Power storage device and manufacturing method thereof, and exterior material for power storage device and manufacturing method thereof

Abstract

To provide an exterior material for a power storage device that is suppressed from cracking in a sealing portion between the exterior material for a power storage device and a lid when the power storage device is repeatedly exposed to high and low temperature changes, a method for manufacturing the same, and a power storage device.SOLUTION: An exterior material for a power storage device is composed of a laminate including at least a barrier layer and a heat-sealable resin layer, and the barrier layer has a ratio (R1 / R2) of an area average crystal grain size R1 (μm) to an area average crystal grain size R2 (μm) of 55% or more, is not subjected to cold forming, and is used by wrapping the exterior material for a power storage device around an electrode body to seal the electrode body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Various types of electricity storage devices have been developed, but in all of them, exterior materials are essential components for sealing the electricity storage device elements such as electrodes and electrolytes. Conventionally, metal exterior materials have been widely used as exterior films.

[0003] Meanwhile, in recent years, with the increasing performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, etc., there has been a demand for energy storage devices to be thinner and lighter in addition to being available in a variety of shapes. However, the metal exterior films that have been widely used up until now have the drawback of being difficult to accommodate the increasing variety of shapes and also having limitations on how much weight they can achieve.

[0004] Therefore, in recent years, a film-like laminate in which a base layer / barrier layer / thermally adhesive resin layer are laminated in this order has been proposed as an exterior film that can be easily processed into various shapes and can be made thinner and lighter (see, for example, Patent Document 1).

[0005] Patent Document 2 also discloses an example of an electricity storage device. This electricity storage device includes an electrode assembly and an exterior body that seals the electrode assembly. The exterior body includes an exterior film that wraps the electrode assembly and a lid that is joined to the exterior film. This electricity storage device is manufactured, for example, by accommodating the electrode assembly inside a cylindrical exterior film and closing the opening of the cylindrical exterior film with the lid. The side surface of the lid and the exterior film are joined, for example, by heat sealing. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-287971 [Patent Document 2] Japanese Patent Publication No. 2022-123686 Summary of the Invention [Problem to be solved by the invention]

[0007] An exterior body including an exterior film (exterior material for an electricity storage device) that wraps an electrode body and a lid body that is joined to the exterior film, as disclosed in Patent Document 2, is useful as an exterior body for a large electricity storage device, for example.

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

[0009] Under these circumstances, the main objective of the present disclosure is to provide an energy storage device that uses an exterior body including an exterior film (exterior material for an energy storage device) that wraps an electrode body and a lid body, and that is capable of suppressing the occurrence of cracks in the sealing portion between the exterior film and the lid body when the energy storage device is repeatedly exposed to high and low temperature changes.

[0010] Another object of the present disclosure is to provide an exterior material for an electricity storage device that uses an exterior body including an exterior material for an electricity storage device that encases an electrode body and a lid body, and that is capable of suppressing the occurrence of cracks in the sealing portion of the exterior material for an electricity storage device with the lid body when the electricity storage device is repeatedly exposed to high and low temperature changes. [Means for solving the problem]

[0011] The inventors of the present disclosure conducted extensive research to solve the above-mentioned problems and found that, in an electricity storage device including an electrode assembly and an exterior body that seals the electrode assembly, the exterior body includes an exterior film that wraps the electrode assembly and a lid that seals the electrode assembly together with the exterior film, the exterior film is composed of a laminate including at least a barrier layer and a heat-sealable resin layer, and the ratio (R1 / R2) of the area-average crystal grain size R1 (μm) to the area-average crystal grain size R2 (μm) of the barrier layer, which will be described later, is 55% or more, thereby suppressing the occurrence of cracks in the sealing portion of the exterior film with the lid when the electricity storage device is repeatedly exposed to high and low temperature changes.

[0012] The present disclosure has been completed based on these findings and further investigations. That is, the present disclosure provides the inventions of the following aspects. An electricity storage device, An electrode body; an exterior body that seals the electrode body, The outer casing is an exterior film that wraps the electrode body; a lid that seals the electrode body together with the exterior film, the exterior film is composed of a laminate including at least a barrier layer and a heat-sealable resin layer, the barrier layer has a ratio (R1 / R2) of an area average crystal grain size R1 (μm) to an area average crystal grain size R2 (μm) of 55% or more; The area average crystal grain size R1 (μm) is an area average crystal grain size (μm) obtained by performing crystal analysis by EBSD on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position where the heat-fusible resin layer of the packaging film is heat-fused to the lid, The area average crystal grain size R2 (μm) is an area average crystal grain size (μm) obtained by performing crystal analysis by EBSD on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position of the packaging film where the heat-sealable resin layer is not heat-sealed, Energy storage device.

[0013] Furthermore, the inventors of the present disclosure conducted extensive research to solve the above-mentioned problems, and as a result, they found that in a packaging material for an electricity storage device constituted by a laminate including at least a barrier layer and a heat-sealable resin layer, when the ratio (R1 / R2) of the area average crystal grain size R1 (μm) to the area average crystal grain size R2 (μm) of the barrier layer, which will be described later, is 55% or more, the occurrence of cracks in the sealing portion of the packaging material for an electricity storage device with the lid can be suppressed when the electricity storage device is repeatedly exposed to high and low temperature changes.

[0014] The present disclosure has been completed based on these findings and further investigations. That is, the present disclosure also provides the inventions of the following aspects. An exterior packaging material for an electricity storage device, which is composed of a laminate including at least a barrier layer and a heat-sealable resin layer, the barrier layer has a ratio (R1 / R2) of an area average crystal grain size R1 (μm) to an area average crystal grain size R2 (μm) of 55% or more; The area average crystal grain size R1 (μm) is an area average crystal grain size (μm) obtained by performing crystal analysis by EBSD on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position where the heat-fusion resin layer of the packaging material for an electricity storage device and a polypropylene plate are heat-fused under conditions such that the thickness of the heat-fusion resin layer is 20% or more and 80% or less, The area average crystal grain size R2 (μm) is an area average crystal grain size (μm) obtained by performing crystal analysis by EBSD on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position where the heat-fusible resin layer of the exterior material for an electricity storage device and the polypropylene plate are not heat-fused. Exterior material for energy storage devices. [Effects of the Invention]

[0015] According to the present disclosure, it is possible to provide an electricity storage device that uses an exterior body including an exterior film that encases an electrode body and a lid body, in which, when the electricity storage device is repeatedly exposed to high and low temperature changes, the occurrence of cracks in the sealing portion of the exterior film with the lid body (more specifically, the occurrence of cracks in the barrier layer) is suppressed. Furthermore, according to the present disclosure, it is also possible to provide a method for manufacturing the electricity storage device.

[0016] Furthermore, according to the present disclosure, it is also possible to provide an electrical storage device packaging material that suppresses the occurrence of cracks in the sealing portion of the electrical storage device packaging material with the lid body (more specifically, the occurrence of cracks in the barrier layer) when the electrical storage device is repeatedly exposed to high and low temperature changes in an electrical storage device that uses an packaging body including the electrical storage device packaging material that wraps an electrode body and a lid body. Furthermore, according to the present disclosure, it is also possible to provide a method for manufacturing the electrical storage device packaging material, and an electrical storage device that uses the electrical storage device packaging material. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a perspective view illustrating an example of an electricity storage device according to the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] FIG. 2 is a schematic diagram illustrating an example of a lid according to the present disclosure. [Figure 4] 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior film of the present disclosure. [Figure 5] 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior packaging material for an electricity storage device according to the present disclosure. [Figure 6] 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior packaging material for an electricity storage device according to the present disclosure. [Figure 7] 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior packaging material for an electricity storage device according to the present disclosure. [Figure 8] 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior packaging material for an electricity storage device according to the present disclosure. [Figure 9] FIG. 2 is a schematic diagram illustrating a method for housing an electricity storage device element in a package formed from the exterior packaging material for an electricity storage device of the present disclosure. [Figure 10] 1 is a perspective view showing an example of an electricity storage device according to the present disclosure that uses an exterior material for an electricity storage device according to the present disclosure. [Figure 11] FIG. 11 is a cross-sectional view taken along line AA in FIG. [Figure 12] FIG. 2 is a schematic diagram illustrating an example of a lid according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

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

[0019] The packaging material for an electricity storage device according to the present disclosure is composed of a laminate including at least a barrier layer and a heat-sealable resin layer in this order, and 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, and the area-average crystal grain size R1 (μm) is determined to be 55% or more in a direction perpendicular to the rolling direction of the barrier layer and extending from the surface of the barrier layer at a position where the heat-sealable resin layer of the packaging material for an electricity storage device and a polypropylene plate are heat-sealed under conditions such that the thickness of the heat-sealable resin layer is 20% or more and 80% or less. and the area-average crystal grain size R2 (μm) is an area-average crystal grain size (μm) obtained by performing crystal analysis by EBSD on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer at a position where the heat-sealable resin layer of the electrical storage device packaging material and the polypropylene plate are not heat-sealed, the cross section being perpendicular to the rolling direction of the barrier layer and being obtained by performing crystal analysis by EBSD on the cross section obtained by cutting the barrier layer in a direction perpendicular to the surface of the barrier layer. According to the electrical storage device packaging material of the present disclosure, by having this configuration, the occurrence of cracks in the sealing portion of the electrical storage device packaging material with the lid is suppressed.

[0020] The electricity storage device and exterior film (hereinafter also referred to as an exterior material for an electricity storage device) of the present disclosure will be described in detail below. In this disclosure, a numerical range indicated by "to" means "greater than or equal to" or "less than or equal to." For example, the notation 2 to 15 mm means 2 mm or more and 15 mm or less. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Separately described upper and lower limits, upper and lower limits, or lower and lower limits may be combined to form a numerical range. In the numerical ranges described in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.

[0021] In the packaging film and the packaging material for an electricity storage device, the MD (Machine Direction) and TD (Transverse Direction) of the barrier layer 52 and the barrier layer 3 described below can usually be determined during their manufacturing process. For example, when the barrier layer 52 and the barrier layer 3 are each made of a metal foil such as an aluminum alloy foil or a stainless steel foil, linear lines called rolling marks are formed on the surface of the metal foil in the rolling direction (RD) of the metal foil. 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. Furthermore, during the manufacturing process of a laminate, the MD of the laminate usually coincides with the RD of the metal foil. Therefore, the MD of the laminate can be determined by observing the surface of the metal foil of the laminate and identifying the rolling direction (RD) of the metal foil. Furthermore, since the TD of the laminate is perpendicular to the MD of the laminate, the TD of the laminate can also be identified.

[0022] Furthermore, when the MD of the exterior film cannot be identified due to rolling marks on the metal foil, such as aluminum alloy foil or stainless steel foil, it can be identified by the following method. One method for identifying the MD of the exterior film is to observe the cross section of the heat-sealable resin layer of the exterior film using an electron microscope to confirm the sea-island structure. In this method, the direction parallel to the cross section in which the average diameter of the island shapes in the direction perpendicular to the thickness direction of the heat-sealable resin layer is the largest can be determined as the MD. Specifically, the sea-island structure is confirmed by observing the longitudinal cross section of the heat-sealable resin layer and each cross section, angled 10 degrees from the direction parallel to the longitudinal cross section, up to the direction perpendicular to the longitudinal cross section (a total of 10 cross sections), using an electron microscope. Next, the shape of each individual island is observed in each cross section. For each island shape, the linear distance connecting the leftmost end in the direction perpendicular to the thickness direction of the heat-sealable resin layer to the rightmost end in that direction is defined as the diameter y. For each cross section, the average of the diameters y of the top 20 island shapes in order of largest diameter y is calculated. The direction parallel to the cross section where the average diameter y of the island shape was the largest was determined to be the MD.

[0023] <1-1. Configuration of the power storage device> FIG. 1 is a perspective view schematically showing an electricity storage device 10. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. FIG. 3 is a schematic view showing an example of a lid body 60. FIG. 4 is a cross-sectional view showing an example of a laminated structure of an exterior film 50 provided in the electricity storage device 10 of FIG. 1. In FIGS. 1 to 3, the arrow z direction (z1 direction and z2 direction) indicates the thickness direction of the electricity storage device 10, the arrow x direction (x1 direction and x2 direction) indicates the width direction of the electricity storage device 10, and the arrow y direction (y1 direction and y2 direction) indicates the depth direction of the electricity storage device 10. The directions indicated by the arrows x, y, and z are common to the subsequent figures.

[0024] The electricity storage device 10 includes an electrode body 20, an electrode terminal 30, and an exterior body 40. The electrode body 20 includes electrodes (positive and negative electrodes) constituting an electricity storage member such as a lithium-ion battery, a capacitor, an all-solid-state battery, a semi-solid battery, a quasi-solid battery, a polymer battery, an all-resin battery, a lead-acid battery, a nickel-metal hydride battery, a nickel-cadmium battery, a nickel-iron battery, a nickel-zinc battery, a silver oxide-zinc battery, a metal-air battery, a polyvalent cation battery, or a capacitor, as well as a separator. In the present disclosure, the shape of the electrode body 20 is, for example, an approximately rectangular parallelepiped. Note that the term "approximately rectangular parallelepiped" includes not only a perfect rectangular parallelepiped, but also a solid that can be considered a rectangular parallelepiped by modifying the shape of a portion of its outer surface, for example. The shape of the electrode body 20 may be, for example, a cylinder or a polygonal prism.

[0025] The power storage device 10 in FIGS. 1 and 2 includes two electrode terminals 30. The electrode terminals 30 are metal terminals used for inputting and outputting electric power to and from the electrode assembly 20. One end of the electrode terminal 30 is electrically connected to an electrode (positive electrode or negative electrode) included in the electrode assembly 20. The other end of the electrode terminal 30 protrudes outward from, for example, an edge of the exterior body 40. Note that the electrode terminal 30 may be any terminal as long as it is capable of inputting and outputting electric power to and from the electrode assembly 20, and may not, for example, protrude from the exterior body 40. For example, when the lid body 60 described below is made of a conductive material, the lid body 60 may also function as the electrode terminal 30. In this case, the lid body 60, which functions as an electrode terminal, may or may not protrude from the exterior body 40.

[0026] The metal material constituting the electrode terminal 30 is, for example, aluminum, nickel, or copper. For example, when 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, and may be, for example, a protective tape or a separator. The outer shape of the electrode body 20 is, for example, a rectangular parallelepiped.

[0027] The exterior body 40 seals the electrode assembly 20. The exterior body 40 includes an exterior film 50 and a lid 60. The exterior film 50 wraps the electrode assembly 20. In FIGS. 1 and 2 , the exterior film 50 is wrapped around the electrode assembly 20. The lid 60 is disposed on the side of the electrode assembly 20 in the y direction. In another example, the electrode assembly 20 may be housed inside an exterior film 50 configured in a cylindrical shape so that openings are formed at both ends in the y direction, and the openings may be closed by the lid 60. In yet another example, the electrode assembly 20 connected to the lid 60 may be housed inside an exterior film 50 configured in a cylindrical shape so that openings are formed, and the openings may be closed by the lid 60.

[0028] The exterior body 40 has a pair of main surfaces and a pair of side surfaces formed by an exterior film 50. In FIGS. 1 and 2, the pair of main surfaces are substantially the same size. Furthermore, the pair of side surfaces are substantially the same size. The pair of main surfaces each have a larger area than the pair of side surfaces. The pair of lid bodies 60 are respectively disposed on the sides of the electrode body 20 so as to close the pair of openings. Note that in the present disclosure, the main surfaces and side surfaces are the surfaces of the exterior body 40 excluding the lid bodies 60.

[0029] For example, there is a method of forming a storage portion (recess) in the exterior film 50 through cold forming to store the electrode assembly 20. However, it is not necessarily easy to form a deep storage portion using this method. Attempting to form a deep storage portion (recess) through cold forming (for example, a forming depth of 15 mm) increases the likelihood of pinholes or cracks occurring in the exterior film 50, resulting in a decrease in battery performance. On the other hand, the exterior body 40 seals the electrode assembly 20 by wrapping the exterior film 50 around the electrode assembly 20, and therefore can easily seal the electrode assembly 20 regardless of the thickness of the electrode assembly 20. Note that in order to reduce the dead space between the electrode assembly 20 and the exterior film 50 and improve the volumetric energy density of the power storage device 10, it is preferable that the exterior film 50 be wrapped so as to contact the outer surface of the electrode assembly 20. Furthermore, in all-solid-state batteries, it is necessary to apply a high pressure uniformly from the outer surface of the battery to maximize battery performance, so it is necessary to eliminate the space between the electrode assembly 20 and the exterior film 50. Therefore, it is preferable that the exterior film 50 be wrapped so as to contact the outer surface of the electrode assembly 20. When wrapping the exterior film 50 around the electrode body 20, only one exterior film 50 may be wrapped around the electrode body 20, or multiple exterior films 50 may be wrapped around the electrode body 20. In addition to a mode in which the mutually facing surfaces of the exterior films 50 are heat-sealed, a mode in which the outer surface and inner surface of the exterior film 50 are heat-sealed is also preferred.

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

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

[0032] Specific examples of resins include thermoplastic resins such as polyester, polyolefin, polyamide, epoxy resin, acrylic resin, fluororesin, polyurethane, silicone resin, and phenolic resin, as well as modified versions of these resins. The resin material may be a mixture of these resins, a copolymer, or a modified 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 using any molding method.

[0033] Specific examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymer polyesters. Examples of copolymer polyesters include copolymer polyesters whose repeating units are primarily ethylene terephthalate. Specific examples include copolymer polyesters in which ethylene terephthalate is the main repeating unit and is polymerized with ethylene isophthalate (hereinafter abbreviated as polyethylene (terephthalate / isophthalate)), polyethylene (terephthalate / adipate), polyethylene (terephthalate / sodium sulfoisophthalate), polyethylene (terephthalate / sodium isophthalate), polyethylene (terephthalate / phenyl dicarboxylate), and polyethylene (terephthalate / decane dicarboxylate). Among these, polybutylene terephthalate is preferred as the resin material from the viewpoint of improving heat resistance and pressure resistance.

[0034] Specific examples of polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); propylene-α-olefin copolymers; and ethylene-butene-propylene terpolymers. When the polyolefin resin is a copolymer, it may be a block copolymer or a random copolymer. Among these, polypropylene is preferred as the resin material because of its excellent heat-sealing properties and electrolyte resistance.

[0035] The resin as the resin material may contain a filler as needed. Specific examples of the filler include glass beads, graphite, glass fiber, and carbon fiber. By including the filler in the resin as the resin material, the deformation resistance of the lid 60 against temperature changes can be improved.

[0036] The melt mass flow rate (measured at 230°C) of the resin material contained in the material constituting the lid 60 is preferably in the range of 1 g / 10 min to 100 g / 10 min, more preferably in the range of 1 g / 10 min to 80 g / 10 min, more preferably in the range of 1 g / 10 min to 60 g / 10 min, more preferably in the range of 5 g / 10 min to 100 g / 10 min, more preferably in the range of 5 g / 10 min to 80 g / 10 min, and even 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 configured to contain a conductive material. "Containing a conductive material" means that, when the entire material constituting the lid 60 is taken as 100% by mass, the content of the conductive material is 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. In other words, the material constituting the lid 60 can contain, in addition to the conductive material, a material other than the conductive material.

[0038] The conductive material forming the lid body 60 is, for example, a metal material. The metal material forming the lid body 60 is, for example, aluminum, an aluminum alloy, nickel, copper, or a copper alloy. For example, when the electrode body 20 is a lithium-ion battery, the lid body 60 connected to the positive electrode is preferably formed of aluminum or an aluminum alloy. The lid body 60 connected to the negative electrode is preferably formed of nickel, copper, or a copper alloy. The material forming the lid body 60 connected to the negative electrode may be copper plated with nickel. The material forming the lid body 60 may include recycled metal materials. When the lid body 60 is formed of a conductive material, the lid body 60 also functions as the electrode terminal 30, so the electrode terminal 30 can be omitted from the electricity storage device 10.

[0039] The lid 60 may be configured such that at least a portion of the lid main body 61 is covered with the covering body 62. In the lid 60 of FIG. 3, the periphery of the lid main body 61 (the periphery of the thickness portion) is covered with the covering body 62. The lid 60 may be joined to the heat-sealable resin layer 53 of the exterior film 50 via the covering body 62. The covering body 62 is preferably configured to contain a resin material. The lid 60 has the lid main body 61 and the covering body 62 that joins the lid main body 61 and the exterior film 50, and the covering body 62 can be configured to contain a resin (resin material). The definition of "comprising a resin material" regarding the covering body 62 is the same as in the case of the lid 60.

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

[0041] When the lid 60 contains a conductive material, the lid 60 may be bonded to the exterior film 50 via an adhesive film instead of a covering. Any adhesive film can be selected as long as it can bond the exterior film 50 and the lid 60. The adhesive film is preferably a laminated film having at least a heat-sealable resin layer, a heat-resistant substrate layer, and a heat-sealable resin layer in this order. The specifications for the heat-sealable resin layer of the adhesive film are the same as those for the heat-sealable resin layer 53. The materials constituting the heat-sealable resin layers on both sides of the adhesive film may be the same or different, and are appropriately selected according to the materials constituting the heat-sealable resin layer 53 of the exterior film 50 and the material constituting the lid 60. The material constituting the heat-sealable resin layer of the adhesive film on the side bonded to the lid 60 is preferably an acid-modified polyolefin resin graft-modified with an acid such as maleic anhydride. The heat-sealable resin layer of the adhesive film on the side that is bonded to the exterior film 50 is preferably made of the same type of material as the material that constitutes the heat-sealable resin layer 53 of the exterior film 50 .

[0042] The heat-resistant substrate layer may be any film made of a heat-resistant resin, such as a non-stretched or stretched film of polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polymethylpentene (registered trademark), polyacetal cyclic polyolefin, polyethylene, polypropylene, etc. Polyethylene terephthalate is particularly preferred because it is inexpensive and has high strength.

[0043] The adhesive film preferably has adhesiveness. When the second sealing portion 80 described below is formed with the adhesive film disposed between the exterior film 50 and the lid 60, the adhesive film is less likely to shift position relative to the lid 60 and the exterior film 50. By incorporating a tackifier resin into the heat-sealable resin layer of the adhesive film, adhesiveness can be imparted to the adhesive film. Examples of the tackifier resin include amorphous polyolefins. Examples of amorphous polyolefins include amorphous polypropylene and copolymers of amorphous propylene and other α-olefins. The content of the tackifier resin relative to the base material constituting the heat-sealable resin is preferably 10 to 20% by weight or less.

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

[0045] When the lid body 60 is a cylinder, a prism, a rectangular parallelepiped, a cube, or the like, it is preferable that the lid body 60 have a certain thickness in the thickness direction (y direction) so that deformation of the exterior body 40 is suppressed even when the power storage device 10 is placed on top of it. From another perspective, when the lid body 60 is a cylinder, a prism, a rectangular parallelepiped, a cube, or the like, it is preferable that the lid body 60 have a certain thickness in the thickness direction (y direction) so that the lid joint portion of the lid body 60 can be suitably joined to the exterior film 50 when forming the second sealing portion 80. The minimum value of the thickness in the thickness direction (y direction) of the lid body 60 (the distance in the y direction between the first main surface and the second main surface) is, for example, 1.0 mm, more preferably 3.0 mm, and even more preferably 4.0 mm. The maximum value of the thickness in the y direction of the lid body 60 is, for example, 20 mm, preferably 15.0 mm, more preferably 10.0 mm, even more preferably 8.0 mm, and even more preferably 7.0 mm. The maximum thickness of the lid 60 in the y direction may be 10 mm or more. Preferred ranges for the thickness of the material constituting the lid 60 are 1.0 mm to 20.0 mm, 1.0 mm to 15.0 mm, 1.0 mm to 10.0 mm, 1.0 mm to 8.0 mm, 1.0 mm to 7.0 mm, 3.0 mm to 20.0 mm, 3.0 mm to 15.0 mm, 3.0 mm to 10.0 mm, 3.0 mm to 8.0 mm, 3.0 mm to 7.0 mm, 4.0 mm to 20.0 mm, 4.0 mm to 15.0 mm, 4.0 mm to 10.0 mm, 4.0 mm to 8.0 mm, and 4.0 mm to 7.0 mm. In the present disclosure, when the lid body 60 is expressed as a cylinder, a prism, a rectangular parallelepiped, a cube, or the like, this does not include an embodiment in which the lid body 60 is made solely of a film as defined by the JIS (Japanese Industrial Standards) [Packaging Terminology] standard. The thickness of the lid body 60 may vary depending on the part of the lid body 60. When the thickness of the lid body 60 varies depending on the part, the thickness of the lid body 60 is the thickness of the thickest part.

[0046] 1 and 2 , a through-hole into which the electrode terminal 30 is inserted is formed in the lid 60. The through-hole penetrates the first and second main surfaces of the lid. When the electrode assembly 20 is stored, the electrode terminal 30 passes through the through-hole formed in the lid 60 and protrudes to the outside of the exterior body 40. A small gap between the through-hole of the lid 60 and the electrode terminal 30 is filled with, for example, resin. Note that, in the energy storage device 10, the position from which the electrode terminal 30 protrudes to the outside can be selected arbitrarily. For example, the electrode terminal 30 may protrude to the outside from a hole formed in any one of the six surfaces of the exterior body 40. In this case, a small gap between the exterior body 40 and the electrode terminal 30 is filled with, for example, resin. The electrode terminal 30 may protrude from between the lid 60 and the exterior film 50, or may protrude from a first sealing portion 70 described below. In the electricity storage device 10, the lid body 60 and the electrode terminal 30 are provided as separate bodies, but the lid body 60 and the electrode terminal 30 may be formed integrally. Note that if the electrode terminal 30 does not protrude from the edge of the exterior body 40, the lid body 60 does not need to have a through-hole formed therein.

[0047] In Figures 1 and 2, with the exterior film 50 wrapped around the electrode body 20, the facing surfaces of the exterior film 50 (heat-sealable resin layers 53) are heat-sealed to form the first sealing portion 70.

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

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

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

[0051] Here, the area average crystal grain size R1 (μm) of the barrier layer 52 is the area average crystal grain size (μm) obtained by performing crystal analysis using the EBSD method on a cross section obtained by cutting the barrier layer 52 in a direction perpendicular to the rolling direction of the barrier layer 52 and 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-sealable resin layer 53 of the exterior film 50 is heat-sealed to the lid body 60 (the position of the second sealing portion 80).

[0052] The area average crystal grain size R2 (μm) of the barrier layer 52 is the area average crystal grain size (μm) obtained by performing crystal analysis using the EBSD method on a cross section obtained by cutting the barrier layer 52 vertically from 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-sealable resin layer 53 of the exterior film 50 is not heat-sealed.

[0053] From the viewpoint of more suitably exerting the effects of the invention of the present disclosure, the ratio (R1 / R2) is preferably about 55% or more, more preferably about 60% or more, and even more preferably about 70% or more, and is preferably about 150% or less, more preferably about 140% or less, and even more preferably about 130% or less, and preferred ranges include about 55 to 150%, about 55 to 140%, about 55 to 130%, about 60 to 150%, about 60 to 140%, about 60 to 130%, about 70 to 150%, about 70 to 140%, and about 70 to 130%.

[0054] The area average crystal grain size R1 (μm) and the area average crystal 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, R2 of the barrier layer> For the power storage device, the barrier layer at the position where the heat-sealable resin layer of the exterior film is heat-sealed to the lid (sealed portion (second sealed portion)) and the barrier layer at the position where the heat-sealable resin layer of the exterior film is not heat-sealed (non-sealed portion) are obtained, and crystal analysis is performed using the EBSD method to measure the area average crystal grain sizes R1 and R2 of the barrier layer. The specific measurement method is as follows.

[0056] Crystal analysis was performed using the EBSD method on the cross section of each barrier layer perpendicular to the rolling direction, and the area-average crystal grain size of the barrier layer was measured. The details of the measurement conditions are as follows. The area-average crystal 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 crystal analysis using the EBSD method were linked together to obtain a diameter of approximately 5000 μm. 2 The area average crystal grain size of the crystals included in the measurement area is equal to or greater than 100 μm. The crystal grain size is the value measured for the crystals included in the measurement area, assuming that the crystal shape is circular. The standard deviation of the crystal grain size is approximately 5000 μm, obtained by combining multiple images obtained by crystal analysis using the EBSD method after removing areas with a CI value of 0.1 or less. 2It is calculated from the distribution of the crystal grain size (diameter when the crystal area is assumed to be a circle) of the crystals contained in the measurement area (the entire thickness direction of the barrier layer is the measurement area) described above. The area average crystal grain size R2 of the barrier layer is measured at a location 3 cm away from the measurement location of the area average crystal grain size R1.

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

[0058] (Pretreatment) As a pretreatment step, the barrier layer was cut perpendicular to the rolling direction (RD) to obtain a cross section. The rolling direction of the barrier layer was determined by observing the shiny surface of the barrier layer with a metallurgical microscope, and the direction of linear rolling marks was the direction of extension. Specifically, the barrier layer sample was first cut into a 5 mm (perpendicular to the rolling direction) x 10 mm (rolling direction) piece using a trimming razor, and then embedded in resin. Next, the barrier layer and the resin were cut using the trimming razor perpendicular to the rolling direction of the barrier layer, perpendicular to the surface of the barrier layer, to expose the cross section of the barrier layer. The resulting cross section was then trimmed using a microtome. To reduce mechanical distortion in the cross section, the microtome was used to cut the embedded resin and the barrier layer perpendicular to the cross section by approximately 1 mm. Next, a broad argon beam was irradiated perpendicular to the cross section using an ion milling device under the following conditions: a protrusion width of 50 μm, a voltage of 6 kV, and 4 hours. The measurement cross section was then prepared. This is a process for precisely exposing the cross section of the barrier layer so as to minimize mechanical damage to the crystal structure that occurred in the previous process. Note that in the present disclosure, the "perpendicular direction" when cutting the aluminum alloy foil is checked under a stereomicroscope, and therefore may include an error of about 10°. That is, the permissible range for the direction perpendicular to the rolling direction is 80 to 100° to the rolling direction, and the permissible range for the direction perpendicular to the surface is 80 to 100° with respect to the surface.

[0059] (SEM conditions) The conditions of the scanning electron microscope (SEM) used for the EBSD method are as follows: Observation magnification: 2000x (the standard observation magnification when taking photos is Polaroid 545) Accelerating voltage: 15 kV 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 is carried out using the crystal orientation analysis software OIM (Ver. 7.3) manufactured by TSL Solutions Co., Ltd. Multiple images are stitched together to measure an area of ​​approximately 5000 μm 2 The upper limit of the measurement area is, for example, approximately 30,000 μm 2 In this case, the measurement area is from the center of the barrier layer in the thickness direction to both ends, and the area where resin is attached to the cross section and the area where the acid-resistant film is present are excluded from the measurement area. The CI value is 0.1 or more, the grain boundary condition is 0.5 degrees or more, and the minimum grain size is 3 steps or more. After stitching the images, check the pole figures. If the center of the pole figure is off by 10° or more, rotate the crystal data to restore symmetry. The pole figure used as reference is measured from the sample surface using XRD. When obtaining a pole figure from the surface using EBSD, the sample surface is mechanically polished, flat-milled, electrolytically polished, etc., before performing a wide-area measurement to remove the influence of the mechanical crystal structure of the sample surface. The pole figure obtained from the surface direction is then rotated 90° so that it is the same as the pole figure obtained from the same orientation as the pole figure obtained from the cross section of the target sample. Use this pole figure as a reference. The analysis is performed by excluding data with a Confidence Index (CI value) of 0.1 or less, as defined by OIM (Ver. 7.3), a crystal orientation analysis software made by TSL Solutions Co., Ltd. This makes it possible to exclude data based on the resin used in pre-processing present on the front and back of the sample, grain boundaries present on the cross section, and amorphous matter.

[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 the exterior film 50 and the lid 60 are heat-sealed 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 exterior film 50), it is possible to increase the ratio (R1 / R2) of the area-average crystal grain size R1 (μm) to the area-average crystal grain size R2 (μm) of the barrier layer 52. The preferred Young's modulus of the barrier layer 52 will be described later. For example, increasing the thickness of the barrier layer 52 or using a high-strength metal is effective.

[0063] Furthermore, for example, when the barrier layer 52 is formed of an aluminum alloy foil, if the aluminum alloy composition is in the JIS 8000 series, 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 JIS 5000 series, the strength of the soft foil can be increased by solid solution strengthening by dissolving Mg in aluminum.

[0064] Refining the crystal grains of the metal forming the barrier layer 52 is also effective in increasing the ratio (R1 / R2). For example, in the case of aluminum alloy compositions in the JIS 8000 and 5000 series, Al-Fe intermetallic compounds are crystallized during casting, and these compounds act as nuclei to refine the crystal grains. Furthermore, when differential speed rolling (a method in which rolls are rolled at different peripheral speeds) is employed, the rolled material undergoes shear deformation throughout the entire thickness in addition to the normal rolling deformation. As a result, crystal rotation is promoted, accelerating the transformation of subgrain boundaries into high-angle grain boundaries, resulting in the generation of fine crystal grains. While this method is also effective in cold rolling, warm rolling is more effective. Furthermore, increasing the number of rolling passes in the hot rolling of aluminum alloy foil and increasing the final cold rolling reduction are also effective. The higher the final cold rolling reduction from the intermediate annealing to the final thickness (e.g., 80% or higher), the greater the amount of strain accumulated in the aluminum alloy foil, resulting in refined recrystallized grains after final annealing.

[0065] The rolling conditions for the aluminum foil are adjusted by adjusting the conditions such as the rolling reduction, heating temperature, heating time, etc. For example, a method including 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 in which the ingot is held at about 300 to 450 ° C for about 1 to 10 hours, a cold rolling process in which the rolling reduction from the intermediate annealing to the final rolling is 80% or more, more preferably 90% or more, and a final annealing process in which the ingot is held at about 250 to 400 ° C for about 30 to 100 hours, can be mentioned, but the conditions for refining the crystal grains are not limited to these.

[0066] Furthermore, it is also effective to make the linear expansion coefficient of the barrier layer 52 close to the linear expansion coefficient of the material used for the lid 60 (lid main body 61 or cover 62).

[0067] <1-3. Method for manufacturing electricity storage devices> The electricity storage device of the present disclosure can be manufactured by assembling the electrode body 20, electrode terminal 30, exterior film 50, and lid body 60 of the present disclosure. These can be assembled using, for example, a known method. Specific examples of the electricity storage device of the present disclosure are shown below.

[0068] A pair of lid bodies 60 to which the electrode terminals 30 are joined are placed on the electrode body 20, and the electrode terminals 30 and the electrode body 20 are electrically connected. Note that the lid bodies 60 may be joined to the electrode terminals 30 that are electrically connected to the electrode body 20.

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

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

[0071] <2-1. Laminate structure and physical properties of exterior film (exterior material for energy storage devices)> An exterior film (exterior material for an electricity storage device) 50 of the present disclosure is composed of a laminate including a barrier layer 52 and a heat-sealable resin layer 53, as shown in FIG. 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 electricity storage device using the exterior film 50 and electricity storage device elements (electrode body 20, electrode terminal 30, etc.), the electrode body 20 is housed in a space formed by heat-sealing the edges of the exterior film 50 together with the lid 60 with the heat-sealable resin layers 53 of the exterior film 50 facing each other. In the laminate constituting the exterior film 50 of the present disclosure, with the barrier layer 52 as the reference, the side of the heat-sealable resin layer 53 relative to the barrier layer 52 is the inner side, and the opposite side is the outer side.

[0072] As shown in Fig. 4, for example, the exterior film 50 may have a base material layer 51 on the outside of the barrier layer 52, if necessary. Furthermore, as shown in Fig. 4, for example, the exterior film 50 may have an adhesive layer 54 between the base material layer 51 and the barrier layer 52, if necessary, for the purpose of increasing the adhesion between these layers. Furthermore, as shown in Fig. 4, for example, the exterior film 50 may have an adhesive layer 55 between the barrier layer 52 and the heat-sealable resin layer 53, if necessary, for the purpose of increasing the adhesion between these layers. Furthermore, as shown in Fig. 4, a surface coating layer (not shown) or the like may be provided on the outside of the base material layer 51 (the side opposite to the heat-sealable resin layer 53), if necessary.

[0073] The thickness of the laminate constituting the exterior film 50 is not particularly limited, but from the viewpoint of cost reduction, improvement of energy density, etc., it is, for example, 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 film to protect the electrode assembly 20, the thickness of the laminate constituting the exterior film 50 is preferably about 35 μm or more, about 45 μm or more, or about 60 μm or more. Furthermore, preferred ranges for the laminate constituting the exterior film 50 include, for example, about 35 to 250 μm, about 35 to 190 μm, about 35 to 180 μm, about 35 to 155 μm, about 35 to 120 μm, about 45 to 250 μm, about 45 to 190 μm, about 45 to 180 μm, about 45 to 155 μm, about 45 to 120 μm, about 60 to 250 μm, about 60 to 190 μm, about 60 to 180 μm, about 60 to 155 μm, and about 60 to 120 μm. In particular, a thickness of about 60 to 155 μm is preferred when making the electricity storage device lighter and thinner, and a thickness of about 155 to 190 μm is preferred when improving the conformability when the exterior film is wrapped around the electrode body.

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

[0075] From the viewpoint of more suitably exerting the effects of the present invention, the Young's modulus of the packaging film 50 is preferably 6,000 MPa or more, more preferably 8,000 MPa or more, even more preferably 10,000 MPa or more, and is preferably 40,000 MPa or less, more preferably 35,000 MPa or less, even more preferably 30,000 MPa or less, with preferred ranges including about 6,000 to 40,000 MPa, about 6,000 to 35,000 MPa, about 6,000 to 30,000 MPa, about 8,000 to 40,000 MPa, about 8,000 to 35,000 MPa, about 8,000 to 30,000 MPa, about 10,000 to 40,000 MPa, about 10,000 to 35,000 MPa, and about 10,000 to 30,000 MPa. In the present disclosure, the Young's modulus of the packaging 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 exterior film was obtained under the following measurement conditions, and the Young's modulus (MPa) was calculated from the maximum value of the slope of the SS curve. (Measurement conditions) A tensile testing machine is used. Test piece shape: Dumbbell No. 7 Test piece width: 2 mm Test piece length: 35 mm Thickness of test piece: 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] As a method for increasing the Young's modulus of the exterior film 50, for example, increasing the Young's modulus of the barrier layer 52 as described above is effective.

[0078] <2-2. Layers that make up the exterior film> [Base material layer 51] In the present disclosure, the base material layer 51 is a layer that is provided as needed for the purpose of functioning as a base material for the exterior film, etc. The base material layer 51 is located on the outer layer side of the exterior film.

[0079] The material for forming the base layer 51 is not particularly limited as long as it functions as a base, i.e., has at least insulating properties. The base layer 51 can be formed using, for example, a resin, which may contain an additive described below.

[0080] When the substrate layer 51 is formed of a resin, the substrate layer 51 can be formed of, for example, a resin film. When the substrate layer 51 is formed of a resin film, a preformed resin film may be used as the substrate layer 51 when laminating the substrate layer 51 with the barrier layer 52 or the like to produce the exterior film 50 of the present disclosure. Alternatively, the resin forming the substrate layer 51 may be formed into a film on the surface of the barrier layer 52 or the like by extrusion molding, coating, or the like to form the substrate layer 51 formed 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, and simultaneous biaxial stretching. Examples of methods for applying the resin 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, silicone resin, and phenolic resin, as well as modified versions of these resins. The resin that forms the base layer 51 may also be a copolymer of these resins, a modified version of the copolymer, or a mixture of these resins.

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

[0084] Specific examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymer polyesters. Examples of copolymer polyesters include copolymer polyesters in which ethylene terephthalate is the main repeating unit. Specific examples include copolymer polyesters in which ethylene terephthalate is the main repeating unit and is polymerized with ethylene isophthalate (hereinafter abbreviated as polyethylene (terephthalate / isophthalate)), polyethylene (terephthalate / adipate), polyethylene (terephthalate / sodium sulfoisophthalate), polyethylene (terephthalate / sodium isophthalate), polyethylene (terephthalate / phenyl-dicarboxylate), and polyethylene (terephthalate / decanedicarboxylate). These polyesters may be used alone or in combination of two or more.

[0085] Specific examples of polyamides include aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, and copolymers of nylon 6 and nylon 66; hexamethylenediamine-isophthalic acid-terephthalic acid copolymer polyamides such as nylon 6I, nylon 6T, nylon 6IT, and nylon 6I6T (where I represents isophthalic acid and T represents terephthalic acid), which contain structural units derived from terephthalic acid and / or isophthalic acid; and aromatic polyamides such as polyamide MXD6 (polymetaxylylene adipamide); alicyclic polyamides such as polyamide PACM6 (polybis(4-aminocyclohexyl)methane adipamide); polyamides copolymerized with a lactam component or an isocyanate component such as 4,4'-diphenylmethane diisocyanate; polyesteramide copolymers and polyetheresteramide copolymers, which are copolymers of copolymerized polyamides with polyesters or polyalkylene ether glycols; and polyamides such as copolymers of these. These polyamides may be used singly or in combination of two or more.

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

[0087] The base material layer 51 may be a single layer, or may be composed of two or more layers. When the base material layer 51 is composed of two or more layers, the base material layer 51 may be a laminate in which resin films are laminated with an adhesive or the like, or a laminate of resin films formed by co-extrusion of resins into two or more layers. Furthermore, a laminate of resin films formed by co-extrusion of resins into two or more layers may be used as the base material layer 51 without being stretched, or may be uniaxially or biaxially stretched to form the base material layer 51.

[0088] Specific examples of laminates of two or more resin films in the base layer 51 include a laminate of a polyester film and a nylon film, a laminate of two or more nylon films, and a laminate of two or more polyester films. Preferred examples include a laminate of a stretched nylon film and a stretched polyester film, a laminate of two or more stretched nylon films, and a laminate of two or more stretched polyester films. For example, when the base layer 51 is a laminate of two resin films, a laminate of a polyester resin film and a polyester resin film, a laminate of a polyamide resin film and a polyamide resin film, or a laminate of a polyester resin film and a polyamide resin film is preferred. A laminate of a polyethylene terephthalate film and a polyethylene terephthalate film, a laminate of a nylon film and a nylon film, or a laminate of a polyethylene terephthalate film and a nylon film is more preferred. Furthermore, when the base layer 51 is a laminate of two or more resin films, it is preferred that the polyester resin film be positioned as the outermost layer of the base layer 51, because polyester resins are less likely to discolor when an electrolyte solution adheres to their surface. In the laminate of a polyester resin film and a polyamide resin film, preferred ranges of the thickness of the polyester resin film are about 2 to 33 μm, about 2 to 28 μm, about 2 to 23 μm, about 2 to 18 μm, about 2 to 11 μm, about 2 to 8 μm, about 10 to 33 μm, about 10 to 28 μm, about 10 to 23 μm, about 10 to 18 μm, about 10 to 11 μm, about 18 to 33 μm, and about 18 to 28 μm. and about 18 to 23 μm, and preferred ranges for the thickness of the polyamide resin film include about 2 to 33 μm, about 2 to 28 μm, about 2 to 23 μm, about 2 to 18 μm, about 2 to 11 μm, about 2 to 8 μm, about 10 to 33 μm, about 10 to 28 μm, about 10 to 23 μm, about 10 to 18 μm, about 10 to 11 μm, about 18 to 33 μm, about 18 to 28 μm, and about 18 to 23 μm.

[0089] When the base layer 51 is a laminate of two or more resin film layers, the two or more resin film layers may be laminated via an adhesive. Examples of preferred adhesives include those similar to those exemplified for the adhesive layer 54 described below. The method for laminating two or more resin film layers is not particularly limited, and known methods can be used, such as dry lamination, sandwich lamination, extrusion lamination, and thermal lamination, with dry lamination being preferred. When laminating using the dry lamination method, a polyurethane adhesive is preferably used as the adhesive. In this case, the thickness of the adhesive may be, for example, about 2 to 5 μm. Alternatively, an anchor coat layer may be formed on the resin film before lamination. Examples of the anchor coat layer include those similar to those exemplified for the adhesive layer 54 described below. In this case, the thickness of the anchor coat layer may be, for example, about 0.01 to 1.0 μm.

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

[0091] In the present disclosure, from the viewpoint of improving the conformability of the exterior film, it is preferable that a lubricant be present on at least one of the surface and the interior of the base layer 51. The lubricant is not particularly limited, but preferably an amide-based lubricant is used. Specific examples of amide-based lubricants include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides. Specific examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Specific examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Specific examples of substituted amides include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, and N-stearyl erucic acid amide. Specific examples of methylolamides include methylol stearic acid amide. Specific examples of saturated fatty acid bisamides include methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene hydroxystearic acid amide, N,N'-distearyl adipamide, and N,N'-distearyl sebacic acid amide. Specific examples of unsaturated fatty acid bisamides include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipamide, and N,N'-dioleyl sebacic acid amide. Specific examples of fatty acid ester amides include stearamidoethyl stearate. Specific examples of aromatic bisamides include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, and N,N'-distearylisophthalic acid amide.The lubricant may be used alone or in combination of two or more kinds, and it is preferable to use a combination of two or more kinds.

[0092] When a lubricant is present on the surface of the base layer 51, the amount of the lubricant is not particularly limited, but may be, for example, about 3 mg / m 2 or more, preferably about 4 mg / m 2 More than about 5mg / m 2 The amount of lubricant present on the surface of the base layer 51 is, for example, about 15 mg / m 2 or less, preferably about 14 mg / m 2 Below, about 10mg / m 2 The preferred range of the amount of lubricant present on the surface of the base layer 51 is 3 to 15 mg / m 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 of

[0093] The lubricant present on the surface of the base layer 51 may be a lubricant exuded from the resin that constitutes the base layer 51, or a lubricant applied to the surface of the base layer 51.

[0094] The thickness of the substrate layer 51 is not particularly limited as long as it functions as a substrate, but may be, for example, about 3 μm or more, preferably about 10 μm or more. The thickness of the substrate layer 51 may be, for example, about 50 μm or less, preferably about 35 μm or less, about 11 μm or less, or about 8 μm or less. The thickness of the substrate layer 51 is preferably 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, or about 10 to 35 μm. For reducing the weight and thickness of the electricity storage device, thicknesses of about 3 to 35 μm, about 3 to 11 μm, or about 3 to 8 μm are preferred. For improving conformability, thicknesses of about 35 to 50 μm are preferred. When the substrate layer 51 is a laminate of two or more resin films, the thickness of each of the resin films constituting each layer is not particularly limited, but may be, for example, about 2 μm or more, preferably about 10 μm or more, or about 18 μm or more. The thickness of the resin film constituting each layer is, for example, about 33 μm or less, preferably about 28 μm or less, about 23 μm or less, about 18 μm or less, about 11 μm or less, or about 8 μm or less. Preferred ranges for the thickness of the resin film constituting each layer include about 2 to 33 μm, about 2 to 28 μm, about 2 to 23 μm, about 2 to 18 μm, about 2 to 11 μm, about 2 to 8 μm, about 10 to 33 μm, about 10 to 28 μm, about 10 to 23 μm, about 10 to 18 μm, about 10 to 11 μm, about 18 to 33 μm, about 18 to 28 μm, and about 18 to 23 μm.

[0095] [Adhesive layer 54] In the exterior film of the present disclosure, the adhesive layer 54 is a layer that is provided between the base material layer 51 and the barrier layer 52 as needed for the purpose of increasing the adhesion between them.

[0096] The adhesive layer 54 is formed of an adhesive capable of bonding the base material layer 51 and the barrier layer 52 together. There are no limitations on the adhesive used to form the adhesive layer 54, and it may be any of a chemical reaction type, a solvent volatilization type, a hot melt type, a hot pressure type, etc. It may also be a two-component curing adhesive (two-component adhesive), a one-component curing adhesive (one-component adhesive), or a resin that does not involve a curing reaction. The adhesive layer 54 may be a single layer or multiple layers.

[0097] Specific examples of adhesive components contained in the adhesive include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymer polyesters; polyethers; polyurethanes; epoxy resins; phenolic resins; polyamides such as nylon 6, nylon 66, nylon 12, and copolymer polyamides; polyolefin-based resins such as polyolefins, cyclic polyolefins, acid-modified polyolefins, and acid-modified cyclic polyolefins; polyvinyl acetate; cellulose; (meth)acrylic resins; polyimides; polycarbonates; amino resins such as urea resins and melamine resins; rubbers such as chloroprene rubber, nitrile rubber, and styrene-butadiene rubber; and silicone resins. These adhesive components may be used alone or in combination. Among these adhesive components, polyurethane adhesives are preferred. Furthermore, the adhesive strength of these adhesive component resins can be increased by using an appropriate curing agent in combination. The curing agent is selected appropriately from polyisocyanates, multifunctional epoxy resins, oxazoline group-containing polymers, polyamine resins, acid anhydrides, and the like, depending on the functional groups of the adhesive components.

[0098] Examples of polyurethane adhesives include polyurethane adhesives containing a first part containing a polyol compound and a second part containing an isocyanate compound. Preferred examples include two-component curing polyurethane adhesives, with a polyol such as polyester polyol, polyether polyol, or acrylic polyol as the first part and an aromatic or aliphatic polyisocyanate as the second part. Examples of polyurethane adhesives include polyurethane adhesives containing a polyurethane compound obtained by reacting a polyol compound with an isocyanate compound in advance, and an isocyanate compound. Examples of polyurethane adhesives include polyurethane adhesives containing a polyurethane compound obtained by reacting a polyol compound with an isocyanate compound in advance, and a polyol compound. Examples of polyurethane adhesives include polyurethane adhesives obtained by reacting a polyurethane compound obtained by reacting a polyol compound with an isocyanate compound in advance with moisture, such as in the air, and curing the polyurethane compound. Polyol compounds preferably include polyester polyols having hydroxyl groups on the side chains in addition to terminal hydroxyl groups in the repeating units. Examples of the second part include aliphatic, alicyclic, aromatic, and araliphatic isocyanate compounds. Examples of isocyanate compounds include hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), hydrogenated XDI (H6XDI), hydrogenated MDI (H12MDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and naphthalene diisocyanate (NDI). Examples of polyisocyanate compounds include polyfunctional isocyanate-modified compounds of one or more of these diisocyanates. Multimers (e.g., trimers) can also be used as polyisocyanate compounds. Examples of such multimers include adducts, biurets, and nurates. Forming the adhesive layer 54 using a polyurethane adhesive provides the exterior film with excellent electrolyte resistance, preventing peeling of the base layer 51 even when the side surface is exposed to electrolyte.

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

[0100] The type of pigment is not particularly limited as long as it does not impair the adhesiveness of the adhesive layer 54. Examples of organic pigments include azo-based, phthalocyanine-based, quinacridone-based, anthraquinone-based, dioxazine-based, indigothioindigo-based, perinone-perylene-based, isoindolenine-based, and benzimidazolone-based pigments, while examples of inorganic pigments include carbon black-based, titanium oxide-based, cadmium-based, lead-based, chromium oxide-based, and iron-based pigments, and other examples include finely powdered mica and fish scale foil.

[0101] Among colorants, carbon black is preferred in order to give the exterior film a black appearance, and mica is preferred from the viewpoint of dissipating heat generated from the electricity storage device.

[0102] The average particle size of the pigment is not particularly limited and may be, for example, about 0.05 to 5 μm, and preferably about 0.08 to 2 μm. The average particle size of the pigment is the median size measured with a laser diffraction / scattering particle size distribution measuring device.

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

[0104] The thickness of adhesive layer 54 is not particularly limited as long as it can bond base layer 51 and barrier layer 52 together, but is, for example, about 1 μm or more, or about 2 μm or more. Also, the thickness of adhesive layer 54 is, for example, about 10 μm or less, or about 5 μm or less. Examples of preferable ranges for the thickness of 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 (not shown) that is provided between the base material layer 51 and the barrier layer 52 as needed. When the adhesive layer 54 is provided, a colored layer may be provided between the base material layer 51 and the adhesive layer 54, or between the adhesive layer 54 and the barrier layer 52. Alternatively, a colored layer may be provided on the outside of the base material layer 51. By providing a colored layer, the exterior film can be colored.

[0106] The colored layer can be formed, for example, by applying ink containing a colorant to the surface of the base layer 51 or the surface of the barrier layer 52. Known colorants such as pigments and dyes can be used as the colorant. Furthermore, only one type of colorant may be used, or two or more types may be mixed together.

[0107] Specific examples of the coloring agent contained in the colored layer include the same as those exemplified in the section [Adhesive layer 54].

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

[0109] Examples of the barrier layer 52 include metal foils, vapor-deposited films, and resin layers having barrier properties. Vapor-deposited films include metal vapor-deposited films, inorganic oxide vapor-deposited films, and carbon-containing inorganic oxide vapor-deposited films. Resin layers include fluorine-containing resins such as polyvinylidene chloride, polymers mainly composed of 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. Other examples of the barrier layer 52 include resin films having at least one of these vapor-deposited films and resin layers. The barrier layer 52 may include multiple layers. The barrier layer 52 preferably includes a layer made of a metal material. Specific examples of metal materials constituting the barrier layer 52 include aluminum, aluminum alloys, titanium, titanium alloys, steel (including stainless steel), copper, copper alloys, nickel, nickel alloys, magnesium, magnesium alloys, niobium, and iron. Of these, aluminum alloys, stainless steel, titanium steel, and steel 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 made of the aforementioned metallic material may contain recycled metallic material. Examples of recycled metallic material include recycled aluminum alloy, stainless steel, titanium steel, and steel plate. These recycled materials can be obtained by known methods. Recycled aluminum alloy material can be obtained, for example, by the manufacturing method described in International Publication No. 2022 / 092231. The barrier layer 52 may be made solely of recycled material or a mixture of recycled and virgin material. Note that recycled metallic material refers to metallic material that has been made reusable by collecting, isolating, and refining various products used in the market or waste from manufacturing processes. Furthermore, virgin metallic material refers to new metallic material refined from natural metallic resources (raw materials) and is not recycled material.

[0111] From the viewpoint of improving the conformability when wrapping the exterior film around the electrode body, the aluminum alloy foil is preferably a soft aluminum alloy foil made of, for example, an annealed aluminum alloy, and from the viewpoint of further improving the conformability, an iron-containing aluminum alloy foil is preferable. In the iron-containing aluminum alloy foil (100% by mass), the iron content is preferably 0.1 to 9.0% by mass, more preferably 0.5 to 2.0% by mass. By setting the iron content to 0.1% by mass or more, an exterior film with better conformability can be obtained. By setting the iron content to 9.0% by mass or less, an exterior film with better flexibility can be obtained. Examples of soft aluminum alloy foils include aluminum alloy foils having a composition 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 be added as needed. Softening can be achieved by annealing or other methods.

[0112] From the viewpoint of improving the mechanical strength of the packaging film 50, the aluminum alloy foil is preferably a hard aluminum alloy foil made of, for example, a work-hardened aluminum alloy. Examples of hard aluminum alloy foils include aluminum alloy foils having a composition 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 packaging film 50, the aluminum alloy foil is preferably an aluminum alloy foil containing magnesium. In the aluminum alloy foil containing magnesium (100% by mass), the magnesium content is preferably 0.2 to 5.6% by mass, and more preferably 0.2 to 3.0% by mass. Examples of aluminum alloy foils containing magnesium include aluminum alloy foils having compositions defined in JIS H4000:2017 A5005P-O, JIS H4000:2017 A5050P-O, and JISH4000:2017 A5052P-O. Furthermore, from the viewpoint of improving the mechanical strength of the packaging film 50, the aluminum alloy foil is preferably an aluminum alloy foil containing manganese. In the aluminum alloy foil containing manganese (100% by mass), the manganese content is preferably 0.3 to 1.5% by mass, and more preferably 1.0 to 1.5% by mass. Examples of aluminum alloy foils containing manganese include aluminum alloy foils having compositions specified in JIS H4000:2017 A3003P-O, JIS H4000:2017 A3103P-O, JISH4000:2017 A3004P-O, and JISH4000:2017 A3104P-O.

[0113] Examples of stainless steel foil include austenitic, ferritic, austenitic-ferritic, martensitic, and precipitation hardened stainless steel foils. From the viewpoint of providing an exterior film with excellent conformability, the stainless steel foil is preferably made of austenitic stainless steel.

[0114] Specific examples of austenitic stainless steels that can be used to form the stainless steel foil include SUS304, SUS301, and SUS316L, with SUS304 being particularly preferred.

[0115] In the case of a metal foil, the thickness of the barrier layer 52 should be sufficient to at least function as a barrier layer that prevents moisture penetration, and may be, 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, still more preferably about 100 μm or less, and particularly preferably about 90 μm or less. The thickness of the barrier layer 52 is preferably about 10 μm or more, more preferably about 20 μm or more, and more preferably about 25 μm or more. Furthermore, preferred ranges for the thickness of the barrier layer 52 include approximately 9 to 200 μm, approximately 9 to 150 μm, approximately 9 to 120 μm, approximately 9 to 100 μm, approximately 9 to 90 μm, approximately 10 to 200 μm, approximately 10 to 150 μm, approximately 10 to 120 μm, approximately 10 to 100 μm, approximately 10 to 90 μm, approximately 20 to 200 μm, approximately 20 to 150 μm, approximately 20 to 120 μm, approximately 20 to 100 μm, approximately 20 to 90 μm, approximately 25 to 200 μm, approximately 25 to 150 μm, approximately 25 to 120 μm, approximately 25 to 100 μm, and approximately 25 to 90 μm. When the barrier layer 52 is made of an aluminum alloy foil, from the viewpoint of imparting high conformability and high rigidity to the exterior film 50, the thickness of the barrier layer 52 is preferably about 40 μm or more, more preferably about 60 μm or more, even more preferably about 70 μm or more, and even more preferably about 80 μm or more, and is preferably about 200 μm or less, more preferably about 150 μm or less, even more preferably about 120 μm or less, even more preferably about 100 μm or less, and even more preferably about 90 μm or less. The thickness ranges are about 40 to 200 μm, about 40 to 150 μm, about 40 to 120 μm, about 40 to 100 μm, about 40 to 90 μm, about 60 to 200 μm, about 60 to 150 μm, about 60 to 120 μm, about 60 to 100 μm, about 60 to 90 μm, about 70 to 200 μm, about 70 to 150 μm, about 70 to 120 μm, about 70 to 100 μm, about 70 to 90 μm, about 80 to 200 μm, about 80 to 150 μm, about 80 to 120 μm, about 80 to 100 μm, and about 80 to 90 μm. The high conformability of the exterior film 50 can contribute to increasing the capacity of the electricity storage device.Furthermore, although increasing the capacity of an electricity storage device increases the weight of the electricity storage device, increasing the rigidity of the exterior film 50 contributes to high sealing performance of the electricity storage device. In particular, when the barrier layer 52 is made of stainless steel foil, the thickness of the stainless steel foil is preferably 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 particularly preferably about 50 μm or less. The thickness of the stainless steel foil is preferably about 10 μm or more, more preferably about 15 μm or more. Preferred thickness ranges for 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, when the barrier layer 52 is a metal foil, it is preferable that a corrosion-resistant coating be provided on at least the surface opposite the substrate layer to prevent dissolution and corrosion. The barrier layer 52 may be provided with a corrosion-resistant coating on both sides. Here, the corrosion-resistant coating refers to a thin film that is provided with corrosion resistance (e.g., acid resistance, alkali resistance, etc.) by applying, for example, a hydrothermal conversion treatment such as boehmite treatment, a chemical conversion treatment, an anodizing treatment, a nickel or chromium plating treatment, or a corrosion prevention treatment such as applying a coating agent to the surface of the barrier layer. Specifically, the corrosion-resistant coating refers to a coating that improves the acid resistance of the barrier layer (acid-resistant coating) or a coating that improves the alkali resistance of the barrier layer (alkali-resistant coating). The corrosion-resistant coating may be formed by one type of treatment or a combination of two or more types. Furthermore, not only one layer but also multiple layers can be formed. Furthermore, among these treatments, the hydrothermal conversion treatment and anodizing treatment are treatments that dissolve the metal foil surface with a treatment agent to form a metal compound with excellent corrosion resistance. These treatments may be included in the definition of chemical conversion treatment. In addition, when the barrier layer 52 is provided with a corrosion-resistant coating, the barrier layer 52 includes the corrosion-resistant coating.

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

[0118] Various corrosion-resistant coatings formed by chemical conversion treatments are known, including corrosion-resistant coatings containing at least one of phosphates, chromates, fluorides, triazine thiol compounds, and rare earth oxides. Examples of chemical conversion treatments using phosphates and chromates include chromate chromate treatment, phosphate chromate treatment, phosphate-chromate treatment, and chromate treatment. Examples of chromium compounds used in these treatments include chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium biphosphate, chromate acetylacetate, chromium chloride, and potassium chromium sulfate. Examples of phosphorus compounds used in these treatments include sodium phosphate, potassium phosphate, ammonium phosphate, and polyphosphoric acid. Examples of chromate treatments include etching chromate treatment, electrolytic chromate treatment, and paint-on chromate treatment, with paint-on chromate treatment being preferred. This paint-type chromate treatment involves first degreasing at least the inner surface of a barrier layer (e.g., an aluminum alloy foil) using a well-known method such as alkali immersion, electrolytic cleaning, acid pickling, electrolytic pickling, or acid activation, and then coating the degreased surface with a treatment solution primarily composed of a metal phosphate such as Cr (chromium) phosphate, Ti (titanium) phosphate, Zr (zirconium) phosphate, or Zn (zinc) phosphate, or a mixture of these metal salts, or a treatment solution primarily composed of a nonmetallic phosphate and a mixture of these nonmetallic salts, or a mixture of these with a synthetic resin, using a well-known coating method such as roll coating, gravure printing, or immersion, followed by drying. The treatment solution can be, for example, water, alcoholic solvents, hydrocarbon solvents, ketone solvents, ester solvents, or ether solvents, with water being preferred. The resin component used here may be a polymer such as a phenolic resin or an acrylic resin, or may be a chromate treatment using an aminated phenol polymer having repeating units represented by the following general formulas (1) to (4): In the aminated phenol polymer, the repeating units represented by the following general formulas (1) to (4) may be contained alone or in any combination of two or more types.The acrylic resin is preferably polyacrylic acid, an acrylic acid methacrylic acid ester copolymer, an acrylic acid maleic acid copolymer, an acrylic acid styrene copolymer, or a derivative thereof such as a sodium salt, an ammonium salt, or an amine salt. A derivative of polyacrylic acid, such as an ammonium salt, a sodium salt, or an amine salt of polyacrylic acid, is particularly preferred. In the present disclosure, polyacrylic acid refers to a polymer of acrylic acid. The acrylic resin is also preferably a copolymer of acrylic acid and a dicarboxylic acid or a dicarboxylic acid anhydride, or an ammonium salt, a sodium salt, or an amine salt of a copolymer of acrylic acid and a dicarboxylic acid or a dicarboxylic acid anhydride. Only one type of acrylic resin may be used, or two or more types may be mixed and used.

[0119] [ka]

[0120] [ka]

[0121] [ka]

[0122] [ka]

[0123] In the general formulas (1) to (4), X represents a hydrogen atom, a hydroxy group, an alkyl group, a hydroxyalkyl group, an allyl group, or a benzyl group. 1 and R 2 are the same or different and represent a hydroxy group, an alkyl group, or a hydroxyalkyl group. 1 and R 2Examples of the alkyl group represented by X and R 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. 1 and R 2 Examples of the hydroxyalkyl group represented by the formula (1) include a linear or branched alkyl group having 1 to 4 carbon atoms substituted with one hydroxy group, such as a hydroxymethyl group, a 1-hydroxyethyl group, a 2-hydroxyethyl group, a 1-hydroxypropyl group, a 2-hydroxypropyl group, a 3-hydroxypropyl group, a 1-hydroxybutyl group, a 2-hydroxybutyl group, a 3-hydroxybutyl group, and a 4-hydroxybutyl group. 1 and R 2 The alkyl group and hydroxyalkyl group represented by the formula (1) may be the same or different. In the formulas (1) to (4), X is preferably a hydrogen atom, a hydroxy group, or a hydroxyalkyl group. The number average molecular weight of the aminated phenol polymer having repeating units represented by the formulas (1) to (4) is preferably about 500 to 1,000,000, and more preferably about 1,000 to 20,000. The aminated phenol polymer can be prepared, for example, by polycondensing a phenol compound or a naphthol compound with formaldehyde to produce a polymer comprising repeating units represented by the formula (1) or (3), and then polycondensing the polymer with formaldehyde and an amine (R 1 R 2 NH) to the functional group (-CHNR 1 R 2 The aminated phenol polymers can be used singly or in combination of two or more.

[0124] Another example of a corrosion-resistant coating is a thin film formed by a coating-type corrosion prevention treatment in which a coating agent containing at least one selected from the group consisting of a rare earth element oxide sol, an anionic polymer, and a cationic polymer is applied. The coating agent may further contain phosphoric acid or a phosphate salt, and a crosslinking agent for crosslinking the polymer. The rare earth element oxide sol has rare earth element oxide fine particles (e.g., particles with an average particle size of 100 nm or less) dispersed in a liquid dispersion medium. Examples of rare earth element oxides include cerium oxide, yttrium oxide, neodymium oxide, and lanthanum oxide, with cerium oxide being preferred from the perspective of further improving adhesion. The rare earth element oxide contained in the corrosion-resistant coating can be used alone or in combination of two or more. The liquid dispersion medium for the rare earth element oxide sol can be various solvents such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester-based solvents, and ether-based solvents, with water being preferred. Preferred examples of cationic polymers include polyethyleneimine, ionic polymer complexes composed of polyethyleneimine and a polymer having a carboxylic acid, primary amine-grafted acrylic resins in which a primary amine is graft-polymerized onto an acrylic backbone, polyallylamine or its derivatives, and aminated phenols. Preferred anionic polymers are poly(meth)acrylic acid or its salts, or copolymers primarily composed of (meth)acrylic acid or its salts. The crosslinking agent is preferably at least one selected from the group consisting of a compound having a functional group selected from an isocyanate group, a glycidyl group, a carboxyl group, and an oxazoline group, and a silane coupling agent. The phosphoric acid or phosphoric acid salt is preferably a condensed phosphoric acid or a condensed phosphate salt.

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

[0126] The corrosion-resistant coating may have a laminated structure, if necessary, by further laminating at least one of a cationic polymer and an anionic polymer, such as those mentioned above.

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

[0128] The amount of the corrosion-resistant film formed on the surface of the barrier layer 52 in the chemical conversion treatment is not particularly limited. For example, in the case of applying chromate treatment, the amount of the corrosion-resistant film formed on the surface of the barrier layer 52 is 2 It is desirable that the chromate compound is contained in an amount, in terms of chromium, of about 0.5 to 50 mg, preferably about 1.0 to 40 mg, the phosphorus compound in terms of phosphorus, and the aminated phenol polymer in an amount, in terms of phosphorus, of about 1.0 to 200 mg, preferably about 5.0 to 150 mg, per unit area.

[0129] The thickness of the corrosion-resistant coating is not particularly limited, but is preferably about 1 nm to 20 μm, more preferably about 1 nm to 100 nm, and even more preferably about 1 nm to 50 nm, from the viewpoint of the cohesive strength of the coating and the adhesive strength with the barrier layer or the thermally adhesive resin layer. The thickness of the corrosion-resistant coating can be measured by observation with a transmission electron microscope, or by a combination of observation with a transmission electron microscope and energy dispersive X-ray spectroscopy or electron energy loss spectroscopy. Analysis of the composition of the corrosion-resistant coating using time-of-flight secondary ion mass spectrometry can reveal the thickness of the corrosion-resistant coating, for example, by measuring the thickness of the coating with secondary ions consisting of Ce, P, and O (e.g., Ce2PO4 + , CePO4 - At least one of the following ions may be present: Cr, P, and O secondary ions (e.g., CrPO2 + , CrPO4 - Peaks derived from at least one of the above are detected.

[0130] The chemical conversion treatment is carried out by applying a solution containing a compound used to form a corrosion-resistant coating to the surface of the barrier layer by bar coating, roll coating, gravure coating, immersion, or other methods, and then heating the barrier layer to a temperature of approximately 70 to 200°C. Furthermore, before applying the chemical conversion treatment to the barrier layer, the barrier layer may be subjected to a degreasing treatment using an alkali immersion method, electrolytic cleaning, acid cleaning, electrolytic acid cleaning, or other methods. By performing such a degreasing treatment, the chemical conversion treatment of the surface of the barrier layer can be carried out more efficiently. Furthermore, using an acid degreasing agent prepared by dissolving a fluorine-containing compound in an inorganic acid for the degreasing treatment not only degreases the metal foil but also forms a passive metal fluoride. In such cases, only the degreasing treatment may be performed.

[0131] [Thermal adhesive resin layer 53] In the exterior film of the present disclosure, the heat-sealable resin layer 53 corresponds to the innermost layer, and is a layer (sealant layer) that performs the function of sealing the electrode body 20 by heat sealing when assembling the electricity storage device.

[0132] The resin constituting the heat-sealable resin layer 53 is not particularly limited as long as it is heat-sealable, but resins containing a polyolefin skeleton, such as polyolefin and acid-modified polyolefin, are preferred. The presence of a polyolefin skeleton in the resin constituting the heat-sealable resin layer 53 can be determined by, for example, infrared spectroscopy, gas chromatography mass spectrometry, or the like. Furthermore, when the resin constituting the heat-sealable resin layer 53 is analyzed by infrared spectroscopy, a peak derived from maleic anhydride is preferably detected. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, a peak derived from maleic anhydride is detected at a wavenumber of 1760 cm. -1 Near and wave number 1780cm -1 A peak derived from maleic anhydride is detected around . When the thermal adhesive resin layer 53 is a layer made of maleic anhydride-modified polyolefin, a peak derived from maleic anhydride is detected when measured by infrared spectroscopy. However, if the degree of acid modification is low, the peak becomes small and may not be detected. In such cases, analysis can be performed by nuclear magnetic resonance spectroscopy.

[0133] The thermally adhesive resin layer 53 preferably contains a resin having a polyolefin skeleton as a main component, more preferably a polyolefin as a main component, and even more preferably polypropylene as a main component. Here, "main component" refers to a resin component whose content of the resin components contained in the thermally adhesive resin layer 53 is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more. For example, "the thermally adhesive resin layer 53 contains polypropylene as a main component" refers to a resin component whose content of polypropylene of the resin components contained in the thermally adhesive 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] Specific examples of polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); propylene-α-olefin copolymers; and ethylene-butene-propylene terpolymers. Among these, polypropylene is preferred. When the polyolefin resin is a copolymer, it may be a block copolymer or a random copolymer. These polyolefin resins may be used alone or in combination of two or more.

[0135] The polyolefin may also be a cyclic polyolefin. Cyclic polyolefins are copolymers of olefins and cyclic monomers, and examples of olefins constituting the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, styrene, butadiene, and isoprene. Examples of cyclic monomers constituting the cyclic polyolefin include cyclic alkenes such as norbornene; and cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these, preferred are cyclic alkenes, and more preferred are norbornene.

[0136] The polyolefin may also 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. Examples of the acid-modified polyolefin include the above-mentioned polyolefins, copolymers of the above-mentioned polyolefins with polar molecules such as acrylic acid or methacrylic acid, and polymers such as crosslinked polyolefins. Examples of the acid component used for acid modification include carboxylic acids or anhydrides thereof, such as maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

[0137] The acid-modified polyolefin may be an acid-modified cyclic polyolefin. The acid-modified cyclic polyolefin is a polymer obtained by copolymerizing a part of the monomers constituting the cyclic polyolefin by replacing it with an acid component, or by block polymerizing or graft polymerizing an acid component onto the cyclic polyolefin. The acid-modified cyclic polyolefin is the same as described above. The acid component used for the acid modification is the same as the acid component used for the modification of the polyolefin.

[0138] Preferred acid-modified polyolefins include polyolefins modified with carboxylic acid or its anhydride, polypropylenes modified with carboxylic acid or its anhydride, maleic anhydride-modified polyolefins, and maleic anhydride-modified polypropylenes.

[0139] The thermally adhesive resin layer 53 may be formed of one type of resin alone or a blend polymer of two or more types of resins. Furthermore, the thermally adhesive resin layer 53 may be formed of only one layer, or may be formed of two or more layers of the same or different resins.

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

[0141] Furthermore, the heat-sealable resin layer 53 may contain a lubricant or the like, if necessary. When the heat-sealable resin layer 53 contains a lubricant, the followability when wrapping the exterior 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 preferably an amide-based lubricant is used. Specific examples of the lubricant include those exemplified for the base layer 51. The lubricant may be used alone or in combination of two or more types, and a combination of two or more types is preferred.

[0143] In the present disclosure, from the viewpoint of improving the conformability of the exterior film when it is wrapped around the electrode assembly, it is preferable that a lubricant be present on at least one of the surface and the interior of the heat-sealable resin layer 53. The lubricant is not particularly limited, but preferably an amide-based lubricant is used. Specific examples of amide-based lubricants include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides. Specific examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Specific examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Specific examples of substituted amides include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, and N-stearyl erucic acid amide. Specific examples of methylolamides include methylol stearic acid amide. Specific examples of saturated fatty acid bisamides include methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene hydroxystearic acid amide, N,N'-distearyl adipamide, and N,N'-distearyl sebacic acid amide. Specific examples of unsaturated fatty acid bisamides include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipamide, and N,N'-dioleyl sebacic acid amide. Specific examples of fatty acid ester amides include stearamidoethyl stearate. Specific examples of aromatic bisamides include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, and N,N'-distearylisophthalic acid amide.The lubricant may be used alone or in combination of two or more kinds, and it is preferable to use a combination of two or more kinds.

[0144] When a lubricant is present on the surface of the heat-sealable resin layer 53, the amount of the lubricant is not particularly limited. However, from the viewpoint of improving the conformability of the exterior film, it is preferably about 1 mg / m 2 or more, more preferably about 3 mg / m 2 or more, more preferably about 5 mg / m 2 or more, more preferably about 10 mg / m 2 or more, more preferably about 15 mg / m 2 or more, and preferably about 50 mg / m 2 or less, more preferably about 40 mg / m 2 The preferred range is 1 to 50 mg / m 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 of

[0145] When a lubricant is present inside the heat-sealable resin layer 53, the amount thereof is not particularly limited, but from the viewpoint of improving the conformability of the exterior film, it is preferably about 100 ppm or more, more preferably about 300 ppm or more, even more preferably about 500 ppm or more, and is preferably about 3000 ppm or less, more preferably about 2000 ppm or less, and preferred ranges include about 100 to 3000 ppm, about 100 to 2000 ppm, about 300 to 3000 ppm, about 300 to 2000 ppm, about 500 to 3000 ppm, and about 500 to 2000 ppm. When two or more types of lubricants are present inside the heat-sealable resin layer 53, the above amount of lubricant is the total amount of lubricant. Furthermore, when two or more types of lubricants are present inside the heat-sealable resin layer 53, the amount of the first type of lubricant present is not particularly limited, but from the viewpoint of improving the conformability of the exterior film, it is preferably about 100 ppm or more, more preferably about 300 ppm or more, even more preferably about 500 ppm or more, and is preferably about 3000 ppm or less, more preferably about 2000 ppm or less, and preferred ranges include about 100 to 3000 ppm, about 100 to 2000 ppm, about 300 to 3000 ppm, about 300 to 2000 ppm, about 500 to 3000 ppm, and about 500 to 2000 ppm. The amount of the second type of lubricant is not particularly limited, but from the viewpoint of improving the conformability of the exterior film, it is preferably about 50 ppm or more, more preferably about 100 ppm or more, and even more preferably about 200 ppm or more, and is preferably about 1500 ppm or less, more preferably about 1000 ppm or less, and 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-sealable resin layer 53 may be a lubricant exuded from the resin constituting the heat-sealable resin layer 53, or a lubricant applied to the surface of the heat-sealable resin layer 53.

[0147] The thickness of the heat-sealable resin layer 53 is not particularly limited as long as it functions to seal the electrode body by heat-sealing the heat-sealable resin layers together, but may be, for example, about 100 μm or less, preferably about 85 μm or less, and more preferably about 15 to 85 μm. Note that, for example, when the thickness of the adhesive layer 55 described below is 10 μm or more, the thickness of the heat-sealable resin layer 53 is preferably about 85 μm or less, and more preferably about 15 to 45 μm. For example, when the thickness of the adhesive layer 55 described below is less than 10 μm or when the adhesive layer 55 is not provided, the thickness of the heat-sealable resin layer 53 is preferably about 20 μm or more, and more preferably about 35 to 85 μm.

[0148] [Adhesive layer 55] In the exterior film of the present disclosure, the adhesive layer 55 is a layer that is provided as needed between the barrier layer 52 (or corrosion-resistant coating) and the heat-sealable 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-sealable resin layer 53. As the resin used to form the adhesive layer 55, for example, the same adhesive as exemplified for the adhesive layer 54 can be used.

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

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

[0152] The inclusion of a polyolefin skeleton in the resin constituting the adhesive layer 55 can be determined by, for example, infrared spectroscopy, gas chromatography mass spectrometry, or the like, and the analysis method is not particularly limited. Furthermore, the inclusion of an acid-modified polyolefin in the resin constituting the adhesive layer 55 can be determined by, for example, measuring a maleic anhydride-modified polyolefin by infrared spectroscopy, and finding a peak at a wave number of 1760 cm. -1 Near and wave number 1780cm -1 A peak derived from maleic anhydride is detected around this point. However, if the degree of acid modification is low, the peak may be small and not be detected. In this case, analysis can be performed using nuclear magnetic resonance spectroscopy.

[0153] Furthermore, from the viewpoint of ensuring durability such as heat resistance and resistance to contents of the exterior film, and of ensuring conformability while reducing the thickness, 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. Preferred examples of the acid-modified polyolefin include those mentioned above.

[0154] The adhesive layer 55 is preferably a cured product of a resin composition containing an acid-modified polyolefin and at least one selected from the group consisting of a compound having an isocyanate group, a compound having an oxazoline group, and a compound having an epoxy group. The adhesive layer 55 is particularly preferably a cured product of a resin composition containing an acid-modified polyolefin and at least one selected from the group consisting of a compound having an isocyanate group and a compound having an epoxy group. The adhesive layer 55 preferably contains at least one selected from the group consisting of polyurethane, polyester, and epoxy resin, and more preferably contains polyurethane and epoxy resin. Examples of polyesters include ester resins formed by the reaction of epoxy groups with maleic anhydride groups, and amide ester resins formed by the reaction of oxazoline groups with maleic anhydride groups. If unreacted components of a curing agent, such as a compound having an isocyanate group, a compound having an oxazoline group, or an epoxy resin, remain in the adhesive layer 55, the presence of the unreacted components can be confirmed by a method selected from the group consisting of infrared spectroscopy, Raman spectroscopy, time-of-flight secondary ion mass spectrometry (TOF-SIMS), and the like.

[0155] Furthermore, from the viewpoint of further enhancing the adhesion between the barrier layer 52 and the adhesive layer 55, the adhesive layer 55 is preferably a cured product of a resin composition containing a curing agent having at least one selected from the group consisting of an oxygen atom, a heterocycle, a C═N bond, and a COC bond. Examples of curing agents having a heterocycle include curing agents having an oxazoline group and curing agents having an epoxy group. Examples of curing agents having a C═N bond include curing agents having an oxazoline group and curing agents having an isocyanate group. Examples of curing agents having a COC bond include curing agents having an oxazoline group and curing agents having an epoxy group. Whether the adhesive layer 55 is a cured product of a resin composition containing such a curing agent can be confirmed by, for example, gas chromatography mass spectrometry (GCMS), infrared spectroscopy (IR), time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), or other methods.

[0156] The compound having an isocyanate group is not particularly limited, but from the viewpoint of effectively increasing the adhesion between the barrier layer 52 and the adhesive layer 55, a polyfunctional isocyanate compound is preferably used. 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), polymers or nurates thereof, mixtures of these, and copolymers with other polymers. Other examples include adducts, biurets, and isocyanurates.

[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 mass %, and more preferably in the range of 0.5 to 40 mass %, of the resin composition constituting the adhesive layer 55. This can effectively improve the adhesion between the barrier layer 52 and the adhesive layer 55.

[0158] The compound having an oxazoline group is not particularly limited as long as it is a compound having an oxazoline skeleton. Specific examples of the compound having an oxazoline group include those having a polystyrene main chain and those having an acrylic main chain. Examples of commercially available products 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 mass %, and more preferably in the range of 0.5 to 40 mass %, of the resin composition constituting the adhesive layer 55. This makes it possible to effectively improve the adhesion between the barrier layer 52 and the adhesive layer 55.

[0160] An example of a compound having an epoxy group is an epoxy resin. The epoxy resin is not particularly limited as long as it is a resin capable of forming a crosslinked structure by the epoxy groups present in the molecule, and known epoxy resins can be used. The weight-average molecular weight of the epoxy resin is preferably about 50 to 2,000, more preferably about 100 to 1,000, and even more preferably about 200 to 800. In the present disclosure, the weight-average molecular weight of the epoxy resin is a value measured by gel permeation chromatography (GPC) under conditions using polystyrene as a standard sample.

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

[0162] The proportion of the epoxy resin in the adhesive layer 55 is preferably in the range of 0.1 to 50 mass %, and more preferably in the range of 0.5 to 40 mass %, of the resin composition constituting the adhesive layer 55. This makes it possible to effectively improve 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 two-component curing polyurethane.

[0164] The proportion of polyurethane in adhesive layer 55 is preferably in the range of 0.1 to 50 mass %, and more preferably in the range of 0.5 to 40 mass %, of the resin composition constituting adhesive layer 55. This effectively improves the adhesion between barrier layer 52 and adhesive layer 55 in an atmosphere containing a component that induces corrosion of the barrier layer, such as an electrolyte solution.

[0165] In addition, when the adhesive layer 55 is a cured product of a resin composition containing at least one selected from the group consisting of a compound having an isocyanate group, a compound having an oxazoline group, and an epoxy resin, and the acid-modified polyolefin, the acid-modified polyolefin functions as the main agent, and the compound having an isocyanate group, the compound having an oxazoline group, and the compound having an epoxy group each function as a curing agent.

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

[0167] From the viewpoint of more suitably exerting the effects of the present disclosure, the adhesive layer 55 is preferably formed from a resin composition containing an acid-modified polypropylene and an elastomer, and further containing at least one of block polypropylene and homopolypropylene. The resin composition may further contain random polypropylene, polyethylene, etc. Note that, from the viewpoint of improving adhesion to the barrier layer 52 and heat resistance, the adhesive layer 55 is preferably made of an acid-modified homopolypropylene (i.e., acid-modified homopolypropylene).

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

[0169] From the viewpoint of more suitably exerting the effects of the present disclosure, the elastomer content in the resin composition forming adhesive layer 55 is preferably about 25% by mass or more, more preferably about 30% by mass or more, even more preferably about 35% by mass or more, and is preferably about 60% by mass or less, more preferably about 55% by mass or less, even more preferably about 50% by mass or less, and preferred ranges include about 25 to 60% by mass, about 25 to 55% by mass, about 25 to 50% by mass, about 30 to 60% by mass, about 30 to 55% by mass, about 30 to 50% by mass, about 35 to 60% by mass, about 35 to 55% by mass, and about 35 to 50% by mass.

[0170] From the viewpoint of more suitably achieving the effects of the present disclosure, the elastomer contained in the resin composition forming the adhesive layer 55 is preferably a binary copolymer or a tertiary copolymer. The elastomer is preferably a propylene-based elastomer. Examples of the propylene-based elastomer include binary copolymers and tertiary copolymers. Examples of the binary copolymer include a propylene-ethylene copolymer elastomer and a propylene-butene copolymer elastomer, and examples of the tertiary copolymer include a propylene-ethylene-butene copolymer elastomer and an ethylene-propylene-diene copolymer elastomer. Among the elastomers, a propylene-ethylene copolymer elastomer is preferred as the binary copolymer, and a propylene-ethylene-butene copolymer elastomer is preferred as the tertiary copolymer.

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

[0172] Furthermore, from the viewpoint of more suitably exerting the effects of the present disclosure, the content of homopolypropylene in the resin composition forming adhesive layer 55 is preferably about 20% by mass or more, more preferably about 25% by mass or more, even more preferably about 30% by mass or more, and is preferably about 80% by mass or less, more preferably about 75% by mass or less, even more preferably about 70% by mass or less, and preferred ranges include about 20 to 80% by mass, about 20 to 75% by mass, about 20 to 70% by mass, about 25 to 80% by mass, about 25 to 75% by mass, about 25 to 70% by mass, about 30 to 80% by mass, about 30 to 75% by mass, and about 30 to 70% by mass.

[0173] From the viewpoint of more suitably exerting the effects of the present disclosure, the content of random polypropylene in the resin composition forming adhesive layer 55 is preferably about 0% by mass or more, more preferably about 1% by mass or more, even more preferably about 2% by mass or more, and is 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 to 30% by mass, about 0 to 25% by mass, about 0 to 20% by mass, about 1 to 30% by mass, about 1 to 25% by mass, about 1 to 20% by mass, about 2 to 30% by mass, about 2 to 25% by mass, and about 2 to 20% by mass.

[0174] From the viewpoint of more suitably exerting the effects of the present disclosure, the polyethylene content in the resin composition forming adhesive layer 55 is, for example, about 0% by mass or more, preferably about 1% by mass or more, more preferably about 2% by mass or more, and even more preferably about 3% by mass or more, and is 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 to 30% by mass, about 0 to 25% by mass, about 0 to 20% by mass, about 1 to 30% by mass, about 1 to 25% by mass, about 1 to 20% by mass, about 2 to 30% by mass, about 2 to 25% by mass, about 2 to 20% by mass, about 3 to 30% by mass, about 3 to 25% by mass, and about 3 to 20% by mass.

[0175] From the viewpoint of more suitably exerting the effects of the present disclosure, the specific composition of the resin composition is, for example, such that the content of acid-modified polypropylene is 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, and preferred ranges are about 5 to 90% by mass, about 5 to 80% by mass, about 5 to 70% by mass, about 10 to 90% by mass, about 10 to 80% by mass, about 10 to 70% by mass, about 15 to 90% by mass, about 15 to 80% by mass, about 15 to 70% by mass, etc.), and the content of elastomer is about 25% by mass or more (more preferably about 30% by mass). The content of block polypropylene is about 30% by mass or more (more preferably about 35% by mass or more), and preferably about 60% by mass or less, more preferably about 55% by mass or less, and even more preferably about 50% by mass or less. Preferred ranges include about 25 to 60% by mass, about 25 to 55% by mass, about 25 to 50% by mass, about 30 to 60% by mass, about 30 to 55% by mass, about 30 to 50% by mass, about 35 to 60% by mass, about 35 to 55% by mass, about 35 to 50% by mass, etc.), and the content of block polypropylene is about 30% by mass or more (more preferably about 35% by mass or more, even more preferably about 40% by mass or more, and 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 to 95% by mass, about 30 to 90% by mass, about 30 to 85% by mass, about 35 to 95% by mass, about 35 to 90% by mass, about 35 to 85% by mass, about 40 to 95% by mass, about 40 to 90% by mass, and about 40 to 85% by mass, and the homopolypropylene content is about 20% by mass or more (more preferably about 25% by mass or more, and even more preferably about 30% by mass or more, and is also preferably about 80% by mass or less, more preferably about 75% by mass). The content of random polypropylene is about 0% by mass or more (more preferably about 1% by mass or more, and even more preferably about 2% by mass or less), and more preferably about 70% by mass or less, and preferred ranges include about 20 to 80% by mass, about 20 to 75% by mass, about 20 to 70% by mass, about 25 to 80% by mass, about 25 to 75% by mass, about 25 to 70% by mass, about 30 to 80% by mass, about 30 to 75% by mass, and about 30 to 70% by mass). It is 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 to 30% by mass, about 0 to 25% by mass, about 0 to 20% by mass, about 1 to 30% by mass, about 1 to 25% by mass, about 1 to 20% by mass, about 2 to 30% by mass, about 2 to 25% by mass, and about 2 to 20% by mass. The polyethylene content is, for example, about 0% by mass or more (preferably about 1% by mass or more, more preferably about 2% by mass or more, and even more preferably about 20% by mass or less). It is preferably about 3% by mass or more, and preferably about 30% by mass or less, more preferably about 25% by mass or less, and even more preferably about 20% by mass or less, with preferred ranges being about 0 to 30% by mass, about 0 to 25% by mass, about 0 to 20% by mass, about 1 to 30% by mass, about 1 to 25% by mass, about 1 to 20% by mass, about 2 to 30% by mass, about 2 to 25% by mass, about 2 to 20% by mass, about 3 to 30% by mass, about 3 to 25% by mass, about 3 to 20% by mass, etc. The resin composition preferably contains, as a resin (excluding additives such as lubricants described below), an acid-modified polypropylene and an elastomer, and further contains only at least one of block polypropylene and homopolypropylene.

[0176] When manufacturing the exterior film 50 of the present disclosure by laminating the adhesive layer 55 with the barrier layer 52, the heat-sealable resin layer 53, or the like, a pre-formed resin film may be used as the adhesive layer 55. Alternatively, the heat-sealable resin that forms the adhesive layer 55 may be formed into a film on the surface of the barrier layer 52, the heat-sealable resin layer 53, or the like by extrusion molding, coating, or the like, to form the adhesive layer 55 from 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. The thickness of the adhesive layer 55 is preferably about 0.1 μm or more, or about 0.5 μm or more. The thickness of the adhesive layer 55 is preferably in the range of 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 adhesives such as those exemplified for the adhesive layer 54 or a cured product of an acid-modified polyolefin and a curing agent, the thickness is preferably about 1 to 10 μm, and more preferably about 1 to 5 μm. Furthermore, when a resin exemplified for 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. When the adhesive layer 55 is an adhesive exemplified for the adhesive layer 54 or a cured product of a resin composition containing an acid-modified polyolefin and a curing agent, the adhesive layer 55 can be formed, for example, by applying the resin composition and curing it by heating or the like. When a resin exemplified for the heat-fusible resin layer 53 is used, the heat-fusible resin layer 53 and the adhesive layer 55 can be formed, for example, by extrusion molding.

[0178] [Surface coating layer] The exterior film of the present disclosure may have a surface coating layer, if necessary, on the barrier layer 52, on the base layer 51 (on the side of the base layer 51 opposite to the barrier layer 52), or the like, if necessary, for the purpose of improving at least one of design, electrolyte resistance, scratch resistance, conformability, etc. The surface coating layer is a layer that is located on the outermost layer side of the exterior film when an electricity storage device is assembled using the exterior film.

[0179] Examples of the surface coating layer include resins such as polyvinylidene chloride, polyester, polyamide, epoxy resin, acrylic resin, fluororesin, polyurethane, silicone resin, and phenolic resin, as well as modified versions of these resins. The surface coating layer may also be a copolymer of these resins or a modified version of the copolymer. Furthermore, the surface coating layer may also 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, the resin may be either a one-component curable resin or a two-component curable resin, but is preferably a two-component curable resin. Examples of two-component curable resins include two-component curable polyurethane, two-component curable polyester, and two-component curable epoxy resin. Among these, two-component curable polyurethane is preferred.

[0181] Examples of two-component curing polyurethanes include polyurethanes containing a first component containing a polyol compound and a second component containing an isocyanate compound. Preferred examples of two-component curing polyurethanes include those containing a polyol, such as polyester polyol, polyether polyol, or acrylic polyol, as the first component and an aromatic or aliphatic polyisocyanate as the second component. Examples of polyurethanes include polyurethane compounds prepared by reacting a polyol compound with an isocyanate compound in advance, and polyurethanes containing an isocyanate compound. Examples of polyurethanes include polyurethane compounds prepared by reacting a polyol compound with an isocyanate compound in advance, and polyurethanes containing a polyol compound. Examples of polyurethanes include polyurethanes prepared by reacting a polyol compound with an isocyanate compound in advance and curing the polyurethane compound with moisture, such as in the air. Polyol compounds preferably include polyester polyols having hydroxyl groups on the side chains in addition to terminal hydroxyl groups in the repeating units. Examples of the second component include aliphatic, alicyclic, aromatic, and araliphatic isocyanate compounds. Examples of isocyanate compounds include hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), hydrogenated XDI (H6XDI), hydrogenated MDI (H12MDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and naphthalene diisocyanate (NDI). Also included are polyfunctional isocyanate-modified compounds of one or more of these diisocyanates. Furthermore, polymers (e.g., trimers) can also be used as polyisocyanate compounds. Examples of such polymers include adducts, biurets, and nurates. It should be noted that an aliphatic isocyanate compound refers to an isocyanate that has an aliphatic group but does not have an aromatic ring, an alicyclic isocyanate compound refers to an isocyanate that has an alicyclic hydrocarbon group, and an aromatic isocyanate compound refers to an isocyanate that has an aromatic ring.The surface coating layer is formed from polyurethane, which gives the exterior film excellent resistance to the electrolyte solution.

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

[0183] The additive may be either inorganic or organic. The shape of the additive is not particularly limited, and examples thereof include spherical, fibrous, plate-like, amorphous, and scaly shapes.

[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. The additives may be used alone or in combination of two or more. Among these additives, silica, barium sulfate, and titanium oxide are preferred from the viewpoints of dispersion stability and cost. Furthermore, mica is preferred from the viewpoint of heat dissipation from the power storage device. The additives may also be subjected to various surface treatments, such as insulation treatment and high-dispersibility treatment.

[0185] The method for forming the surface coating layer is not particularly limited, and examples thereof include a method of applying a resin to form the surface coating layer. When an additive is blended into the surface coating layer, a resin mixed with the additive may be applied.

[0186] In the present disclosure, from the viewpoint of improving the followability when wrapping the exterior film around the electrode assembly, it is preferable that a lubricant be present on at least one of the surface and the interior of the surface coating layer. The lubricant is not particularly limited, but preferably an amide-based lubricant is used. Specific examples of amide-based lubricants include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides. Specific examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Specific examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Specific examples of substituted amides include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, and N-stearyl erucic acid amide. Specific examples of methylolamides include methylol stearic acid amide. Specific examples of saturated fatty acid bisamides include methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene hydroxystearic acid amide, N,N'-distearyl adipamide, and N,N'-distearyl sebacic acid amide. Specific examples of unsaturated fatty acid bisamides include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipamide, and N,N'-dioleyl sebacic acid amide. Specific examples of fatty acid ester amides include stearamidoethyl stearate. Specific examples of aromatic bisamides include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, and N,N'-distearylisophthalic acid amide.The lubricant may be used alone or in combination of two or more kinds, and it is preferable to use a combination of two or more kinds.

[0187] When a lubricant is present on the surface of the surface coating layer, the amount of the lubricant is not particularly limited, but may be, for example, about 3 mg / m 2 or more, preferably about 4 mg / m 2 More than about 5mg / m 2 The amount of lubricant present on the surface of the surface coating layer is, for example, about 15 mg / m 2 or less, preferably about 14 mg / m 2 Below, about 10mg / m 2 The preferred range of the amount of lubricant present on the surface of the surface coating layer is 3 to 15 mg / m 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 of

[0188] The lubricant present on the surface of the surface coating layer may be a lubricant exuded from the resin that constitutes the surface coating layer, 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 exhibits the above-mentioned functions as a surface coating layer, and may be, for example, about 0.5 to 10 μm, and preferably about 1 to 5 μm.

[0190] <2-3. Manufacturing method of exterior film> The method for manufacturing the exterior film is not particularly limited as long as it can produce a laminate in which each layer of the exterior film of the present disclosure is laminated, and examples include methods that include at least a step of laminating a barrier layer 52 and a heat-sealable resin layer 53.

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

[0192] Next, a heat-sealable resin layer 53 is laminated on the barrier layer 52 of the laminate A. When the heat-sealable resin layer 53 is laminated directly on the barrier layer 52, the heat-sealable resin layer 53 may be laminated on the barrier layer 52 of the laminate A by a method such as thermal lamination or extrusion lamination. When an adhesive layer 55 is provided between the barrier layer 52 and the heat-sealable resin layer 53, the adhesive layer 55 and the heat-sealable resin layer 53 may be laminated by, for example, (1) extrusion lamination, (2) thermal lamination, (3) sandwich lamination, or (4) dry lamination. Examples of the (1) extrusion lamination method include a method of laminating the adhesive layer 55 and the heat-sealable resin layer 53 on the barrier layer 52 of the laminate A by extrusion (co-extrusion lamination, tandem lamination), etc. Examples of the (2) thermal lamination method include a method of separately forming a laminate in which an adhesive layer 55 and a heat-sealable resin layer 53 are laminated, and laminating this on the barrier layer 52 of the laminate A, or a method of forming a laminate in which an adhesive layer 55 is laminated on the barrier layer 52 of the laminate A, and laminating this on the heat-sealable resin layer 53. Examples of the (3) sandwich lamination method include a method of pouring a molten adhesive layer 55 between the barrier layer 52 of the laminate A and the heat-sealable resin layer 53 previously formed into a sheet, and bonding the laminate A and the heat-sealable resin layer 53 via the adhesive layer 55. Examples of the (4) dry lamination method include a method of solution-coating an adhesive for forming the adhesive layer 55 on the barrier layer 52 of the laminate A, drying the adhesive, or baking the adhesive, and laminating the heat-sealable resin layer 53 previously formed into a sheet on the 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 above-mentioned resin for forming the surface coating layer to the surface of the base layer 51. The order of the step of laminating the barrier layer 52 on the surface of the base layer 51 and the step of laminating the surface coating layer on the surface of the base layer 51 is not particularly limited. For example, after forming the surface coating layer on the surface of the base layer 51, the barrier layer 52 may be formed on the surface of the base layer 51 opposite to the surface coating layer.

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

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

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

[0197] Like the packaging film 50, the packaging material 50 for an electricity storage device according to the present disclosure is composed of a laminate including a barrier layer 3 and a heat-sealable resin layer 4, as shown in FIG. 5 . In the packaging material 50 for an electricity storage device, the barrier layer 3 is the outermost layer, and the heat-sealable resin layer 4 is the innermost layer. For example, as shown in FIGS. 10 and 11 , when assembling an electricity storage device using the packaging material 50 for an electricity storage device and electricity storage device elements (electrode body 20, electrode terminal 30, etc.), the electrode body 20 is housed in a space formed by heat-sealing the ends of the heat-sealable resin layers 4 of the packaging material 50 for an electricity storage device together with a lid 60 while the layers are facing each other. In the laminate constituting the packaging material 50 for an electricity storage device according to the present disclosure, the side of the heat-sealable resin layer 4 relative to the barrier layer 3 is the inner side, and the opposite side is the outer side, relative to the barrier layer 3.

[0198] As shown in Figs. 5 to 8, for example, the packaging material 50 for an electricity storage device may have a base material layer 1 on the outside of the barrier layer 3, if necessary. Furthermore, as shown in Figs. 6 to 8, for example, the packaging material 50 for an electricity storage device may have an adhesive layer 2 between the base material layer 1 and the barrier layer 3, if necessary, for the purpose of increasing the adhesion between these layers. Furthermore, as shown in Figs. 7 and 8, for example, the packaging material 50 may have an adhesive layer 5 between the barrier layer 3 and the heat-sealable resin layer 4, if necessary, for the purpose of increasing the adhesion between these layers. Furthermore, as shown in Fig. 8, a surface coating layer 6 or the like may be provided on the outside of the base material layer 1 (the side opposite to the heat-sealable resin layer 4), if necessary.

[0199] The thickness of the laminate constituting the electricity storage device packaging material 50 is not particularly limited, but from the viewpoint of cost reduction, improvement of energy density, etc., examples of the thickness include about 250 μm or less, preferably about 190 μm or less, about 180 μm or less, about 155 μm or less, and about 120 μm or less. Furthermore, from the viewpoint of maintaining the function of the electricity storage device packaging material 50, which is to protect the electrode assembly 20, the thickness of the laminate constituting the electricity storage device packaging material 50 is preferably about 35 μm or more, about 45 μm or more, and about 60 μm or more. Furthermore, preferred ranges for the laminate constituting the packaging material 50 for an electricity storage device include, for example, about 35 to 250 μm, about 35 to 190 μm, about 35 to 180 μm, about 35 to 155 μm, about 35 to 120 μm, about 45 to 250 μm, about 45 to 190 μm, about 45 to 180 μm, about 45 to 155 μm, about 45 to 120 μm, about 60 to 250 μm, about 60 to 190 μm, about 60 to 180 μm, about 60 to 155 μm, and about 60 to 120 μm. In particular, a thickness of about 60 to 155 μm is preferred when making the electricity storage device lighter and thinner, and about 155 to 190 μm is preferred when improving conformability.

[0200] In the packaging material 50 for an electricity storage device, the ratio of the total thickness of the base material layer 1 (optional), adhesive layer 2 (optional), barrier layer 3, adhesive layer 5 (optional), heat-sealable resin layer 4, and surface coating layer 6 (optional) to the thickness (total thickness) of the laminate constituting the packaging material 50 for an electricity storage device is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. As a specific example, when the packaging material 50 for an electricity storage device of the present disclosure includes the base material layer 1, adhesive layer 2, barrier layer 3, adhesive layer 5, and heat-sealable resin layer 4, the ratio of the total thickness of these layers to the thickness (total thickness) of the laminate constituting the packaging material 50 for an electricity storage device is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. Furthermore, even when the packaging material 50 for an electricity storage device of the present disclosure is a laminate including a base material layer 1, an adhesive layer 2, a barrier layer 3, and a heat-sealable resin layer 4, the ratio of the total thickness of these layers to the thickness (total thickness) of the laminate constituting the packaging material 50 for an electricity storage device 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 suitably exerting the effects of the present disclosure, the Young's modulus of the electrical storage device packaging material 50 is preferably 6000 MPa or more, more preferably 8000 MPa or more, and even more preferably 10000 MPa or more, and is preferably 40000 MPa or less, more preferably 35000 MPa or less, and even more preferably 30000 MPa or less, with preferred ranges being about 6000 to 40000 MPa, about 6000 to 35000 MPa, about 6000 to 30000 MPa, about 8000 to 40000 MPa, about 8000 to 35000 MPa, about 8000 to 30000 MPa, about 10000 to 40000 MPa, about 10000 to 35000 MPa, and about 10000 to 30000 MPa. In the present disclosure, the Young's modulus of the electrical storage device packaging material 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. Test piece shape: Dumbbell No. 7 Test piece width: 2 mm Test piece length: 35 mm Thickness of test piece: 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 a method for increasing the Young's modulus of the packaging material 50 for an electricity storage device, as explained for the packaging film 50, increasing the Young's modulus of the barrier layer 3 is effective.

[0204] <3-2. Layers that make up the exterior packaging for energy storage devices> As described above, in the laminate constituting the packaging material 50 for an electricity storage device of the present disclosure, the base material layer 1, adhesive layer 2, barrier layer 3, adhesive layer 5, heat-sealable resin layer 4, and surface coating layer 6 correspond to the base material layer 51, adhesive layer 54, barrier layer 52, adhesive layer 55, heat-sealable resin layer 53, and surface coating layer, respectively, of the laminate constituting the above-mentioned packaging film 50. Therefore, the explanations of the base material layer 1, adhesive layer 2, barrier layer 3, adhesive layer 5, heat-sealable resin layer 4, and surface coating layer 6 are common to the explanations of the base material layer 51, adhesive layer 54, barrier layer 52, adhesive layer 55, heat-sealable resin layer 53, and surface coating layer of the laminate constituting the above-mentioned packaging film 50, and redundant explanations will be omitted.

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

[0206] Here, the area-average crystal grain size R1 (μm) of the barrier layer 3 is the area-average crystal grain size (μm) obtained by performing crystal analysis using the EBSD method on a cross section obtained by cutting the barrier layer 3 perpendicularly from 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-sealable resin layer 4 of the packaging material 50 for an electrical storage device and the polypropylene plate are heat-sealed under conditions where the thickness of the heat-sealable resin layer is 20% to 80% or less. Note that the polypropylene plate is intended for use as a lid that constitutes an exterior package. The conditions where the thickness of the heat-sealable resin layer is 20% to 80% or less are adjusted, for example, by setting the heat-sealing temperature to about 160 to 240°C, the surface pressure to about 0.2 to 1.5 MPa, and the heat-sealing time to about 1 to 12 seconds.

[0207] The area average crystal grain size R2 (μm) of the barrier layer 3 is the area average crystal grain size (μm) obtained by performing crystal analysis using the EBSD method on a cross section obtained by cutting the barrier layer 3 vertically from 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-sealable resin layer 4 of the packaging material 50 for an electrical storage device is not heat-sealed to the polypropylene plate.

[0208] From the viewpoint of more suitably exerting the effects of the invention of the present disclosure, the ratio (R1 / R2) is preferably about 55% or more, more preferably about 60% or more, and even more preferably about 70% or more, and is preferably about 150% or less, more preferably about 140% or less, and even more preferably about 130% or less, and preferred ranges include about 55 to 150%, about 55 to 140%, about 55 to 130%, about 60 to 150%, about 60 to 140%, about 60 to 130%, about 70 to 150%, about 70 to 140%, and about 70 to 130%.

[0209] The area average crystal grain size R1 (μm) and the area average crystal grain size R2 (μm) of the barrier layer 3 are values ​​measured by the following method. When an electrical storage device packaging material is obtained from an electrical storage device (for example, an electrical storage device packaging material is obtained from an electrical storage device mounted on a driven automobile) and the area average crystal grain size R1 (μm) and the area average crystal grain size R2 (μm) of the barrier layer 3 are measured, a sample is obtained from a portion of the electrical storage device packaging material where the heat-fusible resin layer is not heat-fused, and the following measurements are performed.

[0210] <Measurement of area-average crystal grain size R1, R2 of the barrier layer> For an electricity storage device, a barrier layer was obtained at a position where the heat-sealable resin layer of the electricity storage device packaging material and a polypropylene plate (assuming a lid) were heat-sealed under conditions such that the thickness of the heat-sealable resin layer was 20% to 80%. The barrier layer was also obtained at a position where the heat-sealable resin layer of the electricity storage device packaging material was not heat-sealed (non-sealed portion). The heat-sealing conditions were set so that the ratio of "(thickness of the heat-sealable resin layer at the position where the heat-sealable resin layer is heat-sealed to the lid) / (thickness of the heat-sealable resin layer at the position where the heat-sealable resin layer is not heat-sealed to the lid)" was 20 to 80%. Specifically, the electricity storage device packaging material was cut into a rectangular shape measuring 360 mm MD x 160 mm TD. A rectangular parallelepiped (100 mm long x 30 mm wide x 5 mm thick) polypropylene lid (polypropylene plate) was prepared as the lid of the packaging material. Furthermore, a rectangular parallelepiped (140 mm long x 98 mm wide x 28 mm thick) aluminum block was prepared as a simulated electrode body. Next, as shown in the schematic diagram of FIG. 1, lids were placed on both sides of the electrode body in the longitudinal direction, and this was wrapped in an exterior material for an electricity storage device. The position where the heat-sealable resin layers of the exterior material for an electricity storage device face each other (first sealing portion 70) and the position where the heat-sealable resin layer of the exterior material for an electricity storage device and the lid body come into contact (second sealing portion 80) were heat-sealed using a heat seal bar, respectively, to obtain a simulated electricity storage device. The simulated electricity storage device did not have electrode terminals like those shown in FIG. 1. The seal width at the position where the heat-sealable resin layers of the exterior material for an electricity storage device face each other (first sealing portion 70) was 10 mm. The seal width at the position where the heat-sealable resin layer of the electrical storage device packaging material and the lid come into contact (second sealing portion 80) is set to the thickness of the lid (10 mm). The heat-sealing conditions (temperature, surface pressure, time) of second sealing portion 80 are set to conditions that reduce the thickness of the heat-sealable resin layer by 20% to 80%. Next, crystal analysis is performed using the EBSD method on the barrier layer of the obtained simulated electrical storage device to measure the area-average crystal grain sizes R1 and R2 of the barrier layer. The specific measurement method is as follows.

[0211] Crystal analysis was performed using the EBSD method on the cross section of each barrier layer perpendicular to the rolling direction, and the area-average crystal grain size of the barrier layer was measured. The details of the measurement conditions are as follows. The area-average crystal 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 crystal analysis using the EBSD method were linked together to obtain a diameter of approximately 5000 μm. 2 The area average crystal grain size of the crystals included in the measurement area is equal to or greater than 100 μm. The maximum crystal grain size is the value measured for the largest crystal among the crystals included in the measurement area, assuming that the crystal shape is circular. The standard deviation of the crystal grain size is approximately 5000 μm, obtained by combining multiple images obtained by crystal analysis using the EBSD method after removing areas with a CI value of 0.1 or less. 2 It is calculated from the distribution of the crystal grain size (diameter when the crystal area is assumed to be a circle) of the crystals contained in the measurement area (the entire thickness direction of the barrier layer is the measurement area) described above. The area average crystal grain size R2 of the barrier layer is measured at a location 3 cm away from the measurement location of the area average crystal grain size R1.

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

[0213] (Pretreatment) As a pretreatment step, the barrier layer was cut perpendicular to the rolling direction (RD) to obtain a cross section. The rolling direction of the barrier layer was determined by observing the shiny surface of the barrier layer with a metallurgical microscope, and the direction of linear rolling marks was the direction of extension. Specifically, the barrier layer sample was first cut into a 5 mm (perpendicular to the rolling direction) x 10 mm (rolling direction) piece using a trimming razor, and then embedded in resin. Next, the barrier layer and the resin were cut using the trimming razor perpendicular to the rolling direction of the barrier layer, perpendicular to the surface of the barrier layer, to expose the cross section of the barrier layer. The resulting cross section was then trimmed using a microtome. To reduce mechanical distortion in the cross section, the microtome was used to cut the embedded resin and the barrier layer perpendicular to the cross section by approximately 1 mm. Next, a broad argon beam was irradiated perpendicular to the cross section using an ion milling device under the following conditions: a protrusion width of 50 μm, a voltage of 6 kV, and 4 hours. The measurement cross section was then prepared. This is a process for precisely exposing the cross section of the barrier layer so as to minimize mechanical damage to the crystal structure that occurred in the previous process. Note that in the present disclosure, the "perpendicular direction" when cutting the aluminum alloy foil is checked under a stereomicroscope, and therefore may include an error of about 10°. That is, the permissible range for the direction perpendicular to the rolling direction is 80 to 100° to the rolling direction, and the permissible range for the direction perpendicular to the surface is 80 to 100° with respect to the surface.

[0214] (SEM conditions) The conditions of the scanning electron microscope (SEM) used for the EBSD method are as follows: Observation magnification: 2000x (the standard observation magnification when taking photos is Polaroid 545) Accelerating voltage: 15 kV 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 is carried out using the crystal orientation analysis software OIM (Ver. 7.3) manufactured by TSL Solutions Co., Ltd. Multiple images are stitched together to measure an area of ​​approximately 5000 μm 2 The upper limit of the measurement area is, for example, approximately 30,000 μm 2 In this case, the measurement area is from the center of the barrier layer in the thickness direction to both ends, and the area where resin is attached to the cross section and the area where the acid-resistant film is present are excluded from the measurement area. The CI value is 0.1 or more, the grain boundary condition is 0.5 degrees or more, and the minimum grain size is 3 steps or more. After stitching the images, check the pole figures. If the center of the pole figure is off by 10° or more, rotate the crystal data to restore symmetry. The pole figure used as reference is measured from the sample surface using XRD. When obtaining a pole figure from the surface using EBSD, the sample surface is mechanically polished, flat-milled, electrolytically polished, etc., before performing a wide-area measurement to remove the influence of the mechanical crystal structure of the sample surface. The pole figure obtained from the surface direction is then rotated 90° so that it is the same as the pole figure obtained from the same orientation as the pole figure obtained from the cross section of the target sample. Use this pole figure as a reference. The analysis is performed by excluding data with a Confidence Index (CI value) of 0.1 or less, as defined by OIM (Ver. 7.3), a crystal orientation analysis software made by TSL Solutions Co., Ltd. This makes it possible to exclude data based on the resin used in pre-processing present on the front and back of the sample, grain boundaries present on the cross section, and amorphous matter.

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

[0217] For example, by increasing the Young's modulus of the barrier layer 3 (i.e., increasing the Young's modulus of the packaging material 50 for an electricity storage device), it is possible to increase the ratio (R1 / R2) of the area average crystal grain size R1 (μm) to the area average crystal grain size R2 (μm) of the barrier layer 3. The preferred Young's modulus of the barrier layer 3 will be described later. For example, increasing the thickness of the barrier layer 3 or using a high-strength metal is effective.

[0218] Furthermore, for example, when the barrier layer 3 is formed of an aluminum alloy foil, if the aluminum alloy composition is in the JIS 8000 series, 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 JIS 5000 series, the strength of the soft foil can be increased by dissolving Mg in aluminum through solid solution strengthening.

[0219] Refining the crystal grains of the metal forming the barrier layer 3 is also effective in increasing the ratio (R1 / R2). For example, in the case of aluminum alloy compositions in the JIS 8000 and 5000 series, Al-Fe intermetallic compounds are crystallized during casting, and these act as nuclei to refine the crystal grains. Furthermore, when differential speed rolling (a method in which rolls are rolled at different peripheral speeds) is employed, the rolled material undergoes shear deformation throughout the entire thickness in addition to the normal rolling deformation. As a result, crystal rotation is promoted, accelerating the transformation of subgrain boundaries into high-angle grain boundaries, resulting in the generation of fine crystal grains. While this method is also effective in cold rolling, warm rolling is more effective. Furthermore, increasing the number of rolling passes in the hot rolling of aluminum alloy foil and increasing the final cold rolling reduction are also effective. The higher the final cold rolling reduction from the intermediate annealing to the final thickness (e.g., 80% or higher), the greater the amount of strain accumulated in the aluminum alloy foil, resulting in refined recrystallized grains after final annealing.

[0220] The rolling conditions for the aluminum foil are adjusted by adjusting the conditions such as the rolling reduction, heating temperature, heating time, etc. For example, a method including 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 in which the ingot is held at about 300 to 450 ° C for about 1 to 10 hours, a cold rolling process in which the rolling reduction from the intermediate annealing to the final rolling is 80% or more, more preferably 90% or more, and a final annealing process in which the ingot is held at about 250 to 400 ° C for about 30 to 100 hours, can be mentioned, but the conditions for refining the crystal grains are not limited to these.

[0221] <3-3. Method for manufacturing exterior materials for electricity storage devices> As described above, the packaging material 50 for an electricity storage device according to the present disclosure corresponds to the packaging film 50, and therefore the manufacturing method is also common to both, and therefore a description thereof will be omitted.

[0222] <3-4. Uses of exterior materials for energy storage devices> The exterior material for an electricity storage device according to the present disclosure is used in a package for hermetically housing an electricity storage device element such as a positive electrode, a negative electrode, and an electrolyte. That is, an electricity storage device can be formed by housing an electricity storage device element including at least a positive electrode, a negative electrode, and an electrolyte in a package formed from the exterior material for an electricity storage device according to the present disclosure. In other words, an electricity storage device can be formed by wrapping an electricity storage device element in the exterior material for an electricity storage device according to the present disclosure.

[0223] For example, an electricity storage device using the electricity storage device packaging material can be provided by covering an electricity storage device element having at least a positive electrode, a negative electrode, and an electrolyte with the electricity storage device packaging material of the present disclosure in a state in which metal terminals connected to each of the positive electrode and negative electrode protrude outward, so that a flange portion (a region where the heat-sealable resin layers contact each other) can be formed around the periphery of the electricity storage device element, and then heat-sealing the heat-sealable resin layers of the flange portion to provide a hermetic seal. Note that when an electricity storage device element is housed in a package formed from the electricity storage device packaging material of the present disclosure, the package is formed so that the heat-sealable resin portion of the electricity storage device packaging material of the present disclosure faces inside (the surface in contact with the electricity storage device element). A package may be formed by overlapping two electrical storage device exterior materials with the heat-sealable resin layers facing each other and heat-sealing the peripheral portions of the overlapped electrical storage device exterior materials. Alternatively, as shown in the example of FIG. 9, one electrical storage device exterior material may be folded back and overlapped, and the peripheral portions may be heat-sealed to form a package. When folding back and overlapping, as shown in the example of FIG. 9, the sides other than the folded side may be heat-sealed to form a package with a three-sided seal, or the material may be folded back and sealed on all four sides so as to form a flange portion. Note that when the innermost and outermost layers of the electrical storage device exterior material are heat-sealable resin layers, the package may be formed by heat-sealing the innermost heat-sealable resin layer and the outermost heat-sealable resin layer. In addition to an embodiment in which mutually facing surfaces of electrical storage device exterior materials are heat-sealed, an embodiment in which the outer and inner surfaces of the electrical storage device exterior material are heat-sealed is also preferred.

[0224] Furthermore, a recess for accommodating an electricity storage device element may be formed in the electrical storage device packaging material by deep drawing or bulging. As in the example shown in Fig. 9, a recess may be provided in one electrical storage device packaging material and no recess may be provided in the other electrical storage device packaging material, or a recess may also be provided in the other electrical storage device packaging material.

[0225] The exterior material for an electricity storage device of the present disclosure is one that, in an electricity storage device using an exterior body including an electricity storage device exterior material that encases an electrode body and a lid, suppresses the occurrence of cracks in the sealing portion of the electricity storage device exterior material with the lid when the electricity storage device is repeatedly exposed to high and low temperature changes. Therefore, the electricity storage device element may be sealed with the lid in addition to the exterior material for an electricity storage device. That is, the exterior material for an electricity storage device and the lid constitute an exterior body (exterior body for an electricity storage device) that seals the electricity storage device element. For example, the electricity storage device element may be housed inside a cylindrically configured exterior material for an electricity storage device, and the opening may be closed with the lid. In another example, the electricity storage device element connected to the lid may be housed inside a cylindrically configured exterior material for an electricity storage device that has an opening, and the opening may be closed with the lid. The lid and the exterior material for an electricity storage device are preferably joined by any means. From the viewpoint of reducing the dead space between the electricity storage device element and the exterior material for an electricity storage device so as to improve the volumetric energy density of the electricity storage device, the exterior material for an electricity storage device is preferably wrapped around the electricity storage device element and the lid. When the exterior material for an electricity storage device is wrapped around the electricity storage device element and the lid, only one sheet of the exterior material for an electricity storage device may be wrapped around the electricity storage device element and the lid, or multiple sheets of the exterior material for an electricity storage device may be wrapped around the electricity storage device element and the lid.

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

[0227] Below, we will specifically explain the case where the energy storage device includes an electrode body and an outer casing that seals the electrode body, and the outer casing has an outer casing material for an energy storage device of the present disclosure that wraps the electrode body, and a lid that seals the electrode body together with the outer casing material for an energy storage device.

[0228] Like Fig. 1, Fig. 10 is a perspective view that schematically shows the electricity storage device 10. Fig. 11 is a cross-sectional view taken along line AA in Fig. 1. In Figs. 10 to 12, the arrow z direction (z1 direction and z2 direction) indicates the thickness direction of the electricity storage device 10, the arrow x direction (x1 direction and x2 direction) indicates the width direction of the electricity storage device 10, and the arrow y direction (y1 direction and y2 direction) indicates the depth direction of the electricity storage device 10. The directions indicated by the arrows x, y, and z are common to the subsequent figures.

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

[0230] 1 and 2, the electricity storage device 10 in FIGS. 10 and 11 includes two electrode terminals 30. The electrode terminals 30 are metal terminals used for inputting and outputting electric power to and from the electrode body 20. One end of the electrode terminal 30 is electrically connected to an electrode (positive electrode or negative electrode) included in the electrode body 20. The other end of the electrode terminal 30 protrudes outward from, for example, an edge of the exterior body 40. Note that the electrode terminal 30 may be any terminal as long as it is capable of inputting and outputting electric power to and from the electrode body 20, and may not, for example, protrude from the exterior body 40. For example, when the lid body 60 described below is made of a conductive material, the lid body 60 may also function as the electrode terminal 30. In this case, the lid body 60, which functions as an electrode terminal, may or may not protrude from the exterior body 40.

[0231] As described above, the metal material constituting the electrode terminal 30 is, for example, aluminum, nickel, or copper. For example, when 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. Note that the outermost layer of the electrode body 20 does not necessarily have to be an electrode, and may be, for example, a protective tape or a separator. The outer shape of the electrode body 20 is, for example, a rectangular parallelepiped.

[0232] As described above, the exterior housing 40 seals the electrode assembly 20. The exterior housing 40 includes an exterior material for an electricity storage device 50 and a lid 60. The exterior material for an electricity storage device 50 encases the electrode assembly 20. As in FIGS. 1 and 2 , in FIGS. 10 and 11 , the exterior material for an electricity storage device 50 is wrapped around the electrode assembly 20. The lid 60 is disposed on the side of the electrode assembly 20 in the y direction. In another example, the electrode assembly 20 may be housed inside a cylindrical exterior material for an electricity storage device 50 having openings at both ends in the y direction, and the openings may be closed by the lid 60. In yet another example, the electrode assembly 20 connected to the lid 60 may be housed inside a cylindrical exterior material for an electricity storage device 50 having openings, and the openings may be closed by the lid 60.

[0233] As described above, the exterior body 40 has a pair of main surfaces and a pair of side surfaces formed by the exterior material 50 for an electricity storage device. As in FIGS. 1 and 2, the pair of main surfaces in FIGS. 10 and 11 are substantially the same size. Furthermore, the pair of side surfaces are substantially the same size. The pair of main surfaces each have a larger area than the pair of side surfaces. The pair of lid bodies 60 are respectively disposed on the sides of the electrode body 20 so as to close the pair of openings. Note that in the present disclosure, the main surfaces and side surfaces are the surfaces of the exterior body 40 excluding the lid bodies 60.

[0234] As described above, for example, there is a method of forming a storage portion (recess) for accommodating the electrode assembly 20 in the electrical storage device exterior material 50 through cold forming. However, it is not necessarily easy to form a deep storage portion using such a method. Attempting to form a deep storage portion (recess) (for example, a molding depth of 15 mm) through cold forming increases the likelihood of pinholes or cracks occurring in the electrical storage device exterior material 50, resulting in a decrease in battery performance. On the other hand, the exterior material 40 seals the electrode assembly 20 by wrapping the electrical storage device exterior material 50 around the electrode assembly 20, and therefore can easily seal the electrode assembly 20 regardless of the thickness of the electrode assembly 20. Note that in order to reduce the dead space between the electrode assembly 20 and the electrical storage device exterior material 50 so as to improve the volumetric energy density of the electrical storage device 10, it is preferable that the electrical storage device exterior material 50 be wrapped so as to contact the outer surface of the electrode assembly 20. Furthermore, in an all-solid-state battery, it is necessary to apply a high pressure uniformly from the outer surface of the battery in order to exert battery performance, and therefore it is necessary to eliminate the space between the electrode body 20 and the exterior material 50 for an electricity storage device. Therefore, it is preferable that the exterior material 50 for an electricity storage device is wrapped around the electrode body 20 so as to contact the outer surface of the electrode body 20.

[0235] The packaging material 50 for an electricity 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 packaging material 50 for an electricity storage device are as described above.

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

[0237] Specific examples of the resin for the lid 60 are as described above.

[0238] As described above, the resin as the resin material may contain a filler as needed. Specific examples of the filler are as described above.

[0239] As described above, the melt mass flow rate (measured at 230°C) of the resin material contained in the material constituting the lid 60 is preferably in the range of 1 g / 10 min to 100 g / 10 min, more preferably in the range of 1 g / 10 min to 80 g / 10 min, more preferably in the range of 1 g / 10 min to 60 g / 10 min, more preferably in the range of 5 g / 10 min to 100 g / 10 min, more preferably in the range of 5 g / 10 min to 80 g / 10 min, and even 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 configured to contain a conductive material. "Configured to contain a conductive material" means that, when the entire material constituting the lid 60 is taken as 100% by mass, the content of the conductive material is 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. In other words, the material constituting the lid 60 can contain, in addition to the conductive material, materials other than the conductive material.

[0241] As described above, the conductive material constituting the lid body 60 is, for example, a metal material. The metal material constituting the lid body 60 is, for example, aluminum, an aluminum alloy, nickel, copper, or a copper alloy. For example, when the electrode body 20 is a lithium-ion battery, the lid body 60 connected to the positive electrode is preferably made of aluminum or an aluminum alloy. The lid body 60 connected to the negative electrode is preferably made of nickel, copper, or a copper alloy. The material constituting the lid body 60 connected to the negative electrode may be nickel-plated copper. The material constituting the lid body 60 may include recycled metal materials. When the lid body 60 is made of a conductive material, the lid body 60 also functions as the electrode terminal 30, so the electrode terminal 30 can be omitted from the electricity storage device 10.

[0242] As described above, the lid body 60 may have a configuration in which at least a portion of the lid main body 61 is covered with the covering body 62. In the lid body 60 of FIG. 12, the periphery of the lid main body 61 (the periphery of the thickness portion) is covered with the covering body 62. The lid body 60 may be joined to the thermally adhesive resin layer 4 of the packaging material 50 for an electricity storage device via the covering body 62. The covering body 62 is preferably composed of a resin material. The lid body 60 has the lid main body 61 and the covering body 62 that joins the lid main body 61 and the packaging material 50 for an electricity storage device, and the covering body 62 can be composed of a resin (resin material). The definition of "composed of a resin material" regarding the covering body 62 is the same as in the case of the lid body 60.

[0243] As described above, when the lid body 60 is configured to include a conductive material, the lid main body 61 may be configured from a conductive material, and at least a portion of the lid main body 61 may be covered with the covering body 62.

[0244] As described above, when the lid 60 contains a conductive material, the lid 60 may be bonded to the electrical storage device packaging material 50 via an adhesive film instead of a covering. Any adhesive film can be selected as long as it can bond the electrical storage device packaging material 50 and the lid 60. The adhesive film is preferably a laminated film having at least a heat-sealable resin layer, a heat-resistant substrate layer, and a heat-sealable resin layer in this order. The specifications for the heat-sealable resin layer of the adhesive film are the same as those for the heat-sealable resin layer 4. The materials constituting the heat-sealable resin layers on both sides of the adhesive film may be the same or different, and are appropriately selected depending on the materials constituting the heat-sealable resin layer 4 of the electrical storage device packaging material 50 and the materials constituting the lid 60. The material constituting the heat-sealable resin layer of the adhesive film on the side bonded to the lid 60 is preferably an acid-modified polyolefin resin graft-modified with an acid such as maleic anhydride. The heat-sealable resin layer of the adhesive film on the side that is bonded to the packaging material 50 for an electricity storage device is preferably made of the same type of material as the material that constitutes the heat-sealable resin layer 4 of the packaging material 50 for an electricity storage device.

[0245] As described above, the heat-resistant base layer may be any film made of a heat-resistant resin, and examples of such films include unstretched or stretched films of polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polymethylpentene (registered trademark), polyacetal cyclic polyolefin, polyethylene, polypropylene, etc. Polyethylene terephthalate is particularly preferred because it is inexpensive and has high strength.

[0246] As described above, the adhesive film preferably has adhesiveness. When the second sealing portion 80, which will be described later, is formed with the adhesive film disposed between the electrical storage device packaging material 50 and the lid 60, the adhesive film is less likely to shift position relative to the lid 60 and the electrical storage device packaging material 50. By incorporating a tackifier resin into the heat-sealable resin layer of the adhesive film, adhesiveness can be imparted to the adhesive film. Examples of the tackifier resin include amorphous polyolefins. Examples of amorphous polyolefins include amorphous polypropylene and copolymers of amorphous propylene and other α-olefins. The content of the tackifier resin relative to the base material constituting the heat-sealable resin is preferably 10 to 20% by weight or less.

[0247] As described above, the lid body 60 has a first main surface located on the inside (electrode body 20 side) of the electricity storage device, a second main surface located on the outside of the electricity storage device, and four side surfaces that are thermally fused to the thermally adhesive resin layer 4 of the exterior packaging material 50 for an electricity 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 body 60 is a cylinder, a prism, a rectangular parallelepiped, a cube, or the like, it is preferable that the lid body 60 has a certain degree of thickness in the thickness direction (y direction) so that deformation of the exterior body 40 is suppressed even when the power storage device 10 is placed on top of it. From another perspective, when the lid body 60 is a cylinder, a prism, a rectangular parallelepiped, a cube, or the like, it is preferable that the lid body 60 has a certain degree of thickness in the thickness direction (y direction) so that the lid joint portion of the lid body 60 can be suitably joined to the exterior film 50 when forming the second sealing portion 80. The minimum value of the thickness in the thickness direction (y direction) of the lid body 60 (the distance in the y direction between the first main surface and the second main surface) is, for example, 1.0 mm, more preferably 3.0 mm, and even more preferably 4.0 mm. The maximum thickness of the lid 60 in the y direction is, for example, 20 mm, preferably 15.0 mm, more preferably 10.0 mm, even more preferably 8.0 mm, and even more preferably 7.0 mm. The maximum thickness of the lid 60 in the y direction may be 10 mm or more. Preferred ranges for the thickness of the material constituting the lid 60 are 1.0 mm to 20.0 mm, 1.0 mm to 15.0 mm, 1.0 mm to 10.0 mm, 1.0 mm to 8.0 mm, 1.0 mm to 7.0 mm, 3.0 mm to 20.0 mm, 3.0 mm to 15.0 mm, 3.0 mm to 10.0 mm, 3.0 mm to 8.0 mm, 3.0 mm to 7.0 mm, 4.0 mm to 20.0 mm, 4.0 mm to 15.0 mm, 4.0 mm to 10.0 mm, 4.0 mm to 8.0 mm, and 4.0 mm to 7.0 mm. In the present disclosure, when the lid body 60 is expressed as a cylinder, a prism, a rectangular parallelepiped, a cube, or the like, this does not include an embodiment in which the lid body 60 is made solely of a film as defined by the JIS (Japanese Industrial Standards) [Packaging Terminology] standard. The thickness of the lid body 60 may vary depending on the part of the lid body 60. When the thickness of the lid body 60 varies depending on the part, the thickness of the lid body 60 is the thickness of the thickest part.

[0249] 1 and 2, in FIGS. 10 and 11, the lid 60 has a through-hole formed therein through which the electrode terminal 30 is inserted. The through-hole penetrates the first and second main surfaces of the lid. When the electrode assembly 20 is housed, the electrode terminal 30 passes through the through-hole formed in the lid 60 and protrudes to the outside of the exterior body 40. A 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 from which the electrode terminal 30 protrudes to the outside can be selected arbitrarily. For example, the electrode terminal 30 may protrude to the outside from a hole formed in any one of the six surfaces of the exterior body 40. In this case, a small gap between the exterior body 40 and the electrode terminal 30 is filled with, for example, resin. The electrode terminal 30 may protrude from between the lid 60 and the exterior material 50 for an energy storage device, or may protrude from a first sealing portion 70 described below. In the electricity storage device 10, the lid body 60 and the electrode terminal 30 are provided as separate bodies, but the lid body 60 and the electrode terminal 30 may be formed integrally. Note that if the electrode terminal 30 does not protrude from the edge of the exterior body 40, the lid body 60 does not need to have a through-hole formed therein.

[0250] 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, and the facing surfaces (heat-sealable resin layers 4) of the outer casing material 50 for the energy storage device are heat-sealed to form a first sealing portion 70.

[0251] As described above, the first sealing portion 70 is formed by heat-sealing the heat-fusible resin layers of the exterior material 50 for an electricity storage device. The first sealing portion 70 extends in the longitudinal direction of the exterior body 40. The position at which the first sealing portion 70 is formed in the exterior body 40 can be selected arbitrarily. As in FIG. 1, as shown in FIG. 10, the base of the first sealing portion 70 is preferably located on the boundary between the main surface and the side surface of the exterior body 40. The base of the first sealing portion 70 may be located on any surface of the exterior body 40. As in FIG. 1, in FIG. 10, the first sealing portion 70 protrudes outward beyond the electrode assembly 20 in a plan view. The first sealing portion 70 may be folded, for example, toward the side surface of the exterior body 40 or toward the main surface.

[0252] As described above, the heat-sealable resin layer 4 of the electrical storage device packaging material 50 and the lid joint portion of the lid 60 (the portion where the heat-sealable resin layer 4 of the electrical storage device packaging material 50 and the lid 60 come into contact) are joined by, for example, heat sealing to form the second sealing portion 80. The electrical storage device packaging material 50 and the lid 60 can be joined by any method such as welding.

[0253] The exterior material for an electricity storage device according to the present disclosure can be suitably used in electricity storage devices such as batteries (including condensers, capacitors, etc.). The exterior material for an electricity storage device according to the present disclosure may be used in either primary or secondary batteries, but is preferably used in secondary batteries. The type of secondary battery to which the exterior material for an electricity storage device according to the present disclosure is applied is not particularly limited, and examples include lithium ion batteries, lithium ion polymer batteries, all-solid-state batteries, semi-solid batteries, quasi-solid batteries, polymer batteries, all-resin batteries, lead-acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, silver oxide-zinc batteries, metal-air batteries, polyvalent cation batteries, condensers, and capacitors. Among these secondary batteries, lithium ion batteries and lithium ion polymer batteries are suitable applications for the exterior material for an electricity storage device according to the present disclosure. [Example]

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

[0255] <Exterior film manufacturing method> Comparative Example 1A A laminate was prepared as the substrate layer, in which a biaxially oriented polyethylene terephthalate (PET) film (thickness 12 μm) and an oriented nylon (ONy) film (thickness 15 μm) were bonded together with an adhesive layer (formed with a two-component curing urethane adhesive, with a thickness of 3 μm after curing). Furthermore, aluminum foil (JIS H4160:1994 A8079H-O (thickness 40 μm)) was prepared as the barrier layer. Chemical conversion treatment was applied to both sides of the aluminum foil. The aluminum foil was chemically treated using a treatment solution consisting of phenolic resin, a chromium fluoride compound, and phosphoric acid, with a coating amount of chromium of 10 mg / m. 2 (dry mass) was applied to both sides of an aluminum foil by roll coating, and baked.

[0256] Next, a two-component curing urethane adhesive was used to bond the base layer and barrier layer with an adhesive layer (thickness 3 μm) using the dry lamination method, producing a laminate in which the base layer / adhesive layer / barrier layer were laminated in that order.

[0257] Next, maleic anhydride-modified polypropylene to form an adhesive layer (40 μm thick) and random polypropylene to form a heat-sealable resin layer (40 μm thick) were co-extruded onto the barrier layer of each of the laminates obtained above, thereby laminating an adhesive layer / heat-sealable resin layer on the barrier layer. Next, the resulting 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-sealable resin layer were laminated in this order.

[0258] Comparative example 2A An exterior film consisting of a laminate in which a base layer / adhesive layer / barrier layer / adhesive layer / thermally adhesive resin layer were laminated in this order was obtained in the same manner as in Comparative Example 1A, except that aluminum foil (JIS H4160:1994 A8079H-O (thickness 60 μm)) was used as the barrier layer.

[0259] Example 1A An exterior film consisting of a laminate in which a base layer / adhesive layer / barrier layer / adhesive layer / thermally adhesive resin layer were laminated in this order was obtained in the same manner as in Comparative Example 1A, except that aluminum foil (JIS H4160:1994 A8079H-O (thickness 80 μm)) was used as the barrier layer.

[0260] Example 2A An exterior film consisting of a laminate in which a base layer / adhesive layer / barrier layer / adhesive layer / thermally adhesive resin layer were laminated in this order was obtained in the same manner as in Comparative Example 1A, except that a stainless steel foil (JIS G4303 SUS304 (thickness 60 μm)) was used as the barrier layer.

[0261] Example 3A The exterior film used was the same as that used in Comparative Example 1 A. In the thermal shock test described below, the material of the lid of the exterior body used for the simulated electricity storage device was different from that used in Comparative Example 1 A.

[0262] Example 4A The exterior film used was the same as that used in Comparative Example 1 A. In the thermal shock test described below, the material of the lid of the exterior body used for the simulated electricity storage device was different from that of Comparative Example 1 A and Example 3A.

[0263] <Measurement of area-average crystal grain size R1, 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 below. Next, for the simulated energy storage device, the barrier layer at the position where the heat-sealable resin layer of the exterior film was heat-sealed to the lid (sealed portion (second sealed portion)) and the barrier layer at the position where the heat-sealable resin layer of the exterior film was not heat-sealed (non-sealed portion) were obtained, and crystal analysis was performed using the EBSD method on each to measure the area average crystal grain sizes R1 and R2 of the barrier layer. The specific measurement method is as follows.

[0264] Crystal analysis was performed using the EBSD method on the cross section of each barrier layer perpendicular to the rolling direction, and the area-average crystal grain size of the barrier layer was measured. Details of the measurement conditions are as follows. The measurement results are shown in Table 1A. The area-average crystal 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 crystal analysis using the EBSD method were linked to obtain a diameter of approximately 5000 μm. 2 The area average crystal grain size of the crystals included in the measurement area is equal to or greater than 100 μm. The crystal grain size is the value measured for the crystals included in the measurement area, assuming that the crystal shape is circular. The standard deviation of the crystal grain size is approximately 5000 μm, obtained by combining multiple images obtained by crystal analysis using the EBSD method after removing areas with a CI value of 0.1 or less. 2 The area average crystal grain size R2 of the barrier layer was measured at a location 3 cm away from the measurement location of the area average crystal grain size R1.

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

[0266] (Pretreatment) As a pretreatment, the barrier layer was cut in a direction perpendicular to the rolling direction (RD) to obtain a cross section. The rolling direction of the barrier layer was determined by observing the shiny surface of the barrier layer with a metallurgical microscope, and the direction of linear rolling marks was the direction in which these marks extended. Specifically, the barrier layer to be used as a sample was first cut into a 5 mm (perpendicular to the rolling direction) x 10 mm (rolling direction) piece using a trimming razor, and then embedded in resin. Next, the barrier layer was cut together with the resin using the trimming razor in a direction perpendicular to the rolling direction of the barrier layer, perpendicular to the surface of the barrier layer, to expose the cross section of the barrier layer. Next, the obtained cross section was trimmed using a microtome (an ultramicrotome manufactured by Leica Microsystems). In this trimming, in order to reduce mechanical distortion in the cross section, the microtome was advanced by approximately 1 mm in a direction perpendicular to the cross section, together with the embedded resin. Next, a broad argon beam was irradiated perpendicularly to the cross section using an ion milling device (Hitachi High-Technologies Corporation) under conditions of a protrusion width of 50 μm, a voltage of 6 kV, and 4 hours to prepare a cross section for measurement. This is a process for precisely exposing the cross section of the barrier layer so as to minimize mechanical damage to the crystal structure that occurred in the previous process. Note that in this disclosure, the "perpendicular direction" when cutting the aluminum alloy foil is confirmed under a stereomicroscope, and therefore may include an error of about 10°. In other words, the direction perpendicular to the rolling direction is defined as 80 to 100° to the rolling direction, and the direction perpendicular to the surface is defined as 80 to 100° relative to the surface.

[0267] (SEM conditions) The conditions of the scanning electron microscope (SEM) used for the EBSD method are as follows: Observation magnification: 2000x (the standard observation magnification when taking photos is Polaroid 545) Accelerating voltage: 15 kV 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 carried out using the crystal orientation analysis software OIM (Ver. 7.3) manufactured by TSL Solutions Co., Ltd. Multiple images are stitched together to measure an area of ​​approximately 5000 μm 2 At this time, the measurement area was the area from the center of the barrier layer in the thickness direction to both ends, and the area where the resin was attached to the cross section and the area where the acid-resistant film was present were excluded from the measurement area. The CI value was set to 0.1 or more, the grain boundary condition to 0.5 degrees or more, and the minimum grain size to 3 steps or more. After stitching the images together, the pole figures were checked. If the center of the pole figure is off by 10° or more, rotate the crystal data to restore symmetry. The pole figure used as reference is measured from the sample surface using XRD. When obtaining a pole figure from the surface using EBSD, the sample surface is mechanically polished, flat-milled, electrolytically polished, etc., before performing a wide-area measurement to remove the influence of the mechanical crystal structure of the sample surface. The pole figure obtained from the surface direction is then rotated 90° so that it is the same as the pole figure obtained from the same orientation as the pole figure obtained from the cross section of the target sample. Use this pole figure as a reference. The analysis was performed by excluding data with a Confidence Index (CI value) of 0.1 or less, as defined by OIM (Ver. 7.3), a crystal orientation analysis software made by TSL Solutions Co., Ltd. This allows us to eliminate data based on the resin used in pre-processing present on the front and back of the sample, grain boundaries present on the cross section, and amorphous matter.

[0269] <Measurement of Young's modulus of exterior film> The Young's modulus of the exterior film was measured by the following method, and the results are shown in Table 1A. In accordance with the provisions of JIS K6251:2017, the SS curve in the TD direction of the exterior film was obtained under the following measurement conditions, and the Young's modulus (MPa) was calculated from the maximum value of the slope of the SS curve. (Measurement conditions) A tensile tester (Shimadzu Autograph AG-X Plus) is used. Test piece shape: Dumbbell No. 7 Test piece width: 2 mm Test piece length: 35 mm Thickness of test piece: 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] <Thermal shock test> The packaging films produced in each Example and Comparative Example were each cut into a rectangular shape measuring MD 360 mm x TD 160 mm. Meanwhile, for Comparative Examples 1A-2A and Examples 1A-2A, a rectangular parallelepiped (100 mm long x 30 mm wide x 5 mm thick) polypropylene lid was prepared as the lid for the packaging body. For Example 3A, a rectangular parallelepiped (98 mm long x 28 mm wide x 5 mm thick) aluminum lid body was prepared, the periphery (periphery of the thick portion) of which was covered with a polypropylene (PP) covering. For Example 4A, a rectangular parallelepiped (98 mm long x 28 mm wide x 5 mm thick) aluminum lid body was prepared, the periphery (periphery of the thick portion) of which was covered with a maleic anhydride-modified polypropylene (PPa) covering. Furthermore, a rectangular parallelepiped (length 140 mm x width 98 mm x thickness 28 mm) aluminum block was prepared as a simulated electrode body.

[0271] Next, as shown in the schematic diagram of FIG. 1, lids were placed on both sides of the electrode assembly in the longitudinal direction, and this was wrapped in an exterior film. The position where the heat-sealable resin layers of the exterior film faced each other (first sealing portion 70) and the position where the heat-sealable resin layer of the exterior film and the lid came into contact (second sealing portion 80) were heat-sealed using a heat seal bar, respectively, to obtain a simulated electricity storage device. Note that the simulated electricity storage device was not provided with electrode terminals as shown in FIG. 1. The seal width at the position where the heat-sealable resin layers of the exterior film faced each other (first sealing portion 70) was 10 mm. The seal width at the position where the heat-sealable resin layer of the exterior film and the lid came into contact (second sealing portion 80) was the thickness of the lid (5 mm). The heat-sealing conditions (temperature, surface pressure, and time) for the second sealing portion 80 were 180°C, 0.60 MPa, and 3 seconds for Comparative Example 1A, 180°C, 1.20 MPa, and 5 seconds for Comparative Example 2A and Examples 1A-3A, respectively, and 180°C, 0.60 MPa, and 7 seconds for Example 4A. All conditions were set so that the ratio of "(thickness of the heat-sealable resin layer at the position where the heat-sealable resin layer is heat-sealed to the lid) / (thickness of the heat-sealable resin layer at the position where the heat-sealable resin layer is not heat-sealed to the lid)" was 20 to 80%. The conditions for achieving a thickness of the heat-sealable resin layer of 20% to 80% can be adjusted, for example, by setting the heat-sealing temperature to approximately 160 to 240°C, the surface pressure to approximately 0.2 to 1.5 MPa, and the heat-sealing time to approximately 1 to 12 seconds.

[0272] The simulated energy storage devices were subjected to a thermal shock test in which each device was left at -30°C for 30 minutes and then left at 80°C for 30 minutes, with this cycle being repeated 800 times to evaluate whether cracks were prevented from occurring in the sealing portion between the exterior film and the lid (the surface layer of the exterior film) 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 exterior film with the lid in the electricity storage devices of Comparative Examples 1A-2A. On the other hand, fine cracks occurred in the sealing portion of the exterior film with the lid in the electricity storage device of Example 1A, but it could be evaluated that the occurrence of cracks in the sealing portion of the exterior film with the lid was suppressed. In the electricity storage devices of Examples 2A-4A, no cracks occurred in the sealing portion of the exterior film with the lid, and it could be evaluated that the occurrence of cracks in the sealing portion of the exterior film with the lid was particularly well suppressed. Fine cracks are cracks that do not reveal voids in the barrier layer when the sealing portion is observed with an SEM, 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 conditions for SEM observation were: observation magnification: 1000x, accelerating voltage: 5 kV, and working distance: 10 mm.

[0274] [Table 1A]

[0275] In Table 1A, PET is a polyethylene terephthalate film, DL is an adhesive layer formed by dry lamination, ONy is an oriented nylon film, AL is an aluminum alloy foil, SUS is a stainless steel foil, PPa is a maleic anhydride-modified polypropylene layer, and PP is a polypropylene layer. The Young's modulus, area-average crystal grain size R1, R2, and R1 / R2 values ​​were calculated by rounding off the values ​​one digit smaller than those listed in Table 1A.

[0276] <Manufacturing of exterior materials for electricity storage devices> Comparative example 1B A laminate was prepared as the substrate layer, in which a biaxially oriented polyethylene terephthalate (PET) film (thickness 12 μm) and an oriented nylon (ONy) film (thickness 15 μm) were bonded together with an adhesive layer (formed with a two-component curing urethane adhesive, with a thickness of 3 μm after curing). Furthermore, an aluminum foil (JIS H4160:1994 A8079H-O (thickness 60 μm)) was prepared as the barrier layer. Both sides of the aluminum foil were subjected to a chemical conversion treatment. The chemical conversion treatment of the aluminum foil was carried out by using a treatment solution consisting of a phenolic resin, a chromium fluoride compound, and phosphoric acid, with a coating amount of chromium of 10 mg / m. 2 (dry mass) was applied to both sides of an aluminum foil by roll coating, and baked.

[0277] Next, a two-component curing urethane adhesive was used to bond the base layer and barrier layer with an adhesive layer (thickness 3 μm) using the dry lamination method, producing a laminate in which the base layer / adhesive layer / barrier layer were laminated in that order.

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

[0279] Example 1B An exterior material for a storage battery device was obtained in the same manner as in Comparative Example 1B, except that aluminum foil (JIS H4160:1994 A8079H-O (thickness: 80 μm)) was used as the barrier layer, and the laminate was formed by laminating a base layer / adhesive layer / barrier layer / adhesive layer / thermally adhesive resin layer in this order.

[0280] Example 2B An exterior material for a storage battery device was obtained in the same manner as in Comparative Example 1B, except that stainless steel foil (JIS G4303 SUS304 (thickness 60 μm)) was used as the barrier layer, consisting of a laminate in which a base layer / adhesive layer / barrier layer / adhesive layer / thermally adhesive resin layer were laminated in this order.

[0281] <Measurement of area-average crystal grain size R1, 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 below. Next, for the simulated energy storage device, the barrier layer at the position (sealed portion (second sealed portion)) where the heat-sealable resin layer of the energy storage device casing material was heat-sealed to the polypropylene plate (polypropylene lid) and the barrier layer at the position (non-sealed portion) where the heat-sealable resin layer of the energy storage device casing material was not heat-sealed were obtained, and crystal analysis was performed using the EBSD method to measure the area average crystal grain sizes R1 and R2 of the barrier layer. The specific measurement method is as follows.

[0282] Crystal analysis was performed using the EBSD method on a cross section perpendicular to the rolling direction of each barrier layer, and the area-average crystal grain size of the barrier layer was measured. Details of the measurement conditions are as follows. The measurement results are shown in Table 1B. The area-average crystal 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 crystal analysis using the EBSD method were linked to obtain a diameter of approximately 5000 μm. 2 The area average crystal grain size of the crystals included in the measurement area is equal to or greater than 100 μm. The maximum crystal grain size is the value measured for the largest crystal among the crystals included in the measurement area, assuming that the crystal shape is circular. The standard deviation of the crystal grain size is approximately 5000 μm, obtained by combining multiple images obtained by crystal analysis using the EBSD method after removing areas with a CI value of 0.1 or less. 2 The diameter was calculated from the distribution of the crystal grain size (diameter when the crystal area is assumed to be a circle) of the crystals contained in the above measurement area.

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

[0284] (Pretreatment) As a pretreatment, the barrier layer was cut in a direction perpendicular to the rolling direction (RD) to obtain a cross section. The rolling direction of the barrier layer was determined by observing the shiny surface of the barrier layer with a metallurgical microscope, and the direction of linear rolling marks was the direction in which these marks extended. Specifically, the barrier layer to be used as a sample was first cut into a 5 mm (perpendicular to the rolling direction) x 10 mm (rolling direction) piece using a trimming razor, and then embedded in resin. Next, the barrier layer was cut together with the resin using the trimming razor in a direction perpendicular to the rolling direction of the barrier layer, perpendicular to the surface of the barrier layer, to expose the cross section of the barrier layer. Next, the obtained cross section was trimmed using a microtome (an ultramicrotome manufactured by Leica Microsystems). In this trimming, in order to reduce mechanical distortion in the cross section, the microtome was advanced by approximately 1 mm in a direction perpendicular to the cross section, together with the embedded resin. Next, a broad argon beam was irradiated perpendicularly to the cross section using an ion milling device (Hitachi High-Technologies Corporation) under conditions of a protrusion width of 50 μm, a voltage of 6 kV, and 4 hours to prepare a cross section for measurement. This is a process for precisely exposing the cross section of the barrier layer so as to minimize mechanical damage to the crystal structure that occurred in the previous process. Note that in this disclosure, the "perpendicular direction" when cutting the aluminum alloy foil is confirmed under a stereomicroscope, and therefore may include an error of about 10°. In other words, the direction perpendicular to the rolling direction is defined as 80 to 100° to the rolling direction, and the direction perpendicular to the surface is defined as 80 to 100° relative to the surface.

[0285] (SEM conditions) The conditions of the scanning electron microscope (SEM) used for the EBSD method are as follows: Observation magnification: 2000x (the standard observation magnification when taking photos is Polaroid 545) Accelerating voltage: 15 kV 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 carried out using the crystal orientation analysis software OIM (Ver. 7.3) manufactured by TSL Solutions Co., Ltd. Multiple images are stitched together to measure an area of ​​approximately 5000 μm 2 At this time, the measurement area was the area from the center of the barrier layer in the thickness direction to both ends, and the area where the resin was attached to the cross section and the area where the acid-resistant film was present were excluded from the measurement area. The CI value was set to 0.1 or more, the grain boundary condition to 0.5 degrees or more, and the minimum grain size to 3 steps or more. After stitching the images together, the pole figures were checked. If the center of the pole figure is off by 10° or more, rotate the crystal data to restore symmetry. The pole figure used as reference is measured from the sample surface using XRD. When obtaining a pole figure from the surface using EBSD, the sample surface is mechanically polished, flat-milled, electrolytically polished, etc., before performing a wide-area measurement to remove the influence of the mechanical crystal structure of the sample surface. The pole figure obtained from the surface direction is then rotated 90° so that it is the same as the pole figure obtained from the same orientation as the pole figure obtained from the cross section of the target sample. Use this pole figure as a reference. The analysis was performed by excluding data with a Confidence Index (CI value) of 0.1 or less, as defined by OIM (Ver. 7.3), a crystal orientation analysis software made by TSL Solutions Co., Ltd. This allows us to eliminate data based on the resin used in pre-processing present on the front and back of the sample, grain boundaries present on the cross section, and amorphous matter.

[0287] <Measurement of Young's modulus of exterior materials for energy storage devices> The Young's modulus of the packaging material for an electricity storage device was measured by the following method, and 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 tester (Shimadzu Autograph AG-X Plus) is used. Test piece shape: Dumbbell No. 7 Test piece width: 2 mm Test piece length: 35 mm Thickness of test piece: 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] <Thermal shock test> The packaging materials for electricity storage devices manufactured in each Example and Comparative Example were each cut into a rectangular shape with dimensions of MD 360 mm x TD 160 mm. A rectangular parallelepiped (100 mm long x 30 mm wide x 5 mm thick) polypropylene lid (polypropylene plate) was prepared as the lid of the packaging body. Furthermore, a rectangular parallelepiped (140 mm long x 98 mm wide x 28 mm thick) aluminum block was prepared as a simulated electrode body.

[0289] Next, as shown in the schematic diagram of FIG. 1, lids were placed on both sides of the electrode assembly in the longitudinal direction, and this was wrapped in an exterior material for an electricity storage device. The position where the heat-sealable resin layers of the exterior material for an electricity storage device face each other (first sealing portion 70) and the position where the heat-sealable resin layer of the exterior material for an electricity storage device and the lid come into contact (second sealing portion 80) were each heat-sealed using a heat seal bar to obtain a simulated electricity storage device. Note that the simulated electricity storage device was not provided with electrode terminals as shown in FIG. 1. The seal width at the position where the heat-sealable resin layers of the exterior material for an electricity storage device face each other (first sealing portion 70) was 10 mm. The seal width at the position where the heat-sealable resin layer of the exterior material for an electricity storage device and the lid come into contact (second sealing portion 80) was the thickness of the lid (5 mm). The heat sealing conditions (temperature, surface pressure, time) for the second sealing portion 80 were 180°C, 1.20 MPa, and 5 seconds, respectively. These heat sealing conditions were set so that the ratio of "(thickness of the heat-sealable resin layer at the position where the heat-sealable resin layer is heat-sealed to the lid) / (thickness of the heat-sealable resin layer at the position where the heat-sealable resin layer is not heat-sealed to the lid)" was 20 to 80%.

[0290] The simulated electricity storage devices thus obtained were subjected to a thermal shock test in which each device was left standing in a -30°C environment for 30 minutes, followed by leaving the device standing in an 80°C environment for 30 minutes, with this cycle being repeated 800 times to evaluate whether or not cracking was suppressed in the sealing portion between the electricity storage device packaging material and the lid (the surface layer of the electricity storage device packaging material) when the electricity 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, cracks occurred in the sealing portion between the casing material for an electricity storage device and the lid in the electricity storage device of Comparative Example 1B. On the other hand, fine cracks occurred in the sealing portion between the casing material for an electricity storage device and the lid in the electricity storage device of Example 1B, but it can be evaluated that the occurrence of cracks in the sealing portion between the casing material for an electricity storage device and the lid was suppressed. In the electricity storage device of Example 2B, no cracks occurred in the sealing portion between the casing material for an electricity storage device and the lid, and it can be evaluated that the occurrence of cracks in the sealing portion between the casing material for an electricity storage device and the lid was particularly well suppressed. Fine cracks are cracks that do not result in voids being observed in the barrier layer when the sealing portion is observed with an SEM, whereas the cracks observed in Comparative Example 1B were cracks that result in voids being observed in the barrier layer when the sealing portion is observed with an SEM. The conditions for SEM observation were observation magnification: 1000 times, acceleration voltage: 5 kV, and working distance: 10 mm.

[0292] [Table 1B]

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

[0294] As described above, the present disclosure provides the following aspects of the invention. Item 1A. An electricity storage device, An electrode body; an exterior body that seals the electrode body, The exterior body is an exterior film that wraps the electrode body; a lid that seals the electrode body together with the exterior film, the exterior film is composed of a laminate including at least a barrier layer and a heat-sealable resin layer, the barrier layer has a ratio (R1 / R2) of an area average crystal grain size R1 (μm) to an area average crystal grain size R2 (μm) of 55% or more; The area average crystal grain size R1 (μm) is an area average crystal grain size (μm) obtained by performing crystal analysis by EBSD on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position where the heat-fusible resin layer of the packaging film is heat-fused to the lid, The area average crystal grain size R2 (μm) is an area average crystal grain size (μm) obtained by performing crystal analysis by EBSD on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position of the packaging film where the heat-sealable resin layer is not heat-sealed, Energy storage device. Item 2A. The electricity storage device according to Item 1A, wherein the barrier layer is formed of stainless steel, a steel plate, or an aluminum alloy. Item 3A. The lid body has a lid main body and a covering body that joins the lid main body and the exterior film, The electricity storage device according to item 1A or 2A, wherein the covering contains a resin. Item 4A: The electricity storage device according to any one of Items 1A to 3A, further comprising an adhesive layer between the barrier layer and the heat-sealable resin layer. Item 5A: The electricity storage device according to any one of Items 1A to 4A, further comprising a substrate layer on the side of the barrier layer opposite to the thermally adhesive resin layer side. Item 6A. The electricity storage device according to Item 5A, further comprising an adhesive layer between the base layer and the barrier layer. Item 7A: The electricity storage device according to any one of Items 1A to 6A, wherein the exterior film has a Young's modulus of 6000 MPa or more. Item 8A. A method for manufacturing an electricity storage device, The electricity storage device is An electrode body; an exterior body that seals the electrode body, The exterior body is an exterior film that wraps the electrode body; a lid that seals the electrode body together with the exterior film, the exterior film is composed of a laminate including at least a barrier layer and a heat-sealable resin layer, the barrier layer has a ratio (R1 / R2) of an area average crystal grain size R1 (μm) to an area average crystal grain size R2 (μm) of 55% or more; The area average crystal grain size R1 (μm) is an area average crystal grain size (μm) obtained by performing crystal analysis by EBSD on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position where the heat-fusible resin layer of the packaging film is heat-fused to the lid, The area average crystal grain size R2 (μm) is an area average crystal grain size (μm) obtained by performing crystal analysis by EBSD on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position of the packaging film where the heat-fusible resin layer is not heat-fused, a step of sealing the electrode body with the outer casing, A method for manufacturing an electricity storage device.

[0295] Furthermore, as described above, the present disclosure provides the following aspects of the invention. Item 1B. An exterior packaging material for an electricity storage device composed of a laminate including at least a barrier layer and a heat-sealable resin layer, the barrier layer has a ratio (R1 / R2) of an area average crystal grain size R1 (μm) to an area average crystal grain size R2 (μm) of 55% or more; The area average crystal grain size R1 (μm) is an area average crystal grain size (μm) obtained by performing crystal analysis by EBSD on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position where the heat-fusion resin layer of the packaging material for an electricity storage device and a polypropylene plate are heat-fused under conditions such that the thickness of the heat-fusion resin layer is 20% or more and 80% or less, The area average crystal grain size R2 (μm) is an area average crystal grain size (μm) obtained by performing crystal analysis by EBSD on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position where the heat-fusible resin layer of the exterior material for an electricity storage device and the polypropylene plate are not heat-fused. Exterior material for energy storage devices. Item 2B: The packaging material for an electricity storage device according to Item 1B, wherein the barrier layer is formed of stainless steel, a steel plate, or an aluminum alloy. Item 3B: The packaging material for an electricity storage device according to Item 1B or 2B, further comprising an adhesive layer between the barrier layer and the heat-sealable resin layer. Item 4B: The packaging material for an electricity storage device according to any one of Items 1B to 3B, further comprising a substrate layer on the side of the barrier layer opposite to the thermally adhesive resin layer side. Item 5B: The packaging material for an electricity storage device according to Item 4B, further comprising an adhesive layer between the base layer and the barrier layer. Item 6B: The packaging material for an electricity storage device according to any one of Items 1B to 5B, wherein the packaging material for an electricity storage device has a Young's modulus of 6000 MPa or more. Item 7B. A method for producing an exterior material for an electricity storage device, The method includes a step of obtaining a laminate in which at least a barrier layer and a thermally adhesive resin layer are laminated, the barrier layer has a ratio (R1 / R2) of an area average crystal grain size R1 (μm) to an area average crystal grain size R2 (μm) of 55% or more; The area average crystal grain size R1 (μm) is an area average crystal grain size (μm) obtained by performing crystal analysis by EBSD on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position where the heat-fusion resin layer of the packaging material for an electricity storage device and a polypropylene plate are heat-fused under conditions such that the thickness of the heat-fusion resin layer is 20% or more and 80% or less, The area average crystal grain size R2 (μm) is an area average crystal grain size (μm) obtained by performing crystal analysis by EBSD on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position where the heat-fusible resin layer of the exterior material for an electricity storage device and the polypropylene plate are not heat-fused. A method for manufacturing an exterior material for an electricity storage device. Item 8B. An electricity storage device, in which an electricity storage device element including at least a positive electrode, a negative electrode, and an electrolyte is housed in a package formed from the exterior packaging material for an electricity storage device according to any one of Items 1B to 6B. [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 body 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 portion 80 Second sealing portion

Claims

1. An exterior packaging material for an electricity storage device, which is composed of a laminate including at least a barrier layer and a heat-sealable resin layer, the barrier layer has a ratio (R1 / R2) of an area average crystal grain size R1 (μm) to an area average crystal grain size R2 (μm) of 55% or more; The area average crystal grain size R1 (μm) is an area average crystal grain size (μm) obtained by performing crystal analysis by an EBSD method on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position where the heat-fusible resin layer of the packaging material for an electricity storage device and a polypropylene plate are heat-fused under conditions such that the thickness of the heat-fusible resin layer is 20% or more and 80% or less, The area average crystal grain size R2 (μm) is an area average crystal grain size (μm) obtained by performing crystal analysis by an EBSD method on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position where the heat-fusible resin layer of the packaging material for an electricity storage device and the polypropylene plate are not heat-fused, The exterior material for an electricity storage device is not subjected to cold forming, and is used to seal an electrode body by wrapping the exterior material for an electricity storage device around the electrode body.

2. The packaging material for an electricity storage device according to claim 1 , wherein the barrier layer is formed of stainless steel, a steel plate, or an aluminum alloy.

3. The packaging material for an electricity storage device according to claim 1 or 2, further comprising an adhesive layer between the barrier layer and the heat-sealable resin layer.

4. The packaging material for an electricity storage device according to claim 1 or 2, further comprising a substrate layer on the opposite side of the barrier layer from the heat-sealable resin layer side.

5. The packaging material for an electricity storage device according to claim 4 , further comprising an adhesive layer between the base material layer and the barrier layer.

6. The packaging material for an electricity storage device according to claim 1 or 2, wherein the packaging material for an electricity storage device has a Young's modulus of 6000 MPa or more.

7. A method for producing an exterior material for an electricity storage device, comprising: The method includes a step of obtaining a laminate in which at least a barrier layer and a thermally adhesive resin layer are laminated, the barrier layer has a ratio (R1 / R2) of an area average crystal grain size R1 (μm) to an area average crystal grain size R2 (μm) of 55% or more; The area average crystal grain size R1 (μm) is an area average crystal grain size (μm) obtained by performing crystal analysis by an EBSD method on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position where the heat-fusible resin layer of the packaging material for an electricity storage device and a polypropylene plate are heat-fused under conditions such that the thickness of the heat-fusible resin layer is 20% or more and 80% or less, The area average crystal grain size R2 (μm) is an area average crystal grain size (μm) obtained by performing crystal analysis by an EBSD method on a cross section obtained by cutting the barrier layer in a direction perpendicular to the rolling direction of the barrier layer and perpendicular to the surface of the barrier layer at a position where the heat-fusible resin layer of the packaging material for an electricity storage device and the polypropylene plate are not heat-fused, A method for producing an exterior material for an electricity storage device, which is not subjected to cold forming and is used to seal an electrode body by wrapping the exterior material for an electricity storage device around the electrode body.

8. An electricity storage device, comprising an electricity storage device element including at least a positive electrode, a negative electrode, and an electrolyte, housed in a package formed from the exterior packaging material for an electricity storage device according to claim 1 or 2.

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