Power storage device, lid member, and method for manufacturing power storage device

Abstract

This power storage device comprises an electrode body and an exterior body in which the electrode body is sealed. The exterior body has: an exterior film that wraps the electrode body; a lid member that seals the electrode body together with the exterior body; and a discharge unit configured so as to be able to discharge at least one among a gas and an electrolyte by being partially destroyed when the internal pressure of the exterior body rises.

Description

Electricity storage device, lid, and method for manufacturing an electricity storage device

[0001] The present invention relates to an electricity storage device, a lid, and a method for manufacturing an 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 encases the electrode assembly and a lid that is joined to the exterior film.

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

[0004] In the above-described electricity storage device, when the internal pressure increases, the exterior body may break, resulting in the release of at least one of the gas and the electrolyte. In the above-described electricity storage device, it is not possible to identify in advance the location where the exterior body will break when the internal pressure increases. Therefore, depending on the usage environment of the electricity storage device, an undesirable location in the exterior body may break, resulting in the release of at least one of the gas and the electrolyte.

[0005] The present invention aims to provide an electricity storage device in which the area where the outer casing breaks when internal pressure increases can be limited, a lid body used in this electricity storage device, and a method for manufacturing this electricity storage device.

[0006] An electricity storage device according to a first aspect of the present invention includes an electrode assembly and an exterior body that seals the electrode assembly. The exterior body has an exterior film that wraps the electrode assembly, a lid that seals the electrode assembly together with the exterior film, and a release section that is configured to be partially broken when the internal pressure of the exterior body increases, thereby releasing at least one of a gas and an electrolyte solution.

[0007] The energy storage device according to a second aspect of the present invention is the energy storage device according to the first aspect, wherein the lid body has a lid main body including a portion that is joined to the exterior film, and the release portion includes a portion of the lid main body that is configured to be partially thin.

[0008] The energy storage device according to a third aspect of the present invention is the energy storage device according to the first aspect, wherein the lid body has a lid main body including a portion that is joined to the exterior film, and the release portion includes a portion of the lid main body in which a recess is formed.

[0009] The fourth aspect of the present invention is an energy storage device according to the first aspect, wherein the outer casing includes at least two lids, one of which has a lower breaking strength than the other of which, and the release portion is formed in one of the lids.

[0010] The fifth aspect of the present invention is an energy storage device according to the first aspect, wherein the outer casing includes at least two lid bodies, the lid bodies have a lid sealing portion where the lid bodies and the outer casing film are joined, the joining strength of the lid sealing portion of one of the lid bodies is lower than the joining strength of the lid sealing portion of the other of the lid bodies, and the release portion is formed in the lid sealing portion of one of the lid bodies.

[0011] The sixth aspect of the present invention relates to an energy storage device according to the first aspect, wherein the outer casing has a lid sealing portion where the lid body and the outer casing film are joined, and the release portion includes a portion of the lid sealing portion where the joining strength is partially reduced.

[0012] The seventh aspect of the present invention is an energy storage device according to the first aspect, wherein the lid body has a lid main body and a covering body that joins the lid main body and the exterior film, and the release portion is a portion where the bonding strength between the lid main body and the covering body is lower than the bonding strength between the covering body and the exterior film.

[0013] The eighth aspect of the present invention is an energy storage device according to the first aspect, wherein the lid body has a lid main body that is joined to the exterior film, at least a portion of the portion of the lid main body that is joined to the exterior film is configured to contain a shape memory alloy, and the release portion includes a portion of the lid main body that contains the shape memory alloy, and is configured so that when the temperature of the exterior body increases due to an increase in internal pressure of the exterior body, the portion of the lid main body that contains the shape memory alloy returns to its original shape, causing the exterior body to be partially destroyed.

[0014] An electricity storage device according to a ninth aspect of the present invention is the electricity storage device according to the first aspect, wherein the release portion has a through-hole formed in the lid and a barrier film that closes the through-hole.

[0015] A lid body according to a tenth aspect of the present invention is a lid body used as an outer casing for an electricity storage device, and has a lid main body, which includes a portion that is breakable when the internal pressure of the outer casing increases and is partially thin.

[0016] A lid body according to an eleventh aspect of the present invention is a lid body used as an outer casing for an electricity storage device, and has a lid main body, which includes a portion that breaks when the internal pressure of the outer casing increases, or a portion that can destroy elements that make up the outer casing, and in which a recess is formed.

[0017] A lid body according to a twelfth aspect of the present invention is a lid body used as an exterior body for an electricity storage device, the lid body having a lid main body that is joined to an exterior film that constitutes the exterior body, and at least a portion of the portion of the lid main body that is joined to the exterior film is composed of a shape memory alloy.

[0018] A thirteenth aspect of the present invention relates to a method for manufacturing an electricity storage device, the method comprising: an electrode assembly; and an exterior body sealing the electrode assembly, the exterior body having an exterior film wrapping the electrode assembly, a lid sealing the electrode assembly together with the exterior film, and a release portion configured to be ruptured to release at least one of a gas and an electrolyte solution when the internal pressure of the exterior body increases. The method for manufacturing an electricity storage device includes a step of forming the release portion.

[0019] According to the electricity storage device, lid, and method for manufacturing an electricity storage device of the present invention, the portion of the exterior body that breaks when the internal pressure increases can be limited to a specific portion.

[0020] 1A. 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 sealing portion of the electricity storage device of FIG. 1. A cross-sectional view showing the layer structure of an exterior film included in the electricity storage device of FIG. 1. A diagram showing the exterior film included in the electricity storage device of FIG. 1 in an unfolded state. A perspective view of a lid included in the electricity storage device of FIG. 1. A cross-sectional view taken along line D5-D5 of FIG. 1A. A cross-sectional view taken along line D6-D6 of FIG. 1A. A flowchart showing an example of a manufacturing method for the electricity storage device of FIG. 1. A diagram relating to a second step of the manufacturing method for an electricity storage device. A perspective view of a lid included in an electricity storage device of a first modified example. A cross-sectional view of an electricity storage device of a second modified example. A cross-sectional view of an electricity storage device of a third modified example. A cross-sectional view of a lid main body and a joint portion of a lid included in an electricity storage device of a fifth modified example. A cross-sectional view of a lid main body and a joint portion of a lid included in an electricity storage device of a sixth modified example. A cross-sectional view showing an example of a state in which a discharge portion of an electricity storage device of a seventh modified example is broken. A cross-sectional view showing another example of a state in which a discharge portion of an electricity storage device of the seventh modified example is broken. 13 is a cross-sectional view showing an example of a state in which a discharge portion of an electricity storage device according to an eighth modified example is broken;

[0021] 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.

[0022] [Embodiment] <1-1. Configuration of Electricity Storage Device> FIG. 1A is a plan view schematically illustrating an electricity storage device 10 according to an embodiment. FIG. 1B is a diagram illustrating a method for measuring the seal strength of a second sealed portion 100B of the electricity storage device 10 of FIG. 1A. FIG. 2 is a cross-sectional view illustrating the layer structure 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. FIG. 5 is a cross-sectional view taken along line D5-D5 in FIG. 1A. FIG. 6 is a cross-sectional view taken along line D6-D6 in 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 the same in the following figures.

[0023] The energy storage device 10 includes an electrode assembly 20 including a current collector 30 and an exterior housing 40. The electrode assembly 20 includes electrodes (positive and negative electrodes) constituting an energy storage member such as a lithium-ion battery, capacitor, all-solid-state battery, semi-solid battery, quasi-solid battery, polymer battery, all-resin battery, lead-acid battery, nickel-metal hydride battery, nickel-cadmium battery, nickel-iron battery, nickel-zinc battery, silver oxide-zinc battery, metal-air battery, polyvalent cation battery, or capacitor, as well as a separator. In this embodiment, the electrode assembly 20 has a substantially rectangular parallelepiped shape. 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 electrode assembly 20 may have a cylindrical or polygonal prism shape, for example.

[0024] One end 31 of the current collector 30 (see FIG. 6) is connected to the lid 60 .

[0025] 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.

[0026] 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.

[0027] As shown in FIG. 2 , the exterior film 50 is a laminate (laminate film) having, for example, a base material layer 51, a barrier layer 52, and a heat-sealable resin layer 53 in this order. It is not necessary for the exterior film 50 to include all of these layers; for example, it may not include the barrier layer 52. That is, the exterior film 50 may be made of any material that is flexible and easily bendable, and may be made of, for example, a resin film. It is preferable that the exterior film 50 is heat-sealable. The innermost and outermost 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.

[0028] The exterior film 50 may be composed of a laminate including at least a barrier layer 52 and a heat-sealable resin layer 53 in this order. In this laminate, the base layer 51 is an optional layer, and the side of the barrier layer 52 opposite to the heat-sealable resin layer 53 is the outermost layer, and the heat-sealable resin layer 53 is the innermost layer.

[0029] The overall thickness of the exterior film 50 can be selected arbitrarily. From the viewpoint of strength, the thickness of the exterior film 50 is preferably 50 μm or more. From the viewpoint of formability or conformability, the thickness of the exterior film 50 is preferably 1200 μm or less. The thickness of the exterior film 50 is preferably within the range of 50 μm or more and 1200 μm or less.

[0030] 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. From the viewpoint of film strength, the thickness of the substrate layer 51 is preferably, for example, 5 to 300 μm, and more preferably 5 to 150 μm.

[0031] 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 alloys, stainless steel, titanium steel, and steel plates. When used as a metal foil, it is preferable that the metal material contains at least one of an aluminum alloy foil and a stainless steel foil.

[0032] In the barrier layer 52, the layer made of the aforementioned metal material may contain recycled metal material. Examples of recycled metal 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 of recycled material alone, or may be made of a mixture of recycled and virgin material. Note that recycled metal material refers to metal material that has been made reusable by collecting, isolating, and refining various products used in the market or waste from manufacturing processes. Furthermore, virgin metal material refers to new metal material refined from natural metal resources (raw materials) and is not recycled material.

[0033] 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. From the viewpoint of further improving the formability or conformability, an iron-containing aluminum alloy foil is preferred. 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 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. Furthermore, silicon, magnesium, copper, manganese, etc. may be added to the aluminum alloy foil as needed. Furthermore, softening can be achieved by annealing or the like. From the viewpoint of improving the mechanical strength of the exterior film 50, the aluminum alloy foil is more 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.

[0034] 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.

[0035] Specific examples of austenitic stainless steels that form the stainless steel foil include SUS304, SUS301, and SUS316L, with SUS304 being particularly preferred.

[0036] 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 5 to 1000 μm. The thickness of the barrier layer 52 is preferably about 85 μm or less, more preferably about 50 μm or less, even more preferably about 40 μm or less, and particularly preferably about 35 μm or less. The thickness of the barrier layer 52 is preferably about 9.0 μm or more, more preferably about 20 μm or more, and more preferably about 25 μm or more. Preferred ranges for the thickness of the barrier layer 52 include about 9.0 to 1000 μm, about 9.0 to 1000 μm, about 9.0 to 1000 μm, about 9.0 to 1000 μm, about 9.0 to 85 μm, about 9.0 to 50 μm, about 9.0 to 40 μm, about 9.0 to 35 μm, about 20 to 85 μm, about 20 to 50 μm, about 20 to 40 μm, about 20 to 35 μm, about 25 to 85 μm, about 25 to 50 μm, about 25 to 40 μm, and about 25 to 35 μm. When the barrier layer 52 is made of aluminum alloy foil, the above-mentioned ranges are particularly preferred. From the viewpoint of imparting high formability and high rigidity to the exterior film 50, the thickness of the barrier layer 52 is preferably about 35 μm or more, more preferably about 45 μm or more, even more preferably about 50 μm or more, and even more preferably about 55 μm or more, and is preferably about 200 μm or less, more preferably about 85 μm or less, even more preferably about 75 μm or less, and even more preferably about 70 μm or less. Preferred ranges are approximately 35 to 200 μm, approximately 35 to 85 μm, approximately 35 to 75 μm, approximately 35 to 70 μm, approximately 45 to 200 μm, approximately 45 to 85 μm, approximately 45 to 75 μm, approximately 45 to 70 μm, approximately 50 to 200 μm, approximately 50 to 85 μm, approximately 50 to 75 μm, approximately 50 to 70 μm, approximately 55 to 200 μm, approximately 55 to 85 μm, approximately 55 to 75 μm, and approximately 55 to 70 μm. The high formability of the exterior film 50 facilitates deep drawing, which can contribute to increasing the capacity of the electricity storage device. Furthermore, while increasing the capacity of the electricity storage device increases the weight of the electricity storage device, increasing the rigidity of the exterior film 50 can contribute 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 60 μm or less, more preferably about 50 μm or less, even more preferably about 40 μm or less, even more preferably about 30 μm or less, and particularly preferably about 25 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 ranges for the thickness of the stainless steel foil include about 10 to 60 μm, about 10 to 50 μm, about 10 to 40 μm, about 10 to 30 μm, about 10 to 25 μm, about 15 to 60 μm, about 15 to 50 μm, about 15 to 40 μm, about 15 to 30 μm, and about 15 to 25 μm.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] When the buffer layer is made of rubber, the lower limit of the thickness of the buffer layer is preferably 0.5 mm. When the buffer layer is made of rubber, the upper limit of the thickness of the buffer layer is preferably 10 mm, more preferably 5 mm, and even more preferably 2 mm. When the buffer layer is made of rubber, the preferred range of the thickness of the buffer layer is 0.5 mm to 10 mm, 0.5 mm to 5 mm, or 0.5 mm to 2 mm.

[0043] 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.

[0044] The lid body 60 has a lid main body 70, a joint 80, and a covering body 90 that covers a part of the lid main body 70. The lid body 60 can be manufactured, for example, by injection molding the covering body 90 onto the lid main body 70.

[0045] The lid main body 70 and the joint portion 80 are composed of a conductive material. "Composed of a conductive material" means that, when the entire material constituting the lid main body 70 and the joint portion 80 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 main body 70 and the joint portion 80 can contain materials other than the conductive material in addition to the conductive material. The lid main body 70 and the joint portion 80 preferably have the corrosion-resistant coating described in connection with the barrier layer 52.

[0046] The conductive material constituting the lid body 70 and the joint 80 is, for example, a metal material. The metal material constituting the lid body 70 and the joint 80 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 70 and the joint 80 connected to the positive electrode are preferably made of aluminum or an aluminum alloy. The lid body 70 and the joint 80 connected to the negative electrode are preferably made of nickel, copper, or a copper alloy. The material constituting the lid body 70 and the joint 80 connected to the negative electrode may be nickel-plated copper. The material constituting the lid body 70 and the joint 80 may include recycled metal material. The lid body 70 has a base 71 and a covering 72.

[0047] 4 and 5 is, for example, a rectangular plate and has a first surface 71A and a second surface 71B. The first surface 71A faces the outside. The second surface 71B is the surface opposite to the first surface 71A. The second surface 71B faces the electrode body 20.

[0048] The covering portion 72 is covered by a covering body 90. The covering portion 72 is frame-shaped and rises from the first surface 71A of the base 71. The covering portion 72 has a first covering portion 72A, a second covering portion 72B, and a third covering portion 72C. The first covering portion 72A forms the top surface of the lid main body 70. The first covering portion 72A extends in a first direction (in the present embodiment, the LR direction) in a front view of the lid main body 70. The second covering portion 72B and the third covering portion 72C are connected to the first covering portion 72A and form the side surfaces of the lid main body 70. The second covering portion 72B and the third covering portion 72C extend in a second direction (in the present embodiment, the UD direction) that intersects with the first direction in a front view of the lid main body 70. In the present embodiment, the first direction and the second direction are orthogonal in a front view of the lid main body 70. The first direction and the second direction do not have to be perpendicular to each other when the lid main body 70 is viewed from the front.

[0049] At least a portion of the surface 72X of the covering portion 72 is covered with the covering body 90. In this embodiment, the entire surface 72X of the covering portion 72 is covered with the covering body 90.

[0050] The joint 80 is formed to facilitate joining of the current collector 30 of the electrode assembly 20 and the lid body 60. The shape of the joint 80 can be selected arbitrarily as long as it protrudes from the lid main body 70 toward the electrode assembly 20. In this embodiment, the joint 80 is plate-shaped and protrudes in a first direction, which is the direction from the second surface 71B of the base 71 toward the electrode assembly 20.

[0051] The lid body 70 and the joint portion 80 may be made of the same conductive material or different conductive materials. At least one of the lid body 70 and the joint portion 80 may be made of partially different conductive materials. The lid body 70 and the joint portion 80 may be integrally formed, or may be formed separately and joined. When the lid body 70 and the joint portion 80 are integrally formed, the lid body 70 and the joint portion 80 can be manufactured by, for example, machining, polishing, electric discharge machining, cutting, pressing, casting, plastic processing, sintering, 3D printing, or forging. When the lid body 70 and the joint portion 80 are formed separately, the lid body 70 and the joint portion 80 may be joined by welding, recess-and-projection fitting, or crimping. The lid body 70 and the joint portion 80 can be manufactured by any method, without being limited to these.

[0052] The joint portion 80 has a first end portion 81 and a second end portion 82. The first end portion 81 is one end portion in the FB direction. The first end portion 81 is connected to the lower surface of the base portion 71. The second end portion 82 is the other end portion in the FB direction. The portion of the joint portion 80 including the first end portion 81 is sandwiched between the second covering portion 72B and the third covering portion 72C.

[0053] The joint 80 is joined to the current collector 30 by, for example, ultrasonic bonding. In the manufacturing process of the electricity storage device 10, from the viewpoint of ensuring a large space for arranging the apparatus 110 (see FIG. 8 ), it is preferable that the second end 82 of the joint 80 is formed in a position that does not overlap with the lid main body 70 in a plan view. The second end 82 may be formed in a position spaced apart from the exterior film 50. When the second end 82 is formed in a position spaced apart from the exterior film 50, the second end 82 and the exterior film 50 are less likely to come into contact with each other. This prevents damage to the exterior film 50 due to contact between the joint 80 and the exterior film 50.

[0054] The joint portion 80 has an upper surface 83 and a lower surface 84. The upper surface 83 is joined to the current collector 30. The current collector 30 may be joined to the lower surface 84. Of the upper surface 83 and the lower surface 84, at least the portions that are joined to the current collector 30 are preferably subjected to a surface treatment to ensure suitable joining to the current collector 30.

[0055] In this embodiment, at least a portion of the lower surface 84 is covered by the covering body 90. The lower surface 84 is preferably joined to the exterior film 50 via the covering body 90. The area of ​​the lower surface 84 that is joined to the exterior film 50 can be selected arbitrarily. In this embodiment, a portion of the lower surface 84 is joined to the exterior film 50. Almost the entire lower surface 84 may be joined to the exterior film 50. Note that if the lid body 60 does not have the covering body 90, the lid main body 70 and the joint portion 80 may be joined to the exterior film 50 with an adhesive.

[0056] The thickness HA of the joint 80 can be selected arbitrarily. The joint 80 preferably has a thickness that allows it to be easily bent so that the position of the second end 82 can be adjusted within the exterior body 40. The joint 80 preferably has a certain thickness so that the joint 80 will not be damaged even if an external force is applied to the exterior body 40. From this perspective, the minimum value of the thickness HA of the joint 80 is preferably 0.05 mm, for example. The maximum value of the thickness HA of the joint 80 is preferably 16 mm, for example. A preferred range for the thickness HA of the joint 80 is 0.6 mm to 0.05 mm. The thickness HA of the joint 80 may vary depending on the location. If the thickness HA of the joint 80 varies depending on the location, the thickness HA of the joint 80 is the thickness of the thickest portion.

[0057] The covering body 90 shown in FIGS. 4 and 5 has a lid seal portion 91. The lid seal portion 91 is heat-sealed to the heat-fusible resin layer 53 of the exterior film 50. The lid seal portion 91 and the exterior film 50 may be joined by any method other than heat sealing, such as welding. Specific welding methods include laser welding, ultrasonic welding, and other methods. The lid seal portion 91 includes a first seal surface 91A, a second seal surface 91B, a third seal surface 91C, and a fourth seal surface 91D. The first seal surface 91A forms the top surface of the lid body 60. The first seal surface 91A is formed on the first covering portion 72A. The first seal surface 91A extends in a first direction (the LR direction in this embodiment) when viewed from the front of the lid body 60. The second seal surface 91B and the third seal surface 91C are connected to the first seal surface 91A and form the side surfaces of the lid body 60. The second sealing surface 91B is formed on the second covering portion 72B. The third sealing surface 91C is formed on the third covering portion 73C. The second sealing surface 91B and the third sealing surface 91C extend in a second direction (UD direction in this embodiment) intersecting 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 sealing surface 91D forms the lower surface of the lid 60. The fourth sealing surface 91D extends in the first direction (LR direction in this embodiment) in a front view of the lid 60. The fourth sealing surface 91D is formed on the lower surface 84 of the joint portion 80.

[0058] The lid seal portion 91 further includes boundaries 92, 93, 94, and 95. The boundary 92 is the boundary between the first seal surface 91A and the second seal surface 91B. The boundary 93 is the boundary between the first seal surface 91A and the third seal surface 91C. The boundary 94 is the boundary between the fourth seal surface 91D and the second seal surface 91B. The boundary 95 is the boundary between the fourth seal surface 91D and the third seal surface 91C. The shapes of the boundaries 92 to 95 may be angular, or may be rounded by applying a rounding process. In this embodiment, the boundaries 92 to 95 are angular.

[0059] The covering 90 is made up of a resin material. Here, "made up of a resin material" means that, when the entire material constituting the covering 90 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 covering 90 can contain materials other than the resin material in addition to the resin material.

[0060] 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 covering 90 may be molded using any molding method.

[0061] The resin material contained in the material constituting the coating 90 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 coating 90 preferably contains multiple types of amide-based lubricants. Furthermore, the resin material contained in the material constituting the coating 90 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 coating 90 may be a polyolefin resin to which a propylene-based elastomer having a melting point higher than 150°C has been added.

[0062] 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.

[0063] 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.

[0064] 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 covering 90 against temperature changes can be improved.

[0065] The melt mass flow rate of the resin material contained in the material constituting the coating 90 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 melt mass flow rate is measured at 230°C.

[0066] In the lid body 60, the lid main body 70 may be made of a resin material. When the lid main body 70 is made of a resin material, the cover 90 may be omitted. When the lid main body 70 is made of a resin material, an electrode terminal is preferably joined to the lid main body 70. The electrode terminal is joined to the current collector 30.

[0067] The lid 60 may be bonded to the exterior film 50 via an adhesive film instead of the covering 90. Any adhesive film can be selected as long as it can bond the exterior film 50 and the lid 60 together. 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 .

[0068] 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.

[0069] 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.

[0070] When the lid body 60 is plate-shaped, it is preferable that the lid body 60 have a certain thickness 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 seal portion 91 of the lid body 60 have a certain thickness in the FB direction so that the lid seal portion 91 of the lid body 60 and the exterior film 50 can be heat-sealed appropriately when forming the second sealing portion 100B described below. The minimum thickness of the lid seal portion 91 of the lid body 60 is, for example, 1.0 mm, more preferably 3.0 mm, and even more preferably 4.0 mm. The maximum thickness of the lid seal portion 91 of the lid body 60 is, for example, 20 mm, more preferably 15 mm, and even more preferably 10 mm. The maximum thickness of the lid seal portion 91 of the lid body 60 may be 20 mm or more. Preferred ranges for the thickness of the lid seal portion 91 of 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 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. Note that the thickness of the lid seal portion 91 of the lid body 60 may vary depending on the region of the lid body 60. When the thickness of the lid seal portion 91 of the lid body 60 varies depending on the region, the thickness of the lid seal portion 91 of the lid body 60 is the thickness of the thickest portion.

[0071] In this embodiment, the first sealing portion 100A 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).

[0072] The first sealed portion 100A 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 100A extends in the longitudinal direction of the exterior body 40. The position at which the first sealed portion 100A is formed on the exterior body 40 can be selected arbitrarily. In this embodiment, the base 70X of the first sealed portion 100A is preferably located on the edge 43 at the boundary between the first surface 41 and the second surface 42 of the exterior body 40. The first surface 41 has a larger area than the second surface 42. The base 100AX of the first sealed portion 100A may be located on any surface of the exterior body 40. In this embodiment, the first sealed portion 100A protrudes outward beyond the electrode assembly 20 in a plan view. The first sealed portion 100A may be folded, for example, toward the second surface 42 or the first surface 41 of the exterior body 40.

[0073] In this embodiment, the second sealing portion 100B (lid sealing portion 100B) is formed by heat-sealing the heat-fusible resin layer 53 of the exterior film 50 and the lid seal portion 91 of the lid body 60. Hereinafter, the seal strength between the heat-fusible resin layer 53 of the exterior film 50 and the lid seal portion 91 of the lid body 60 may be referred to as the seal strength (bonding strength) of the second sealing portion 100B. Note that the seal strength of the second sealing portion 100B is the seal strength between the heat-fusible resin layer 53 and the lid body 60 at the long side portion of the lid seal portion 91, i.e., the lid seal portion 91 extending in the LR (width) direction in FIG. 1A .

[0074] The seal strength of the second sealing portion 100B is measured as follows. First, a slit is formed in the portion of the exterior film 50 that constitutes the first surface 41 of the exterior body 40, and three strip-shaped members 41X, 41Y, and 41Z (see the two-dot chain lines in FIG. 1B ) aligned in the LR direction are formed. The strip-shaped members 41X, 41Y, and 41Z are formed so as to avoid the release portion 100X, which will be described later. 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 100B. The length of the lid body 60 in the LR direction is 45 mm or more. Next, the end of each of the belt-shaped members 41X, 41Y, and 41Z opposite the end joined to the lid 60 is pulled upward in the UD direction (the direction opposite to the first surface 41B) to measure the seal strength of each of the belt-shaped members 41X, 41Y, and 41Z. The distance between the chucks in the UD direction is 10 mm. The seal strengths of the belt-shaped members 41X, 41Y, and 41Z are the peak values ​​of their respective seal strengths. In this embodiment, the seal strength of the second sealing portion 100B is the average value of the seal strengths of the belt-shaped members 41X, 41Y, and 41Z. When the length of the lid 60 in the LR direction is less than 45 mm, three belt-shaped members with an arbitrary width X mm, less than 15 mm, are formed, and the seal strengths of the three belt-shaped members are measured using the same method as when the length of the lid 60 in the LR direction is 45 mm or more. The obtained seal strengths are each divided by an arbitrary width X mm and multiplied by 15 to convert them into the seal strengths of the three strip-shaped members for a 15 mm width. The seal strength of the second sealing portion 100B is the average value of the seal strengths of the three strip-shaped members converted into 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 100B is the seal strength of the long sides of the lid seal portions 91 of the multiple parts.

[0075] 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 100B 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 100B 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 100B 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 unit 100B is preferably 300 N / 15 mm or less. A preferred range of the seal strength of the second sealing portion 100B is 40N / 15mm to 300N / 15mm, 50N / 15mm to 300N / 15mm, 60N / 15mm to 300N / 15mm, 70N / 15mm to 300N / 15mm, or 85N / 15mm to 300N / 15mm.

[0076] In this embodiment, the lid body 60 preferably has a protrusion 96 protruding from the lid seal portion 91 to prevent a gap from forming between the exterior film 50 and the lid body 60. The protrusion 96 may be formed integrally with the cover 90, or may be formed separately from the cover 90 and joined to the cover 90. In this embodiment, the protrusion 96 is formed integrally with the cover 90. The position at which the protrusion 96 is formed in the lid seal portion 91 can be selected arbitrarily. A gap between the exterior film 50 and the lid body 60 is likely to form, for example, between the base 100AX of the first sealing portion 100A and the lid body 60. In particular, when the base 100AX of the first sealing portion 100A is located between the boundary 92 and boundary 95 of the lid body 60, the resin filling ability between the base 100AX of the first sealing portion 100A and the lid body 60 is likely to decrease. For this reason, the protrusion 96 is preferably formed in the lid seal portion 91 at a location where the root 100AX of the first sealing portion 100A is located. In this embodiment, the root 100AX of the first sealing portion 100A is located at the boundary 92 of the lid body 60. For this reason, the protrusion 96 is preferably formed in the lid seal portion 91 at the boundary 92. In this embodiment, the first sealing portion 100A is sealed with the protrusion 96 sandwiched between them. Note that the protrusion 96 may be formed on at least one of the first seal surface 100AA, the second seal surface 100AB, the third seal surface 100AC, the fourth seal surface 100AD, the boundary 93, the boundary 94, and the boundary 95.

[0077] The shape of the protrusion 96 can be selected arbitrarily. In this embodiment, the shape of the protrusion 96 is plate-like. The thickness of the protrusion 96 can be selected arbitrarily. In this embodiment, the thickness of the protrusion 96 becomes thinner with increasing distance from the boundary 92. In other words, the protrusion 96 has a tapered shape with increasing distance from the boundary 92. The thickness of the protrusion 96 may be constant, or may increase with increasing distance from the boundary 92.

[0078] The direction in which the protrusion 96 extends can be selected arbitrarily. In the present embodiment, the protrusion 96 extends along a first direction (in the present embodiment, the LR direction). The protrusion 96 may extend along a second direction (in the present embodiment, the UD direction). The protrusion 96 may extend in a third direction that intersects with the first direction (in the present embodiment, the LR direction) and the second direction (in the present embodiment, the UD direction) when the lid 60 is viewed from the front.

[0079] The length of the protrusion 96 can be selected arbitrarily within a range equal to or less than the length of the first sealing portion 100A. For example, the length of the protrusion 96 may be substantially equal to the length of the first sealing portion 100A, or may be 30% to 50% of the length of the first sealing portion 100A.

[0080] When the electricity storage device 10 is in use, the internal pressure of the exterior body 40 increases due to the influence of at least one of the expansion of the electrode assembly 20 and the gas generated inside the exterior body 40. When the internal pressure of the exterior body 40 increases, a part of the exterior body 40 breaks, and at least one of the gas and the electrolyte is released. The electricity storage device 10 of this embodiment is provided with a release section 100X that is configured to limit, to some extent, the location of the exterior body 40 that breaks when the internal pressure of the exterior body 40 increases. The number of release sections 100X provided in the electricity storage device 10 can be selected arbitrarily. In this embodiment, the electricity storage device 10 is provided with one release section 100X. The electricity storage device 10 may be provided with two or more release sections 100X.

[0081] The release portion 100X is an element of the exterior body 40 whose strength is partially reduced. The position of the exterior body 40 where the release portion 100X is formed is a position where, for example, even if gas or the like is released, the influence on surrounding devices is small. For this reason, the position of the exterior body 40 where the release portion 100X is formed is arbitrary, and is preferably determined based on the usage environment of the electricity storage device 10.

[0082] In this embodiment, the discharge portion 100X is a portion of the second sealing portion 100B where the bonding strength is partially reduced. For example, the discharge portion 100X is formed in a portion including the center of the first sealing surface 91A in the LR direction.

[0083] The material constituting the portion of the covering 90 where the release portion 100X is formed (hereinafter referred to as the "first material") is made of a resin material different from the material constituting the other portions (hereinafter referred to as the "second material"). In a first example, the first material is a material with a lower melting point than the second material. In the first example, the first material is polyethylene or polypropylene with a higher polyethylene content than the second material. In a second example, the first material is a material that contains more filler than the second material. The filler is, for example, glass fiber or carbon fiber. Note that the first material and the second material are not limited to resin materials and can be selected arbitrarily as long as they are materials that can adjust the bonding strength of the second sealing portion 100B.

[0084] The entire cover 90 may be made of the same resin material. In this case, by making at least one of the width in the FB direction and the thickness in the UD direction of the portion of the cover 90 corresponding to the release portion 100X smaller than those of other portions, it is possible to form the release portion 100X in which the bonding strength of the second sealing portion 100B is partially reduced. Note that the material constituting the cover 90 can be selected arbitrarily as long as it is a material that can bond the lid main body 70 and the exterior film 50.

[0085] 7 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, and a fifth step. The first step to the fifth step are performed, for example, by a manufacturing apparatus for the power storage device 10. At least some of the first step to the fifth step may be performed by an operator. Note that the first step to the fifth 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 first step to the fifth step can be changed as desired as long as it is not technically inconsistent.

[0086] In the first process of step S11, the manufacturing device places a pair of lid bodies 60 on either side of the electrode body 20 in the FB direction.

[0087] The second process of step S12 is performed after the first process. In the second process, the manufacturing apparatus joins the current collector 30 and the joint 80 of the lid body 60. Note that if the lid main body 70 and the joint 80 are configured as separate bodies, the joint 80 and the lid main body 70 may be joined after the current collector 30 and the joint 80 are joined.

[0088] 8 is a diagram relating to the second step. In this embodiment, in the second step, the current collector 30 and the joint 80 are joined by ultrasonic bonding. The current collector 30 and the joint 80 may also be joined by resistance welding or laser welding. The ultrasonic bonding is performed using an apparatus 110. The apparatus 110 is a known ultrasonic device and includes a tip 111, an anvil 112, a horn 113, and an oscillator 114. In the second step, the current collector 30 and the joint 80 are ultrasonically bonded together in a state in which the upper surface 83, the lower surface 84, and a portion of the joint 80 including the end 31 of the current collector 30 are sandwiched between the tip 111 and the anvil 112.

[0089] The third step of step S13 is performed after the second step. In the third step, the manufacturing apparatus winds the exterior film 50 around the electrode assembly 20 and the lid body 60 while tension is applied to the exterior film 50, while restricting the movement of the electrode assembly 20 and the lid body 60 using 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. 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 after the current collector 30 and the joint 80 are joined, the opening may be closed with the lid 60. In yet another example, the electrode body 20 connected to the joint 80 of the lid 60 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 opening may be closed with the lid 60.

[0090] The fourth step of step S14 is performed after the third step. In the fourth step, the manufacturing apparatus forms the second sealed portion 110B by heat-sealing the exterior film 50 and the lid body 60. Completion of the fourth step results in the formation of the release portion 100X in which the bonding strength of the second sealed portion 110B is partially reduced.

[0091] The fifth step of step S15 is performed before or after the fourth step. In the fifth step, the manufacturing apparatus forms the first sealed portion 100A by heat-sealing the heat-sealable resin layer 53 in a portion including the first edge 50A of the exterior film 50 and the heat-sealing the heat-sealable resin layer 53 in a portion including the second edge 50B while restricting the movement of the electrode body 20 and the lid body 60 and applying tension to the exterior film 50.

[0092] <1-3. Functions and Effects of the Electricity Storage Device> The electricity storage device 10 includes a release section 100X. The release section 100X is an element in which the strength of the exterior body 40 is partially reduced. Therefore, when the internal pressure of the exterior body 40 increases, the release section 100X is likely to break (peel off) before other sections, causing the release of gas and the like. For this reason, when the internal pressure of the exterior body 40 increases, the section in which the exterior body 40 breaks can be limited.

[0093] [2. Modifications] The above-described embodiments are examples of possible forms of the electricity storage device, lid, and method for manufacturing an electricity storage device according to the present invention, and are not intended to limit the forms. The electricity storage device, lid, 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.

[0094] 2-1. First Modification In the above embodiment, the position where the joint 80 of the lid body 60 is formed can be changed as desired. FIG. 9 is a perspective view of a lid body 160 included in an electricity storage device 10 of a first modification. The lid body 160 has a joint 180. It is sufficient that a first end 81 of the joint 180 is connected to at least the lid main body 70. In the example shown in FIG. 9, the covering portion 72 preferably has a fourth covering portion 72D. The fourth covering portion 72D forms the lower surface of the lid main body 70. The fourth covering portion 72D is connected to the second covering portion 72B and the third covering portion 72C. The fourth covering portion 72D extends in a first direction (the LR direction in this embodiment) when the lid body 160 is viewed from the front. When the covering portion 72 has the fourth covering portion 72D, the lower surface 84 of the joint 180 does not need to be covered by the covering body 90, and therefore the second end portion 82 may be formed at a position spaced apart from the exterior film 50. When the second end portion 82 is formed at a position spaced apart from the exterior film 50, the second end portion 82 is less likely to come into contact with the exterior film 50. This reduces damage to the exterior film 50 caused by contact between the joint 80 and the exterior film 50.

[0095] 2-2. Second Modification In the above-described embodiment, the shape of the joint 80 can be modified as desired. FIG. 10 is a cross-sectional view of an electricity storage device 10 according to a second modification. The electricity storage device 10 according to the second modification includes a lid body 260. The lid body 260 has a joint 280. The joint 280 has a first portion 281 and a second portion 282. The first portion 281 is connected to the lid main body 70 and extends in a first direction toward the electrode body 20. In the example shown in FIG. 10 , the first direction is the FB direction. The second portion 282 is connected to the first portion 281 and extends in a second direction intersecting the first direction in a side view of the lid body 60. In the example shown in FIG. 10 , the second direction is the UD direction. The angle between the first direction and the second direction is within a range greater than 0° and less than 180°. 10, the angle between the first direction and the second direction is 90°. In the second modified example, the second portion 282 of the joint 280 and the current collector 30 are joined.

[0096] The first portion 281 and the second portion 282 may be integrally formed, or may be formed separately and then joined. In the second modified example, the first portion 281 and the second portion 282 are integrally formed. More specifically, in the second modified example, the first portion 281 and the second portion 282 are formed by bending one joint 280. In the second modified example, the joint 280 has a thickness that allows it to be bent, and therefore is flexible. Therefore, the joint 280 is less likely to be damaged even when an external force such as vibration acts on the power storage device 10. In other words, the joint 280 is highly durable. Furthermore, because the joint 280 extends in the second direction, the size of the power storage device 10 in the FB direction can be made smaller than in a configuration in which the joint extends as a whole in the first direction. Furthermore, because the second end 82 is formed at a position spaced apart from the exterior film 50, the second end 82 is less likely to come into contact with the exterior film 50. Therefore, damage to the exterior film 50 caused by contact between the joint 280 and the exterior film 50 is suppressed.

[0097] 2-3. Third Modification FIG. 11 is a cross-sectional view of a power storage device 10 according to a third modification, which is a further modification of the second modification. The power storage device 10 according to the third modification includes a lid 360. The lid 360 has a joint 380. The joint 380 includes a third portion 383 in addition to the first portion 281 and the second portion 282 of the second modification. The third portion 383 is connected to the second portion 282 and extends in a first direction toward the electrode body 20. In the example shown in FIG. 11 , the first direction is the FB direction. The first portion 281, the second portion 282, and the third portion 383 may be integrally formed, or at least two of them may be formed separately and joined together. In the third modification, the first portion 281, the second portion 282, and the third portion 383 are integrally formed. More specifically, in the third modified example, one joint 380 is bent to form a first portion 281, a second portion 282, and a third portion 383. The power storage device 10 of the third modified example also provides the same effects as the power storage device 10 of the second modified example.

[0098] <2-4. Fourth Modification> In the above embodiment, the covering portion 72 may be omitted from the lid main body 70. In the fourth modification, the side surface (edge) of the base portion 71 may be covered by the covering body 90. In the fourth modification, the first end portion 81 of the joint portion 80 may be connected to the second surface 71B of the base portion 71, or may be connected to the side surface of the base portion 71.

[0099] <2-5. Fifth Modification> In the above embodiment, the specific configuration of the release section 100X can be changed as desired. Fig. 12 is a cross-sectional view of the lid main body 570 of the lid body 60 included in the electricity storage device 10 of the fifth modification. Note that the cover 90 is not shown in Fig. 5.

[0100] The lid main body 570 includes a release portion 500X. The release portion 500X is a component of the lid main body 570 that is configured to have a partially thinner thickness. In the example shown in FIG. 12 , the release portion 500X is formed in the base portion 571. The release portion 500X may be formed in the covering portion 72, or may be formed at the boundary between the base portion 71 and the covering portion 72. In the electricity storage device 10 of the fifth modification, when the internal pressure of the exterior body 40 increases, the release portion 500X is likely to break (rupture) before other portions, causing the release of gas and the like. Therefore, the electricity storage device 10 of the fifth modification can achieve the same effects as the electricity storage device 10 of the embodiment.

[0101] 13 is a cross-sectional view of a lid main body 670 of a lid body 60 provided in an electricity storage device 10 according to a sixth modified example. Note that the cover body 90 is not shown in FIG.

[0102] The lid main body 670 includes a release portion 600X. The release portion 600X is an element in which a recess 610 is formed in the lid main body 670, thereby partially reducing the strength of the lid main body 670. The recess 610 does not penetrate the lid main body 670. The recess 610 is, for example, a depression or a notch. In the example shown in FIG. 12 , the recess 610 is formed in the covering portion 72. The recess 610 may also be formed in the base portion 71. In the electricity storage device 10 of the sixth modification, when the internal pressure of the exterior body 40 increases, the release portion 600X is likely to break (rupture) before other portions, thereby releasing gas and the like. Therefore, the electricity storage device 10 of the sixth modification can achieve the same effects as the electricity storage device 10 of the embodiment.

[0103] 2-7. Seventh Modification In the above-described embodiment, at least a portion of the covering portion 72 of the lid main body 70 may be configured to include a shape memory alloy that has a curved shape at a predetermined temperature. In the seventh modification, the release portion 700X includes a portion of the lid main body 70 that is configured to include a shape memory alloy. FIGS. 14 and 15 are cross-sectional views of the electricity storage device 10 of the seventh modification in a state in which the internal pressure has increased and the release portion 700X has been destroyed. Before the temperature increases, the covering portion 72 of the electricity storage device 10 of the seventh modification has a linear shape as shown in FIG. 6 and the like. However, when the temperature increases with the increase in internal pressure, it deforms as shown in FIG. 14 or 15. In the examples shown in FIGS. 14 and 15, the covering portion 72 deforms in a curved shape. The covering portion 72 may also deform in a bent shape. That is, the power storage device 10 of the seventh modification is configured so that, when the temperature of the exterior body 40 rises as the internal pressure of the exterior body 40 rises, the portion of the lid main body 70 containing the shape memory alloy returns to its original shape, causing partial destruction of the exterior body 40. Partial destruction of the exterior body 40 includes at least one of destruction of the portion of the lid main body 70 containing the shape memory alloy and destruction of elements near the portion of the lid main body 70 containing the shape memory alloy, such as the exterior film 50 and the covering body 90. In the power storage device 10 of the seventh modification, when the internal pressure of the exterior body 40 rises, the release portion 700X is likely to break (rupture) before other portions, causing the release of gas or the like. Therefore, the power storage device 10 of the seventh modification can achieve the same effects as the power storage device 10 of the embodiment.

[0104] 2-8. Eighth Modification In the above embodiment, the electricity storage device 10 may have a release portion 800X instead of or in addition to the release portion 100X. The release portion 800X is a portion where the bond strength between the lid main body 70 and the covering body 90 is lower than the bond strength between the covering body 90 and the exterior film 50. FIG. 16 is a cross-sectional view of the electricity storage device 10 of the eighth modification in a state where the internal pressure has increased and the release portion 800X has been broken. In the electricity storage device 10 of the eighth modification, when the internal pressure of the exterior body 40 increases, the lid main body 70 is likely to peel off from the covering body 90 while the bond between the exterior film 50 and the covering body 90 is maintained, resulting in the release of gas or the like. Therefore, the electricity storage device 10 of the eighth modification can achieve the same effects as the electricity storage device 10 of the embodiment. Note that Figure 16 shows the entire lid body 70 peeled off from the covering body 90, but depending on the area in which the release section 800X is formed, the lid body 70 may be partially peeled off from the covering body 90.

[0105] 2-9. Ninth Modification FIG. 17 is a cross-sectional view of an electricity storage device 10 according to a ninth modification. The electricity storage device 10 according to the ninth modification includes a discharge portion 900X. The discharge portion 900X has a through-hole 971X formed in the base portion 71 of the lid main body 70, and a barrier film 910. The through-hole 971X penetrates the first surface 71A and the second surface 71B of the base portion 71. The barrier film 910 is bonded to the first surface 71A of the base portion 71 so as to close the through-hole 971X. The barrier film 910 may be bonded to the second surface 71B of the base portion 71 so as to close the through-hole 971X. The barrier film 910 may be disposed inside the lid main body 70 in the F-B direction so as to close the through-hole 971X. The barrier film 910 is a film including the barrier layer 52 of the exterior film 50 exemplified in the embodiment. In the ninth modification, the through-hole 971X may be closed by the covering body 90, and the barrier film 910 may be joined to the portion of the covering body 90 that closes the through-hole 971X. In the electricity storage device 10 of the ninth modification, when the internal pressure of the exterior body 40 increases, the barrier film 910 of the release portion 700X is likely to break (rupture) before other portions, causing the release of gas, etc. Therefore, the electricity storage device 10 of the ninth modification can achieve the same effects as the electricity storage device 10 of the embodiment.

[0106] <2-10. Tenth Modification> When the power storage device 10 includes at least two lid bodies 60, as in the power storage device 10 of the embodiment, the breaking strength of one of the lid bodies 60 may be configured to be lower than the breaking strength of the other lid body 60. The breaking strength of the lid body 60 is determined by the pressure at which the lid body 60 breaks when the lid body 60 is clamped with a jig and air pressure is applied from the first surface 71A or the second surface 71B using a leak tester. In the tenth modification, the release portion 100X is formed in one of the lid bodies 60. The difference between the breaking strength of one lid body 60 and the breaking strength of the other lid body 60 can be selected arbitrarily, but from the viewpoint of suitably forming the release portion 100X, it is preferably 0.05 MPa or more, and more preferably 0.1 MPa or more. In the electricity storage device 10 of the tenth modification, when the internal pressure of the exterior body 40 increases, one of the lid bodies 60 is likely to break (rupture) before the other lid body 60, resulting in the release of gas, etc. Therefore, the electricity storage device 10 of the tenth modification can achieve the same effect as the electricity storage device 10 of the embodiment.

[0107] 2-11. Eleventh Modification When the power storage device 10 includes at least two lid bodies 60, as in the power storage device 10 of the embodiment, the bonding strength of the second sealing portion 100B of one lid body 60 may be configured to be lower than the bonding strength of the second sealing portion 100B of the other lid body 60. In this case, the release portion 100X is formed in the second sealing portion 100B corresponding to one of the lid bodies 60. In the power storage device 10 of the eleventh modification, when the internal pressure of the exterior body 40 increases, the second sealing portion 100B corresponding to one of the lid bodies 60 is likely to break (peel off) before the other lid body 60, thereby releasing gas or the like. Therefore, the power storage device 10 of the eleventh modification can achieve the same effects as the power storage device 10 of the embodiment.

[0108] <2-12. Twelfth 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 twelfth modification, it is preferable that the electrode terminal be joined to the second surface 71B of the lid body 60. It is preferable that the length of the electrode terminal in the FB direction is such that it is exposed from the portion of the exterior film 50 that protrudes outward beyond the lid body 60.

[0109] <2-13. Thirteenth 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.

[0110] 2-14. Fourteenth Modification In the above embodiment, the outer shape of the exterior body 40 can be changed as desired. The outer shape of the exterior body 40 may be a cylinder, a prism, or a cube.

[0111] 10: Electricity storage device 20: Electrode body 40: Exterior body 50: Exterior film 60, 260, 360: Lid body 70, 570, 670: Lid body 100B: Second sealing portion (lid sealing portion) 100X: Emission portion 200X: Emission portion 300X: Emission portion 400X: Emission portion 500X: Emission portion 600X: Emission portion 700X: Emission portion 800X: Emission portion 900X: Emission portion 910: Barrier film 971X: Through-hole

Claims

1. An electricity storage device comprising: an electrode body; and an exterior body that seals the electrode body, wherein the exterior body has an exterior film that wraps the electrode body, a lid that seals the electrode body together with the exterior film, and a release section that is configured to be able to release at least one of a gas and an electrolyte by being partially ruptured when the internal pressure of the exterior body increases.

2. The electricity storage device according to claim 1, wherein the lid body has a lid main body including a portion joined to the exterior film, and the release section includes a portion of the lid main body that is partially thinned.

3. The electricity storage device according to claim 1, wherein the lid body has a lid main body including a portion joined to the exterior film, and the release portion includes a portion of the lid main body in which a recess is formed.

4. The energy storage device according to claim 1, wherein the exterior body comprises at least two lids, one of the lids has a breaking strength lower than the breaking strength of the other lid, and the release portion is formed in one of the lids.

5. The energy storage device according to claim 1, wherein the exterior body includes at least two lid bodies, the exterior body has a lid sealing portion where the lid body and the exterior film are joined, the joining strength of the lid sealing portion of one of the lid bodies is lower than the joining strength of the lid sealing portion of the other of the lid bodies, and the release portion is formed in the lid sealing portion of one of the lid bodies.

6. The energy storage device according to claim 1, wherein the exterior body has a lid sealing portion where the lid body and the exterior film are joined, and the release portion includes a portion of the lid sealing portion where the joining strength is partially reduced.

7. The energy storage device according to claim 1, wherein the lid body has a lid main body and a covering body that joins the lid main body and the exterior film, and the release portion is a portion where the bonding strength between the lid main body and the covering body is lower than the bonding strength between the covering body and the exterior film.

8. The energy storage device of claim 1, wherein the lid body has a lid main body joined to the exterior film, at least a portion of the portion of the lid main body joined to the exterior film is composed of a shape memory alloy, the release portion includes a portion of the lid main body composed of the shape memory alloy, and the exterior body is configured such that when the temperature of the exterior body increases due to an increase in internal pressure of the exterior body, the portion of the lid main body composed of the shape memory alloy returns to its original shape, thereby partially destroying the exterior body.

9. The electricity storage device according to claim 1, wherein the release section has a through hole formed in the lid body and a barrier film closing the through hole.

10. A lid body used as an exterior body for an electricity storage device, the lid body having a lid main body, the lid main body including a portion that can be broken when the internal pressure of the exterior body increases and that is partially thinned.

11. A lid body used as an exterior body for an electricity storage device, the lid body having a lid main body, the lid main body including a portion that breaks when the internal pressure of the exterior body increases, or a portion that can destroy an element that constitutes the exterior body, and a portion having a recess formed therein.

12. A lid body used as an exterior body for an electricity storage device, the lid body having a lid main body joined to an exterior film that constitutes the exterior body, and at least a portion of the portion of the lid main body joined to the exterior film is composed of a shape memory alloy.

13. 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 having an exterior film that wraps the electrode body, a lid that seals the electrode body together with the exterior film, and a release portion configured to be able to release at least one of gas and electrolyte when ruptured when internal pressure of the exterior body increases, the method for manufacturing an electricity storage device including a step of forming the release portion.

Images