JP7675154B2 - Exterior material for power storage device and power storage device - Google Patents

Description

The present invention relates to exterior materials for electricity storage devices, such as batteries and capacitors used in mobile devices such as smartphones and tablets, and batteries and capacitors used for storing electricity in hybrid vehicles, electric vehicles, wind power generation, solar power generation, and nighttime electricity, and to electricity storage devices.

In this specification and claims, the term "tensile yield strength" refers to the tensile yield strength (tensile yield strength) obtained by measuring in accordance with JIS K7127-1999 (tensile test method) under conditions of a sample width of 15 mm, a gauge length of 50 mm, and a tensile speed of 100 mm/min.

Lithium ion secondary batteries are widely used as power sources for devices such as notebook computers, video cameras, and mobile phones. These lithium ion secondary batteries are constructed with a battery body (body including a positive electrode, a negative electrode, and an electrolyte) surrounded by a case. A known case material (exterior material) is one in which an outer layer made of a heat-resistant resin film, an aluminum foil layer, and an inner layer made of a thermoplastic resin film are bonded together in this order (see Patent Document 1).

The electricity storage device is constructed by sandwiching the electricity storage device body between a pair of exterior materials and sealing the peripheral edges of the pair of exterior materials by fusion bonding (heat sealing). By providing sufficient sealing by such heat sealing, leakage of the electrolyte can be prevented.

JP 2005-22336 A

However, batteries such as lithium-ion secondary batteries are intended for use in normal temperature environments such as notebook computers and mobile phones.

However, in recent years, as the uses of such lithium-ion secondary batteries have become more diverse, new applications in which they are used outdoors in high-temperature environments, such as in automobiles, are also on the rise.

For example, when used in automobiles, the temperature of an automobile can reach a considerable level when parked outdoors during the summer. Therefore, there is a need to develop an exterior material that can maintain good sealing performance of the seals of the exterior material even when exposed to such high-temperature environments for long periods of time, even for batteries such as lithium-ion secondary batteries.

The present invention has been made in consideration of this technical background, and aims to provide an exterior material for an electricity storage device and an electricity storage device that can maintain good sealing performance of the sealing part of the exterior material even when exposed to a high-temperature environment for a long period of time.

To achieve the above objective, the present invention provides the following means:

[1] An exterior material for an electricity storage device, comprising a heat-resistant resin layer as an outer layer, a sealant layer as an inner layer, and a metal foil layer disposed between these layers,
The sealant layer is composed of one or more layers, and at least the innermost layer of the sealant layer contains an elastomer-modified olefin-based resin,
The elastomer-modified olefin-based resin comprises an olefin-based thermoplastic elastomer-modified homopolypropylene and/or an olefin-based thermoplastic elastomer-modified random copolymer,
The olefin-based thermoplastic elastomer modified random copolymer is an olefin-based thermoplastic elastomer modified random copolymer containing propylene and other copolymer components other than propylene as copolymer components, characterized in that it is an exterior material for a storage battery device.

[2] The exterior material for a storage battery device according to the preceding paragraph 1, in which the content of the olefin-based thermoplastic elastomer in the innermost layer is 0.1% by mass or more and less than 20% by mass.

[3] The exterior material for a storage battery device according to the preceding paragraphs 1 or 2, in which the melting point of the elastomer-modified olefin resin constituting the innermost layer is higher than 160°C.

[4] The exterior material for a storage battery device according to any one of items 1 to 3 above, wherein the sealant film constituting the sealant layer has a tensile yield strength at 80°C of 3.5 MPa to 15.0 MPa.

[5] The exterior material for a storage battery device according to any one of the preceding paragraphs 1 to 4, characterized in that the sealant layer is made of multiple layers, a second sealant layer is disposed on the side of the sealant layer closest to the metal foil layer, and the second sealant layer contains 50% by mass or more of a propylene-ethylene random copolymer and does not contain an elastomer component.

[6] The exterior material for an electricity storage device according to any one of items 1 to 5 above, in which the metal foil layer and the sealant layer are bonded via an adhesive layer.

[7] The exterior material for a storage battery device according to the preceding paragraph 6, wherein the adhesive layer is made of an adhesive containing an olefin resin having a carboxyl group and a polyfunctional isocyanate compound.

[8] A main body of an electricity storage device;
The electrical storage device packaging material according to any one of items 1 to 7,
A power storage device, characterized in that the power storage device main body is exteriorly covered with the exterior material.

In the invention of [1], at least the innermost layer of the sealant layer of the exterior material contains the above-mentioned specific elastomer-modified olefin-based resin, so that the initial seal strength between the exterior materials can be sufficiently secured even in a high-temperature environment, and sufficient seal strength can be maintained even when the exterior materials are left in a high-temperature environment (for example, inside a car in summer) for a long period of time.

In the invention of [2], the content of the olefin-based thermoplastic elastomer in the innermost layer of the sealant layer is 0.1% by mass or more and less than 20% by mass, so that the film strength of the sealant layer is increased, making the sealant layer less susceptible to destruction (breakage).

In the invention of [3], the melting point of the elastomer-modified olefin resin constituting the innermost layer of the sealant layer is higher than 160°C, so that outflow of the sealant layer can be sufficiently suppressed when the exterior material is heat-sealed, and the heat resistance is also excellent in the high-temperature environment.

In the invention of [4], a sealant film having a tensile yield strength of 3.5 MPa to 15.0 MPa at 80°C is used for the sealant layer, so that even if the electricity storage device is used in a high-temperature environment (for example, inside a car in summer) for a long period of time, the exterior material can be prevented from bursting due to an increase in internal pressure.

In the invention [5], the second sealant layer closest to the metal foil layer contains 50% by mass or more of propylene-ethylene random copolymer and does not contain an elastomer component, so that adhesion to the metal foil layer is improved and delamination is unlikely to occur even if deformation occurs. Furthermore, because the second sealant layer closest to the metal foil layer does not contain an elastomer component, there is no penetration of electrolyte into the vicinity of the metal foil layer due to crazes (interface separation without cracks or gaps) that may occur at the interface between the propylene-ethylene random copolymer and the elastomer component, and sufficient insulation can be ensured.

In the invention [6], the interlayer adhesive strength between the metal foil layer and the sealant layer can be further increased.

In the invention of [7], the adhesive layer is made of an adhesive containing an olefin resin having a carboxyl group and a polyfunctional isocyanate compound, so that the electrolyte resistance can be further improved.

The invention [8] provides an electricity storage device that has excellent high-temperature durability and is exterior-wrapped with an exterior material that can ensure sufficient initial seal strength between exterior materials even in a high-temperature environment and can maintain sufficient seal strength even when placed in a high-temperature environment (e.g., inside a car in summer) for a long period of time.

1 is a cross-sectional view showing one embodiment of an exterior material for an electricity storage device according to the present invention. FIG. 3 is a cross-sectional view showing another embodiment of an exterior material for an electricity storage device according to the present invention. 1 is a cross-sectional view showing one embodiment of an electricity storage device according to the present invention. 4 is a perspective view showing the exterior material (planar), the main body of the electricity storage device, and the exterior case (a molded body molded into a three-dimensional shape) constituting the electricity storage device of FIG. 3 in a separated state before being heat-sealed. FIG.

One embodiment of the exterior material 1 for an electricity storage device according to the present invention is shown in FIG. 1. This exterior material 1 for an electricity storage device is used, for example, as an exterior material for a lithium ion secondary battery. The exterior material 1 for an electricity storage device may be used as an exterior material as is without being subjected to molding, or may be used as an exterior case 10 after being subjected to molding such as deep drawing or stretch molding (see FIG. 4).

The exterior material 1 for the electric storage device is configured such that a base material layer (outer layer) 2 is laminated and integrated onto one side of a metal foil layer 4 via a first adhesive layer 5, and an inner sealant layer (inner layer) 3 is laminated and integrated onto the other side of the metal foil layer 4 via a second adhesive layer 6 (see Figures 1 and 2).

In the exterior material 1 of FIG. 1, the inner sealant layer (inner layer) 3 is composed of a single layer (one layer) consisting of the first sealant layer 7. Therefore, the first sealant layer 7 is disposed on the innermost side (the first sealant layer 7 is the innermost layer).

In addition, in the exterior material 1 of FIG. 2, the inner sealant layer (inner layer) 3 has a two-layer laminate structure consisting of a first sealant layer 7, which is the innermost layer, and a second sealant layer 8, which is arranged closest to the metal foil layer 4, with the first sealant layer 7 being arranged on the innermost side.

In the present invention, the inner sealant layer (inner layer) 3 has the function of providing excellent chemical resistance against highly corrosive electrolytes used in lithium ion secondary batteries and the like, and also imparting heat sealability to the exterior material. The sealant layer (inner layer) 3 is made of a non-stretchable sealant film.

In the present invention, the sealant layer (inner layer) 3 may be formed of one layer or two or more layers, but at least the innermost layer (first sealant layer) 7 of the sealant layer (inner layer) 3 contains an elastomer-modified olefin-based resin.

The elastomer-modified olefin resin (polypropylene block copolymer) is preferably made of an olefin thermoplastic elastomer-modified homopolypropylene or/and an olefin thermoplastic elastomer-modified random copolymer, and the olefin thermoplastic elastomer-modified random copolymer is an olefin thermoplastic elastomer-modified random copolymer containing "propylene" and "other copolymer components other than propylene" as copolymer components, and the "other copolymer components other than propylene" are not particularly limited, but examples thereof include olefin components such as ethylene, 1-butene, 1-hexene, 1-pentene, 4-methyl-1-pentene, and butadiene. The olefin thermoplastic elastomer is not particularly limited, but examples thereof include EPR (ethylene propylene rubber), propylene-butene elastomer, propylene-butene-ethylene elastomer, EPDM (ethylene-propylene-diene rubber), and the like, and among them, it is preferable to use EPR (ethylene propylene rubber).

Regarding the elastomer-modified olefin-based resin, the "olefin-based thermoplastic elastomer modification" may be graft polymerization or other modification modes.

The elastomer-modified olefin resin can be produced, for example, by the following reactor-made method. This is merely one example, and the resin is not limited to those produced by this method.

First, a Ziegler-Natta catalyst, a co-catalyst, propylene, and hydrogen are supplied to a first reactor to polymerize homopolypropylene. The obtained homopolypropylene is transferred to a second reactor while containing unreacted propylene and Ziegler-Natta catalyst. In the second reactor, propylene and hydrogen are further added to polymerize homopolypropylene. The obtained homopolypropylene is transferred to a third reactor while containing unreacted propylene and Ziegler-Natta catalyst. In the third reactor, ethylene, propylene, and hydrogen are further added to polymerize ethylene-propylene rubber (EPR) obtained by copolymerizing ethylene and propylene, thereby producing the elastomer-modified olefin-based resin. For example, the elastomer-modified olefin-based resin can be produced by adding a solvent to produce it in the liquid phase, or by carrying out the reaction in the gas phase without using a solvent.

The content of the olefin-based thermoplastic elastomer in the innermost layer (first sealant layer) 7 of the sealant layer 3 is preferably 0.1% by mass or more and less than 20% by mass. In addition, the content of the homopolypropylene (part not modified with the olefin-based thermoplastic elastomer) and/or the random copolymer (part not modified with the olefin-based thermoplastic elastomer) in the innermost layer (first sealant layer) 7 of the sealant layer 3 is preferably 80% by mass or more and 99% by mass or less.

The melting point of the elastomer-modified olefin-based resin constituting the innermost layer (first sealant layer) 7 of the sealant layer 3 is preferably in the range of 160°C to 180°C. This sufficiently prevents the sealant layer 3 from flowing out when the exterior material is heat-sealed, and also has excellent heat resistance in high-temperature environments. In particular, the melting point of the elastomer-modified olefin-based resin constituting the innermost layer (first sealant layer) 7 of the sealant layer 3 is preferably 163°C or higher, and particularly preferably in the range of 163°C to 169°C. The melting point is measured by differential scanning calorimetry (DSC) in accordance with JIS K7121-1987.

The olefin-based thermoplastic elastomer component (this component alone) present in the innermost layer (first sealant layer) 7 preferably has multiple crystallization temperatures. In this way, when it has multiple crystallization temperatures, the effect of making the resin (the olefin-based resin of the innermost layer) less likely to dissolve during adhesion is obtained. In addition, when it has multiple crystallization temperatures, the lowest crystallization temperature among the multiple crystallization temperatures is preferably in the range of 40°C to 80°C, and more preferably in the range of 40°C to 75°C. By having the lowest crystallization temperature be 40°C to 80°C, the effect of being able to shorten the adhesion time at room temperature (adhesion time during heat sealing) is obtained. The crystallization temperature is the crystallization temperature (crystallization peak) measured by differential scanning calorimetry (DSC) in accordance with JIS K7121-1987.

The MFR of the olefin-based thermoplastic elastomer component (this component alone) present in the innermost layer (first sealant layer) 7 is preferably 0.1 g/10 min to 1.4 g/10 min. In this case, the resin (the olefin-based resin of the innermost layer) is less likely to dissolve during heat sealing, so that greater adhesive strength can be ensured. In particular, the MFR of the olefin-based thermoplastic elastomer component (this component alone) present in the innermost layer (first sealant layer) 7 is more preferably 0.1 g/10 min to 1.0 g/10 min, and particularly preferably 0.1 g/10 min to 0.6 g/10 min. The MFR (melt flow rate) is the MFR measured under conditions of 230°C and 2.16 kg in accordance with JIS K7210-1-2014.

The sealant film constituting the sealant layer 3 preferably has a tensile yield strength of 3.5 MPa to 15.0 MPa at 80 ° C. For example, when the sealant layer 3 is composed of only the first sealant layer 7, the tensile yield strength of the first sealant film at 80 ° C. is preferably 3.5 MPa to 15.0 MPa, and when the sealant layer 3 is composed of a laminate of the first sealant layer 7 and the second sealant layer 8, the tensile yield strength of the laminated sealant film at 80 ° C. is preferably 3.5 MPa to 15.0 MPa. The same applies when the sealant layer 3 is a multi-layered structure of three or more layers. In this way, the tensile yield strength of the sealant film constituting the sealant layer 3 at 80 ° C. is 3.5 MPa to 15.0 MPa, so that the rupture of the exterior material due to an increase in internal pressure can be prevented even if the electricity storage device is used in a high-temperature environment (for example, inside a car in summer) for a long period of time. In particular, it is preferable that the sealant film constituting the sealant layer 3 has a tensile yield strength of 4 MPa to 12 MPa at 80°C.

The thickness of the innermost layer (first sealant layer) 7 is preferably 30 μm or more, which has the advantage of improving the toughness of the first sealant layer 7. It is more preferable that the thickness of the innermost layer (first sealant layer) 7 is 30 μm to 100 μm.

When the second sealant layer 8 is provided, the thickness of the second sealant layer 8 is preferably 3 μm to 60 μm, and more preferably 5 μm to 20 μm. When the second sealant layer 8 is provided, the resin forming the second sealant layer 8 is not particularly limited, but examples thereof include propylene-ethylene random copolymer, homopolypropylene, polyethylene, olefin-based thermoplastic elastomer-modified homopolypropylene, and olefin-based thermoplastic elastomer-modified random copolymer (olefin-based thermoplastic elastomer-modified random copolymer containing "propylene" and "other copolymer components other than propylene" as copolymerization components), etc.

The thickness of the sealant layer 3 is preferably set to 30 μm to 200 μm.

In the present invention, the sealant layer 3 is composed of multiple layers, and includes an innermost layer (first sealant layer) 7 containing the elastomer-modified olefin resin and a second sealant layer 8 arranged on the side closest to the metal foil layer 4 (see FIG. 2), and the second sealant layer preferably contains 50% by mass or more of a propylene-ethylene random copolymer and does not contain an elastomer component. When such a configuration is adopted, the second sealant layer 8 on the side closest to the metal foil layer 4 contains 50% by mass or more of a propylene-ethylene random copolymer and does not contain an elastomer component, so that adhesion with the metal foil layer side is improved and interlayer peeling is unlikely to occur even if deformation occurs. Furthermore, since the second sealant layer 8 on the side closest to the metal foil layer 4 does not contain an elastomer component, there is no penetration of the electrolyte into the vicinity of the metal foil layer due to crazes (interface separation without cracks or gaps) that may occur at the interface between the propylene-ethylene random copolymer and the elastomer component, and sufficient insulation can be ensured. Among these, it is more preferable that the second sealant layer contains 70% by mass or more of a propylene-ethylene random copolymer and does not contain an elastomer component. Here, a configuration that does not contain an elastomer component means that an elastomer component is not mixed (blended), and also that an elastomer-modified resin is not mixed.

The sealant film constituting the sealant layer (inner layer) 3 is preferably manufactured by a molding method such as multilayer extrusion molding, inflation molding, or T-die cast film molding.

The method for laminating the sealant film constituting the sealant layer (inner layer) 3 onto the metal foil layer 4 is not particularly limited, but examples include a dry lamination method and a sandwich lamination method (a method in which an adhesive film such as acid-modified polypropylene is extruded, sandwich-laminated between the metal foil and the sealant film, and then heat-laminated with a heated roll).

In the present invention, the base layer (outer layer) 2 is preferably formed of a heat-resistant resin layer. The heat-resistant resin constituting the heat-resistant resin layer 2 is a heat-resistant resin that does not melt at the heat-sealing temperature when the exterior material is heat-sealed. As the heat-resistant resin, it is preferable to use a heat-resistant resin having a melting point 10°C or more higher than the melting point of the sealant layer 3, and it is particularly preferable to use a heat-resistant resin having a melting point 20°C or more higher than the melting point of the sealant layer 3.

The heat-resistant resin layer (outer layer) 2 is not particularly limited, but examples thereof include polyamide films such as nylon films, polyester films, etc., and these stretched films are preferably used. Among them, it is particularly preferable to use biaxially stretched polyamide films such as biaxially stretched nylon films, biaxially stretched polybutylene terephthalate (PBT) films, biaxially stretched polyethylene terephthalate (PET) films, or biaxially stretched polyethylene naphthalate (PEN) films as the heat-resistant resin layer 2. The nylon film is not particularly limited, but examples thereof include nylon 6 film, nylon 6,6 film, and MXD nylon film. The heat-resistant resin layer 2 may be formed as a single layer, or may be formed as a multilayer of polyester film/polyamide film (e.g., a multilayer of PET film/nylon film). In the case of the multilayer, it is preferable to place the polyester film side on the outermost side.

The thickness of the outer layer (base material layer) 2 is preferably 2 μm to 50 μm. When a polyester film is used, the thickness is preferably 5 μm to 40 μm, and when a nylon film is used, the thickness is preferably 15 μm to 50 μm. By setting the thickness to above the above preferred lower limit, sufficient strength as an exterior material can be ensured, and by setting the thickness to below the above preferred upper limit, stress during molding such as stretch molding and drawing can be reduced, improving moldability.

In the exterior material for an electric storage device according to the present invention, the metal foil layer 4 serves to impart gas barrier properties to the exterior material 1, preventing the intrusion of oxygen and moisture. The metal foil layer 4 is not particularly limited, but examples thereof include aluminum foil, SUS foil (stainless steel foil), and copper foil. Among these, it is preferable to use aluminum foil and SUS foil (stainless steel foil). The thickness of the metal foil layer 4 is preferably 10 μm to 120 μm. A thickness of 10 μm or more can prevent the occurrence of pinholes during rolling in the manufacture of the metal foil, and a thickness of 120 μm or less can reduce stress during forming such as stretch forming and drawing, improving formability.

It is preferable that at least the inner surface (the surface on the side of the second adhesive layer 6) of the metal foil layer 4 is subjected to a chemical conversion treatment. By performing such a chemical conversion treatment, corrosion of the metal foil surface due to the contents (such as the electrolyte of a battery) can be sufficiently prevented. For example, the chemical conversion treatment is performed on the metal foil by carrying out the following treatment. That is, for example, 1) phosphoric acid and
Chromic acid,
at least one compound selected from the group consisting of metal salts of fluorides and non-metal salts of fluorides; 2) an aqueous solution of a mixture containing phosphoric acid;
At least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins;
3) an aqueous solution of a mixture containing phosphoric acid and at least one compound selected from the group consisting of chromic acid and chromium (III) salts;
At least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins;
At least one compound selected from the group consisting of chromic acid and chromium (III) salts;
and at least one compound selected from the group consisting of a metal salt of fluoride and a non-metal salt of fluoride. The chemical conversion treatment is carried out by applying an aqueous solution of any one of the above 1) to 3) and drying it.

The chemical conversion coating preferably has a chromium coating amount (per side) of 0.1 mg/m ² to 50 mg/m ² , and more preferably 2 mg/m ² to 20 mg/m ² .

The first adhesive layer (outer adhesive layer) 5 is not particularly limited, but examples include a polyurethane polyolefin adhesive layer, a polyurethane adhesive layer, a polyester polyurethane adhesive layer, and a polyether polyurethane adhesive layer. The thickness of the first adhesive layer 5 is preferably set to 1 μm to 6 μm. In particular, from the viewpoint of making the exterior material 1 thinner and lighter, it is particularly preferable that the thickness of the first adhesive layer 5 is set to 1 μm to 3 μm.

The second adhesive layer (inner adhesive layer) 6 is not particularly limited, and may be, for example, one of the first adhesive layer 5 exemplified above, but it is preferable to use a polyolefin adhesive that swells less with the electrolyte. Among them, it is particularly preferable that the second adhesive layer (inner adhesive layer) 6 is formed of an adhesive containing an olefin resin having a carboxyl group and a polyfunctional isocyanate compound. The second adhesive layer can be formed by dry lamination of the adhesive. Alternatively, it is particularly preferable that the second adhesive layer (inner adhesive layer) 6 is formed of an olefin resin having a carboxyl group. In this case, the second adhesive layer can be formed by extrusion lamination by melt extrusion of the olefin resin having a carboxyl group. The olefin resin having a carboxyl group is not particularly limited, and may be, for example, a carboxylic acid-modified olefin resin such as maleic acid-modified polypropylene, maleic acid-modified polyethylene, acrylic acid-modified polypropylene, acrylic acid-modified polyethylene, methacrylic acid-modified polypropylene, methacrylic acid-modified polyethylene, fumaric acid-modified polypropylene, or fumaric acid-modified polyethylene. The thickness of the second adhesive layer 6 is preferably set to 1 μm to 4 μm. In particular, from the viewpoint of making the exterior material thinner and lighter, it is particularly preferable that the thickness of the second adhesive layer 6 is set to 1 μm to 3 μm.

By molding (deep drawing, stretch molding, etc.) the exterior material 1 of the present invention, an exterior case (battery case, etc.) 10 can be obtained (Figure 4). Note that the exterior material 1 of the present invention can also be used as is without being subjected to molding (Figure 4).

FIG. 3 shows an embodiment of an electric storage device 30 constructed using the exterior material 1 of the present invention. This electric storage device 30 is a lithium ion secondary battery. In this embodiment, as shown in FIGS. 3 and 4, an exterior member 15 is constructed by an exterior case 10 obtained by molding the exterior material 1 and a planar exterior material 1. Thus, an approximately rectangular parallelepiped electric storage device main body (electrochemical element, etc.) 31 is housed in the housing recess of the exterior case 10 obtained by molding the exterior material 1 of the present invention, and the exterior material 1 of the present invention is placed on the electric storage device main body 31 with its sealant layer 3 side facing inward (lower side) without being molded, and the peripheral portion of the sealant layer 3 of the planar exterior material 1 and the sealant layer 3 of the flange portion (sealing peripheral portion) 29 of the exterior case 10 are sealed and sealed by heat sealing to construct the electric storage device 30 of the present invention (see FIGS. 3 and 4). The inner surface of the storage recess of the exterior case 10 is a sealant layer 3, and the outer surface of the storage recess is a base layer (outer layer) 2 (see Figure 4).

In FIG. 3, 39 is a heat seal portion where the peripheral portion of the exterior material 1 and the flange portion (sealing peripheral portion) 29 of the exterior case 10 are joined (welded). In the electricity storage device 30, the tip of the tab lead connected to the electricity storage device main body 31 is led out to the outside of the exterior member 15, but is not shown in the figure.

The electric storage device main body 31 is not particularly limited, but examples thereof include a battery main body, a capacitor main body, a condenser main body, etc.

The width of the heat-sealed portion 39 is preferably set to 0.5 mm or more. By setting the width at 0.5 mm or more, sealing can be performed reliably. In particular, the width of the heat-sealed portion 39 is preferably set to 3 mm to 15 mm.

In the above embodiment, the exterior member 15 is configured to include an exterior case 10 obtained by molding the exterior material 1 and a planar exterior material 1 (see Figures 3 and 4), but is not limited to this combination. For example, the exterior member 15 may be configured to include a pair of planar exterior materials 1, or a pair of exterior cases 10.

Next, specific examples of the present invention will be described, but the present invention is not particularly limited to these examples.

<Materials used>
(Elastomer-modified olefin resin A)
The elastomer-modified olefin-based resin A is composed of an EPR-modified homopolypropylene and an EPR-modified ethylene-propylene random copolymer. The EPR stands for ethylene-propylene rubber. The content of the elastomer component in the elastomer-modified olefin-based resin A is 15% by mass. The melting point of the elastomer-modified olefin-based resin A is 166°C.
(Elastomer-modified olefin resin B)
The elastomer-modified olefin-based resin B is composed of a propylene-butene elastomer-modified homopolypropylene and a propylene-butene elastomer-modified ethylene-propylene random copolymer. The content of the elastomer component in the elastomer-modified olefin-based resin B is 18% by mass. The melting point of the elastomer-modified olefin-based resin B is 164°C.
(Elastomer-modified olefin resin C)
The elastomer-modified olefin-based resin C is composed of a propylene-butene-ethylene elastomer-modified homopolypropylene and a propylene-butene-ethylene elastomer-modified product of an ethylene-propylene random copolymer. The content of the elastomer component in the elastomer-modified olefin-based resin C is 16% by mass. The melting point of the elastomer-modified olefin-based resin C is 164°C.

Example 1
A chemical conversion coating was formed by applying a chemical conversion treatment solution consisting of phosphoric acid, polyacrylic acid (acrylic resin), a chromium (III) salt compound, water, and alcohol to both sides of an aluminum foil 4 having a thickness of 35 μm, and then drying at 180° C. The chromium deposition amount of this chemical conversion coating was 10 mg/ ^m2 per side.

Next, a 15 μm-thick biaxially oriented 6 nylon film 2 was dry laminated (attached) to one side of the chemically treated aluminum foil 4 via a two-component curing urethane adhesive (outer adhesive) 5.

Next, an 80 μm thick sealant film (first sealant layer) 7 made of elastomer-modified olefin resin A was extruded, and then the other side of the dry-laminated aluminum foil 4 was superimposed on one side of the sealant film 7 (3) via a two-component curing urethane adhesive (inner adhesive layer) 6, and the other side was dry-laminated by sandwiching and pressing between a rubber nip roll and a laminating roll heated to 100°C, and then aging (heating) at 50°C for 5 days to obtain an exterior material 1 for an electricity storage device having the configuration shown in FIG. 1.

Example 2
An exterior material 1 for an electricity storage device having the configuration shown in FIG. 1 was obtained in the same manner as in Example 1, except that a two-component curing acrylic adhesive 6 was used as the inner adhesive 6 instead of the two-component curing urethane adhesive.

Example 3
A chemical conversion coating was formed by applying a chemical conversion treatment solution consisting of phosphoric acid, polyacrylic acid (acrylic resin), a chromium (III) salt compound, water, and alcohol to both sides of an aluminum foil 4 having a thickness of 35 μm, and then drying at 180° C. The chromium deposition amount of this chemical conversion coating was 10 mg/ ^m2 per side.

Next, a 15 μm-thick biaxially oriented 6 nylon film 2 was dry laminated (attached) to one side of the chemically treated aluminum foil 4 via a two-component curing urethane adhesive 5.

Next, a 4 μm-thick maleic anhydride-modified polypropylene film (inner adhesive layer) 6, an 8 μm-thick propylene-ethylene random copolymer film (second sealant layer) 8, and a 72 μm-thick elastomer-modified olefin resin A film (first sealant layer) 7 were co-extruded and layered in this order on the other side of the aluminum foil 4 after the dry lamination, and the resulting product was dry laminated by being pressed between a rubber nip roll and a laminating roll heated to 100°C, and then aged (heated) at 50°C for 5 days to obtain an exterior material 1 for an electricity storage device having the configuration shown in FIG. 2.

Example 4
A chemical conversion coating was formed by applying a chemical conversion treatment solution consisting of phosphoric acid, polyacrylic acid (acrylic resin), a chromium (III) salt compound, water, and alcohol to both sides of an aluminum foil 4 having a thickness of 35 μm, and then drying at 180° C. The chromium deposition amount of this chemical conversion coating was 10 mg/ ^m2 per side.

Next, a 15 μm-thick biaxially oriented 6 nylon film 2 was dry laminated (attached) to one side of the chemically treated aluminum foil 4 via a two-component curing urethane adhesive 5.

Next, a 4 μm-thick maleic anhydride-modified polypropylene film (inner adhesive layer) 6 and an 80 μm-thick elastomer-modified olefin resin A film 3 were co-extruded and layered in this order on the other side of the dry-laminated aluminum foil 4, and the resulting film was dry-laminated by being sandwiched between a rubber nip roll and a laminating roll heated to 100°C and pressure-bonded. The resulting film was then aged (heated) at 50°C for 5 days to obtain the exterior material 1 for an electricity storage device having the configuration shown in FIG. 1.

Example 5
Except for using elastomer-modified olefin-based resin B instead of elastomer-modified olefin-based resin A, the same procedure as in Example 1 was carried out to obtain an exterior material for an electricity storage device 1 having the configuration shown in FIG.

Example 6
Except for using elastomer-modified olefin-based resin C instead of elastomer-modified olefin-based resin A, the same procedure as in Example 1 was carried out to obtain an exterior material for an electricity storage device 1 having the configuration shown in FIG.

Example 7
A chemical conversion coating was formed by applying a chemical conversion treatment solution consisting of phosphoric acid, polyacrylic acid (acrylic resin), a chromium (III) salt compound, water, and alcohol to both sides of an aluminum foil 4 having a thickness of 35 μm, and then drying at 180° C. The chromium deposition amount of this chemical conversion coating was 10 mg/ ^m2 per side.

Next, a 15 μm-thick biaxially oriented 6 nylon film 2 was dry laminated (attached) to one side of the chemically treated aluminum foil 4 via a two-component curing urethane adhesive 5.

Next, a two-component curing urethane adhesive (inner adhesive layer) 6 was applied to the other side of the dry-laminated aluminum foil 4, and then a homopolypropylene film (second sealant layer) 8 having a thickness of 8 μm and an elastomer-modified olefin resin A film (first sealant layer) 7 having a thickness of 72 μm were co-extruded and laminated in this order on the coated surface, and the resulting film was sandwiched between a rubber nip roll and a laminating roll heated to 100°C and pressed to dry laminate. The resulting film was then aged (heated) at 50°C for 5 days to obtain the exterior material 1 for an electricity storage device having the configuration shown in FIG. 2.

Example 8
An exterior material for a power storage device 1 having the configuration shown in FIG. 2 was obtained in the same manner as in Example 7, except that a propylene-ethylene random copolymer film 8 having a thickness of 8 μm was used as the second sealant layer 8 instead of the homopolypropylene film having a thickness of 8 μm.

<Example 9>
An exterior material for an electricity storage device 1 having the configuration shown in Figure 2 was obtained in the same manner as in Example 8, except that a two-component curing acrylic adhesive 6 was used as the inner adhesive 6 instead of the two-component curing urethane adhesive.

<Comparative Example 1>
An outer casing material for an electricity storage device having the configuration shown in FIG. 1 was obtained in the same manner as in Example 1, except that a propylene-ethylene random copolymer was used instead of the elastomer-modified olefin resin A.

<Comparative Example 2>
A chemical conversion coating was formed by applying a chemical conversion treatment solution consisting of phosphoric acid, polyacrylic acid (acrylic resin), a chromium (III) salt compound, water, and alcohol to both sides of an aluminum foil 4 having a thickness of 35 μm, and then drying at 180° C. The chromium deposition amount of this chemical conversion coating was 10 mg/ ^m2 per side.

Next, a 15 μm-thick biaxially oriented 6 nylon film 2 was dry laminated (attached) to one side of the chemically treated aluminum foil 4 via a two-component curing urethane adhesive 5.

Next, a two-component curing acrylic adhesive 6 was applied to the other side of the dry-laminated aluminum foil 4, and then a 68 μm-thick elastomer-modified olefin resin A film (second sealant layer) 8 and a 12 μm-thick propylene-ethylene random copolymer film (first sealant layer) 7 were co-extruded and layered on the coated surface in this order, and the layers were dry-laminated by being sandwiched between a rubber nip roll and a laminating roll heated to 100°C and pressure-bonded, and then aged (heated) at 50°C for 5 days to obtain an exterior material for an electricity storage device having the configuration shown in FIG. 2.

The tensile yield strength (see Table 1) of the sealant film (thickness 80 μm) 3 used to prepare the exterior materials of Examples 1 to 9 and Comparative Examples 1 and 2 was measured as follows.

<Method for measuring tensile yield strength of sealant film>
For a separate non-stretched sealant film 3 (thickness 80 μm) prepared in the same manner for measurement, a type 2 test piece (length 150 mm or more) was prepared in accordance with JIS K7127-1999 (tensile test method for plastic films), and a tensile test was performed under conditions of 80° C., sample width 15 mm, grip distance 100 mm, gauge distance 50 mm, and tensile speed 100 mm/min to determine the tensile yield strength (tensile yield strength). The load at the yield point in the S-S curve is the tensile yield strength. The test piece was set in a tensile tester in a thermostatic chamber set at 80° C., and then left to stand in this 80° C. environment for 1 minute before carrying out a tensile test in the 80° C. environment. The measurement results of the tensile yield strength at 80° C. are shown in Table 1.

The thickness of the test piece is set to 80 μm for measurement, but if the sealant film 3 used is 64 μm thick and has a two-layer laminate structure of a second sealant layer with a thickness of 6 μm and a first sealant layer with a thickness of 58 μm, for example, a test piece with a thickness of 80 μm should be created and measured so that the thickness ratio of the two layers does not change. In other words, a test piece with a two-layer laminate structure of a second sealant layer with a thickness of 7.5 μm and a first sealant layer with a thickness of 72.5 μm should be created and measured. In the case of a laminate structure of three or more layers, a test piece with a thickness of 80 μm should be created and measured in the same manner.

The exterior materials for electricity storage devices obtained as described above were evaluated based on the following measurement methods.

<Method for measuring initial seal strength at high temperatures>
Two test pieces measuring 15 mm in width and 150 mm in length were cut out from the obtained exterior material, and then these two test pieces were overlapped so that their inner sealant layers were in contact with each other. In this state, heat sealing was performed by heating on one side using a heat sealing device (TP-701-A) manufactured by Tester Sangyo Co., Ltd. under the following conditions: heat sealing temperature: 200°C, sealing pressure: 0.2 MPa (gauge pressure), sealing time: 2 seconds.

Next, for a pair of exterior materials in which the inner sealant layers were heat-sealed together as described above, the peel strength was measured when the exterior materials (test pieces) were peeled at 90 degrees between the inner sealant layers of the sealed portions at a tensile speed of 100 mm/min using a Shimadzu Access Strograph (tensile testing device) (AGS-5kNX) placed in a thermostatic chamber in accordance with JIS Z0238-1998, and this was taken as the seal strength (N/15 mm width). The seal strength was measured at 100°C and 120°C.

When measuring the seal strength at 100°C, the test specimen was set in a tensile testing device in a thermostatic chamber set at 100°C, and then left to stand in this 100°C environment for one minute before measuring in the 100°C environment. When measuring the seal strength at 120°C, the test specimen was set in a tensile testing device in a thermostatic chamber set at 120°C, and then left to stand in this 120°C environment for one minute before measuring in the 120°C environment.

Products that have a seal strength of 27 N/15 mm width or more at both 100°C and 120°C are considered to pass.

<Method for measuring seal strength after 90 days in a high temperature environment>
Two pieces of exterior materials cut to a size of 200 mm long x 150 mm wide were placed on top of each other with the sealant layers facing each other on the inside, and the edges of the three sides were heat-sealed at 180°C and 0.2 MPa for 2 seconds. 10 mL of electrolyte was poured into the opening of the remaining unsealed side, and the remaining side was also heat-sealed while removing the air under the same sealing conditions as above to create a simulated battery (test specimen). The electrolyte used was an electrolyte in which lithium hexafluorophosphate (LiPF ₆ ) was dissolved at a concentration of 1 mol/L in a mixed solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed in equal volume ratios.

The resulting simulated battery was placed in an ESPEC thermo-hygrostat and left to stand for 90 days under conditions of 80°C x 90% Rh (exposed to a high temperature and humidity environment for 90 days).

After the 90 days had passed, the simulated battery was removed, one side was opened to remove the electrolyte, and the inside was washed several times with water. The two sheets of exterior materials were then cut into a size of 15 mm wide x 150 mm long while overlapping each other so as to include the sealed portions of the two exterior materials. The resulting pair of exterior materials was then measured for peel strength when the sealant layers of the sealed portions of the pair of exterior materials were peeled off at 90 degrees at a tensile speed of 100 mm/min using a Strograph (tensile testing device) (AGS-5kNX) manufactured by Shimadzu Access Co., Ltd., in accordance with JIS Z0238-1998, and this was taken as the seal strength (N/15 mm width). The seal strength was measured at 25°C. A seal strength of 27 N/15 mm width or more was deemed to be acceptable.

As is clear from Table 1, the electrical storage device packaging materials of Examples 1 to 9 according to the present invention are able to ensure sufficient initial seal strength even in a high-temperature environment, and are able to maintain sufficient seal strength even when placed in a high-temperature environment for a long period of time.

In contrast, in Comparative Examples 1 and 2, the initial seal strength was insufficient in a high-temperature environment, and the seal strength was significantly reduced after being left in a high-temperature environment for a long period of time.

Specific examples of the electrical storage device packaging material produced using the sealant film according to the present invention and the electrical storage device packaging material according to the present invention include, for example,
Used as an exterior material for various electricity storage devices such as lithium secondary batteries (lithium ion batteries, lithium polymer batteries, etc.), lithium ion capacitors, electric double layer capacitors, etc. The electricity storage device according to the present invention includes all-solid-state batteries in addition to the electricity storage devices exemplified above.

1... Exterior material for power storage device 2... Heat-resistant resin layer (outer layer)
3...Sealant layer (inner layer)
4...Metal foil layer 5...Outer adhesive layer (first adhesive layer)
6...Inner adhesive layer (second adhesive layer)
7...First sealant layer (innermost layer; innermost sealant layer)
8...Second sealant layer (sealant layer closest to the metal foil layer)
10... Outer case for power storage device 15... Outer case member 30... Power storage device 31... Power storage device main body

Claims (7)

An exterior material for an electricity storage device, comprising a heat-resistant resin layer as an outer layer, a sealant layer as an inner layer, and a metal foil layer disposed between these layers,
The sealant layer is composed of one or more layers, and at least the innermost layer of the sealant layer contains an elastomer-modified olefin-based resin,
The elastomer-modified olefin-based resin contains an olefin-based thermoplastic elastomer-modified homopolypropylene,
The electrical storage device exterior material , wherein the elastomer-modified olefin resin has an olefin thermoplastic elastomer component content of 0.1 mass % or more and less than 20 mass % . The exterior material for a storage battery device according to claim 1, wherein the melting point of the elastomer-modified olefin resin constituting the innermost layer is higher than 160°C. The exterior material for a storage battery device according to claim 1 or 2, wherein the sealant film constituting the sealant layer has a tensile yield strength at 80°C of 3.5 MPa to 15.0 MPa. The exterior material for a storage battery device according to any one of claims 1 to 3, characterized in that the sealant layer is made up of multiple layers, a second sealant layer is disposed on the side of the sealant layer closest to the metal foil layer, and the second sealant layer contains 50% by mass or more of a propylene-ethylene random copolymer and does not contain an elastomer component. The exterior material for an electricity storage device according to any one of claims 1 to 4, wherein the metal foil layer and the sealant layer are bonded via an adhesive layer. The exterior material for a storage battery device according to claim 5, wherein the adhesive layer is made of an adhesive containing an olefin resin having a carboxyl group and a polyfunctional isocyanate compound. A main body of the electricity storage device;
The electrical storage device packaging material according to any one of claims 1 to 6,
A power storage device, characterized in that the power storage device main body is exteriorly covered with the exterior material.

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