Power storage device, lid body, and lid unit

Abstract

A power storage device according to the present invention comprises an electrode body and an exterior body that seals the electrode body. The exterior body includes: an exterior film that wraps around the electrode body such that an opening is formed; and a lid body that is placed on the opening. The electrode body includes a corner section at which an R surface is formed, the lid body includes a corner section at which an R surface is formed, and the absolute value of the difference between the radius of curvature of the corner section of the electrode body and the radius of curvature of the corner section of the lid body is 10 mm or less.

Description

Electricity storage device, lid body, lid unit

[0001] The present invention relates to an electricity storage device, a lid body, and a lid unit.

[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 so as to form an opening, and a lid that is placed over the opening. The exterior film and the lid are joined together.

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

[0004] In the above-described electricity storage device, for example, the electrode body and the lid body may have corners with rounded surfaces. In this case, if the shapes of the corners of the electrode body and the lid body differ significantly, the exterior film may not conform to the electrode body, and the adhesion between the exterior film and the electrode body may decrease.

[0005] An object of the present invention is to provide an electricity storage device in which an electrode assembly can be suitably held by an exterior film, a lid body used in this electricity storage device, and a lid unit including this lid body.

[0006] An energy storage device according to a first aspect of the present invention comprises an electrode body and an exterior body that seals the electrode body, the exterior body including an exterior film that wraps the electrode body so as to form an opening, and a lid body that is placed in the opening, the electrode body having a corner with an R-surface, the lid body having a corner with an R-surface, and the absolute value of the difference between the radius of curvature of the corner of the electrode body and the radius of curvature of the corner of the lid body is 10 mm or less.

[0007] An electricity storage device according to a second aspect of the present invention is the electricity storage device according to the first aspect, wherein the radius of curvature of the corner of the lid body is smaller than the radius of curvature of the corner of the electrode body.

[0008] An electricity storage device according to a third aspect of the present invention is the electricity storage device according to the first or second aspect, wherein the radius of curvature of the corner of the lid is 0.05 mm or more.

[0009] An electricity storage device according to a fourth aspect of the present invention is the electricity storage device according to any one of the first to third aspects, wherein the corner of the lid body and the corner of the electrode body face each other.

[0010] A lid according to a fifth aspect of the present invention is a lid used as an exterior body for an electricity storage device, and has at least one corner portion formed with a rounded surface, and the radius of curvature of the corner portion is 20 mm or less.

[0011] A lid unit according to a sixth aspect of the present invention comprises the lid body according to the fifth aspect and an electrode terminal joined to the lid body.

[0012] According to the electricity storage device, the lid body used in the electricity storage device, and the lid unit including the lid body of the present invention, the electrode assembly can be suitably held by the exterior film.

[0013] 6 is a perspective view of an electricity storage device according to an embodiment. FIG. 1B is a diagram relating to a method for measuring the seal strength of a second sealing portion of the electricity storage device of FIG. 1A. FIG. 1C is a perspective view showing the outer shape of an electrode body included in the electricity storage device of FIG. 1A. FIG. 2 is a diagram showing the outer shape of the front of the electrode body of FIG. 2. FIG. 1D is a cross-sectional view showing the layer structure of an exterior film included in the electricity storage device of FIG. 1A. FIG. 1E is a diagram showing the exterior film included in the electricity storage device of FIG. 1A in an unfolded state. FIG. 1F is a cross-sectional view taken along line D6-D6 of FIG. 1A. FIG. 6 is a side view of the lid body in a state where the exterior film of FIG. 6 is omitted. FIG. 6 is a plan view of the lid body in a state where the exterior film of FIG. 6 is omitted. FIG. 7 is a flowchart showing an example of a manufacturing process for the electricity storage device of FIG. 1A. FIG. 8 is a cross-sectional view of a lid body included in an electricity storage device of a modified example. FIG. 9 is a cross-sectional view of a lid body included in an electricity storage device of another modified example.

[0014] 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.

[0015] 1. Embodiments 1-1. Configuration of Electricity Storage Device FIG. 1A is a plan view schematically showing an electricity storage device 10 of a first embodiment. FIG. 1B is a diagram relating to a method for measuring the seal strength of a second sealing portion 80 of the electricity storage device 10. FIG. 2 is a perspective view showing the outer shape of an electrode body 20 included in the electricity storage device 10 of FIG. 1A. FIG. 3 is a diagram showing the outer shape of the front of the electrode body 20 of FIG. 2. FIG. 4 is a cross-sectional view showing the layer structure of an exterior film 50 included in the electricity storage device 10 of FIG. 1A. FIG. 5 is a diagram showing the exterior film 50 included in the electricity storage device 10 of FIG. 1A in an unfolded state. FIG. 6 is a cross-sectional view taken along line D6-D6 in FIG. 1A. FIG. 7 is a side view of a lid body 60 included in the electricity storage device 10 of FIG. 1A. FIG. 8 is a plan view of the lid body 60 of FIG. 7. 1A, the direction of the arrow UD indicates the thickness direction of the power storage device 10, the direction of the arrow LR indicates the width direction of the power storage device 10, and the direction of the arrow FB indicates the depth direction of the power storage device 10. The directions indicated by the arrows UDLRFB are the same in the subsequent figures.

[0016] 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.

[0017] As shown in Fig. 2, in this embodiment, the electrode body 20 has a front surface 21, a back surface 22, an upper surface 23, a lower surface 24, a first side surface 25, and a second side surface 26. The front surface 21 faces one of the lid bodies 60. The back surface 22 faces the other of the lid bodies 60. The upper surface 23 constitutes one of a pair of first surfaces 41 of the exterior body 40, which will be described later. The lower surface 24 constitutes the other of the pair of first surfaces 41 of the exterior body 40, which will be described later. The first side surface 25 constitutes one of a pair of second surfaces 42 of the exterior body 40, which will be described later. The second side surface 26 constitutes the other of the pair of second surfaces 42 of the exterior body 40, which will be described later.

[0018] As shown in Fig. 3, the electrode body 20 has corners 20A, 20B, 20C, and 20D. Corners 20A, 20B, 20C, and 20D have rounded surfaces. Corner 20A is formed at the boundary between the upper surface 23 and the first side surface 25. Corner 20B is formed at the boundary between the upper surface 23 and the second side surface 26. Corner 20C is formed at the boundary between the first side surface 25 and the lower surface 24. Corner 20D is formed at the boundary between the second side surface 26 and the lower surface 24. Note that in Fig. 2, the rounded shapes of corners 20A to 20D are omitted for simplicity of illustration.

[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. When the lid body 60 described below is made of, for example, metal, 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, copper, etc. 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, etc., and the electrode terminal 30 connected to the negative electrode is usually made of copper, nickel, etc. 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.

[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 so as to have an opening 40A. In this embodiment, the exterior film 50 is wrapped around the electrode body 20 so as to have the opening 40A. The lid 60 is disposed on the side of the electrode body 20 so as to close the opening 40A. Note that the electrode body 20 may be housed inside the exterior film 50 that is configured in a cylindrical shape so as to form the opening 40A, and the opening 40A may be closed by the lid 60.

[0022] An adhesive film 31 is preferably bonded to the electrode terminal 30 from the viewpoint of favorable adhesion to the lid 60. The adhesive film 31 can be any film that can bond the metal electrode terminal 30 and the resin lid 60. For example, the adhesive film 31 can be a polyolefin resin such as a polyethylene resin or a polypropylene resin, a cyclic polyolefin resin, or an acid-modified polyolefin resin obtained by graft-modifying these polyolefin resins with an acid such as maleic anhydride. The adhesive film 31 can be a single-layer film or a film of two or more layers. In this embodiment, the adhesive film 31 is bonded to substantially the entire portion of the electrode terminal 30 that is covered by the lid 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. 4 , 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. The exterior film 50 may be formed by laminating the heat-sealable resin layer 53, the base material layer 51, the barrier layer 52, and the heat-sealable resin layer 53 in this order. The exterior film 50 may be formed by laminating the heat-sealable resin layer 53, the barrier layer 52, and the heat-sealable resin layer 53 in this order. The first sealed portion 70, described below, may be formed by joining the outermost layer and the innermost layer of the exterior film 50. The exterior film 50 does not need to include all of these layers; for example, the barrier layer 52 may not be included. That is, the exterior film 50 may be formed by any flexible and easily bendable material, such as a resin film. The exterior film 50 is preferably heat-sealable.

[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 or a biaxially stretched polybutylene terephthalate (PBT) film, and the stretched polyamide resin layer is more preferably a biaxially stretched nylon (ONy) film. The base layer 51 may be configured to include both a stretched polyester resin layer and a stretched polyamide resin layer. From the viewpoint of film strength, the thickness of the base layer 51 is preferably, for example, 5 to 300 μm, and more preferably 20 to 150 μm.

[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 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.

[0027] 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.

[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 defined by JIS H4160:1994 A8021H-H18, JIS H4160:1994 A8079H-H18, JIS H4000:2014 A8021P-H14, or JIS H4000:2014 A8079P-H14.

[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 or conformability, 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] 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, approximately 9 to 200 μm. The thickness of the barrier layer 52 is preferably approximately 85 μm or less, more preferably approximately 50 μm or less, even more preferably approximately 40 μm or less, and particularly preferably approximately 35 μm or less. The thickness of the barrier layer 52 is preferably approximately 10 μm or more, even more preferably approximately 20 μm or more, and more preferably approximately 25 μm or more. Preferred thickness ranges for the barrier layer 52 include approximately 10 to 85 μm, approximately 10 to 50 μm, approximately 10 to 40 μm, approximately 10 to 35 μm, approximately 20 to 85 μm, approximately 20 to 50 μm, approximately 20 to 40 μm, approximately 20 to 35 μm, approximately 25 to 85 μm, approximately 25 to 50 μm, approximately 25 to 40 μm, and approximately 25 to 35 μm. When the barrier layer 52 is made of an aluminum alloy foil, the above-mentioned range is particularly preferable. 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, because the rigidity of the exterior film 50 is increased, when the exterior film 50 is wrapped around the electrode body 20, the exterior film 50 can be suitably wrapped around the electrode body 20. Furthermore, when the capacity of the electricity storage device is increased, the weight of the electricity storage device increases, but 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.

[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 when the exterior film 50 is formed or wound, 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 particularly 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 forming.

[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 1 mm, more preferably 0.5 mm. When the buffer layer is made of rubber, the upper limit of the buffer layer thickness is preferably 10 mm, more preferably 5 mm, and even more preferably 2 mm. When the buffer layer is made of rubber, the preferred ranges of the buffer layer thickness are 1 mm to 10 mm, 1 mm to 5 mm, 1 mm to 2 mm, 0.5 mm to 10 mm, 0.5 mm to 5 mm, and 0.5 mm to 2 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] The lid 60 has, for example, a rectangular parallelepiped shape and is made of, for example, a resin material. The lid 60 may be a metal molded product. The material constituting the lid 60 may include at least two or more materials selected from a metal oxide, a carbon material, and a rubber material. The material may include a metal oxide, a carbon material, and a rubber material.

[0040] The lid 60 is preferably made up of a resin material. Here, "made up of a resin material" means that, when the entire material constituting the lid 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 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] 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.

[0043] 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.

[0044] 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.

[0045] The melt mass flow rate of the resin material contained in the material constituting the lid body 60 is preferably in the range of 1 g / 10 min to 80 g / 10 min, and more preferably in the range of 5 g / 10 min to 60 g / 10 min. The melt mass flow rate is measured based on JIS K7210-1:2014.

[0046] The lid 60 may be configured to contain a conductive material. "Containing a conductive material" means that, when the entire material constituting the lid 60 is taken as 100% by mass, the content of the conductive material is 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. In other words, the material constituting the lid 60 can contain, in addition to the conductive material, a material other than the conductive material.

[0047] 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. Since the electrode terminal 30 can be omitted from the electricity storage device 10, the configuration of the electricity storage device 10 can be simplified.

[0048] When the lid 60 contains a conductive material, the lid 60 may be bonded to the exterior film 50 via an adhesive film. 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 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 .

[0049] 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.

[0050] The adhesive film preferably has adhesive properties. When the second sealing portion 80 (described later) is formed with the adhesive film disposed between the exterior film 50 and the lid 60, the adhesive film is less likely to shift position relative to the lid 60 and the exterior film 50. By incorporating a tackifier resin into the heat-sealable resin layer of the adhesive film, adhesive properties can be imparted to the adhesive film. Examples of the tackifier resin include amorphous polyolefins. Examples of amorphous polyolefins include amorphous polypropylene and copolymers of amorphous propylene and other α-olefins. The content of the tackifier resin relative to the base material constituting the heat-sealable resin is preferably 10 to 20% by weight or less.

[0051] The lid body 60 has a lid main body 60A. The lid main body 60A has a first surface 61, a second surface 62, and a lid seal portion 63. The first surface 61 faces the electrode assembly 20. The second surface 62 is the surface opposite the first surface 61. The lid seal portion 63 connects the first surface 61 and the second surface 62 and is heat-sealed to the heat-fusible resin layer 53 of the exterior film 50. The lid seal portion 63 includes a first seal surface 63A, a second seal surface 63B, a third seal surface 63C, and a fourth seal surface 63D. The first seal surface 63A forms the top surface of the lid body 60. The first seal 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 seal surface 63B and the third seal surface 63C are connected to the first seal surface 63A and form side surfaces of the lid body 60. The second sealing surface 63B and the third sealing 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 perpendicular to each other in a front view of the lid 60. The first direction and the second direction do not have to be perpendicular to each other in a front view of the lid 60. The fourth sealing surface 63D forms the lower surface of the lid 60. The fourth sealing surface 63D extends in the first direction (LR direction in this embodiment) in a front view of the lid 60.

[0052] The lid seal portion 63 further includes corners 64, 65, 66, and 67. The corner 64 is formed to include the boundary between the first seal surface 63A and the second seal surface 63B. The corner 65 is formed to include the boundary between the first seal surface 63A and the third seal surface 63C. The corner 66 is formed to include the boundary between the fourth seal surface 63D and the second seal surface 63B. The corner 67 is formed to include the boundary between the fourth seal surface 63D and the third seal surface 63C. The corners 65 to 67 have rounded surfaces. This prevents the exterior body 40 from being deformed, such as by wrinkles being formed in the exterior film 50, during the manufacturing process of the energy storage device 10 or when the finished energy storage device 10 is evacuated. Furthermore, the corners 65 to 67 are less susceptible to external impacts than if the corners 65 to 67 were right angles. This prevents the exterior body 40 from being damaged. In FIG. 1, the rounded shapes of the corners 65 to 67 are omitted for the sake of simplicity.

[0053] The corner 64 faces the corner 20A of the electrode body 20. The corner 65 faces the corner 20B of the electrode body 20. The corner 66 faces the corner 20C of the electrode body 20. The corner 67 faces the corner 20D of the electrode body 20.

[0054] 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 sealing surfaces 63A, 63B, 63C, and 63D of the lid body 60 have a certain thickness so that the sealing surfaces 63A, 63B, 63C, and 63D of the lid body 60 can be suitably heat-sealed to the exterior film 50 when forming the second sealing portion 80 described below. The minimum thickness 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 body 60 is, for example, 20 mm, more preferably 15 mm, and even more preferably 10 mm. The maximum thickness of the lid body 60 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] From the viewpoint of appropriately heat-sealing the lid 60 and the exterior film 50 together, it is preferable that the material constituting the lid 60 and the material constituting the heat-sealable resin layer 53 of the exterior film 50 are primarily made of the same material. In this embodiment, examples of the material constituting the lid 60 include polyester resins such as polyethylene terephthalate resins and polybutylene terephthalate resins, polyolefin resins such as polyethylene resins, fluorine-based resins and polypropylene resins, cyclic polyolefin resins, and acid-modified polyolefin resins obtained by graft-modifying these polyolefin resins with an acid such as maleic anhydride. From the viewpoint of appropriately heat-sealing the lid 60 and the exterior film 50 together, it is preferable that the material constituting the lid 60 and the material constituting the heat-sealable resin layer 53 of the exterior film 50 are primarily made of the same material. In this embodiment, the main material of the lid 60 and the heat-sealable resin layer 53 is, for example, a polyolefin resin such as a polyethylene resin or a polypropylene resin, or an acid-modified polyolefin resin obtained by graft-modifying these polyolefin resins with an acid such as maleic anhydride. The main material refers to, for example, a material that accounts for 50% or more of the materials contained in the constituent elements.

[0056] In this embodiment, a through hole 60X into which the electrode terminal 30 is inserted is formed in the lid body 60. The through hole 60X penetrates the first surface 61 and the second surface 62. When the electrode body 20 is wrapped in the exterior film 50, 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. In another example, the electrode terminals 30 may protrude to the outside of the exterior body 40 from between the sealing surfaces 63A, 63B, 63C, 63D of the lid body 60 and the exterior film 50. In this case, the through-holes 60X may not be formed in the lid body 60. In the electricity storage device 10, the lid body 60 and the electrode terminals 30 are provided as separate bodies, but the lid body 60 and the electrode terminals 30 may be formed integrally. Note that even when the electrode terminals 30 do not protrude from the edge of the exterior body 40, the lid body 60 may not have the through-holes 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 so as to have an opening 40A, and then heat-sealing the opposing surfaces of the exterior film 50 (heat-fusible resin layer 53) together.

[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. 5 . The first sealed portion 70 extends in the longitudinal direction (FB 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 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 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 42 or the first surface 41 of the exterior body 40.

[0059] In this embodiment, the second sealing portion 80 is formed by heat-sealing the heat-fusible resin layer 53 of the exterior film 50 and the lid seal portion 63 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 63 of the lid body 60 may be referred to as the seal strength of the second sealing portion 80. Note that the seal strength of the second sealing portion 80 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 63, i.e., the lid seal portion 63 extending in the LR (width) direction in FIG. 1A .

[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 41 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 in 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 of the long sides of the lid seal portions 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 unit 80 is preferably 300 N / 15 mm or less. A preferred range for the seal strength of the second sealing portion 80 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.

[0062] In this embodiment, the lid body 60 has a protrusion 68 protruding from the lid seal portion 63 to prevent gaps from forming between the exterior film 50 and the lid body 60. The protrusion 68 may be formed integrally with the lid main body 60A, or may be formed separately from the lid main body 60A and then joined to the lid main body 60A. In this embodiment, the protrusion 68 is formed integrally with the lid main body 60A. The position of the lid seal portion 63 at which the protrusion 68 is formed 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 70X of the first sealing portion 70 and the lid body 60. In particular, when the base 70X of the first sealing portion 70 is located at a corner 64 to a corner 67 of the lid body 60, the resin filling between the base 70X of the first sealing portion 70 and the lid body 60 is likely to be reduced. For this reason, it is preferable that the protrusion 68 be formed in the lid seal portion 63 at the location where the base 70X of the first sealing portion 70 is located. In this embodiment, the base 70X of the first sealing portion 70 is located at the corner 64 of the lid body 60. For this reason, the protrusion 68 is preferably formed at the corner 64 of the lid seal portion 63. In this embodiment, the first sealing portion 70 is sealed with the protrusion 68 sandwiched between them. Note that the protrusion 68 may be formed on at least one of the first seal surface 63A, the second seal surface 63B, the third seal surface 63C, the fourth seal surface 63D, the corner 65, the corner 66, and the corner 67.

[0063] The shape of the protrusion 68 can be selected arbitrarily. In this embodiment, the shape of the protrusion 68 is plate-like. The thickness of the protrusion 68 can be selected arbitrarily. In this embodiment, the thickness of the protrusion 68 becomes thinner as it moves away from the corner 64. In other words, the protrusion 68 has a tapered shape as it moves away from the corner 64. The thickness of the protrusion 68 may be constant, or may become thicker as it moves away from the corner 64.

[0064] The direction in which the protrusion 68 extends can be selected arbitrarily. In this embodiment, the protrusion 68 extends along a first direction (in this embodiment, the LR direction). The protrusion 68 may also extend along a second direction (in this embodiment, the UD direction).

[0065] The length of the protrusion 68 can be selected arbitrarily within a range equal to or less than the length of the first sealing portion 70. For example, the length of the protrusion 68 may be substantially equal to the length of the first sealing portion 70, or may be 30% to 50% of the length of the first sealing portion 70.

[0066] If the shapes of the corners 20A to 20D of the electrode body 20 and the corners 65 to 67 of the lid body 60, more specifically, the radius of curvature of the corners 20A to 20D and the radius of curvature of the corners 65 to 67, are significantly different, the exterior film 50 will not conform to the electrode body 20, and there is a risk that the adhesion between the exterior film 50 and the electrode body 20 will be reduced. For this reason, the exterior film 50 will not be able to hold the electrode body 20 properly.

[0067] In this embodiment, from the viewpoint of suitably holding the electrode body 20 by the exterior film 50, the absolute value of the difference between the radius of curvature of any corner 20A to 20D of the electrode body 20 and the radius of curvature of any corner 65 to 67 of the lid body 60 is 10 mm or less. The absolute value of the difference between the radius of curvature of any corner 20A to 20D of the electrode body 20 and the radius of curvature of any corner 65 to 67 of the lid body 60 is more preferably 5 mm or less, and even more preferably 3 mm or less. Note that in this embodiment, the radius of curvature of the corners 20A to 20D of the electrode body 20 includes the radius of curvature of the corners corresponding to the corners 20A to 20D that appear on the exterior of the exterior body 40 when the electrode body 20 is wrapped in the exterior film 50.

[0068] In this embodiment, the radii of curvature of the corners 20A to 20D are measured at positions of the electrode body 20 close to the lid body 60. The radii of curvature of the corners 20A to 20D are measured values ​​measured with an R gauge after wrapping the exterior film 50 in contact with the outer surface of the electrode body 20 while tension is applied to the exterior film 50.

[0069] From the viewpoint of more suitably holding the electrode body 20 by the exterior film 50, the absolute value of the difference in the radii of curvature between opposing corners of the corners 20A to 20D of the electrode body 20 and the corners 65 to 67 of the lid body 60 is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 3 mm or less. That is, the absolute value of the difference in the radii of curvature between the corner 20B of the electrode body 20 and the corner 65 of the lid body 60 is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 3 mm or less. The absolute value of the difference in the radii of curvature between the corner 20C of the electrode body 20 and the corner 66 of the lid body 60 is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 3 mm or less. The absolute value of the difference between the radius of curvature of the corner 20D of the electrode body 20 and the radius of curvature of the corner 67 of the lid body 60 is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 3 mm or less.

[0070] Furthermore, if the radius of curvature of any of the corners 65 to 67 of the lid body 60 is larger than the radius of curvature of any of the corners 20A to 20D of the electrode body 20, the perimeter of the exterior film 50 joined to the lid body 60 will be longer than the perimeter of the electrode body 20, which may reduce the adhesion between the exterior film 50 and the electrode body 20. For this reason, the exterior film 50 may not be able to hold the electrode body 20 properly.

[0071] For this reason, the radius of curvature of any of the corners 65 to 67 of the lid body 60 is preferably smaller than the radius of curvature of any of the corners 20A to 20D of the electrode assembly 20. From the viewpoint of more suitably holding the electrode assembly 20 by the exterior film 50, the radius of curvature of the corners 65 to 67 of the lid body 60 is preferably smaller than the radius of curvature of the opposing corners 20A to 20D of the electrode assembly 20. In other words, the radius of curvature of the corner 65 of the lid body 60 is preferably smaller than the radius of curvature of the corner 20B of the electrode assembly 20. The radius of curvature of the corner 66 of the lid body 60 is preferably smaller than the radius of curvature of the corner 20C of the electrode assembly 20. The radius of curvature of the corner 67 of the lid body 60 is preferably smaller than the radius of curvature of the corner 20D of the electrode assembly 20.

[0072] The radius of curvature of at least one of the corners 65-67 of the lid body 60 can be selected arbitrarily as long as the absolute value of the difference from the radius of curvature of any one of the corners 20A-20D of the electrode body 20 is 10 mm or less. From the viewpoint of preventing the circumferential length of the exterior film 50 from increasing, the radius of curvature of at least one of the corners 65-67 of the lid body 60 is preferably 10 mm or less. From the viewpoint of suitably forming the corners 65-67 having a rounded surface in the lid body 60 and from the viewpoint of improving adhesion between the exterior film 50 and the lid body 60, the radius of curvature of at least one of the corners 65-67 of the lid body 60 is preferably 0.05 mm or more. From the viewpoint of preventing a significant difference in shape from the corners 20A-20D of the electrode body 20, the radius of curvature of at least one of the corners 65-67 is preferably 20 mm or less. The preferred range of the radius of curvature of at least one of the corners 65 to 67 of the lid 60 is 0.05 mm or more and 20 mm or less.

[0073] In the LR direction, the ratio of the portion of the lid body 60 with the largest outer diameter to the portion of the electrode body 20 with the largest outer diameter is preferably ±10% or less. In the UD direction, the ratio of the portion of the lid body 60 with the largest outer diameter to the portion of the electrode body 20 with the largest outer diameter is preferably ±10% or less.

[0074] 9 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, and a seventh step. The first step to the seventh step are performed, for example, by a manufacturing apparatus for the power storage device 10. Note that the first step to the seventh step are names of the steps in the method for manufacturing the power storage device 10 defined for convenience, and do not necessarily indicate the order of the steps.

[0075] In the first process of step S11, the manufacturing equipment joins the lid body 60 and the electrode terminal 30. By completing the second process, a pair of lid units 60Z in which the electrode terminal 30 is joined to the lid body 60 is completed.

[0076] The second step of step S12 is performed after the first step. In the second step, the manufacturing apparatus places a pair of lid units 60Z on the sides of the electrode body 20 and joins the electrode terminals 30 to the electrode body 20. Note that the manufacturing method for the electricity storage device 10 may include, instead of the first and second steps, a step of first joining the electrode body 20 to the electrode terminals 30 and then joining the lid body 60 to the electrode terminals 30 joined to the electrode body 20.

[0077] The third step of step S13 is performed after the second step. In the third step, the manufacturing apparatus wraps the exterior film 50 around the electrode assembly 20 and the lid body 60. In the third step, the manufacturing apparatus wraps 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.

[0078] The fourth step of step S14 is performed after the third step. In the fourth step, the manufacturing equipment forms a first sealing portion (hereinafter referred to as a "temporary first sealing portion") having an unsealed portion formed in a part thereof for injecting an electrolyte solution. In the temporary first sealing portion, the heat-sealable resin layers 53 of the exterior film 50 facing each other are joined together with the protruding portion 68 of the lid body 60 sandwiched between the exterior film 50. Note that if the power storage device 10 is, for example, an all-solid-state battery, the step of injecting an electrolyte solution is not necessary, and therefore, in the fourth step, the manufacturing equipment forms a first sealing portion 70.

[0079] The fifth step of step S15 is performed after the fourth step. In the fifth step, the manufacturing apparatus forms the second sealing portion 80 by, for example, heat-sealing the heat-fusible resin layer 53 of the exterior film 50 and the lid seal portion 63 of the lid body 60. The fifth step preferably includes a first sealing step and a second sealing step. In the first sealing step, the manufacturing apparatus heat-seals the first sealing surface 63A, the second sealing surface 63B, the third sealing surface 63C, the fourth sealing surface 63D of the lid seal portion 63, and the protruding portion 68 including the corner portion 64, to the exterior film 50. The second sealing step is performed after the first sealing step. In the second sealing step, the manufacturing apparatus heat-seals the corner portions 65-67 to the exterior film 50. In the second sealing step, a heat seal bar having the same radius of curvature as the rounded surfaces of the corners 65-67 is preferably used.

[0080] The sixth step of step S16 is performed after the fifth step. In the sixth step, the manufacturing equipment injects an electrolyte solution through the unsealed portion formed in the temporary first sealing portion.

[0081] The seventh step of step S17 is performed after the sixth step. In the seventh step, the manufacturing apparatus heat-seals a portion of the temporary first sealed portion, including the unsealed portion, to form the first sealed portion 70. Note that, when the power storage device 10 is, for example, an all-solid-state battery, the sixth and seventh steps are omitted.

[0082] <1-3. Effects of the electricity storage device> In the electricity storage device 10, the absolute value of the difference between the radius of curvature of any corner 20A to 20D of the electrode body 20 and the radius of curvature of any corner 65 to 67 of the lid body 60 is 10 mm or less, and therefore the exterior film 50 can easily conform to the electrode body 20. Therefore, the exterior film 50 can suitably hold the electrode body 20.

[0083] [2. Modifications] The above-described embodiments are examples of possible forms of the electricity storage device and lid according to the present invention, and are not intended to limit the forms. The electricity storage device and lid according to the present invention may take forms different from those exemplified in the embodiments. Examples of such forms include forms in which part of the configuration of the embodiment is replaced, modified, or omitted, or forms in which a new configuration is added to the embodiment. Below are some examples of modifications of the embodiments. Note that the following modifications can be combined with each other as long as there is no technical contradiction.

[0084] <2-1> In the above embodiment, the protrusion 68 may be omitted from the lid 60. In this modification, from the viewpoint of suitably forming the first sealing portion 70, it is preferable that the corner 64 be a substantially right angle.

[0085] In another example, when the protrusion 68 is omitted from the lid body 60, a rounded surface may be formed at the corner 64. From the viewpoint of suitably holding the electrode body 20 by the exterior film 50, the absolute value of the difference between the radius of curvature of any one of the corners 20A to 20D of the electrode body 20 and the radius of curvature of the corner 64 of the lid body 60 is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 3 mm or less.

[0086] From the viewpoint of more suitably holding the electrode body 20 by the exterior film 50, the absolute value of the difference between the radius of curvature of the corner 20A of the electrode body 20 and the radius of curvature of the corner 64 of the lid body 60 is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 3 mm or less.

[0087] Furthermore, if the radius of curvature of the corner 64 of the lid body 60 is larger than the radius of curvature of any of the corners 20A to 20D of the electrode body 20, the perimeter of the exterior film 50 joined to the lid body 60 will be longer than the perimeter of the electrode body 20, which may reduce the adhesion between the exterior film 50 and the electrode body 20. As a result, the electrode body 20 cannot be held in place by the exterior film 50.

[0088] For this reason, the radius of curvature of the corner 64 of the lid body 60 is preferably smaller than the radius of curvature of any of the corners 20A to 20D of the electrode body 20. From the viewpoint of more suitably holding the electrode body 20 by the exterior film 50, the radius of curvature of the corner 64 of the lid body 60 is preferably smaller than the radius of curvature of the corner 20A of the electrode body 20. Note that the radius of curvature of the corner 64 of the lid body 60 may be equal to or larger than the radius of curvature of any of the corners 20A to 20D of the electrode body 20.

[0089] The radius of curvature of the corner 64 of the lid body 60 can be selected arbitrarily. From the viewpoint of preventing the circumferential length of the exterior film 50 from increasing, the radius of curvature of the corner 64 of the lid body 60 is preferably 20 mm or less. From the viewpoint of suitably forming the corner 64 having a rounded surface on the lid body 60, the radius of curvature of the corner 64 of the lid body 60 is preferably 0.05 mm or more. From the viewpoint of preventing the shape of the corner 64 from differing significantly from the corners 20A to 20D of the electrode body 20, the radius of curvature of the corner 64 is preferably 20 mm or less. A preferred range for the radius of curvature of the corner 64 of the lid body 60 is 0.05 mm or more and 20 mm or less.

[0090] <2-2> In the above embodiment, it is possible to arbitrarily change the magnitude relationship between the radius of curvature of any of the corners 65 to 67 of the lid body 60 and the radius of curvature of any of the corners 20A to 20D of the electrode body 20. The radius of curvature of any of the corners 65 to 67 of the lid body 60 may be equal to or greater than the radius of curvature of any of the corners 20A to 20D of the electrode body 20.

[0091] <2-3> In the electricity storage device 10 of the above embodiment, the direction in which the protrusion 68 extends can be changed as desired. For example, as shown in Fig. 10 , the protrusion 68 may extend in a third direction that intersects the first direction (in the embodiment, the LR direction) and the second direction (in the embodiment, the UD direction) in a front view of the lid 60.

[0092] <2-4> In the electricity storage device 10 of the above embodiment, the configuration of the lid body 60 can be modified as desired. As shown in FIG. 11 , the lid body 60 may include a frame 60B that covers the lid main body 60A. In this modification, the lid main body 60A may be made of any material, such as metal, resin, or a composite material of metal and resin. The frame 60B may be made of a material that can be suitably sealed with the heat-sealable resin layer 53 of the exterior film 50, for example. In this modification, the lid seal portion 63 and the protrusion 68 of the lid body 60 are formed on the frame 60B.

[0093] <2-5> In the electricity storage device 10 of the above embodiment, the specific method for forming the protrusion 68 of the lid body 60 can be changed as desired. For example, the protrusion 68 may be formed by an adhesive film or the like that is bonded to the lid seal portion 63 of the lid main body 60A. In this modification, for example, the protrusion 68 may be formed by bonding a plurality of adhesive films to the lid seal portion 63 in an overlapping manner, or the protrusion 68 may be formed by bonding an adhesive film to the lid seal portion 63 in a flap shape.

[0094] <2-6> The energy storage device 10 of the above embodiment may have an adhesive film disposed between the exterior film 50 and the lid body 60 to suitably bond the exterior film 50 and the lid body 60. In this modification, for example, the lid body 60 with the adhesive film adhered thereto is attached to the openings 40A at both ends of the exterior body 40, and then the second sealing portion 80 is formed. For example, the adhesive film is wrapped around the lid body 60 so as to cover the entire surface of the lid seal portion 63 of the lid body 60. The adhesive film is preferably configured to be wider overall than the lid seal portion 63 of the lid body 60. In this case, the adhesive film can be easily bonded to the lid body 60. Furthermore, since the corners 64 to 67 of the lid seal portion 63 are covered by the adhesive film, the adhesion between the lid body 60 and the adhesive film is enhanced.

[0095] The adhesive film can be any film capable of adhering 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 materials, 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 bonded to the exterior film 50 is preferably made of the same material as the material constituting the heat-sealable resin layer 53 of the exterior film 50.

[0096] 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.

[0097] The adhesive film preferably has adhesive properties. When the second sealing portion 80 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.

[0098] <2-7> In the above embodiment, it is possible to arbitrarily select the position where the electrode terminal 30 is disposed. For example, the electrode terminal 30 may protrude from the first sealing portion 70.

[0099] 10: Electricity storage device 20: Electrode body 20A, 20B, 20C, 20D: Corner portion 40: Exterior body 40A: Opening 50: Exterior film 60: Lid body 60Z: Lid unit 64, 65, 66, 67: Corner portion

Claims

1. An electrode body; and an exterior body that seals the electrode body, The exterior body is an exterior film that wraps the electrode body so as to form an opening; A lid body disposed in the opening, The electrode body has a corner portion having a rounded surface, The lid has a corner portion having a rounded surface, The absolute value of the difference between the radius of curvature of the corner of the electrode body and the radius of curvature of the corner of the lid body is 10 mm or less. Energy storage device.

2. The radius of curvature of the corner of the cover is smaller than the radius of curvature of the corner of the electrode body. The power storage device according to claim 1 .

3. The radius of curvature of the corner of the lid is 0.05 mm or more. The electricity storage device according to claim 1 or 2.

4. The corner of the cover and the corner of the electrode body face each other. The electricity storage device according to claim 1 or 2.

5. A lid body used as an exterior body for an electricity storage device, the exterior body includes the lid body and an exterior film joined to the lid body, the lid has at least one corner portion having a rounded surface to be joined to the exterior film, The radius of curvature of the corner is 20 mm or less. Lid body.

6. The lid according to claim 5 , and an electrode terminal joined to the lid. Lid unit.