Exterior film, power storage device, and method for manufacturing power storage device

Abstract

This exterior film is an exterior film used as an exterior body of a power storage device, and comprises at least a substrate layer, a barrier layer, and a hot-melt resin layer in this order. The barrier layer has a thickness of more than 40 μm and 200 μm or less. The exterior film has a bending stiffness of 2.0 gf·cm2 / cm or more.

Description

Exterior film, electricity storage device, and method for manufacturing electricity storage device

[0001] The present invention relates to an exterior film, an electricity storage device including this exterior film, and a method for manufacturing this electricity storage device.

[0002] Patent Document 1 discloses an example of an electricity storage device. This electricity storage device includes an electrode assembly and an exterior body that seals the electrode assembly. The exterior body includes an exterior film that wraps the electrode assembly and a lid that is joined to the exterior film. This electricity storage device is manufactured, for example, by housing the electrode assembly inside a cylindrical exterior film and closing the opening of the cylindrical exterior film with the lid. The side surface of the lid and the exterior film are joined, for example, by heat sealing.

[0003] Japanese Patent Application Laid-Open No. 2022-123686

[0004] In recent years, with the demand for larger electricity storage devices, the weight of the electrode assembly used in the electricity storage device has tended to increase. In the electricity storage device, for example, in the process of joining the lid and the exterior film, the load of the electrode assembly acts on the exterior film, which may cause the exterior film to bend. As a result, there is a risk that the electrode assembly in the electricity storage device may be displaced from a desired position.

[0005] An object of the present invention is to provide an exterior film that is prevented from being significantly warped, an electricity storage device including this exterior film, and a method for manufacturing this electricity storage device.

[0006] A packaging film according to a first aspect of the present invention is a packaging film used as an exterior body of an electricity storage device, and comprises at least a base layer, a barrier layer, and a heat-sealable resin layer in this order, the thickness of the barrier layer being greater than 40 μm and not more than 200 μm, and the bending stiffness of the packaging film being 2.0 gf cm ２ / cm or more.

[0007] An exterior film according to a second aspect of the present invention is the exterior film according to the first aspect, wherein the thickness of the exterior film is 100 μm or more.

[0008] A packaging film according to a third aspect of the present invention is the packaging film according to the first or second aspect, wherein the electricity storage device comprises an electrode body and an exterior body that seals the electrode body, and the exterior body includes the packaging film that wraps the electrode body, and a pair of lid bodies that are arranged on sides of the electrode body and are joined to the packaging film to seal the electrode body, and when a load-bearing test is conducted on a virtual electricity storage device manufactured using the packaging film, the virtual electricity storage device has a configuration similar to the electricity storage device and includes surfaces of the exterior body configured excluding the lid bodies, which are a first surface and a second surface that has an area smaller than the first surface, the pair of lid bodies that are joined to the packaging film, the electrode body or pseudo electrode body, and spacers that contact the pair of lid bodies and the electrode body or the pseudo electrode body. The electrode body or the pseudo electrode body and the spacer are sealed by the exterior film and the pair of lid bodies, the sum of the weight of the electrode body or the pseudo electrode body and the weight of the spacer is 500 g or more, and in the load-bearing test, of the elements constituting the virtual energy storage device, only one of the lid bodies joined to the exterior film is placed on a first support stand of 20 mm in height so that the first surface or the second surface is the lower surface, and of the elements constituting the virtual energy storage device, only the other lid body joined to the exterior film is placed on a second support stand of 20 mm in height, and after 5 minutes have elapsed since the virtual energy storage device was placed on the first support stand and the second support stand, the maximum deflection in the direction of gravity of the portion of the exterior film that constitutes the lower surface of the exterior body is 5 mm or less.

[0009] An exterior film according to a fourth aspect of the present invention is the exterior film according to any one of the first to third aspects, wherein the electricity storage device comprises an electrode body and an exterior body sealing the electrode body, the exterior body including the exterior film wrapping the electrode body, and a pair of lid bodies arranged on sides of the electrode body and sealed by being joined to the exterior film, and when a virtual electricity storage device is manufactured using the exterior film, the virtual electricity storage device has a configuration similar to the electricity storage device and includes surfaces of the exterior body configured excluding the lid body, which are a first surface and a second surface having an area smaller than that of the first surface, the pair of lid bodies joined to the exterior film, the electrode body or pseudo electrode body, the pair of lid bodies, and a spacer in contact with the electrode body or pseudo electrode body, and the electrode body or pseudo electrode body and the spacer are sealed by the exterior film and the pair of lid bodies, and in the virtual electricity storage device, an area of ​​the first surface or the second surface constituting a bottom surface is S (mm ２ ), the sum of the weight of the electrode body or the pseudo electrode body and the weight of the spacer is W (kg), the bending stiffness of the exterior film is X (gf cm ２ / cm), the value of the parameter Y calculated by the following formula is 5 or less: Y=-0.0000012·S·W·X+0.0000241·S·W.

[0010] A packaging film according to a fifth aspect of the present invention is the packaging film according to any one of the first to fourth aspects, wherein the electricity storage device comprises an electrode body and an exterior body sealing the electrode body, and the exterior body includes the packaging film that wraps the electrode body, and a pair of lid bodies that are arranged on sides of the electrode body and are joined to the packaging film to seal the electrode body, and when a load-bearing test is conducted on a virtual electricity storage device manufactured using the packaging film, the virtual electricity storage device has a configuration similar to the electricity storage device and includes surfaces of the exterior body configured excluding the lid bodies, which are a first surface and a second surface having an area smaller than that of the first surface, the pair of lid bodies joined to the packaging film, the electrode body or pseudo electrode bodies, and spacers in contact with the pair of lid bodies and the electrode body or the pseudo electrode bodies, and The pair of lid bodies seal the electrode body or the pseudo electrode body and the spacer, and the sum of the weight of the electrode body or the pseudo electrode body and the weight of the spacer is 500 g or more. In the load-bearing test, only one of the lid bodies joined to the exterior film among the elements constituting the virtual energy storage device is placed on a first support stand of 20 mm in height so that the first surface or the second surface is the underside, and only the other lid body joined to the exterior film among the elements constituting the virtual energy storage device is placed on a second support stand of 20 mm in height, and after 5 minutes have passed since the virtual energy storage device was placed on the first support stand and the second support stand, the maximum deflection amount in the direction of gravity of the part of the exterior film that constitutes the underside of the exterior body is smaller when the second surface is the underside than when the first surface is the underside.

[0011] An electricity storage device according to a sixth aspect of the present invention comprises an electrode body and an exterior body that seals the electrode body, the exterior body comprising an exterior film that wraps the electrode body and a lid that seals the electrode body together with the exterior film, the exterior film comprising at least a base layer, a barrier layer, and a heat-sealable resin layer in this order, the barrier layer having a thickness of more than 40 μm and not more than 200 μm, and the exterior film having a bending stiffness of 2.0 gf cm ２ / cm or more.

[0012] An electricity storage device according to a seventh aspect of the present invention is the electricity storage device according to the sixth aspect, wherein the exterior body comprises a first surface and a second surface that are surfaces of the exterior body configured excluding the lid body and have an area smaller than that of the first surface, and a pair of the lid bodies joined to the exterior film, the electricity storage device has spacers in contact with the pair of lid bodies and the electrode body, the electrode body and the spacers are sealed by the exterior film and the pair of lid bodies, and in the electricity storage device, an area of ​​the first surface or the second surface that configures a bottom surface is set to S (mm ２ ), the sum of the weight of the electrode body and the weight of the spacer is W (kg), the bending stiffness of the exterior film is X (gf cm ２ / cm), the value of the parameter Y calculated by the following formula is 5 or less: Y=-0.0000012·S·W·X+0.0000241·S·W.

[0013] A method for manufacturing an electricity storage device according to an eighth aspect of the present invention includes an electrode assembly and an exterior assembly that seals the electrode assembly, the exterior assembly including an exterior film that wraps the electrode assembly and a lid that seals the electrode assembly together with the exterior film, the exterior film including at least a base layer, a barrier layer, and a heat-sealable resin layer in this order, the barrier layer having a thickness of more than 40 μm and not more than 200 μm, and the exterior film having a bending stiffness of 2.0 gf cm ２ The method for manufacturing an electricity storage device includes a step of wrapping the electrode assembly with the exterior film.

[0014] According to the exterior film, the electricity storage device, and the method for manufacturing the electricity storage device of the present invention, it is possible to prevent the exterior film from being significantly deflected.

[0015] 6. A perspective view of an electricity storage device according to an embodiment. A diagram relating to a method for measuring the seal strength of a second sealed portion of the electricity storage device of FIG. 1A. A cross-sectional view showing the layer structure of an exterior film included in the electricity storage device of FIG. 1A. A diagram of the exterior film included in the electricity storage device of FIG. 1A in an unfolded state. A perspective view of a lid included in the electricity storage device of FIG. 1A. A flowchart showing an example of a manufacturing method for the electricity storage device of FIG. 1A. A diagram relating to a third step of the manufacturing method for the electricity storage device of FIG. 6. A diagram relating to a fourth step of the manufacturing method for the electricity storage device of FIG. 6. A diagram relating to a fifth step of the manufacturing method for the electricity storage device of FIG. 6. A diagram relating to a sixth step of the manufacturing method for the electricity storage device of FIG. 6. A diagram relating to an eighth step of the manufacturing method for the electricity storage device of FIG. 6. A cross-sectional view taken along line D11-D11 of FIG. 1A. A cross-sectional view relating to a load-bearing test using a hypothetical electricity storage device. A cross-sectional view showing a deflected state of the exterior film of the hypothetical electricity storage device of FIG. 12. A diagram showing an example of a state in which the electricity storage device of FIG. 1A is in use. A table showing specifications of exterior films of examples and comparative examples. A table showing measurement results of maximum deflection in a load-bearing test. 10 is a table showing calculation results of a parameter Y of a hypothetical power storage device in a load resistance test.

[0016] Hereinafter, an electricity storage device according to one embodiment of the present invention will be described with reference to the drawings. In this specification, a numerical range indicated by "to" means "greater than or equal to" or "less than or equal to." For example, the expression "2 to 15 mm" means 2 mm or more and 15 mm or less.

[0017] [Embodiments] <1-1. Configuration of Electricity Storage Device> Fig. 1A is a perspective view that schematically illustrates an electricity storage device 10 according to an embodiment. Fig. 1B is a diagram illustrating a method for measuring the seal strength of the second sealing portion 80 of the electricity storage device 10 of Fig. 1A. Fig. 2 is a cross-sectional view that illustrates an example of the layer configuration of an exterior film 50 included in the electricity storage device 10 of Fig. 1A. Fig. 3 is a diagram illustrating the exterior film 50 included in the electricity storage device 10 of Fig. 1A in an unfolded state. Fig. 4 is a perspective view of a lid 60 included in the electricity storage device 10 of Fig. 1A. In Fig. 1A, the direction of arrow UD indicates the thickness direction of the electricity storage device 10, the direction of arrow LR indicates the width direction of the electricity storage device 10, and the direction of arrow FB indicates the depth direction of the electricity storage device 10. The directions indicated by the arrows UDLRFB are common to the subsequent figures.

[0018] The energy storage device 10 includes an electrode body 20, an electrode terminal 30, and an exterior body 40. The electrode body 20 includes electrodes (positive and negative electrodes) 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 this embodiment, the shape of the electrode body 20 is approximately rectangular. Note that the term "approximately rectangular" 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.

[0019] In this embodiment, the power storage device 10 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 terminals 30 only need to be 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 configured to include a conductive material, the lid body 60 may also function as the electrode terminals 30. In this case, the lid body 60, which functions as an electrode terminal, may or may not protrude from the exterior body 40.

[0020] 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.

[0021] The exterior body 40 seals the electrode body 20. The exterior body 40 includes an exterior film 50 and a lid 60. The exterior film 50 wraps the electrode body 20. In the present embodiment, the exterior film 50 is wrapped around the electrode body 20. The lid 60 is disposed on the side of the electrode body 20 in the FB direction. In another example, the electrode body 20 may be housed inside an exterior film 50 configured in a cylindrical shape so that openings are formed at both ends in the FB direction, and the openings may be closed by the lid 60. In yet another example, the electrode body 20 connected to the lid 60 may be housed inside an exterior film 50 configured in a cylindrical shape so that openings are formed, and the openings may be closed by the lid 60.

[0022] The exterior body 40 has a pair of first surfaces 41A, 41B and a pair of second surfaces 42A, 42B. In the present embodiment, the pair of first surfaces 41A, 41B are substantially the same size. In the present embodiment, the pair of second surfaces 42A, 42B are substantially the same size. The pair of first surfaces 41A, 41B have a larger area than the pair of second surfaces 42A, 42B. 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 embodiment, the first surfaces 41A, 41B and the second surfaces 42A, 42B are surfaces of the exterior body 40 excluding the lid bodies 60.

[0023] For example, there is a method of forming a storage portion (recess) in the exterior film 50 through cold forming to accommodate the electrode assembly 20. However, it is not necessarily easy to form a deep storage portion using such a method. Attempting to form a deep storage portion (recess) by 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 exhibit 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.

[0024] As shown in FIG. 2 , the exterior film 50 is, for example, a laminate (laminate film) having a base material layer 51, a barrier layer 52, and a heat-sealable resin layer 53 in this order. The exterior film 50 may be composed of a laminate having at least the barrier layer 52 and the heat-sealable resin layer 53 in this order. In this laminate, the base material layer 51 is an optional layer, and the side of the barrier layer 52 opposite the heat-sealable resin layer 53 is the outermost layer, and the heat-sealable resin layer 53 is the innermost layer. In this embodiment, the exterior film 50 is configured to be prevented from deflecting significantly even when the load of the electrode assembly 20 is applied. From the viewpoint of preventing the exterior film 50 from deflecting significantly, the thickness of the exterior film 50 is preferably 100 μm or more, more preferably 110 μm or more, even more preferably 120 μm or more, even more preferably 140 μm or more, and even more preferably 155 μm or more. The outermost and innermost layers of the exterior film 50 may be heat-sealable resin layers 53. In this case, the exterior film 50 may encase the electrode body 20 and the lid body 60 by joining the outermost and innermost layers.

[0025] The substrate layer 51 included in the exterior film 50 is a layer that imparts heat resistance to the exterior film 50 and suppresses the occurrence of pinholes that may occur during processing or distribution. The substrate layer 51 is composed of, for example, at least one layer of a stretched polyester resin layer and a stretched polyamide resin layer. For example, by including at least one layer of a stretched polyester resin layer and a stretched polyamide resin layer in the substrate layer 51, the barrier layer 52 can be protected during processing of the exterior film 50 and breakage of the exterior film 50 can be suppressed. Furthermore, from the viewpoint of increasing the tensile elongation of the exterior film 50, the stretched polyester resin layer is preferably a biaxially stretched polyester resin layer, and the stretched polyamide resin layer is preferably a biaxially stretched polyamide resin layer. Furthermore, from the viewpoint of excellent puncture strength or impact strength, the stretched polyester resin layer is more preferably a biaxially stretched polyethylene terephthalate (PET) film, and the stretched polyamide resin layer is more preferably a biaxially stretched nylon (ONy) film. The substrate layer 51 may be composed of both a stretched polyester resin layer and a stretched polyamide resin layer. The thickness of the substrate layer 51 is preferably, for example, 5 to 300 μm, and more preferably 5 to 150 μm, from the viewpoint of film strength.

[0026] The barrier layer 52 is a layer that prevents at least moisture penetration. The barrier layer 52 is bonded to the substrate layer 51 via, for example, an adhesive layer 54. Examples of the barrier layer 52 include metal foils, vapor-deposited films, and resin layers with barrier properties. Vapor-deposited films include metal vapor-deposited films, inorganic oxide vapor-deposited films, and carbon-containing inorganic oxide vapor-deposited films. Resin layers include fluorine-containing resins such as polyvinylidene chloride, polymers based on chlorotrifluoroethylene (CTFE), polymers based on tetrafluoroethylene (TFE), polymers having fluoroalkyl groups, and polymers based on fluoroalkyl units, as well as ethylene-vinyl alcohol copolymers. The barrier layer 52 may also be a resin film having at least one of these vapor-deposited films and resin layers. The barrier layer 52 may be formed of multiple layers. The barrier layer 52 preferably includes a layer made of a metal material. Specific examples of the metal material 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. When a metal foil is used as the material constituting the barrier layer 52, the metal foil preferably includes at least one of an aluminum alloy foil and a stainless steel foil.

[0027] 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, aluminum alloy, titanium, titanium alloy, steel (including stainless steel), copper, copper alloy, nickel, nickel alloy, magnesium, magnesium alloy, niobium, and iron. 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 may be made of 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.

[0028] From the viewpoint of improving the formability or conformability of the exterior film 50, 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 formability or conformability, an aluminum alloy foil containing iron is preferable. In the aluminum alloy foil containing iron (100% by mass), the iron content is preferably 0.1 to 9.0% by mass, and more preferably 0.5 to 2.0% by mass. By having an iron content of 0.1% by mass or more, an exterior film 50 with better formability can be obtained. By having an iron content of 9.0% by mass or less, an exterior film 50 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, and the like may also be added as needed. Softening can be achieved by annealing or other methods. From the perspective of improving the mechanical strength of the exterior film 50, 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 exterior 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 JIS H4000:2017 A5052P-O.

[0029] Examples of the stainless steel foil include austenitic, ferritic, austenitic-ferritic, martensitic, and precipitation hardened stainless steel foils. Furthermore, from the viewpoint of providing an exterior film 50 with excellent formability, the stainless steel foil is preferably made of austenitic stainless steel.

[0030] Specific examples of austenitic stainless steels that form the stainless steel foil include SUS304, SUS301, and SUS316L, with SUS304 being particularly preferred.

[0031] From the viewpoint of preventing the exterior film 50 from being significantly deflected even when the load of the electrode assembly 20 acts on the exterior film 50, the minimum thickness of the barrier layer 52 is greater than 40 μm. The minimum thickness of the barrier layer 52 is preferably 50 μm or greater, more preferably 60 μm or greater, and even more preferably 80 μm or greater. From the viewpoint of conformability to the electrode assembly 20 and the lid body 60 when the electrode assembly 20 and the lid body 60 are wrapped, the maximum thickness of the barrier layer 52 is 200 μm. The maximum thickness of the barrier layer 52 is preferably 180 μm or less, more preferably 150 μm or less, and even more preferably 120 μm or less. The thickness of the barrier layer 52 ranges from greater than 40 μm to 200 μm or less. The thickness of the barrier layer 52 is preferably in the range of more than 40 μm and not more than 180 μm, more than 40 μm and not more than 150 μm, more than 40 μm and not more than 120 μm, 50 μm or more and not more than 200 μm, 50 μm or more and not more than 180 μm, 50 μm or more and not more than 150 μm, 50 μm or more and not more than 120 μm, 60 μm or more and not more than 200 μm, 60 μm or more and not more than 180 μm, 60 μm or more and not more than 150 μm, 60 μm or more and not more than 120 μm, 80 μm or more and not more than 200 μm, 80 μm or more and not more than 180 μm, 80 μm or more and not more than 150 μm, or 80 μm or more and not more than 120 μm.

[0032] Furthermore, when the barrier layer 52 is an aluminum foil, it is preferable that a corrosion-resistant coating be provided on at least the surface opposite the substrate layer 51 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 performing, for example, a hydrothermal conversion treatment such as boehmite treatment, a chemical conversion treatment, an anodizing treatment, a plating treatment of nickel or chromium, or a corrosion prevention treatment such as applying a coating agent on the surface of the barrier layer 52. Specifically, the corrosion-resistant coating refers to a coating that improves the acid resistance of the barrier layer 52 (acid-resistant coating), a coating that improves the alkali resistance of the barrier layer 52 (alkali-resistant coating), or the like. The corrosion-resistant coating may be formed by one type of treatment or a combination of two or more types. Furthermore, the barrier layer 52 may be formed not only as a single layer but also as a multi-layer. Furthermore, among these treatments, hydrothermal conversion treatment and anodizing treatment are treatments in which the surface of the metal foil is dissolved with a treatment agent to form a metal compound with excellent corrosion resistance. Note that these treatments may also be included in the definition of chemical conversion treatment. Furthermore, if the barrier layer 52 has a corrosion-resistant coating, the corrosion-resistant coating is also included in the barrier layer 52.

[0033] The corrosion-resistant coating prevents delamination between the barrier layer 52 (e.g., aluminum alloy foil) and the substrate layer 51 during molding of the exterior film 50, prevents dissolution and corrosion of the surface of the barrier layer 52 due to hydrogen fluoride produced by a reaction between an electrolyte and water, and in particular prevents dissolution and corrosion of aluminum oxide present on the surface of the barrier layer 52 when the barrier layer 52 is an aluminum alloy foil, and also improves the adhesion (wettability) of the surface of the barrier layer 52, thereby preventing delamination between the substrate layer 51 and the barrier layer 52 during heat sealing and between the substrate layer 51 and the barrier layer 52 during molding.

[0034] The heat-sealable resin layer 53 is bonded to the barrier layer 52 via, for example, an adhesive layer 55. The heat-sealable resin layer 53 included in the exterior film 50 is a layer that provides heat-sealing properties to the exterior film 50. Examples of the heat-sealable resin layer 53 include resin films made of polyester resins such as polyethylene terephthalate resins and polybutylene terephthalate resins, polyolefin resins such as polyethylene resins and polypropylene resins, or acid-modified polyolefin resins obtained by graft-modifying these polyolefin resins with an acid such as maleic anhydride. From the standpoints of sealability and strength, the thickness of the heat-sealable resin layer 53 is preferably, for example, 20 to 300 μm, and more preferably 40 to 150 μm.

[0035] The exterior film 50 preferably has one or more layers having a buffer function (hereinafter referred to as "buffer layer") outside the heat-sealable resin layer 53, more preferably outside the barrier layer 52. The buffer layer may be laminated on the outside of the base material layer 51, or the base material layer 51 may also function as a buffer layer. When the exterior film 50 has multiple buffer layers, the multiple buffer layers may be adjacent to each other, or may be laminated with the base material layer 51, the barrier layer 52, or the like interposed therebetween.

[0036] The material constituting the buffer layer can be arbitrarily selected from materials having cushioning properties. Examples of the material having cushioning properties include rubber, nonwoven fabric, and foam sheet. Examples of rubber include natural rubber, fluororubber, and silicone rubber. The rubber hardness is preferably about 20 to 90. The material constituting the nonwoven fabric is preferably a material having excellent heat resistance. When the buffer layer is made of nonwoven fabric, the lower limit of the thickness of the buffer layer is preferably 100 μm, more preferably 200 μm, and even more preferably 1000 μm. When the buffer layer is made of nonwoven fabric, the upper limit of the thickness of the buffer layer is preferably 5000 μm, and even more preferably 3000 μm. The thickness of the buffer layer is preferably in the range of 100 μm to 5000 μm, 100 μm to 3000 μm, 200 μm to 5000 μm, 200 μm to 3000 μm, 1000 μm to 5000 μm, or 1000 μm to 3000 μm, with the most preferred range being 1000 μm to 3000 μm.

[0037] When the buffer layer is made of rubber, the lower limit of the buffer layer thickness is preferably 0.5 mm, more preferably 1.0 mm. When the buffer layer is made of rubber, the upper limit of the buffer layer thickness is preferably 10 mm, more preferably 5.0 mm, and even more preferably 2.0 mm. When the buffer layer is made of rubber, the preferred ranges of the buffer layer thickness are 1.0 mm to 2.0 mm, 1.0 mm to 5.0 mm, 1.0 mm to 10 mm, 0.5 mm to 2.0 mm, 0.5 mm to 5.0 mm, and 0.5 mm to 10 mm.

[0038] When the exterior film 50 has a buffer layer, the buffer layer functions as a cushion, thereby preventing the exterior film 50 from being damaged by impact when the energy storage device 10 is dropped or by handling during manufacturing of the energy storage device 10.

[0039] In order to prevent the exterior film 50 from being significantly bent even when a load is applied to the exterior film 50, the minimum bending stiffness of the exterior film 50 is set to 2.0 gf cm ２The minimum bending stiffness of the exterior film 50 is 3.0 gf cm ２ / cm or more, and 4.0 gf cm ２ / cm or more, more preferably 5.0 gf cm2 / cm or more, and even more preferably 6.0 gf cm ２ From the viewpoint of conformability to the electrode body 20 and the lid body 60 when the exterior film 50 is wrapped around the electrode body 20 and the lid body 60, the maximum bending stiffness of the exterior film 50 is preferably 40 gf cm / cm or less. The maximum bending stiffness of the exterior film 50 is preferably 30 gf cm ２ / cm or less, and more preferably 25 gf cm ２ / cm or less, and more preferably 20 gf cm ２ The preferred range of the bending stiffness of the exterior film 50 is 2.0 gf cm ２ / cm or more 40gf・cm ２ / cm or less, 2.0gf・cm ２ / cm or more 30gf・cm ２ / cm or less, 2.0gf・cm ２ / cm or more 25gf・cm ２ / cm or less, 2.0gf・cm ２ / cm or more 20gf・cm ２ / cm or less, 3.0gf・cm ２ / cm or more 40gf・cm ２ / cm or less, 3.0gf・cm ２ / cm or more 30gf・cm ２ / cm or less, 3.0gf・cm ２ / cm or more 25gf・cm ２ / cm or less, 3.0gf・cm ２ / cm or more 20gf・cm ２ / cm or less, 4.0gf・cm ２ / cm or more 40gf・cm ２ / cm or less, 4.0gf・cm ２ / cm or more 30gf・cm ２ / cm or less, 4.0gf・cm ２ / cm or more 25gf・cm ２ / cm or less, 4.0gf・cm２ / cm or more 20gf・cm ２ / cm or less, 5.0gf・cm ２ / cm or more 40gf・cm ２ / cm or less, 5.0gf・cm ２ / cm or more 30gf・cm ２ / cm or less, 5.0gf・cm ２ / cm or more 25gf・cm ２ / cm or less, 5.0gf・cm ２ / cm or more 20gf・cm ２ / cm or less, 6.0gf・cm ２ / cm or more 40gf・cm ２ / cm or less, 6.0gf・cm ２ / cm or more 30gf・cm ２ / cm or less, 6.0gf・cm ２ / cm or more 25gf・cm ２ / cm or less, or 6.0 gf cm ２ / cm or more 20gf・cm ２ / cm or less. The bending stiffness of the exterior film 50 is measured as follows. The exterior film 50 is cut into a rectangle with a width of 80 mm and a length of 20 mm to obtain a test sample. The width is the direction perpendicular to the flow direction of the exterior film 50 during film production, i.e., the TD (Transverse Direction). The length is the flow direction of the exterior film 50 during film production, i.e., the MD (Machine Direction). The bending stiffness (gf cm) of the obtained test sample is measured at a temperature of 23°C and a relative humidity of 50% using a commercially available bending stiffness measuring machine (pure bending tester (JTC-911BT, manufactured by SMT Corporation)). 2 The test sample is fixed to two clamps so that the edge of the 80 mm wide test sample coincides with the clamp axis direction. The measurement conditions are: curvature change rate: 0.1 / cm·sec, clamp interval: 1 cm, maximum curvature: 2.5 cm -1 The average value of the bending stiffness of the five test samples is taken as the bending stiffness of the exterior film 50.

[0040] The lid body 60 is, for example, plate-shaped and is made up of, for example, a resin material. Here, "made up of a resin material" means that, when the entire material constituting the lid body 60 is taken as 100% by mass, the content of the resin material is 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. In other words, the material constituting the lid body 60 can contain materials other than the resin material in addition to the resin material.

[0041] Specific examples of the resin 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 version of the copolymer. Among these, the resin material is preferably a heat-sealable resin such as polyester or polyolefin, and more preferably polyolefin. When the resin material is a resin, the lid 60 may be molded by any molding method.

[0042] The resin material contained in the material constituting the lid 60 is preferably an olefin-based random copolymer, more preferably a resin containing a polyolefin skeleton as a main component, even more preferably a polyolefin as a main component, and even more preferably a polypropylene as a main component. The polyolefin may be an acid-modified polyolefin. The resin material contained in the material constituting the lid 60 preferably contains multiple types of amide-based lubricants. Furthermore, the resin material contained in the material constituting the lid 60 preferably contains multiple types of amide-based lubricants that further contain unsaturated fatty acid amides in addition to saturated fatty acid amides. The resin material contained in the material constituting the lid 60 may be a polyolefin resin to which a propylene-based elastomer having a melting point higher than 150°C has been added.

[0043] 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 / decanedicarboxylate). Among these, polybutylene terephthalate is preferred as the resin material from the viewpoint of enhancing heat resistance and pressure resistance.

[0044] Specific examples of polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; polypropylenes such as homopolypropylene, polypropylene block copolymers (e.g., block copolymers of propylene and ethylene), and polypropylene random copolymers (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.

[0045] 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.

[0046] The melt mass flow rate 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, and more preferably in the range of 5 g / 10 min to 80 g / 10 min. The melt mass flow rate is measured in accordance with JIS K7210-1:2014. The measurement temperature for the melt mass flow rate is 230°C.

[0047] The lid 60 is made up of a conductive material. The phrase "made up of 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.

[0048] 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, aluminum alloy, nickel, copper, or 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 copper plated with nickel. The material constituting the lid body 60 may include recycled metal material. When the lid body 60 is made of a conductive material, the lid body 60 also functions as the electrode terminal 30, so the electrode terminal 30 can be omitted from the electricity storage device 10.

[0049] When the lid body 60 is made of a conductive material, at least a portion of the lid body 60 may be covered with a covering body. The lid body 60 may be joined to the heat-sealable resin layer 53 of the exterior film 50 via the covering body. The covering body is preferably made of a resin material. The definition of "made of a resin material" regarding the covering body is the same as that for the lid body 60.

[0050] 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 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 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 .

[0051] 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.

[0052] The adhesive film preferably has adhesive properties. When the second sealing portion 100B 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 tackifying resin into the heat-sealable resin layer of the adhesive film, adhesive properties can be imparted to the adhesive film. Examples of the tackifying resin include amorphous polyolefins. Examples of amorphous polyolefins include amorphous polypropylene and copolymers of amorphous propylene and other α-olefins. The content of the tackifying resin relative to the base material constituting the heat-sealable resin is preferably 10 to 20% by weight or less.

[0053] As shown in FIG. 4 , the lid body 60 has a first surface 61, a second surface 62, and a lid joint portion 63. The first surface 61 faces the electrode assembly 20. The second surface 62 is the surface opposite to the first surface 61. The lid joint portion 63 connects the first surface 61 and the second surface 62 and is joined to the thermally adhesive resin layer 53 of the exterior film 50. The lid joint portion 63 includes a first joint surface 63A, a second joint surface 63B, a third joint surface 63C, and a fourth joint surface 63D. The first joint surface 63A forms the top surface of the lid body 60. The first joint surface 63A extends in a first direction (in this embodiment, the LR direction) when viewed from the front of the lid body 60. The second joint surface 63B and the third joint surface 63C are connected to the first joint surface 63A and form side surfaces of the lid body 60. The second bonding surface 63B and the third bonding surface 63C extend in a second direction (UD direction in this embodiment) that intersects with the first direction in a front view of the lid 60. In this embodiment, the first direction and the second direction are orthogonal in a front view of the lid 60. The first direction and the second direction do not have to be orthogonal in a front view of the lid 60. The fourth bonding surface 63D forms the lower surface of the lid 60. The fourth bonding surface 63D extends in the first direction (LR direction in this embodiment) in a front view of the lid 60.

[0054] When the lid body 60 is plate-shaped, it is preferable that the lid body 60 have a certain thickness in the FB 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 plate-shaped, it is preferable that the lid joint portion 63 of the lid body 60 have a certain thickness in the FB direction so that the lid joint portion 63 of the lid body 60 can be suitably joined to the exterior film 50 when forming the second sealing portion 80. The minimum thickness of the lid body 60 in the FB direction is 1.0 mm, more preferably 3.0 mm, and even more preferably 4.0 mm. The maximum thickness of the lid body 60 in the FB direction is, for example, 20 mm, more preferably 15 mm, and even more preferably 10 mm. The maximum thickness of the lid body 60 in the FB direction may be 20 mm or more. Preferred ranges for the thickness of the material constituting the lid body 60 are 1.0 mm to 20 mm, 1.0 mm to 15 mm, 1.0 mm to 10 mm, 3.0 mm to 20 mm, 3.0 mm to 15 mm, 3.0 mm to 10 mm, 4.0 mm to 20 mm, 4.0 mm to 15 mm, and 4.0 mm to 10 mm. In this embodiment, when the lid body 60 is described as being plate-shaped, this does not include embodiments in which the lid body 60 is composed 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 region of the lid body 60. When the thickness of the lid body 60 varies depending on the region, the thickness of the lid body 60 is the thickness of the thickest portion.

[0055] The lid joint portion 63 further includes boundaries 64, 65, 66, and 67. The boundary 64 is the boundary between the first joint surface 63A and the second joint surface 63B. The boundary 65 is the boundary between the first joint surface 63A and the third joint surface 63C. The boundary 66 is the boundary between the fourth joint surface 63D and the second joint surface 63B. The boundary 67 is the boundary between the fourth joint surface 63D and the third joint surface 63C. The shapes of the boundaries 64 to 67 may be angular, or may be rounded by applying a rounding process. In this embodiment, the boundaries 64 to 67 are angular.

[0056] In this embodiment, the lid body 60 has a through hole 60X formed therein, into which the electrode terminal 30 is inserted. The through hole 60X penetrates the first surface 61 and the second surface 62. When the electrode body 20 is stored, the electrode terminal 30 passes through the through hole 60X formed in the lid body 60 and protrudes to the outside of the exterior body 40. A small gap between the through hole 60X of the lid body 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 body 60 and the exterior film 50, or may protrude from a first sealing portion 70, which will be described later. 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 60X formed therein.

[0057] In this embodiment, the first sealing portion 70 is formed by wrapping the exterior film 50 around the electrode body 20 and heat-sealing the opposing surfaces of the exterior film 50 (heat-fusible resin layer 53).

[0058] The first sealed portion 70 is formed by heat-sealing a portion of the exterior film 50 including the first edge 50A and a portion of the exterior film 50 including the second edge 50B shown in FIG. 3 . 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 on the exterior body 40 can be selected arbitrarily. In this embodiment, the base 70X of the first sealed portion 70 is preferably located on the edge 43 at the boundary between the first surface 41A and the second surface 42A of the exterior body 40. The base 70X of the first sealed portion 70 may be located on any surface of the exterior body 40. In this embodiment, 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 second surface 42A of the exterior body 40 or toward the first surface 41A.

[0059] In this embodiment, the heat-sealing resin layer 53 of the exterior film 50 and the lid joint 63 of the lid 60 are joined together by, for example, heat sealing, thereby forming the second sealed portion 80. Hereinafter, the seal strength between the heat-sealing resin layer 53 of the exterior film 50 and the lid joint 63 of the lid 60 may be referred to as the seal strength (joint strength) of the second sealed portion 100B. Note that the seal strength of the second sealed portion 80 is the seal strength between the heat-sealing resin layer 53 and the lid 60 at the long side portion of the lid joint 63, i.e., the lid joint 63 extending in the LR (width) direction in FIG. 1A . Note that the exterior film 50 and the lid 60 can be joined together by any method, such as welding.

[0060] The seal strength of the second sealing portion 80 is measured as follows. First, a slit is formed in the portion of the exterior film 50 that constitutes the first surface 41A of the exterior body 40, forming three strip-shaped members 41X, 41Y, and 41Z aligned in the LR direction (see the two-dot chain lines in FIG. 1B ). The width of the three strip-shaped members 41X, 41Y, and 41Z in the LR direction is 15 mm. The ends of the strip-shaped members 41X, 41Y, and 41Z are joined to the lid body 60 at the second sealing portion 80. The length of the lid body 60 in the LR direction is 45 mm or more. Next, the end of each of the strip-shaped members 41X, 41Y, and 41Z opposite the end joined to the lid body 60 is pulled upward in the UD direction (away from the first surface 41B), thereby measuring the seal strength of each of the strip-shaped members 41X, 41Y, and 41Z. In this embodiment, the seal strength of the second sealing portion 80 is the average value of the seal strengths of the strip-shaped members 41X, 41Y, and 41Z. When the lid body 60 has a length in the LR direction of less than 45 mm, three strip-shaped members with an arbitrary width X mm, less than 15 mm, are formed, and the seal strengths of the three strip-shaped members are measured in the same manner as when the lid body 60 has a length in the LR direction of 45 mm or more. The obtained seal strengths are each divided by the arbitrary width X mm and multiplied by 15 to convert them to the seal strengths of the three strip-shaped members with a 15 mm width. The seal strength of the second sealing portion 80 is the average value of the seal strengths of the three strip-shaped members converted to a 15 mm width. Note that when the lid body 60 is divided into multiple parts including long and short sides, the seal strength of the second sealing portion 80 is the seal strength at the long sides of the lid joints 63 of the multiple parts.

[0061] From the viewpoint of suitably maintaining the state in which the electrode assembly 20 is sealed by the exterior body 40, the seal strength of the second sealing unit 80 is preferably 40 N / 15 mm or more, more preferably 50 N / 15 mm or more, even more preferably 60 N / 15 mm or more, even more preferably 70 N / 15 mm or more, and even more preferably 85 N / 15 mm or more. When the seal strength of the second sealing unit 80 is 40 N / 15 mm or more, the state in which the electrode assembly 20 is sealed by the exterior body 40 is suitably maintained even after the power storage device 10 has been used for, for example, several years (less than 10 years). When the seal strength of the second sealing unit 80 is 85 N / 15 mm or more, the state in which the electrode assembly 20 is sealed by the exterior body 40 is suitably maintained even after the power storage device 10 has been used for, for example, 10 years or more. The seal strength of the second sealing portion 80 is preferably 500 N / 15 mm or less, more preferably 300 N / 15 mm, and even more preferably 150 N / 15 mm. Preferred ranges for the seal strength of the second sealing portion 80 are 40 N / 15 mm to 500 N / 15 mm, 50 N / 15 mm to 500 N / 15 mm, 60 N / 15 mm to 500 N / 15 mm, 70 N / 15 mm to 500 N / 15 mm, 85 N / 15 mm to 500 N / 15 mm, 40 N / 15 mm to 300 N / 15 mm, 50 N / 15 mm to 300 N / 15 mm, 60 N / 15mm to 300N / 15mm, 70N / 15mm to 300N / 15mm, 85N / 15mm to 300N / 15mm, 40N / 15mm to 150N / 15mm, 50N / 15mm to 150N / 15mm, 60N / 15mm to 150N / 15mm, 70N / 15mm to 150N / 15mm, or 85N / 15mm to 150N / 15mm.

[0062] 5 is a flowchart showing an example of a method for manufacturing the power storage device 10. The method for manufacturing the power storage device 10 includes, for example, a first step, a second step, a third step, a fourth step, a fifth step, a sixth step, a seventh step, and an eighth step. The first step to the eighth step are performed, for example, by a manufacturing apparatus for the power storage device 10. At least some of the first step to the eighth step may be performed by an operator. Note that the first step to the eighth step are names of the steps in the method for manufacturing the power storage device 10 defined for convenience, and do not necessarily refer to the order of the steps. The order of the following steps can be changed as desired.

[0063] In the first process of step S11, the manufacturing apparatus places a pair of lid units 60Z to which the electrode terminals 30 are joined, on the electrode body 20, and electrically connects the electrode terminals 30 to the electrode body 20. Note that in the first process, the lid body 60 may be joined to the electrode terminals 30 electrically connected to the electrode body 20.

[0064] The second step of step S12 is performed after the first step. In the second step, the manufacturing apparatus wraps the electrode assembly 20 and the lid unit 60Z in an exterior film 50. Note that in the second step, an exterior film 50 having a larger area than the exterior film 50 of the finished power storage device 10 is used in order to form a gas pocket 300, which will be described later. In the second step, the manufacturing apparatus wraps the exterior film 50 around the electrode assembly 20 and the lid body 60 while applying tension to the exterior film 50, while restricting the movement of the electrode assembly 20 and the lid body 60 with 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 over the exterior film 50 while the exterior film 50 is being pulled in order to remove wrinkles in the exterior film 50 .

[0065] The third process of step S13 is performed after the second process. As shown in Fig. 6, in the third process, the manufacturing apparatus forms the first FB-direction seal portion 71 having an unsealed portion 71Z in the center. Note that the hatched portion in Fig. 6 indicates an example of the region where the first FB-direction seal portion 71 is formed.

[0066] The fourth step of step S14 is performed after the third step. As shown in Fig. 7 , in the fourth step, the manufacturing apparatus forms a second short side seal portion 82. The second short side seal portion 82 is a portion where the second bonding surface 63B and the third bonding surface 63C of the lid body 60 are heat-sealed to the exterior film 50. The hatched portion in Fig. 7 indicates an example of the region where the second short side seal portion 82 is formed.

[0067] The fifth step of step S15 is performed after the fourth step. As shown in Fig. 8 , in the fifth step, the manufacturing apparatus forms a second long side seal portion 81. The second long side seal portion 81 is a portion where the first bonding surface 63A and the fourth bonding surface 63D of the lid body 60 are heat-sealed to the exterior film 50. The hatched portion in Fig. 8 indicates an example of the region where the second long side seal portion 81 is formed.

[0068] The sixth step of step S16 is performed after the fifth step. As shown in FIG. 9 , in the sixth step, the manufacturing apparatus forms the first LR-direction seal portion 72. In the sixth step, the first LR-direction seal portion 72 is formed so as to partially overlap the first FB-direction seal portion 71 in the portion including the side 43. Note that the hatched portion in FIG. 9 indicates an example of the region where the first LR-direction seal portion 72 is formed. Completion of the sixth step results in the completion of a gas pocket 300 having a larger area in a plan view than the first sealing portion 70 of the finished power storage device 10.

[0069] The seventh step of step S17 is performed after the sixth step. In the seventh step, the manufacturing apparatus injects an electrolytic solution through the opening of the gas pocket 300. As shown in FIG. 10 , after the electrolytic solution is injected, the edges of the gas pocket 300, including the opening, are joined to form a pocket sealing portion 310. An aging step is performed after the seventh step. Gas generated by the aging step is accumulated in the gas pocket 300. The gas accumulated in the gas pocket 300 is discharged through an opening formed by cutting a portion of the gas pocket 300. The gas pocket 300 is cut, for example, along the dashed dotted line XA shown in FIG. 10 to form an opening for discharging the gas.

[0070] The eighth step of step S18 is performed after the seventh step and after the aging step is completed. In the eighth step, the manufacturing apparatus forms the first sealing portion 70. In the eighth step, the first FB-direction seal portion 71 may or may not be resealed.

[0071] <1-3. Load-bearing Test of a Virtual Energy Storage Device> In recent years, the weight of the electrode assembly 20 has tended to increase due to demand for larger energy storage devices 10. As a result, the load of the electrode assembly 20 acts on the exterior film 50, which can cause the exterior film 50 to warp. In a typical example, during the steps of forming the first sealing portion 70 and the second sealing portion 80, such as the third to sixth steps of the manufacturing method for the energy storage device 10, the load of the electrode assembly 20 acts on the portion of the exterior film 50 that constitutes the bottom surface of the exterior body 40, which is likely to cause a large warp in the exterior film 50. The inventors of the present application manufactured a virtual energy storage device 10X using the exterior film 50 and conducted a load-bearing test on the virtual energy storage device 10X. The load-bearing test was conducted in an environment with a temperature of 23°C and a relative humidity of 50%.

[0072] Fig. 11 is a cross-sectional view taken along line D11-D11 in Fig. 1. That is, Fig. 11 is a cross-sectional view of the power storage device 10. Fig. 12 is a cross-sectional view relating to a load-bearing test using a virtual power storage device 10X. As shown in Fig. 12, the virtual power storage device 10X has a similar configuration to the power storage device 10. In the following, for ease of explanation, the same reference numerals are used to denote, among the elements constituting the virtual power storage device 10X, elements that are the same as the elements constituting the power storage device 10.

[0073] The differences between the virtual energy storage device 10 and the virtual energy storage device 10 are as follows: The virtual energy storage device 10X has a pseudo electrode body 20X instead of the electrode body 20. The pseudo electrode body 20X is a block having the same outer shape as the electrode body 20. The pseudo electrode body 20X is made of aluminum. The virtual energy storage device 10 may have the electrode body 20. The virtual energy storage device 10 does not have an electrode terminal 30. The virtual energy storage device 10 does not have an electrolyte inside the exterior body 40. The interior of the exterior body 40 of the virtual energy storage device 10 is not in a vacuum state. The lid body 60 of the virtual energy storage device 10 does not have a through-hole 60X. In the virtual energy storage device 10X, a spacer 90 is arranged between the first surface 61 of the lid body 60 and the electrode body 20 or the pseudo electrode body 20X. The material making up the spacer 90 is, for example, a resin material. The resin material is, for example, a thermoplastic resin such as polyester, polyolefin, polyamide, epoxy resin, acrylic resin, fluororesin, polyurethane, silicone resin, or phenolic resin, or a modified version of these resins. The spacer 90 is a rectangular parallelepiped. The spacer 90 is in contact with the first surface 61 of the lid 60 and the electrode body 20 or the pseudo electrode body 20X, but is not bonded to the first surface 61 of the lid 60 and the electrode body 20 or the pseudo electrode body 20X.

[0074] The specifications of the hypothetical power storage device 10X are as follows: the electrode body 20 or pseudo electrode body 20X has a dimension of 350 mm in the FB direction, a dimension of 30 mm in the UD direction, a dimension of 100 mm in the LR direction, and a weight of 2.3 kg. In another example, the electrode body 20 or pseudo electrode body 20X has a dimension of 580 mm in the FB direction, a dimension of 30 mm in the UD direction, a dimension of 100 mm in the LR direction, and a weight of 4.5 kg.

[0075] The lid body 60 has a dimension of 5 mm in the FB direction, a dimension of 30 mm in the UD direction, a dimension of 100 mm in the LR direction, and a weight of 14 g.

[0076] The spacer 90 has a dimension of 5 mm in the FB direction, a dimension of 15 mm in the UD direction, a dimension of 30 mm in the LR direction, and a weight of 2 g. The volume of one spacer 90 is smaller than the volume of one lid body 60. The static friction coefficient of the spacer 90 is 0.20 or more.

[0077] The clearance CA between the first surface 61 of the lid 60 and the electrode body 20 or the pseudo electrode body 20X is 5 mm.

[0078] The seal strength of the first sealing portion 70 is 150 N / 15 mm. The seal strength of the second sealing portion 80 is 100 N / 15 mm.

[0079] In the load-bearing test, of the elements constituting the hypothetical power storage device 10X, only one lid body 60 joined to the exterior film 50 is placed on a first support stand 110 at a height of 20 mm from the installation surface 200, so that the first surfaces 41A, 41B or the second surfaces 42A, 42B of the exterior body 40 face downward. Furthermore, of the elements constituting the hypothetical power storage device 10X, only the other lid body 60 joined to the exterior film 50 is placed on a second support stand 120 at a height of 20 mm from the installation surface 200. Five minutes after the hypothetical power storage device 10X is placed on the first support stand 110 and the second support stand 120, the maximum deflection TX (mm) in the vertical direction of the portion of the exterior film 50 that constitutes the lower surface of the exterior body 40 is measured.

[0080] 13, the load of the electrode body 20 or pseudo electrode body 20X acts on the contact point PA with the corner of the underside of the electrode body 20 or pseudo electrode body 20X, and the central portion of the exterior film 50 in the F-B direction is deflected starting from the contact point PA. In a typical example, the exterior film 50 deflects the most in the center in the F-B direction. The maximum deflection amount TX can be calculated using the following equation (1) using the distance LA and the distance LB.

[0081] Maximum deflection TX (mm) = distance LA (mm) - distance LB (mm) (1)

[0082] The distance LA in formula (1) is the height of the first support stand 110 and the second support stand 120, i.e., the vertical distance between the installation surface 200 facing the contact point PA and the exterior film 50. The distance LB is the distance between the installation surface 200 and the most warped part of the part of the exterior film 50 that forms the underside of the exterior body 40, five minutes after the hypothetical power storage device 10X is placed on the first support stand 110 and the second support stand 120.

[0083] From a first viewpoint, when a load-bearing test is carried out using a hypothetical electricity storage device 10X, it is preferable that the maximum deflection amount TX of the exterior film 50 measured is 5 mm or less.

[0084] From a second perspective, in a hypothetical power storage device 10X, the area of ​​the first surfaces 41A, 41B or the second surfaces 42A, 42B constituting the bottom surface is defined as S (mm ２ ), the sum of the weight of the electrode body 20 or the pseudo electrode body 20X and the weight of the spacer 90 is W (kg), and the bending stiffness of the exterior film 50 is X (gf cm ２ / cm), the exterior film 50 preferably has a parameter Y value of 5 or less calculated by the following formula (2):

[0085] Y=-0.0000012・S・W・X+0.0000241・S・W...(2)

[0086] 14 is a diagram showing an example of a state in which the power storage device 10 is used. As shown in Fig. 14, in a typical example, the power storage device 10 is used while being disposed so that the second surfaces 42A, 42B, which have smaller areas than the first surfaces 41A, 41B and the second surfaces 42A, 42B, are in contact with the installation surface. Therefore, from the third viewpoint, when a load-bearing test is conducted using a hypothetical power storage device 10X, it is preferable that the maximum deflection amount TX of the exterior film 50 be smaller when the second surfaces 42A, 42B are the bottom surfaces than when the first surfaces 41A, 41B are the bottom surfaces.

[0087] <1-4. Effects of the Exterior Film> According to the exterior film 50 of this embodiment, the thickness of the barrier layer 52 is more than 40 μm and not more than 200 μm, and the bending stiffness of the exterior film 50 is 2.0 gf·cm ２ / cm or more. Therefore, the exterior film 50 is prevented from being significantly deflected.

[0088] [2. Modifications] The above-described embodiments are examples of possible forms of the exterior film, electricity storage device, and method for manufacturing an electricity storage device according to the present invention, and are not intended to limit the forms. The exterior film, electricity storage device, and method for manufacturing an electricity storage device according to the present invention may take forms different from those exemplified in the embodiments. Examples include forms in which part of the configuration of the embodiments is replaced, changed, or omitted, or forms in which a new configuration is added to the embodiments. Some examples of modifications of the embodiments are shown below. Note that the following modifications can be combined with each other as long as there is no technical contradiction.

[0089] <2-1. First Modification> In the above embodiment, the exterior film 50 of the power storage device 10 may protrude outward in the FB direction beyond at least one of the two lid bodies 60. The electrode body 20 is sealed by closing the portion of the exterior film 50 that protrudes outward beyond the lid body 60. The portion of the exterior film 50 that protrudes beyond the lid body 60 may be folded like a Goebel-top pouch or a brick pouch. In the first modification, the length of the electrode terminal in the FB direction is preferably such that it is exposed from the portion of the exterior film 50 that protrudes outward beyond the lid body 60.

[0090] <2-2. Second Modification> In the above embodiment, the exterior body 40 may not have one of the two lid bodies 60. In this modification, in the FB direction, in the portion of the exterior body 40 where the lid body 60 is omitted, the electrode body 20 is sealed by closing the portion of the exterior film 50 that protrudes outward beyond the electrode body 20. The portion of the exterior film 50 that protrudes outward beyond the electrode body 20 may be folded like a Goebel-top pouch or a brick pouch.

[0091] 2-3. Third Modification In the above embodiment, it is possible to arbitrarily change the outer shape of the exterior body 40. The outer shape of the exterior body 40 may be a cylinder, a prism, or a cube.

[0092] [3. Examples] The inventors of the present application manufactured hypothetical electricity storage devices using the exterior films of Examples 1 to 6 and Comparative Examples 1 to 3, and conducted load-bearing tests. In the load-bearing tests, the inventors measured the maximum deflection TX and calculated the value of parameter Y using equation (2). The method for conducting the load-bearing tests and the measurement conditions for the maximum deflection TX are the same as those in the embodiments. Note that, for ease of explanation, the following description may use the same reference numerals to designate components of the examples and comparative examples that are the same as those in the embodiments.

[0093] FIG. 15 shows the specifications of the exterior films 50 of Examples 1 to 6 and Comparative Examples 1 to 3. In the exterior films of Examples 2 to 5 and Comparative Example 3, the base material layer 51 is composed of a polyethylene terephthalate layer and a nylon layer. In the exterior films 50 of Examples 1 and 6, the base material layer 51 is composed of only a polyethylene terephthalate layer. In the exterior films 50 of Comparative Examples 1 and 2, the base material layer 51 is composed of only a nylon layer. In the exterior films 50 of Examples 1 to 5 and Comparative Examples 1 and 3, aluminum is used as the material constituting the barrier layer 52. In the exterior films 50 of Example 6 and Comparative Example 2, stainless steel is used as the material constituting the barrier layer 52. Of the materials constituting the heat-sealable resin layer 53 in FIG. 15 , PPa represents acid-modified polypropylene, PP represents polypropylene, and CPP represents unstretched polypropylene.

[0094] 16 is a table showing the measurement results of the maximum deflection amount TX in the load-bearing test. The load-bearing test was carried out by manufacturing four hypothetical power storage devices 10X (types A to D) using the exterior films 50 of Examples 1 to 6 and Comparative Examples 1 to 3. In types A and C, the second surface 42A or the second surface 42B of the exterior body 40 is the bottom surface. In types B and D, the first surface 41A or the first surface 41B of the exterior body 40 is the bottom surface.

[0095] It was confirmed that the maximum deflection amount TX of the exterior film 50 of Examples 1 to 6 was 5.0 mm or less when either the first surfaces 41A, 41B or the second surfaces 42A, 42B of the hypothetical power storage device 10X was the bottom surface. Furthermore, it was confirmed that, for the same weight of the electrode body 20, the exterior film 50 of Examples 1 to 6 had a smaller maximum deflection amount TX when the second surfaces 42A, 42B of the hypothetical power storage device 10X were the bottom surfaces than when the first surfaces 41A, 41B of the hypothetical power storage device 10X were the bottom surfaces.

[0096] It was confirmed that the exterior films 50 of Comparative Examples 1 to 3 had a larger maximum deflection amount TX than the hypothetical electricity storage devices 10X of the same type of Examples 1 to 6.

[0097] 17 is a table showing the calculation results of the parameter Y in equation (2). It was confirmed that the values ​​of the parameter Y for the exterior films 50 of Examples 1 to 6 were 5.0 mm or less, regardless of whether the first surfaces 41A, 41B or the second surfaces 42A, 42B of the hypothetical power storage device 10X were set as the bottom surface. It was also confirmed that, for the exterior films 50 of Examples 1 to 6, when the weight of the electrode body 20 was the same, the values ​​of the parameter Y were smaller when the second surfaces 42A, 42B of the hypothetical power storage device 10X were set as the bottom surface than when the first surfaces 41A, 41B of the hypothetical power storage device 10X were set as the bottom surface.

[0098] It was confirmed that the exterior films 50 of Comparative Examples 1 to 3 had larger values ​​of parameter Y than the hypothetical electricity storage devices 10X of the same type of Examples 1 to 6.

[0099] 10: Electricity storage device 10X: Virtual electricity storage device 20: Electrode body 20: Pseudo electrode body 40: Exterior body 41A, 41B: First surface 42A, 42B: Second surface 50: Exterior film 51: Base material layer 52: Barrier layer 53: Thermally adhesive resin layer 60: Lid body 90: Spacer 110: First support base 120: Second support base

Claims

1. An exterior film used as an exterior body of an electric storage device, comprising at least a base layer, a barrier layer, and a heat-sealable resin layer in this order, the thickness of the barrier layer being greater than 40 μm and less than 200 μm, and the bending stiffness of the exterior film being less than 2.0 gf cm ２ / cm or more.

2. The exterior film according to claim 1, wherein the thickness of the exterior film is 100 μm or more.

3. The electricity storage device comprises an electrode body and an exterior body sealing the electrode body, the exterior body including the exterior film wrapping the electrode body, and a pair of lid bodies arranged on sides of the electrode body and sealed by being joined to the exterior film, a load-bearing test of a hypothetical electricity storage device manufactured using the exterior film is carried out, the hypothetical electricity storage device has a configuration similar to the electricity storage device, and includes a first surface and a second surface, which are surfaces of the exterior body excluding the lid bodies and have an area smaller than that of the first surface, the pair of lid bodies joined to the exterior film, the electrode body or pseudo electrode body, the pair of lid bodies, and a spacer in contact with the electrode body or pseudo electrode body, the electrode body or pseudo electrode body and the spacer are sealed by the exterior film and the pair of lid bodies, the sum of the weight of the electrode body or pseudo electrode body and the weight of the spacer is 500 g or more, and in the load-bearing test, The exterior film according to claim 1 or 2, wherein, of the elements constituting the virtual energy storage device, only one of the lid bodies joined to the exterior film is placed on a first support stand having a height of 20 mm so that the first surface or the second surface is the underside, and, of the elements constituting the virtual energy storage device, only the other of the lid bodies joined to the exterior film is placed on a second support stand having a height of 20 mm, and five minutes after the virtual energy storage device is placed on the first support stand and the second support stand, a maximum deflection amount in the direction of gravity of a portion of the exterior film constituting the underside of the exterior body is 5 mm or less.

4. The electric storage device comprises an electrode body and an exterior body sealing the electrode body, the exterior body including the exterior film wrapping the electrode body, and a pair of lid bodies arranged on sides of the electrode body and sealed by being joined to the exterior film, a virtual electric storage device manufactured using the exterior film, the virtual electric storage device having a configuration similar to the electric storage device, the exterior body being configured excluding the lid bodies, and including a first surface and a second surface having an area smaller than that of the first surface, the pair of lid bodies joined to the exterior film, the electrode body or pseudo electrode body, the pair of lid bodies, and a spacer in contact with the electrode body or pseudo electrode body, the electrode body or pseudo electrode body and the spacer are sealed by the exterior film and the pair of lid bodies, the area of ​​the first surface or the second surface constituting a bottom surface is S (mm ２ The sum of the weight of the electrode body or the pseudo electrode body and the weight of the spacer is W (kg), and the bending stiffness of the exterior film is X (gf cm ２ 3. The exterior film according to claim 1 or 2, wherein when the thickness of the outer casing is 1 / cm, the value of a parameter Y calculated by the following formula is 5 or less: Y=-0.0000012·S·W·X+0.0000241·S·W.

5. The electricity storage device comprises an electrode body and an exterior body sealing the electrode body, the exterior body including the exterior film wrapping the electrode body, and a pair of lid bodies arranged on sides of the electrode body and sealed by being joined to the exterior film, a load-bearing test of a hypothetical electricity storage device manufactured using the exterior film is carried out, the hypothetical electricity storage device has a configuration similar to the electricity storage device, and includes a first surface and a second surface, which are surfaces of the exterior body excluding the lid bodies and have an area smaller than that of the first surface, the pair of lid bodies joined to the exterior film, the electrode body or pseudo electrode body, the pair of lid bodies, and a spacer in contact with the electrode body or pseudo electrode body, the electrode body or pseudo electrode body and the spacer are sealed by the exterior film and the pair of lid bodies, the sum of the weight of the electrode body or pseudo electrode body and the weight of the spacer is 500 g or more, and in the load-bearing test, The exterior film according to claim 1 or 2, wherein, of the elements constituting the virtual energy storage device, only one of the lid bodies joined to the exterior film is placed on a first support stand having a height of 20 mm so that the first surface or the second surface is the underside, and, of the elements constituting the virtual energy storage device, only the other of the lid bodies joined to the exterior film is placed on a second support stand having a height of 20 mm, and five minutes after the virtual energy storage device is placed on the first support stand and the second support stand, the maximum deflection amount in the direction of gravity of the portion of the exterior film that constitutes the underside of the exterior body is smaller when the second surface is the underside than when the first surface is the underside.

6. An electrode assembly comprising: an exterior body that seals the electrode assembly; the exterior body comprising: an exterior film that wraps the electrode assembly; and a lid that seals the electrode assembly together with the exterior film; the exterior film comprising at least a base layer, a barrier layer, and a heat-sealable resin layer in this order; the thickness of the barrier layer being greater than 40 μm and less than 200 μm; and the bending stiffness of the exterior film being less than 2.0 gf cm. ２ / cm or more.

7. The exterior body includes a first surface and a second surface that is a surface of the exterior body excluding the lid body and has an area smaller than that of the first surface, and a pair of the lid bodies that are joined to the exterior film, the electricity storage device includes a spacer that contacts the pair of lid bodies and the electrode body, the electrode body and the spacer are sealed by the exterior film and the pair of lid bodies, and in the electricity storage device, the area of ​​the first surface or the second surface that constitutes a bottom surface is set to S (mm ２ The sum of the weight of the electrode body and the weight of the spacer is W (kg), and the bending stiffness of the exterior film is X (gf cm ２ 7. The electricity storage device according to claim 6, wherein when the surface roughness is 1 / cm, a value of a parameter Y calculated by the following formula is 5 or less: Y=-0.0000012·S·W·X+0.0000241·S·W.

8. A method for manufacturing an electricity storage device, the electricity storage device comprising: an electrode body; and an exterior body that seals the electrode body; the exterior body comprising: an exterior film that wraps the electrode body; and a lid that seals the electrode body together with the exterior film; the exterior film comprising at least a base layer, a barrier layer, and a heat-sealable resin layer in this order; the barrier layer having a thickness of more than 40 μm and not more than 200 μm; and the exterior film having a bending stiffness of 2.0 gf cm ２ / cm or more, and the method for producing an electricity storage device includes a step of wrapping the electrode body with the exterior film.

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