JP7746709B2 - Exterior material for power storage device, manufacturing method thereof, and power storage device - Google Patents

Description

This disclosure relates to an exterior material for an electricity storage device, a method for manufacturing the same, and an electricity storage device.

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

On the other hand, in recent years, with the increasing performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, etc., 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 materials for energy storage devices that have traditionally been widely used have the drawback of being difficult to accommodate the increasing variety of shapes, and there are also limitations to how light they can be made.

In recent years, therefore, a film-like packaging material has been proposed for use in electricity storage devices, which can be easily processed into a variety of shapes and can be made thinner and lighter. This packaging material is made up of a base material, an aluminum alloy foil layer, and a heat-sealable resin layer laminated in that order (see, for example, Patent Document 1).

In such film-like packaging materials, recesses are generally formed by cold forming, and electricity storage device elements such as electrodes and electrolyte are placed in the spaces formed by the recesses. The heat-sealable resin layers are then heat-sealed to each other to obtain an electricity storage device in which the electricity storage device elements are housed inside the packaging material.

Japanese Patent Application Laid-Open No. 2008-287971

In order to increase the energy density of electricity storage devices, it is necessary to form deep recesses in film-type exterior materials through molding. Therefore, the aluminum alloy foil used in exterior materials for electricity storage devices must have high formability.

Al-Fe alloy-based soft aluminum alloy foil is known as an aluminum alloy foil with excellent formability. Specific examples of such soft aluminum alloy foil include aluminum alloy foils having the composition specified in JIS H4160:1994 A8021H-O, JIS H4160:1994 A8079H-O, JIS H4000:2014 A8021P-O, or JIS H4000:2014 A8079P-O.

On the other hand, during processes such as the molding process for the electrical storage device casing material, the process of housing an electrical storage device element in the electrical storage device casing material and heat-sealing it, and the process of folding the heat-sealed portion, if a short circuit occurs between the external terminal and the aluminum alloy foil of the electrical storage device casing material due to a foreign object, or if uneven pressure during heat sealing causes the external terminal and the aluminum alloy foil of the electrical storage device casing material to come into close proximity or contact with each other, and if fine cracks or pinholes occur in the innermost heat-sealing resin layer, current may flow between the aluminum alloy foil of the electrical storage device casing material and the external terminal via the electrolyte that has permeated the heat-sealing resin layer, potentially causing the aluminum alloy foil to corrode due to alloying with lithium ions in the electrolyte (in particular, if the aluminum alloy foil and the negative electrode terminal are short-circuited via the electrolyte, the aluminum alloy foil is prone to corrosion). Corrosion of the aluminum alloy foil can cause problems such as expansion of the aluminum alloy foil, leading to deterioration of the performance of the electrical storage device.

In addition, when sealing an electricity storage device element, a metal plate or the like is used to apply high temperature and high pressure to the electricity storage device casing material, thereby heat-sealing the heat-sealable resin layer. However, applying high temperature and high pressure to the electricity storage device casing material can cause a problem in that the insulating properties of the electricity storage device casing material are reduced.

Under these circumstances, the present disclosure aims to provide an exterior packaging material for an electricity storage device that is composed of at least a substrate layer, a barrier layer including an aluminum alloy foil layer, and a heat-sealable resin layer laminated in this order, and that has excellent formability, effectively inhibits corrosion of the aluminum alloy foil when electricity is passed through the material with electrolyte attached, and also has improved insulation properties.

The inventors of the present disclosure conducted extensive research to solve the above-mentioned problems. Specifically, they conducted extensive research into the composition of the aluminum alloy foil used in the barrier layer of the packaging material for an electricity storage device, and discovered that by setting the Mg and Fe contents within a predetermined range, high formability of the packaging material for an electricity storage device can be ensured and corrosion can be effectively suppressed when electricity is passed through the packaging material while it is exposed to electrolyte. Furthermore, the inventors of the present disclosure also discovered that insulation can be improved by using this aluminum alloy foil for the barrier layer and laminating an adhesive layer formed from a cured product of a resin composition containing a curable resin between the barrier layer and the heat-sealable resin layer.

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.
The laminate is composed of at least a base layer, a barrier layer, and a heat-sealable resin layer in this order,
the barrier layer includes an aluminum alloy foil having a composition of Fe: 0.2 mass% or more and 2.0 mass% or less, and Mg: 0.1 mass% or more and 5.0 mass% or less,
The adhesive layer is formed from a cured product of a resin composition containing a curable resin.

The present disclosure provides an electrical storage device packaging material having at least a substrate layer, a barrier layer including an aluminum alloy foil layer, and a heat-sealable resin layer laminated in this order, which has excellent formability, effectively inhibits corrosion of the aluminum alloy foil when current is passed through the material with electrolyte attached, and has enhanced insulation properties. The present disclosure also provides a method for manufacturing the electrical storage device packaging material, and an electrical storage device.

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 for explaining a method for evaluating corrosion resistance in the examples. FIG. 2 is a schematic diagram showing crystal grains and second-phase particles in a cross section of an aluminum alloy foil in the thickness direction. 1 is a microscope image of the surface of an aluminum alloy foil observed after evaluation of corrosion resistance, showing an example in which corrosion is suitably suppressed. 1 is a microscope image of the surface of an aluminum alloy foil observed after evaluating corrosion resistance, showing an example in which corrosion is not sufficiently suppressed. FIG. 1 is a diagram showing the planar shape of a square punch used in a limit forming height test in an example of the present disclosure.

The electrical storage device packaging material of the present disclosure is composed of a laminate having at least a base layer, a barrier layer, and a heat-sealable resin layer, in this order; the barrier layer contains aluminum alloy foil with a composition of Fe: 0.2% by mass to 2.0% by mass and Mg: 0.1% by mass to 5.0% by mass; and the adhesive layer is formed from a cured product of a resin composition containing a curable resin. By having this configuration, the electrical storage device packaging material of the present disclosure has excellent formability, effectively inhibits corrosion of the aluminum alloy foil when electricity is applied with electrolyte attached, and also enhances insulation.

The disclosed exterior packaging material for an electricity storage device, its manufacturing method, and the electricity storage device are described in detail below. Note that in this specification, numerical ranges indicated by "to" mean "greater than or equal to" or "less than or equal to." For example, the expression "2 to 15 mm" means 2 mm or greater and 15 mm or less.

1. Electricity Storage Device Exterior Material The electricity storage device exterior material 10 of the present disclosure is composed of a laminate including, in this order, a base material layer 1, a barrier layer 3, an adhesive layer 5, and a heat-sealable resin layer 4, as shown in FIG. 1 . In the electricity storage device exterior material 10, the base material layer 1 is the outermost layer, and the heat-sealable resin layer 4 is the innermost layer. When assembling an electricity storage device using the electricity storage device exterior material 10 and an electricity storage device element, the heat-sealable resin layers 4 of the electricity storage device exterior material 10 are placed opposite each other, and the peripheries are heat-sealed to form a space, in which the electricity storage device element is housed. In the laminate constituting the electricity storage device exterior material 10 of the present disclosure, with the barrier layer 3 as the reference, the heat-sealable resin layer 4 side relative to the barrier layer 3 is the inner side, and the base material layer 1 side relative to the barrier layer 3 is the outer side.

The barrier layer 3 of the electrical storage device packaging material of the present disclosure contains aluminum alloy foil. That is, the barrier layer 3 of the electrical storage device packaging material of the present disclosure can be composed of aluminum alloy foil. An electrical storage device packaging material of the present disclosure using aluminum alloy foil satisfying the specified composition described below has excellent formability and effectively suppresses corrosion of the aluminum alloy foil. Furthermore, the adhesive layer of the electrical storage device packaging material of the present disclosure is formed from a cured product of a resin composition containing a curable resin. The electrical storage device packaging material of the present disclosure can improve the insulation properties of the electrical storage device packaging material due to the synergistic effect of the adhesive layer 5 and the barrier layer (aluminum alloy foil).

As shown in Figures 1 to 3, the exterior packaging material 10 for an electricity storage device may optionally include an adhesive layer 2 between the base layer 1 and the barrier layer 3 to enhance adhesion between these layers. Furthermore, as shown in Figure 3, a surface coating layer 6 or the like may be provided on the outer side of the base 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 10 is not particularly limited, but from the viewpoints of cost reduction, improved energy density, etc., it is, for example, 190 μm or less, preferably about 180 μm or less, about 155 μm or less, or about 120 μm or less. Furthermore, from the viewpoint of maintaining the function of the electrical storage device exterior material to protect the electrical storage device elements, the thickness of the laminate constituting the electrical storage device exterior material 10 is preferably about 35 μm or more, about 45 μm or more, or about 60 μm or more. Furthermore, preferred ranges for the laminate constituting the electrical storage device exterior material 10 include, for example, approximately 35 to 190 μm, approximately 35 to 180 μm, approximately 35 to 155 μm, approximately 35 to 120 μm, approximately 45 to 190 μm, approximately 45 to 180 μm, approximately 45 to 155 μm, approximately 45 to 120 μm, approximately 60 to 190 μm, approximately 60 to 180 μm, approximately 60 to 155 μm, and approximately 60 to 120 μm, with approximately 60 to 155 μm being particularly preferred.

In the electrical storage device exterior material 10, the ratio of the total thickness of the base material layer 1, optional adhesive layer 2, barrier layer 3, 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 10 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 10 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 10 is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more.

In addition, in the packaging material for an electric storage device, the MD (Machine Direction) and TD (Transverse Direction) of the barrier layer 3 (described below) during the manufacturing process can usually be determined. When the barrier layer 3 is made of aluminum alloy 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 usually coincides with the RD of the metal foil. Therefore, 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. Furthermore, because 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 electrical storage device packaging material cannot be determined based on the rolling marks on the aluminum alloy foil, it can be determined using the following method. One method for determining the MD of an electrical storage device packaging material is to observe the cross section of the heat-sealable resin layer of the electrical storage device packaging material using an electron microscope to confirm the sea-island structure. In this method, the direction parallel to the cross section in which 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 straight-line distance connecting the leftmost end perpendicular to the thickness direction of the heat-sealable resin layer to the rightmost end in that perpendicular direction is defined as the diameter y. For each cross section, the average of the 20 largest diameters y of the island shapes is calculated. The direction parallel to the cross section with the largest average diameter y of the island shapes is determined to be the MD.

Layers forming the exterior material for an electricity storage device [Base material layer 1]
In the present disclosure, the substrate layer 1 is a layer provided for the purpose of allowing the packaging material for an electricity storage device to function as a substrate. The substrate layer 1 is located on the outer layer side of the packaging material for an electricity storage device.

There are no particular restrictions on the material from which the substrate layer 1 is made, as long as it functions as a substrate, i.e., has at least insulating properties. The substrate layer 1 can be made using, for example, a resin, which may contain additives as described below.

When the base layer 1 is formed from a resin, the base layer 1 may be, for example, a resin film formed from a resin, or may be formed by applying a resin. 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 application methods include roll coating, gravure coating, and extrusion coating.

Examples of resins that form the base layer 1 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 1 may also be a copolymer of these resins, or a modified version of the copolymer. It may also be a mixture of these resins.

Of these, polyester and polyamide are preferred as resins for forming the base layer 1.

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 (I represents isophthalic acid, 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 substrate layer 1 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 base layer 1 may be a single layer, or may be composed of two or more layers. When the base layer 1 is composed of two or more layers, the base layer 1 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 resins into two or more layers. Furthermore, a laminate of resin films formed by co-extrusion of resins into two or more layers may be used as the base layer 1 without being stretched, or may be uniaxially or biaxially stretched to form the base layer 1.

Specific examples of laminates of two or more resin films in the base layer 1 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. Preferably, they are a laminate of stretched nylon film and stretched polyester film, a laminate of two or more stretched nylon film layers, or a laminate of two or more stretched polyester film layers. For example, when the base layer 1 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 surface, it is preferable that the polyester resin film be the outermost layer of the base layer 1 when the base layer 1 is a laminate of two or more resin films.

When the substrate layer 1 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 adhesive layer 2, 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 adhesive layer 2, 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 1. A single type of additive may be used, or two or more types may be mixed together.

In the present disclosure, from the viewpoint of improving the formability of the exterior material for an electrical storage device, it is preferable that a lubricant be present on the surface of the base layer 1. 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 lubricants may be used alone or in combination of two or more.

When a lubricant is present on the surface of the base layer 1, the amount thereof is not particularly limited, but is preferably about 3 mg/ ^m2 or more, more preferably about 4 to 15 mg/ ^m2 , and even more preferably about ⁵ to 14 mg/m2.

The lubricant present on the surface of the base layer 1 may be a lubricant exuded from the resin that makes up the base layer 1, or a lubricant applied to the surface of the base layer 1.

The thickness of the substrate layer 1 is not particularly limited as long as it functions as a substrate, but examples include approximately 3 to 50 μm, and preferably approximately 10 to 35 μm. When the substrate layer 1 is a laminate of two or more resin film layers, the thickness of each resin film constituting each layer is preferably approximately 2 to 25 μm.

[Adhesive layer 2]
In the packaging material for an electricity storage device of the present disclosure, the adhesive layer 2 is a layer that is provided between the base layer 1 and the barrier layer 3 as needed for the purpose of increasing the adhesion between them.

The adhesive layer 2 is formed from an adhesive capable of bonding the base layer 1 and the barrier layer 3. There are no limitations on the adhesive used to form the adhesive layer 2, 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 2 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 those containing a base agent containing a polyol compound and a curing agent containing an isocyanate compound. Preferred examples include two-component curing polyurethane adhesives that use a polyol such as polyester polyol, polyether polyol, or acrylic polyol as the base agent and an aromatic or aliphatic polyisocyanate as the curing agent. Furthermore, it is preferable to use a polyester polyol that has hydroxyl groups on the side chain in addition to the terminal hydroxyl groups of the repeating unit as the polyol compound. Forming the adhesive layer 2 from a polyurethane adhesive provides the electrical storage device exterior material with excellent electrolyte resistance, preventing peeling of the base layer 1 even when electrolyte adheres to the side surface.

Furthermore, in the case of an all-solid-state battery exterior material, adhesive layer 2, like adhesive layer 5 described below, is preferably formed from a cured product of a resin composition containing at least one of polyester and polycarbonate, and at least one of an alicyclic isocyanate compound and an aromatic isocyanate compound. This prevents delamination between the substrate layer and the barrier layer in a high-temperature environment in the all-solid-state battery exterior material. Details of the resin composition in adhesive layer 2 are the same as those for adhesive layer 5.

In addition, the adhesive layer 2 may contain other components as long as they do not impair adhesion, such as colorants, thermoplastic elastomers, tackifiers, and fillers. By including a colorant in the adhesive layer 2, the electrical storage device packaging material can be colored. Known colorants such as pigments and dyes can be used. A single colorant may be used, or two or more colorants 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 2. 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 material for an electrical storage device a black appearance.

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 2 is not particularly limited as long as it colors the electrical storage device exterior material, but may be, for example, approximately 5 to 60% by mass, and preferably 10 to 40% by mass.

There are no particular restrictions on the thickness of the adhesive layer 2, as long as it can bond the base layer 1 and the barrier layer 3 together. However, the lower limit can be, for example, approximately 1 μm or more, or approximately 2 μm or more, and the upper limit can be approximately 10 μm or less, or approximately 5 μm or less. Preferred ranges 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 is a layer (not shown) that is provided as needed between the base material layer 1 and the barrier layer 3. When the adhesive layer 2 is provided, a colored layer may be provided between the base material layer 1 and the adhesive layer 2, or between the adhesive layer 2 and the barrier layer 3. Alternatively, a colored layer may be provided on the outside of the base material layer 1. By providing a colored layer, the packaging material for an electricity storage device can be colored.

The colored layer can be formed, for example, by applying ink containing a colorant to the surface of the base layer 1, the surface of the adhesive layer 2, or the surface of the barrier layer 3. 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 2] section.

[Barrier layer 3]
In the packaging material for an electricity storage device, the barrier layer 3 is a layer that at least prevents the penetration of moisture.

The barrier layer 3 of the electrical storage device packaging material disclosed herein contains aluminum alloy foil.

The aluminum alloy foil contains aluminum alloy foil that satisfies the following composition: Fe (iron): 0.2% by mass to 2.0% by mass, and Mg (magnesium): 0.1% by mass to 5.0% by mass. The main component of the aluminum alloy foil is Al (aluminum), and for example, 92.10% by mass or more is made up of aluminum. The aluminum alloy foil preferably contains Si (silicon). The silicon content is preferably approximately 0.50% by mass or less.

The aluminum alloy foil may also contain other components in addition to Fe, Mg, and Al. Examples of other components include inevitable impurities such as Si (silicon), Mn (manganese), Cu (copper), Cr (chromium), and Zn (zinc). The inevitable impurities in the aluminum alloy foil may each be 0.10% by mass or less and may total 0.40% by mass or less. The other components may be one type or two or more types.

In aluminum alloy foil, Fe crystallizes as Al-Fe intermetallic compounds during casting. If the size of these compounds is large, they become recrystallization sites during annealing, thereby refining the recrystallized grains. If the Fe content is below the lower limit (0.2 mass%), the distribution density of coarse intermetallic compounds decreases, the effect of grain refinement is reduced, and the final grain size distribution becomes non-uniform. If the Fe content exceeds the upper limit (2.0 mass%), the effect of grain refinement saturates or even decreases. Furthermore, the size of the Al-Fe intermetallic compounds formed during casting becomes very large, resulting in reduced elongation and rollability of the aluminum alloy foil. For this reason, the Fe content is set to the above range of 0.2 mass% to 2.0 mass%. For the same reasons, a lower limit of 0.5 mass% is preferable, and for the same reasons, a lower limit of 1.0 mass% and an upper limit of 1.8 mass% are even more preferable.

In aluminum alloy foil, Mg dissolves in aluminum and can increase the strength of the foil through solid-solution strengthening. Furthermore, because Mg dissolves readily in aluminum, its inclusion with Fe reduces the risk of coarsening intermetallic compounds and reducing formability and rollability. If the Mg content falls below the lower limit (0.1% by mass), the strength improvement is insufficient. If the Mg content exceeds the upper limit (5.0% by mass), the aluminum alloy foil becomes hard, resulting in reduced rollability and formability. A particularly preferred lower limit is 0.5% by mass. If the Mg content exceeds 5.0% by mass, the aluminum alloy foil becomes hard and its formability and rollability deteriorate, but it can achieve extremely high strength. It is desirable to limit the Mg content to more than 0.5% by mass and up to 4.5% by mass. Furthermore, the addition of Mg improves the corrosion resistance of the electrical storage device exterior material to the electrolyte. Although the details of the mechanism are not clear, the more Mg added, the less likely the aluminum alloy foil is to react with lithium and other substances in the electrolyte, which can prevent the aluminum alloy foil from pulverizing and the formation of through holes.

In aluminum alloy foil, trace amounts of Si are sometimes added to increase the strength of the foil. However, in this disclosure, a content of 0.5% by mass or less reduces the size of the Al-Fe-Si intermetallic compounds formed during casting, improving the elongation and formability of the aluminum alloy foil. Therefore, even when the aluminum alloy foil is thin, fracture originating from the intermetallic compounds is less likely to occur, and rollability is improved. Furthermore, by not adding large amounts of Si to alloys with a high Mg content, the amount of Mg-Si precipitates formed is reduced, reducing the likelihood of reduced rollability and the amount of Mg in solid solution, and thus reducing strength. For the same reason, it is desirable to limit the Si content to 0.2% by mass or less. The lower limit of the Si content is preferably 0.001% by mass, and more preferably 0.005% by mass. Note that a lower Si content tends to result in better formability, rollability, grain refinement, and ductility.

Aluminum alloy foil may contain unavoidable impurities such as Cu and Mn. The content of each of these impurities is preferably, for example, 0.1% by mass or less. Note that this disclosure does not limit the upper limit of the content of the unavoidable impurities to the above values. However, because Mn is difficult to dissolve in aluminum, unlike Mg, it is not expected to significantly increase the strength of aluminum alloy foil through solid solution strengthening. Furthermore, adding large amounts of Mn to alloys with a high Fe content increases the risk of coarsening of intermetallic compounds and the formation of large Al-Fe-Mn intermetallic compounds, which may result in reduced rollability and formability. For this reason, the Mn content is preferably 0.1% by mass or less. The Mn content is more preferably 0.08% by mass or less. The lower limit of the Mn content is preferably 0.001% by mass, and more preferably 0.005% by mass.

In the present disclosure, from the viewpoint of providing an exterior material for an electricity storage device that has excellent formability and that effectively suppresses corrosion when electricity is passed through it with an electrolyte attached, the aluminum alloy foil preferably has a composition of Mn (manganese) of 0.1% by mass or less, more preferably has a composition of Mn of 0.01% by mass or more and 0.1% by mass or less, and even more preferably has a composition of Mn of 0.01% by mass or more and 0.08% by mass or less.

The preferred composition and properties of aluminum alloy foil are now explained in more detail.

Fe: 0.2% by mass or more and 2.0% by mass or less. Fe crystallizes as Al-Fe intermetallic compounds during casting, and if the size of these compounds is large, they become recrystallization sites during annealing, thereby having the effect of recrystallizing grains. If the Fe content is below the lower limit, the distribution density of coarse intermetallic compounds decreases, the effect of grain refinement is low, and the final grain size distribution becomes non-uniform. If the Fe content exceeds the upper limit, the effect of grain refinement saturates or even decreases, and further, the size of the Al-Fe intermetallic compounds generated during casting becomes very large, resulting in reduced elongation and rollability of the foil. For this reason, the Fe content is set within the above range. For the same reasons, the lower limit of the Fe content is preferably 0.5% by mass, and even more preferably, the lower limit of the Fe content is 1.0% by mass and the upper limit is 1.8% by mass.

Mg: 0.1% by mass or more and 5.0% by mass or less Mg dissolves in aluminum and can increase the strength of the soft foil through solid solution strengthening. Furthermore, because Mg easily dissolves in aluminum, even when it is contained together with Fe, there is little risk of the intermetallic compounds becoming coarse and reducing formability and rollability. If the Mg content is below the lower limit, the improvement in strength becomes insufficient, while if it exceeds the upper limit, the aluminum alloy foil becomes hard, resulting in reduced rollability and formability. A particularly preferred range is 0.5% by mass or more and 5.0% by mass or less.
It has also been confirmed that the addition of Mg improves corrosion resistance against the electrolyte of lithium-ion secondary batteries. Although the details of the mechanism are not clear, the greater the amount of Mg added, the less likely the aluminum alloy foil is to react with lithium in the electrolyte, thereby suppressing pulverization of the aluminum alloy foil and the occurrence of through-holes. Although formability is slightly reduced, it is desirable to set the lower limit of Mg to 0.5 mass% even when a particularly clear improvement in corrosion resistance is expected.

Si: preferably 0.5% by mass or less. Although trace amounts of Si may be added to increase the strength of the foil, in the present disclosure, a content of 0.5% or less reduces the size of the Al-Fe-Si intermetallic compounds generated during casting, improving the elongation and formability of the foil. Even when the foil is thin, fracture originating from the intermetallic compounds is less likely to occur, and rollability is also improved. Therefore, a content of 0.5% by mass or less is preferred. Furthermore, not adding a large amount of Si reduces the amount of Mg-Si precipitates generated, making it less likely to cause a decrease in rollability or a decrease in the amount of Mg in solid solution, and therefore less likely to result in a decrease in strength. For the same reason, it is desirable to limit the Si content to 0.2% by mass or less. The lower the Si content, the better the formability, rollability, degree of crystal grain refinement, and ductility tend to be.

Inevitable impurities: In addition, unavoidable impurities such as Cu and Mn may be contained. The content of these impurities is preferably 0.1% by mass or less. However, in the present disclosure, the upper limit of the content of the unavoidable impurities is not limited to the above numerical values.
However, since Mn is difficult to dissolve in aluminum, unlike Mg, it cannot be expected to significantly increase the strength of the soft foil through solid solution strengthening. Furthermore, adding a large amount of Mn to an alloy with a high Fe content increases the risk of coarsening of intermetallic compounds and the formation of giant Al-Fe-Mn intermetallic compounds, which may lead to a decrease in rollability and formability. For this reason, it is desirable to keep the Mn content at 0.1 mass% or less.

- The orientation density of the Copper orientation and the R orientation as texture is 15 or less. Texture has a significant effect on the mechanical properties and formability of the foil. To obtain good formability, it is desirable to keep the density of the Copper orientation and the R orientation each 15 or less. More preferably, each orientation density is 10 or less.

- The Mg concentration on the surface is 5.0 atomic percent or more and the oxide film thickness is 80 Å or more (Mg: 0.1 mass% to 1.5 mass%)
Although the details of the mechanism are unclear, it has been confirmed that the Mg concentration and oxide film thickness on the foil surface contribute to corrosion resistance against the electrolyte of lithium-ion secondary batteries. A high Mg concentration on the foil surface and the formation of a thick oxide film improve corrosion resistance. Therefore, when Mg is 0.1 mass% or more and 1.5 mass% or less, it is desirable for the Mg concentration on the aluminum foil surface to be 5.0 atomic percent or more and the oxide film thickness to be 80 Å or more. More preferably, the surface Mg concentration is 15.0 atomic percent or more and the oxide film thickness is 200 Å or more. Even more preferably, the surface Mg concentration is 20.0 atomic percent or more.

- The Mg concentration on the surface is 15.0 atomic percent or more and the oxide film thickness is 120 Å or more (Mg: more than 1.5 mass% and 5.0 mass% or less)
As mentioned above, although the details of the mechanism are unclear, it has been confirmed that the Mg concentration and oxide film thickness on the foil surface contribute to corrosion resistance against the electrolyte of lithium-ion secondary batteries. A high Mg concentration on the foil surface and the formation of a thick oxide film improve corrosion resistance. Therefore, when the Mg content is more than 1.5 mass% and not more than 5.0 mass%, it is desirable for the Mg concentration on the aluminum foil surface to be 15.0 atomic percent or more and the oxide film thickness to be 120 Å or more. More preferably, the surface Mg concentration is 20.0 atomic percent or more and the oxide film thickness is 220 Å or more. Even more preferably, the surface Mg concentration is 25.0 atomic percent or more.

When the length of a high-angle grain boundary per unit area measured by backscattered electron diffraction is L1 and the length of a low-angle grain boundary is L2, L1/L2 > 3.0
The proportion of high-angle grain boundaries (HAGBs) and low-angle grain boundaries (LAGBs) in the recrystallized grain structure after annealing affects the elongation and formability of the foil. By reducing the proportion of LAGBs in the recrystallized grain structure after final annealing, localized deformation is suppressed, and elongation and formability are improved. Therefore, by setting L1/L2 > 3.0 and increasing the proportion of HAGBs, high elongation and good formability can be expected. More preferably, L1/L2 > 5.0.

Tensile strength: 110 MPa or more and 180 MPa or less (when Mg: 0.1 mass% or more and 1.5 mass% or less)
When Mg is 0.1% by mass or more and 1.5% by mass or less, a tensile strength of 110 MPa or more is required to dramatically improve impact resistance and puncture strength compared to existing foils such as JIS A8079 and 8021. The tensile strength is preferably 180 MPa or less.
Tensile strength can be achieved by composition selection and optimization of grain size.

Tensile strength: 180 MPa or more (Mg: more than 1.5 mass% and less than 5.0 mass%)
When the Mg content is more than 1.5% by mass and not more than 5.0% by mass, a tensile strength of 180 MPa or more is preferred in order to dramatically improve impact resistance and puncture strength compared to existing foils such as JIS A8079 and 8021. For the same reason, the tensile strength is preferably 200 MPa or more. However, since formability decreases as the tensile strength increases, it is better to keep the tensile strength low when formability is important.
As mentioned above, tensile strength can be achieved by optimizing composition and grain size.

Breaking elongation: 10% or more (when Mg: 0.1% by mass or more and 1.5% by mass or less)
The effect of elongation on formability varies greatly depending on the forming method, and formability is not determined solely by elongation. In the stretching process often used for aluminum packaging materials, the higher the elongation of the aluminum alloy foil, the more advantageous the formability. When the Mg content is 0.1% by mass or more and 1.5% by mass or less, it is desirable for the aluminum alloy foil to have an elongation of 10% or more.
The elongation properties can be achieved by selecting the composition and by reducing the grain size.

Breaking elongation: 15% or more (Mg: more than 1.5% by mass and 5.0% by mass or less)
As described above, the effect of elongation on formability varies greatly depending on the forming method, and formability is not determined solely by elongation. However, in the stretching process that is often used for aluminum packaging materials, the higher the elongation of the aluminum alloy foil, the more advantageous the formability is. When the Mg content is more than 1.5 mass % and not more than 5.0 mass %, it is desirable for the aluminum alloy foil to have an elongation of 15% or more.
As mentioned above, the elongation properties can be achieved by selecting the composition and by refining the grain size.

Average crystal grain size: 25 μm or less. The fine crystal grains of soft aluminum alloy foil can suppress the surface roughness of the foil when deformed, and high elongation and therefore high formability can be expected. The effect of this crystal grain size becomes greater as the foil thickness becomes thinner. To achieve high elongation properties and the resulting high formability, it is desirable for the average crystal grain size to be 25 μm or less.
The average crystal grain size can be achieved by selecting the composition and optimizing the manufacturing conditions such as homogenization treatment and cold rolling reduction.

Preferred compositions of aluminum alloy foil include those satisfying the compositions of specific examples 1 and 2 below.

・Specific example 1
Si: 0.1% by mass or more and 0.5% by mass or less, Fe: 0.2% by mass or more and 2.0% by mass or less, Mg: 0.1% by mass or more and 5.0% by mass or less, Mn: 0.05% by mass or more and 0.1% by mass or less, Cu: 0.0% by mass or more and 0.1% by mass or less, Cr: 0.0% by mass or more and 0.1% by mass or less, Zr: 0.0% by mass or more and 0.1% by mass or less, other inevitable impurities are each 0.05% by mass or less and 0.15% by mass or less in total, and the balance is Al.

・Specific example 2
More preferably, the aluminum alloy foil contains 0.1% by mass or more and 0.5% by mass or less of Si, 0.2% by mass or more and 2.0% by mass or less of Fe, 0.1% by mass or more and 5.0% by mass or less of Mg, 0.1% by mass or more and 0.1% by mass or less of Mn, 0.1% by mass or more and 0.0% by mass or less of Cu, 0.0% by mass or more and 0.15% by mass or less of Cr, 0.0% by mass or less of Zr, and other inevitable impurities are each 0.05% by mass or less and 0.15% by mass or less in total, with the balance being Al.

To dramatically improve impact resistance and puncture strength compared to existing aluminum alloy foils such as JIS A8079 and JIS A8021, the tensile strength of the aluminum alloy foil is preferably 100 MPa or more, and more preferably 200 MPa or more. The upper limit of the tensile strength is preferably 350 MPa. Furthermore, the tensile strength is preferably 200 MPa or more and 350 MPa or less, and more preferably 200 MPa or more and 310 MPa or less. However, since formability decreases as the tensile strength increases, it is better to keep the tensile strength low when formability is important. From the perspective of improving the formability of the exterior material for an energy storage device, the aluminum alloy foil preferably has a tensile strength of 100 MPa or more and 180 MPa or less, as measured on a JIS No. 5 test piece in accordance with JIS Z2241:2011. Specifically, the tensile strength is measured by the method described in the Examples. The tensile strength of the aluminum alloy foil can be achieved by selecting the composition and optimizing the crystal grain size.

The effect of elongation on the formability of aluminum alloy foil varies greatly depending on the forming method, and formability is not determined solely by elongation. When stretching aluminum alloy foil for exterior packaging materials, the higher the elongation of the aluminum alloy foil, the more advantageous it is for forming. The aluminum alloy foil preferably has a breaking elongation of 10% or more, more preferably 15% or more, measured using a JIS No. 5 test piece in accordance with JIS Z2241:2011. The upper breaking elongation limit is preferably 40%, more preferably 30%. Furthermore, the breaking elongation is preferably 0% to 40%, more preferably 15% to 40%, and even more preferably 15% to 30%. Specifically, the breaking elongation is measured using the method described in the Examples. The elongation characteristics of aluminum alloy foil can be achieved by selecting the composition and refining the crystal grain size.

Aluminum alloy foil satisfying the above-described composition and properties can be manufactured by adjusting the composition based on an aluminum alloy having a composition in the A5000 series of alloy numbers specified in JIS H4000:2014, and then performing the same processes as known aluminum alloy foil manufacturing methods, such as melting, homogenization, hot rolling, cold rolling, intermediate annealing, cold rolling, and final annealing. For manufacturing conditions for aluminum alloy foil, see, for example, Japanese Patent Application Laid-Open No. 2005-163077. Furthermore, analysis of the chemical components contained in the aluminum alloy foil is performed using analytical tests specified in JIS H4160-1994.

For example, an aluminum alloy ingot with a composition of Fe: 0.2% by mass to 2.0% by mass and Mg: 0.1% by mass to 5.0% by mass is cast using a conventional method such as semi-continuous casting. The resulting ingot is then subjected to a homogenization treatment at 480-540°C for 6-12 hours.

Generally, homogenization treatment of aluminum materials is carried out at 400-600°C for a long period of time (for example, approximately 12 hours), but considering the grain refinement achieved by adding Fe as in this disclosure, heat treatment at 480-540°C for 6 hours or more is desirable. Temperatures below 480°C result in insufficient grain refinement, while temperatures above 540°C result in coarsening of the grains. Treatment times of less than 6 hours result in insufficient homogenization.

After homogenization, the aluminum alloy sheet is hot-rolled to the desired thickness. Hot-rolling can be performed using conventional methods, but the coiling temperature during hot-rolling should preferably be above the recrystallization temperature, specifically 300°C or higher. Temperatures below 300°C are undesirable, as they can precipitate fine Al-Fe intermetallic compounds of 0.3 μm or less, cause recrystallized grains and fibrous grains to coexist after hot-rolling, and result in non-uniform grain sizes after intermediate annealing and final annealing, potentially reducing elongation properties.

After hot rolling, cold rolling, intermediate annealing, and final cold rolling are performed to reduce the thickness to 5 to 100 μm, thereby obtaining the aluminum alloy foil of the present disclosure. It is desirable for the final cold rolling reduction to be 90% or more.

Intermediate annealing during cold rolling is not required, but may be performed in some cases. There are two types of intermediate annealing: batch annealing, in which the coil is placed in a furnace and held there for a certain period of time, and continuous annealing line (hereafter referred to as CAL annealing), in which the material is rapidly heated and cooled. When intermediate annealing is added, either method is acceptable, but CAL annealing is preferred if the goal is to refine the crystal grains and increase strength, and batch annealing is preferred if formability is a priority.

For example, batch annealing can be performed at 300-400°C for 3 hours or more, while CAL annealing can be performed under the following conditions: heating rate: 10-250°C/sec, heating temperature: 400-550°C, no holding time or holding time: 5 seconds or less, and cooling rate: 20-200°C/sec. However, this disclosure does not specifically limit the use of intermediate annealing or the conditions for intermediate annealing, if any.

After foil rolling, final annealing is performed to produce soft foil. Final annealing after foil rolling is generally carried out at 250°C to 400°C. However, to further enhance the corrosion resistance effect of Mg, it is desirable to hold the foil at a high temperature of 350°C or higher for 5 hours or more.

If the final annealing temperature is too low, softening will be insufficient and Mg will not be concentrated sufficiently on the foil surface, which could result in reduced corrosion resistance. If the temperature exceeds 400°C, Mg will be excessively concentrated on the foil surface, causing discoloration of the foil and changes in the properties of the oxide film, resulting in microcracks and reduced corrosion resistance. If the final annealing time is less than 5 hours, the effect of the final annealing will be insufficient.

A preferred method for preparing the aluminum alloy foil will be described in more detail below.
An aluminum alloy ingot containing 0.2 to 2.0% by mass of Fe, 0.1 to 5.0% by mass of Mg, the balance being Al and unavoidable impurities, and optionally 0.1% by mass or less of Mn, is cast by a conventional method such as semi-continuous casting, and the resulting ingot is subjected to a homogenization treatment at 480 to 540°C for 6 to 12 hours.

Homogenization treatment: 450 to 540°C
The homogenization process aims to eliminate microsegregation within the ingot and adjust the distribution of intermetallic compounds, and is a very important process for ultimately obtaining the desired crystal grain structure.
Generally, homogenization of aluminum materials is carried out at 400 to 600° C. for a long period of time, but in the present invention, it is necessary to take into consideration the refinement of crystal grains by adding Fe.
In homogenization treatment, at temperatures below 450°C, Fe precipitation is insufficient, resulting in coarsening of crystal grains during final annealing and an increase in the rate of in-situ recrystallization, which increases the rate of LAGB. This raises concerns about a decrease in L1/L2 and a decrease in formability due to an increase in the orientation density of the Copper and R orientations. Furthermore, at temperatures above 550°C, crystallized deposits grow significantly, leading to coarsening of crystal grains during final annealing and a decrease in formability. The homogenization treatment time must be at least 3 hours. Precipitation is insufficient at temperatures below 3 hours, resulting in a decrease in the density of fine intermetallic compounds. A temperature of 480 to 520°C and a time of 5 hours or more are desirable.

After homogenization, the aluminum alloy sheet is hot-rolled to the desired thickness. Hot-rolling can be performed using conventional methods, but the coiling temperature during hot-rolling should preferably be above the recrystallization temperature, specifically 300°C or higher. Temperatures below 300°C are undesirable, as they can precipitate fine Al-Fe intermetallic compounds of 0.3 μm or less, cause recrystallized grains and fibrous grains to coexist after hot-rolling, and result in non-uniform grain sizes after intermediate annealing and final annealing, potentially reducing elongation properties.

After the hot rolling, cold rolling, intermediate annealing, and final cold rolling are carried out to a thickness of 5 to 100 μm, thereby obtaining the aluminum alloy foil of the present invention.
There are two types of intermediate annealing: batch annealing, in which a coil is placed in a furnace and held there for a certain period of time, and continuous annealing line (hereinafter referred to as CAL annealing), in which the material is rapidly heated and cooled. Either method is acceptable when intermediate annealing is applied, but CAL annealing is desirable when grain refinement and high strength are desired. However, there is a concern that texture may develop after the subsequent final cold rolling and final annealing, increasing the density of Copper orientation and R orientation and reducing formability. Therefore, if formability is prioritized, batch annealing is preferred.
For example, in batch annealing, conditions such as 300 to 400°C for 3 hours or more can be adopted, and in CAL annealing, conditions such as a temperature rise rate of 10 to 250°C/sec, a heating temperature of 400 to 550°C, no holding time or a holding time of 5 seconds or less, and a cooling rate of 20 to 200°C/sec can be adopted. However, the present invention is not limited to any particular conditions such as whether intermediate annealing is performed or not.

Final cold rolling reduction: 84.0% or more and 97.0% or less. The higher the final cold rolling reduction from the intermediate annealing to the final thickness, the greater the amount of strain accumulated in the material, resulting in finer recrystallized grains after final annealing. It also has the effect of suppressing in-situ recrystallization, and improved formability is expected as L1/L2 increases. Specifically, a final cold rolling reduction of 84.0% or more is desirable. However, if the final cold rolling reduction is too high, there is a concern that formability will decrease due to an increase in the orientation density of the Copper orientation and the R orientation even after final annealing, and as a result, L1/L2 will also decrease. Therefore, specifically, a final cold rolling reduction of 97.0% or less is desirable. Furthermore, if the final cold rolling reduction is low, there is a concern that formability will decrease due to coarsening of crystal grains and a decrease in L1/L2. For the same reason, a more desirable range of the final cold rolling reduction is 90.0% or more and 93.0% or less.

After the foil rolling, final annealing is performed to produce a soft foil. Final annealing after foil rolling is generally performed at 250°C to 400°C. However, to enhance the corrosion resistance effect of Mg, it is preferable to hold the foil at a high temperature of 300°C or higher for 5 hours or more, and more preferably 350°C to 400°C.
If the final annealing temperature is low, softening is insufficient, and there is a concern that the L1/L2 ratio will decrease and the orientation densities of the Copper orientation and the R orientation will increase. Furthermore, there is a concern that the Mg concentration on the foil surface and the growth of the oxide film will be insufficient, resulting in a decrease in corrosion resistance. If the temperature exceeds 400°C, there is a concern that Mg will be excessively concentrated on the foil surface, causing discoloration of the foil, and that the properties of the oxide film will change, resulting in the generation of microcracks, resulting in a decrease in corrosion resistance. If the final annealing time is less than 5 hours, the effect of the final annealing will be insufficient.

At room temperature, the obtained aluminum alloy foil has a tensile strength of 110 MPa or more and 180 MPa or less and a breaking elongation of 10% or more when the Mg content is 0.1% by mass or more and 1.5% by mass or less, and a tensile strength of 180 MPa or more and a breaking elongation of 15% or more when the Mg content is more than 1.5% by mass and 5.0% by mass or less. The average crystal grain size is also 25 μm or less.

In the present disclosure, as shown in the schematic diagram of Figure 5, when any 100 second-phase particles 3b within the field of view of an optical microscope are examined in a cross section of the aluminum alloy foil (barrier layer 3) in the thickness direction, and the linear distance connecting the leftmost end of each second-phase particle 3b perpendicular to the thickness direction to the rightmost end of each second-phase particle 3b perpendicular to the thickness direction is defined as diameter y, the average diameter y of the top 20 second-phase particles 3b in descending order of diameter y is preferably 10.0 μm or less. This makes it possible to laminate the aluminum alloy foil to an exterior packaging material for an electricity storage device and form it without generating pinholes or cracks, thereby providing the exterior packaging material for an electricity storage device with excellent formability. Furthermore, in the present disclosure, the average diameter y of the second phase particles 3b in the aluminum alloy foil (barrier layer 3) is 10.0 μm or less, so that the thickness of the aluminum alloy foil is, for example, approximately 85 μm or less, further approximately 50 μm or less, or even approximately 40 μm or less, and even when the total thickness of the exterior material for an electricity storage device is as thin as the aforementioned thickness, pinholes and cracks are unlikely to occur during molding, providing excellent formability.

Furthermore, from the viewpoint of further improving moldability, the average diameter y is more preferably approximately 1.0 to 8.0 μm, and even more preferably approximately 1.0 to 6.0 μm. Note that because Figure 5 is a schematic diagram, the drawing is omitted and not all 100 second-phase particles 3b are depicted.

In this disclosure, second-phase particles contained in aluminum alloy foil refer to intermetallic compound particles present in the aluminum alloy, and are crystallized phase particles separated by rolling or precipitated phase particles precipitated during homogenization treatment or annealing.

When a cross section of aluminum alloy foil in the thickness direction is observed with a scanning electron microscope (SEM), crystal grains typically form boundaries where multiple crystals meet. In contrast, second-phase particles typically form boundaries with a single crystal. Furthermore, because the crystal grains and second-phase particles are in different phases, they are characterized by different colors in SEM images. Furthermore, when a cross section of an aluminum alloy foil layer in the thickness direction is observed with an optical microscope, only the second-phase particles appear black due to the difference in phase between the crystal grains and second-phase particles, making observation easier.

From the viewpoint of further improving formability, the average crystal grain size in the aluminum alloy foil is preferably 25.0 μm or less, more preferably 20.0 μm or less, even more preferably 10.0 μm or less, and is preferably 1.0 μm or more, 3.0 μm or more, and more preferably 9.0 μm or more. Preferred ranges for the average crystal grain size include approximately 1.0 to 25.0 μm, approximately 1.0 to 20.0 μm, approximately 1.0 to 10.0 μm, approximately 3.0 to 25.0 μm, approximately 3.0 to 20.0 μm, approximately 3.0 to 10.0 μm, approximately 9.0 to 25.0 μm, approximately 9.0 to 20.0 μm, and approximately 9.0 to 10.0 μm. When the average crystal grain size in the aluminum alloy foil is 25.0 μm or less and the diameter y of the second-phase particles 3b is the above value, the formability of the electrical storage device exterior material described below can be further improved.

In this disclosure, the average crystal grain size in an aluminum alloy foil refers to the average value of the maximum diameters x of 100 aluminum alloy crystal grains 3a located within the field of view when a cross section of the aluminum alloy foil in the thickness direction is observed with a scanning electron microscope (SEM), and the maximum diameter x is defined as the linear distance connecting the leftmost end of each individual crystal grain in the direction perpendicular to the thickness direction to the rightmost end of each individual crystal grain in the direction perpendicular to the thickness direction, as shown in the schematic diagram of Figure 5. Note that because Figure 5 is a schematic diagram, the drawing is omitted and 100 crystal grains 3a are not depicted.

The thickness of the aluminum alloy foil in the exterior material for the energy storage device should at least function as a barrier layer that prevents moisture from penetrating, with a lower limit of approximately 9 μm or more and an upper limit of approximately 200 μm or less. From the perspective of reducing the thickness of the exterior material for an electricity storage device, the upper limit of the thickness of the aluminum alloy foil is, for example, preferably about 85 μm or less, more preferably about 50 μm or less, even more preferably about 45 μm or less, and particularly preferably about 40 μm or less. The lower limit is preferably about 10 μm or more, even more preferably about 20 μm or more, and more preferably about 25 μm or more. Preferred ranges for the thickness include about 10 to 85 μm, about 10 to 50 μm, about 10 to 45 μm, about 10 to 40 μm, about 20 to 85 μm, about 20 to 50 μm, about 20 to 45 μm, about 20 to 40 μm, about 25 to 85 μm, about 25 to 50 μm, about 25 to 45 μm, and about 25 to 40 μm.

In addition, it is preferable that at least one side of the aluminum alloy foil be provided with a corrosion-resistant coating to prevent dissolution and corrosion of the aluminum alloy foil. The aluminum alloy foil may be provided with a corrosion-resistant coating on both sides. Here, the corrosion-resistant coating refers to a thin film formed on the surface of the aluminum alloy foil, which is provided with corrosion resistance by, for example, hydrothermal conversion treatments such as boehmite treatment, chemical conversion treatments, anodizing treatments, plating treatments such as nickel or chromium plating, or corrosion prevention treatments such as applying a coating agent. The corrosion-resistant coating may be formed by a single type of treatment, or by a combination of two or more types. Furthermore, the aluminum alloy foil may be formed in a single layer or in multiple layers. Furthermore, among these treatments, hydrothermal conversion treatments and anodizing treatments dissolve the metal foil surface with a treatment agent to form metal compounds with excellent corrosion resistance. These treatments may also be included in the definition of chemical conversion treatments. Furthermore, when an aluminum alloy foil has a corrosion-resistant coating, the corrosion-resistant coating is included in the aluminum alloy foil.

The corrosion-resistant coating prevents delamination between the aluminum alloy foil and the base layer during the molding of the exterior material for electricity storage devices. It also prevents dissolution and corrosion of the aluminum alloy foil surface and dissolution and corrosion of aluminum oxide present on the aluminum alloy foil surface due to hydrogen fluoride produced by the reaction between the electrolyte and water. It also improves the adhesion (wettability) of the aluminum alloy foil surface, preventing delamination between the base layer and the aluminum alloy foil 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 aluminum alloy foil in the chemical conversion treatment is not particularly limited. For example, in the case of a paint-type chromate treatment, it is desirable that the aluminum alloy foil surface contain, ^per square meter, about 0.5 to 50 mg, preferably about 1.0 to 40 mg, of a chromate-equivalent chromate compound, about 0.5 to 50 mg, preferably about 1.0 to 40 mg, of a phosphorus compound, and about 1.0 to 200 mg, preferably about 5.0 to 150 mg, of an aminated phenol polymer.

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 carried out by applying a solution containing the compound used to form the corrosion-resistant coating to the surface of the aluminum alloy foil using methods such as bar coating, roll coating, gravure coating, or dipping, and then heating the aluminum alloy foil to a temperature of approximately 70 to 200°C. Furthermore, before chemical conversion treatment is carried out on the aluminum alloy foil, the foil may be subjected to a degreasing treatment using methods such as alkaline dipping, electrolytic cleaning, acid cleaning, or electrolytic acid cleaning. Performing such a degreasing treatment allows for more efficient chemical conversion treatment of the aluminum alloy foil 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, only degreasing may be performed.

[Thermofusible resin layer 4]
In the exterior packaging material for an electricity storage device of the present disclosure, the heat-sealable resin layer 4 corresponds to the innermost layer and is a layer (sealant layer) that functions to seal the electricity storage device elements by heat-sealing the heat-sealable resin layers to each other when assembling the electricity storage device.

The resin constituting the heat-sealable resin layer 4 is not particularly limited as long as it is heat-sealable, but resins containing a polyolefin skeleton, such as polyolefins and acid-modified polyolefins, are preferred. The polyolefin skeleton of the resin constituting the heat-sealable resin layer 4 can be determined by, for example, infrared spectroscopy or gas chromatography-mass spectrometry. Furthermore, when the resin constituting the heat-sealable resin layer 4 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 4 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.

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.

Acid-modified polyolefins are polymers modified by block or graft polymerization of polyolefins with an acid component. Examples of acid-modified polyolefins include the polyolefins listed above, copolymers of the polyolefins with polar molecules such as acrylic acid or methacrylic acid, and 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 4 may be formed from a single type of resin, or may be formed from a blend polymer of two or more types of resin. Furthermore, the heat-sealable resin layer 4 may be formed from only one layer, or may be formed from two or more layers of the same or different resins.

Furthermore, the packaging material 1 for an electricity storage device disclosed herein can be suitably used as a packaging material for an all-solid-state battery, and the melting point of the heat-sealable resin layer 4 of the packaging material for an all-solid-state battery is preferably 150 to 250°C, more preferably 180 to 270°C, even more preferably 200 to 270°C, and even more preferably 200 to 250°C.

Resins contained in the heat-sealable resin layer 4 of the all-solid-state battery casing material include the aforementioned polyolefins such as polypropylene and polyethylene, acid-modified polyolefins such as acid-modified polypropylene and acid-modified polyethylene, and polyesters such as polyethylene terephthalate and polybutylene terephthalate. Among these, polybutylene terephthalate has excellent heat resistance, so in the all-solid-state battery casing material, the heat-sealable resin layer 4 is preferably formed from a polybutylene terephthalate film. The polybutylene terephthalate film forming the heat-sealable resin layer 4 may be prepared by laminating a pre-prepared polybutylene terephthalate film with the adhesive layer 5, or the resin forming the polybutylene terephthalate film may be melt-extruded to form a film and then laminated with the adhesive layer 5.

The polybutylene terephthalate film may be a stretched polybutylene terephthalate film or an unstretched polybutylene terephthalate film, with an unstretched polybutylene terephthalate film being preferred.

It is preferable that the polybutylene terephthalate film further contains an elastomer in addition to polybutylene terephthalate. The elastomer enhances the flexibility of the polybutylene terephthalate film while ensuring its durability in high-temperature environments. Preferred elastomers include at least one thermoplastic elastomer selected from polyesters, polyamides, polyurethanes, polyolefins, polystyrenes, and polyethers, as well as thermoplastic elastomer copolymers thereof. The elastomer content in the polybutylene terephthalate film is not particularly limited, as long as it enhances the flexibility of the polybutylene terephthalate film while ensuring its durability in high-temperature environments. For example, the elastomer content may be approximately 0.1% by mass or more, preferably approximately 0.5% by mass or more, more preferably approximately 1.0% by mass or more, and even more preferably approximately 3.0% by mass or more. The elastomer content may be, for example, approximately 10.0% by mass or less, approximately 8.0% by mass or less, or approximately 5.0% by mass or less. Preferred ranges for the content include approximately 0.1 to 10.0% by mass, approximately 0.1 to 8.0% by mass, approximately 0.1 to 5.0% by mass, approximately 0.5 to 10.0% by mass, approximately 0.5 to 8.0% by mass, approximately 0.5 to 5.0% by mass, approximately 1.0 to 10.0% by mass, approximately 1.0 to 8.0% by mass, approximately 1.0 to 5.0% by mass, approximately 3.0 to 10.0% by mass, approximately 3.0 to 8.0% by mass, and approximately 3.0 to 5.0% by mass.

In an all-solid-state battery casing material, when the heat-sealable resin layer 4 is formed of two or more layers, at least one layer is formed of a polybutylene terephthalate film, and the polybutylene terephthalate film is preferably the innermost layer of the all-solid-state battery casing material. Furthermore, the layer that adheres to the adhesive layer 5 is preferably a polybutylene terephthalate film. When the heat-sealable resin layer 4 is formed of two or more layers, the layers not formed of a polybutylene terephthalate film may be formed of, for example, a polyolefin such as polypropylene or polyethylene, or an acid-modified polyolefin such as acid-modified polypropylene or acid-modified polyethylene. However, since polyolefins and acid-modified polyolefins have lower durability in high-temperature environments than polybutylene terephthalate, in an all-solid-state battery casing material, the heat-sealable resin layer 4 is preferably formed solely of a polybutylene terephthalate film.

The heat-sealable resin layer 4 may also contain a lubricant, if necessary. When the heat-sealable resin layer 4 contains a lubricant, the formability of the electrical storage device packaging material can be improved. There are no particular restrictions on the lubricant, and any known lubricant can be used. The lubricant may be used alone or in combination of two or more types.

The lubricant is not particularly limited, but preferably an amide-based lubricant is used. Specific examples of lubricants include those exemplified for base layer 1. One type of lubricant may be used alone, or two or more types may be used in combination.

When a lubricant is present on the surface of the heat-fusible resin layer 4, the amount thereof is not particularly limited, but from the viewpoint of improving the formability of the exterior material for an electricity storage device, it is preferably about 10 to 50 mg/ ^m2 , and more preferably about 15 to 40 mg/ ^m2 .

The lubricant present on the surface of the heat-sealable resin layer 4 may be a lubricant exuded from the resin that makes up the heat-sealable resin layer 4, or a lubricant applied to the surface of the heat-sealable resin layer 4.

The thickness of the heat-sealable resin layer 4 is not particularly limited as long as it functions to heat-seal the heat-sealable resin layers together and seal the electricity storage device element, 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 5 described below is 10 μm or greater, the thickness of the heat-sealable resin layer 4 is preferably approximately 85 μm or less, more preferably approximately 15 to 45 μm. For example, if the thickness of the adhesive layer 5 described below is less than 10 μm or if the adhesive layer 5 is not provided, the thickness of the heat-sealable resin layer 4 is preferably approximately 20 μm or greater, more preferably approximately 35 to 85 μm.

[Adhesive layer 5]
In the packaging material for an electricity storage device of the present disclosure, the adhesive layer 5 is a layer provided between the barrier layer 3 (or acid-resistant film) and the heat-sealable resin layer 4 in order to firmly bond them together.

The adhesive layer 5 is formed from a cured product of a resin composition containing a curable resin. The term "curable resin" refers to a resin that has curability, such as a thermosetting resin or an ionizing radiation-curable resin, and does not have a clear melting peak temperature after curing. The resin composition used to form the adhesive layer 5 can be similar to the resin composition used in the adhesive exemplified for the adhesive layer 2. The adhesive layer 5 preferably contains a polyolefin skeleton, such as the polyolefins and acid-modified polyolefins exemplified for the heat-fusible resin layer 4. The presence of a polyolefin skeleton in the cured product of the resin composition constituting the adhesive layer 5 can be determined by, for example, infrared spectroscopy or gas chromatography-mass spectrometry, and any analytical method is not particularly limited. Furthermore, when the cured product of the resin composition constituting the adhesive layer 5 is analyzed by infrared spectroscopy, a peak derived from maleic anhydride is preferably detected. For example, when a maleic anhydride-modified polyolefin is measured by infrared spectroscopy, peaks derived from maleic anhydride are detected near wavenumbers 1760 cm ^-1 and 1780 cm ^-1 . However, if the degree of acid denaturation is low, the peak may be too small to be detected. In this case, analysis can be performed using nuclear magnetic resonance spectroscopy.

In order to more effectively achieve the effects of the present invention, the adhesive layer 5 is preferably formed from a cured product of a resin composition containing an acid-modified polyolefin. Particularly preferred examples of 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.

Furthermore, from the viewpoint of more optimally exerting the effects of the present invention, it is more preferable that the adhesive layer 5 be a cured product of a resin composition containing an acid-modified polyolefin and a curing agent. In this case, the acid-modified polyolefin and the curing agent constitute a curable resin. Preferred examples of acid-modified polyolefins include those listed above.

Furthermore, the adhesive layer 5 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 5 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. A preferred polyester is, for example, an amide ester resin. Amide ester resins are generally produced by the reaction of a carboxyl group and an oxazoline group. It is more preferred that the adhesive layer 5 is a cured product of a resin composition containing at least one of these resins and the acid-modified polyolefin. Furthermore, if unreacted compounds of curing agents such as compounds having an isocyanate group, compounds having an oxazoline group, or epoxy resin remain in the adhesive layer 5, the presence of the unreacted compounds can be confirmed by a method selected from the group consisting of infrared spectroscopy, Raman spectroscopy, and time-of-flight secondary ion mass spectrometry (TOF-SIMS).

In order to further enhance the adhesion between the barrier layer 3 and the adhesive layer 5, the adhesive layer 5 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, curing agents having an epoxy group, and polyurethane. Whether the adhesive layer 5 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 enhancing adhesion between the barrier layer 3 and the adhesive layer 5, 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, biuret compounds, and isocyanurates.

The content of the compound having an isocyanate group in the adhesive layer 5 is preferably in the range of 0.1 to 50% by mass, and more preferably in the range of 0.5 to 40% by mass, of the resin composition that constitutes the adhesive layer 5. This effectively improves the adhesion between the barrier layer 3 and the adhesive layer 5.

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 5 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 5. This effectively improves the adhesion between the barrier layer 3 and the adhesive layer 5.

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 known epoxy resins 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 the first disclosure, the weight-average molecular weight of the epoxy resin is a value measured by gel permeation chromatography (GPC) under conditions 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, 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 adhesive layer 5 is preferably in the range of 0.1 to 50% by mass, and more preferably in the range of 0.5 to 40% by mass, of the resin composition that makes up adhesive layer 5. This effectively improves the adhesion between barrier layer 3 and adhesive layer 5.

The polyurethane is not particularly limited, and any known polyurethane can be used. The adhesive layer 5 may be, for example, a cured product of a two-component curing polyurethane.

The proportion of polyurethane in adhesive layer 5 is preferably in the range of 0.1 to 50 mass % of the resin composition constituting adhesive layer 5, and more preferably in the range of 0.5 to 40 mass %. This effectively improves adhesion between barrier layer 3 and adhesive layer 5 in an atmosphere containing components that induce corrosion of the barrier layer, such as electrolyte solution.

When adhesive layer 5 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.

Furthermore, when the packaging material for an electricity storage device is a packaging material for an all-solid-state battery, the adhesive layer is preferably formed from a cured product of a resin composition containing at least one of polyester and polycarbonate, and at least one of an alicyclic isocyanate compound and an aromatic isocyanate compound. This prevents delamination between the barrier layer and the heat-sealable resin layer in high-temperature environments, and also enables the packaging material for an all-solid-state battery to exhibit high sealing strength.

The polyester is preferably a polyester polyol. There are no particular restrictions on the polyester polyol, so long as it has an ester bond in the polymer main chain and multiple hydroxyl groups at the terminals or side chains. The polycarbonate is preferably a polycarbonate polyol. There are no particular restrictions on the polyester polyol, so long as it has a carbonate bond in the polymer main chain and multiple hydroxyl groups at the terminals or side chains. The polyester is preferably, for example, a polyester in which a polyester polyol has been reacted with a polyisocyanate (e.g., a diisocyanate) in advance to extend the urethane chain, or a polycarbonate in which a polycarbonate polyol has been reacted with a polyisocyanate (e.g., a diisocyanate) in advance to extend the urethane chain. The resin composition that forms the adhesive layer may contain one type of polyester or two or more types of polycarbonate.

The alicyclic isocyanate compound is not particularly limited as long as it has an alicyclic structure and an isocyanate group. Preferably, the alicyclic isocyanate compound has two or more isocyanate groups. Specific examples of alicyclic isocyanate compounds include isophorone diisocyanate (IPDI), bis(4-isocyanatocyclohexyl)methane, 1,3-bis(isocyanatomethyl)cyclohexane, methylenebis(4,1-cyclohexylene)diisocyanate, and their polymers or nurates, as well as mixtures and copolymers with other polymers. Examples of other alicyclic isocyanate compounds include adducts, biuret compounds, and isocyanurates. Furthermore, the alicyclic isocyanate compound is preferably a polyol-modified polyisocyanate obtained by reacting an alicyclic isocyanate with a polyol (e.g., polyester polyol) in advance. The resin composition forming the adhesive layer may contain one or more types of alicyclic isocyanate compounds.

The aromatic isocyanate compound is not particularly limited as long as it has an aromatic ring and an isocyanate group. Preferably, the aromatic isocyanate compound has two or more isocyanate groups. Specific examples of aromatic isocyanate compounds include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), their polymers or nurates, mixtures of these, and copolymers with other polymers. Other examples include adducts, biuret compounds, and isocyanurates. The aromatic isocyanate compound is preferably a polyol-modified polyisocyanate, which is prepared by reacting an aromatic isocyanate with a polyol (e.g., polyester polyol) in advance. The resin composition forming the adhesive layer 5 may contain one or more types of aromatic isocyanate compounds.

The resin composition forming the adhesive layer may, for example, contain an alicyclic isocyanate compound but not contain an aromatic isocyanate compound, or may, for example, contain an aromatic isocyanate compound but not contain an alicyclic isocyanate compound, or may, for example, contain both an alicyclic isocyanate compound and an aromatic isocyanate compound. It is preferable that the resin composition forming the adhesive layer 32 contain an aromatic isocyanate compound.

The content of the alicyclic isocyanate compound and aromatic isocyanate compound in the adhesive layer is preferably in the range of 0.1 to 50% by mass, and more preferably in the range of 0.5 to 40% by mass, of the resin composition constituting the adhesive layer 5. Furthermore, when the adhesive layer 5 contains both an alicyclic isocyanate compound and an aromatic isocyanate compound, the total content of these compounds in the resin composition constituting the adhesive layer 5 is preferably in the range of 0.1 to 50% by mass, and more preferably in the range of 0.5 to 40% by mass.

The upper limit of the thickness of adhesive layer 5 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 lower limit is preferably approximately 0.1 μm or more, or approximately 0.5 μm or more. The thickness range 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 adhesive layer 2 or a cured product of an acid-modified polyolefin and a curing agent, the thickness is preferably approximately 1 to 10 μm, more preferably approximately 1 to 5 μm. Furthermore, when using a resin exemplified for the heat-sealable resin layer 4, the thickness is preferably about 2 to 50 μm, and more preferably about 10 to 40 μm. When the adhesive layer 5 is an adhesive exemplified for the adhesive layer 2, or a cured product of a resin composition containing an acid-modified polyolefin and a curing agent, the adhesive layer 5 can be formed, for example, by applying the resin composition and curing it by heating or the like. When using a resin exemplified for the heat-sealable resin layer 4, the heat-sealable resin layer 4 and the adhesive layer 5 can be formed, for example, by extrusion molding.

[Surface coating layer 6]
The packaging material for an electricity storage device according to the present disclosure may, if necessary, have a surface coating layer 6 on the substrate layer 1 (the side of the substrate layer 1 opposite to the barrier layer 3) for the purpose of improving at least one of design, electrolyte resistance, scratch resistance, formability, etc. The surface coating layer 6 is a layer located on the outermost layer side of the packaging material for an electricity storage device when an electricity storage device is assembled using the packaging material for an electricity storage device.

The surface coating layer 6 can be formed from a resin such as polyvinylidene chloride, polyester, polyurethane, acrylic resin, or epoxy resin.

When the resin forming the surface coating layer 6 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 base agent containing a polyol compound and a curing agent containing an isocyanate compound. Preferred examples include two-component curing polyurethanes that use a polyol such as polyester polyol, polyether polyol, or acrylic polyol as the base agent and an aromatic or aliphatic polyisocyanate as the curing agent. Furthermore, it is preferable to use a polyester polyol that has hydroxyl groups on the side chain in addition to the terminal hydroxyl groups of the repeating unit as the polyol compound. Forming the surface coating layer 6 from polyurethane provides the electrical storage device exterior material with excellent electrolyte resistance.

The surface coating layer 6 may contain additives such as the aforementioned lubricants, antiblocking agents, matting agents, flame retardants, antioxidants, tackifiers, and antistatic agents, at least on the surface and/or inside the surface coating layer 6, as needed, depending on the functionality to be provided by the surface coating layer 6 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 size measured using a laser diffraction/scattering particle size distribution analyzer.

The additive 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. Additives may be used alone or in combination of two or more. Among these additives, silica, barium sulfate, and titanium oxide are preferred from the standpoints of dispersion stability and cost. The additives may also be subjected to various surface treatments, such as insulation treatments and high-dispersion treatments.

The method for forming the surface coating layer 6 is not particularly limited, and examples include a method of applying a resin to form the surface coating layer 6. If an additive is to be blended into the surface coating layer 6, a resin mixed with the additive may be applied.

The thickness of the surface coating layer 6 is not particularly limited as long as it exhibits the above-mentioned functions of the surface coating layer 6, but may be, for example, approximately 0.5 to 10 μm, and preferably approximately 1 to 5 μm.

2. Manufacturing Method of Electricity Storage Device Exterior Material The manufacturing method of the electricity storage device exterior material is not particularly limited as long as it can produce a laminate in which the layers of the electricity storage device exterior material of the present disclosure are laminated, and examples include a method comprising a step of laminating at least a substrate layer 1, a barrier layer 3, an adhesive layer 5, and a heat-sealable resin 4 in this order. As described above, an aluminum alloy foil satisfying the above-mentioned predetermined composition can be used as the barrier layer 3. Furthermore, the adhesive layer 5 is formed from a cured product of a resin composition containing a curable resin.

An example of a manufacturing method for an exterior material for an electricity storage device 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 1, an adhesive layer 2, and a barrier layer 3 are laminated in this order. Specifically, laminate A can be formed by a dry lamination method in which the adhesive used to form adhesive layer 2 is applied to substrate layer 1 or, if necessary, to barrier layer 3 whose surface has been chemically treated, by a coating method such as gravure coating or roll coating, and then dried. After that, the barrier layer 3 or substrate layer 1 is laminated, and the adhesive layer 2 is cured.

Next, a heat-sealable resin layer 4 is laminated on the barrier layer 3 of the laminate A. For example, (1) a method of laminating the adhesive layer 5 and the heat-sealable resin layer 4 by extruding them onto the barrier layer 3 of the laminate A (co-extrusion lamination method, tandem lamination method), (2) a method of separately forming a laminate in which the adhesive layer 5 and the heat-sealable resin layer 4 are laminated, and laminating this on the barrier layer 3 of the laminate A by a thermal lamination method, or a method of forming a laminate in which the adhesive layer 5 is laminated on the barrier layer 3 of the laminate A, and laminating this on the heat-sealable resin layer 4 by a thermal lamination method, (3) a laminate Examples of such methods include (1) a method in which a molten adhesive layer 5 is poured between the barrier layer 3 of A and a heat-sealable resin layer 4 that has been pre-formed into a sheet, and the laminate A and the heat-sealable resin layer 4 are bonded together via the adhesive layer 5 (sandwich lamination method); and (4) a method in which an adhesive for forming the adhesive layer 5 is solution-coated onto the barrier layer 3 of the laminate A, followed by drying or baking, and then the heat-sealable resin layer 4 that has been pre-formed into a sheet is laminated onto this adhesive layer 5.

When the surface coating layer 6 is provided, the surface coating layer 6 is laminated on the surface of the base layer 1 opposite the barrier layer 3. The surface coating layer 6 can be formed, for example, by applying the above-mentioned resin that forms the surface coating layer 6 to the surface of the base layer 1. The order of the step of laminating the barrier layer 3 on the surface of the base layer 1 and the step of laminating the surface coating layer 6 on the surface of the base layer 1 is not particularly limited. For example, after the surface coating layer 6 is formed on the surface of the base layer 1, the barrier layer 3 may be formed on the surface of the base layer 1 opposite the surface coating layer 6.

As described above, a laminate is formed comprising the optional surface coating layer 6, the substrate layer 1, the optional adhesive layer 2, the barrier layer 3, the adhesive layer 5, and the heat-sealable resin layer 4 in this order. To strengthen the adhesion of the optional adhesive layer 2 and adhesive layer 5, the laminate may be further subjected to a heat treatment.

In the packaging material for an electricity storage device, 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 necessary, to improve its processability. For example, corona treatment can be performed on the surface of the base layer 1 opposite the barrier layer 3, thereby improving the printability of ink on the surface of the base layer 1.

The packaging 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, an electrolyte, etc. 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 packaging material for an electricity storage device according to the present disclosure.

Specifically, an electricity storage device using the electricity storage device packaging material of the present disclosure is provided by covering an electricity storage device element having 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 the heat-sealable resin layers of the flange portion are heat-sealed to form 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).

The exterior packaging material for an electricity storage device of the present disclosure can be suitably used for electricity storage devices such as batteries (including condensers, capacitors, etc.). The exterior packaging material for an electricity storage device of the present disclosure may be used for either primary or secondary batteries, but is preferably used for secondary batteries. The type of secondary battery to which the exterior packaging 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, 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, capacitors, and capacitors. Among these secondary batteries, lithium ion batteries and lithium ion polymer batteries are suitable applications for the exterior packaging 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.

<Production of Aluminum Alloy Foil>
Ingots of aluminum alloys having the compositions shown in Table 1 (the balance being Al and other inevitable impurities) were prepared, subjected to homogenization treatment under the conditions shown in the table, and then hot-rolled to a finishing temperature of 330°C to form sheets having a thickness of 3 mm. Subsequently, the ingots were subjected to cold rolling, intermediate annealing, and final cold rolling to produce aluminum alloy foil samples having a thickness of 40 μm and a width of 1200 mm. The method of intermediate annealing is shown in Table 1. The cold rolling item in Table 1 shows the sheet thickness immediately before intermediate annealing and the cold rolling reduction ratio to reach the sheet thickness.

The following tests and measurements were performed on the produced aluminum alloy foil, and the results are shown in Table 1.

Tensile strength and elongation at break of aluminum alloy foil Both the tensile strength and the elongation at break were measured by tensile testing. The tensile test conformed to JIS Z2241:2011. JIS No. 5 test pieces were taken from the samples so that the elongation in the 0° direction relative to the rolling direction could be measured. The test was performed using a universal tensile testing machine (Shimadzu Corporation, AGS-X 10kN) at a tensile speed of 2mm/min. The elongation refers to the elongation at break, and the calculation of the elongation percentage is as follows. First, before the test, two lines were marked in the longitudinal center of the test piece in the direction perpendicular to the test piece, spaced 50mm apart, which is the gauge length. After the test, the fracture surfaces of the aluminum alloy foil were butted together to measure the distance between the marks. The gauge length (50mm) was subtracted from this to obtain the elongation amount (mm), and the elongation percentage (%) was calculated by dividing the elongation amount (mm) by the gauge length (50mm). The elongation of the aluminum alloy foil is the total elongation at break (the sum of the elastic elongation and plastic elongation of the extensometer) and is expressed as a percentage of the extensometer gauge length.

Average grain size The surface of the aluminum alloy foil was electropolished using a mixed solution of 20% by volume perchloric acid and 80% by volume ethanol at a voltage of 20 V, and then anodized in Barker's solution at a voltage of 30 V. The grains of the treated specimen were observed using an optical microscope. The average grain size was calculated from the photographs taken using the intercept method.

L1 (HAGB length) / L2 (LAGB length)
After electrolytic polishing of the foil surface, crystal orientation analysis was performed using SEM-EBSD to observe high-angle grain boundaries (HAGBs) with a misorientation between crystal grains of 15° or more and small-angle grain boundaries with a misorientation of 2° to 15°. Four fields of view, each with a field size of 170 × 340 μm, were measured at a magnification of 500x, and the lengths of the HAGBs and LAGBs within the fields of view were determined, and the ratio was calculated. The calculated ratio is shown in Table 2 as L1/L2.

Crystal orientation: The representative orientations were {112}<111> for the Copper orientation and {123}<634> for the R orientation. The orientation density of each orientation was obtained by measuring the incomplete pole figures of {111}, {200}, and {220} using X-ray diffraction, and then using the results to calculate the crystal orientation distribution function (ODF).

Surface analysis The Mg concentration on the foil surface was estimated using X-ray Photoelectron Spectroscopy (XPS). The narrow spectrum obtained by narrow scan measurement was subjected to waveform separation, and the atomic concentration of each element was quantified. For Mg, the Mg2p spectrum was used. The XPS equipment used was an ULVAC-PHI Quantera SMX. The analysis conditions were an X-ray source of 100 W, pass energy of 26 eV, step of 0.05 eV, analysis area (beam diameter) of 100 μm × 1.4 mm, and detection angle of 45°.

- Oxide film thickness measurement The oxide film thickness was measured using an FE-EPMA (Electron Probe Micro Analyzer) rather than XPS. The oxide film thickness of the sample was calculated using a calibration curve of X-ray intensity obtained from an oxide film sample with a known thickness. The FE-EPMA used was a JXA-8530F manufactured by JEOL Ltd. The analysis conditions were an acceleration voltage of 10 kV, a probe current of 100 nA, and a beam diameter of 50 μm.

- Puncture strength A needle with a diameter of 1.0 mm and a tip radius of 0.5 mm was pierced into an aluminum alloy foil with a thickness of 40 μm at a speed of 50 mm/min, and the maximum load (N) until the needle penetrated the foil was measured. Here, a piercing strength of 9.0 N or more was considered to have good piercing resistance and was evaluated as ◯, and a piercing strength of less than 9.0 N was evaluated as ×.

Limit Forming Height: The forming height was evaluated in a square tube forming test. The test was performed using a universal sheet metal forming tester (Model 142/20 manufactured by ERICHSEN) and a square punch (side length D = 37 mm, corner chamfer diameter R = 4.5 mm) with a 40 μm thick aluminum alloy foil having the shape shown in Figure 8 (side length D = 37 mm, corner chamfer diameter R = 4.5 mm). The test conditions were a wrinkle suppression force of 10 kN, a scale of 1 for the punch rising speed (forming speed), and mineral oil applied as a lubricant to one side of the foil (the surface that the punch contacts). The foil was formed by the punch rising from the bottom of the device. The maximum punch rising height that could be formed without cracks or pinholes after three consecutive forming runs was defined as the limit forming height (mm) for that material. The punch height was varied in 0.5 mm increments. Here, a protrusion height of 7.0 mm or more was considered good formability and rated as ○, while a protrusion height of less than 7.0 mm was rated as ×.

Corrosion Evaluation: 152 g of lithium hexafluorophosphate was dissolved in 1 L of propylene carbonate/diethylene carbonate (volume ratio: 1/1) to prepare a 1 mol/L electrolyte. Next, each aluminum alloy foil used in the Examples and Comparative Examples was placed on the positive electrode of a 200 mL bipolar beaker cell, metallic lithium was placed on the negative electrode, and the aforementioned electrolyte was added. A potential difference of 0.1 V was applied for 1 hour and 3 hours, and the surface of the aluminum alloy foil was then visually observed under a microscope. As shown in the micrographs (observation magnification: 200x) in Figures 6 and 7, samples with corroded surfaces (Figure 7) were rated as ×, and samples without change (Figure 6) were rated as ○. Samples with only partial surface change were rated as △, indicating that they were practically acceptable but had slightly poor corrosion resistance. The corroded aluminum alloy foil surface (rated as ×) was observed to have formed a compound with lithium, resulting in a raised surface due to volume expansion. The results for each test material are shown in Table 2.

<Manufacturing of exterior materials for electricity storage devices>
(Example 1 and Comparative Examples 1 and 2)
A laminate film was prepared as a substrate layer, in which a polyethylene terephthalate film (12 μm) / an adhesive layer (a two-component curing urethane adhesive (a polyol compound and an aromatic isocyanate compound), thickness 3 μm) / a biaxially oriented nylon film (thickness 15 μm) were laminated in this order. Next, a barrier layer consisting of the aluminum alloy foil (having the composition shown in Table 1 and a thickness of 40 μm) with acid-resistant coatings formed on both sides was laminated on the biaxially oriented nylon film (thickness 15 μm) as the substrate layer by dry lamination. Specifically, a two-component curing urethane adhesive (a polyol compound and an aromatic isocyanate compound) was applied to one side of an aluminum alloy foil with acid-resistant coatings (a coating formed by chromate treatment with a chromium content of 30 mg/ ^m2 ) formed on both sides, to form an adhesive layer (thickness 3 μm after curing) on the aluminum alloy foil. Next, the adhesive layer on the aluminum alloy foil and the biaxially oriented nylon film were laminated, and then aging treatment was performed to produce a substrate layer/adhesive layer/barrier layer laminate.

Next, an unstretched polypropylene film (80 μm thick) was laminated onto the barrier layer of the resulting laminate using the dry lamination method. Specifically, a two-component curing adhesive (acid-modified polypropylene and epoxy compound) was applied to form an adhesive layer (2 μm thick after curing) on the aluminum alloy foil. An aging treatment was then performed to obtain an exterior material for an electricity storage device, laminated in the following order: polyethylene terephthalate film (12 μm) / adhesive layer (3 μm) / biaxially oriented nylon film (15 μm) / adhesive layer (3 μm) / barrier layer (40 μm) / adhesive layer (2 μm) / heat-sealable resin layer (80 μm).

Example 2
A polyethylene terephthalate film (25 μm) was prepared as a substrate layer. Next, a barrier layer consisting of the aluminum alloy foil (having the composition shown in Table 1 and a thickness of 40 μm) with acid-resistant coatings formed on both sides was laminated on the substrate layer by dry lamination. Specifically, a two-component curing urethane adhesive (a polyol compound and an aromatic isocyanate compound) was applied to one side of the aluminum alloy foil with acid-resistant coatings (a coating formed by chromate treatment with a chromium content of 30 mg/ ^m2 ) formed on both sides, forming an adhesive layer (thickness of 3 μm after curing) on the aluminum alloy foil. The adhesive layer on the aluminum alloy foil and the substrate layer were then laminated, followed by aging treatment, to produce a substrate layer/adhesive layer/barrier layer laminate.

Next, an unstretched polybutylene terephthalate film (50 μm thick) was laminated onto the barrier layer of the resulting laminate using the dry lamination method. Specifically, a two-component curing adhesive (acid-modified polypropylene and epoxy compound) was applied to form an adhesive layer (3 μm thick after curing) on the aluminum alloy foil. An aging treatment was then performed to obtain an exterior material for an electricity storage device, laminated in the following order: polyethylene terephthalate film (25 μm), adhesive layer (3 μm), barrier layer (40 μm), adhesive layer (3 μm), and polybutylene terephthalate film (50 μm).

Example 3
A laminate film was prepared as a substrate layer, in which a polyethylene terephthalate film (12 μm) / an adhesive layer (a two-component curing urethane adhesive (a polyol compound and an aromatic isocyanate compound), thickness 3 μm) / a biaxially oriented nylon film (thickness 15 μm) were laminated in this order. Next, a barrier layer consisting of the aluminum alloy foil (having the composition shown in Table 1 and a thickness of 40 μm) with acid-resistant coatings formed on both sides was laminated on the biaxially oriented nylon film (thickness 15 μm) as the substrate layer by dry lamination. Specifically, a two-component curing urethane adhesive (a polyol compound and an aromatic isocyanate compound) was applied to one side of an aluminum alloy foil with acid-resistant coatings (a coating formed by chromate treatment with a chromium content of 30 mg/ ^m2 ) formed on both sides, to form an adhesive layer (thickness 3 μm after curing) on the aluminum alloy foil. Next, the adhesive layer on the aluminum alloy foil and the biaxially oriented nylon film were laminated, and then aging treatment was performed to produce a substrate layer/adhesive layer/barrier layer laminate.

Next, an unstretched polypropylene film (80 μm thick) was laminated onto the barrier layer of the resulting laminate using the dry lamination method. Specifically, a two-component curing adhesive (polyester polyol compound and alicyclic isocyanate compound) was applied to form an adhesive layer (2 μm thick after curing) on the aluminum alloy foil. An aging treatment was then performed to obtain an exterior packaging material for an electricity storage device, laminated in the following order: polyethylene terephthalate film (12 μm) / adhesive layer (3 μm) / biaxially oriented nylon film (15 μm) / adhesive layer (3 μm) / barrier layer (40 μm) / adhesive layer (2 μm) / heat-sealable resin layer (80 μm).

(Comparative Example 3)
A laminate film was prepared as a substrate layer, in which a polyethylene terephthalate film (12 μm) / an adhesive layer (a two-component curing urethane adhesive (a polyol compound and an aromatic isocyanate compound), thickness 3 μm) / a biaxially oriented nylon film (thickness 15 μm) were laminated in this order. Next, a barrier layer consisting of the aluminum alloy foil (having the composition shown in Table 1 and a thickness of 40 μm) with acid-resistant coatings formed on both sides was laminated on the biaxially oriented nylon film (thickness 15 μm) as the substrate layer by dry lamination. Specifically, a two-component curing urethane adhesive (a polyol compound and an aromatic isocyanate compound) was applied to one side of an aluminum alloy foil with acid-resistant coatings (a coating formed by chromate treatment with a chromium content of 30 mg/ ^m2 ) formed on both sides, to form an adhesive layer (thickness 3 μm after curing) on the aluminum alloy foil. Next, the adhesive layer on the aluminum alloy foil and the biaxially oriented nylon film were laminated, and then aging treatment was performed to produce a substrate layer/adhesive layer/barrier layer laminate.

Next, maleic anhydride-modified polypropylene (40 μm thick) as an adhesive layer and polypropylene (40 μm thick) as a heat-sealable resin layer were co-extruded onto the barrier layer of the resulting laminate, thereby laminating an adhesive layer/heat-sealable resin layer onto the barrier layer. The resulting laminate was then aged and heated to obtain an exterior packaging material for an electricity storage device, laminated in the following order: polyethylene terephthalate film (12 μm)/adhesive layer (3 μm)/biaxially oriented nylon film (15 μm)/adhesive layer (3 μm)/barrier layer (40 μm)/adhesive layer (40 μm)/heat-sealable resin layer (40 μm).

In addition, erucic acid amide was present as a lubricant on both sides of the exterior material for an electricity storage device to form a lubricant layer.

<Evaluation of corrosion resistance of aluminum alloy foil to electrolyte>
Each aluminum alloy foil used in the examples and comparative examples was cut into a rectangle measuring 45 mm long and 15 mm wide. Next, rectangular polyethylene films measuring 50 mm long and 20 mm wide were attached and heat-welded to the front and back surfaces of the aluminum alloy foil, leaving a 1 cm diameter exposed portion on one side of the foil. These films were then used to prepare test samples. The corrosion resistance of the test samples was evaluated using the 1 cm diameter portion of the aluminum alloy foil AL, while the end of the test sample not immersed in the electrolyte was left exposed for connection to the working electrode. Next, as shown in the schematic diagram of FIG. 4, the test sample AL was set as the working electrode, and metallic lithium Li (disk-shaped, 15 mm diameter x 0.35 mm thick) was set as the counter electrode. The test samples were then immersed in an electrolyte _consisting of 1 mol/L LiPF6 and a mixture of ethylene carbonate, diethyl carbonate, and dimethyl carbonate (volume ratio 1:1:1). In this state, a voltage of 0.1 V was applied for 1 hour in an environment of 20°C, and then the surface of the aluminum alloy foil was observed. Surfaces corroded as shown in Figure 7 were rated C, and surfaces unchanged as shown in Figure 6 were rated A, and the results are shown in Table 2. It was observed that compounds with lithium were formed on the corroded aluminum alloy foil surface, and the surface was raised due to volume expansion.

<Corrosion resistance of aluminum alloy foil against all-solid-state electrolytes>
In a glove box, a solid electrolyte (Li2S-P2S5 (75:25)) with a thickness of 800 μm and a diameter of 10 mm was prepared by powder compaction. Next, indium foil (thickness 0.3 mm, diameter 9 mm), lithium foil (thickness 0.2 mm, diameter 8 mm), and indium foil (thickness 0.1 mm, diameter 9 mm) were placed on top of the solid electrolyte, with the indium foil (thickness 0.1 mm) facing the solid electrolyte side, and the foil was restrained and left overnight. Thereafter, the restraint was released, and each aluminum alloy foil used in the examples and comparative examples was punched out to a diameter of 9 mm and laminated on the solid electrolyte on the side opposite the foil. The resulting laminate was restrained and sealed in a glass cell with leads. The laminate was removed from the glove box and left for 1 hour to stabilize. In this state, a voltage of -0.53 V was applied for 3 hours in an environment of 25°C, and the amount of electricity per unit area was calculated. When the amount of electricity was less than 4 C/cm ^2, it was evaluated as A, and when it was 4 C/cm ² or more, it was evaluated as C. The results are shown in Table 3.

<Evaluation of formability>
Each of the electrical storage device packaging materials obtained above was cut into a rectangle with a length (MD) of 90 mm and a width (TD) of 150 mm to prepare a test sample. The MD of the electrical storage device packaging material corresponds to the rolling direction (RD) of the aluminum alloy foil, and the TD of the electrical storage device packaging material corresponds to the TD of the aluminum alloy foil. The test sample was placed in an environment of 25°C in a forming mold (female mold, the surface of which had a maximum height roughness (nominal value of Rz) of 3.2 μm, corner R2.0 mm, ridge R1.0 mm, as specified in Table 2 of the comparative surface roughness standard piece in JIS B 0659-1:2002 Annex 1 (Reference)) with a rectangular opening of 31.6 mm (MD) x 54.5 mm (TD). The corresponding forming mold (male mold, the surface of which had a maximum height roughness (nominal value of Rz) of 3.2 μm, corner R2.0 mm, ridge R1.0 mm, as specified in Table 2 of the comparative surface roughness standard piece in JIS B 0659-1:2002 Annex 1 (Reference)) was placed in an environment of 25°C. The maximum height roughness (nominal Rz value) of the comparative surface roughness standard specimen, as specified in Table 2, is 1.6 μm. Using a corner R of 2.0 mm and a ridge R of 1.0 mm, a pressing pressure (surface pressure) of 0.25 MPa was applied to ten samples, varying the forming depth from 0.5 mm in 0.5 mm increments. The test samples were placed on a female mold so that the heat-fusible resin layer was positioned on the male mold side. The clearance between the male and female molds was 0.3 mm. After cold forming, the samples were illuminated with a penlight in a darkroom to check for pinholes or cracks in the aluminum alloy foil. The deepest forming depth at which no pinholes or cracks occurred in the aluminum alloy foil in any of the ten samples was defined as the limit forming depth P mm. When the limit forming depth was 4.0 mm or more, it was evaluated as A, when it was 3.5 mm, it was evaluated as B, and when it was 3.0 mm or less, it was evaluated as C. The results are shown in Table 3.

<Insulation evaluation>
Each of the electrical storage device packaging materials obtained in the Examples and Comparative Examples was cut to a length (MD) of 100 mm and a width (TD) of 40 mm. Additionally, an aluminum plate measuring 100 mm x 30 mm and 1 mm thick was prepared, and a φ50 μm aluminum wire was fixed to the aluminum plate with double-sided tape. The positive electrode of a megaohm tester (HIOKI 3154 DIGITAL MΩ HiTESTER) was contacted with the aluminum plate, and the negative electrode was connected so that the jig contacted the barrier layer of the electrical storage device packaging material. The heat-sealable resin layer side of the electrical storage device packaging material was placed on the wire side of the aluminum plate. In this state, a 7 mm wide seal bar was used to heat seal the exterior material for an electricity storage device from above (sealing conditions: 190°C, 0.1 MPa), and the time until the heat-sealing resin layer bit into the wire, the wire reached the barrier layer, and the resistance between the exterior material for an electricity storage device and the aluminum plate reached 200 MΩ or less at 100 V was measured. A time of 15 seconds or more was assigned an A rating, and a time of less than 15 seconds was assigned an C rating. The results are shown in Table 3.

In Table 3, acid-modified PP refers to acid-modified polypropylene.

The electrical storage device packaging materials of Examples 1 to 3 are composed of a laminate having at least a base layer, a barrier layer, and a heat-sealable resin layer, in this order. The barrier layer contains aluminum alloy foil with a composition of Fe: 0.2% by mass to 2.0% by mass and Mg: 0.1% by mass to 5.0% by mass, and the adhesive layer is formed from a cured product of a resin composition containing a curable resin. The electrical storage device packaging materials of Examples 1 to 3 have excellent formability, effectively suppress corrosion of the aluminum alloy foil when electricity is applied with electrolyte attached, and also have enhanced insulation properties.

As described above, the present disclosure provides the following aspects of the invention.
Item 1. The laminate is composed of at least a base layer, a barrier layer, an adhesive layer, and a heat-sealable resin layer in this order,
the barrier layer includes an aluminum alloy foil having a composition of Fe: 0.2 mass% or more and 2.0 mass% or less, and Mg: 0.1 mass% or more and 5.0 mass% or less,
The adhesive layer is formed from a cured product of a resin composition containing a curable resin.
Item 2. The packaging material for an electricity storage device according to Item 1, wherein the aluminum alloy foil has a composition satisfying Mn: 0.1 mass % or less.
Item 3. The exterior packaging material for an electricity storage device according to Item 1 or 2, wherein the aluminum alloy foil has a tensile strength of 100 MPa or more and a breaking elongation of 10% or more, as measured using a JIS No. 5 test piece in accordance with JIS Z2241:2011.
Item 4. The exterior packaging material for a storage battery device according to any one of Items 1 to 3, wherein the adhesive layer is formed from a cured product of a resin composition containing an acid-modified polyolefin and a curing agent.
Item 5. The electrical storage device packaging material according to any one of Items 1 to 3, wherein the adhesive layer is formed from a cured product of a resin composition containing at least one of polyester and polycarbonate, and at least one of an alicyclic isocyanate compound and an aromatic isocyanate compound.
Item 6. The packaging material for an electricity storage device according to any one of Items 1 to 5, wherein the base material layer contains polyester.
Item 7. The packaging material for an electricity storage device according to any one of Items 1 to 6, wherein the heat-sealable resin layer contains polyester.
Item 8. The packaging material for an electricity storage device according to any one of Items 1 to 7, wherein the aluminum alloy foil has a composition of Si: 0.5 mass% or less.
Item 9.
Item 9. The aluminum alloy foil has a ratio of the length L1 of a high-angle grain boundary to the length L2 of a low-angle grain boundary per unit area measured by electron backscatter diffraction (EBSD) satisfying the relationship L1/L2>3.0. Item 9. An exterior material for an electricity storage device according to any one of items 1 to 8.
Item 10. The composition of the aluminum alloy foil satisfies Mg: 0.1 mass% or more and 1.5 mass% or less,
Item 10. The aluminum alloy foil according to Item 9, wherein at least one surface of the aluminum alloy foil contains 5.0 atomic percent or more of Mg, and at least one surface of the aluminum alloy foil has an oxide film having a thickness of 80 Å or more.
Item 11. The composition of the aluminum alloy foil satisfies Mg: 0.1 mass% or more and 1.5 mass% or less,
Item 11. The exterior packaging material for a power storage device according to Item 9 or 10, wherein the aluminum alloy foil has a tensile strength of 110 MPa or more and 180 MPa or less and a breaking elongation of 10% or more.
Item 12. The composition of the aluminum alloy foil satisfies Mg: more than 1.5 mass% and 5.0 mass% or less,
Item 10. The aluminum alloy foil according to Item 9, wherein at least one surface of the aluminum alloy foil contains 15.0 atomic percent or more of Mg, and at least one surface of the aluminum alloy foil has an oxide film having a thickness of 120 Å or more.
Item 13. The composition of the aluminum alloy foil satisfies Mg: more than 1.5 mass% and 5.0 mass% or less,
Item 13. The exterior packaging material for a storage battery device according to Item 9 or 12, wherein the aluminum alloy foil has a tensile strength of 180 MPa or more and an elongation at break of 15% or more.
Item 14. The exterior packaging material for an electricity storage device according to any one of Items 9 to 13, wherein the aluminum alloy foil has a texture in which the orientation densities of the Copper orientation and the R orientation are each 15 or less.
Item 15. The packaging material for an electricity storage device according to any one of Items 9 to 14, wherein the aluminum alloy foil has an average crystal grain size of 25 μm or less.
Item 16. The packaging material for an electricity storage device according to any one of Items 9 to 15, wherein the aluminum alloy foil has a composition in which unavoidable impurities include Mn: 0.1 mass% or less.
Item 17. The packaging material for an electricity storage device according to any one of Items 9 to 16, wherein the aluminum alloy foil has a composition satisfying Si: 0.5 mass% or less.
Item 18. 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 1 to 17.
Item 19. The method includes a step of laminating at least a base layer, a barrier layer, and a heat-sealable resin layer in this order to obtain a laminate,
the barrier layer includes an aluminum alloy foil having a composition of Fe: 0.2 mass% or more and 2.0 mass% or less, and Mg: 0.1 mass% or more and 5.0 mass% or less,
The method for producing an exterior material for an electricity storage device, wherein the adhesive layer is formed from a cured product of a resin composition containing a curable resin.

REFERENCE SIGNS LIST 1 Base material layer 2 Adhesive layer 3 Barrier layer 4 Heat-sealable resin layer 5 Adhesive layer 6 Surface coating layer 10 Electricity storage device packaging material

Claims (19)

The laminate is composed of at least a base layer, a barrier layer, an adhesive layer, and a heat-sealable resin layer in this order,
the barrier layer contains an aluminum alloy foil that satisfies a composition of Fe: 1.0% by mass or more and 2.0% by mass or less, Mg: 0.1% by mass or more and 5.0% by mass or less, and inevitable impurities each being 0.10% by mass or less and totaling 0.40% by mass or less ;
The adhesive layer is formed from a cured product of a resin composition containing a curable resin. The exterior packaging material for an electricity storage device according to claim 1, wherein the aluminum alloy foil has a composition satisfying Mn: 0.1% by mass or less. The exterior packaging material for an electricity storage device according to claim 1 or 2, wherein the aluminum alloy foil has a tensile strength of 100 MPa or more and a breaking elongation of 10% or more, as measured using a JIS No. 5 test piece in accordance with JIS Z2241:2011. The electrical storage device packaging material according to any one of claims 1 to 3, wherein the adhesive layer is formed from a cured resin composition containing an acid-modified polyolefin and a curing agent. The electrical storage device packaging material according to any one of claims 1 to 3, wherein the adhesive layer is formed from a cured resin composition containing at least one of polyester and polycarbonate, and at least one of an alicyclic isocyanate compound and an aromatic isocyanate compound. The exterior packaging material for an electricity storage device according to any one of claims 1 to 5, wherein the base layer contains polyester. The packaging material for an electricity storage device according to any one of claims 1 to 6, wherein the heat-sealable resin layer contains polyester. The exterior packaging material for an electricity storage device according to any one of claims 1 to 7, wherein the aluminum alloy foil has a composition of Si: 0.5 mass% or less. The exterior material for an electricity storage device according to any one of claims 1 to 8, wherein the ratio of the length L1 of the high-angle grain boundaries to the length L2 of the low-angle grain boundaries per unit area measured by electron backscatter diffraction satisfies the relationship L1/L2 > 3.0. The composition of the aluminum alloy foil satisfies Mg: 0.1 mass% or more and 1.5 mass% or less,
10. The exterior packaging material for an electricity storage device according to claim 9, wherein at least one surface of the aluminum alloy foil contains 5.0 atomic percent or more of Mg, and at least one surface of the aluminum alloy foil has an oxide film having a thickness of 80 Å or more. The composition of the aluminum alloy foil satisfies Mg: 0.1 mass% or more and 1.5 mass% or less,
The packaging material for an electricity storage device according to claim 9 or 10, wherein the aluminum alloy foil has a tensile strength of 110 MPa or more and 180 MPa or less and an elongation at break of 10% or more. The composition of the aluminum alloy foil satisfies Mg: more than 1.5 mass% and not more than 5.0 mass%,
At least one surface of the aluminum alloy foil is coated with 15.0 atomic percent or more of Mg
and an oxide film having a thickness of 120 Å or more on at least one surface of the aluminum alloy foil. The composition of the aluminum alloy foil satisfies Mg: more than 1.5 mass% and not more than 5.0 mass%,
The packaging material for an electricity storage device according to claim 9 or 12, wherein the aluminum alloy foil has a tensile strength of 180 MPa or more and an elongation at break of 15% or more. The exterior packaging material for an electricity storage device according to any one of claims 9 to 13, wherein the aluminum alloy foil has a texture in which the orientation densities of the Copper orientation and the R orientation are each 15 or less. The exterior packaging material for an electricity storage device according to any one of claims 9 to 14, wherein the aluminum alloy foil has an average crystal grain size of 25 μm or less. The exterior packaging material for an electricity storage device according to any one of claims 9 to 15, wherein the aluminum alloy foil has a composition in which unavoidable impurities include Mn: 0.1 mass% or less. The exterior packaging material for an electricity storage device according to any one of claims 9 to 16, wherein the aluminum alloy foil has a composition containing Si: 0.5 mass% or less. An electricity storage device in which an electricity storage device element having 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 claims 1 to 17. The method includes a step of laminating at least a base layer, a barrier layer, an adhesive layer, and a heat-sealable resin layer in this order to obtain a laminate,
the barrier layer contains an aluminum alloy foil that satisfies a composition of Fe: 1.0% by mass or more and 2.0% by mass or less, Mg: 0.1% by mass or more and 5.0% by mass or less, and inevitable impurities each being 0.10% by mass or less and totaling 0.40% by mass or less ;
The method for producing an exterior material for an electricity storage device, wherein the adhesive layer is formed from a cured product of a resin composition containing a curable resin.