating layer is laminated on the surface of the base layer 51 opposite the barrier layer 52. The surface coating layer can be formed, for example, by applying the above-mentioned resin that forms the surface coating layer to the surface of the base layer 51. There are no particular restrictions on the order of the step of laminating the barrier layer 52 on the surface of the base layer 51 and the step of laminating the surface coating layer on the surface of the base layer 51. For example, after forming the surface coating layer on the surface of the base layer 51, the barrier layer 52 may be formed on the surface of the base layer 51 opposite the surface coating layer.

As described above, a laminate is formed which comprises, in this order, an optional surface coating layer, an optional base layer 51, an optional adhesive layer 54, a barrier layer 52, an optional adhesive layer 55, and a heat-sealable resin layer 53. In order to strengthen the adhesiveness of the optional adhesive layer 54 and adhesive layer 55, the laminate may be further subjected to a heat treatment.

In the exterior film, each layer constituting the laminate may be subjected to a surface activation treatment such as corona treatment, blast treatment, oxidation treatment, or ozone treatment, as needed, to improve its processability. For example, corona treatment can be performed on the surface of the base layer 51 opposite the barrier layer 52 to improve the printability of ink on the surface of the base layer 51.

<3-1. Laminate structure and physical properties of exterior materials for electricity storage devices>
The packaging material 50 for an electricity storage device according to the present disclosure corresponds to the above-described packaging film 50, and each layer is also common to both. That is, in the laminate constituting the packaging material 50 for an electricity storage device according to the present disclosure, the base material layer 1, adhesive layer 2, barrier layer 3, adhesive layer 5, heat-sealable resin layer 4, and surface coating layer 6 correspond to the base material layer 51, adhesive layer 54, barrier layer 52, adhesive layer 55, heat-sealable resin layer 53, and surface coating layer of the laminate constituting the above-described packaging film 50, respectively.

Like the exterior packaging film 50, the exterior packaging material 50 for an electricity storage device of the present disclosure is composed of a laminate including a barrier layer 3 and a heat-sealable resin layer 4, as shown in FIG. 5, for example. In the exterior packaging material 50 for an electricity storage device, the barrier layer 3 is the outermost layer, and the heat-sealable resin layer 4 is the innermost layer. For example, as shown in FIGS. 10 and 11, when assembling an electricity storage device using the exterior packaging material 50 for an electricity storage device and an electricity storage device element (electrode body 20, electrode terminal 30, etc.), the electrode body 20 is housed in a space formed by heat-sealing the ends of the heat-sealable resin layers 4 of the exterior packaging material 50 for an electricity storage device together with the lid 60 while facing each other. In the laminate constituting the exterior packaging material 50 for an electricity storage device of the present disclosure, the side of the heat-sealable resin layer 4 relative to the barrier layer 3 is the inner side, and the opposite side is the outer side, relative to the barrier layer 3.

As shown in Figures 5 to 8, the electrical storage device packaging material 50 may optionally include a substrate layer 1 on the outside of the barrier layer 3. As shown in Figures 6 to 8, the electrical storage device packaging material 50 may optionally include an adhesive layer 2 between the substrate layer 1 and the barrier layer 3, for example, to enhance adhesion between these layers. As shown in Figures 7 and 8, the electrical storage device packaging material 50 may optionally include an adhesive layer 5 between the barrier layer 3 and the heat-sealable resin layer 4, for example, to enhance adhesion between these layers. As shown in Figure 8, a surface coating layer 6 or the like may be provided on the outside of the substrate layer 1 (the side opposite the heat-sealable resin layer 4) as needed.

The thickness of the laminate constituting the electrical storage device exterior material 50 is not particularly limited, but from the viewpoints of cost reduction, improved energy density, etc., examples of the thickness include approximately 250 μm or less, preferably approximately 190 μm or less, approximately 180 μm or less, approximately 155 μm or less, and approximately 120 μm or less. Furthermore, from the viewpoint of maintaining the function of the electrical storage device exterior material to protect the electrode assembly 20, the thickness of the laminate constituting the electrical storage device exterior material 50 is preferably approximately 35 μm or more, approximately 45 μm or more, or approximately 60 μm or more. Furthermore, preferred ranges for the laminate constituting the electrical storage device exterior material 50 include, for example, approximately 35 to 250 μm, approximately 35 to 190 μm, approximately 35 to 180 μm, approximately 35 to 155 μm, approximately 35 to 120 μm, approximately 45 to 250 μm, approximately 45 to 190 μm, approximately 45 to 180 μm, approximately 45 to 155 μm, approximately 45 to 120 μm, approximately 60 to 250 μm, approximately 60 to 190 μm, approximately 60 to 180 μm, approximately 60 to 155 μm, and approximately 60 to 120 μm. In particular, approximately 60 to 155 μm is preferred when making the electrical storage device lighter and thinner, and approximately 155 to 190 μm is preferred when improving conformability.

In the electrical storage device exterior material 50, the ratio of the total thickness of the optional base material layer 1, optional adhesive layer 2, barrier layer 3, optional adhesive layer 5, heat-sealable resin layer 4, and optional surface coating layer 6 to the thickness (total thickness) of the laminate constituting the electrical storage device exterior material 50 is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. As a specific example, when the electrical storage device exterior material 50 of the present disclosure includes the base material layer 1, adhesive layer 2, barrier layer 3, adhesive layer 5, and heat-sealable resin layer 4, the ratio of the total thickness of these layers to the thickness (total thickness) of the laminate constituting the electrical storage device exterior material 50 is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. Furthermore, even when the electrical storage device packaging material 50 of the present disclosure is a laminate including a substrate layer 1, an adhesive layer 2, a barrier layer 3, and a heat-sealable resin layer 4, the ratio of the total thickness of these layers to the thickness (total thickness) of the laminate constituting the electrical storage device packaging material 50 can be, for example, 80% or more, preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more.

From the viewpoint of more optimally exerting the effects of the presently disclosed invention, the Young's modulus of the exterior material 50 for an electrical storage device is preferably 6,000 MPa or more, more preferably 8,000 MPa or more, and even more preferably 10,000 MPa or more, and is preferably 40,000 MPa or less, more preferably 35,000 MPa or less, and even more preferably 30,000 MPa or less. Preferred ranges include approximately 6,000 to 40,000 MPa, approximately 6,000 to 35,000 MPa, approximately 6,000 to 30,000 MPa, approximately 8,000 to 40,000 MPa, approximately 8,000 to 35,000 MPa, approximately 8,000 to 30,000 MPa, approximately 10,000 to 40,000 MPa, approximately 10,000 to 35,000 MPa, and approximately 10,000 to 30,000 MPa. In this disclosure, the Young's modulus of the exterior material for an electricity storage device is a value measured by the following method.

<Measurement of Young's modulus of exterior material for electricity storage device>
In accordance with the provisions of JIS K6251:2017, an S-S curve in the TD direction of the adhesive film was obtained under the following measurement conditions, and the Young's modulus (MPa) was calculated from the maximum value of the slope of the S-S curve.
(Measurement conditions)
A tensile testing machine is used.
Shape of test piece: Dumbbell No. 7 Width of test piece: 2 mm
Test piece length: 35 mm
Thickness of test piece: measured with a thickness gauge. Gauge distance: 20 mm
Tensile speed: 50 mm/min
Test environment: 23±5°C, 50±30% RH
Number of measurements: Average value of 3 measurements

As explained for the exterior film 50, an effective method for increasing the Young's modulus of the exterior material 50 for an electricity storage device is to increase the Young's modulus of the barrier layer 3.

<3-2. Layers that constitute the exterior packaging material for an electricity storage device>
As described above, in the laminate constituting the exterior packaging material 50 for an electricity storage device of the present disclosure, the base material layer 1, adhesive layer 2, barrier layer 3, adhesive layer 5, heat-sealable resin layer 4, and surface coating layer 6 correspond to the base material layer 51, adhesive layer 54, barrier layer 52, adhesive layer 55, heat-sealable resin layer 53, and surface coating layer, respectively, of the laminate constituting the above-mentioned exterior packaging film 50. Therefore, the explanations of the base material layer 1, adhesive layer 2, barrier layer 3, adhesive layer 5, heat-sealable resin layer 4, and surface coating layer 6 are common to the explanations of the base material layer 51, adhesive layer 54, barrier layer 52, adhesive layer 55, heat-sealable resin layer 53, and surface coating layer of the laminate constituting the above-mentioned exterior packaging film 50, and redundant explanations will be omitted.

In the electrical storage device packaging material disclosed herein, the barrier layer 3 of the electrical storage device packaging material 50 is characterized in that, at a position where the thermally adhesive resin layer of the electrical storage device packaging material and the polypropylene plate are thermally fused under conditions where the thickness of the thermally adhesive resin layer is 20% to 80% or less, the area-average angular difference of the GOS (Grain Orientation Sparse) is 2.50° or less, where the grain boundary is defined as 5°, as obtained by performing crystal analysis using the electron backscattered diffraction (EBSD) method on a cross section obtained by cutting the barrier layer perpendicularly from the surface of the barrier layer in a direction perpendicular to the rolling direction of the barrier layer. The polypropylene plate is intended for use as a lid that constitutes the packaging body. The conditions for the thickness of the thermally adhesive resin layer to be 20% to 80% or less can be adjusted, for example, by setting the heat-fusion temperature to approximately 160 to 240°C, the surface pressure to approximately 0.2 to 1.5 MPa, and the heat-fusion time to approximately 1 to 12 seconds.

From the perspective of more optimally demonstrating the effects of the presently disclosed invention, the area-average angular difference of the GOS (crystal grain orientation dispersion) is preferably approximately 2.50° or less, more preferably approximately 2.00° or less, and even more preferably approximately 1.50° or less. It may also be, for example, approximately 0° or more, approximately 0.20° or more, and preferred ranges include approximately 0 to 2.50°, approximately 0 to 2.00°, approximately 0 to 1.50°, approximately 0.20 to 2.50°, approximately 0.20 to 2.00°, and approximately 0.20 to 1.50°.

The area-average angular difference of the GOS (crystal grain orientation dispersion) of the barrier layer 3 is a value measured by the following method. When obtaining an electrical storage device exterior material from an electrical storage device (for example, obtaining an electrical storage device exterior material from an electrical storage device mounted on a driven automobile) and measuring the area-average angular difference of the GOS (crystal grain orientation dispersion) of the barrier layer 3, a sample is obtained from a portion of the electrical storage device exterior material where the heat-sealable resin layer is not heat-sealed, and the following measurement is performed.

<Measurement of area average angle difference of GOS (grain orientation dispersion) of barrier layer>
For an electric storage device, a barrier layer was obtained at a position where a heat-sealable resin layer of an electric storage device exterior material and a polypropylene plate (simulating a lid) were heat-sealed under conditions where the thickness of the heat-sealable resin layer was 20% to 80%. These heat-sealing conditions were set so that the ratio of "(thickness of the heat-sealable resin layer at the position where the heat-sealable resin layer is heat-sealed to the lid)/(thickness of the heat-sealable resin layer at the position where the heat-sealable resin layer is not heat-sealed to the lid)" was 20 to 80%. Specifically, the electric storage device exterior material was cut into a rectangular shape measuring 360 mm MD x 160 mm TD. A rectangular (100 mm long x 30 mm wide x 5 mm thick) polypropylene lid (polypropylene plate) was prepared as the lid of the exterior material. Furthermore, a rectangular (140 mm long x 98 mm wide x 28 mm thick) aluminum block was prepared as a simulated electrode body. Next, as shown in the schematic diagram of FIG. 1 , lids are placed on both sides of the electrode assembly in the longitudinal direction, and this is wrapped in an electrical storage device exterior material. The position where the heat-sealable resin layers of the electrical storage device exterior material face each other (first sealing portion 70) and the position where the heat-sealable resin layer of the electrical storage device exterior material and the lid come into contact (second sealing portion 80) are each heat-sealed using a heat seal bar to obtain a simulated electrical storage device. The simulated electrical storage device does not have electrode terminals like those shown in FIG. 1 . The seal width at the position where the heat-sealable resin layers of the electrical storage device exterior material face each other (first sealing portion 70) is 10 mm. The seal width at the position where the heat-sealable resin layer of the electrical storage device exterior material and the lid come into contact (second sealing portion 80) is the thickness of the lid (10 mm). The heat sealing conditions (temperature, surface pressure, and time) for the second sealing portion 80 are set so that the thickness of the heat-sealable resin layer is reduced by 20% or more and 80% or less. Next, for the barrier layer of the obtained simulated electricity storage device, the barrier layer is obtained at the position (sealing portion (second sealing portion)) where the heat-sealable resin layer of the exterior material for an electricity storage device is heat-sealed to the polypropylene plate (polypropylene lid), and crystal analysis is performed using the EBSD method to measure the area-average angle difference of the GOS (crystal grain orientation dispersion) when the grain boundary of the barrier layer is defined as 5°. The specific measurement method is as follows.

Crystal analysis was performed by EBSD on a cross section of each barrier layer perpendicular to the rolling direction, and the area-average angular difference of GOS (grain orientation dispersion) was measured when the grain boundary of the barrier layer was defined as ⁵ °. The detailed measurement conditions are as follows: The area-average angular difference of GOS (grain orientation dispersion) is the area-average angular difference of GOS (grain orientation dispersion) of crystals contained in a measurement area of approximately 5,000 μm2 or more (the entire barrier layer in the thickness direction is the measurement area) obtained by connecting multiple images acquired by crystal analysis by EBSD.

(Measuring device)
A Schottky field emission scanning electron microscope equipped with an EBSD detector is used.

(Pretreatment)
As a pretreatment, the barrier layer is cut in a direction perpendicular to the rolling direction (RD) to obtain a cross section. The rolling direction of the barrier layer is the direction in which linear rolling marks extend when the shiny surface of the barrier layer is observed with a metallurgical microscope. Specifically, the barrier layer to be used as a sample is first cut into a 5 mm (perpendicular to the rolling direction) x 10 mm (rolling direction) piece using a trimming razor, and then embedded in resin. Next, the barrier layer and the resin are cut using the trimming razor in a direction perpendicular to the rolling direction of the barrier layer, perpendicular to the surface of the barrier layer, to expose the cross section of the barrier layer. Next, the obtained cross section is trimmed using a microtome. In this trimming, to reduce mechanical distortion of the cross section shape, the microtome is used to cut the embedded resin and the barrier layer in a direction perpendicular to the cross section by approximately 1 mm. Next, a measurement cross section is prepared by irradiating the cross section with a broad argon beam in a direction perpendicular to the cross section under conditions of a protrusion width of 50 μm, a voltage of 6 kV, and 4 hours. This is a process for precisely exposing the cross section of the barrier layer so as to minimize mechanical damage to the crystal structure that occurred in the previous process. In the present disclosure, the "perpendicular direction" when cutting the aluminum alloy foil is confirmed under a stereomicroscope, and therefore may include an error of about 10°. That is, the permissible range for the direction perpendicular to the rolling direction is 80 to 100° to the rolling direction, and the permissible range for the direction perpendicular to the surface is 80 to 100° with respect to the surface.

(SEM conditions)
The conditions of the scanning electron microscope (SEM) used in the EBSD method are as follows.
Observation magnification: 2000 times (the standard observation magnification when photographing is Polaroid 545)
Acceleration voltage: 15 kV
Working distance: 15mm
Sample tilt angle: 70°

(EBSD conditions)
The conditions for the crystal analysis by the EBSD method are as follows.
Step size: 150 nm
Analysis conditions:
The following analysis is carried out using crystal orientation analysis software OIM (Ver. 7.3) manufactured by TSL Solutions Co., Ltd.
Multiple images are joined together, and the measurement area is approximately 5,000 μm ^or more. The upper limit of the measurement area is, for example, approximately 30,000 μm ^or less. In this case, the measurement area is from the center of the barrier layer in the thickness direction to both ends, and areas where resin is attached to the cross section or where an acid-resistant coating is present are excluded from the measurement area.
The CI value is 0.1 or more, the grain boundary condition is 5° or more, and the minimum grain size is 3 steps or more.
After stitching the images, check the pole figures.
If the center of the pole figure is shifted by 10° or more, rotate the crystal data to ensure symmetry. The pole figure used as a reference is measured from the sample surface using XRD. When obtaining a pole figure from the surface using EBSD, the sample surface is mechanically polished, flat-milled, electrolytically polished, etc., before a wide-area measurement is performed to remove the influence of the mechanical crystal structure of the sample surface. The pole figure obtained from the surface direction is then rotated 90° so that it is the same as the pole figure obtained from the same orientation as the pole figure obtained from the cross section of the target sample. This pole figure is used as a reference.
The analysis is performed by excluding data with a CI value of 0.1 or less, which is defined by the crystal orientation analysis software OIM (Ver. 7.3) manufactured by TSL Solutions Co., Ltd. This makes it possible to exclude data based on the resin used in pretreatment present on the front and back of the sample, grain boundaries present on the cross section, and amorphous matter.

The area-average angular difference of the GOS (grain orientation dispersion) of the barrier layer 3 can be adjusted by the material constituting the barrier layer 3, the thickness of the barrier layer 3, etc.

For example, by increasing the Young's modulus of the barrier layer 3 (i.e., by increasing the Young's modulus of the electrical storage device packaging material 50), the area-average angular difference of the GOS (crystal grain orientation dispersion) of the barrier layer 3 can be reduced. The preferred Young's modulus of the barrier layer 3 will be described later. For example, increasing the thickness of the barrier layer 3 or using a high-strength metal is effective.

For example, if the barrier layer 3 is made of aluminum alloy foil, and the aluminum alloy composition is in the 8000 series of the JIS standard, the strength can be increased by adding a small amount of Si to the aluminum base metal. Furthermore, if the aluminum alloy composition is in the 5000 series of the JIS standard, the strength of the soft foil can be increased by solid solution strengthening by dissolving Mg in the aluminum.

Refining the crystal grains of the metal forming the barrier layer 3 is also effective in increasing the ratio (R1/R2). For example, in the case of aluminum alloy compositions in the JIS 8000 and 5000 series, Al-Fe intermetallic compounds crystallize during casting, which then act as nuclei for grain refinement. Furthermore, when differential speed rolling (a method of rolling using rolls with different peripheral speeds) is employed, the rolled material undergoes shear deformation throughout the entire thickness in addition to the normal rolling deformation. This promotes crystal rotation and promotes the transformation of subgrain boundaries into high-angle grain boundaries, resulting in the formation of fine crystal grains. While this method is also effective in cold rolling, warm rolling is more effective. Furthermore, increasing the number of rolling passes in the hot rolling of aluminum alloy foil and increasing the final cold rolling reduction are also effective. The higher the final cold rolling reduction from the intermediate annealing to the final thickness (e.g., 80% or higher), the greater the amount of strain accumulated in the aluminum alloy foil, resulting in finer recrystallized grains after final annealing.

The rolling conditions for aluminum foil are adjusted by adjusting the rolling reduction, heating temperature, heating time, and other conditions. Examples of methods include a homogenization process for aluminum metal or aluminum alloy ingots at approximately 500-600°C for approximately 1-2 hours, a hot rolling process, a cold rolling process, an intermediate annealing process in which the ingot is held at approximately 300-450°C for approximately 1-10 hours, a cold rolling process in which the rolling reduction from the intermediate annealing to the final rolling is 80% or more, preferably 90% or more, and a final annealing process in which the ingot is held at approximately 250-400°C for approximately 30-100 hours, but the conditions for refining the crystal grains are not limited to these.

<3-3. Manufacturing method of exterior material for electricity storage device>
As described above, the exterior packaging material 50 for an electricity storage device according to the present disclosure corresponds to the exterior packaging film 50, and therefore the manufacturing method is also common to both, and therefore a description thereof will be omitted.

<3-4. Uses of exterior materials for electricity storage devices>
The exterior material for an electricity storage device according to the present disclosure is used in a package for hermetically housing an electricity storage device element such as a positive electrode, a negative electrode, and an electrolyte. That is, an electricity storage device can be formed by housing an electricity storage device element including at least a positive electrode, a negative electrode, and an electrolyte in a package formed from the exterior material for an electricity storage device according to the present disclosure. In other words, an electricity storage device can be formed by wrapping an electricity storage device element in the exterior material for an electricity storage device according to the present disclosure.

For example, an electricity storage device using the electricity storage device packaging material of the present disclosure can be provided by covering an electricity storage device element including at least a positive electrode, a negative electrode, and an electrolyte with the electricity storage device packaging material of the present disclosure, with metal terminals connected to the positive electrode and negative electrode protruding outward, so that a flange portion (a region where the heat-sealable resin layers contact each other) is formed around the periphery of the electricity storage device element, and then heat-sealing the heat-sealable resin layers of the flange portion to provide a hermetic seal. When an electricity storage device element is housed in a package formed from the electricity storage device packaging material of the present disclosure, the package is formed so that the heat-sealable resin portion of the electricity storage device packaging material of the present disclosure faces inward (the surface that contacts the electricity storage device element). A package may be formed by overlapping two electrical storage device packaging materials with their heat-sealable resin layers facing each other and heat-sealing the peripheral edges of the overlapped electrical storage device packaging materials. Alternatively, as shown in the example of FIG. 9, a package may be formed by folding one electrical storage device packaging material over and overlapping the materials and heat-sealing the peripheral edges. When folding and overlapping the materials, the packaging may be formed by heat-sealing the edges other than the folded edge to form a three-sided seal, as shown in the example of FIG. 9, or by folding the material over so as to form a flange and sealing all four sides. Note that when the innermost and outermost layers of the electrical storage device packaging material are heat-sealable resin layers, the packaging may be formed by heat-sealing the innermost heat-sealable resin layer and the outermost heat-sealable resin layer. In addition to an embodiment in which the opposing surfaces of the electrical storage device packaging materials are heat-sealed, an embodiment in which the outer and inner surfaces of the electrical storage device packaging material are heat-sealed is also preferred.

In addition, a recess for accommodating an electricity storage device element may be formed in the electricity storage device exterior material by deep drawing or stretch forming. As shown in the example in Figure 9, a recess may be formed in one electricity storage device exterior material and no recess may be formed in the other electricity storage device exterior material, or a recess may also be formed in the other electricity storage device exterior material.

The exterior material for an electricity storage device disclosed herein suppresses cracking at the sealing portion of the exterior material for an electricity storage device with the lid, even when the electricity storage device is repeatedly exposed to high and low temperature changes, in an electricity storage device that uses an exterior material including an exterior material for an electricity storage device that encases an electrode assembly and a lid. Therefore, the electricity storage device element may be sealed with the lid in addition to the exterior material for an electricity storage device. That is, the exterior material for an electricity storage device and the lid constitute an exterior (exterior material for an electricity storage device) that seals the electricity storage device element. For example, the electricity storage device element may be housed inside a cylindrical exterior material for an electricity storage device, and the opening may be closed with the lid. In another example, the electricity storage device element connected to the lid may be housed inside a cylindrical exterior material for an electricity storage device that has an opening, and the opening may be closed with the lid. The lid and the exterior material for an electricity storage device are preferably joined by any means. From the viewpoint of reducing the dead space between the electricity storage device element and the electricity storage device exterior material in order to improve the volumetric energy density of the electricity storage device, the electricity storage device exterior material is preferably wrapped around the electricity storage device element and the lid. When wrapping the electricity storage device exterior material around the electricity storage device element and the lid, only one sheet of the electricity storage device exterior material may be wrapped around the electricity storage device element and the lid, or multiple sheets of the electricity storage device exterior material may be wrapped around the electricity storage device element and the lid.

As mentioned above, the lid body can be formed, for example, from a resin molded product, a metal molded product, an exterior material for an electricity storage device, or a combination of these. In this disclosure, when the lid body is referred to as a resin molded product, this does not include embodiments in which the lid body is composed solely of a film as defined by the JIS (Japanese Industrial Standards) "Packaging Terminology" standard. When the lid body is a metal molded product, the lid body also functions as a metal terminal, so the metal terminal can be omitted. The lid body may be composed of a resin material and a conductive material.

The following provides a specific description of an electricity storage device that includes an electrode assembly and an exterior body that seals the electrode assembly, and the exterior body includes the exterior material for an electricity storage device of the present disclosure that wraps the electrode assembly, and a lid that seals the electrode assembly together with the exterior material for an electricity storage device.

Like FIG. 1, FIG. 10 is a perspective view schematically illustrating the energy storage device 10. FIG. 11 is a cross-sectional view taken along line A-A in FIG. 1. Note that in FIGS. 10 to 12, the arrow z direction (z1 direction and z2 direction) indicates the thickness direction of the energy storage device 10, the arrow x direction (x1 direction and x2 direction) indicates the width direction of the energy storage device 10, and the arrow y direction (y1 direction and y2 direction) indicates the depth direction of the energy storage device 10. The directions indicated by the arrows x, y, and z are the same in the subsequent figures.

As described above, the energy storage device 10 includes an electrode body 20, an electrode terminal 30, and an exterior body 40. The electrode body 20 includes, for example, electrodes (positive and negative electrodes) constituting an energy storage component such as a lithium-ion battery, capacitor, all-solid-state battery, semi-solid battery, quasi-solid battery, polymer battery, all-resin battery, lead-acid battery, nickel-metal hydride battery, nickel-cadmium battery, nickel-iron battery, nickel-zinc battery, silver oxide-zinc battery, metal-air battery, polyvalent cation battery, or capacitor, as well as a separator. In this disclosure, the shape of the electrode body 20 is, for example, an approximately rectangular parallelepiped. Note that "approximately rectangular parallelepiped" includes not only a perfect rectangular parallelepiped, but also a solid that can be considered a rectangular parallelepiped by modifying the shape of a portion of its outer surface, for example. The shape of the electrode body 20 may be, for example, a cylinder or polygonal prism.

As in Figures 1 and 2, the energy storage device 10 in Figures 10 and 11 has two electrode terminals 30. The electrode terminals 30 are metal terminals used for inputting and outputting power to and from the electrode body 20. One end of the electrode terminal 30 is electrically connected to an electrode (positive or negative) included in the electrode body 20. The other end of the electrode terminal 30 protrudes outward from, for example, the edge of the exterior body 40. Note that the electrode terminal 30 only needs to be able to input and output power to and from the electrode body 20, and does not, for example, need not protrude from the exterior body 40. For example, if the lid body 60 described below is made of a conductive material, the lid body 60 may also function as the electrode terminal 30. In this case, the lid body 60, which functions as an electrode terminal, may or may not protrude from the exterior body 40.

As mentioned above, the metal material that constitutes the electrode terminal 30 is, for example, aluminum, nickel, or copper. For example, if the electrode body 20 is a lithium-ion battery, the electrode terminal 30 connected to the positive electrode is typically made of aluminum, and the electrode terminal 30 connected to the negative electrode is typically made of copper, nickel, or the like. Note that the outermost layer of the electrode body 20 does not necessarily have to be an electrode, and may be, for example, a protective tape or a separator. The outer shape of the electrode body 20 is, for example, a rectangular parallelepiped.

As described above, the exterior body 40 seals the electrode body 20. The exterior body 40 includes an exterior material for an electricity storage device 50 and a lid body 60. The exterior material for an electricity storage device 50 encases the electrode body 20. As in Figures 1 and 2, in Figures 10 and 11, the exterior material for an electricity storage device 50 is wrapped around the electrode body 20. The lid body 60 is disposed on the side of the electrode body 20 in the y direction. In another example, the electrode body 20 may be housed inside a cylindrical exterior material for an electricity storage device 50 with openings at both ends in the y direction, and the openings may be closed by the lid body 60. In yet another example, the electrode body 20 connected to the lid body 60 may be housed inside a cylindrical exterior material for an electricity storage device 50 with openings, and the openings may be closed by the lid body 60.

As described above, the exterior body 40 has a pair of main surfaces and a pair of side surfaces formed by the exterior body material 50 for an electricity storage device. As in Figures 1 and 2, in Figures 10 and 11, the pair of main surfaces are substantially the same size. Furthermore, the pair of side surfaces are substantially the same size. The pair of main surfaces each have a larger area than the pair of side surfaces. The pair of lid bodies 60 are respectively disposed on the sides of the electrode body 20 so as to close the pair of openings. Note that in the present disclosure, the main surfaces and side surfaces refer to the surfaces of the exterior body 40 excluding the lid bodies 60.

As mentioned above, one method is to form a storage portion (recess) in the electrical storage device exterior material 50 through cold forming to accommodate the electrode assembly 20. However, forming a deep storage portion using this method is not necessarily easy. Attempting to form a deep storage portion (recess) using cold forming (e.g., a forming depth of 15 mm) increases the likelihood of pinholes or cracks occurring in the electrical storage device exterior material 50, resulting in a decrease in battery performance. On the other hand, the exterior material 40 seals the electrode assembly 20 by wrapping the electrical storage device exterior material 50 around the electrode assembly 20, making it easy to seal the electrode assembly 20 regardless of the thickness of the electrode assembly 20. Note that in order to reduce the dead space between the electrode assembly 20 and the electrical storage device exterior material 50 and thereby improve the volumetric energy density of the electrical storage device 10, it is preferable for the electrical storage device exterior material 50 to be wrapped in contact with the outer surface of the electrode assembly 20. Furthermore, in all-solid-state batteries, it is necessary to apply high pressure uniformly from the outer surface of the battery to maximize battery performance, and therefore it is necessary to eliminate the space between the electrode body 20 and the electrical storage device exterior material 50. Therefore, it is preferable that the electrical storage device exterior material 50 be wrapped around the outer surface of the electrode body 20 so that it is in contact with the outer surface of the electrode body 20.

The electrical storage device packaging material 50 is a laminate (laminate film) having at least a barrier layer 3 and a heat-sealable resin layer 4. Details of each layer included in the electrical storage device packaging material 50 are as described above.

As mentioned above, the lid body 60 may have any shape, such as a cylinder, prism, rectangular parallelepiped, or cube, and is made up of, for example, a resin material. Here, "made up of a resin material" means that, when the entire material making up the lid body 60 is taken as 100% by mass, the resin material content is 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. In other words, the material making up the lid body 60 can contain materials other than resin materials in addition to resin materials.

Specific examples of resins used in the lid body 60 are as described above.

As mentioned above, the resin used as the resin material may contain a filler as needed. Specific examples of fillers are as described above.

As mentioned above, the melt mass flow rate (measured at 230°C) of the resin material contained in the material constituting the lid 60 is preferably in the range of 1g/10min to 100g/10min, preferably in the range of 1g/10min to 80g/10min, preferably in the range of 1g/10min to 60g/10min, preferably in the range of 5g/10min to 100g/10min, preferably in the range of 5g/10min to 80g/10min, and even more preferably in the range of 5g/10min to 60g/10min. The melt mass flow rate is measured in accordance with JIS K7210-1:2014.

As mentioned above, the lid body 60 may be composed of a conductive material. "Composed of a conductive material" means that, when the entire material constituting the lid body 60 is taken as 100% by mass, the content of the conductive material is 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. In other words, the material constituting the lid body 60 can contain materials other than the conductive material in addition to the conductive material.

As described above, the conductive material that makes up the lid body 60 is, for example, a metal material. The metal material that makes up the lid body 60 is, for example, aluminum, an aluminum alloy, nickel, copper, or a copper alloy. For example, if the electrode body 20 is a lithium-ion battery, the lid body 60 connected to the positive electrode is preferably made of aluminum or an aluminum alloy. The lid body 60 connected to the negative electrode is preferably made of nickel, copper, or a copper alloy. The material that makes up the lid body 60 connected to the negative electrode may be nickel-plated copper. The material that makes up the lid body 60 may include recycled metal materials. When the lid body 60 is made up of a conductive material, the lid body 60 also functions as the electrode terminal 30, so the electrode terminal 30 can be omitted from the electricity storage device 10.

As described above, the lid body 60 may be configured such that at least a portion of the lid main body 61 is covered with the covering body 62. In the lid body 60 of FIG. 12, the periphery of the lid main body 61 (the periphery of the thickness portion) is covered with the covering body 62. The lid body 60 may be joined to the thermally adhesive resin layer 4 of the electrical storage device exterior material 50 via the covering body 62. The covering body 62 preferably contains a resin material. The lid body 60 has the lid main body 61 and the covering body 62 that joins the lid main body 61 and the electrical storage device exterior material 50, and the covering body 62 can be configured to contain a resin (resin material). The definition of "containing a resin material" with respect to the covering body 62 is the same as for the lid body 60.

As described above, when the lid body 60 is made of a conductive material, the lid main body 61 may be made of a conductive material, and at least a portion of the lid main body 61 may be covered by the covering body 62.

As described above, when the lid 60 contains a conductive material, the lid 60 may be bonded to the electrical storage device exterior packaging material 50 via an adhesive film instead of a covering. Any adhesive film can be selected as long as it can bond the electrical storage device exterior packaging material 50 and the lid 60. The adhesive film is preferably a laminated film having at least a heat-sealable resin layer, a heat-resistant substrate layer, and a heat-sealable resin layer, in this order. The specifications for the heat-sealable resin layer of the adhesive film are the same as those for the heat-sealable resin layer 4. The materials constituting the heat-sealable resin layers on both sides of the adhesive film may be the same or different, and are selected appropriately depending on the materials constituting the heat-sealable resin layer 4 of the electrical storage device exterior packaging material 50 and the materials constituting the lid 60. The material constituting the heat-sealable resin layer of the adhesive film on the side bonded to the lid 60 is preferably an acid-modified polyolefin resin graft-modified with an acid such as maleic anhydride. The heat-sealable resin layer of the adhesive film on the side that is bonded to the electrical storage device packaging material 50 is preferably made of the same type of material as the material that constitutes the heat-sealable resin layer 4 of the electrical storage device packaging material 50.

As mentioned above, the heat-resistant substrate layer may be any film made of a heat-resistant resin, such as polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polymethylpentene (registered trademark), polyacetal cyclic polyolefin, polyethylene, or polypropylene, and may be an unstretched or stretched film. Polyethylene terephthalate is particularly preferred as it is inexpensive and has high strength.

As mentioned above, the adhesive film preferably has adhesive properties. When the second sealing portion 80 (described below) is formed with the adhesive film disposed between the electrical storage device exterior material 50 and the lid 60, the adhesive film is less likely to shift position relative to the lid 60 and the electrical storage device exterior material 50. Adhesion can be imparted to the adhesive film by incorporating a tackifying resin into the heat-sealable resin layer of the adhesive film. Examples of tackifying resins include amorphous polyolefins. Examples of amorphous polyolefins include amorphous polypropylene and copolymers of amorphous propylene and other α-olefins. The content of the tackifying resin relative to the base material constituting the heat-sealable resin is preferably 10 to 20% by weight or less.

As described above, the lid body 60 has a first main surface located on the inside of the electricity storage device (the electrode body 20 side), a second main surface located on the outside of the electricity storage device, and four side surfaces that are heat-sealed to the heat-sealable resin layer 4 of the exterior material for an electricity storage device 50. The first main surface faces the electrode body 20. The second main surface is the surface opposite the first main surface.

As described above, when the lid body 60 is a cylinder, prism, rectangular parallelepiped, cube, or the like, it is preferable that the lid body 60 have a certain thickness in the thickness direction (y direction) so that deformation of the exterior body 40 is suppressed even when the energy storage device 10 is stacked. From another perspective, when the lid body 60 is a cylinder, prism, rectangular parallelepiped, cube, or the like, it is preferable that the lid body 60 have a certain thickness in the thickness direction (y direction) so that the lid joint of the lid body 60 can be suitably joined to the exterior film 50 when forming the second sealing portion 80. The minimum value of the thickness of the lid body 60 in the thickness direction (y direction) (the distance in the y direction between the first main surface and the second main surface) is, for example, 1.0 mm, more preferably 3.0 mm, and even more preferably 4.0 mm. The maximum thickness of the lid 60 in the y direction is, for example, 20 mm, preferably 15.0 mm, more preferably 10.0 mm, even more preferably 8.0 mm, and even more preferably 7.0 mm. The maximum thickness of the lid 60 in the y direction may be 10 mm or more. Preferred ranges for the thickness of the material constituting the lid 60 are 1.0 mm to 20.0 mm, 1.0 mm to 15.0 mm, 1.0 mm to 10.0 mm, 1.0 mm to 8.0 mm, 1.0 mm to 7.0 mm, 3.0 mm to 20.0 mm, 3.0 mm to 15.0 mm, 3.0 mm to 10.0 mm, 3.0 mm to 8.0 mm, 3.0 mm to 7.0 mm, 4.0 mm to 20.0 mm, 4.0 mm to 15.0 mm, 4.0 mm to 10.0 mm, 4.0 mm to 8.0 mm, and 4.0 mm to 7.0 mm. In this disclosure, when the lid body 60 is described as a cylinder, prism, rectangular parallelepiped, cube, or the like, this does not include embodiments in which the lid body 60 is made solely of a film as defined by the JIS (Japanese Industrial Standards) [Packaging Terminology] standard. The thickness of the lid body 60 may vary depending on the part of the lid body 60. When the thickness of the lid body 60 varies depending on the part, the thickness of the lid body 60 is the thickness of the thickest part.

1 and 2, in Figures 10 and 11, the lid body 60 has a through-hole formed therein through which the electrode terminal 30 is inserted. The through-hole penetrates the first and second main surfaces of the lid body. When the electrode body 20 is stored, the electrode terminal 30 passes through the through-hole formed in the lid body 60 and protrudes to the outside of the exterior body 40. The small gap between the through-hole in the lid body 60 and the electrode terminal 30 is filled, for example, with resin. Note that the position from which the electrode terminal 30 protrudes to the outside of the energy storage device 10 can be selected arbitrarily. For example, the electrode terminal 30 may protrude to the outside from a hole formed on any of the six surfaces of the exterior body 40. In this case, the small gap between the exterior body 40 and the electrode terminal 30 is filled, for example, with resin. The electrode terminal 30 may protrude from between the lid body 60 and the exterior material 50 for an energy storage device, or from the first sealing portion 70 described below. In the electricity storage device 10, the lid body 60 and the electrode terminal 30 are provided as separate bodies, but the lid body 60 and the electrode terminal 30 may also be formed integrally. Note that if the electrode terminal 30 does not protrude from the edge of the exterior body 40, the lid body 60 does not need to have a through-hole formed therein.

As in Figures 1 and 2, in Figures 10 and 11, the electrical storage device exterior material 50 is wrapped around the electrode body 20, and the facing surfaces (thermally adhesive resin layers 4) of the electrical storage device exterior material 50 are heat-sealed to form the first sealing portion 70.

As described above, the first sealing portion 70 is formed by heat-sealing the heat-fusible resin layers of the exterior material 50 for an electricity storage device. The first sealing portion 70 extends in the longitudinal direction of the exterior body 40. The position at which the first sealing portion 70 is formed on the exterior body 40 can be selected arbitrarily. As in FIG. 1, as shown in FIG. 10, the base of the first sealing portion 70 is preferably located on the boundary between the main surface and the side surface of the exterior body 40. The base of the first sealing portion 70 may be located on any surface of the exterior body 40. As in FIG. 1, in FIG. 10, the first sealing portion 70 protrudes outward beyond the electrode body 20 in a plan view. The first sealing portion 70 may be folded, for example, toward the side surface of the exterior body 40 or toward the main surface.

As described above, the second sealing portion 80 is formed by joining the heat-sealable resin layer 4 of the electrical storage device exterior material 50 and the lid joint portion of the lid body 60 (the portion where the heat-sealable resin layer 4 of the electrical storage device exterior material 50 and the lid body 60 come into contact) by, for example, heat sealing. The electrical storage device exterior material 50 and the lid body 60 can be joined by any method, such as welding.

The exterior material for an electricity storage device of the present disclosure can be suitably used in electricity storage devices such as batteries (including condensers, capacitors, etc.). The exterior material for an electricity storage device of the present disclosure may be used in either primary or secondary batteries, but is preferably used in secondary batteries. The type of secondary battery to which the exterior material for an electricity storage device of the present disclosure can be applied is not particularly limited, and examples include lithium ion batteries, lithium ion polymer batteries, all-solid-state batteries, semi-solid batteries, quasi-solid batteries, polymer batteries, all-resin batteries, lead-acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, silver oxide-zinc batteries, metal-air batteries, polyvalent cation batteries, condensers, and capacitors. Among these secondary batteries, lithium ion batteries and lithium ion polymer batteries are suitable applications for the exterior material for an electricity storage device of the present disclosure.

The present disclosure will be explained in detail below using examples and comparative examples. However, the present disclosure is not limited to the examples.

<Method of manufacturing exterior film>
Comparative Example 1A
A laminate was prepared as the substrate layer, consisting of a biaxially oriented polyethylene terephthalate (PET) film (12 μm thick) and an oriented nylon (ONy) film (15 μm thick) bonded together with an adhesive layer (formed with a two-component curing urethane adhesive, with a cured thickness of 3 μm). Furthermore, an aluminum foil (JIS H4160:1994 A8079H-O (thickness 40 μm)) was prepared as the barrier layer. Both sides of the aluminum foil were subjected to a chemical conversion treatment. The chemical conversion treatment of the aluminum foil was performed by applying a treatment solution consisting of a phenolic resin, a chromium fluoride compound, and phosphoric acid to both sides of the aluminum foil by roll coating so that the coating amount of chromium was 10 mg/ ^m2 (dry mass), followed by baking.

Next, a two-component curing urethane adhesive was used to adhere the base layer and barrier layer to an adhesive layer (3 μm thick) using the dry lamination method, producing a laminate in which the base layer/adhesive layer/barrier layer were laminated in that order.

Next, maleic anhydride-modified polypropylene, which forms an adhesive layer (40 μm thick), and random polypropylene, which forms a heat-sealable resin layer (40 μm thick), were co-extruded onto the barrier layer of each of the laminates obtained above, thereby laminating the adhesive layer/heat-sealable resin layer on top of the barrier layer. The resulting laminate was then aged and heated to obtain an exterior film consisting of a laminate in which the substrate layer/adhesive layer/barrier layer/adhesive layer/heat-sealable resin layer were laminated in this order.

Comparative example 2A
An exterior film consisting of a laminate in which a base layer/adhesive layer/barrier layer/adhesive layer/thermally adhesive resin layer were laminated in this order was obtained in the same manner as in Comparative Example 1A, except that aluminum foil (JIS H4160:1994 A8079H-O (thickness 60 μm)) was used as the barrier layer.

Example 1A
An exterior film consisting of a laminate in which a base layer/adhesive layer/barrier layer/adhesive layer/thermally adhesive resin layer were laminated in this order was obtained in the same manner as in Comparative Example 1A, except that aluminum foil (JIS H4160:1994 A8079H-O (thickness: 80 μm)) was used as the barrier layer.

Example 2A
An exterior film consisting of a laminate in which a base layer/adhesive layer/barrier layer/adhesive layer/thermally adhesive resin layer were laminated in this order was obtained in the same manner as in Comparative Example 1A, except that a stainless steel foil (JIS G4303 SUS304 (thickness 60 μm)) was used as the barrier layer.

Example 3A
The exterior film used was the same as that used in Comparative Example 1 A. In the thermal shock test described below, the material of the lid of the exterior body used for the simulated electricity storage device was different from that used in Comparative Example 1 A.

Example 4A
The exterior film used was the same as that used in Comparative Example 1 A. In the thermal shock test described below, the material of the lid of the exterior body used for the simulated electricity storage device was different from that of Comparative Example 1 A and Example 3A.

<Measurement of area average angle difference of GOS (grain orientation dispersion) of barrier layer>
A simulated electricity storage device was manufactured in the same manner as the simulated electricity storage device manufactured in the <Thermal Shock Test> described below. Next, for the simulated electricity storage device, the barrier layer was obtained at the position where the heat-sealable resin layer of the exterior film was heat-sealed to the lid (sealing portion (second sealing portion)), and crystal analysis was performed using the EBSD method to measure the area-average angle difference of GOS (crystal grain orientation dispersion) when the grain boundary of the barrier layer was defined as 5°. The specific measurement method is as follows.

Crystal analysis was performed by EBSD on a cross section of each barrier layer perpendicular to the rolling direction, and the area-average angular difference of GOS (grain orientation dispersion) was measured when the grain boundary of the barrier layer was defined as 5°. Details of the measurement conditions are as follows. The measurement results are shown in Table 1A. The area-average angular difference of GOS (grain orientation dispersion) is the area-average angular difference of GOS (grain orientation dispersion) of crystals contained in a measurement area of approximately 5,000 ^μm2 or more (the entire barrier layer in the thickness direction is the measurement area) obtained by connecting multiple images obtained by crystal analysis by EBSD.

(Measuring device)
The apparatus used was a Schottky field emission scanning electron microscope equipped with an EBSD detector (manufactured by TSL Solutions Co., Ltd.).

(Pretreatment)
As a pretreatment, the barrier layer was cut in a direction perpendicular to the rolling direction (RD) to obtain a cross section. The rolling direction of the barrier layer was determined by observing the shiny surface of the barrier layer with a metallurgical microscope, and the direction of linear rolling marks was the direction in which these marks extended. Specifically, the barrier layer sample was first cut into a 5 mm (perpendicular to the rolling direction) x 10 mm (rolling direction) piece using a trimming razor, and then embedded in resin. Next, the barrier layer was cut together with the resin using the trimming razor in a direction perpendicular to the rolling direction of the barrier layer, perpendicular to the surface of the barrier layer, to expose the cross section of the barrier layer. Next, the obtained cross section was trimmed using a microtome (an ultramicrotome manufactured by Leica Microsystems). In this trimming, the microtome was used to cut the embedded resin along with the barrier layer in a direction perpendicular to the cross section by approximately 1 mm to reduce mechanical distortion in the cross section. Next, a broad argon beam was irradiated perpendicularly to the cross section using an ion milling device (manufactured by Hitachi High-Technologies Corporation) under conditions of a protrusion width of 50 μm, a voltage of 6 kV, and 4 hours to prepare a cross section for measurement. This is a process for precisely exposing the cross section of the barrier layer so as to minimize mechanical damage to the crystal structure that occurred in the previous process. In this disclosure, the "perpendicular direction" when cutting the aluminum alloy foil is confirmed under a stereomicroscope, and therefore may include an error of about 10°. In other words, the permissible range for the direction perpendicular to the rolling direction is 80 to 100° to the rolling direction, and the permissible range for the direction perpendicular to the surface is 80 to 100° relative to the surface.

(SEM conditions)
The conditions of the scanning electron microscope (SEM) used in the EBSD method are as follows.
Observation magnification: 2000 times (the standard observation magnification when photographing is Polaroid 545)
Acceleration voltage: 15 kV
Working distance: 15mm
Sample tilt angle: 70°

(EBSD conditions)
The conditions for the crystal analysis by the EBSD method are as follows.
Step size: 150 nm
Analysis conditions:
The following analysis was carried out using crystal orientation analysis software OIM (Ver. 7.3) manufactured by TSL Solutions Co., Ltd.
Multiple images were joined together to set the measurement area to approximately 5000 ^μm2 or more. The measurement area was set from the center of the barrier layer in the thickness direction to both ends, and areas where resin was attached to the cross section and areas where the acid-resistant coating was present were excluded from the measurement area.
The CI value was set to 0.1 or more, the grain boundary condition was set to 5° or more, and the minimum grain size was set to 3 steps or more.
After stitching the images together, the pole figures were checked.
If the center of the pole figure is shifted by 10° or more, rotate the crystal data to ensure symmetry. The pole figure used as a reference is measured from the sample surface using XRD. When obtaining a pole figure from the surface using EBSD, the sample surface is mechanically polished, flat-milled, electrolytically polished, etc., before a wide-area measurement is performed to remove the influence of the mechanical crystal structure of the sample surface. The pole figure obtained from the surface direction is then rotated 90° so that it is the same as the pole figure obtained from the same orientation as the pole figure obtained from the cross section of the target sample. This pole figure is used as a reference.
The analysis was performed by excluding data with a CI value of 0.1 or less, which is defined by the crystal orientation analysis software OIM (Ver. 7.3) manufactured by TSL Solutions Co., Ltd. This allows us to eliminate data based on the resin used in pretreatment present on the front and back of the sample, grain boundaries present on the cross section, and amorphous matter.

<Measurement of Young's modulus of exterior film>
The Young's modulus of the exterior film was measured by the following method, and the results are shown in Table 1A.
In accordance with the provisions of JIS K6251:2017, an S-S curve in the TD direction of the exterior film was obtained under the following measurement conditions, and the Young's modulus (MPa) was calculated from the maximum value of the slope of the S-S curve.
(Measurement conditions)
A tensile tester (Shimadzu Autograph AG-X Plus) is used.
Shape of test piece: Dumbbell No. 7 Width of test piece: 2 mm
Test piece length: 35 mm
Thickness of test piece: measured with a thickness gauge. Gauge distance: 20 mm
Tensile speed: 50 mm/min
Test environment: 23±5°C, 50±30% RH
Number of measurements: Average value of 3 measurements

<Thermal shock test>
The exterior film produced in each Example and Comparative Example was cut into a rectangular shape measuring 360 mm in MD x 160 mm in TD. Meanwhile, in Comparative Examples 1A-2A and 1A-2A, a rectangular parallelepiped (100 mm long x 30 mm wide x 5 mm thick) polypropylene lid was prepared as the lid for the exterior body. In Example 3A, a rectangular parallelepiped (98 mm long x 28 mm wide x 5 mm thick) aluminum lid body was prepared, the periphery (periphery of the thick portion) of which was covered with a polypropylene (PP) covering body (100 mm long x 30 mm wide x 5 mm thick). In Example 4A, a rectangular parallelepiped (98 mm long x 28 mm wide x 5 mm thick) aluminum lid body was prepared, the periphery (periphery of the thick portion) of which was covered with a maleic anhydride-modified polypropylene (PPa) covering body (100 mm long x 30 mm wide x 5 mm thick). Furthermore, a rectangular parallelepiped (length 140 mm x width 98 mm x thickness 28 mm) aluminum block was prepared as a simulated electrode body.

Next, as shown in the schematic diagram of Figure 1, lids were placed on both longitudinal sides of the electrode assembly, which were then wrapped in an exterior film. The location where the heat-sealable resin layers of the exterior film faced each other (first sealing portion 70) and the location where the heat-sealable resin layer of the exterior film and the lid came into contact (second sealing portion 80) were heat-sealed using a heat seal bar, respectively, to obtain a simulated energy storage device. The simulated energy storage device did not have electrode terminals like those shown in Figure 1. The seal width at the location where the heat-sealable resin layers of the exterior film faced each other (first sealing portion 70) was 10 mm. The seal width at the location where the heat-sealable resin layer of the exterior film and the lid came into contact (second sealing portion 80) was the thickness of the lid (5 mm). The heat-sealing conditions (temperature, surface pressure, and time) for the second sealing portion 80 were 180°C, 0.60 MPa, and 3 seconds for Comparative Example 1A, 180°C, 1.20 MPa, and 5 seconds for Comparative Example 2A and Examples 1A-3A, and 180°C, 0.60 MPa, and 7 seconds for Example 4A. In all cases, the conditions were set so that the ratio of "(thickness of the heat-sealable resin layer at the position where the heat-sealable resin layer is heat-sealed to the lid)/(thickness of the heat-sealable resin layer at the position where the heat-sealable resin layer is not heat-sealed to the lid)" was 10 to 90%. The conditions for achieving a thickness of the heat-sealable resin layer of 20% to 80% can be adjusted, for example, by setting the heat-sealing temperature to approximately 160 to 240°C, the surface pressure to approximately 0.2 to 1.5 MPa, and the heat-sealing time to approximately 1 to 12 seconds.

The simulated energy storage devices obtained were each subjected to a thermal shock test in which one cycle consisted of leaving the device in a -30°C environment for 30 minutes, followed by leaving the device in an 80°C environment for 30 minutes. This cycle was repeated 800 times to evaluate whether the occurrence of cracks in the sealing portion between the exterior film and the lid (the surface layer of the exterior film) was suppressed when the energy storage device was repeatedly exposed to high and low temperature changes. The results are shown in Table 1A.

In the thermal shock test results shown in Table 1A, the energy storage devices of Comparative Examples 1A-2A had cracks at the sealing portion of the exterior film with the lid. On the other hand, the energy storage device of Example 1A had fine cracks at the sealing portion of the exterior film with the lid, but it could be evaluated that the occurrence of cracks at the sealing portion of the exterior film with the lid was suppressed. The energy storage devices of Examples 2A-4A had no cracks at the sealing portion of the exterior film with the lid, and it could be evaluated that the occurrence of cracks at the sealing portion of the exterior film with the lid was particularly well suppressed. Fine cracks are cracks that do not reveal voids in the barrier layer when the sealing portion is observed with an SEM. In contrast, the cracks observed in Comparative Examples 1A-2A were cracks that revealed voids in the barrier layer when the sealing portion was observed with an SEM. The conditions for SEM observation were: magnification: 1000x, accelerating voltage: 5 kV, and working distance: 10 mm.

In Table 1A, PET is a polyethylene terephthalate film, DL is an adhesive layer formed by the dry lamination method, ONy is an oriented nylon film, AL is an aluminum alloy foil, SUS is a stainless steel foil, PPa is a maleic anhydride-modified polypropylene layer, and PP is a polypropylene layer. The Young's modulus and area-average angular difference of GOS (grain orientation dispersion) were calculated by rounding off the measured values that were one digit smaller than the values listed in Table 1A.

<Manufacturing of exterior materials for electricity storage devices>
Comparative example 1B
A laminate was prepared as the substrate layer, consisting of a biaxially oriented polyethylene terephthalate (PET) film (12 μm thick) and an oriented nylon (ONy) film (15 μm thick) bonded together with an adhesive layer (formed with a two-component curing urethane adhesive, with a cured thickness of 3 μm). Furthermore, an aluminum foil (JIS H4160:1994 A8079H-O (thickness 60 μm)) was prepared as the barrier layer. Both sides of the aluminum foil were subjected to a chemical conversion treatment. The chemical conversion treatment of the aluminum foil was performed by applying a treatment solution consisting of a phenolic resin, a chromium fluoride compound, and phosphoric acid to both sides of the aluminum foil by roll coating so that the coating amount of chromium was 10 mg/ ^m2 (dry mass), followed by baking.

Next, a two-component curing urethane adhesive was used to adhere the base layer and barrier layer to an adhesive layer (3 μm thick) using the dry lamination method, producing a laminate in which the base layer/adhesive layer/barrier layer were laminated in that order.

Next, maleic anhydride-modified polypropylene, which forms an adhesive layer (40 μm thick), and random polypropylene, which forms a heat-sealable resin layer (40 μm thick), were co-extruded onto the barrier layer of each of the laminates obtained above, thereby laminating the adhesive layer/heat-sealable resin layer on top of the barrier layer. The resulting laminate was then aged and heated to obtain an exterior packaging material for an electricity storage device consisting of a laminate in which the base layer/adhesive layer/barrier layer/adhesive layer/heat-sealable resin layer were laminated in this order.

Example 1B
An exterior packaging material for an electricity storage device comprising a laminate in which a base material layer/adhesive layer/barrier layer/adhesive layer/thermally adhesive resin layer were laminated in this order was obtained in the same manner as in Comparative Example 1B, except that aluminum foil (JIS H4160:1994 A8079H-O (thickness: 80 μm)) was used as the barrier layer.

Example 2B
An exterior packaging material for an electricity storage device comprising a laminate in which a base material layer/an adhesive layer/a barrier layer/an adhesive layer/a heat-fusible resin layer were laminated in this order was obtained in the same manner as in Comparative Example 1B, except that a stainless steel foil (JIS G4303 SUS304 (thickness 60 μm)) was used as the barrier layer.

<Measurement of area average angle difference of GOS (grain orientation dispersion) of barrier layer>
A simulated electricity storage device was manufactured in the same manner as the simulated electricity storage device manufactured in the <Thermal Shock Test> described below. Next, for the simulated electricity storage device, the barrier layer was obtained at the position (sealing portion (second sealing portion)) where the heat-sealable resin layer of the exterior material for an electricity storage device was heat-sealed to the polypropylene plate (polypropylene lid), and crystal analysis was performed using the EBSD method to measure the area-average angle difference of GOS (crystal grain orientation dispersion) when the grain boundary of the barrier layer was defined as 5°. The specific measurement method is as follows.

Crystal analysis was performed by EBSD on a cross section perpendicular to the rolling direction of each barrier layer, and the area-average angular difference of GOS (grain orientation dispersion) was measured when the grain boundary of the barrier layer was defined as 5°. Details of the measurement conditions are as follows. The measurement results are shown in Table 1B. The area-average angular difference of GOS (grain orientation dispersion) is the area-average angular difference of GOS (grain orientation dispersion) of crystals contained in a measurement area of approximately 5,000 ^μm2 or more (the entire barrier layer in the thickness direction is the measurement area) obtained by connecting multiple images obtained by crystal analysis by EBSD.

(Measuring device)
The apparatus used was a Schottky field emission scanning electron microscope equipped with an EBSD detector (manufactured by TSL Solutions Co., Ltd.).

(Pretreatment)
As a pretreatment, the barrier layer was cut in a direction perpendicular to the rolling direction (RD) to obtain a cross section. The rolling direction of the barrier layer was determined by observing the shiny surface of the barrier layer with a metallurgical microscope, and the direction of linear rolling marks was the direction in which these marks extended. Specifically, the barrier layer sample was first cut into a 5 mm (perpendicular to the rolling direction) x 10 mm (rolling direction) piece using a trimming razor, and then embedded in resin. Next, the barrier layer was cut together with the resin using the trimming razor in a direction perpendicular to the rolling direction of the barrier layer, perpendicular to the surface of the barrier layer, to expose the cross section of the barrier layer. Next, the obtained cross section was trimmed using a microtome (an ultramicrotome manufactured by Leica Microsystems). In this trimming, the microtome was used to cut the embedded resin along with the barrier layer in a direction perpendicular to the cross section by approximately 1 mm to reduce mechanical distortion in the cross section. Next, a broad argon beam was irradiated perpendicularly to the cross section using an ion milling device (manufactured by Hitachi High-Technologies Corporation) under conditions of a protrusion width of 50 μm, a voltage of 6 kV, and 4 hours to prepare a cross section for measurement. This is a process for precisely exposing the cross section of the barrier layer so as to minimize mechanical damage to the crystal structure that occurred in the previous process. In this disclosure, the "perpendicular direction" when cutting the aluminum alloy foil is confirmed under a stereomicroscope, and therefore may include an error of about 10°. In other words, the permissible range for the direction perpendicular to the rolling direction is 80 to 100° to the rolling direction, and the permissible range for the direction perpendicular to the surface is 80 to 100° relative to the surface.

(SEM conditions)
The conditions of the scanning electron microscope (SEM) used in the EBSD method are as follows.
Observation magnification: 2000 times (the standard observation magnification when photographing is Polaroid 545)
Acceleration voltage: 15 kV
Working distance: 15mm
Sample tilt angle: 70°

(EBSD conditions)
The conditions for the crystal analysis by the EBSD method are as follows.
Step size: 150 nm
Analysis conditions:
The following analysis was carried out using crystal orientation analysis software OIM (Ver. 7.3) manufactured by TSL Solutions Co., Ltd.
Multiple images were joined together to set the measurement area to approximately 5000 ^μm2 or more. The measurement area was set from the center of the barrier layer in the thickness direction to both ends, and areas where resin was attached to the cross section and areas where the acid-resistant coating was present were excluded from the measurement area.
The CI value was set to 0.1 or more, the grain boundary condition was set to 5° or more, and the minimum grain size was set to 3 steps or more.
After stitching the images together, the pole figures were checked.
If the center of the pole figure is shifted by 10° or more, rotate the crystal data to ensure symmetry. The pole figure used as a reference is measured from the sample surface using XRD. When obtaining a pole figure from the surface using EBSD, the sample surface is mechanically polished, flat-milled, electrolytically polished, etc., before a wide-area measurement is performed to remove the influence of the mechanical crystal structure of the sample surface. The pole figure obtained from the surface direction is then rotated 90° so that it is the same as the pole figure obtained from the same orientation as the pole figure obtained from the cross section of the target sample. This pole figure is used as a reference.
The analysis was performed by excluding data with a CI value of 0.1 or less, which is defined by the crystal orientation analysis software OIM (Ver. 7.3) manufactured by TSL Solutions Co., Ltd. This allows us to eliminate data based on the resin used in pretreatment present on the front and back of the sample, grain boundaries present on the cross section, and amorphous matter.

<Measurement of Young's modulus of exterior material for electricity storage device>
The Young's modulus of the electrical storage device packaging material was measured by the following method, and the results are shown in Table 1B.
In accordance with the provisions of JIS K6251:2017, an S-S curve in the TD direction of the adhesive film was obtained under the following measurement conditions, and the Young's modulus (MPa) was calculated from the maximum value of the slope of the S-S curve.
(Measurement conditions)
A tensile tester (Shimadzu Autograph AG-X Plus) is used.
Shape of test piece: Dumbbell No. 7 Width of test piece: 2 mm
Test piece length: 35 mm
Thickness of test piece: measured with a thickness gauge. Gauge distance: 20 mm
Tensile speed: 50 mm/min
Test environment: 23±5°C, 50±30% RH
Number of measurements: Average value of 3 measurements

<Thermal shock test>
The exterior materials for electrical storage devices manufactured in each Example and Comparative Example were each cut into a rectangular shape with dimensions of 360 mm (MD) x 160 mm (TD). A rectangular parallelepiped (100 mm long x 30 mm wide x 5 mm thick) polypropylene cover (polypropylene plate) was prepared as the cover for the exterior body. Furthermore, a rectangular parallelepiped (140 mm long x 98 mm wide x 28 mm thick) aluminum block was prepared as a simulated electrode body.

Next, as shown in the schematic diagram of Figure 1, lids were placed on both longitudinal sides of the electrode assembly, which were then wrapped in an electrical storage device exterior material. The position where the thermally adhesive resin layers of the electrical storage device exterior material face each other (first sealing portion 70) and the position where the thermally adhesive resin layer of the electrical storage device exterior material and the lid contact each other (second sealing portion 80) were heat-sealed using a heat seal bar, respectively, to obtain a simulated electrical storage device. The simulated electrical storage device did not have electrode terminals like those shown in Figure 1. The seal width at the position where the thermally adhesive resin layers of the electrical storage device exterior material face each other (first sealing portion 70) was 10 mm. The seal width at the position where the thermally adhesive resin layer of the electrical storage device exterior material and the lid contact each other (second sealing portion 80) was the thickness of the lid (5 mm). The heat sealing conditions (temperature, surface pressure, and time) for the second sealing portion 80 were 180°C, 1.20 MPa, and 5 seconds, respectively. These heat sealing conditions were set so that the ratio of "(thickness of the heat-sealable resin layer at the position where it is heat-sealed to the lid)/(thickness of the heat-sealable resin layer at the position where it is not heat-sealed to the lid)" was 20-80%.

The simulated electricity storage devices obtained were each subjected to a thermal shock test in which one cycle consisted of leaving the device in a -30°C environment for 30 minutes, followed by leaving the device in an 80°C environment for 30 minutes. This cycle was repeated 800 times to evaluate whether the occurrence of cracks in the sealing portion between the electricity storage device packaging material and the lid (the surface layer of the electricity storage device packaging material) was suppressed when the electricity storage device was repeatedly exposed to high and low temperature changes. The results are shown in Table 1B.

In the thermal shock test results shown in Table 1B, the energy storage device of Comparative Example 1B had cracks at the sealing portion between the energy storage device exterior material and the lid. On the other hand, the energy storage device of Example 1B had fine cracks at the sealing portion between the energy storage device exterior material and the lid, but it could be evaluated that the occurrence of cracks at the sealing portion between the energy storage device exterior material and the lid was suppressed. The energy storage device of Example 2B had no cracks at the sealing portion between the energy storage device exterior material and the lid, and it could be evaluated that the occurrence of cracks at the sealing portion between the energy storage device exterior material and the lid was particularly well suppressed. Fine cracks are cracks that do not reveal voids in the barrier layer when the sealing portion is observed with an SEM, whereas the cracks observed in Comparative Example 1B were cracks that revealed voids in the barrier layer when the sealing portion was observed with an SEM. The conditions for SEM observation were: magnification: 1000x, acceleration voltage: 5 kV, working distance: 10 mm.

In Table 1B, PET is a polyethylene terephthalate film, DL is an adhesive layer formed by the dry lamination method, ONy is an oriented nylon film, AL is an aluminum alloy foil, SUS is a stainless steel foil, PPa is a maleic anhydride-modified polypropylene layer, and PP is a polypropylene layer. The Young's modulus and area-average angular difference of GOS (grain orientation dispersion) were calculated by rounding off the measured values that were one digit smaller than the values listed in Table 1B.

As described above, the present disclosure provides the following aspects of the invention.
Item 1A. An electricity storage device,
An electrode body;
an exterior body that seals the electrode body,
The exterior body is
an exterior film that wraps the electrode body;
a lid that seals the electrode body together with the exterior film,
the exterior film is composed of a laminate including at least a barrier layer and a heat-sealable resin layer,
the barrier layer has an area-average angular difference of GOS (grain orientation dispersion) of 2.50° or less, where the grain boundary is defined as 5°, obtained by performing crystal analysis by an EBSD method on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position where the heat-sealable resin layer of the packaging film is heat-sealed to the lid;
Energy storage device.
Item 2A. The electricity storage device according to Item 1A, wherein the barrier layer is formed of stainless steel, a steel plate, or an aluminum alloy.
Item 3A. The lid body has a lid main body and a covering body that joins the lid main body and the exterior film,
Item 1A or 2A, the electricity storage device according to Item 1A or 2A, wherein the covering contains a resin.
Item 4A: The electricity storage device according to any one of Items 1A to 3A, further comprising an adhesive layer between the barrier layer and the heat-sealable resin layer.
Item 5A: The electricity storage device according to any one of Items 1A to 4A, further comprising a substrate layer on the side of the barrier layer opposite to the thermally adhesive resin layer side.
Item 6A. The electricity storage device according to Item 5A, further comprising an adhesive layer between the base layer and the barrier layer.
Item 7A: The electricity storage device according to any one of Items 1A to 6A, wherein the exterior film has a Young's modulus of 6000 MPa or more.
Item 8A. A method for manufacturing an electricity storage device,
The electricity storage device is
An electrode body;
an exterior body that seals the electrode body,
The exterior body is
an exterior film that wraps the electrode body;
a lid that seals the electrode body together with the exterior film,
the exterior film is composed of a laminate including at least a barrier layer and a heat-sealable resin layer,
the barrier layer has an area-average angular difference of GOS (grain orientation dispersion) of 2.50° or less, where a grain boundary is defined as 5°, obtained by performing crystal analysis by an EBSD method on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer at a position where the heat-fusible resin layer of the packaging film is heat-fused to the lid, and the area-average angular difference of GOS (grain orientation dispersion) is 2.50° or less, where a grain boundary is defined as 5°;
a step of sealing the electrode body with the outer casing,
A method for manufacturing an electricity storage device.

Furthermore, as described above, the present disclosure provides the following aspects of the invention.
Item 1B. An exterior packaging material for an electricity storage device composed of a laminate including at least a barrier layer and a heat-sealable resin layer,
the barrier layer has an area-average angular difference of GOS (grain orientation dispersion) of 2.50° or less, when a grain boundary is defined as 5°, obtained by performing crystal analysis by an EBSD method on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer, at a position where the heat-fusible resin layer of the electrical storage device packaging material and a polypropylene plate are heat-fusible under conditions such that the thickness of the heat-fusible resin layer is 20% or more and 80% or less;
Exterior material for energy storage devices.
Item 2B: The packaging material for an electricity storage device according to Item 1B, wherein the barrier layer is formed of stainless steel, a steel plate, or an aluminum alloy.
Item 3B: The packaging material for an electricity storage device according to Item 1B or 2B, further comprising an adhesive layer between the barrier layer and the heat-sealable resin layer.
Item 4B: The packaging material for an electricity storage device according to any one of Items 1B to 3B, further including a substrate layer on the opposite side of the barrier layer from the heat-sealable resin layer side.
Item 5B: The packaging material for an electricity storage device according to Item 4B, further comprising an adhesive layer between the base material layer and the barrier layer.
Item 6B: The packaging material for an electricity storage device according to any one of Items 1B to 5B, wherein the packaging material for an electricity storage device has a Young's modulus of 6000 MPa or more.
Item 7B. A method for producing an exterior material for an electricity storage device,
The method includes a step of obtaining a laminate in which at least a barrier layer and a thermally adhesive resin layer are laminated,
the barrier layer has an area-average angular difference of GOS (grain orientation dispersion) of 2.50° or less, when a grain boundary is defined as 5°, obtained by performing crystal analysis by an EBSD method on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer, at a position where the heat-fusible resin layer of the electrical storage device packaging material and a polypropylene plate are heat-fusible under conditions such that the thickness of the heat-fusible resin layer is 20% or more and 80% or less;
A method for manufacturing an exterior material for an electricity storage device.
Item 8B: An electricity storage device, in which an electricity storage device element including at least a positive electrode, a negative electrode, and an electrolyte is housed in a package formed from the exterior packaging material for an electricity storage device according to any one of Items 1B to 6B.

REFERENCE SIGNS LIST 10 Electricity storage device 20 Electrode body 30 Electrode terminal 40 Exterior body 50 Exterior film 51 Base material layer 52 Barrier layer 53 Thermally adhesive resin layer 54 Adhesive layer 55 Adhesive layer 60 Lid body 61 Lid main body 62 Cover 70 First sealing portion 80 Second sealing portion

Claims (7)

An exterior packaging material for an electricity storage device, which is composed of a laminate including at least a barrier layer and a heat-sealable resin layer,
the barrier layer is formed of an aluminum alloy foil,
the barrier layer has an area-average angular difference of GOS (grain orientation dispersion) of 0.20° or more and 1.50° or less, where the grain boundary is defined as 5°, obtained by performing crystal analysis by EBSD on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer, at a position where the heat-fusible resin layer of the electrical storage device packaging material and a polypropylene plate are heat-fusible under conditions such that the thickness of the heat-fusible resin layer is 20% or more and 80% or less ;
The packaging material for an electricity storage device has a Young's modulus of 8000 MPa or more and 30000 MPa or less,
An exterior material for an electricity storage device that is not subjected to cold forming and is used to seal the electrode body with an exterior body including the exterior material for an electricity storage device wrapped around the electrode body and a lid body joined to the exterior material for an electricity storage device. The packaging material for an electricity storage device according to claim 1, wherein the packaging material for an electricity storage device has a Young's modulus of 10,000 MPa or more and 30,000 MPa or less . The packaging material for an electricity storage device according to claim 1 or 2, further comprising an adhesive layer between the barrier layer and the heat-sealable resin layer. The packaging material for an electricity storage device according to claim 1 or 2, further comprising a substrate layer on the side of the barrier layer opposite the heat-sealable resin layer. The exterior packaging material for an electricity storage device according to claim 4, further comprising an adhesive layer between the base layer and the barrier layer. A method for producing an exterior material for an electricity storage device, comprising:
The method includes a step of obtaining a laminate in which at least a barrier layer and a thermally adhesive resin layer are laminated,
the barrier layer is formed of an aluminum alloy foil,
the barrier layer has an area-average angular difference of GOS (grain orientation dispersion) of 0.20° or more and 1.50° or less, where the grain boundary is defined as 5°, obtained by performing crystal analysis by EBSD on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer, at a position where the heat-fusible resin layer of the electrical storage device packaging material and a polypropylene plate are heat-fusible under conditions such that the thickness of the heat-fusible resin layer is 20% or more and 80% or less ;
The packaging material for an electricity storage device has a Young's modulus of 8000 MPa or more and 30000 MPa or less,
An exterior material for an electricity storage device that is not subjected to cold forming and is used to seal the electrode body with an exterior body including the exterior material for an electricity storage device wrapped around the electrode body and a lid body joined to the exterior material for an electricity storage device. An electricity storage device, comprising an electricity storage device element including at least a positive electrode, a negative electrode, and an electrolyte, housed in a package formed from the exterior packaging material for an electricity storage device according to claim 1 or 2.