Energy storage device and method for manufacturing the same, and exterior material for energy storage device and method for manufacturing the same

Abstract

The present invention provides an energy storage device in which cracking of the sealing portion between the exterior material and the lid of the energy storage device is suppressed when repeatedly exposed to high and low temperature changes. [Solution] An energy storage device comprising an electrode body and an outer casing that seals the electrode body, wherein the outer casing has an outer film that encloses the electrode body and a lid that seals the electrode body together with the outer film, the outer film is composed of a laminate comprising a barrier layer and a heat-sealable resin layer, and the ratio of the area average crystal grain size R1 (μm) to the area average crystal grain size R2 (μm) (R1 / R2) is 55% or more. R1 (μm) is the area average crystal grain size (μm) obtained at the position where the heat-sealable resin layer of the outer film is heat-sealed to the lid, and R2 (μm) is the area average crystal grain size (μm) obtained at the position where the heat-sealable resin layer of the outer film is not heat-sealed.

Description

Technical Field

[0001] The present disclosure relates to a power storage device, a method for manufacturing the same, an exterior material for a power storage device, and a method for manufacturing the same.

Background Art

[0002] Conventionally, various types of power storage devices have been developed. In any power storage device, an exterior material is an essential member for sealing power storage device elements such as electrodes and electrolytes. Conventionally, a metal exterior material has been frequently used as an exterior film.

[0003] On the other hand, in recent years, with the improvement in performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, etc., various shapes are required for power storage devices, and thinning and weight reduction are also demanded. However, conventionally used metal exterior films have drawbacks in that it is difficult to follow the diversification of shapes, and there is also a limit to weight reduction.

[0004] Therefore, in recent years, as an exterior film that can be easily processed into various shapes and can achieve thinning and weight reduction, a film-like laminate in which a base material layer / barrier layer / heat-sealable resin layer are sequentially laminated has been proposed (for example, see Patent Document 1).

[0005] Further, Patent Document 2 discloses an example of a power storage device. This power storage device includes an electrode body and an exterior body that seals the electrode body. The exterior body includes an exterior film that wraps the electrode body and a lid body that is joined to the exterior film. This power storage device is manufactured, for example, by accommodating an electrode body inside a cylindrically configured exterior film and closing the opening of the cylindrically shaped exterior film with a lid body. The side surface of the lid body and the exterior film are joined, for example, by heat-sealing.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2008-287971 [Patent Document 2] Japanese Patent Publication No. 2022-123686 [Overview of the project] [Problems that the invention aims to solve]

[0007] An exterior body, such as the one disclosed in Patent Document 2, which comprises an outer film (exterior material for energy storage devices) that encloses an electrode body and a lid that is joined to the outer film, is useful, for example, as an exterior body for a large energy storage device.

[0008] Such an exterior body has a sealing portion (joint) between the exterior film (exterior material for energy storage devices) and the lid. The inventors of this disclosure have found a novel problem in that when the energy storage device is repeatedly exposed to high and low temperature changes, cracks occur in the sealing portion of the exterior film (exterior material for energy storage devices).

[0009] Under these circumstances, the main objective of this disclosure is to provide an energy storage device that utilizes an outer casing comprising an outer film (outer casing material for energy storage devices) enclosing an electrode body and a lid, wherein cracking of the sealing portion of the outer film with the lid is suppressed when the energy storage device is repeatedly exposed to high and low temperature changes.

[0010] Furthermore, this disclosure also aims to provide an exterior material for an energy storage device that includes an exterior material for an energy storage device that encloses an electrode body and a lid, and in which the occurrence of cracks in the sealing portion between the exterior material for the energy storage device and the lid is suppressed when the energy storage device is repeatedly exposed to high and low temperature changes. [Means for solving the problem]

[0011] The inventors of this disclosure have diligently studied to solve the above-mentioned problems. As a result, they have found that in an energy storage device comprising an electrode body and an outer casing that seals the electrode body, the outer casing comprises an outer film that encloses the electrode body and a lid that seals the electrode body together with the outer film, the outer film is composed of a laminate comprising at least a barrier layer and a heat-sealable resin layer, and the ratio of the area-average crystal grain size R1 (μm) to the area-average crystal grain size R2 (μm) of the barrier layer (R1 / R2), described later, to 55% or more suppresses the occurrence of cracks in the sealing portion of the outer film with the lid when the energy storage device is repeatedly exposed to high and low temperature changes.

[0012] This disclosure is the result of further consideration based on these findings. Specifically, this disclosure provides inventions in the following embodiments. It is an energy storage device, Electrode body and The electrode body is enclosed by an outer casing, The exterior body is, The outer film enclosing the electrode body, It has a lid that seals the electrode body together with the outer film, The exterior film is composed of a laminate comprising at least a barrier layer and a heat-sealable resin layer. The barrier layer has a ratio (R1 / R2) of area-average crystal grain size R1 (μm) to area-average crystal grain size R2 (μm) of 55% or more. The area-average grain size R1 (μm) is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicular to the surface of the barrier layer, in a direction perpendicular to the rolling direction of the barrier layer, at the position where the heat-sealable resin layer of the outer film is heat-sealed to the lid. The area-average grain size R2 (μm) is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicular to the surface of the barrier layer, in a direction perpendicular to the rolling direction of the barrier layer, at a position where the heat-fusible resin layer of the outer film is not heat-fussed. Energy storage device.

[0013] Furthermore, the inventors of this disclosure have diligently studied to solve the above-mentioned problems. As a result, they have found that, in an exterior material for an energy storage device composed of a laminate comprising at least a barrier layer and a heat-fusible resin layer, if the ratio of the area-average crystal grain size R1 (μm) to the area-average crystal grain size R2 (μm) of the barrier layer (R1 / R2), as described later, is 55% or more, the occurrence of cracks in the sealing portion of the exterior material for the energy storage device with the lid is suppressed when the energy storage device is repeatedly exposed to high and low temperature changes.

[0014] This disclosure is the result of further consideration based on these findings. Specifically, this disclosure also provides inventions in the following embodiments. An exterior material for an energy storage device, comprising at least a laminate comprising a barrier layer and a heat-sealable resin layer, The barrier layer has a ratio (R1 / R2) of area-average crystal grain size R1 (μm) to area-average crystal grain size R2 (μm) of 55% or more. The area-average grain size R1 (μm) is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicular to the surface of the barrier layer, in a direction perpendicular to the rolling direction of the barrier layer, at a position where the heat-sealable resin layer of the exterior material for the energy storage device and the polypropylene plate are heat-sealed under the condition that the thickness of the heat-sealable resin layer is 20% or more and 80% or less. The area-average grain size R2 (μm) is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicular to the surface of the barrier layer, in a direction perpendicular to the rolling direction of the barrier layer, at a position where the heat-fusible resin layer of the exterior material for the energy storage device and the polypropylene plate are not heat-fussed together. Exterior material for energy storage devices. [Effects of the Invention]

[0015] According to this disclosure, in an energy storage device utilizing an outer casing comprising an outer film enclosing an electrode body and a lid, it is possible to provide an energy storage device in which cracking of the sealing portion between the outer film and the lid (more specifically, cracking of the barrier layer) is suppressed when the energy storage device is repeatedly exposed to high and low temperature changes. Furthermore, according to this disclosure, a method for manufacturing the energy storage device can also be provided.

[0016] Furthermore, according to this disclosure, in an energy storage device utilizing an exterior material for an energy storage device that encloses an electrode body and a lid, it is possible to provide an exterior material for an energy storage device in which cracking of the sealing portion between the exterior material for the energy storage device and the lid (more specifically, cracking of the barrier layer) is suppressed when the energy storage device is repeatedly exposed to high and low temperature changes. Furthermore, according to this disclosure, it is also possible to provide a method for manufacturing the exterior material for an energy storage device and an energy storage device utilizing the exterior material for an energy storage device. [Brief explanation of the drawing]

[0017] [Figure 1] This is a perspective view showing an example of an energy storage device in this disclosure. [Figure 2] This is a cross-sectional view along line AA in Figure 1. [Figure 3] This is a schematic diagram showing an example of a cover for the present disclosure. [Figure 4] This is a schematic diagram showing an example of the cross-sectional structure of the exterior film of the present disclosure. [Figure 5] This is a schematic diagram showing an example of the cross-sectional structure of the exterior material for the energy storage device of this disclosure. [Figure 6] This is a schematic diagram showing an example of the cross-sectional structure of the exterior material for the energy storage device of this disclosure. [Figure 7] This is a schematic diagram showing an example of the cross-sectional structure of the exterior material for the energy storage device of this disclosure. [Figure 8] This is a schematic diagram showing an example of the cross-sectional structure of the exterior material for the energy storage device of this disclosure. [Figure 9] This is a schematic diagram illustrating a method for housing an energy storage device element in a package formed from the exterior material for energy storage devices of the present disclosure. [Figure 10] This is a perspective view showing an example of an energy storage device using the exterior material for energy storage devices of this disclosure. [Figure 11] This is a cross-sectional view along line AA in Figure 10. [Figure 12] This is a schematic diagram showing an example of a cover for the present disclosure. [Modes for carrying out the invention]

[0018] In the energy storage device of this disclosure, the outer film comprises an electrode body and an outer body that seals the electrode body. The outer body has an outer film that encloses the electrode body and a lid that seals the electrode body together with the outer film (outer material for energy storage device). The outer film is composed of a laminate comprising at least a barrier layer and a heat-sealable resin layer. The barrier layer has a ratio (R1 / R2) of area-average grain size R1 (μm) to area-average grain size R2 (μm) of 55% or more. The area-average grain size R1 (μm) is the area-average grain size (μm) obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicular to the surface of the barrier layer (i.e., perpendicular to the surface of the barrier layer) in a direction perpendicular to the rolling direction of the barrier layer at the position where the heat-sealable resin layer of the outer film is heat-sealed to the lid. The area-average grain size R2 (μm) is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicular to the surface of the barrier layer, in a direction perpendicular to the rolling direction of the barrier layer, at a location where the heat-sealable resin layer of the outer film is not heat-sealed. The energy storage device of this disclosure, by having this configuration, suppresses the occurrence of cracks in the sealing portion between the outer film and the lid.

[0019] Furthermore, the exterior material for energy storage devices of this disclosure is composed of a laminate comprising at least a barrier layer and a heat-sealable resin layer in this order, wherein the ratio of the area average grain size R1 (μm) to the area average grain size R2 (μm) (R1 / R2) of the barrier layer is 55% or more, and the area average grain size R1 (μm) is perpendicular to the rolling direction of the barrier layer and on the surface of the barrier layer at the position where the heat-sealable resin layer of the exterior material for energy storage devices and the polypropylene plate are heat-sealed under the condition that the thickness of the heat-sealable resin layer is 20% or more and 80% or less The area average grain size (μm) is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicularly, and the area average grain size R2 (μm) is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicularly from the surface of the barrier layer, in a position where the heat-fusible resin layer and the polypropylene plate of the exterior material for the energy storage device are not heat-fussed, in a direction perpendicular to the rolling direction of the barrier layer. The exterior material for the energy storage device according to this disclosure has the above configuration, which suppresses the occurrence of cracks in the sealing portion between the exterior material for the energy storage device and the lid.

[0020] The following details the energy storage device and exterior film (hereinafter also referred to as the exterior material for the energy storage device) described herein. In this disclosure, numerical ranges indicated by "~" mean "greater than or equal to" and "less than or equal to". For example, the notation 2~15mm means 2mm or more and 15mm or less. In numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Alternatively, upper and lower limits, upper and lower limits, or lower limits described separately may be combined to form numerical ranges. Furthermore, in numerical ranges described in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples.

[0021] Furthermore, in exterior films and exterior materials for energy storage devices, the Machine Direction (MD) and Transverse Direction (TD) of the barrier layer 52 and barrier layer 3, described later, can usually be determined during their manufacturing process. For example, when the barrier layer 52 and barrier layer 3 are composed of metal foils such as aluminum alloy foil and stainless steel foil, linear lines called rolling marks are formed on the surface of the metal foil in the rolling direction (RD). Since 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. Also, in the manufacturing process of a laminate, the MD of the laminate and the RD of the metal foil usually coincide, so the MD of the laminate can be determined by observing the surface of the metal foil in the laminate and identifying the rolling direction (RD) of the metal foil. In addition, since the TD of the laminate is perpendicular to the MD of the laminate, the TD of the laminate can also be determined.

[0022] Furthermore, if the MD of the outer film cannot be identified due to the rolling marks of metal foils such as aluminum alloy foil or stainless steel foil, it can be identified by the following method. One method for confirming the MD of the outer film is to observe the cross-section of the heat-fusible resin layer of the outer film with an electron microscope and confirm the sea-island structure. In this method, the direction parallel to the cross-section where the average diameter of the island shapes perpendicular to the thickness direction of the heat-fusible resin layer is largest can be determined as the MD. Specifically, the sea-island structure is confirmed by observing electron microscope images of each of the following cross-sections (a total of 10 cross-sections) from the cross-section in the length direction of the heat-fusible resin layer, with angles changed by 10 degrees from the direction parallel to the cross-section in the length direction, up to the direction perpendicular to the cross-section in the length direction. Next, the shape of each individual island is observed in each cross-section. For each island shape, the straight-line distance connecting the leftmost point perpendicular to the thickness direction of the heat-fusible resin layer and the rightmost point perpendicular to that direction is defined as the diameter y. In each cross-section, the average of the top 20 diameters y of the island shapes, in descending order of diameter y, is calculated. The direction parallel to the cross-section where the average of the relevant diameter y of the island's shape was largest is determined to be the MD (Movement Direction).

[0023] <1-1. Configuration of Energy Storage Devices> Figure 1 is a schematic perspective view of the energy storage device 10. Figure 2 is a cross-sectional view along line AA in Figure 1. Figure 3 is a schematic diagram showing an example of a cover 60. Figure 4 is a cross-sectional view showing an example of the laminated structure of the outer film 50 provided on the energy storage device 10 in Figure 1. In Figures 1 to 3, the z direction of the arrow (z1 and z2 directions) indicates the thickness direction of the energy storage device 10, the x direction of the arrow (x1 and x2 directions) indicates the width direction of the energy storage device 10, and the y direction of the arrow (y1 and y2 directions) indicates the depth direction of the energy storage device 10. The directions indicated by arrows x, y, and z are the same in all subsequent figures.

[0024] The energy storage device 10 comprises an electrode body 20, electrode terminals 30, and an outer casing 40. The electrode body 20 includes, for example, electrodes (positive and negative electrodes) that constitute an energy storage component such as a lithium-ion battery, capacitor, all-solid-state battery, semi-solid-state battery, pseudo-solid-state battery, polymer battery, all-resin battery, lead-acid battery, nickel-metal hydride battery, nickel-cadmium battery, nickel-iron battery, nickel-zinc battery, silver oxide-zinc battery, metal-air battery, polyvalent cation battery, or capacitor, as well as a separator, etc. In this disclosure, the shape of the electrode body 20 is, for example, a substantially rectangular parallelepiped. Note that "substantially rectangular parallelepiped" includes not only a perfect rectangular parallelepiped but also a solid that can be considered a rectangular parallelepiped by, for example, modifying the shape of a part of its outer surface. The shape of the electrode body 20 may be, for example, a cylinder or a polygonal prism.

[0025] The energy storage device 10 shown in Figures 1 and 2 is equipped with two electrode terminals 30. The electrode terminals 30 are metal terminals used for inputting and outputting power to the electrode body 20. One end of the electrode terminal 30 is electrically connected to an electrode (positive or negative electrode) included in the electrode body 20. The other end of the electrode terminal 30 protrudes outward from, for example, the edge of the outer casing 40. Note that the electrode terminal 30 only needs to be able to input and output power to the electrode body 20, and does not need to protrude from, for example, the outer casing 40. If the cover 60, which will be described later, is made of, for example, a conductive material, the cover 60 may also function as an electrode terminal 30, and in this case, the cover 60 that functions as an electrode terminal may or may not protrude from the outer casing 40.

[0026] The metal material constituting the electrode terminal 30 is, for example, aluminum, nickel, or copper. For example, if the electrode body 20 is a lithium-ion battery, the electrode terminal 30 connected to the positive electrode is usually made of aluminum, and the electrode terminal 30 connected to the negative electrode is usually made of copper, nickel, or the like. The outermost layer of the electrode body 20 does not necessarily have to be an electrode; for example, it may be a protective tape or a separator. The outer shape of the electrode body 20 is, for example, a rectangular parallelepiped.

[0027] The outer casing 40 seals the electrode body 20. The outer casing 40 comprises an outer film 50 and a lid 60. The outer film 50 wraps around the electrode body 20. In Figures 1 and 2, the outer film 50 is wrapped around the electrode body 20. The lid 60 is positioned to the side of the electrode body 20 in the y-direction. In another example, the electrode body 20 may be housed inside a cylindrical outer film 50 with openings formed at both ends in the y-direction, and the openings may be closed by the lid 60. In yet another example, the electrode body 20 may be housed inside a cylindrical outer film 50 with openings formed thereon, connected to the lid 60, and the openings may be closed by the lid 60.

[0028] The outer casing 40 has a pair of main surfaces and a pair of side surfaces formed by the outer film 50. In Figures 1 and 2, the pair of main surfaces are substantially the same size. The pair of side surfaces are also substantially the same size. Each of the pair of main surfaces has a larger area than the pair of side surfaces. The pair of lids 60 are positioned to the sides of the electrode body 20 so as to close the pair of openings. In this disclosure, the main surfaces and side surfaces are the surfaces of the outer casing 40 excluding the lids 60.

[0029] For example, one method is to form a housing portion (recess) for housing the electrode body 20 in the outer film 50 through cold forming. However, it is not always easy to form a deep housing portion by such a method. If one attempts to form a deep housing portion (recess) (for example, a forming depth of 15 mm) by cold forming, pinholes or cracks may occur in the outer film 50, which is likely to lead to a decrease in battery performance. On the other hand, the outer body 40 seals the electrode body 20 by wrapping the outer film 50 around the electrode body 20, so the electrode body 20 can be easily sealed regardless of the thickness of the electrode body 20. Furthermore, in order to reduce the dead space between the electrode body 20 and the outer film 50 in order to improve the volumetric energy density of the energy storage device 10, it is preferable that the outer film 50 is wrapped so as to be in contact with the outer surface of the electrode body 20. In addition, in all-solid-state batteries, it is necessary to eliminate the space between the electrode body 20 and the outer film 50 from the viewpoint that it is necessary to apply high pressure uniformly from the outside surface of the battery in order to exert battery performance, so it is preferable that the outer film 50 is wrapped so as to be in contact with the outer surface of the electrode body 20. When wrapping the outer film 50 around the electrode body 20, one outer film 50 may be wrapped around it, or multiple outer films 50 may be wrapped around it. In addition to the configuration in which the opposing surfaces of the outer film 50 are heat-fused together, a configuration in which the outer surface and inner surface of the outer film 50 are heat-fused together is also preferred.

[0030] As shown in Figure 4, the outer film 50 is a laminate (laminate film) having at least a barrier layer 52 and a heat-sealable resin layer 53. Details of each layer included in the outer film 50 will be described later.

[0031] The lid 60 may be any shape, such as a cylinder, prism, rectangular parallelepiped, or cube, and may be composed of, for example, a resin material. Here, "composed of a resin material" means that when the total mass of the materials constituting the lid 60 is considered to be 100% by mass, the resin material content is 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. In other words, the materials constituting the lid 60 may contain materials other than resin materials in addition to resin materials.

[0032] Specific examples of resins include thermoplastic resins such as polyester, polyolefin, polyamide, epoxy resin, acrylic resin, fluororesin, polyurethane, silicon resin, and phenolic resin, as well as modified versions of these resins. The resin material may also be a mixture of these resins, a copolymer, or a modified version of a copolymer. Among these, the resin material is preferably a heat-sealable resin such as polyester or polyolefin, and more preferably polyolefin. When the resin material is a resin, the lid 60 may be molded by any molding method.

[0033] Examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymerized polyesters. Examples of copolymerized polyesters include copolymerized polyesters with ethylene terephthalate as the main repeating unit. Specifically, examples include copolymerized polyesters polymerized with ethylene isophthalate using ethylene terephthalate as the main repeating unit (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). Among these, polybutylene terephthalate is preferred as the resin material from the viewpoint of improving heat resistance and pressure resistance.

[0034] Furthermore, specific examples of polyolefins include polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; polypropylene such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymer of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymer of propylene and ethylene); propylene-α-olefin copolymers; and ethylene-butene-propylene terpolymers. When polyolefin resins are copolymers, they may be block copolymers or random copolymers. Among these, polypropylene is preferred as the resin material because it has excellent heat-sealability and electrolyte resistance.

[0035] The resin material may contain fillers as needed. Specific examples of fillers include glass beads, graphite, glass fibers, and carbon fibers. By including the above-mentioned fillers in the resin material, the deformation resistance of the lid 60 to temperature changes can be improved.

[0036] The melt mass flow rate (measurement temperature 230°C) of the resin material contained in the material constituting the lid 60 is preferably in the range of 1 g / 10 min to 100 g / 10 min, preferably in the range of 1 g / 10 min to 80 g / 10 min, preferably in the range of 1 g / 10 min to 60 g / 10 min, preferably in the range of 5 g / 10 min to 100 g / 10 min, preferably in the range of 5 g / 10 min to 80 g / 10 min, and more preferably in the range of 5 g / 10 min to 60 g / 10 min. The melt mass flow rate is measured in accordance with JIS K7210-1:2014.

[0037] The lid 60 may be made up of a conductive material. "Made up of a conductive material" means that when the total mass of the materials constituting the lid 60 is considered to be 100% by mass, the content of the conductive material is 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. In other words, the materials constituting the lid 60 may contain materials other than conductive materials in addition to conductive materials.

[0038] The conductive material constituting the cover 60 is, for example, a metallic material. The metallic material constituting the cover 60 is, for example, aluminum, aluminum alloy, nickel, copper, or copper alloy. For example, if the electrode body 20 is a lithium-ion battery, the cover 60 connected to the positive electrode is preferably made of aluminum or an aluminum alloy. The cover 60 connected to the negative electrode is preferably made of nickel, copper, or a copper alloy. The material constituting the cover 60 connected to the negative electrode may be copper with nickel plating. The material constituting the cover 60 may also include recycled metallic material. If the cover 60 is made of a conductive material, the cover 60 also functions as an electrode terminal 30, so the energy storage device 10 can omit the electrode terminal 30.

[0039] The lid 60 may be configured such that at least a portion of the lid body 61 is covered by a covering 62. In the lid 60 of Figure 3, the periphery of the lid body 61 (the periphery of the thickness portion) is covered by the covering 62. The lid 60 may be joined to the heat-sealable resin layer 53 of the outer film 50 via the covering 62. It is preferable that the covering 62 is made up of a resin material. The lid 60 has a lid body 61 and a covering 62 that joins the lid body 61 and the outer film 50, and the covering 62 may be made up of resin (resin material). The definition of "made up of a resin material" for the covering 62 is the same as for the lid 60.

[0040] If the lid 60 is made of a conductive material, the lid body 61 may be made of a conductive material, and at least a portion of the lid body 61 may be covered by the covering 62.

[0041] If the lid 60 is made of a conductive material, the lid 60 may be joined to the outer film 50 via an adhesive film instead of a covering. The adhesive film can be arbitrarily selected as long as it is a film that can adhere the outer film 50 and the lid 60. Preferably, the adhesive film is a laminated film having at least a heat-fusible resin layer, a heat-resistant substrate layer, and a heat-fusible resin layer in this order. The specifications for the heat-fusible resin layer of the adhesive film can be the same as those for the heat-fusible resin layer 53. The materials constituting the heat-fusible resin layers on both sides of the adhesive film may be the same material or different materials, and are appropriately selected in accordance with the materials constituting the heat-fusible resin layer 53 of the outer film 50 and the materials constituting the lid 60. Preferably, the material constituting the heat-fusible resin layer on the side of the adhesive film that is adhered to the lid 60 is an acid-modified polyolefin resin graft-modified with an acid such as maleic anhydride. It is preferable that the heat-sealable resin layer of the adhesive film that is bonded to the outer film 50 is made of the same material as the material that constitutes the heat-sealable resin layer 53 of the outer film 50.

[0042] The heat-resistant base layer can be any film made of a heat-resistant resin. For example, unstretched or stretched films of polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polymethylpentene (registered trademark), polyacetal cyclic polyolefin, polyethylene, polypropylene, etc. can be used. Polyethylene terephthalate is particularly preferred because it is inexpensive and strong.

[0043] The adhesive film preferably has adhesive properties. When the second sealing portion 80, described later, is formed with the adhesive film positioned between the outer film 50 and the lid 60, the position of the adhesive film relative to the lid 60 and the outer film 50 is less likely to shift. Adhesion can be imparted to the adhesive film by incorporating an adhesive-imparting resin into the heat-fusible resin layer of the adhesive film. Examples of adhesive-imparting resins include amorphous polyolefins. Examples of amorphous polyolefins include amorphous polypropylene, or copolymers of amorphous propylene and other α-olefins. The content of the adhesive-imparting resin relative to the base material constituting the heat-fusible resin is preferably 10 to 20% by weight or less.

[0044] The lid 60 has a first main surface located on the inside of the energy storage device (electrode body 20 side), a second main surface located on the outside of the energy storage device, and four sides that are heat-sealed to the heat-sealable resin layer 53 of the outer film 50. The first main surface faces the electrode body 20. The second main surface is the surface opposite to the first main surface.

[0045] When the lid 60 is cylindrical, prismatic, rectangular parallelepiped, or cube, it is preferable that the lid 60 has a certain thickness in the thickness direction (y direction) so as to suppress deformation of the outer casing 40 even when the energy storage devices 10 are stacked on top of each other. From another viewpoint, when the lid 60 is cylindrical, prismatic, rectangular parallelepiped, or cube, it is preferable that the lid 60 has a certain thickness in the thickness direction (y direction) so as to allow suitable joining of the lid joint of the lid 60 and the outer casing film 50 when forming the second sealing portion 80. The minimum value of the thickness of the lid 60 in the thickness direction (y direction) (distance in the y direction between the first main surface and the second main surface) is, for example, 1.0 mm, more preferably 3.0 mm, and even more preferably 4.0 mm. The maximum value of the thickness of the lid 60 in the y direction is, for example, 20 mm, preferably 15.0 mm, more preferably 10.0 mm, even more preferably 8.0 mm, and even more preferably 7.0 mm. The maximum thickness of the lid 60 in the y-direction may be 10 mm or more. The preferred range of thickness for the material constituting the lid 60 is 1.0 mm to 20.0 mm, 1.0 mm to 15.0 mm, 1.0 mm to 10.0 mm, 1.0 mm to 8.0 mm, 1.0 mm to 7.0 mm, 3.0 mm to 20.0 mm, 3.0 mm to 15.0 mm, 3.0 mm to 10.0 mm, 3.0 mm to 8.0 mm, 3.0 mm to 7.0 mm, 4.0 mm to 20.0 mm, 4.0 mm to 15.0 mm, 4.0 mm to 10.0 mm, 4.0 mm to 8.0 mm, and 4.0 mm to 7.0 mm. In this disclosure, when the lid 60 is described as a cylinder, prism, rectangular parallelepiped, or cube, etc., it does not include the form in which the lid 60 is composed solely of film as defined by the JIS (Japanese Industrial Standards) [Packaging Terminology] standard. The thickness of the lid 60 may vary depending on the part of the lid 60. If the thickness of the lid 60 varies depending on the part, the thickness of the lid 60 is the thickness of the thickest part.

[0046] In Figures 1 and 2, the lid 60 has a through-hole into which the electrode terminal 30 is inserted. The through-hole penetrates the first and second main surfaces of the lid. With the electrode body 20 housed inside, the electrode terminal 30 protrudes to the outside of the outer casing 40 through the through-hole formed in the lid 60. The small gap between the through-hole in the lid 60 and the electrode terminal 30 is filled with, for example, resin. In the energy storage device 10, the position in which the electrode terminal 30 protrudes to the outside can be arbitrarily selected. For example, the electrode terminal 30 may protrude to the outside through a hole formed in any of the six surfaces of the outer casing 40. In this case, the small gap between the outer casing 40 and the electrode terminal 30 is filled with, for example, resin. The electrode terminal 30 may also protrude from between the lid 60 and the outer film 50, or from the first sealing portion 70, which will be described later. In the energy storage device 10, the cover 60 and the electrode terminals 30 are provided as separate components, but the cover 60 and the electrode terminals 30 may be integrally formed. Furthermore, if the electrode terminals 30 do not protrude from the edge of the outer casing 40, the cover 60 does not need to have through holes.

[0047] In Figures 1 and 2, the outer film 50 is wrapped around the electrode body 20, and the first sealing portion 70 is formed by heat sealing the opposing surfaces of the outer film 50 (heat-fusible resin layers 53).

[0048] The first sealing portion 70 is formed by heat sealing the heat-sealable resin layers of the outer film 50. The first sealing portion 70 extends in the longitudinal direction of the outer body 40. The position in the outer body 40 where the first sealing portion 70 is formed can be arbitrarily selected. As shown in Figure 1, the base of the first sealing portion 70 is preferably located on the edge of the boundary between the main surface and the side surface of the outer body 40. The base of the first sealing portion 70 may also be located on any surface of the outer body 40. In Figure 1, the first sealing portion 70 protrudes outward from the electrode body 20 in a plan view. The first sealing portion 70 may be folded toward the side surface of the outer body 40, for example, or folded toward the main surface.

[0049] The heat-sealable resin layer 53 of the outer film 50 and the lid joint portion of the lid 60 (the portion where the heat-sealable resin layer 53 of the outer film 50 and the lid 60 come into contact) are joined, for example, by heat sealing to form the second sealing portion 80. The outer film 50 and the lid 60 can also be joined by any method, such as welding.

[0050] <1-2. Physical properties of energy storage devices> In the energy storage device of this disclosure, the barrier layer 52 of the outer film 50 is characterized in that the ratio of the area average crystal grain size R1 (μm) to the area average crystal grain size R2 (μm) (R1 / R2) is 55% or more.

[0051] Here, the area-average grain size R1 (μm) of the barrier layer 52 is the area-average grain size (μm) obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer 52 perpendicular to the surface of the barrier layer 52 (i.e., perpendicular to the surface of the barrier layer) at the position where the heat-fusible resin layer 53 of the outer film 50 is heat-fussed to the lid 60 (position of the second sealing portion 80), in a direction perpendicular to the rolling direction of the barrier layer 52.

[0052] Furthermore, the area-average grain size R2 (μm) of the barrier layer 52 is the area-average grain size (μm) obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer 52 perpendicular to the surface of the barrier layer 52, in a direction perpendicular to the rolling direction of the barrier layer 52, at a position where the heat-fusible resin layer 53 of the outer film 50 is not heat-fussed.

[0053] From the viewpoint of more favorably exhibiting the effects of the invention disclosed herein, the ratio (R1 / R2) is preferably about 55% or more, more preferably about 60% or more, even more preferably about 70% or more, and also preferably about 150% or less, more preferably about 140% or less, even more preferably about 130% or less. Preferred ranges include about 55-150%, about 55-140%, about 55-130%, about 60-150%, about 60-140%, about 60-130%, about 70-150%, about 70-140%, and about 70-130%.

[0054] The area-average grain size R1 (μm) and area-average grain size R2 (μm) of the barrier layer 52 are values ​​measured by the following method.

[0055] <Measurement of area-average crystal grain size R1 and R2 of the barrier layer> For the energy storage device, the barrier layer at the location where the heat-sealable resin layer of the outer film is heat-sealed to the lid (sealed area (second sealing area)) and the barrier layer at the location where the heat-sealable resin layer of the outer film is not heat-sealed (non-sealed area) are obtained, and crystallographic analysis is performed on each using the EBSD method to measure the area-average crystal grain sizes R1 and R2 of the barrier layers. The specific measurement method is as follows.

[0056] Crystallographic analysis of the cross-section of each barrier layer perpendicular to the rolling direction is performed using the EBSD method to measure the area-average grain size of the barrier layer. The details of the measurement conditions are as follows. The area-average grain size is the diameter when the area calculated by [(measurement area - area with CI value of 0.1 or less) / number of crystals] is assumed to be a circle. Multiple images obtained by crystallographic analysis using the EBSD method are stitched together to form an area of ​​approximately 5000 μm. 2 The above is the area-average grain size of the crystals included in the measurement area. The grain size is calculated assuming a circular crystal shape and is measured for the crystals within the measurement area. The standard deviation of the grain size is calculated by removing areas with a CI value of 0.1 or less, and then concatenating multiple images obtained by crystal analysis using the EBSD method, resulting in a standard deviation of approximately 5000 μm. 2The area-average grain size R2 of the barrier layer is calculated from the distribution of crystal grain size (diameter when the crystal area is assumed to be a circle) of the crystals contained within the measurement area (the entire thickness direction of the barrier layer is defined as the measurement area). The area-average grain size R2 of the barrier layer is measured at a point 3 cm away from the measurement point of the area-average grain size R1.

[0057] (Measuring device) A Schottky field emission scanning electron microscope equipped with an EBSD detector is used.

[0058] (Pre-processing) As a pretreatment, the barrier layer is cut perpendicular to the rolling direction (RD) to obtain a cross-section. The rolling direction of the barrier layer is determined by observing the glossy surface of the barrier layer with a metallurgical microscope and determining the direction in which linear rolling marks extend. Specifically, the procedure is as follows: First, the barrier layer to be used as a sample is cut out with a trimming razor to a size of 5 mm (perpendicular to the rolling direction) x 10 mm (in the rolling direction), and then embedded in resin. Next, using a trimming razor, the barrier layer is cut together with the resin perpendicular to the surface of the barrier layer, perpendicular to the rolling direction of the barrier layer, to expose the cross-section of the barrier layer. Next, the obtained cross-section is trimmed using a microtome. In this trimming, in order to reduce mechanical distortion of the cross-sectional shape, the microtome is used to cut approximately 1 mm perpendicular to the cross-section together with the embedded resin. Next, using an ion milling apparatus, a broad argon beam is irradiated perpendicular to the cross-section under the conditions of a projection width of 50 μm, a voltage of 6 kV, and 4 hours to prepare the measurement cross-section. This is a process of precisely exposing the cross-section of the barrier layer in order to minimize mechanical damage to the crystal structure that occurs in the previous process. In this disclosure, the "perpendicular direction" when cutting the aluminum alloy foil is confirmed under a stereomicroscope and may contain an error of about 10°. Specifically, the direction perpendicular to the rolling direction is allowed to be 80 to 100° in the rolling direction, and the direction perpendicular to the surface is allowed to be 80 to 100° relative to the surface.

[0059] (SEM conditions) The scanning electron microscope (SEM) settings used in the EBSD method are as follows: Magnification: 2000x (Standard magnification for photography is Polaroid 545) Acceleration voltage: 15kV Working distance: 15mm Sample tilt angle: 70°

[0060] (EBSD conditions) The conditions for crystal analysis using the EBSD method are as follows: Step size: 150nm Analysis conditions: The following analysis will be performed using the crystal orientation analysis software OIM (Ver. 7.3) manufactured by TSL Solutions Co., Ltd. Multiple images are stitched together, and the measurement area is approximately 5000 μm. 2 This concludes the explanation. Regarding the upper limit of the measurement area, for example, approximately 30,000 μm. 2 The following applies: The measurement area will be defined as extending from the center of the barrier layer in the thickness direction to both ends, and areas where resin is attached to the cross-section or where an acid-resistant coating is present will be excluded from the measurement area. The CI value should be 0.1 or higher, the grain boundary condition should be 0.5 degrees or higher, and the minimum grain size should be 3 steps or higher. After stitching the images together, check the pole diagram. If the center of the pole figure is shifted by more than 10°, rotate the crystal data to correct the symmetry. The reference pole figure used in this case is measured from the sample surface using XRD. When obtaining the pole figure from the surface using EBSD, perform mechanical polishing, plane milling, or electropolishing of the sample surface to eliminate the influence of the mechanical crystal structure of the sample surface, and then perform wide-area measurements. After that, rotate the pole figure obtained from the surface direction by 90° so that it matches the pole figure obtained from the same orientation as the pole figure obtained from the cross-section of the target sample. Use this pole figure as a reference. Data with a Confidence Index (CI) of 0.1 or less, as defined by TSL Solutions Co., Ltd.'s crystal orientation analysis software OIM (Ver. 7.3), will be excluded from the analysis. This eliminates data based on pretreatment resins present on both the front and back surfaces of the sample, grain boundaries in the cross-section, and amorphous materials.

[0061] The area-average crystal grain size R1 (μm) and area-average crystal grain size R2 (μm) of the barrier layer 52 can be adjusted by the material constituting the barrier layer 52, the thickness of the barrier layer 52, the material of the lid 60, etc. Furthermore, the area-average crystal grain size R1 (μm) of the barrier layer 52 can also be adjusted by the sealing conditions (temperature, pressure, time) when heat-sealing the outer film 50 and the lid 60 to form the second sealing portion 80.

[0062] For example, by increasing the Young's modulus of the barrier layer 52 (i.e., increasing the Young's modulus of the outer film 50), the ratio of the area-average grain size R1 (μm) to the area-average grain size R2 (μm) of the barrier layer 52 (R1 / R2) can be increased. The preferred Young's modulus of the barrier layer 52 will be discussed later. For example, increasing the thickness of the barrier layer 52 or using a high-strength metal are effective methods.

[0063] Furthermore, if the barrier layer 52 is formed of aluminum alloy foil, for example, if it is an aluminum alloy composition in the 8000 series according to JIS standards, the strength can be increased by adding a small amount of Si to the aluminum base metal. Also, if it is an aluminum alloy composition in the 5000 series according to JIS standards, the strength of the soft foil can be increased by solid solution strengthening by solid solution strengthening by solid solution dissolving Mg in the aluminum.

[0064] Refining the crystal grains of the metal forming the barrier layer 52 is also effective in increasing the aforementioned ratio (R1 / R2). For example, in the case of aluminum alloy compositions of the 8000 and 5000 series according to JIS standards, Al-Fe intermetallic compounds crystallize during casting, and these act as nuclei for refining the crystal grains. Furthermore, when different peripheral speed rolling (a method of rolling with rolls of different peripheral speeds) is employed, the rolled material undergoes shear deformation over the entire thickness of the plate in addition to the normal rolling deformation. As a result, crystal rotation is promoted, and the change from subgrain boundaries to large-angle grain boundaries is accelerated, generating fine crystal grains. This method is also effective in cold working, but it is more effective in hot working. In addition, increasing the number of rolling passes in the hot rolling of aluminum alloy foil and increasing the final cold rolling ratio are also effective. The higher the final cold rolling ratio from after intermediate annealing to the final thickness (for example, 80% or more), the greater the amount of strain accumulated in the aluminum alloy foil, and the finer the recrystallized grains after final annealing.

[0065] The rolling conditions for aluminum foil are adjusted by controlling factors such as the rolling rate, heating temperature, and heating time. For example, a method may include a process of homogenizing an aluminum metal or aluminum alloy ingot at approximately 500-600°C for 1-2 hours, hot rolling, cold rolling, intermediate annealing at approximately 300-450°C for 1-10 hours, cold rolling with a rolling rate of 80% or more, more preferably 90% or more, from intermediate annealing to final rolling, and final annealing at approximately 250-400°C for 30-100 hours. However, the conditions for refining the crystal grains are not limited to these.

[0066] Furthermore, it is also effective to bring the coefficient of thermal expansion of the barrier layer 52 closer to that of the material used for the lid 60 (lid body 61 or covering 62).

[0067] <1-3. Method for manufacturing energy storage devices> The energy storage device of this disclosure can be manufactured by assembling the electrode body 20, electrode terminals 30, outer film 50, and cover 60 of this disclosure. These can be assembled using, for example, known methods. A specific example of the energy storage device of this disclosure is shown below.

[0068] A pair of covers 60, to which electrode terminals 30 are attached, are placed relative to the electrode body 20, thereby electrically connecting the electrode terminals 30 and the electrode body 20. Alternatively, the covers 60 may be attached to the electrode terminals 30 that are electrically connected to the electrode body 20.

[0069] Next, the electrode body 20 and the lid 60 are wrapped in the outer film 50. The outer film 50 is wrapped around the electrode body 20 and the lid 60 while tension is applied to the outer film 50, while restricting the movement of the electrode body 20 and the lid 60 with restricting means. The restricting means is, for example, a groove into which the electrode body 20 and the lid 60 are fitted. The restricting means may also be a device that applies an external force to the electrode body 20 and the lid 60 to prevent them from moving. The restricting means may also be a device that applies a force to the electrode body 20 and the lid 60 in the opposite direction to the direction in which the outer film 50 is pulled. The restricting means may also include a roller that runs on the outer film 50 while the outer film 50 is being pulled in order to remove wrinkles in the outer film 50.

[0070] Next, the electrode body 20 is sealed with the outer casing 40. Specifically, this involves the steps of forming a first sealing portion 70 by heat-sealing the heat-sealable resin layers 53 of the outer casing film 50 that are facing each other, and forming a second sealing portion 80 by heat-sealing the heat-sealable resin layer 53 of the outer casing film 50 to the side surface of the lid 60. The order of these steps is not particularly limited, but for example, the second sealing portion 80 may be formed first, followed by the first sealing portion 70. The first sealing portion 70 and the second sealing portion 80 can be formed by heat-sealing the heat-sealable resin layers 53 using a heat sealing bar or the like.

[0071] <2-1. Laminated structure and physical properties of exterior film (exterior material for energy storage devices)> The exterior film (exterior material for energy storage devices) 50 of this disclosure is composed of a laminate comprising a barrier layer 52 and a heat-sealable resin layer 53, as shown in Figure 4, for example. In the exterior film 50, the barrier layer 52 is the outermost layer, and the heat-sealable resin layer 53 is the innermost layer. When assembling an energy storage device using the exterior film 50 and energy storage device elements (electrode body 20, electrode terminals 30, etc.), the electrode body 20 is housed in a space formed by heat-sealing the ends of the heat-sealable resin layers 53 of the exterior film 50 together with the lid 60, with the heat-sealable resin layers 53 facing each other. In the laminate constituting the exterior film 50 of this disclosure, with respect to the barrier layer 52, the side of the heat-sealable resin layer 53 on the barrier layer 52 side is inward, and the opposite side is outward.

[0072] The outer film 50 may, for example, have a base layer 51 outside the barrier layer 52, as needed, as shown in Figure 4. The outer film 50 may also, for example, have an adhesive layer 54 between the base layer 51 and the barrier layer 52, as needed, for purposes such as improving the adhesion between these layers. Furthermore, as shown in Figure 4, an adhesive layer 55 may be, for example, between the barrier layer 52 and the heat-fusible resin layer 53, as needed, for purposes such as improving the adhesion between these layers. Additionally, as shown in Figure 4, a surface coating layer (not shown) or the like may be provided on the outside of the base layer 51 (opposite the heat-fusible resin layer 53 side), as needed.

[0073] The thickness of the laminate constituting the outer film 50 is not particularly limited, but from the viewpoint of cost reduction and energy density improvement, for example, it can be about 250 μm or less, preferably about 190 μm or less, 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 outer film, which is to protect the electrode body 20, the thickness of the laminate constituting the outer film 50 can be 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 outer film 50 include, for example, approximately 35-250 μm, 35-190 μm, 35-180 μm, 35-155 μm, 35-120 μm, 45-250 μm, 45-190 μm, 45-180 μm, 45-155 μm, 45-120 μm, 60-250 μm, 60-190 μm, 60-180 μm, 60-155 μm, and 60-120 μm. In particular, approximately 60-155 μm is preferred when making the energy storage device a lightweight thin film, and approximately 155-190 μm is preferred when improving the conformability when wrapping the outer film around the electrode body.

[0074] In the exterior film 50, the ratio of the total thickness of the optional base layer 51, optional adhesive layer 54, barrier layer 52, optional adhesive layer 55, heat-fusible resin layer 53, and optional surface coating layer to the thickness (total thickness) of the laminate constituting the exterior film 50 is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. For example, if the exterior film 50 of this disclosure includes a base layer 51, an adhesive layer 54, a barrier layer 52, an adhesive layer 55, and a heat-fusible resin layer 53, the ratio of the total thickness of each of these layers to the thickness (total thickness) of the laminate constituting the exterior film 50 is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. Furthermore, even when the exterior film 50 of this disclosure is a laminate comprising a base material layer 51, an adhesive layer 54, a barrier layer 52, and a heat-fusible resin layer 53, the ratio of the total thickness of these layers to the thickness (total thickness) of the laminate constituting the exterior film 50 can be, for example, 80% or more, preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more.

[0075] From the viewpoint of more favorably demonstrating the effects of the present invention, the Young's modulus of the outer film 50 is preferably 6000 MPa or more, more preferably 8000 MPa or more, even more preferably 10000 MPa or more, and also preferably 40000 MPa or less, more preferably 35000 MPa or less, even more preferably 30000 MPa or less. Preferred ranges include approximately 6000 to 40000 MPa, approximately 6000 to 35000 MPa, approximately 6000 to 30000 MPa, approximately 8000 to 40000 MPa, approximately 8000 to 35000 MPa, approximately 8000 to 30000 MPa, approximately 10000 to 40000 MPa, approximately 10000 to 35000 MPa, and approximately 10000 to 30000 MPa. In this disclosure, the Young's modulus of the outer film is a value measured by the following method.

[0076] <Measurement of Young's modulus of exterior film> In accordance with the provisions of JIS K6251:2017, the SS curve in the TD direction of the outer film was obtained under the following measurement conditions, and the Young's modulus (MPa) was calculated from the maximum value of the slope of the SS curve. (Measurement conditions) A tensile testing machine is used. Specimen shape: Dumbbell No. 7 Specimen width: 2 mm Length of test specimen: 35 mm Thickness of the test specimen: Measured with a thickness gauge. Distance between gauge lines: 20mm Tensile speed: 50 mm / min Test environment: 23±5℃, 50±30%RH Number of measurements: Average of 3 measurements

[0077] One effective way to increase the Young's modulus of the exterior film 50 is, for example, to increase the Young's modulus of the barrier layer 52 as described above.

[0078] <2-2. Each layer that makes up the outer film> [Base material layer 51] In this disclosure, the base layer 51 is a layer provided as needed for purposes such as enabling the exterior film to function as a base material. The base layer 51 is located on the outer layer side of the exterior film.

[0079] The material used to form the base layer 51 is not particularly limited, as long as it has the function of a base material, that is, at least insulating properties. The base layer 51 can be formed using, for example, a resin, and the resin may contain additives described later.

[0080] When the base layer 51 is formed of resin, the base layer 51 can be formed of, for example, a resin film. When the base layer 51 is formed of a resin film, a pre-formed resin film may be used as the base layer 51 when manufacturing the exterior film 50 of this disclosure by laminating the base layer 51 with a barrier layer 52 or the like. Alternatively, the resin forming the base layer 51 may be formed into a film on the surface of the barrier layer 52 or the like by extrusion molding or coating, resulting in a base layer 51 formed of a resin film. The resin film may be an unstretched film or a stretched film. Examples of stretched films include uniaxially stretched films and biaxially stretched films, with biaxially stretched films being preferred. Examples of stretching methods for forming a biaxially stretched film include sequential biaxial stretching, inflation method, and simultaneous biaxial stretching. Examples of resin coating methods include roll coating, gravure coating, and extrusion coating.

[0081] Examples of resins that form the base layer 51 include polyester, polyamide, polyolefin, epoxy resin, acrylic resin, fluororesin, polyurethane, silicon resin, phenolic resin, and modified versions of these resins. The resin forming the base layer 51 may also be a copolymer of these resins, or a modified version of a copolymer. Furthermore, it may be a mixture of these resins.

[0082] The base layer 51 preferably contains these resins as its main component, and more preferably contains polyester or polyamide as its main component. Here, "main component" means that among the resin components contained in the base layer 51, the content is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more. For example, when the base layer 51 contains polyester or polyamide as its main component, it means that among the resin components contained in the base layer 51, the content of polyester or polyamide is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more.

[0083] Among these, polyester and polyamide are preferred as resins for forming the base layer 51.

[0084] Examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymerized polyesters. Examples of copolymerized polyesters include copolymerized polyesters with ethylene terephthalate as the main repeating unit. Specifically, examples include copolymerized polyesters polymerized with ethylene isophthalate using ethylene terephthalate as the main repeating unit (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 individually or in combination of two or more types.

[0085] Furthermore, specific examples of polyamides include aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, and copolymers of nylon 6 and nylon 66; hexamethylenediamine-isophthalic acid-terephthalic acid copolymer polyamides such as nylon 6I, nylon 6T, nylon 6IT, and nylon 6I6T (where I represents isophthalic acid and T represents terephthalic acid), which contain constituent 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)methaneadipamide); polyamides copolymerized with lactam components or isocyanate components such as 4,4'-diphenylmethane-diisocyanate; polyesteramide copolymers and polyether esteramide copolymers, which are copolymers of copolymerized polyamides with polyester or polyalkylene ether glycol; and other polymers of these polyamides. These polyamides may be used individually or in combination of two or more types.

[0086] The base layer 51 preferably contains at least one of polyester film, polyamide film, and polyolefin film, preferably at least one of stretched polyester film, stretched polyamide film, and stretched polyolefin film, more preferably at least one of stretched polyethylene terephthalate film, stretched polybutylene terephthalate film, stretched nylon film, and stretched polypropylene film, and even more preferably at least one of biaxially oriented polyethylene terephthalate film, biaxially oriented polybutylene terephthalate film, biaxially oriented nylon film, and biaxially oriented polypropylene film.

[0087] The base layer 51 may be a single layer or may consist of two or more layers. If the base layer 51 consists of two or more layers, the base layer 51 may be a laminate formed by laminating resin films with an adhesive, or a laminate of resin films formed by co-extruding resin into two or more layers. Furthermore, the laminate of resin films formed by co-extruding resin into two or more layers may be used as the base layer 51 in its unstretched state, or it may be used as the base layer 51 after uniaxial stretching or biaxial stretching.

[0088] Specific examples of a laminate of two or more resin films in the base layer 51 include a laminate of polyester film and nylon film, a laminate of two or more nylon films, and a laminate of two or more polyester films. Preferably, a laminate of stretched nylon film and stretched polyester film, a laminate of two or more stretched nylon films, and a laminate of two or more stretched polyester films are preferred. For example, when the base layer 51 is a laminate of two resin films, a laminate of polyester resin film and polyester resin film, a laminate of polyamide resin film and polyamide resin film, or a laminate of polyester resin film and polyamide resin film is preferred, and 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, since polyester resin is less likely to discolor when an electrolyte adheres to its surface, for example, when the base layer 51 is a laminate of two or more resin films, it is preferable that the polyester resin film is located in the outermost layer of the base layer 51. In a laminate of a polyester resin film and a polyamide resin film, the preferred thickness range for the polyester resin film is approximately 2-33 μm, 2-28 μm, 2-23 μm, 2-18 μm, 2-11 μm, 2-8 μm, 10-33 μm, 10-28 μm, 10-23 μm, 10-18 μm, 10-11 μm, 18-33 μm, and 18-28 μm. The preferred thickness range for the polyamide resin film is approximately 18-23 μm, and also includes approximately 2-33 μm, 2-28 μm, 2-23 μm, 2-18 μm, 2-11 μm, 2-8 μm, 10-33 μm, 10-28 μm, 10-23 μm, 10-18 μm, 10-11 μm, 18-33 μm, 18-28 μm, and 18-23 μm.

[0089] If the base layer 51 is a laminate of two or more resin films, the two or more resin films may be laminated with an adhesive in between. Preferred adhesives include those similar to those exemplified in the adhesive layer 54 described later. The method for laminating the two or more resin films 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 by dry lamination, it is preferable to use a polyurethane adhesive. In this case, the thickness of the adhesive is, for example, about 2 to 5 μm. Alternatively, an anchor coat layer may be formed on the resin film and then laminated. The anchor coat layer is similar to the adhesive exemplified in the adhesive layer 54 described later. In this case, the thickness of the anchor coat layer is, for example, about 0.01 to 1.0 μm.

[0090] Furthermore, at least one of the surface and interior of the base layer 51 may contain additives such as lubricants, flame retardants, antiblocking agents, antioxidants, light stabilizers, tackifiers, and antistatic agents. Only one type of additive may be used, or two or more types may be mixed and used.

[0091] In this disclosure, from the viewpoint of improving the conformability of the outer film, it is preferable that a lubricant be present on at least one of the surface and interior of the base layer 51. The lubricant is not particularly limited, but amide lubricants are preferred. Specific examples of amide 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 stearate amide, N-stearyl oleic acid amide, N-oleyl stearate amide, and N-stearyl erucic acid amide. Specific examples of methylolamides include methylol stearate amide. Specific examples of saturated fatty acid bisamides include methylenebisstearate, ethylenebiscaprate, ethylenebislaurate, ethylenebisstearate, ethylenebishydroxystearate, ethylenebisbehenamide, hexamethylenebisstearate, hexamethylenebisbehenamide, hexamethylenehydroxystearate, N,N'-distearyladipamide, and N,N'-distearylsebacinamide. Specific examples of unsaturated fatty acid bisamides include ethylenebisoleamide, ethylenebiserucamide, hexamethylenebisoleamide, N,N'-dioleyladipamide, and N,N'-dioleylsebacinamide. Specific examples of fatty acid ester amides include stearamidoethylstearate. Specific examples of aromatic bisamides include m-xylylenebisstearamide, m-xylylenebishydroxystearamide, and N,N'-distearyl isophthalamide.The lubricant may be used alone or in combination of two or more kinds, and it is preferable to use two or more kinds in combination.

[0092] When a lubricant is present on the surface of the base material layer 51, its amount of presence is not particularly limited. For example, it is about 3 mg / m 2 or more, preferably about 4 mg / m 2 or more, about 5 mg / m 2 or more. Further, as the amount of the lubricant present on the surface of the base material layer 51, for example, it is about 15 mg / m 2 or less, preferably about 14 mg / m 2 or less, about 10 mg / m 2 or less. Also, the preferable range of the amount of the lubricant present on the surface of the base material layer 51 is about 3 to 15 mg / m 2 level, about 3 to 14 mg / m 2 level, about 3 to 10 mg / m 2 level, about 4 to 15 mg / m 2 level, about 4 to 14 mg / m 2 level, about 4 to 10 mg / m 2 level, about 5 to 15 mg / m 2 level, about 5 to 14 mg / m 2 level, about 5 to 10 mg / m 2 level.

[0093] The lubricant present on the surface of the base material layer 51 may be one obtained by exuding the lubricant contained in the resin constituting the base material layer 51, or may be one obtained by coating the surface of the base material layer 51 with a lubricant.

[0094] The thickness of the base layer 51 is not particularly limited as long as it performs its function as a base material, but for example, it can be about 3 μm or more, preferably about 10 μm or more. Also, examples of the thickness of the base layer 51 include about 50 μm or less, preferably about 35 μm or less, about 11 μm or less, and about 8 μm or less. Furthermore, preferred ranges for the thickness of the base layer 51 include about 3 to 50 μm, about 3 to 35 μm, about 3 to 11 μm, about 3 to 8 μm, about 10 to 50 μm, and about 10 to 35 μm. In particular, when making a lightweight thin film for energy storage devices, about 3 to 35 μm, about 3 to 11 μm, and about 3 to 8 μm are preferred, and when improving conformability, about 35 to 50 μm is preferred. When the base layer 51 is a laminate of two or more resin films, the thickness of the resin film constituting each layer is not particularly limited, but for example, about 2 μm or more, preferably about 10 μm or more and about 18 μm or more, respectively. Furthermore, the thickness of the resin film constituting each layer can be, for example, about 33 μm or less, preferably about 28 μm or less, about 23 μm or less, about 18 μm or less, about 11 μm or less, or about 8 μm or less. In addition, preferred ranges for the thickness of the resin film constituting each layer can be about 2 to 33 μm, about 2 to 28 μm, about 2 to 23 μm, about 2 to 18 μm, about 2 to 11 μm, about 2 to 8 μm, about 10 to 33 μm, about 10 to 28 μm, about 10 to 23 μm, about 10 to 18 μm, about 10 to 11 μm, about 18 to 33 μm, about 18 to 28 μm, or about 18 to 23 μm.

[0095] [Adhesive layer 54] In the exterior film of this disclosure, the adhesive layer 54 is a layer provided between the substrate layer 51 and the barrier layer 52 as necessary, for the purpose of improving the adhesion between them.

[0096] The adhesive layer 54 is formed by an adhesive capable of bonding the substrate layer 51 and the barrier layer 52. The adhesive used to form the adhesive layer 54 is not limited, but may be a chemical reaction type, solvent evaporation type, heat melt type, hot pressure type, etc. It may also be a two-component curing adhesive (two-part adhesive), a one-component curing adhesive (one-part adhesive), or a resin that does not undergo a curing reaction. Furthermore, the adhesive layer 54 may be a single layer or a multi-layer layer.

[0097] Specifically, adhesive components included in adhesives include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, copolymerized polyester; polyethers; polyurethanes; epoxy resins; phenolic resins; polyamides such as nylon 6, nylon 66, nylon 12, copolymerized 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 individually or in combination of two or more. Among these adhesive components, polyurethane adhesives are particularly preferred. Furthermore, the adhesive strength of these adhesive resins can be increased by using an appropriate curing agent. The curing agent is selected appropriately from polyisocyanates, polyfunctional epoxy resins, oxazoline group-containing polymers, polyamine resins, acid anhydrides, etc., depending on the functional groups of the adhesive components.

[0098] Examples of polyurethane adhesives include polyurethane adhesives comprising a first agent containing a polyol compound and a second agent containing an isocyanate compound. Preferably, a two-component curing type polyurethane adhesive is used, in which a polyol such as polyester polyol, polyether polyol, and acrylic polyol is used as the first agent and an aromatic or aliphatic polyisocyanate is used as the second agent. Another example of a polyurethane adhesive is a polyurethane adhesive comprising a polyurethane compound obtained by pre-reacting a polyol compound with an isocyanate compound and an isocyanate compound. Another example of a polyurethane adhesive is a polyurethane adhesive comprising a polyurethane compound obtained by pre-reacting a polyol compound with an isocyanate compound and an isocyanate compound and an isocyanate compound. Another example of a polyurethane adhesive is a polyurethane adhesive obtained by curing a polyurethane compound obtained by pre-reacting a polyol compound with an isocyanate compound by reacting it with moisture such as air. As the polyol compound, it is preferable to use a polyester polyol having hydroxyl groups on the side chains in addition to the hydroxyl groups at the ends of the repeating units. Examples of the second agent are aliphatic, alicyclic, aromatic, and aromaticaliphatic isocyanate compounds. Examples of isocyanate compounds include hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), hydrogenated XDI (H6XDI), hydrogenated MDI (H12MDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and naphthalene diisocyanate (NDI). Also, polyfunctional isocyanate modified compounds derived from one or more of these diisocyanates are used. Furthermore, polymers (e.g., trimers) can be used as polyisocyanate compounds. Examples of such polymers include adducts, biuretes, and nurates. The adhesive layer 54 is formed from a polyurethane adhesive, which provides the outer film with excellent electrolyte resistance, preventing the substrate layer 51 from peeling off even if electrolyte adheres to the sides.

[0099] Furthermore, the adhesive layer 54 may contain other components as long as they do not impair adhesion, and may contain colorants, thermoplastic elastomers, tackifiers, fillers, etc. The presence of a colorant in the adhesive layer 54 allows the exterior film to be colored. Known colorants such as pigments and dyes can be used. In addition, only one type of colorant may be used, or two or more types may be mixed and used.

[0100] The type of pigment is not particularly limited, as long as it does not impair the adhesion of the adhesive layer 54. Examples of organic pigments include azo, phthalocyanine, quinacridone, anthraquinone, dioxazine, indigothioindigo, perinone-perylene, isoindorenine, and benzimidazolon pigments. Examples of inorganic pigments include carbon black, titanium dioxide, cadmium, lead, chromium oxide, and iron pigments. Other examples include fine mica powder and fish scale foil.

[0101] Among colorants, carbon black is preferred for, for example, to give the exterior film a black appearance. Furthermore, from the viewpoint of dissipating heat generated from the energy storage device, mica is preferred.

[0102] The average particle size of the pigment is not particularly limited, but for example, it can be about 0.05 to 5 μm, preferably about 0.08 to 2 μm. The average particle size of the pigment is the median diameter measured by a laser diffraction / scattering particle size distribution analyzer.

[0103] The pigment content in the adhesive layer 54 is not particularly limited as long as the outer film is colored, and for example, it is about 5 to 60% by mass, preferably 10 to 40% by mass.

[0104] The thickness of the adhesive layer 54 is not particularly limited as long as it can bond the substrate layer 51 and the barrier layer 52, but for example, it is about 1 μm or more and about 2 μm or more. Alternatively, the thickness of the adhesive layer 54 can be about 10 μm or less and about 5 μm or less. Preferred ranges for the thickness of the adhesive layer 54 include about 1 to 10 μm, about 1 to 5 μm, about 2 to 10 μm, and about 2 to 5 μm.

[0105] [Colored layer] The colored layer is a layer provided between the base layer 51 and the barrier layer 52 as needed (not shown in the figure). If an adhesive layer 54 is present, the colored layer may be provided between the base layer 51 and the adhesive layer 54, and between the adhesive layer 54 and the barrier layer 52. Alternatively, the colored layer may be provided on the outside of the base layer 51. By providing a colored layer, the outer film can be colored.

[0106] The colored layer can be formed, for example, by applying an ink containing a coloring agent to the surface of the substrate layer 51 or the surface of the barrier layer 52. Known coloring agents such as pigments and dyes can be used. In addition, only one type of coloring agent may be used, or two or more types may be mixed and used.

[0107] Specific examples of colorants included in the colored layer are the same as those exemplified in the section for [adhesive layer 54].

[0108] [Barrier layer 52] In the exterior film, the barrier layer 52 is a layer that at least prevents the intrusion of moisture.

[0109] Examples of barrier layers 52 include metal foils, vapor-deposited films, and resin layers that have barrier properties. Examples of vapor-deposited films include metal vapor-deposited films, inorganic oxide vapor-deposited films, and carbon-containing inorganic oxide vapor-deposited films. Examples of resin layers include fluorine-containing resins such as polymers mainly composed of polyvinylidene chloride, chlorotrifluoroethylene (CTFE), polymers mainly composed of tetrafluoroethylene (TFE), polymers having fluoroalkyl groups, and polymers mainly composed of fluoroalkyl units, as well as ethylene vinyl alcohol copolymers. In addition, a resin film having at least one of these vapor-deposited films and resin layers can also be provided as barrier layer 52. Multiple layers of barrier layer 52 may be provided. Preferably, the barrier layer 52 includes a layer composed of a metal material. The metal materials constituting the barrier layer 52 include, specifically, aluminum, aluminum alloys, titanium, titanium alloys, steel (including stainless steel), copper, copper alloys, nickel, nickel alloys, magnesium, magnesium alloys, niobium, and iron. Among these, aluminum alloys, stainless steel, titanium steel, and steel plates are preferred. When used as a metal foil, it is preferable to include at least one of aluminum alloy foil and stainless steel foil.

[0110] In the barrier layer 52, the layer composed of the aforementioned metal material may include recycled metal material. Examples of recycled metal material include recycled aluminum alloy, stainless steel, titanium steel, or steel sheet. These recycled materials can each be obtained by known methods. Recycled aluminum alloy can be obtained, for example, by the manufacturing method described in International Publication No. 2022 / 092231. The barrier layer 52 may be composed solely of recycled material, or it may be composed of a mixture of recycled material and virgin material. Recycled metal material refers to metal material that has been recovered, isolated, and purified from various products used in the market or waste generated from manufacturing processes to make it reusable. Virgin metal material refers to new metal material refined from natural metal resources (raw materials) that is not recycled material.

[0111] From the viewpoint of improving the conformability when wrapping the outer film around the electrode body, the aluminum alloy foil is more preferably a soft aluminum alloy foil made of, for example, an annealed aluminum alloy, and from the viewpoint of further improving conformability, it is more preferably an aluminum alloy foil containing iron. In an iron-containing aluminum alloy foil (100 mass%), the iron content is preferably 0.1 to 9.0 mass%, and more preferably 0.5 to 2.0 mass%. By having an iron content of 0.1 mass% or more, an outer film with better conformability can be obtained. By having an iron content of 9.0 mass% or less, an outer film with better flexibility can be obtained. Examples of soft aluminum alloy foils include aluminum alloy foils having compositions specified in JIS H4160:1994 A8021H-O, JIS H4160:1994 A8079H-O, JIS H4000:2014 A8021P-O, or JIS H4000:2014 A8079P-O. Silicon, magnesium, copper, manganese, etc., may also be added as needed. Softening can be achieved through annealing or other treatments.

[0112] From the viewpoint of improving the mechanical strength of the outer film 50, it is more preferable that the aluminum alloy foil is a hard aluminum alloy foil composed of, for example, a work-hardened aluminum alloy. Examples of hard aluminum alloy foils include aluminum alloy foils having compositions specified in JIS H4160:1994 A8021H-H18, JIS H4160:1994 A8079H-H18, JIS H4000:2014 A8021P-H14, or JIS H4000:2014 A8079P-H14. From the viewpoint of improving the mechanical strength of the outer film 50, it is more preferable that the aluminum alloy foil is an aluminum alloy foil containing magnesium. In an aluminum alloy foil containing magnesium (100% by mass), the magnesium content is preferably 0.2 to 5.6% by mass, and more preferably 0.2 to 3.0% by mass. Examples of aluminum alloy foils containing magnesium include those having compositions specified in JIS H4000:2017 A5005P-O, JIS H4000:2017 A5050P-O, and JIS H4000:2017 A5052P-O. Furthermore, from the viewpoint of improving the mechanical strength of the outer film 50, it is also preferable that the aluminum alloy foil contains manganese. In aluminum alloy foil containing manganese (100% by mass), the manganese content is preferably 0.3 to 1.5% by mass, and more preferably 1.0 to 1.5% by mass. Examples of aluminum alloy foils containing manganese include those having compositions specified in JIS H4000:2017 A3003P-O, JIS H4000:2017 A3103P-O, JIS H4000:2017 A3004P-O, and JIS H4000:2017 A3104P-O.

[0113] Furthermore, examples of stainless steel foils include austenitic, ferritic, austenitic-ferritic, martensitic, and precipitation-hardening stainless steel foils. From the viewpoint of providing an outer film with excellent conformability, it is preferable that the stainless steel foil be made of austenitic stainless steel.

[0114] Specific examples of austenitic stainless steels that make up stainless steel foil include SUS304, SUS301, and SUS316L, with SUS304 being particularly preferred among these.

[0115] In the case of metal foil, the thickness of the barrier layer 52 should at least function as a barrier layer that prevents moisture from penetrating, for example, about 9 to 200 μm. The thickness of the barrier layer 52 is preferably about 200 μm or less, more preferably about 150 μm or less, even more preferably about 120 μm or less, even more preferably about 100 μm or less, and particularly preferably about 90 μm or less. Also, the thickness of the barrier layer 52 is preferably about 10 μm or more, even more preferably about 20 μm or more, and more preferably about 25 μm or more. Furthermore, preferred thickness ranges for the barrier layer 52 include approximately 9-200 μm, 9-150 μm, 9-120 μm, 9-100 μm, 9-90 μm, 10-200 μm, 10-150 μm, 10-120 μm, 10-100 μm, 10-90 μm, 20-200 μm, 20-150 μm, 20-120 μm, 20-100 μm, 20-90 μm, 25-200 μm, 25-150 μm, 25-120 μm, 25-100 μm, and 25-90 μm. When the barrier layer 52 is made of aluminum alloy foil, from the viewpoint of providing the outer film 50 with high conformability and high rigidity, the thickness of the barrier layer 52 is preferably about 40 μm or more, more preferably about 60 μm or more, even more preferably about 70 μm or more, even more preferably about 80 μm or more, and also preferably about 200 μm or less, more preferably about 150 μm or less, even more preferably about 120 μm or less, even more preferably about 100 μm or less, and even more preferably about 90 μm or less. The ranges are approximately 40-200 μm, 40-150 μm, 40-120 μm, 40-100 μm, 40-90 μm, 60-200 μm, 60-150 μm, 60-120 μm, 60-100 μm, 60-90 μm, 70-200 μm, 70-150 μm, 70-120 μm, 70-100 μm, 70-90 μm, 80-200 μm, 80-150 μm, 80-120 μm, 80-100 μm, and 80-90 μm. The high conformability of the outer film 50 can contribute to increasing the capacity of the energy storage device.Furthermore, as the capacity of the energy storage device increases, the weight of the energy storage device increases, but by increasing the rigidity of the outer film 50, it is possible to contribute to the high sealing performance of the energy storage device. In particular, when the barrier layer 52 is made of stainless steel foil, the thickness of the stainless steel foil is preferably about 80 μm or less, more preferably about 70 μm or less, even more preferably about 65 μm or less, even more preferably about 60 μm or less, and especially preferably about 50 μm or less. Also, the thickness of the stainless steel foil is preferably about 10 μm or more, more preferably about 15 μm or more. Furthermore, preferred ranges for the thickness of the stainless steel foil include about 10 to 80 μm, about 10 to 70 μm, about 10 to 65 μm, about 10 to 60 μm, about 10 to 50 μm, about 15 to 80 μm, about 15 to 70 μm, about 15 to 65 μm, about 15 to 60 μm, and about 15 to 50 μm.

[0116] Furthermore, if the barrier layer 52 is a metal foil, it is preferable to provide a corrosion-resistant coating on at least the side opposite to the substrate layer to prevent dissolution and corrosion. The barrier layer 52 may have a corrosion-resistant coating on both sides. Here, a corrosion-resistant coating refers to a thin film that provides corrosion resistance (e.g., acid resistance, alkali resistance, etc.) to the barrier layer by performing treatments such as hot water modification treatment such as boehmite treatment, chemical conversion treatment, anodizing treatment, plating treatment with nickel or chromium, or corrosion prevention treatment by applying a coating agent to the surface of the barrier layer. Specifically, a corrosion-resistant coating means a coating that improves the acid resistance of the barrier layer (acid-resistant coating), a coating that improves the alkali resistance of the barrier layer (alkali-resistant coating), etc. One type of treatment may be performed to form the corrosion-resistant coating, or two or more types may be combined. In addition, it is possible to have multiple layers instead of just one. Furthermore, among these treatments, hot water modification treatment and anodizing treatment are treatments that dissolve the surface of the metal foil with a treatment agent and form a metal compound with excellent corrosion resistance. These processes may also be included in the definition of chemical conversion treatment. Furthermore, if the barrier layer 52 has a corrosion-resistant coating, the barrier layer 52 shall include the corrosion-resistant coating.

[0117] The corrosion-resistant coating prevents delamination between the barrier layer (e.g., aluminum alloy foil) and the base layer during the molding of the outer film, prevents dissolution and corrosion of the barrier layer surface due to hydrogen fluoride generated by the reaction of electrolytes and moisture, and in particular prevents the dissolution and corrosion of aluminum oxide present on the barrier layer surface when the barrier layer is aluminum alloy foil, and improves the adhesion (wettability) of the barrier layer surface, thereby preventing delamination between the base layer and the barrier layer during heat sealing and molding.

[0118] Various corrosion-resistant coatings are known to be formed by chemical conversion treatments, mainly including corrosion-resistant coatings containing at least one of the following: phosphates, chromates, fluorides, triazinethiol compounds, and rare earth oxides. Examples of chemical conversion treatments using phosphates and chromates include chromate treatment, phosphate chromate treatment, phosphate-chromate treatment, and chromate treatment. Examples of chromium compounds used in these treatments include chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium biphosphate, acetyl acetate chromate, chromium chloride, and potassium chromium sulfate. Examples of phosphorus compounds used in these treatments include sodium phosphate, potassium phosphate, ammonium phosphate, and polyphosphate. Examples of chromate treatments include etching chromate treatment, electrolytic chromate treatment, and coating-type chromate treatment, with coating-type chromate treatment being preferred. This coating-type chromate treatment involves first degreasing at least the inner surface of a barrier layer (e.g., aluminum alloy foil) using a well-known treatment method such as alkaline immersion, electrolytic cleaning, acid cleaning, electrolytic acid cleaning, or acid activation. Then, a treatment solution mainly composed of metal phosphate salts such as chromium phosphate, titanium phosphate, zirconium phosphate, and zinc phosphate, or mixtures thereof, or a treatment solution mainly composed of nonmetallic phosphates and mixtures thereof, or a treatment solution consisting of a mixture of these with synthetic resins, etc., is applied to the degreased surface using a well-known coating method such as roll coating, gravure printing, or immersion, and then dried. Various solvents can be used as the treatment solution, such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester-based solvents, and ether-based solvents, with water being preferred. Furthermore, examples of resin components used in this process include polymers such as phenolic resins and acrylic resins, and examples of chromate treatment using an amination phenol polymer having repeating units represented by the following general formulas (1) to (4). In this amination phenol polymer, the repeating units represented by the following general formulas (1) to (4) may be included individually or in any combination of two or more types.The acrylic resin is preferably polyacrylic acid, acrylate methacrylate copolymer, acrylate maleic acid copolymer, acrylate styrene copolymer, or derivatives thereof such as sodium salts, ammonium salts, or amine salts. Derivatives of polyacrylic acid, such as ammonium salts, sodium salts, or amine salts of polyacrylic acid, are particularly preferred. In this disclosure, polyacrylic acid means a polymer of acrylic acid. Furthermore, the acrylic resin is also preferably a copolymer of acrylic acid and a dicarboxylic acid or dicarboxylic acid anhydride, and also preferably an ammonium salt, sodium salt, or amine salt of a copolymer of acrylic acid and a dicarboxylic acid or dicarboxylic acid anhydride. Only one type of acrylic resin may be used, or two or more types may be mixed and used.

[0119] [ka]

[0120] [ka]

[0121] [ka]

[0122] [ka]

[0123] In general formulas (1) to (4), X represents a hydrogen atom, a hydroxyl group, an alkyl group, a hydroxyalkyl group, an allyl group, or a benzyl group. Also, R 1 and R 2 Each of these represents a hydroxyl group, an alkyl group, or a hydroxyalkyl group, either identical or different. In general formulas (1) to (4), X and R 1 and R 2Examples of alkyl groups represented by include linear or branched alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl groups. Also, X, R 1 and R 2 Examples of hydroxyalkyl groups represented by include linear or branched alkyl groups having 1 to 4 carbon atoms with one hydroxyl group substituted, such as hydroxymethyl group, 1-hydroxyethyl group, 2-hydroxyethyl group, 1-hydroxypropyl group, 2-hydroxypropyl group, 3-hydroxypropyl group, 1-hydroxybutyl group, 2-hydroxybutyl group, 3-hydroxybutyl group, and 4-hydroxybutyl group. In general formulas (1) to (4), X and R 1 and R 2 The alkyl group and hydroxyalkyl group shown may be the same or different. In general formulas (1) to (4), X is preferably a hydrogen atom, a hydroxyl group, or a hydroxyalkyl group. The number-average molecular weight of the amination phenol polymer having repeating units represented by general formulas (1) to (4) is preferably about 500 to 1,000,000, and more preferably about 1,000 to 20,000. The amination phenol polymer is produced, for example, by polycondensing a phenol compound or naphthol compound with formaldehyde to produce a polymer consisting of repeating units represented by the above general formula (1) or general formula (3), and then adding formaldehyde and amine (R 1 R 2 Using NH) to form the functional group (-CH2NR 1 R 2 It is produced by introducing ) into the polymer obtained above. The amination phenol polymer can be used alone or in a mixture of two or more types.

[0124] Another example of a corrosion-resistant coating is a thin film formed by a coating-type corrosion prevention treatment, which involves applying a coating agent containing at least one selected from the group consisting of rare earth element oxide sols, anionic polymers, and cationic polymers. The coating agent may further contain phosphoric acid or phosphate, and a crosslinking agent for crosslinking the polymer. In the rare earth element oxide sol, fine particles of rare earth element oxides (for example, particles with an average particle size of 100 nm or less) are 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 from the viewpoint of further improving adhesion. The rare earth element oxides contained in the corrosion-resistant coating can be used individually or in combination of two or more. Various solvents can be used as the liquid dispersion medium for the rare earth element oxide sol, such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester-based solvents, and ether-based solvents, with water being preferred. Preferred cationic polymers include, for example, polyethyleneimine, ionic polymer complexes comprising polyethyleneimine and a polymer having a carboxylic acid, primary amine-grafted acrylic resins obtained by graft polymerization of a primary amine onto an acrylic main skeleton, polyallylamine or its derivatives, and amination phenols. Preferred anionic polymers are poly(meth)acrylic acid or its salts, or copolymers mainly composed of (meth)acrylic acid or its salts. Furthermore, the crosslinking agent is preferably at least one selected from the group consisting of a compound having one of the functional groups of isocyanate, glycidyl, carboxyl, or oxazoline, and a silane coupling agent. Additionally, the phosphoric acid or phosphate is preferably condensed phosphoric acid or condensed phosphate.

[0125] An example of a corrosion-resistant coating is one formed by dispersing metal oxides such as aluminum oxide, titanium oxide, cerium oxide, and tin oxide, or fine particles of barium sulfate, in phosphoric acid, applying this mixture to the surface of a barrier layer, and then baking it at a temperature of 150°C or higher.

[0126] The corrosion-resistant coating may, if necessary, be a laminated structure in which at least one of a cationic polymer and an anionic polymer is further laminated. Examples of cationic and anionic polymers include those mentioned above.

[0127] Furthermore, the composition of the corrosion-resistant coating can be analyzed, for example, using time-of-flight secondary ion mass spectrometry.

[0128] The amount of corrosion-resistant film to be formed on the surface of the barrier layer 52 in the chemical conversion treatment is not particularly limited, but for example, in the case of coating-type chromate treatment, the surface of the barrier layer 52 is 1 m 2 It is desirable that the product contains, for example, about 0.5 to 50 mg of chromium-based chromium, preferably about 1.0 to 40 mg of phosphorus-based chromium

[0129] The thickness of the corrosion-resistant coating is not particularly limited, but from the viewpoint of the cohesive force of the coating and the adhesion force with the barrier layer and the heat-fusible resin layer, it 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. 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 beam energy loss spectroscopy. By analyzing the composition of the corrosion-resistant coating using time-of-flight secondary ion mass spectrometry, for example, secondary ions consisting of Ce, P, and O (e.g., Ce2PO4) can be identified. + CePO4 - (at least one of the above), or, for example, a secondary ion consisting of Cr, P, and O (e.g., CrPO2) + , CrPO4 - Peaks originating from at least one of the following are detected.

[0130] The chemical conversion treatment is carried out by applying a solution containing compounds used to form a corrosion-resistant film to the surface of the barrier layer using methods such as bar coating, roll coating, gravure coating, or immersion, and then heating the barrier layer to a temperature of approximately 70-200°C. Alternatively, before applying the chemical conversion treatment to the barrier layer, it may be subjected to a degreasing treatment using methods such as alkaline immersion, electrolytic cleaning, acid cleaning, or electrolytic acid cleaning. This degreasing treatment makes it possible to perform the chemical conversion treatment on the surface of the barrier layer more efficiently. Furthermore, by using an acid degreasing agent, which is a fluorine-containing compound dissolved in an inorganic acid, it is possible to not only degrease the metal foil but also form a fluoride of the passive metal; in such cases, only the degreasing treatment may be performed.

[0131] [Thermal adhesive resin layer 53] In the exterior film of this disclosure, the heat-sealable resin layer 53 is the innermost layer and is a layer (sealant layer) that performs the function of sealing the electrode body 20 by heat fusion during the assembly of the energy storage device.

[0132] The resin constituting the heat-fusible resin layer 53 is not particularly limited as long as it is heat-fusible, but resins containing a polyolefin backbone, such as polyolefins and acid-modified polyolefins, are preferred. The presence of a polyolefin backbone in the resin constituting the heat-fusible resin layer 53 can be analyzed, for example, by infrared spectroscopy or gas chromatography-mass spectrometry. Furthermore, when the resin constituting the heat-fusible resin layer 53 is analyzed by infrared spectroscopy, it is preferable that a peak originating from maleic anhydride is detected. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, a peak originating from maleic anhydride is detected at wavenumber 1760 cm⁻¹. -1 Nearby wave frequency 1780cm -1 A peak derived from maleic anhydride is detected in the vicinity. If the heat-fusible resin layer 53 is composed of maleic anhydride-modified polyolefin, a peak derived from maleic anhydride will be detected when measured by infrared spectroscopy. However, if the degree of acid modification is low, the peak may become small and not be detected. In that case, analysis is possible by nuclear magnetic resonance spectroscopy.

[0133] The heat-fusible resin layer 53 preferably contains a resin containing a polyolefin skeleton as its main component, more preferably contains polyolefin as its main component, and even more preferably contains polypropylene as its main component. Here, "main component" means a resin component in which the content of the resin components contained in the heat-fusible resin layer 53 is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more. For example, if the heat-fusible resin layer 53 contains polypropylene as its main component, it means that the content of polypropylene in the resin components contained in the heat-fusible resin layer 53 is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more.

[0134] Examples of polyolefins include polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; polypropylene such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymer of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymer of propylene and ethylene); propylene-α-olefin copolymers; and ethylene-butene-propylene terpolymers. Among these, polypropylene is preferred. When polyolefin resins are copolymers, they may be block copolymers or random copolymers. These polyolefin resins may be used individually or in combination of two or more.

[0135] Furthermore, the polyolefin may be a cyclic polyolefin. A cyclic polyolefin is a copolymer of an olefin and a cyclic monomer. Examples of olefins that are constituent monomers of the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, styrene, butadiene, isoprene, and the like. Examples of cyclic monomers that are constituent monomers of the cyclic polyolefin include cyclic alkenes such as norbornene; and cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, norbornadiene, and the like. Among these, cyclic alkenes are preferred, and norbornene is more preferred.

[0136] Furthermore, the polyolefin may be an acid-modified polyolefin. An acid-modified polyolefin is a polymer modified by block polymerization or graft polymerization of a polyolefin with an acid component. As the polyolefin to be acid-modified, the above-mentioned polyolefin, copolymers obtained by copolymerizing the above-mentioned polyolefin with polar molecules such as acrylic acid or methacrylic acid, or polymers such as cross-linked polyolefins can also be used. Examples of acid components used for acid modification include carboxylic acids or their anhydrides such as maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

[0137] Acid-modified polyolefins may also be acid-modified cyclic polyolefins. Acid-modified cyclic polyolefins are polymers obtained by copolymerizing a portion of the monomers constituting a cyclic polyolefin with an acid component, or by block polymerization or graft polymerization of an acid component to a cyclic polyolefin. The cyclic polyolefin to be acid-modified is the same as described above. Furthermore, the acid component used for acid modification is the same as the acid component used for modifying the polyolefin described above.

[0138] 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.

[0139] The heat-sealable resin layer 53 may be formed by a single resin or by a blended polymer of two or more resins. Furthermore, the heat-sealable resin layer 53 may be formed as a single layer or as two or more layers of the same or different resins.

[0140] When manufacturing the exterior film 50 of this disclosure by laminating the heat-fusible resin layer 53 with a barrier layer 52, an adhesive layer 55, etc., a pre-formed resin film may be used as the heat-fusible resin layer 53. Alternatively, the heat-fusible resin that forms the heat-fusible resin layer 53 may be formed into a film on the surface of the barrier layer 52, adhesive layer 55, etc. by extrusion molding or coating, etc., to form the heat-fusible resin layer 53 from a resin film.

[0141] Furthermore, the heat-fusible resin layer 53 may contain a lubricant or the like as needed. When the heat-fusible resin layer 53 contains a lubricant, the conformability when wrapping the outer film around the electrode body can be improved. The lubricant is not particularly limited, and known lubricants can be used.

[0142] The lubricant is not particularly limited, but amide-based lubricants are preferred. Specific examples of lubricants include those exemplified in the base layer 51. The lubricant may be used alone or in combination of two or more types, with a combination of two or more being preferable.

[0143] In this disclosure, from the viewpoint of improving the conformability when wrapping the outer film around the electrode body, it is preferable that a lubricant be present on at least one of the surface and interior of the heat-fusible resin layer 53. The lubricant is not particularly limited, but amide lubricants are preferred. Specific examples of amide 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 stearate amide, N-stearyl oleic acid amide, N-oleyl stearate amide, and N-stearyl erucic acid amide. Specific examples of methylolamides include methylol stearate amide. Specific examples of saturated fatty acid bisamides include methylenebisstearate, ethylenebiscaprate, ethylenebislaurate, ethylenebisstearate, ethylenebishydroxystearate, ethylenebisbehenamide, hexamethylenebisstearate, hexamethylenebisbehenamide, hexamethylenehydroxystearate, N,N'-distearyladipamide, and N,N'-distearylsebacinamide. Specific examples of unsaturated fatty acid bisamides include ethylenebisoleamide, ethylenebiserucamide, hexamethylenebisoleamide, N,N'-dioleyladipamide, and N,N'-dioleylsebacinamide. Specific examples of fatty acid ester amides include stearamidoethylstearate. Specific examples of aromatic bisamides include m-xylylenebisstearamide, m-xylylenebishydroxystearamide, and N,N'-distearyl isophthalamide.The lubricant may be used alone or in combination of two or more types, and it is preferable to use a combination of two or more types.

[0144] When a lubricant is present on the surface of the heat-fusible resin layer 53, there are no particular restrictions on the amount present, but from the viewpoint of improving the conformability of the outer film, it is preferably about 1 mg / m². 2 More preferably, approximately 3 mg / m² 2 More preferably, about 5 mg / m² 2 More preferably, about 10 mg / m² 2 More preferably, about 15 mg / m² 2 The above is true, and preferably about 50 mg / m² 2 More preferably, about 40 mg / m² 2 The following are preferred ranges, with a preferred range being 1 to 50 mg / m². 2 degree, 1~40mg / m 2 degree, 3~50mg / m 2 degree, 3~40mg / m 2 degree, 5~50mg / m 2 degree, 5~40mg / m 2 degree, 10~50mg / m 2 degree, 10~40mg / m 2 degree, 15~50mg / m 2 degree, 15~40mg / m 2 The degree can be described as follows.

[0145] When a lubricant is present inside the heat-fusible resin layer 53, there are no particular restrictions on its amount, but from the viewpoint of improving the conformability of the outer film, it is preferably about 100 ppm or more, more preferably about 300 ppm or more, even more preferably about 500 ppm or more, and also preferably about 3000 ppm or less, more preferably about 2000 ppm or less. Preferred ranges include about 100 to 3000 ppm, about 100 to 2000 ppm, about 300 to 3000 ppm, about 300 to 2000 ppm, about 500 to 3000 ppm, and about 500 to 2000 ppm. When two or more types of lubricants are present inside the heat-fusible resin layer 53, the above amount of lubricant is the total amount of lubricant. Furthermore, when two or more types of lubricants are present inside the heat-fusible resin layer 53, the amount of the first type of lubricant is not particularly limited, but from the viewpoint of improving the conformability of the outer film, it is preferably about 100 ppm or more, more preferably about 300 ppm or more, even more preferably about 500 ppm or more, and also preferably about 3000 ppm or less, more preferably about 2000 ppm or less. Preferred ranges include about 100 to 3000 ppm, about 100 to 2000 ppm, about 300 to 3000 ppm, about 300 to 2000 ppm, about 500 to 3000 ppm, and about 500 to 2000 ppm. The amount of the second type of lubricant is not particularly limited, but from the viewpoint of improving the conformability of the outer film, it is preferably about 50 ppm or more, more preferably about 100 ppm or more, even more preferably about 200 ppm or more, and also preferably about 1500 ppm or less, more preferably about 1000 ppm or less. Preferred ranges include about 50 to 1500 ppm, about 50 to 1000 ppm, about 100 to 1500 ppm, about 100 to 1000 ppm, about 200 to 1500 ppm, and about 200 to 1000 ppm.

[0146] The lubricant present on the surface of the heat-fusible resin layer 53 may be a lubricant contained in the resin constituting the heat-fusible resin layer 53 that has seeped out, or a lubricant may be applied to the surface of the heat-fusible resin layer 53.

[0147] Furthermore, the thickness of the heat-fusible resin layer 53 is not particularly limited as long as the heat-fusible resin layers heat-fuse together to seal the electrode body, but for example, it can be about 100 μm or less, preferably about 85 μm or less, and more preferably about 15 to 85 μm. For example, if the thickness of the adhesive layer 55 described later is 10 μm or more, the thickness of the heat-fusible resin layer 53 can be preferably about 85 μm or less, and more preferably about 15 to 45 μm. For example, if the thickness of the adhesive layer 55 described later is less than 10 μm or if the adhesive layer 55 is not provided, the thickness of the heat-fusible resin layer 53 can be preferably about 20 μm or more, and more preferably about 35 to 85 μm.

[0148] [Adhesive layer 55] In the exterior film of this disclosure, the adhesive layer 55 is a layer provided as necessary between the barrier layer 52 (or corrosion-resistant coating) and the heat-fusible resin layer 53 in order to firmly bond them together.

[0149] The adhesive layer 55 is formed of a resin capable of bonding the barrier layer 52 and the heat-fusible resin layer 53. The resin used to form the adhesive layer 55 can be, for example, the same type of adhesive exemplified in the adhesive layer 54.

[0150] Furthermore, from the viewpoint of firmly bonding the adhesive layer 55 and the heat-fusible resin layer 53, it is preferable that the resin used to form the adhesive layer 55 contains a polyolefin skeleton, and examples of such resins include the polyolefins, acid-modified polyolefins, cyclic polyolefins, and acid-modified cyclic polyolefins exemplified in the heat-fusible resin layer 53 mentioned above. On the other hand, from the viewpoint of firmly bonding the barrier layer 52 and the adhesive layer 55, it is preferable that the adhesive layer 55 contains an acid-modified polyolefin. Examples of acid-modified components include dicarboxylic acids such as maleic acid, itaconic acid, succinic acid, and adipic acid, as well as their anhydrides, acrylic acid, and methacrylic acid, but maleic anhydride is most preferred in terms of ease of modification and versatility. Furthermore, from the viewpoint of the heat resistance of the outer film, it is preferable that the olefin component be a polypropylene-based resin, and it is most preferable that the adhesive layer 55 contains maleic anhydride-modified polypropylene.

[0151] When the resin used to form the adhesive layer 55 contains a polyolefin skeleton, the adhesive layer 55 preferably contains a resin containing a polyolefin skeleton as its main component, more preferably contains acid-modified polyolefin as its main component, and even more preferably contains acid-modified polypropylene as its main component. Here, "main component" means a resin component in the adhesive layer 55 whose content is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more. For example, when the adhesive layer 55 contains acid-modified polypropylene as its main component, it means that the content of acid-modified polypropylene in the resin component of the adhesive layer 55 is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more.

[0152] The presence of a polyolefin backbone in the resin constituting the adhesive layer 55 can be analyzed by methods such as infrared spectroscopy and gas chromatography-mass spectrometry, and the analytical method is not particularly limited. Furthermore, the presence of an acid-modified polyolefin in the resin constituting the adhesive layer 55 can be determined, for example, by measuring maleic anhydride-modified polyolefin using infrared spectroscopy, at a wavenumber of 1760 cm⁻¹. -1 Nearby wave frequency 1780cm -1 A peak originating from maleic anhydride is detected in the vicinity. However, if the degree of acid denaturation is low, the peak may become small and not be detected. In that case, analysis is possible by nuclear magnetic resonance spectroscopy.

[0153] Furthermore, from the viewpoint of ensuring durability such as heat resistance and content resistance of the outer film, and ensuring conformability while keeping the thickness thin, it is more preferable that the adhesive layer 55 is a cured product of a resin composition containing an acid-modified polyolefin and a curing agent. The above-mentioned products are examples of the acid-modified polyolefin.

[0154] Furthermore, the adhesive layer 55 is preferably a cured product of a resin composition comprising an acid-modified polyolefin and at least one selected from the group consisting of compounds having isocyanate groups, compounds having oxazoline groups, and compounds having epoxy groups, and is particularly preferably a cured product of a resin composition comprising an acid-modified polyolefin and at least one selected from the group consisting of compounds having isocyanate groups and compounds having epoxy groups. Furthermore, the adhesive layer 55 preferably contains at least one selected from the group consisting of polyurethane, polyester, and epoxy resin, and more preferably contains polyurethane and epoxy resin. As polyester, for example, ester resins produced by the reaction of epoxy groups and maleic anhydride groups, and amide ester resins produced by the reaction of oxazoline groups and maleic anhydride groups are preferred. If unreacted curing agents such as compounds having isocyanate groups, compounds having oxazoline groups, and epoxy resins remain in the adhesive layer 55, the presence of unreacted substances can be confirmed by methods selected from, for example, infrared spectroscopy, Raman spectroscopy, and time-of-flight secondary ion mass spectrometry (TOF-SIMS).

[0155] Furthermore, from the viewpoint of further improving the adhesion between the barrier layer 52 and the adhesive layer 55, it is preferable that the adhesive layer 55 is a cured product of a resin composition containing a curing agent having at least one selected from the group consisting of oxygen atoms, heterocyclic rings, C=N bonds, and COC bonds. Examples of curing agents having heterocyclic rings include curing agents having oxazoline groups and curing agents having epoxy groups. Examples of curing agents having C=N bonds include curing agents having oxazoline groups and curing agents having isocyanate groups. Examples of curing agents having COC bonds include curing agents having oxazoline groups and curing agents having epoxy groups. The fact that the adhesive layer 55 is a cured product of a resin composition containing these curing agents can be confirmed by methods such as gas chromatography-mass spectrometry (GCMS), infrared spectroscopy (IR), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and X-ray photoelectron spectroscopy (XPS).

[0156] While there are no particular limitations on the compound having an isocyanate group, polyfunctional isocyanate compounds are preferred from the viewpoint of effectively improving the adhesion between the barrier layer 52 and the adhesive layer 55. The polyfunctional isocyanate compound is not particularly limited as long as it is a compound having 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), polymerized or nurated versions thereof, mixtures thereof, and copolymers with other polymers. Adducts, biuretes, and isocyanurates are also examples.

[0157] The content of the compound having an isocyanate group in the adhesive layer 55 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 55. This effectively enhances the adhesion between the barrier layer 52 and the adhesive layer 55.

[0158] Compounds containing an oxazoline group are not particularly limited as long as they have an oxazoline skeleton. Specific examples of compounds containing an oxazoline group include those with a polystyrene main chain and those with an acrylic main chain. Commercially available examples include the Epocross series manufactured by Nippon Shokubai Co., Ltd.

[0159] The proportion of the compound having an oxazoline group in the adhesive layer 55 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 55. This effectively enhances the adhesion between the barrier layer 52 and the adhesive layer 55.

[0160] Examples of compounds having epoxy groups include epoxy resins. The epoxy resin is not particularly limited as long as it is capable of forming a crosslinked structure by the epoxy groups present in the molecule; known epoxy resins can be used. The weight-average molecular weight of the epoxy resin is preferably around 50 to 2000, more preferably around 100 to 1000, and even more preferably around 200 to 800. In this disclosure, the weight-average molecular weight of the epoxy resin is the value measured by gel permeation chromatography (GPC) under conditions using polystyrene as a standard sample.

[0161] Specific examples of epoxy resins include glycidyl ether derivatives of trimethylolpropane, bisphenol A diglycidyl ether, modified bisphenol A diglycidyl ether, bisphenol F type glycidyl ether, novolac glycidyl ether, glycerin polyglycidyl ether, and polyglycerin polyglycidyl ether. Epoxy resins may be used individually or in combination of two or more types.

[0162] The proportion of epoxy resin in the adhesive layer 55 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 55. This effectively enhances the adhesion between the barrier layer 52 and the adhesive layer 55.

[0163] The polyurethane is not particularly limited, and any known polyurethane can be used. The adhesive layer 55 may be, for example, a cured product of a two-component curing type polyurethane.

[0164] The proportion of polyurethane in the adhesive layer 55 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 55. This effectively enhances the adhesion between the barrier layer 52 and the adhesive layer 55 in an atmosphere where components that induce corrosion of the barrier layer, such as electrolytes, are present.

[0165] Furthermore, if the adhesive layer 55 is a cured product of a resin composition containing at least one selected from the group consisting of compounds having isocyanate groups, compounds having oxazoline groups, and epoxy resins, and the acid-modified polyolefin, the acid-modified polyolefin functions as the main agent, and the compounds having isocyanate groups, compounds having oxazoline groups, and compounds having epoxy groups each function as curing agents.

[0166] The adhesive layer 55 may contain a modifier having a carbodiimide group.

[0167] From the viewpoint of more favorably exhibiting the effects of this disclosure, it is preferable that the adhesive layer 55 is formed from a resin composition comprising acid-modified polypropylene and an elastomer, and further comprising at least one of block polypropylene and homopolypropylene. The resin composition may further contain random polypropylene, polyethylene, etc. From the viewpoint of improving adhesion to the barrier layer 52 and heat resistance, it is preferable that the adhesive layer 55 is made of homopolypropylene that has been acid-modified (i.e., acid-modified homopolypropylene).

[0168] From the viewpoint of more favorably exhibiting the effects of this disclosure, in the resin composition forming the adhesive layer 55, the content of acid-modified polypropylene is preferably about 5% by mass or more, more preferably about 10% by mass or more, even more preferably about 15% by mass or more, and also preferably about 90% by mass or less, more preferably about 80% by mass or less, even more preferably about 70% by mass or less. Preferred ranges include about 5-90% by mass, about 5-80% by mass, about 5-70% by mass, about 10-90% by mass, about 10-80% by mass, about 10-70% by mass, about 15-90% by mass, about 15-80% by mass, and about 15-70% by mass.

[0169] From the viewpoint of more favorably exhibiting the effects of this disclosure, in the resin composition forming the adhesive layer 55, the elastomer content is preferably about 25% by mass or more, more preferably about 30% by mass or more, even more preferably about 35% by mass or more, and also preferably about 60% by mass or less, more preferably about 55% by mass or less, even more preferably about 50% by mass or less. Preferred ranges include about 25-60% by mass, about 25-55% by mass, about 25-50% by mass, about 30-60% by mass, about 30-55% by mass, about 30-50% by mass, about 35-60% by mass, about 35-55% by mass, and about 35-50% by mass.

[0170] From the viewpoint of more favorably exhibiting the effects of this disclosure, the elastomer included in the resin composition that forms the adhesive layer 55 is preferably a binary copolymer or a ternary copolymer. Furthermore, the elastomer is preferably a propylene-based elastomer. Examples of propylene-based elastomers include binary copolymers and ternary copolymers. Examples of binary copolymers include propylene-ethylene copolymer elastomers and propylene-butene copolymer elastomers, and examples of ternary copolymers include propylene-ethylene-butene copolymer elastomers and ethylene-propylene-diene copolymer elastomers. Among elastomers, propylene-ethylene copolymer elastomers are preferred as binary copolymers, and propylene-ethylene-butene copolymer elastomers are preferred as ternary copolymers.

[0171] From the viewpoint of more favorably exhibiting the effects of this disclosure, in the resin composition forming the adhesive layer 55, the content of block polypropylene is preferably about 30% by mass or more, more preferably about 35% by mass or more, even more preferably about 40% by mass or more, and also preferably about 95% by mass or less, more preferably about 90% by mass or less, and even more preferably about 85% by mass or less. Preferred ranges include about 30-95% by mass, about 30-90% by mass, about 30-85% by mass, about 35-95% by mass, about 35-90% by mass, about 35-85% by mass, about 40-95% by mass, about 40-90% by mass, and about 40-85% by mass.

[0172] Furthermore, from the viewpoint of exhibiting the effects of this disclosure more favorably, in the resin composition forming the adhesive layer 55, the homopolypropylene content is preferably about 20% by mass or more, more preferably about 25% by mass or more, even more preferably about 30% by mass or more, and also preferably about 80% by mass or less, more preferably about 75% by mass or less, even more preferably about 70% by mass or less. Preferred ranges include about 20-80% by mass, about 20-75% by mass, about 20-70% by mass, about 25-80% by mass, about 25-75% by mass, about 25-70% by mass, about 30-80% by mass, about 30-75% by mass, and about 30-70% by mass.

[0173] From the viewpoint of more favorably exhibiting the effects of this disclosure, in the resin composition forming the adhesive layer 55, the content of random polypropylene is preferably about 0% by mass or more, more preferably about 1% by mass or more, even more preferably about 2% by mass or more, and also preferably about 30% by mass or less, more preferably about 25% by mass or less, and even more preferably about 20% by mass or less. Preferred ranges include about 0-30% by mass, about 0-25% by mass, about 0-20% by mass, about 1-30% by mass, about 1-25% by mass, about 1-20% by mass, about 2-30% by mass, about 2-25% by mass, and about 2-20% by mass.

[0174] From the viewpoint of more favorably exhibiting the effects of this disclosure, the polyethylene content in the resin composition forming the adhesive layer 55 is, for example, about 0% by mass or more, preferably about 1% by mass or more, more preferably about 2% by mass or more, even more preferably about 3% by mass or more, and also preferably about 30% by mass or less, more preferably about 25% by mass or less, even more preferably about 20% by mass or less. Preferred ranges include about 0-30% by mass, about 0-25% by mass, about 0-20% by mass, about 1-30% by mass, about 1-25% by mass, about 1-20% by mass, about 2-30% by mass, about 2-25% by mass, about 2-20% by mass, about 3-30% by mass, about 3-25% by mass, and about 3-20% by mass.

[0175] From the viewpoint of more favorably exhibiting the effects of this disclosure, the specific composition of the resin composition is, for example, an acid-modified polypropylene content of about 5% by mass or more (more preferably about 10% by mass or more, even more preferably about 15% by mass or more, and also preferably about 90% by mass or less, more preferably about 80% by mass or less, even more preferably about 70% by mass or less, with preferred ranges being about 5-90% by mass, about 5-80% by mass, about 5-70% by mass, about 10-90% by mass, about 10-80% by mass, about 10-70% by mass, about 15-90% by mass, about 15-80% by mass, about 15-70% by mass, etc.), and an elastomer content of about 25% by mass or more (more preferably about 30% by mass). The above is more preferably about 35% by mass or more, more preferably about 60% by mass or less, more preferably about 55% by mass or less, and even more preferably about 50% by mass or less, with a preferred range being about 25-60% by mass, about 25-55% by mass, about 25-50% by mass, about 30-60% by mass, about 30-55% by mass, about 30-50% by mass, about 35-60% by mass, about 35-55% by mass, about 35-50% by mass, etc.), and the block polypropylene content is about 30% by mass or more (more preferably about 35% by mass or more, even more preferably about 40% by mass or more, and also preferably about 95% by mass or less, more preferably about 90% by mass or less, and even more preferably about 85% by mass or less).Preferred ranges include approximately 30-95% by mass, 30-90% by mass, 30-85% by mass, 35-95% by mass, 35-90% by mass, 35-85% by mass, 40-95% by mass, 40-90% by mass, and 40-85% by mass), with a homopolypropylene content of approximately 20% by mass or more (more preferably approximately 25% by mass or more, even more preferably approximately 30% by mass or more, and also preferably approximately 80% by mass or less, more preferably approximately 75% by mass). The following is more preferably about 70% by mass or less, and preferred ranges include about 20-80% by mass, about 20-75% by mass, about 20-70% by mass, about 25-80% by mass, about 25-75% by mass, about 25-70% by mass, about 30-80% by mass, about 30-75% by mass, about 30-70% by mass, etc.), and the content of random polypropylene is about 0% by mass or more (more preferably about 1% by mass or more, even more preferably about 2% by mass or more, and also preferably The polyethylene content is approximately 30% by mass or less, more preferably approximately 25% by mass or less, and even more preferably approximately 20% by mass or less. Preferred ranges include approximately 0-30% by mass, approximately 0-25% by mass, approximately 0-20% by mass, approximately 1-30% by mass, approximately 1-25% by mass, approximately 1-20% by mass, approximately 2-30% by mass, approximately 2-25% by mass, and approximately 2-20% by mass), where the polyethylene content is, for example, approximately 0% by mass or more (preferably approximately 1% by mass or more, more preferably approximately 2% by mass or more, and even more Preferably, the amount is about 3% by mass or more, more preferably about 30% by mass or less, more preferably about 25% by mass or less, and even more preferably about 20% by mass or less. Preferred ranges include about 0-30% by mass, about 0-25% by mass, about 0-20% by mass, about 1-30% by mass, about 1-25% by mass, about 1-20% by mass, about 2-30% by mass, about 2-25% by mass, about 2-20% by mass, about 3-30% by mass, about 3-25% by mass, and about 3-20% by mass). The resin composition may also be formed from a resin (excluding additives such as lubricants described later) that includes acid-modified polypropylene and an elastomer, and further preferably includes at least one of block polypropylene and homopolypropylene.

[0176] When manufacturing the exterior film 50 of this disclosure by laminating the adhesive layer 55 with a barrier layer 52, a heat-fusible resin layer 53, etc., a pre-formed resin film may be used as the adhesive layer 55. Alternatively, the heat-fusible resin that forms the adhesive layer 55 may be formed into a film on the surface of the barrier layer 52, the heat-fusible resin layer 53, etc. by extrusion molding or coating, and the adhesive layer 55 may be formed from a resin film.

[0177] The thickness of the adhesive layer 55 is preferably about 50 μm or less, about 40 μm or less, about 30 μm or less, about 20 μm or less, or about 5 μm or less. Alternatively, the thickness of the adhesive layer 55 is preferably about 0.1 μm or more, or about 0.5 μm or more. The range of the thickness of the adhesive layer 55 is preferably about 0.1 to 50 μm, about 0.1 to 40 μm, about 0.1 to 30 μm, about 0.1 to 20 μm, about 0.1 to 5 μm, about 0.5 to 50 μm, about 0.5 to 40 μm, about 0.5 to 30 μm, about 0.5 to 20 μm, or about 0.5 to 5 μm. More specifically, in the case of the adhesive exemplified in adhesive layer 54, or the cured product of acid-modified polyolefin and a curing agent, the thickness is preferably about 1 to 10 μm, more preferably about 1 to 5 μm. Furthermore, if the resin exemplified in the heat-fusible resin layer 53 is used, the thickness is preferably about 2 to 50 μm, and more preferably about 10 to 40 μm. If the adhesive layer 55 is the adhesive exemplified in the adhesive layer 54, or a cured product of a resin composition containing an acid-modified polyolefin and a curing agent, the adhesive layer 55 can be formed, for example, by applying the resin composition and curing it by heating. Also, if the resin exemplified in the heat-fusible resin layer 53 is used, it can be formed, for example, by extrusion molding of the heat-fusible resin layer 53 and the adhesive layer 55.

[0178] [Surface coating layer] The exterior film of this disclosure may optionally include a surface coating layer on top of the barrier layer 52, or on top of the substrate layer 51 (on the side of the substrate layer 51 opposite to the barrier layer 52), for the purpose of improving at least one of the following: aesthetics, electrolyte resistance, scratch resistance, and conformability. The surface coating layer is the outermost layer of the exterior film when the energy storage device is assembled using the exterior film.

[0179] The surface coating layer may be made of resins such as polyvinylidene chloride, polyester, polyamide, epoxy resin, acrylic resin, fluororesin, polyurethane, silicon resin, or phenolic resin, or modified versions of these resins. It may also be a copolymer of these resins, or a modified version of a copolymer. Furthermore, it may be a mixture of these resins. The resin is preferably a curable resin. That is, the surface coating layer is preferably composed of a cured product of a resin composition containing a curable resin.

[0180] When the resin forming the surface coating layer is a curable resin, it may be either a one-component curable resin or a two-component curable resin, but a two-component curable resin is preferred. Examples of two-component curable resins include two-component curable polyurethane, two-component curable polyester, and two-component curable epoxy resin. Among these, two-component curable polyurethane is preferred.

[0181] Examples of two-component curable polyurethanes include polyurethanes comprising a first agent containing a polyol compound and a second agent containing an isocyanate compound. Preferably, two-component curable polyurethanes include those comprising a polyol such as polyester polyol, polyether polyol, and acrylic polyol as the first agent and an aromatic or aliphatic polyisocyanate as the second agent. Examples of polyurethanes include polyurethanes comprising a polyurethane compound obtained by reacting a polyol compound and an isocyanate compound in advance, and an isocyanate compound. Examples of polyurethanes include polyurethanes comprising a polyurethane compound obtained by reacting a polyol compound and an isocyanate compound in advance, and a polyol compound. Examples of polyurethanes include polyurethanes cured by reacting a polyurethane compound obtained by reacting a polyol compound and an isocyanate compound in advance with moisture such as air. As the polyol compound, it is preferable to use a polyester polyol having hydroxyl groups on the side chains in addition to the hydroxyl groups at the ends of the repeating units. Examples of the second agent include aliphatic, alicyclic, aromatic, and aromaticaliphatic isocyanate compounds. Examples of isocyanate compounds include hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), hydrogenated XDI (H6XDI), hydrogenated MDI (H12MDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and naphthalene diisocyanate (NDI). Polyfunctional isocyanate modified compounds derived from one or more of these diisocyanates are also possible. Furthermore, polymers (e.g., trimers) can be used as polyisocyanate compounds. Examples of such polymers include adducts, biuretes, and nurates. Furthermore, aliphatic isocyanate compounds refer to isocyanates that have an aliphatic group and no aromatic ring, alicyclic isocyanate compounds refer to isocyanates that have an alicyclic hydrocarbon group, and aromatic isocyanate compounds refer to isocyanates that have an aromatic ring.The surface coating layer is formed of polyurethane, which provides the outer film with excellent electrolyte resistance.

[0182] The surface coating layer may contain, as necessary, additives such as lubricants, flame retardants, antiblocking agents, antioxidants, light stabilizers, tackifiers, and antistatic agents in at least one of its surface and interior, depending on the functionality to be provided to the surface coating layer and its surface. Examples of additives include fine particles with an average particle size of about 0.5 nm to 5 μm. The average particle size of the additive is the median diameter measured by a laser diffraction / scattering particle size distribution analyzer.

[0183] The additive may be either inorganic or organic. Furthermore, there are no particular restrictions on the shape of the additive; examples include spherical, fibrous, plate-like, amorphous, or flaky forms.

[0184] 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 individually or in combination of two or more. Among these additives, silica, barium sulfate, and titanium oxide are preferred from the viewpoint of dispersion stability and cost. Mica is also preferred from the viewpoint of heat dissipation from the energy storage device. In addition, various surface treatments such as insulation treatment and high-dispersibility treatment may be applied to the surface of the additives.

[0185] The method for forming the surface coating layer is not particularly limited; for example, a method of applying a resin to form the surface coating layer can be used. If additives are to be incorporated into the surface coating layer, a resin mixed with the additives can be applied.

[0186] In this disclosure, from the viewpoint of improving the conformability when wrapping the outer film around the electrode body, it is preferable that a lubricant be present on at least one of the surface and interior of the surface coating layer. The lubricant is not particularly limited, but amide lubricants are preferred. Specific examples of amide 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 stearate amide, N-stearyl oleic acid amide, N-oleyl stearate amide, and N-stearyl erucic acid amide. Specific examples of methylolamides include methylol stearate amide. Specific examples of saturated fatty acid bisamides include methylenebisstearate, ethylenebiscaprate, ethylenebislaurate, ethylenebisstearate, ethylenebishydroxystearate, ethylenebisbehenamide, hexamethylenebisstearate, hexamethylenebisbehenamide, hexamethylenehydroxystearate, N,N'-distearyladipamide, and N,N'-distearylsebacinamide. Specific examples of unsaturated fatty acid bisamides include ethylenebisoleamide, ethylenebiserucamide, hexamethylenebisoleamide, N,N'-dioleyladipamide, and N,N'-dioleylsebacinamide. Specific examples of fatty acid ester amides include stearamidoethylstearate. Specific examples of aromatic bisamides include m-xylylenebisstearamide, m-xylylenebishydroxystearamide, and N,N'-distearyl isophthalamide.The lubricant may be used alone or in combination of two or more types, and it is preferable to use a combination of two or more types.

[0187] If a lubricant is present on the surface of the surface coating layer, there are no particular restrictions on its amount, but for example, it may be about 3 mg / m². 2 Preferably about 4 mg / m² 2 More than about 5mg / m 2 The above points are given. In addition, the amount of lubricant present on the surface of the surface coating layer is, for example, approximately 15 mg / m². 2 Preferably about 14 mg / m² 2 Below, about 10mg / m 2 The following are examples. Furthermore, a preferred range for the amount of lubricant present on the surface of the surface coating layer is 3 to 15 mg / m². 2 degree, 3~14mg / m 2 degree, 3~10mg / m 2 degree, 4~15mg / m 2 degree, 4~14mg / m 2 degree, 4~10mg / m 2 degree, 5~15mg / m 2 degree, 5~14mg / m 2 degree, 5~10mg / m 2 The degree can be described as follows.

[0188] The lubricant present on the surface of the surface coating layer may be a lubricant contained in the resin constituting the surface coating layer that has seeped out, or a lubricant applied to the surface of the surface coating layer.

[0189] The thickness of the surface coating layer is not particularly limited as long as it performs the above-mentioned functions as a surface coating layer, and examples include about 0.5 to 10 μm, preferably about 1 to 5 μm.

[0190] <2-3. Method for manufacturing the outer packaging film> The method for manufacturing the exterior film is not particularly limited, as long as a laminate is obtained by laminating each layer of the exterior film of this disclosure, and at a minimum, a method comprising the step of laminating a barrier layer 52 and a heat-sealable resin layer 53 is provided.

[0191] An example of a manufacturing method for the exterior film of this disclosure is as follows. First, a laminate (hereinafter sometimes referred to as "laminated laminate A") is formed by sequentially laminating a base layer 51, an adhesive layer 54, and a barrier layer 52. Specifically, laminate A can be formed by a dry lamination method in which an adhesive used to form the adhesive layer 54 is applied to the base layer 51 or, if necessary, a barrier layer 52 whose surface has been chemically treated, using a coating method such as gravure coating or roll coating, and after drying, the barrier layer 52 or base layer 51 is laminated and the adhesive layer 54 is cured.

[0192] Next, a heat-fusible resin layer 53 is laminated onto the barrier layer 52 of the laminate A. When the heat-fusible resin layer 53 is directly laminated onto the barrier layer 52, the heat-fusible resin layer 53 can be laminated onto the barrier layer 52 of the laminate A by methods such as thermal lamination or extrusion lamination. Also, when an adhesive layer 55 is provided between the barrier layer 52 and the heat-fusible resin layer 53, the adhesive layer 55 and the heat-fusible resin layer 53 can be laminated by methods such as (1) extrusion lamination, (2) thermal lamination, (3) sandwich lamination, or (4) dry lamination. (1) Examples of extrusion lamination methods include laminating the adhesive layer 55 and the heat-fusible resin layer 53 by extrusion onto the barrier layer 52 of the laminate A (co-extrusion lamination, tandem lamination). Furthermore, (2) as a thermal lamination method, for example, a laminate is formed by separately laminating an adhesive layer 55 and a heat-fusible resin layer 53, and this is laminated onto the barrier layer 52 of laminate A, or a laminate is formed by laminating an adhesive layer 55 on the barrier layer 52 of laminate A, and this is laminated with the heat-fusible resin layer 53. Furthermore, (3) as a sandwich lamination method, for example, a molten adhesive layer 55 is poured between the barrier layer 52 of laminate A and a heat-fusible resin layer 53 that has been previously made into a sheet, thereby bonding laminate A and the heat-fusible resin layer 53 via the adhesive layer 55. Furthermore, (4) as a dry lamination method, for example, an adhesive for forming the adhesive layer 55 is solution-coated onto the barrier layer 52 of laminate A and dried, or further laminated by baking, and the heat-fusible resin layer 53 that has been previously made into a sheet is laminated onto this adhesive layer 55.

[0193] When a surface coating layer is provided, the surface coating layer is laminated on the surface of the base layer 51 opposite to the barrier layer 52. The surface coating layer can be formed, for example, by applying the resin used to form the surface coating layer to the surface of the base layer 51. The order of the steps of laminating the barrier layer 52 onto the surface of the base layer 51 and laminating the surface coating layer onto the surface of the base layer 51 is not particularly limited. For example, the surface coating layer may be formed on the surface of the base layer 51 first, and then the barrier layer 52 may be formed on the surface of the base layer 51 opposite to the surface coating layer.

[0194] As described above, a laminate is formed comprising, in this order, a surface coating layer provided as needed, a base material layer 51 provided as needed, an adhesive layer 54 provided as needed, a barrier layer 52, an adhesive layer 55 provided as needed, and a heat-fusible resin layer 53. In order to strengthen the adhesion of the adhesive layer 54 and the adhesive layer 55, which are provided as needed, the laminate may be subjected to further heat treatment.

[0195] In the exterior film, each layer constituting the laminate may be subjected to surface activation treatments such as corona treatment, blast treatment, oxidation treatment, or ozone treatment as needed to improve its processability. For example, by applying corona treatment to the surface of the base layer 51 opposite to the barrier layer 52, the printability of ink on the surface of the base layer 51 can be improved.

[0196] <3-1. Laminated structure and physical properties of exterior materials for energy storage devices> The exterior material 50 for energy storage devices of this disclosure corresponds to the exterior film 50 described above, and each layer is also common to both. That is, in the laminate constituting the exterior material 50 for energy storage devices of this disclosure, the base layer 1, adhesive layer 2, barrier layer 3, adhesive layer 5, heat-fusible resin layer 4, and surface coating layer 6 correspond to the base layer 51, adhesive layer 54, barrier layer 52, adhesive layer 55, heat-fusible resin layer 53, and surface coating layer of the laminate constituting the exterior film 50 described above, respectively.

[0197] The exterior material 50 for energy storage devices of this disclosure, like the exterior film 50, is composed of a laminate comprising a barrier layer 3 and a heat-sealable resin layer 4, as shown in Figure 5, for example. In the exterior material 50 for energy storage devices, the barrier layer 3 is the outermost layer, and the heat-sealable resin layer 4 is the innermost layer. For example, as shown in Figures 10 and 11, when assembling an energy storage device using the exterior material 50 for energy storage devices and energy storage device elements (electrode body 20, electrode terminals 30, etc.), the electrode body 20 is housed in a space formed by heat-sealing the ends of the heat-sealable resin layers 4 of the exterior material 50 for energy storage devices together with the lid 60, with the layers facing each other. In the laminate constituting the exterior material 50 for energy storage devices of this disclosure, with respect to the barrier layer 3, the side of the heat-sealable resin layer 4 on the barrier layer 3 side is inward, and the opposite side is outward.

[0198] The exterior material 50 for the energy storage device may, for example, have a base layer 1 outside the barrier layer 3, as needed, as shown in Figures 5 to 8. The exterior material 50 for the energy storage device may also have an adhesive layer 2 between the base layer 1 and the barrier layer 3, as needed, for purposes such as improving the adhesion between these layers, as shown in Figures 6 to 8. Furthermore, an adhesive layer 5 may be provided between the barrier layer 3 and the heat-fusible resin layer 4, as needed, for purposes such as improving the adhesion between these layers, as shown in Figures 7 and 8. Additionally, as shown in Figure 8, a surface coating layer 6 or the like may be provided on the outside of the base layer 1 (opposite the heat-fusible resin layer 4 side), as needed.

[0199] The thickness of the laminate constituting the exterior material 50 for the energy storage device is not particularly limited, but from the viewpoint of cost reduction and improvement of energy density, for example, it can be about 250 μm or less, preferably about 190 μm or less, 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 exterior material for the energy storage device, which is to protect the electrode body 20, the thickness of the laminate constituting the exterior material 50 for the energy storage device can be 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 outer casing material 50 for energy storage devices include, for example, approximately 35-250 μm, 35-190 μm, 35-180 μm, 35-155 μm, 35-120 μm, 45-250 μm, 45-190 μm, 45-180 μm, 45-155 μm, 45-120 μm, 60-250 μm, 60-190 μm, 60-180 μm, 60-155 μm, and 60-120 μm. In particular, approximately 60-155 μm is preferred when making the energy storage device a lightweight thin film, and approximately 155-190 μm is preferred when improving conformability.

[0200] In the exterior material 50 for energy storage devices, the ratio of the total thickness of the optional base layer 1, optional adhesive layer 2, barrier layer 3, optional adhesive layer 5, heat-fusible resin layer 4, and optional surface coating layer 6 to the thickness (total thickness) of the laminate constituting the exterior material 50 for energy storage devices is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. Specifically, if the exterior material 50 for energy storage devices of this disclosure includes a base layer 1, an adhesive layer 2, a barrier layer 3, an adhesive layer 5, and a heat-fusible resin layer 4, the ratio of the total thickness of each of these layers to the thickness (total thickness) of the laminate constituting the exterior material 50 for energy storage devices is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. Furthermore, even if the exterior material 50 for energy storage devices of this disclosure is a laminate comprising a base layer 1, an adhesive layer 2, a barrier layer 3, and a heat-fusible resin layer 4, the ratio of the total thickness of these layers to the thickness (total thickness) of the laminate constituting the exterior material 50 for energy storage devices can be, for example, 80% or more, preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more.

[0201] From the viewpoint of more favorably demonstrating the effects of the present invention, the Young's modulus of the exterior material 50 for the energy storage device is preferably 6000 MPa or more, more preferably 8000 MPa or more, even more preferably 10000 MPa or more, and also preferably 40000 MPa or less, more preferably 35000 MPa or less, even more preferably 30000 MPa or less. Preferred ranges include approximately 6000 to 40000 MPa, approximately 6000 to 35000 MPa, approximately 6000 to 30000 MPa, approximately 8000 to 40000 MPa, approximately 8000 to 35000 MPa, approximately 8000 to 30000 MPa, approximately 10000 to 40000 MPa, approximately 10000 to 35000 MPa, and approximately 10000 to 30000 MPa. In this disclosure, the Young's modulus of the exterior material for the energy storage device is a value measured by the following method.

[0202] <Measurement of Young's modulus of exterior materials for energy storage devices> In accordance with the provisions of JIS K6251:2017, the SS curve in the TD direction of the adhesive film was obtained under the following measurement conditions, and the Young's modulus (MPa) was calculated from the maximum value of the slope of the SS curve. (Measurement conditions) A tensile testing machine is used. Specimen shape: Dumbbell No. 7 Specimen width: 2 mm Length of test specimen: 35 mm Thickness of the test specimen: Measured with a thickness gauge. Distance between gauge lines: 20mm Tensile speed: 50 mm / min Test environment: 23±5℃, 50±30%RH Number of measurements: Average of 3 measurements

[0203] As explained for the exterior film 50, an effective way to increase the Young's modulus of the exterior material 50 for energy storage devices is to increase the Young's modulus of the barrier layer 3.

[0204] <3-2. Each layer that makes up the exterior material for energy storage devices> As described above, in the laminate constituting the exterior material 50 for energy storage devices of this disclosure, the base layer 1, adhesive layer 2, barrier layer 3, adhesive layer 5, heat-fusible resin layer 4, and surface coating layer 6 correspond, respectively, to the base layer 51, adhesive layer 54, barrier layer 52, adhesive layer 55, heat-fusible resin layer 53, and surface coating layer of the laminate constituting the exterior film 50 described above. Therefore, the descriptions of the base layer 1, adhesive layer 2, barrier layer 3, adhesive layer 5, heat-fusible resin layer 4, and surface coating layer 6 are the same as the descriptions of the base layer 51, adhesive layer 54, barrier layer 52, adhesive layer 55, heat-fusible resin layer 53, and surface coating layer of the laminate constituting the exterior film 50 described above, and redundant descriptions are omitted.

[0205] In the exterior material for energy storage devices of the present disclosure, the barrier layer 3 of the exterior material 50 for energy storage devices is characterized in that the ratio of the area average crystal grain size R1 (μm) to the area average crystal grain size R2 (μm) (R1 / R2) is 55% or more.

[0206] Here, the area-average grain size R1 (μm) of the barrier layer 3 is the area-average grain size (μm) obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer 3 perpendicular to the rolling direction of the barrier layer 3 and perpendicular to the surface of the barrier layer 3 at a position where the heat-fusible resin layer 4 of the exterior material 50 for the energy storage device and the polypropylene plate are heat-fusible under the condition that the thickness of the heat-fusible resin layer is 20% to 80%. The polypropylene plate is assumed to be a lid that constitutes the exterior body. Furthermore, the condition that the thickness of the heat-fusible resin layer is 20% to 80% can be adjusted, for example, by setting the heat-fusible temperature to about 160 to 240°C, the surface pressure to about 0.2 to 1.5 MPa, and the heat-fusible time to about 1 to 12 seconds.

[0207] Furthermore, the area-average grain size R2 (μm) of the barrier layer 3 is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer 3 perpendicular to the surface of the barrier layer 3 in a direction perpendicular to the rolling direction of the barrier layer 3, at a position where the heat-fusible resin layer 4 of the exterior material 50 for the energy storage device is not heat-fussed to the polypropylene plate.

[0208] From the viewpoint of more favorably exhibiting the effects of the invention disclosed herein, the ratio (R1 / R2) is preferably about 55% or more, more preferably about 60% or more, even more preferably about 70% or more, and also preferably about 150% or less, more preferably about 140% or less, even more preferably about 130% or less. Preferred ranges include about 55-150%, about 55-140%, about 55-130%, about 60-150%, about 60-140%, about 60-130%, about 70-150%, about 70-140%, and about 70-130%.

[0209] The area-average crystal grain size R1 (μm) and area-average crystal grain size R2 (μm) of the barrier layer 3 are values ​​measured by the following method. When obtaining the exterior material for energy storage devices from energy storage devices (for example, obtaining the exterior material for energy storage devices from energy storage devices installed in vehicles that have been driven) and measuring the area-average crystal grain size R1 (μm) and area-average crystal grain size R2 (μm) of the barrier layer 3, a sample should be taken from the part of the energy storage device exterior material where the heat-sealable resin layer has not been heat-sealed, and the following measurement should be performed.

[0210] <Measurement of area-average crystal grain size R1 and R2 of the barrier layer> For the energy storage device, the barrier layer at the location where the heat-sealable resin layer of the energy storage device's exterior material and a polypropylene plate (assuming a lid) are heat-sealed under the condition that the thickness of the heat-sealable resin layer is between 20% and 80%, and the barrier layer at the location where the heat-sealable resin layer of the energy storage device's exterior material is not heat-sealed (non-sealed area) are obtained. The heat-sealing condition is set so that the ratio of "(thickness of the heat-sealable resin layer at the location where the heat-sealable resin layer is heat-sealed to the lid) / (thickness of the heat-sealable resin layer at the location where the heat-sealable resin layer is not heat-sealed to the lid)" is between 20% and 80%. Specifically, the energy storage device's exterior material is cut into a rectangular shape with dimensions of MD360mm x TD160mm. On the other hand, a rectangular polypropylene lid (polypropylene plate) with dimensions of 100mm length x 30mm width x 5mm thickness is prepared as the lid for the exterior body. Furthermore, a rectangular aluminum block (140 mm long x 98 mm wide x 28 mm thick) is prepared as a simulated electrode. Next, as shown in the schematic diagram in Figure 1, lids are placed on both sides of the electrode in the longitudinal direction, and this is wrapped with an outer casing material for energy storage devices. The positions where the heat-sealable resin layers of the outer casing material for energy storage devices face each other (first sealing portion 70) and the positions where the heat-sealable resin layer of the outer casing material for energy storage devices contacts the lids (second sealing portion 80) are heat-sealed using a heat-sealing bar to obtain a simulated energy storage device. Note that the simulated energy storage device does not have electrode terminals as shown in Figure 1. The sealing width at the positions where the heat-sealable resin layers of the outer casing material for energy storage devices face each other (first sealing portion 70) is 10 mm. Furthermore, the seal width at the point where the heat-fusible resin layer of the exterior material for the energy storage device contacts the lid (second sealing portion 80) shall be the thickness of the lid (10 mm). The thermal sealing conditions (temperature, surface pressure, time) of the second sealing portion 80 shall be such that the thickness of the heat-fusible resin layer is between 20% and 80%, respectively. Next, the barrier layer of the obtained simulated energy storage device shall be subjected to crystallographic analysis by EBSD to measure the area-average crystal grain sizes R1 and R2 of the barrier layer. The specific measurement method is as follows.

[0211] Crystallographic analysis of the cross-section of each barrier layer perpendicular to the rolling direction is performed using the EBSD method to measure the area-average grain size of the barrier layer. The details of the measurement conditions are as follows. The area-average grain size is the diameter when the area calculated by [(measurement area - area with CI value of 0.1 or less) / number of crystals] is assumed to be a circle. Multiple images obtained by crystallographic analysis using the EBSD method are stitched together to form an area of ​​approximately 5000 μm. 2 The above represents the area-average grain size of crystals included in the measurement area. The maximum grain size is the value measured for the largest crystal among those included in the measurement area, assuming a circular crystal shape. The standard deviation of grain size is calculated by removing areas with a CI value of 0.1 or less, and then concatenating multiple images obtained by crystal analysis using the EBSD method, resulting in a standard deviation of approximately 5000 μm. 2 The area-average grain size R2 of the barrier layer is calculated from the distribution of crystal grain size (diameter when the crystal area is assumed to be a circle) of the crystals contained within the measurement area (the entire thickness direction of the barrier layer is defined as the measurement area). The area-average grain size R2 of the barrier layer is measured at a point 3 cm away from the measurement point of the area-average grain size R1.

[0212] (Measuring device) A Schottky field emission scanning electron microscope equipped with an EBSD detector is used.

[0213] (Pre-processing) As a pretreatment, the barrier layer is cut perpendicular to the rolling direction (RD) to obtain a cross-section. The rolling direction of the barrier layer is determined by observing the glossy surface of the barrier layer with a metallurgical microscope and determining the direction in which linear rolling marks extend. Specifically, the procedure is as follows: First, the barrier layer to be used as a sample is cut out with a trimming razor to a size of 5 mm (perpendicular to the rolling direction) x 10 mm (in the rolling direction), and then embedded in resin. Next, using a trimming razor, the barrier layer is cut together with the resin perpendicular to the surface of the barrier layer, perpendicular to the rolling direction of the barrier layer, to expose the cross-section of the barrier layer. Next, the obtained cross-section is trimmed using a microtome. In this trimming, in order to reduce mechanical distortion of the cross-sectional shape, the microtome is used to cut approximately 1 mm perpendicular to the cross-section together with the embedded resin. Next, using an ion milling apparatus, a broad argon beam is irradiated perpendicular to the cross-section under the conditions of a projection width of 50 μm, a voltage of 6 kV, and 4 hours to prepare the measurement cross-section. This is a process of precisely exposing the cross-section of the barrier layer in order to minimize mechanical damage to the crystal structure that occurs in the previous process. In this disclosure, the "perpendicular direction" when cutting the aluminum alloy foil is confirmed under a stereomicroscope and may contain an error of about 10°. Specifically, the direction perpendicular to the rolling direction is allowed to be 80 to 100° in the rolling direction, and the direction perpendicular to the surface is allowed to be 80 to 100° relative to the surface.

[0214] (SEM conditions) The scanning electron microscope (SEM) settings used in the EBSD method are as follows: Magnification: 2000x (Standard magnification for photography is Polaroid 545) Acceleration voltage: 15kV Working distance: 15mm Sample tilt angle: 70°

[0215] (EBSD conditions) The conditions for crystal analysis using the EBSD method are as follows: Step size: 150nm Analysis conditions: The following analysis will be performed using the crystal orientation analysis software OIM (Ver. 7.3) manufactured by TSL Solutions Co., Ltd. Multiple images are stitched together, and the measurement area is approximately 5000 μm. 2 This concludes the explanation. Regarding the upper limit of the measurement area, for example, approximately 30,000 μm. 2 The following applies: The measurement area will be defined as extending from the center of the barrier layer in the thickness direction to both ends, and areas where resin is attached to the cross-section or where an acid-resistant coating is present will be excluded from the measurement area. The CI value should be 0.1 or higher, the grain boundary condition should be 0.5 degrees or higher, and the minimum grain size should be 3 steps or higher. After stitching the images together, check the pole diagram. If the center of the pole figure is shifted by more than 10°, rotate the crystal data to correct the symmetry. The reference pole figure used in this case is measured from the sample surface using XRD. When obtaining the pole figure from the surface using EBSD, perform mechanical polishing, plane milling, or electropolishing of the sample surface to eliminate the influence of the mechanical crystal structure of the sample surface, and then perform wide-area measurements. After that, rotate the pole figure obtained from the surface direction by 90° so that it matches the pole figure obtained from the same orientation as the pole figure obtained from the cross-section of the target sample. Use this pole figure as a reference. Data with a Confidence Index (CI) of 0.1 or less, as defined by TSL Solutions Co., Ltd.'s crystal orientation analysis software OIM (Ver. 7.3), will be excluded from the analysis. This eliminates data based on pretreatment resins present on both the front and back surfaces of the sample, grain boundaries in the cross-section, and amorphous materials.

[0216] The area-average grain size R1 (μm) and area-average grain size R2 (μm) of the barrier layer 3 can be adjusted, respectively, by the material constituting the barrier layer 3, the thickness of the barrier layer 3, etc.

[0217] For example, by increasing the Young's modulus of the barrier layer 3 (i.e., increasing the Young's modulus of the exterior material 50 for the energy storage device), the ratio of the area-average crystal grain size R1 (μm) to the area-average crystal grain size R2 (μm) of the barrier layer 3 (R1 / R2) can be increased. The preferred Young's modulus of the barrier layer 3 will be discussed later. For example, increasing the thickness of the barrier layer 3 or using a high-strength metal are effective methods.

[0218] Furthermore, if, for example, the barrier layer 3 is formed from aluminum alloy foil, and the aluminum alloy composition is in the 8000 series according to JIS standards, the strength can be increased by adding a small amount of Si to the aluminum base metal. Also, if the aluminum alloy composition is in the 5000 series according to JIS standards, the strength of the soft foil can be increased by solid solution strengthening by solid solution strengthening by solid solution dissolving Mg in the aluminum.

[0219] Refining the crystal grains of the metal forming barrier layer 3 is also effective in increasing the aforementioned ratio (R1 / R2). For example, in the case of aluminum alloy compositions of the 8000 and 5000 series according to JIS standards, Al-Fe intermetallic compounds crystallize during casting, and these act as nuclei for refining the crystal grains. Furthermore, when different peripheral speed rolling (a method of rolling with rolls of different peripheral speeds) is employed, the rolled material undergoes shear deformation over the entire thickness of the plate in addition to normal rolling deformation. As a result, crystal rotation is promoted, and the change from subgrain boundaries to large-angle grain boundaries is accelerated, generating fine crystal grains. This method is also effective in cold working, but it is more effective in hot working. In addition, increasing the number of rolling passes in hot rolling of aluminum alloy foil and increasing the final cold rolling ratio are also effective. The higher the final cold rolling ratio from after intermediate annealing to the final thickness (for example, 80% or more), the greater the amount of strain accumulated in the aluminum alloy foil, and the finer the recrystallized grains after final annealing.

[0220] Regarding the rolling conditions of aluminum foil, conditions such as the rolling ratio, heating temperature, and heating time are adjusted. For example, a process of homogenizing an aluminum metal or aluminum alloy ingot at about 500 to 600 °C for about 1 to 2 hours, a hot rolling process, a cold rolling process, an intermediate annealing process of holding at about 300 to 450 °C for about 1 to 10 hours, a cold rolling process carried out with a rolling ratio of 80% or more, more preferably 90% or more, from after the intermediate annealing to the final rolling, and a final annealing process of holding at about 250 to 400 °C for about 30 to 100 hours are included. However, the conditions for refining crystal grains are not limited to this.

[0221] <3-3. Manufacturing Method of Exterior Material for Power Storage Device> As described above, since the exterior material 50 for a power storage device of the present disclosure corresponds to the exterior film 50, the manufacturing method thereof is also common, and thus the description is omitted.

[0222] <3-4. Use of Exterior Material for Power Storage Device> The exterior material for a power storage device of the present disclosure is used for a package for sealing and housing power storage device elements such as a positive electrode, a negative electrode, and an electrolyte. That is, a power storage device element including at least a positive electrode, a negative electrode, and an electrolyte can be housed in a package formed by the exterior material for a power storage device of the present disclosure to form a power storage device. In other words, a power storage device can be formed by wrapping a power storage device element with the exterior material for a power storage device of the present disclosure.

[0223] For example, a power storage device element including at least a positive electrode, a negative electrode, and an electrolyte is coated with the exterior material for a power storage device of the present disclosure in a state where metal terminals connected to each of the positive electrode and the negative electrode protrude outward, such that a flange portion (a region where heat-sealable resin layers contact each other) can be formed at the periphery of the power storage device element, and the heat-sealable resin layers of the flange portion are heat-sealed and sealed, thereby providing a power storage device using the exterior material for a power storage device. When accommodating a power storage device element in a package formed by the exterior material for a power storage device of the present disclosure, the package is formed such that the heat-sealable resin portion of the exterior material for a power storage device of the present disclosure is on the inner side (the surface contacting the power storage device element). The heat-sealable resin layers of two exterior materials for a power storage device may be opposed and overlapped, and the peripheral portion of the overlapped exterior materials for a power storage device may be heat-sealed to form a package. Also, as in the example shown in FIG. 9, one exterior material for a power storage device may be folded back and overlapped, and the peripheral portion may be heat-sealed to form a package. When folding back and overlapping, as in the example shown in FIG. 9, the sides other than the folded-back side may be heat-sealed to form a package by three-side sealing, or it may be folded back to form a flange portion and four-side sealed. When the innermost layer and the outermost layer of the exterior material for a power storage device are heat-sealable resin layers, the package may be formed by heat-sealing the heat-sealable resin layer of the innermost layer and the heat-sealable resin layer of the outermost layer. Also, in addition to the mode in which the surfaces of the exterior material for a power storage device facing each other are heat-sealed, a mode in which the outer surface and the inner surface of the exterior material for a power storage device are heat-sealed is also preferable.

[0224] Further, a recess for accommodating a power storage device element may be formed in the exterior material for a power storage device by deep drawing or bulging. As in the example shown in FIG. 9, one of the exterior materials for a power storage device may be provided with a recess, and the other exterior material for a power storage device may not be provided with a recess, or the other exterior material for a power storage device may also be provided with a recess.

[0225] The exterior material for energy storage devices of this disclosure is used in an energy storage device that utilizes an exterior material for energy storage devices that encloses an electrode body and a lid, and when the energy storage device is repeatedly exposed to high and low temperature changes, cracks are suppressed in the sealing portion of the exterior material for energy storage devices with the lid. Therefore, the energy storage device element may be sealed by the lid in addition to the exterior material for energy storage devices. That is, the exterior material for energy storage devices and the lid constitute an exterior that seals the energy storage device element (an exterior for energy storage devices). For example, the energy storage device element may be housed inside a cylindrical exterior material for energy storage devices, and the opening may be closed with a lid. In another example, the energy storage device element, connected to a lid, may be housed inside a cylindrical exterior material for energy storage devices that has an opening, and the opening may be closed with a lid. The lid and the exterior material for energy storage devices are preferably joined by any means. In order to improve the volumetric energy density of the energy storage device, it is preferable that the energy storage device exterior material be wrapped around the energy storage device element and the cover in order to reduce the dead space between the energy storage device element and the energy storage device exterior material. When wrapping the energy storage device exterior material around the energy storage device element and the cover, one piece of energy storage device exterior material may be wrapped around, or multiple pieces of energy storage device exterior material may be wrapped around.

[0226] As described above, the lid can be formed from, for example, a resin molded product, a metal molded product, an exterior material for an energy storage device, or a combination thereof. In this disclosure, when the lid is described as a resin molded product, it does not include embodiments in which the lid is composed solely of a film as defined by the JIS (Japanese Industrial Standards) [Packaging Terminology] standard. When the lid is a metal molded product, the metal terminals can be omitted because the lid also functions as a metal terminal. The lid may be composed of a resin material and a conductive material.

[0227] The following describes in detail the case where the energy storage device comprises an electrode body and an outer casing that seals the electrode body, and the outer casing has an outer casing material for energy storage devices of the present disclosure that encloses the electrode body and a lid that seals the electrode body together with the outer casing material for energy storage devices.

[0228] Similar to Figure 1, Figure 10 is a schematic perspective view of the energy storage device 10. Figure 11 is a cross-sectional view along line AA in Figure 1. In Figures 10 to 12, the z-direction (z1 and z2 directions) of the arrows indicates the thickness direction of the energy storage device 10, the x-direction (x1 and x2 directions) of the arrows indicates the width direction of the energy storage device 10, and the y-direction (y1 and y2 directions) of the arrows indicates the depth direction of the energy storage device 10. The directions indicated by the x, y, and z arrows are the same in all subsequent figures.

[0229] As described above, the energy storage device 10 comprises an electrode body 20, electrode terminals 30, and an outer casing 40. The electrode body 20 includes, for example, electrodes (positive and negative electrodes) that constitute an energy storage component such as a lithium-ion battery, capacitor, all-solid-state battery, semi-solid-state battery, pseudo-solid-state battery, polymer battery, all-resin battery, lead-acid battery, nickel-metal hydride battery, nickel-cadmium battery, nickel-iron battery, nickel-zinc battery, silver oxide-zinc battery, metal-air battery, polyvalent cation battery, or capacitor, as well as a separator, etc. In this disclosure, the shape of the electrode body 20 is, for example, a substantially rectangular parallelepiped. Note that "substantially rectangular parallelepiped" includes not only a perfect rectangular parallelepiped but also a solid that can be considered a rectangular parallelepiped by, for example, modifying the shape of a part of its outer surface. The shape of the electrode body 20 may be, for example, a cylinder or a polygonal prism.

[0230] Similar to Figures 1 and 2, the energy storage device 10 in Figures 10 and 11 is equipped with two electrode terminals 30. The electrode terminals 30 are metal terminals used for inputting and outputting power to the electrode body 20. One end of the electrode terminal 30 is electrically connected to an electrode (positive or negative electrode) included in the electrode body 20. The other end of the electrode terminal 30 protrudes outward from, for example, the edge of the outer casing 40. Note that the electrode terminals 30 only need to be able to input and output power to the electrode body 20, and do not need to protrude from, for example, the outer casing 40. If the cover 60, which will be described later, is made of, for example, a conductive material, the cover 60 may also function as an electrode terminal 30, and in this case, the cover 60 that functions as an electrode terminal may or may not protrude from the outer casing 40.

[0231] As described above, the metal material constituting the electrode terminal 30 is, for example, aluminum, nickel, or copper. For example, if the electrode body 20 is a lithium-ion battery, the electrode terminal 30 connected to the positive electrode is usually made of aluminum, and the electrode terminal 30 connected to the negative electrode is usually made of copper, nickel, or the like. The outermost layer of the electrode body 20 does not necessarily have to be an electrode; for example, it may be a protective tape or a separator. The outer shape of the electrode body 20 is, for example, a rectangular parallelepiped.

[0232] As described above, the casing 40 seals the electrode body 20. The casing 40 comprises an outer casing material 50 for the energy storage device and a cover 60. The outer casing material 50 for the energy storage device encloses the electrode body 20. As in Figures 1 and 2, in Figures 10 and 11, the outer casing material 50 for the energy storage device is wrapped around the electrode body 20. The cover 60 is positioned to the side of the electrode body 20 in the y-direction. In another example, the electrode body 20 may be housed inside the outer casing material 50 for the energy storage device, which is configured in a cylindrical shape with openings at both ends in the y-direction, and the openings may be closed by the cover 60. In yet another example, the electrode body 20 may be housed inside the outer casing material 50 for the energy storage device, which is configured in a cylindrical shape with openings, while connected to the cover 60, and the openings may be closed by the cover 60.

[0233] As described above, the exterior body 40 has a pair of main surfaces and a pair of side surfaces formed from the exterior material 50 for the energy storage device. As in Figures 1 and 2, the pair of main surfaces are substantially the same size in Figures 10 and 11. The pair of side surfaces are also substantially the same size. Each of the pair of main surfaces has a larger area than the pair of side surfaces. The pair of covers 60 are positioned to the sides of the electrode body 20 so as to close the pair of openings. In this disclosure, the main surfaces and side surfaces are the surfaces of the exterior body 40 excluding the covers 60.

[0234] As mentioned above, for example, there is a method of forming a housing portion (recess) for housing the electrode body 20 in the outer material 50 for the energy storage device by cold forming. However, it is not always easy to form a deep housing portion by such a method. If one attempts to form a deep housing portion (recess) (for example, a molding depth of 15 mm) by cold forming, pinholes or cracks may occur in the outer material 50 for the energy storage device, which is likely to lead to a decrease in battery performance. On the other hand, the outer material 40 seals the electrode body 20 by wrapping the outer material 50 for the energy storage device around the electrode body 20, so the electrode body 20 can be easily sealed regardless of the thickness of the electrode body 20. Furthermore, in order to reduce the dead space between the electrode body 20 and the outer material 50 for the energy storage device in order to improve the volumetric energy density of the energy storage device 10, it is preferable that the outer material 50 for the energy storage device is wrapped so that it is in contact with the outer surface of the electrode body 20. Furthermore, in all-solid-state batteries, it is necessary to apply high pressure uniformly from the outside of the battery in order to achieve optimal battery performance. Therefore, it is preferable that the outer casing material 50 for the energy storage device is wrapped around the outer surface of the electrode body 20 so that it is in contact with the outer surface of the electrode body 20.

[0235] The exterior material 50 for the energy storage device is a laminate (laminate film) having at least a barrier layer 3 and a heat-sealable resin layer 4. Details of each layer included in the exterior material 50 for the energy storage device are as described above.

[0236] As described above, the lid 60 may be any shape, such as a cylinder, prism, rectangular parallelepiped, or cube, and may be composed of, for example, a resin material. Here, "composed of a resin material" means that when the total mass of the materials constituting the lid 60 is considered to be 100% by mass, the resin material content is 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. In other words, the materials constituting the lid 60 may contain materials other than resin materials in addition to resin materials.

[0237] In the lid 60, specific examples of resin are as described above.

[0238] Furthermore, as stated above, the resin material may contain fillers as needed. Specific examples of fillers are as described above.

[0239] As described above, the melt mass flow rate (measurement temperature 230°C) of the resin material contained in the material constituting the lid 60 is preferably in the range of 1 g / 10 min to 100 g / 10 min, preferably in the range of 1 g / 10 min to 80 g / 10 min, preferably in the range of 1 g / 10 min to 60 g / 10 min, preferably in the range of 5 g / 10 min to 100 g / 10 min, preferably in the range of 5 g / 10 min to 80 g / 10 min, and more preferably in the range of 5 g / 10 min to 60 g / 10 min. The melt mass flow rate is measured in accordance with JIS K7210-1:2014.

[0240] As described above, the lid 60 may be made up of a conductive material. "Made up of a conductive material" means that when the total mass of the materials constituting the lid 60 is considered to be 100% by mass, the content of the conductive material is 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. In other words, the materials constituting the lid 60 may contain materials other than conductive materials in addition to conductive materials.

[0241] As described above, the conductive material constituting the cover 60 is, for example, a metallic material. The metallic material constituting the cover 60 is, for example, aluminum, aluminum alloy, nickel, copper, or copper alloy. For example, if the electrode body 20 is a lithium-ion battery, the cover 60 connected to the positive electrode is preferably made of aluminum or an aluminum alloy. The cover 60 connected to the negative electrode is preferably made of nickel, copper, or a copper alloy. The material constituting the cover 60 connected to the negative electrode may be copper with nickel plating. The material constituting the cover 60 may also include recycled metallic material. If the cover 60 is made of a conductive material, the cover 60 also functions as an electrode terminal 30, so the energy storage device 10 can omit the electrode terminal 30.

[0242] As described above, the lid 60 may be configured such that at least a part of the lid body 61 is covered by the covering 62. In the lid 60 of Figure 12, the periphery of the lid body 61 (the periphery of the thickness portion) is covered by the covering 62. The lid 60 may be joined to the heat-fusible resin layer 4 of the exterior material 50 for the energy storage device via the covering 62. It is preferable that the covering 62 is made up of a resin material. The lid 60 has a lid body 61 and a covering 62 that joins the lid body 61 to the exterior material 50 for the energy storage device, and the covering 62 may be made up of resin (resin material). The definition of "made up of a resin material" for the covering 62 is the same as for the lid 60.

[0243] As described above, if the lid 60 is made of a conductive material, the lid body 61 may be made of a conductive material, and at least a portion of the lid body 61 may be covered by the covering 62.

[0244] As described above, when the lid body 60 is made of a conductive material, the lid body 60 may be joined to the exterior material 50 for the power storage device via an adhesive film instead of the coating. The adhesive film can be arbitrarily selected as long as it can adhere the exterior material 50 for the power storage device and the lid body 60. The adhesive film is preferably a laminated film having at least a heat-sealable resin layer, a heat-resistant base material layer, and a heat-sealable resin layer in this order. The specifications regarding the heat-sealable resin layer of the adhesive film can be applied to the specifications regarding the heat-sealable resin layer 4. The materials constituting the heat-sealable resin layers on both sides of the adhesive film may be the same kind of material or different kinds of materials, and are appropriately selected according to the material constituting the heat-sealable resin layer 4 of the exterior material 50 for the power storage device and the material constituting the lid body 60. The material constituting the heat-sealable resin layer on the side of the adhesive film that is adhered to the lid body 60 is preferably an acid-modified polyolefin-based resin graft-modified with an acid such as maleic anhydride. The heat-sealable resin layer on the side of the adhesive film that is adhered to the exterior material 50 for the power storage device preferably uses the same kind of material as the material constituting the heat-sealable resin layer 4 of the exterior material 50 for the power storage device.

[0245] As described above, the heat-resistant base material layer may be a film made of a heat-resistant resin. For example, unstretched or stretched films such as polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polymethylpentene (registered trademark), polyacetal cyclic polyolefin, polyethylene, and polypropylene can be used. Polyethylene terephthalate is inexpensive and has high strength, and is particularly preferable.

[0246] As described above, it is preferable that the adhesive film has adhesive properties. When forming the second sealing portion 80, which will be described later, with the adhesive film positioned between the exterior material 50 for the energy storage device and the lid 60, the position of the adhesive film relative to the lid 60 and the exterior material 50 for the energy storage device is less likely to shift. Adhesion can be imparted to the adhesive film by including an adhesive-imparting resin in the heat-fusible resin layer of the adhesive film. Examples of adhesive-imparting resins include amorphous polyolefins. Examples of amorphous polyolefins include amorphous polypropylene, or copolymers of amorphous propylene and other α-olefins. The content of the adhesive-imparting resin relative to the base material constituting the heat-fusible resin is preferably 10 to 20% by weight or less.

[0247] As described above, the lid 60 has a first main surface located on the inside of the energy storage device (electrode body 20 side), a second main surface located on the outside of the energy storage device, and four sides which are heat-sealed to the heat-sealable resin layer 4 of the exterior material 50 for the energy storage device. The first main surface faces the electrode body 20. The second main surface is the surface opposite to the first main surface.

[0248] As described above, when the lid 60 is cylindrical, prismatic, rectangular parallelepiped, or cube, it is preferable that the lid 60 has a certain thickness in the thickness direction (y direction) so as to suppress deformation of the outer casing 40 even when the energy storage devices 10 are stacked on top of each other. From another viewpoint, when the lid 60 is cylindrical, prismatic, rectangular parallelepiped, or cube, it is preferable that the lid 60 has a certain thickness in the thickness direction (y direction) so as to allow the lid joint of the lid 60 and the outer casing film 50 to be suitably joined when forming the second sealing portion 80. The minimum value of the thickness of the lid 60 in the thickness direction (y direction) (distance in the y direction between the first main surface and the second main surface) is, for example, 1.0 mm, more preferably 3.0 mm, and even more preferably 4.0 mm. The maximum thickness of the lid 60 in the y-direction is, for example, 20 mm, preferably 15.0 mm, more preferably 10.0 mm, even more preferably 8.0 mm, and even more preferably 7.0 mm. The maximum thickness of the lid 60 in the y-direction may be 10 mm or more. The preferred range of thickness for the material constituting the lid 60 is 1.0 mm to 20.0 mm, 1.0 mm to 15.0 mm, 1.0 mm to 10.0 mm, 1.0 mm to 8.0 mm, 1.0 mm to 7.0 mm, 3.0 mm to 20.0 mm, 3.0 mm to 15.0 mm, 3.0 mm to 10.0 mm, 3.0 mm to 8.0 mm, 3.0 mm to 7.0 mm, 4.0 mm to 20.0 mm, 4.0 mm to 15.0 mm, 4.0 mm to 10.0 mm, 4.0 mm to 8.0 mm, and 4.0 mm to 7.0 mm. In this disclosure, when the lid 60 is described as a cylinder, prism, rectangular parallelepiped, or cube, etc., it does not include the form in which the lid 60 is composed solely of film as defined by the JIS (Japanese Industrial Standards) [Packaging Terminology] standard. The thickness of the lid 60 may vary depending on the part of the lid 60. If the thickness of the lid 60 varies depending on the part, the thickness of the lid 60 is the thickness of the thickest part.

[0249] Similar to Figures 1 and 2, in Figures 10 and 11, the cover 60 has a through-hole into which the electrode terminal 30 is inserted. The through-hole penetrates the first main surface and the second main surface of the cover. With the electrode body 20 housed inside, the electrode terminal 30 protrudes to the outside of the outer casing 40 through the through-hole formed in the cover 60. The small gap between the through-hole in the cover 60 and the electrode terminal 30 is filled with, for example, resin. In the energy storage device 10, the position in which the electrode terminal 30 protrudes to the outside can be arbitrarily selected. For example, the electrode terminal 30 may protrude to the outside from a hole formed on any of the six surfaces of the outer casing 40. In this case, the small gap between the outer casing 40 and the electrode terminal 30 is filled with, for example, resin. The electrode terminal 30 may protrude from between the cover 60 and the outer casing material 50 for the energy storage device, or it may protrude from the first sealing portion 70, which will be described later. In the energy storage device 10, the cover 60 and the electrode terminals 30 are provided as separate components, but the cover 60 and the electrode terminals 30 may be integrally formed. Furthermore, if the electrode terminals 30 do not protrude from the edge of the outer casing 40, the cover 60 does not need to have through holes.

[0250] Similar to Figures 1 and 2, in Figures 10 and 11, the outer casing material 50 for the energy storage device is wrapped around the electrode body 20, and the first sealing portion 70 is formed by heat sealing the opposing surfaces (heat-fusible resin layers 4) of the outer casing material 50 for the energy storage device.

[0251] As described above, the first sealing portion 70 is formed by heat sealing the heat-sealable resin layers of the exterior material 50 for the energy storage device. The first sealing portion 70 extends in the longitudinal direction of the exterior body 40. The position in which the first sealing portion 70 is formed on the exterior body 40 can be arbitrarily selected. As with Figure 1, and as shown in Figure 10, it is preferable that the base of the first sealing portion 70 is located on the edge of the boundary between the main surface and the side surface of the exterior body 40. The base of the first sealing portion 70 may also be located on any surface of the exterior body 40. As with Figure 1, in Figure 10, the first sealing portion 70 protrudes outward from the electrode body 20 in a plan view. The first sealing portion 70 may be folded toward the side surface of the exterior body 40, for example, or folded toward the main surface.

[0252] As described above, the second sealing portion 80 is formed by joining the heat-fusible resin layer 4 of the energy storage device exterior material 50 and the lid joint portion of the lid 60 (the portion where the heat-fusible resin layer 4 of the energy storage device exterior material 50 and the lid 60 come into contact), for example, by heat sealing. The energy storage device exterior material 50 and the lid 60 can be joined by any method, such as welding.

[0253] The casing material for energy storage devices disclosed herein can be suitably used in energy storage devices such as batteries (including capacitors, capacitors, etc.). Furthermore, the casing material for energy storage devices disclosed herein can be used in either primary batteries or secondary batteries, but is preferably used in secondary batteries. The types of secondary batteries to which the casing material for energy storage devices disclosed herein can be applied are not particularly limited, and examples include lithium-ion batteries, lithium-ion polymer batteries, all-solid-state batteries, semi-solid-state batteries, pseudo-solid-state batteries, polymer batteries, all-resin batteries, lead-acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, silver oxide-zinc batteries, metal-air batteries, polyvalent cation batteries, capacitors, capacitors, etc. Among these secondary batteries, lithium-ion batteries and lithium-ion polymer batteries are particularly suitable applications for the casing material for energy storage devices disclosed herein. [Examples]

[0254] The present disclosure will be described in detail below with reference to examples and comparative examples. However, the present disclosure is not limited to the examples.

[0255] <Manufacturing method for outer packaging film> Comparative Example 1A As the base layer, a laminate was prepared by bonding a biaxially oriented polyethylene terephthalate (PET) film (12 μm thick) and an oriented nylon (ONy) film (15 μm thick) with an adhesive layer (formed with a two-component curing urethane adhesive, with a curing thickness of 3 μm). In addition, aluminum foil (JIS H4160:1994 A8079H-O (40 μm thick)) was prepared as the barrier layer. Both sides of the aluminum foil were treated with a chemical conversion solution. The chemical conversion solution for the aluminum foil consisted of a phenolic resin, a chromium fluoride compound, and phosphoric acid, with a chromium coating amount of 10 mg / m². 2 This was achieved by applying the coating to both sides of the aluminum foil using the roll-coating method and then baking it to achieve the desired (dry mass).

[0256] Next, using a two-component curing urethane adhesive, the substrate layer and the barrier layer were bonded together with an adhesive layer (3 μm thick) by a dry lamination method, and a laminate was fabricated in which the substrate layer / adhesive layer / barrier layer were stacked in that order.

[0257] Next, maleic anhydride-modified polypropylene, which forms an adhesive layer (40 μm thick), and random polypropylene, which forms a heat-fusible resin layer (40 μm thick), were co-extruded onto the barrier layer of each laminate obtained above, thereby laminating the adhesive layer / heat-fusible resin layer on top of the barrier layer. Next, the obtained laminate was aged and heated to obtain an exterior film consisting of a laminate in which the base layer / adhesive layer / barrier layer / adhesive layer / heat-fusible resin layer were laminated in this order.

[0258] Comparative example 2A Except for using aluminum foil (JIS H4160:1994 A8079H-O (60 μm thick)) as the barrier layer, an outer film was obtained in the same manner as in Comparative Example 1A, consisting of a laminate in which a base layer / adhesive layer / barrier layer / adhesive layer / heat-fusible resin layer were laminated in this order.

[0259] Example 1A Except for using aluminum foil (JIS H4160:1994 A8079H-O (thickness 80 μm)) as the barrier layer, an outer film was obtained in the same manner as in Comparative Example 1A, consisting of a laminate in which a base layer / adhesive layer / barrier layer / adhesive layer / heat-fusible resin layer were laminated in this order.

[0260] Example 2A Except for using stainless steel foil (JIS G4303 SUS304 (60 μm thick)) as the barrier layer, an outer film was obtained in the same manner as in Comparative Example 1A, consisting of a laminate in which a base layer / adhesive layer / barrier layer / adhesive layer / heat-fusible resin layer were laminated in this order.

[0261] Example 3A The same outer film as in Comparative Example 1A was used. In the thermal shock test described later, the material of the lid of the outer casing used for the simulated energy storage device is different from that of Comparative Example 1A.

[0262] Example 4A The same outer film used in Comparative Example 1A was used. In the thermal shock test described later, the material of the lid of the outer casing used for the simulated energy storage device differs from that of Comparative Example 1A and Example 3A.

[0263] <Measurement of area-average crystal grain size R1 and R2 of the barrier layer> A simulated energy storage device was manufactured in the same manner as the simulated energy storage device manufactured in the <thermal shock test> described later. Next, for the simulated energy storage device, the barrier layer at the location where the heat-sealable resin layer of the outer film is heat-sealed to the lid (sealed area (second sealing area)) and the barrier layer at the location where the heat-sealable resin layer of the outer film is not heat-sealed (non-sealed area) were obtained, and crystal analysis was performed on each using the EBSD method to measure the area-average crystal grain size R1 and R2 of the barrier layer. The specific measurement method is as follows.

[0264] Crystallographic analysis was performed on the cross-section of each barrier layer perpendicular to the rolling direction using the EBSD method, and the area-average grain size of the barrier layer was measured. The details of the measurement conditions are as follows. The measurement results are shown in Table 1A. The area-average grain size is the diameter when the area calculated by [(measurement area - area with CI value of 0.1 or less) / number of crystals] is assumed to be a circle, and multiple images obtained by crystallographic analysis using the EBSD method are stitched together to form an area of ​​approximately 5000 μm. 2 The above is the area-average grain size of the crystals included in the measurement area. The grain size is calculated assuming a circular crystal shape and is measured for the crystals within the measurement area. The standard deviation of the grain size is calculated by removing areas with a CI value of 0.1 or less, and then concatenating multiple images obtained by crystal analysis using the EBSD method, resulting in a standard deviation of approximately 5000 μm. 2 The average crystal grain size R2 of the barrier layer was calculated from the distribution of crystal grain size (diameter when the crystal area is assumed to be a circle) within the measurement area (the entire thickness direction of the barrier layer). The average crystal grain size R2 of the barrier layer was measured at a location 3 cm away from the measurement location of the average crystal grain size R1.

[0265] (Measuring device) A Schottky field emission scanning electron microscope equipped with an EBSD detector (manufactured by TSL Solutions Co., Ltd.) was used.

[0266] (Pre-processing) As a pretreatment, the barrier layer is cut perpendicular to the rolling direction (RD) to obtain a cross-section. The rolling direction of the barrier layer is determined by observing the glossy surface of the barrier layer with a metallurgical microscope and determining the direction in which linear rolling marks extend. Specifically, the procedure is as follows: First, the barrier layer to be used as a sample is cut out with a trimming razor to a size of 5 mm (perpendicular to the rolling direction) x 10 mm (in the rolling direction), and then embedded in resin. Next, using a trimming razor, the barrier layer is cut together with the resin perpendicular to the rolling direction and perpendicular to the surface of the barrier layer, exposing the cross-section of the barrier layer. Then, the obtained cross-section is trimmed using a microtome (ultramicrotome manufactured by Leica Microsystems). In this trimming, in order to reduce mechanical distortion of the cross-sectional shape, the microtome is used to cut approximately 1 mm perpendicular to the cross-section together with the embedded resin. Next, using an ion milling apparatus (manufactured by Hitachi High-Technologies Corporation), a broad argon beam was irradiated perpendicularly to the cross-section under the conditions of a projection width of 50 μm, a voltage of 6 kV, and a duration of 4 hours to prepare the measurement cross-section. This is a process to precisely expose the cross-section of the barrier layer in order to minimize damage to the mechanical crystal structure that occurred in the previous process. In this disclosure, the "perpendicular direction" when cutting the aluminum alloy foil is confirmed under a stereomicroscope and may contain an error of about 10°. Specifically, the direction perpendicular to the rolling direction is considered to be within an acceptable range of 80 to 100° in the rolling direction, and the direction perpendicular to the surface is considered to be within an acceptable range of 80 to 100° relative to the surface.

[0267] (SEM conditions) The scanning electron microscope (SEM) settings used in the EBSD method are as follows: Magnification: 2000x (Standard magnification for photography is Polaroid 545) Acceleration voltage: 15kV Working distance: 15mm Sample tilt angle: 70°

[0268] (EBSD conditions) The conditions for crystal analysis using the EBSD method are as follows: Step size: 150nm Analysis conditions: The following analysis was performed using the crystal orientation analysis software OIM (Ver. 7.3) manufactured by TSL Solutions Co., Ltd. Multiple images are stitched together, and the measurement area is approximately 5000 μm. 2 The above was concluded. In this case, the measurement area was defined as the area from the center in the thickness direction of the barrier layer to both ends, and areas where resin was attached to the cross-section or where an acid-resistant coating was present were excluded from the measurement area. The CI value was set to 0.1 or higher, the grain boundary condition to 0.5 degrees or higher, and the minimum grain size to 3 steps or higher. After stitching the images together, I checked the pole diagram. If the center of the pole figure is shifted by more than 10°, rotate the crystal data to correct the symmetry. The reference pole figure used in this case is measured from the sample surface using XRD. When obtaining the pole figure from the surface using EBSD, perform mechanical polishing, plane milling, or electropolishing of the sample surface to eliminate the influence of the mechanical crystal structure of the sample surface, and then perform wide-area measurements. After that, rotate the pole figure obtained from the surface direction by 90° so that it matches the pole figure obtained from the same orientation as the pole figure obtained from the cross-section of the target sample. Use this pole figure as a reference. Data with a Confidence Index (CI) value of 0.1 or less, as defined by TSL Solutions Co., Ltd.'s crystal orientation analysis software OIM (Ver. 7.3), were excluded from the analysis. This eliminates data based on pretreatment resins present on both the front and back surfaces of the sample, grain boundaries in the cross-section, and amorphous materials.

[0269] <Measurement of Young's modulus of exterior film> The Young's modulus of the outer film was measured using the following method. The results are shown in Table 1A. In accordance with the provisions of JIS K6251:2017, the SS curve in the TD direction of the outer film was obtained under the following measurement conditions, and the Young's modulus (MPa) was calculated from the maximum value of the slope of the SS curve. (Measurement conditions) A tensile testing machine (Shimadzu Autograph AG-X Plus) will be used. Specimen shape: Dumbbell No. 7 Specimen width: 2 mm Length of test specimen: 35 mm Thickness of the test specimen: Measured with a thickness gauge. Distance between gauge lines: 20mm Tensile speed: 50 mm / min Test environment: 23±5℃, 50±30%RH Number of measurements: Average of 3 measurements

[0270] <Cold and thermal shock test> The outer packaging films produced in each example and comparative example were cut into rectangular shapes with dimensions of MD360mm x TD160mm. Meanwhile, as lids for the outer packaging, comparative examples 1A-2A and examples 1A-2A prepared lids made of polypropylene in the shape of a rectangular parallelepiped (length 100mm x width 30mm x thickness 5mm). Example 3A prepared a lid (length 100mm x width 30mm x thickness 5mm) in which the perimeter (around the thickness portion) of a rectangular parallelepiped (length 98mm x width 28mm x thickness 5mm) aluminum lid body was covered with a polypropylene (PP) coating. Example 4A prepared a lid (length 100mm x width 30mm x thickness 5mm) in which the perimeter (around the thickness portion) of a rectangular parallelepiped (length 98mm x width 28mm x thickness 5mm) aluminum lid body was covered with a maleic anhydride-modified polypropylene (PPa) coating. Furthermore, a rectangular aluminum block (140mm long x 98mm wide x 28mm thick) was prepared as a simulated electrode.

[0271] Next, as shown in the schematic diagram in Figure 1, lids were placed on both sides of the electrode body in the longitudinal direction, and this was wrapped with an outer film. The positions where the heat-sealable resin layers of the outer film face each other (first sealing portion 70) and the positions where the heat-sealable resin layers of the outer film and the lids come into contact (second sealing portion 80) were heat-sealed using a heat-sealing bar to obtain a simulated energy storage device. Note that the simulated energy storage device does not have electrode terminals as shown in Figure 1. The sealing width at the positions where the heat-sealable resin layers of the outer film face each other (first sealing portion 70) was set to 10 mm. The sealing width at the positions where the heat-sealable resin layers of the outer film and the lids come into contact (second sealing portion 80) was set to the thickness of the lids (5 mm). Furthermore, the heat sealing conditions (temperature, surface pressure, and time) for the second sealing portion 80 were set as follows: Comparative Example 1A was 180°C, 0.60 MPa, and 3 seconds; Comparative Examples 2A and Examples 1A-3A were 180°C, 1.20 MPa, and 5 seconds, respectively; and Example 4A was 180°C, 0.60 MPa, and 7 seconds. In all cases, the conditions were set so that the ratio of "(thickness of the heat-fusible resin layer at the location where the heat-fusible resin layer is heat-fused to the lid) / (thickness of the heat-fusible resin layer at the location where the heat-fusible resin layer is not heat-fused to the lid)" was 20-80%. Note that the conditions under which the thickness of the heat-fusible resin layer is between 20% and 80% can be adjusted, for example, by setting the heat-fussing temperature to approximately 160-240°C, the surface pressure to approximately 0.2-1.5 MPa, and the heat-fussing time to approximately 1-12 seconds.

[0272] For each of the obtained simulated energy storage devices, a thermal shock test was conducted by leaving them undisturbed in a -30°C environment for 30 minutes, followed by leaving them undisturbed in an 80°C environment for 30 minutes, with this cycle repeated 800 times. The test evaluated whether cracking in the sealing portion of the outer film with the lid (the surface layer of the outer film) was suppressed when the energy storage device was repeatedly exposed to high and low temperature changes. The results are shown in Table 1A.

[0273] In the thermal shock test results shown in Table 1A, cracks occurred in the sealing portion of the outer film between the lid and the energy storage device of Comparative Examples 1A-2A. On the other hand, while fine cracks occurred in the sealing portion of the outer film between the lid and the energy storage device of Example 1A, it can be evaluated that the occurrence of cracks in the sealing portion of the outer film between the lid and the energy storage device was suppressed. In the energy storage devices of Examples 2A-4A, no cracks occurred in the sealing portion of the outer film between the lid and the energy storage device, and it can be evaluated that the occurrence of cracks in the sealing portion of the outer film between the lid and the energy storage device was suppressed particularly well. Fine cracks are defined as cracks that do not reveal voids in the barrier layer when the sealing portion is observed with an SEM, whereas the cracks observed in Comparative Examples 1A-2A were cracks that revealed voids in the barrier layer when the sealing portion was observed with an SEM. The SEM observation conditions were: observation magnification: 1000x, acceleration voltage: 5kV, working distance: 10mm.

[0274] [Table 1A]

[0275] In Table 1A, PET represents polyethylene terephthalate film, DL represents an adhesive layer formed by the dry lamination method, ONy represents stretched nylon film, AL represents aluminum alloy foil, SUS represents stainless steel foil, PPa represents a maleic anhydride-modified polypropylene layer, and PP represents a polypropylene layer. Furthermore, the values ​​of Young's modulus, area-average grain size R1, R2, and R1 / R2 are calculated by rounding the measured values ​​listed in Table 1A to one order of magnitude smaller.

[0276] <Manufacturing of exterior materials for energy storage devices> Comparative example 1B As the base layer, a laminate was prepared by bonding a biaxially oriented polyethylene terephthalate (PET) film (12 μm thick) and an oriented nylon (ONy) film (15 μm thick) with an adhesive layer (formed with a two-component curing urethane adhesive, with a curing thickness of 3 μm). In addition, aluminum foil (JIS H4160:1994 A8079H-O (60 μm thick)) was prepared as the barrier layer. Both sides of the aluminum foil were treated with a chemical conversion treatment. The chemical conversion treatment of the aluminum foil consisted of a treatment solution made of phenolic resin, chromium fluoride compound, and phosphoric acid, with a chromium coating amount of 10 mg / m². 2 This was achieved by applying the coating to both sides of the aluminum foil using the roll-coating method and then baking it to achieve the desired (dry mass).

[0277] Next, using a two-component curing urethane adhesive, the substrate layer and the barrier layer were bonded together with an adhesive layer (3 μm thick) by a dry lamination method, and a laminate was fabricated in which the substrate layer / adhesive layer / barrier layer were stacked in that order.

[0278] Next, maleic anhydride-modified polypropylene, which forms an adhesive layer (40 μm thick), and random polypropylene, which forms a heat-fusible resin layer (40 μm thick), were co-extruded onto the barrier layer of each laminate obtained above, thereby laminating the adhesive layer / heat-fusible resin layer on top of the barrier layer. Next, the obtained laminate was aged and heated to obtain an exterior material for an energy storage device consisting of a laminate in which the base layer / adhesive layer / barrier layer / adhesive layer / heat-fusible resin layer are laminated in this order.

[0279] Example 1B Except for using aluminum foil (JIS H4160:1994 A8079H-O (thickness 80 μm)) as the barrier layer, an exterior material for an energy storage device was obtained in the same manner as in Comparative Example 1B, consisting of a laminate in which a base layer / adhesive layer / barrier layer / adhesive layer / heat-fusible resin layer were laminated in this order.

[0280] Example 2B Except for using stainless steel foil (JIS G4303 SUS304 (thickness 60 μm)) as the barrier layer, an exterior material for an energy storage device was obtained in the same manner as in Comparative Example 1B, consisting of a laminate in which a base layer / adhesive layer / barrier layer / adhesive layer / heat-fusible resin layer were laminated in this order.

[0281] <Measurement of area-average crystal grain size R1 and R2 of the barrier layer> A simulated energy storage device was manufactured in the same manner as the simulated energy storage device manufactured in the <thermal shock test> described later. Next, for the simulated energy storage device, the barrier layer at the location where the heat-fusible resin layer of the energy storage device's exterior material is heat-fusible to the polypropylene plate (polypropylene lid) (sealed area (second sealing area)) and the barrier layer at the location where the heat-fusible resin layer of the energy storage device's exterior material is not heat-fusible (non-sealed area) were obtained, and crystal analysis was performed on each using the EBSD method to measure the area-average crystal grain size R1 and R2 of the barrier layer. The specific measurement method is as follows.

[0282] Crystallographic analysis was performed on the cross-section of each barrier layer perpendicular to the rolling direction using the EBSD method, and the area-average grain size of the barrier layer was measured. The details of the measurement conditions are as follows. The measurement results are shown in Table 1B. The area-average grain size is the diameter when the area calculated by [(measurement area - area with CI value of 0.1 or less) / number of crystals] is assumed to be a circle, and is calculated by stitching together multiple images obtained by crystallographic analysis using the EBSD method to obtain a diameter of approximately 5000 μm. 2 The above represents the area-average grain size of crystals included in the measurement area. The maximum grain size is the value measured for the largest crystal among those included in the measurement area, assuming a circular crystal shape. The standard deviation of grain size is calculated by removing areas with a CI value of 0.1 or less, and then concatenating multiple images obtained by crystal analysis using the EBSD method, resulting in a standard deviation of approximately 5000 μm. 2 The grain size (diameter when the crystal area is assumed to be a circle) of the crystals included in the measurement area was used to calculate the grain size.

[0283] (Measuring device) A Schottky field emission scanning electron microscope equipped with an EBSD detector (manufactured by TSL Solutions Co., Ltd.) was used.

[0284] (Pre-processing) As a pretreatment, the barrier layer is cut perpendicular to the rolling direction (RD) to obtain a cross-section. The rolling direction of the barrier layer is determined by observing the glossy surface of the barrier layer with a metallurgical microscope and determining the direction in which linear rolling marks extend. Specifically, the procedure is as follows: First, the barrier layer to be used as a sample is cut out with a trimming razor to a size of 5 mm (perpendicular to the rolling direction) x 10 mm (in the rolling direction), and then embedded in resin. Next, using a trimming razor, the barrier layer is cut together with the resin perpendicular to the rolling direction and perpendicular to the surface of the barrier layer, exposing the cross-section of the barrier layer. Then, the obtained cross-section is trimmed using a microtome (ultramicrotome manufactured by Leica Microsystems). In this trimming, in order to reduce mechanical distortion of the cross-sectional shape, the microtome is used to cut approximately 1 mm perpendicular to the cross-section together with the embedded resin. Next, using an ion milling apparatus (manufactured by Hitachi High-Technologies Corporation), a broad argon beam was irradiated perpendicularly to the cross-section under the conditions of a projection width of 50 μm, a voltage of 6 kV, and a duration of 4 hours to prepare the measurement cross-section. This is a process to precisely expose the cross-section of the barrier layer in order to minimize damage to the mechanical crystal structure that occurred in the previous process. In this disclosure, the "perpendicular direction" when cutting the aluminum alloy foil is confirmed under a stereomicroscope and may contain an error of about 10°. Specifically, the direction perpendicular to the rolling direction is considered to be within an acceptable range of 80 to 100° in the rolling direction, and the direction perpendicular to the surface is considered to be within an acceptable range of 80 to 100° relative to the surface.

[0285] (SEM conditions) The scanning electron microscope (SEM) settings used in the EBSD method are as follows: Magnification: 2000x (Standard magnification for photography is Polaroid 545) Acceleration voltage: 15kV Working distance: 15mm Sample tilt angle: 70°

[0286] (EBSD conditions) The conditions for crystal analysis using the EBSD method are as follows: Step size: 150nm Analysis conditions: The following analysis was performed using the crystal orientation analysis software OIM (Ver. 7.3) manufactured by TSL Solutions Co., Ltd. Multiple images are stitched together, and the measurement area is approximately 5000 μm. 2 The above was concluded. In this case, the measurement area was defined as the area from the center in the thickness direction of the barrier layer to both ends, and areas where resin was attached to the cross-section or where an acid-resistant coating was present were excluded from the measurement area. The CI value was set to 0.1 or higher, the grain boundary condition to 0.5 degrees or higher, and the minimum grain size to 3 steps or higher. After stitching the images together, I checked the pole diagram. If the center of the pole figure is shifted by more than 10°, rotate the crystal data to correct the symmetry. The reference pole figure used in this case is measured from the sample surface using XRD. When obtaining the pole figure from the surface using EBSD, perform mechanical polishing, plane milling, or electropolishing of the sample surface to eliminate the influence of the mechanical crystal structure of the sample surface, and then perform wide-area measurements. After that, rotate the pole figure obtained from the surface direction by 90° so that it matches the pole figure obtained from the same orientation as the pole figure obtained from the cross-section of the target sample. Use this pole figure as a reference. Data with a Confidence Index (CI) value of 0.1 or less, as defined by TSL Solutions Co., Ltd.'s crystal orientation analysis software OIM (Ver. 7.3), were excluded from the analysis. This eliminates data based on pretreatment resins present on both the front and back surfaces of the sample, grain boundaries in the cross-section, and amorphous materials.

[0287] <Measurement of Young's modulus of exterior materials for energy storage devices> The Young's modulus of the exterior material for energy storage devices was measured using the following method. The results are shown in Table 1B. In accordance with the provisions of JIS K6251:2017, the SS curve in the TD direction of the adhesive film was obtained under the following measurement conditions, and the Young's modulus (MPa) was calculated from the maximum value of the slope of the SS curve. (Measurement conditions) A tensile testing machine (Shimadzu Autograph AG-X Plus) will be used. Specimen shape: Dumbbell No. 7 Specimen width: 2 mm Length of test specimen: 35 mm Thickness of the test specimen: Measured with a thickness gauge. Distance between gauge lines: 20mm Tensile speed: 50 mm / min Test environment: 23±5℃, 50±30%RH Number of measurements: Average of 3 measurements

[0288] <Cold and thermal shock test> The exterior materials for the energy storage devices manufactured in each example and comparative example were cut into rectangular shapes with dimensions of MD360mm x TD160mm. A rectangular polypropylene lid (polypropylene plate) measuring 100mm in length, 30mm in width, and 5mm in thickness was prepared as the lid for the exterior. Furthermore, a rectangular aluminum block measuring 140mm in length, 98mm in width, and 28mm in thickness was prepared as a simulated electrode.

[0289] Next, as shown in the schematic diagram of Figure 1, covers were placed on both sides of the electrode body in the longitudinal direction, and this was wrapped with an outer casing material for energy storage devices. The positions where the heat-fusible resin layers of the outer casing material for energy storage devices face each other (first sealing portion 70) and the positions where the heat-fusible resin layers of the outer casing material for energy storage devices and the covers come into contact (second sealing portion 80) were heat-sealed using a heat sealing bar to obtain a simulated energy storage device. Note that the simulated energy storage device does not have electrode terminals as shown in Figure 1. The seal width at the positions where the heat-fusible resin layers of the outer casing material for energy storage devices face each other (first sealing portion 70) was set to 10 mm. The seal width at the positions where the heat-fusible resin layers of the outer casing material for energy storage devices and the covers come into contact (second sealing portion 80) was set to the thickness of the covers (5 mm). Furthermore, the heat sealing conditions (temperature, surface pressure, and time) for the second sealing section 80 were set to 180°C, 1.20 MPa, and 5 seconds, respectively. These heat sealing conditions were set so that the ratio of "(thickness of the heat-fusible resin layer at the location where the heat-fusible resin layer is heat-fused to the lid) / (thickness of the heat-fusible resin layer at the location where the heat-fusible resin layer is not heat-fused to the lid)" was between 20% and 80%.

[0290] For each of the obtained simulated energy storage devices, a thermal shock test was conducted by leaving them undisturbed in a -30°C environment for 30 minutes, followed by leaving them undisturbed in an 80°C environment for 30 minutes, with this cycle being repeated 800 times. The test evaluated whether cracking in the sealing portion between the energy storage device's outer casing and the lid (the surface layer of the energy storage device's outer casing) was suppressed when the energy storage device was repeatedly exposed to high and low temperature changes. The results are shown in Table 1B.

[0291] In the thermal shock test results shown in Table 1B, the energy storage device of Comparative Example 1B showed cracks in the sealing portion between the energy storage device's exterior material and the lid. On the other hand, the energy storage device of Example 1B showed fine cracks in the sealing portion between the energy storage device's exterior material and the lid, but it can be evaluated that the occurrence of cracks in the sealing portion between the energy storage device's exterior material and the lid was suppressed. The energy storage device of Example 2B showed no cracks in the sealing portion between the energy storage device's exterior material and the lid, and it can be evaluated that the occurrence of cracks in the sealing portion between the energy storage device's exterior material and the lid was suppressed particularly well. Fine cracks are cracks in which no voids are observed in the barrier layer when the sealing portion is observed with an SEM, whereas the cracks observed in Comparative Example 1B were cracks in which voids were observed in the barrier layer when the sealing portion was observed with an SEM. The SEM observation conditions were: observation magnification: 1000x, acceleration voltage: 5kV, working distance: 10mm.

[0292] [Table 1B]

[0293] In Table 1B, PET represents polyethylene terephthalate film, DL represents an adhesive layer formed by the dry lamination method, ONy represents stretched nylon film, AL represents aluminum alloy foil, SUS represents stainless steel foil, PPa represents a maleic anhydride-modified polypropylene layer, and PP represents a polypropylene layer. Furthermore, the values ​​of Young's modulus, area-average grain size R1, R2, and R1 / R2 are calculated by rounding the measured values ​​to one order of magnitude smaller than the values ​​listed in Table 1B.

[0294] As described above, this disclosure provides inventions in the following embodiments. Item 1A. Energy storage device, Electrode body and The electrode body is enclosed by an outer casing, The exterior body is, The outer film enclosing the electrode body, It has a lid that seals the electrode body together with the outer film, The exterior film is composed of a laminate comprising at least a barrier layer and a heat-sealable resin layer. The barrier layer has a ratio (R1 / R2) of area-average crystal grain size R1 (μm) to area-average crystal grain size R2 (μm) of 55% or more. The area-average grain size R1 (μm) is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicular to the surface of the barrier layer, in a direction perpendicular to the rolling direction of the barrier layer, at the position where the heat-sealable resin layer of the outer film is heat-sealed to the lid. The area-average grain size R2 (μm) is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicular to the surface of the barrier layer, in a direction perpendicular to the rolling direction of the barrier layer, at a position where the heat-fusible resin layer of the outer film is not heat-fussed. Energy storage device. Item 2A. The energy storage device according to Item 1A, wherein the barrier layer is formed of stainless steel, steel sheet, or aluminum alloy. Item 3A. The lid comprises a lid body and a covering that joins the lid body and the outer film. The covering comprises a resin, as described in item 1A or 2A. Item 4A. The energy storage device according to any one of items 1A to 3A, further comprising an adhesive layer between the barrier layer and the heat-fusible resin layer. Item 5A. The energy storage device according to any one of items 1A to 4A, further comprising a base layer on the side of the barrier layer opposite to the side of the heat-fusible resin layer. Item 6A. The energy storage device according to item 5A, further comprising an adhesive layer between the substrate layer and the barrier layer. Item 7A. The energy storage device according to any one of items 1A to 6A, wherein the outer film has a Young's modulus of 6000 MPa or more. Item 8A. A method for manufacturing an energy storage device, The aforementioned energy storage device is Electrode body and The electrode body is enclosed by an outer casing, The exterior body is, The outer film enclosing the electrode body, It has a lid that seals the electrode body together with the outer film, The exterior film is composed of a laminate comprising at least a barrier layer and a heat-sealable resin layer. The barrier layer has a ratio (R1 / R2) of area-average crystal grain size R1 (μm) to area-average crystal grain size R2 (μm) of 55% or more. The area-average grain size R1 (μm) is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicular to the surface of the barrier layer, in a direction perpendicular to the rolling direction of the barrier layer, at the position where the heat-sealable resin layer of the outer film is heat-sealed to the lid. The area-average grain size R2 (μm) is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicular to the surface of the barrier layer, in a direction perpendicular to the rolling direction of the barrier layer, at a position where the heat-sealable resin layer of the outer film is not heat-sealed. The process includes sealing the electrode body with the outer casing, A method for manufacturing energy storage devices.

[0295] Furthermore, as described above, this disclosure provides inventions in the following embodiments. Item 1B. An exterior material for an energy storage device comprising at least a laminate comprising a barrier layer and a heat-sealable resin layer, The barrier layer has a ratio (R1 / R2) of area-average crystal grain size R1 (μm) to area-average crystal grain size R2 (μm) of 55% or more. The area-average grain size R1 (μm) is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicular to the surface of the barrier layer, in a direction perpendicular to the rolling direction of the barrier layer, at a position where the heat-sealable resin layer of the exterior material for the energy storage device and the polypropylene plate are heat-sealed under the condition that the thickness of the heat-sealable resin layer is 20% or more and 80% or less. The area-average grain size R2 (μm) is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicular to the surface of the barrier layer, in a direction perpendicular to the rolling direction of the barrier layer, at a position where the heat-fusible resin layer of the exterior material for the energy storage device and the polypropylene plate are not heat-fussed together. Exterior material for energy storage devices. Item 2B. The exterior material for an energy storage device according to Item 1B, wherein the barrier layer is formed of stainless steel, steel sheet, or aluminum alloy. Item 3B. The exterior material for an energy storage device according to item 1B or 2B, further comprising an adhesive layer between the barrier layer and the heat-fusible resin layer. Item 4B. An exterior material for an energy storage device according to any one of items 1B to 3B, further comprising a base material layer on the side of the barrier layer opposite to the side of the heat-fusible resin layer. Item 5B. The exterior material for an energy storage device according to Item 4B, further comprising an adhesive layer between the base material layer and the barrier layer. Item 6B. The exterior material for the energy storage device is the exterior material for the energy storage device according to any one of items 1B to 5B, wherein the Young's modulus is 6000 MPa or more. Item 7B. A method for manufacturing an exterior material for an energy storage device, The process includes at least a step of obtaining a laminate in which a barrier layer and a heat-fusible resin layer are laminated, The barrier layer has a ratio (R1 / R2) of area-average crystal grain size R1 (μm) to area-average crystal grain size R2 (μm) of 55% or more. The area-average grain size R1 (μm) is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicular to the surface of the barrier layer, in a direction perpendicular to the rolling direction of the barrier layer, at a position where the heat-sealable resin layer of the exterior material for the energy storage device and the polypropylene plate are heat-sealed under the condition that the thickness of the heat-sealable resin layer is 20% or more and 80% or less. The area-average grain size R2 (μm) is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicular to the surface of the barrier layer, in a direction perpendicular to the rolling direction of the barrier layer, at a position where the heat-fusible resin layer of the exterior material for the energy storage device and the polypropylene plate are not heat-fussed together. A method for manufacturing exterior materials for energy storage devices. Item 8B. An energy storage device in which an energy storage device element comprising at least a positive electrode, a negative electrode, and an electrolyte is housed in a package formed from an outer covering material for energy storage devices as described in any one of items 1B to 6B. [Explanation of symbols]

[0296] 1 Base material layer 2 Adhesive layer 3. Barrier layer 4 Heat-fusible resin layer 5 Adhesive layer 6 Surface coating layer 10 Energy storage devices 20 Electrode body 30 electrode terminal 40 Exterior 50. Exterior film (exterior material for energy storage devices) 51 Base material layer 52 Barrier layer 53 Heat-fusible resin layer 54 Adhesive layer 55 Adhesive layer 60 Lid 61 Lid body 62 Covering 70 First sealing section 80 Second sealing section

Claims

[Claim 1] It is an energy storage device, Electrode body and The electrode body is enclosed by an outer casing, The exterior body is, The outer film enclosing the electrode body, It has a lid that seals the electrode body together with the outer film, The exterior film is composed of a laminate comprising at least a barrier layer and a heat-sealable resin layer. The barrier layer has a ratio (R1 / R2) of area-average grain size R1 (μm) to area-average grain size R2 (μm) of 55% or more. The area-average grain size R1 (μm) is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicular to the surface of the barrier layer, in a direction perpendicular to the rolling direction of the barrier layer, at the position where the heat-sealable resin layer of the outer film is heat-sealed to the lid. The area-average grain size R2 (μm) is obtained by performing crystal analysis by EBSD on a cross-section obtained by cutting the barrier layer perpendicular to the surface of the barrier layer, in a direction perpendicular to the rolling direction of the barrier layer, at a position where the heat-fusible resin layer of the outer film is not heat-fussed. Energy storage device.

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