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

Abstract

To provide a power storage device having high sealability, a lid body used for the power storage device, a method of manufacturing the lid body, and a method of manufacturing the power storage device.SOLUTION: The power storage device includes an electrode body, an exterior film that wraps the electrode body, and a lid that seals the electrode body together with the exterior film. The lid includes a lid main body containing a conductive material, a covering body containing a resin material and covering a part of the lid main body, and a joining body joining the lid main body and the covering body.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an electricity storage device, a lid, a method for manufacturing a lid, and a method for manufacturing an electricity storage device. [Background technology]

[0002] Patent Document 1 discloses an example of an electricity storage device. This electricity storage device includes an electrode assembly including a current collector, an exterior body that seals the electrode assembly, and an electrode terminal connected to the current collector. The exterior body includes an exterior film that encases the electrode assembly, and a lid that is joined to the exterior film. The electrode terminal is inserted into a through-hole formed in the lid. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-123686 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described electricity storage device, if the lid is made of a metal material, the lid also functions as an electrode terminal, so that the electrode terminal can be omitted. This simplifies the configuration. However, if the lid is made of a metal material, it may not bond well with the heat-sealable resin layer of the exterior film, which may result in poor bonding. This may reduce the hermeticity of the electricity storage device.

[0005] An object of the present invention is to provide an electricity storage device with high sealing performance, a lid used in the electricity storage device, a method for manufacturing the lid, and a method for manufacturing the electricity storage device. [Means for solving the problem]

[0006] The energy storage device according to a first aspect of the present invention comprises an electrode body, an exterior film that wraps the electrode body, and a lid body that seals the electrode body together with the exterior film, and the lid body has a lid main body that contains a conductive material, a covering body that contains a resin material and covers the lid main body, and a bonding body that joins the lid main body and the covering body.

[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 bonded body contains a resin material having a polar group.

[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 thickness of the bonded body is smaller than the thickness of the covering body.

[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 bonded body is a coating film.

[0010] An electricity storage device according to a fifth aspect of the present invention is the electricity storage device according to any one of the first to fourth aspects, wherein the thickness of the bonded body is in the range of 0.5 μm to 20 μm.

[0011] An electricity storage device according to a sixth aspect of the present invention is the electricity storage device according to any one of the first to fourth aspects, wherein the bonded body is a film.

[0012] An electricity storage device according to a seventh aspect of the present invention is the electricity storage device according to any one of the first to fourth aspects or the sixth aspect, wherein the thickness of the bonded body is in the range of 5 μm to 500 μm.

[0013] An electricity storage device according to an eighth aspect of the present invention is the electricity storage device according to any one of the first to seventh aspects, further comprising a surface treatment layer formed on at least a part of the surface of the lid body that is to be joined to the assembly.

[0014] An electricity storage device according to a ninth aspect of the present invention is the electricity storage device according to any one of the first to eighth aspects, wherein a peak derived from Cr2p3 / 2 of a chromium compound is detected in the range of 576 eV to 581 eV by X-ray photoelectron spectroscopy analysis of at least a part of the surface of the lid body that is joined to the joined body.

[0015] An electricity storage device according to a tenth aspect of the present invention is the electricity storage device according to any one of the first to ninth aspects, wherein at least a part of the surface of the lid body that is joined to the joining body is a rough surface.

[0016] A lid body according to an eleventh aspect of the present invention is a lid body used as an exterior body for an electricity storage device, and comprises a lid body comprising a conductive material, a covering body comprising a resin material and covering a portion of the lid body, and a bonding body joining the lid body and the covering body.

[0017] A twelfth aspect of the present invention relates to a method for manufacturing a lid body used as an exterior body for an electricity storage device. The lid body includes a lid body containing a conductive material, a cover containing a resin material and covering the lid body, and a bonding member bonding the lid body and the cover body together. The method for manufacturing the lid body includes a step of bonding the lid body and the cover body together via the bonding member.

[0018] A thirteenth aspect of the present invention relates to a method for manufacturing an electricity storage device including an electrode assembly, an exterior film that encases the electrode assembly, and a lid that seals the electrode assembly together with the exterior film. The lid includes a lid body containing a conductive material, a cover that contains a resin material and covers a portion of the lid body, and a joint that joins the lid body and the cover. The method for manufacturing an electricity storage device includes a step of placing the lid body on the electrode assembly. [Effects of the Invention]

[0019] The electricity storage device, lid, method for manufacturing a lid, and method for manufacturing an electricity storage device according to the present invention can contribute to improving the sealing performance of the electricity storage device. [Brief explanation of the drawings]

[0020] [Figure 1A] FIG. 1 is a perspective view of an electricity storage device according to an embodiment. [Figure 1B] 1B is a diagram showing a method for measuring the seal strength of the second sealing portion of the electricity storage device in FIG. 1A. FIG. [Figure 2] 1B is a cross-sectional view showing the layer structure of an exterior film included in the electricity storage device of FIG. 1A. [Figure 3] FIG. 1B is a diagram showing the state in which the exterior film provided on the electricity storage device of FIG. 1A is unfolded. [Figure 4] 1B is a perspective view of the rear side of a lid provided in the electricity storage device of FIG. 1A. FIG. [Figure 5] FIG. 5 is a perspective view of the front side of the lid body of FIG. 4. [Figure 6] FIG. 1B is a cross-sectional view taken along line D6-D6 in FIG. 1A. [Figure 7] 1B is a cross-sectional view taken along line D7-D7 in FIG. 1A. [Figure 8A] FIG. 7 is a cross-sectional view showing an example of the layer structure of the bonded body of FIG. 6. [Figure 8B] FIG. 7 is a cross-sectional view showing another example of the layer structure of the bonded body of FIG. 6. [Figure 8C] FIG. 7 is a cross-sectional view showing another example of the layer structure of the bonded body of FIG. 6. [Figure 8D] FIG. 7 is a cross-sectional view showing another example of the layer structure of the bonded body of FIG. 6. [Figure 9] 1B is a flowchart showing an example of a method for manufacturing the electricity storage device of FIG. 1A. [Figure 10] FIG. 10 is an enlarged view of a flange portion of a lid provided in an electricity accumulation device according to a first modified example. [Figure 11] FIG. 11 is an enlarged view of a flange portion of a lid provided in an electricity accumulation device according to a second modified example. DETAILED DESCRIPTION OF THE INVENTION

[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 the power 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 120 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 the rear side of a lid body 60 included in the electricity storage device 10 of FIG. 1A. FIG. 5 is a perspective view of the front side of the lid body 60 of FIG. 4. FIG. 6 is a cross-sectional view taken along line D6-D6 in FIG. 1A. FIG. 7 is a cross-sectional view taken along line D7-D7 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 UD, LR, and FB are common to all subsequent figures.

[0023] The electricity 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 electricity 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, polycation 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. 7) is connected to the lid 60 .

[0025] The exterior body 40 seals the electrode assembly 20. The exterior body 40 includes an exterior film 50 and a lid 60. The exterior film 50 wraps the electrode assembly 20. In this embodiment, the exterior film 50 is wrapped around the electrode assembly 20. The lid 60 is disposed on the side of the electrode assembly 20 in the FB direction. In another example, the electrode assembly 20 may be housed inside an exterior film 50 configured in a cylindrical shape so that openings are formed at both ends in the FB direction, and the openings may be closed by the lid 60. In yet another example, the electrode assembly 20 connected to the lid 60 may be housed inside an exterior film 50 configured in a cylindrical shape so that openings are formed, and the openings may be closed by the lid 60.

[0026] For example, there is a method of forming a storage portion (recess) in the exterior film 50 through cold forming to store the electrode assembly 20. However, it is not necessarily easy to form a deep storage portion using this method. Attempting to form a deep storage portion (recess) through cold forming (for example, a forming depth of 15 mm) increases the likelihood of pinholes or cracks occurring in the exterior film 50, resulting in a decrease in battery performance. On the other hand, the exterior body 40 seals the electrode assembly 20 by wrapping the exterior film 50 around the electrode assembly 20, and therefore can easily seal the electrode assembly 20 regardless of the thickness of the electrode assembly 20. Note that in order to reduce the dead space between the electrode assembly 20 and the exterior film 50 and improve the volumetric energy density of the power storage device 10, it is preferable that the exterior film 50 be wrapped so as to contact the outer surface of the electrode assembly 20. Furthermore, in all-solid-state batteries, it is necessary to apply a high pressure uniformly from the outer surface of the battery to maximize battery performance, so it is necessary to eliminate the space between the electrode assembly 20 and the exterior film 50. Therefore, it is preferable that the exterior film 50 be wrapped so as to contact the outer surface of the electrode assembly 20.

[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. Note that the exterior film 50 does not need 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 flexible and easily bendable material, such as a resin film. Note that the exterior film 50 is preferably 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 assembly 20 and the lid 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 prevents pinholes from forming 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 prevented. Furthermore, from the viewpoint of increasing the tensile elongation of the exterior film 50, the stretched polyester resin layer is preferably a biaxially stretched polyester resin layer, and the stretched polyamide resin layer is preferably a biaxially stretched polyamide resin layer. Furthermore, from the viewpoint of excellent puncture strength or impact strength, the stretched polyester resin layer is more preferably a biaxially stretched polyethylene terephthalate (PET) film, and the stretched polyamide resin layer is more preferably a biaxially stretched nylon (ONy) film. The substrate layer 51 may be composed of both a stretched polyester resin layer and a stretched polyamide resin layer. The thickness of the base layer 51 is preferably, for example, 5 to 300 μm, and more preferably 5 to 150 μm, from the viewpoint of film strength.

[0031] The barrier layer 52 is a layer that prevents at least moisture from penetrating. The barrier layer 52 is bonded to the base 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. Other examples of the barrier layer 52 include resin films having at least one of these vapor-deposited films and resin layers. The barrier layer 52 may 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 metallic material may contain recycled metallic material. Examples of recycled metallic material include recycled aluminum alloy, stainless steel, titanium steel, and steel plate. These recycled materials can be obtained by known methods. Recycled aluminum alloy material can be obtained, for example, by the manufacturing method described in International Publication No. 2022 / 092231. The barrier layer 52 may be made solely of recycled material, or may be made of a mixture of recycled and virgin material. Note that recycled metallic material refers to metallic material that has been made reusable by collecting, isolating, and refining various products used in the market or waste from manufacturing processes. Furthermore, virgin metallic material refers to new metallic material refined from natural metallic resources (raw materials) and is not recycled material.

[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, and 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. 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 defined in JIS H4160:1994 A8021H-H18, JIS H4160:1994 A8079H-H18, JIS H4000:2014 A8021P-H14, or JIS H4000:2014 A8079P-H14. From the viewpoint of improving the mechanical strength of the packaging film 50, the aluminum alloy foil is preferably an aluminum alloy foil containing magnesium. In the aluminum alloy foil containing magnesium (100% by mass), the magnesium content is preferably 0.2 to 5.6% by mass, and more preferably 0.2 to 3.0% by mass. Examples of aluminum alloy foils containing magnesium include aluminum alloy foils having compositions specified in JIS H4000:2017 A5005P-O, JIS H4000:2017 A5050P-O, and JISH4000:2017 A5052P-O.

[0034] Examples of 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 can be used to 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 an 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 using 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 base 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 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 base layer 51 and the barrier layer 52 during heat sealing and between the base 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 viewpoints 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 with 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, and most preferably in the range of 1000 μm to 3000 μm.

[0042] When the buffer layer is made of rubber, the lower limit of the buffer layer thickness is preferably 0.5 mm, more preferably 1.0 mm. When the buffer layer is made of rubber, the upper limit of the buffer layer thickness is preferably 10 mm, more preferably 5.0 mm, and even more preferably 2.0 mm. When the buffer layer is made of rubber, the preferred ranges of the buffer layer thickness are 1.0 mm to 2.0 mm, 1.0 mm to 5.0 mm, 1.0 mm to 10 mm, 0.5 mm to 2.0 mm, 0.5 mm to 5.0 mm, and 0.5 mm to 10 mm.

[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 the manufacture of the energy storage device 10.

[0044] The lid body 60 has a lid main body 70, a cover 90 that covers the lid main body 70, and a joint 80. The lid main body 70 may have a protrusion that protrudes in the direction opposite to the electrode body 20. The protrusion is an element for outputting current to the outside and is connected to an external device. The protrusion may be, for example, an element for fixing the electricity storage device 10.

[0045] The lid body 70 is composed of a conductive material. "Composed of a conductive material" means that, when the entire material constituting the lid body 70 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 body 70 can contain, in addition to the conductive material, materials other than the conductive material. The lid body 70 preferably has a corrosion-resistant coating as described for the barrier layer 52.

[0046] The conductive material constituting the lid body 70 is, for example, a metal material. The metal material constituting the lid body 70 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 connected to the positive electrode is preferably made of aluminum or an aluminum alloy. The lid body 70 connected to the negative electrode is preferably made of nickel, copper, or a copper alloy. The material constituting the lid body 70 connected to the negative electrode may be nickel-plated copper. The material constituting the lid body 70 may include recycled metal material. The lid body 70 has a base 71 and a flange 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. The base 71 may have any shape, such as a cylinder, a prism, a rectangular parallelepiped, or a cube.

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

[0049] At least a portion of the surface 72X of the flange portion 72 is covered with the coating 90. In this embodiment, the entire surface 72X of the flange portion 72 is covered with the coating 90. An arbitrary portion of the lid body 70 is connected to the end 31 of the current collector 30. In the example shown in FIG. 7, the second surface 71B of the base 71 and the end 31 of the current collector 30 are connected. In another example, a connection portion may be formed at an arbitrary portion of the lid body 70 (e.g., the second surface 71B). The connection portion may, for example, protrude toward the electrode body 20. The connection portion is configured to include a conductive material. When the connection portion protrudes toward the electrode body 20, the end 31 of the current collector 30 is joined to an arbitrary portion of the connection portion. The connection portion may be a recess recessed from an arbitrary portion of the lid body 70 (e.g., the second surface 71B).

[0050] From the viewpoint of suitably joining the joining body 80 described later, the flange portion 72 may have at least one of a through hole, a recessed portion recessed on the side opposite the covering body 90, or a protrusion protruding toward the covering body 90.

[0051] The thickness HA (see FIG. 7 ) of the portion constituting the lid main body 70 can be selected arbitrarily. From the viewpoint of easily manufacturing the lid main body 70, the thickness HA is preferably 0.1 mm or more. On the other hand, if the volume of the lid main body 70 is large, when forming the second sealing section 120 described below, heat from the heat seal may be absorbed by the lid main body 70, which may result in poor bonding of the second sealing section 120. In addition, the time required for the process of forming the second sealing section 120 increases. Furthermore, if the volume of the lid main body 70 is large, the weight energy density of the electricity storage device 10 itself decreases. Therefore, from the viewpoint of suitably forming the second sealing section 120 and preventing a decrease in the weight energy density of the electricity storage device 10 itself, the thickness HA is preferably 7.0 mm or less, more preferably 4.0 mm or less, even more preferably 3.0 mm or less, and even more preferably 2.0 mm or less. The thickness HA is preferably in the range of 0.1 mm to 7.0 mm, 0.1 mm to 4.0 mm, 0.1 mm to 3.0 mm, or 0.1 mm to 2.0 mm. The portions constituting the lid body 70 may have different thicknesses. When the portions constituting the lid body 70 have different thicknesses, the thickness HA is the maximum thickness.

[0052] The covering body 90 shown in FIGS. 4, 5, and 6 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 any other method. 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 upper surface of the lid body 60. The first seal surface 91A is formed on the first flange 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 seal surface 91B is formed on the second flange portion 72B. The third seal surface 91C is formed on the third flange portion 72C. The second seal surface 91B and the third seal surface 91C extend in a second direction (UD direction in this embodiment) that intersects with the first direction in a front view of the lid body 60. In this embodiment, the first direction and the second direction are perpendicular to each other in a front view of the lid body 60. The first direction and the second direction do not have to be perpendicular to each other in a front view of the lid body 60. The fourth seal surface 91D forms the lower surface of the lid body 60. The fourth seal surface 91D extends in the first direction (LR direction in this embodiment) in a front view of the lid body 60. The fourth seal surface 91D is formed on the fourth flange portion 72D.

[0053] 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.

[0054] 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 resin material content is 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. In other words, the material constituting the covering 90 can contain materials other than the resin material in addition to the resin material.

[0055] 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, heat-sealable resins such as polyester and polyolefin are preferred, with polyolefin being more preferred. When the resin material is a resin, the covering 90 may be molded using any molding method.

[0056] 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 the main component, even more preferably a polyolefin as the main component, and even more preferably a polypropylene as the 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, in addition to saturated fatty acid amides, multiple types of amide-based lubricants that further contain unsaturated 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. Note that the "main component" refers to the component with the highest mass percentage among the materials contained in the constituent elements, for example, a material that accounts for 35 mass% or more, 50 mass% or more, 90 mass% or more, or 95 mass% or more.

[0057] Specific examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymer polyesters. Examples of copolymer polyesters include copolymer polyesters whose repeating units are primarily ethylene terephthalate. Specific examples include copolymer polyesters in which ethylene terephthalate is the main repeating unit and is polymerized with ethylene isophthalate (hereinafter abbreviated as polyethylene (terephthalate / isophthalate)), polyethylene (terephthalate / adipate), polyethylene (terephthalate / sodium sulfoisophthalate), polyethylene (terephthalate / sodium isophthalate), polyethylene (terephthalate / phenyl dicarboxylate), and polyethylene (terephthalate / decane dicarboxylate). Among these, polybutylene terephthalate is preferred as the resin material from the viewpoint of improving heat resistance and pressure resistance.

[0058] Specific examples of polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); propylene-α-olefin copolymers; and ethylene-butene-propylene terpolymers. When the polyolefin resin is a copolymer, it may be a block copolymer or a random copolymer. Among these, polypropylene is preferred as the resin material because of its excellent heat-sealing properties and electrolyte resistance.

[0059] The resin as the resin material may contain a filler as needed. Specific examples of fillers 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 to temperature changes can be improved.

[0060] 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 temperature for measuring the melt mass flow rate is 230°C.

[0061] The conjugate 80 (see FIG. 6 ) joins the lid body 70 and the covering body 90. Note that the conjugate 80 is not shown in FIGS. 4 and 5 for simplicity of the drawings. In this embodiment, the conjugate 80 joins at least a portion of the flange portion 72 of the lid body 70 to the covering body 90. In this embodiment, the conjugate 80 joins the entire surface 72X of the flange portion 72 to the covering body 90. When the lid body 70 does not have a flange portion 72, the conjugate 80 may join at least a portion of the base portion 71 of the lid body 70 to the covering body 90. Even when the lid body 70 has a flange portion 72, the conjugate 80 may join at least a portion of the base portion 71 of the lid body 70 to the covering body 90. When the joining body 80 joins at least a portion of the base 71 of the lid body 70 to the covering body 90, the joining body 80 may be joined to any location of the base 71, and the joining body 80 does not have to be joined to the flange portion 72.

[0062] The material constituting the bonded body 80 can be selected arbitrarily as long as it can bond the lid body 70 and the covering body 90. From the viewpoint of suitably bonding the lid body 70 and the covering body 90, the bonded body 80 is preferably composed of a resin material having a polar group. The resin material having a polar group is a resin material in which a polar group is introduced into a resin material that serves as a basic skeleton. Examples of the resin material that serves as a basic skeleton include polyolefins such as polyethylene and polypropylene, polycarbonate, polyamide, polyimide, polyacetal, polyphenylene sulfide, polyether ether ketone, polyvinyl chloride, ABS resin, tetrafluoroethylene resin, perfluoroalkoxyalkane, and vinylidene fluoride resin. From the viewpoint of suitably bonding the covering body 90 to the heat-sealable resin layer 53 of the exterior film 50, the resin material that serves as a basic skeleton preferably contains polyolefin as a main component. From the viewpoint of suitable bonding with the heat-sealable resin layer 53 of the exterior film 50 and from the viewpoint of heat resistance, the resin material forming the basic skeleton is preferably polybutylene terephthalate. Therefore, the material constituting the bonded body 80 is preferably a polyolefin, like the covering body 90, in that it is a material that can be bonded to the covering body 90, which is suitable for bonding with the heat-sealable resin layer 53 of the exterior film 50. Furthermore, from the viewpoint of heat resistance, the resin material forming the basic skeleton is preferably polybutylene terephthalate.

[0063] A method for introducing a polar group into a resin material that serves as a basic skeleton can be chlorinated. Another example of a method for introducing a polar group into a resin material that serves as a basic skeleton can be graft-modifying the resin material that serves as a basic skeleton with a monomer containing an acidic group (such as a carboxylic acid group, a sulfonic acid group, or a phosphoric acid group), graft-modifying the resin material that serves as a basic skeleton with a monomer containing an acidic anhydride group (such as a carboxylic acid anhydride group, a sulfonic acid anhydride group, or a phosphoric acid anhydride group), or graft-modifying the resin material with a (meth)acrylic monomer. When a resin material that serves as a basic skeleton is graft-modified with a monomer containing an acidic anhydride group, maleic anhydride is particularly suitable as the monomer containing an acidic anhydride group.

[0064] From the viewpoint of favorable bonding between the coating 90 and the bonded body 80, it is preferable that the basic skeleton of the resin material constituting the coating 90 and the basic skeleton of the resin material constituting the layer of the bonded body 80 that is bonded to the coating 90 have the same or a similar structure. For example, when polyolefin or acid-modified polyolefin is used as the resin material constituting the coating 90, it is preferable that the resin material constituting the bonded body 80 contains acid-modified polyolefin.

[0065] The specific configuration of the bonded body 80 is a coating or a film. The bonded body 80 may have a single-layer structure of a layer made of a resin material having a polar group (hereinafter referred to as a "polar group-containing layer"), or any layer may be laminated on the polar group-containing layer.

[0066] 8A to 8D are cross-sectional views showing examples of the layer structure of the bonded body 80. The examples of the layer structure of the bonded body 80 shown in Fig. 8A to 8D are applicable to the case where the bonded body 80 is a coating film and the case where the bonded body 80 is a film.

[0067] In the example shown in FIG. 8A, the conjugate 80 has a single layer structure of a polar group-containing layer 81.

[0068] In the example shown in FIG. 8B , the bonded body 80 has a polar group-containing layer 81 and a resin layer 82 laminated on the coating body 90 side of the polar group-containing layer 81. The resin layer 82 is a layer made of a resin material that does not have polar groups. From the viewpoint of more suitably bonding the bonded body 80 and the coating body 90, it is preferable that the basic skeleton of the resin material that makes up the resin layer 82 is the same as or has a similar structure to the basic skeleton of the resin material that makes up the coating body 90. For example, when the resin material that makes up the coating body 90 is a polyolefin such as polyethylene or polypropylene, it is preferable that the material that makes up the resin layer 82 contains a polyolefin such as polyethylene or polypropylene.

[0069] In the example shown in FIG. 8C , the bonded body 80 has two polar group-containing layers 81A and 81B and a core material 83 disposed between the two polar group-containing layers 81A and 81B. The polar group-containing layer 81A is bonded to the lid body 70. The polar group-containing layer 81B is bonded to the coating body 90. When the coating body 90 is formed from a resin material having polar groups, the basic skeleton of the resin material constituting the polar group-containing layer 81B preferably has the same or a similar structure as the basic skeleton of the resin material constituting the coating body 90, from the viewpoint of more suitably bonding the bonded body 80 and the coating body 90. The basic skeletons of the resin material constituting the polar group-containing layer 81A and the basic skeletons of the resin material constituting the polar group-containing layer 81B may be the same or different. The material constituting the core material 83 is any material. The material constituting the core material 83 preferably has a higher melting point than the polar group-containing layers 81A and 81B so that it can maintain its shape even when heat is applied. The material that constitutes the core material 83 preferably has water vapor barrier properties.

[0070] When the polar group-containing layers 81A and 81B are made of a polyolefin resin, a polyester resin is preferred for the core material 83. Specific examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymer polyester. The core material 83 may also be a fibrous sheet. Examples of fibrous sheets include nonwoven fabric, mesh, and woven fabric. The fibers forming the nonwoven fabric are not particularly limited, and examples include natural fibers such as cellulose, wool, silk, cotton, and hemp; glass fiber, carbon fiber, and rock fiber; and chemical fibers made from heat-resistant synthetic resins such as polyester, aromatic polyester resin (liquid crystal polymer), polyamide, polyimide, polymethylpentene, polyarylate, polyphenylene oxide, polysulfone, polyether ether ketone, and polyphenylene sulfide. Among these, polyarylate, which has high heat resistance and excellent electrolyte compatibility, is preferred.

[0071] In the example shown in FIG. 8D , the bonded body 80 includes a polar group-containing layer 81, a resin layer 84 laminated on the coating body 90 side of the polar group-containing layer 81, and a core material 83 disposed between the polar group-containing layer 81 and the resin layer 82.

[0072] The thickness of the joined body 80 is the thickness in the UD direction of the joined body 80, which is disposed between the first flange portion 72A and the covering body 90 and extends in the LR direction in Fig. 6. The thickness of the joined body 80 can be selected arbitrarily. It is preferable that the thickness in the UD direction of the joined body 80 is thinner than the thickness in the UD direction of the covering body 90.

[0073] When the joined body 80 is a coating film, the thickness of the joined body 80 in the UD direction is preferably 0.5 μm or more, and more preferably 1.0 μm or more. When the joined body 80 is a coating film, the thickness of the joined body 80 in the UD direction is preferably 20 μm or less. When the joined body 80 is a coating film, the preferred range of the thickness of the joined body 80 in the UD direction is 0.5 μm or more and 20 μm or less, or 1 μm or more and 20 μm or less.

[0074] When the bonded body 80 is a coating film, the bonded body 80 can be formed as a coating film on the lid body 70 by applying a solution or dispersion of a resin material having polar groups to the lid body 70 and drying it. Methods for applying the solution or dispersion of the resin material having polar groups to the lid body 70 include, for example, dip coating, dispenser, inkjet, spraying, and screen printing. When applying the solution or dispersion of the resin material having polar groups to the lid body 70 by dip coating or spraying, it is preferable that the solution or dispersion be applied while masking portions of the lid body 70 that require conductivity, such as the base 71. When portions of the lid body 70 that require conductivity, such as the base 71, are not masked, it is preferable that the coating film formed on the portions that require conductivity be removed.

[0075] When the joined body 80 is a film, the thickness in the UD direction of the joined body 80 is preferably 5 μm or more. When the joined body 80 is a film, the thickness in the UD direction of the joined body 80 is preferably 500 μm or less. When the joined body 80 is a film, the preferred range of the thickness in the UD direction of the joined body 80 is 5 μm or more and 500 μm or less.

[0076] The UD thickness of the assembly 80 is measured as follows. First, the lid 60 is removed from the power storage device 10. Next, the lid 60 is cut so that a surface perpendicular to the interface between the lid body 70 and the assembly 80 is exposed, and the surface perpendicular to the interface between the lid body 70 and the assembly 80 is polished using a polishing machine. Next, the polished cross section is imaged using a laser microscope (e.g., a combination of a controller VK-X3000 and a head VK-X3050, manufactured by KEYENCE Corporation) to obtain image data of the cross section of the test piece. Based on the obtained image data, the assembly 80 is identified, and its thickness is calculated using an image analysis program (e.g., a multi-file analysis application VK-X3050, manufactured by KEYENCE Corporation). The UD thickness of the assembly 80 may vary in different locations. The preferred UD thickness of the assembly 80 exemplified in the embodiments is the thickness at any location of the assembly 80.

[0077] When the lid body 60 is plate-shaped, it is preferable that the lid body 60 has 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 has a certain width in the FB direction so that the lid seal portion 91 of the lid body 60 and the exterior film 50 can be appropriately heat-sealed when forming the second sealing portion 120 described below. The minimum width 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 width 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 width of the lid seal portion 91 of the lid body 60 may be 20 mm or more. The preferred width ranges for 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 being plate-shaped, this does not include embodiments in which the lid body 60 is composed solely of a film specified by the JIS (Japanese Industrial Standards) "Packaging Terminology" standard. The width of the lid seal portion 91 of the lid body 60 may vary depending on the location. When the width of the lid seal portion 91 of the lid body 60 varies depending on the location, the width of the lid seal portion 91 of the lid body 60 is the width of the widest part.

[0078] In this embodiment, with the exterior film 50 wrapped around the electrode body 20, the facing surfaces (heat-fusible resin layers 53) of the exterior film 50 are heat-sealed to form the first sealing portion 110.

[0079] The first sealed portion 110 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 110 extends in the longitudinal direction of the exterior body 40. The position at which the first sealed portion 110 is formed in the exterior body 40 can be selected arbitrarily. In the present embodiment, the base 70X of the first sealed portion 110 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 110X of the first sealed portion 110 may be located on any surface of the exterior body 40. In the present embodiment, the first sealed portion 110 protrudes outward beyond the electrode assembly 20 in a plan view. The first sealed portion 110 may be folded, for example, toward the second surface 42 or the first surface 41 of the exterior body 40.

[0080] In this embodiment, the second sealing portion 120 (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 120. The seal strength of the second sealing portion 120 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 L-R (width) direction in FIG. 1A .

[0081] The seal strength of the second sealing portion 120 is measured as follows. First, a slit is made 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 (see the two-dot chain lines in FIG. 1B) aligned in the L-R direction. The width of the three strip-shaped members 41X, 41Y, and 41Z in the L-R 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 120. The length of the lid body 60 in the L-R 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. The distance between the zippers in the UD direction is 10 mm. The seal strength of the strip-shaped members 41X, 41Y, and 41Z is the peak value of each seal strength. In this embodiment, the seal strength of the second sealing portion 120 is the average value of the seal strengths of the strip-shaped members 41X, 41Y, and 41Z. When the length of the lid body 60 in the L-R direction is 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 using the same method as when the length of the lid body 60 in the L-R direction is 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 120 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 120 is the seal strength of the long sides of the lid seal portions 91 of the multiple parts.

[0082] From the viewpoint of suitably maintaining the state in which the electrode assembly 20 is sealed by the exterior housing 40, the seal strength of the second sealing unit 120 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 120 is 40 N / 15 mm or more, the state in which the electrode assembly 20 is sealed by the exterior housing 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 120 is 85 N / 15 mm or more, the state in which the electrode assembly 20 is sealed by the exterior housing 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 120 is preferably 300 N / 15 mm or less. A preferred range for the seal strength of the second sealing portion 120 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.

[0083] 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 covering body 90, or may be formed separately from the covering body 90 and joined to the covering body 90. In this embodiment, the protrusion 96 is formed integrally with the covering body 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 110X of the first sealing portion 110 and the lid body 60. In particular, when the base 110X of the first sealing portion 110 is located between the boundary 92 and boundary 95 of the lid body 60, the resin filling ability between the base 110X of the first sealing portion 110 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 base 110X of the first sealing portion 110 is located. In this embodiment, the base 110X of the first sealing portion 110 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 110 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 91A, the second seal surface 91B, the third seal surface 91C, the fourth seal surface 91D, the boundary 93, the boundary 94, and the boundary 95.

[0084] 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.

[0085] The direction in which the protrusion 96 extends can be selected arbitrarily. In this embodiment, the protrusion 96 extends along a first direction (in this embodiment, the LR direction). The protrusion 96 may extend along a second direction (in this embodiment, the UD direction). The protrusion 96 may extend in a third direction that intersects with the first direction (in this embodiment, the LR direction) and the second direction (in this embodiment, the UD direction) when the lid 60 is viewed from the front.

[0086] 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 110. For example, the length of the protrusion 96 may be substantially equal to the length of the first sealing portion 110, or may be 30% to 50% of the length of the first sealing portion 110.

[0087] <1-2. Method for manufacturing electricity storage devices> FIG. 9 is a flowchart showing an example of a method for manufacturing the electricity storage device 10. The method for manufacturing the electricity storage device 10 includes, for example, a first step, a second step, a third step, a fourth step, a fifth step, and a sixth step. The first step to the sixth step are performed, for example, by a manufacturing apparatus for the electricity storage device 10. At least some of the first step to the sixth step may be performed by an operator. Note that the first step to the sixth step are names of the steps in the method for manufacturing the electricity storage device 10 specified for convenience, and do not necessarily refer to the order of the steps. The order of the first step to the sixth step can be changed as desired as long as it is not technically inconsistent.

[0088] In the first step of step S11, the manufacturing apparatus manufactures the lid body 60. The first step is a step of joining the lid body 70 and the covering body 90 via the connecting body 80. The lid body 60 can be manufactured, for example, by injection molding the covering body 90 onto the lid body 70 to which the connecting body 80 is connected. In another example, the lid body 60 may be manufactured by fitting the lid body 70 to which the connecting body 80 is connected into the molded covering body 90, and applying heat to the lid body 70 to fuse the lid body 70, the connecting body 80, and the covering body 90 together. In yet another example, the lid body 60 may be manufactured by fitting the molded covering body 90 and the lid body 70 to which the connecting body 80 is connected into a mold, and crimping them together while applying heat.

[0089] The second step of step S12 is carried out after the first step. In the second step, the manufacturing device places a pair of lid bodies 60 on the sides of the electrode body 20 in the FB direction.

[0090] The third step of step S13 is performed after the second step. In the second step, the manufacturing device joins the current collector 30 and the lid 60 together.

[0091] The fourth step of step S14 is performed after the third step. In the fourth 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 with a restricting means. The restricting means is, for example, a groove into which the electrode assembly 20 and the lid body 60 are fitted. The restricting means may be a device that applies an external force to the electrode assembly 20 and the lid body 60 to prevent the electrode assembly 20 and the lid body 60 from moving. The restricting means may be a device that applies a force to the electrode assembly 20 and the lid body 60 in a direction opposite to the direction in which the exterior film 50 is pulled. The restricting means may include a roller that runs 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 lid 60 are joined, the opening 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 at both ends in the FB direction, and the opening may be closed by the lid 60.

[0092] The fifth step of step S15 is performed after the fourth step. In the fifth step, the manufacturing device heat-seals the exterior film 50 and the lid 60 together to form the second sealed portion 120.

[0093] The sixth step of step S16 is performed before or after the fifth step. In the sixth step, the manufacturing apparatus forms the first sealing portion 110 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-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.

[0094] <1-3. Actions and Effects of Electricity Storage Devices> In the electricity storage device 10, the lid main body 70 containing a conductive material is covered with the covering body 90 containing a resin material, so that the covering body 90 and the exterior film 50 can be suitably joined together. Furthermore, the lid main body 70 and the covering body 90 are joined together by the joining body 80, so that the lid main body 70 and the covering body 90 can be suitably joined together. Therefore, the electricity storage device 10 has high sealing performance.

[0095] [2. Modifications] The above-described embodiments are examples of possible forms of the electricity storage device, lid, method for manufacturing a 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, method for manufacturing a 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 of such forms include forms in which part of the configuration of the embodiments is replaced, modified, or omitted, or forms in which a new configuration is added to the embodiments. Some examples of modified forms of the embodiments are shown below. Note that the following modified forms can be combined with each other as long as there is no technical contradiction.

[0096] <2-1. First modified example> 10 is an enlarged view of a surface 72X of the lid body 60 included in the electricity storage device 10 of the first modified example. In the above embodiment, from the viewpoint of more suitably joining the joined body 80 and the lid main body 70, it is preferable that at least a part of the surface of the portion of the lid main body 70 that is joined to the joined body 80 is a roughened surface 72Y. In the first modified example, at least a part of the surface 72X of the flange portion 72 of the lid main body 70 may be a roughened surface 72Y. When the base 71 is covered with the covering body 90, at least a part of the surface of the base 71 may be a roughened surface 72Y. This allows the base 71 and the covering body 90 to be more firmly joined.

[0097] The rough surface 73 can be formed, for example, by roughening the surface 72X of the flange portion 72. Specific methods for roughening include, for example, shot blasting, polishing, alumite treatment, wet etching, plasma treatment, laser treatment, or roughening plating. To strengthen the bonding strength between the lid main body 70 and the bonded body 80, it is preferable that the entire surface 72X of the flange portion 72 of the lid main body 70 be roughened. In other words, it is preferable that the entire surface 72X of the flange portion 72 is a roughened surface 72Y. As shown in FIG. 10 , minute irregularities are formed on the roughened surface 72Y. When the bonded body 80 is bonded to the lid main body 70, the lid main body 70 and the bonded body 80 are more firmly bonded to each other due to the anchor effect. To obtain a higher anchoring effect, the maximum height roughness Rz of the rough surface 72Y is preferably in the range of 0.01 μm to 500 μm, and more preferably in the range of 0.5 μm to 200 μm. The maximum height roughness Rz of the rough surface 72Y is measured in accordance with JIS B 0601-2001. The maximum height roughness Rz of the rough surface 72Y is measured using a laser microscope VK-X3000 equipped with a white light interferometer manufactured by Keyence Corporation.

[0098] <2-2. Second modified example> FIG. 11 is an enlarged view of a surface 72X of the lid body 60 included in the electricity storage device 10 of the second modified example. In the above embodiment, from the viewpoint of more suitably joining the joined body 80 and the lid main body 70 and increasing the adhesion between the lid main body 70 and the joined body 80, it is preferable that at least a portion of the surface of the lid main body 70 that is joined to the joined body 80 has a surface treatment layer 72Z (see FIG. 11 ). The surface treatment layer 72Z refers to a thin film that is provided with corrosion resistance (e.g., acid resistance, alkali resistance, etc.) on the surface of the lid main body 70 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 by applying a coating agent on the surface of the lid main body 70. Examples of corrosion prevention treatment by applying a coating agent include applying a liquid such as a chromate treatment, a zirconium phosphate chemical conversion treatment, a resin-zirconium-based chemical conversion coating treatment, or a metal salt-zirconium-based chemical conversion treatment. Specifically, the surface treatment layer 72Z refers to a coating that improves the acid resistance of the lid body 70 (acid-resistant coating), a coating that improves the alkali resistance of the lid body 70 (alkali-resistant coating), or the like. The surface treatment layer 72Z may be formed by one type of treatment, or by a combination of two or more types. It may also be formed by a single layer or multiple layers. Among these treatments, hydrothermal conversion treatment and anodizing are treatments in which the surface of a metal foil is dissolved by a treatment agent to form a metal compound with excellent corrosion resistance. These treatments may also be included in the definition of chemical conversion treatment. Furthermore, when the surface treatment layer 72Z is ​​formed on the surface of the lid body 70, the surface treatment layer 72Z is ​​included in the lid body 70.

[0099] Preferably, at least a portion of the surface of the lid main body 70 that is to be joined with the joined body 80 exhibits a peak PCr in the range of 576 eV to 581 eV, which is derived from the Cr2p3 / 2 chromium compound, as determined by X-ray photoelectron spectroscopy. Such a characteristic can be obtained, for example, by forming a surface treatment layer 72Z on at least a portion of the surface of the lid main body 70 that is to be joined with the joined body 80. In this embodiment, the surface treatment layer 72Z is ​​formed on at least a portion of the surface 72X of the flange portion 72 of the lid main body 70. This further enhances the adhesion between the surface treatment layer 72Z formed on the surface 72X and the joined body 80.

[0100] The detection of the PCr peak confirms that a chromium compound is present in the composition used to form the surface treatment layer 72Z by chemical conversion treatment. Cr atoms play a central role in the coating, forming coordinate bonds with -COOH, -NH2, -CN, and other groups. Therefore, they form crosslinked structures with functional groups that have structures that can serve as other ligands, such as polycarboxylic acids and their ammonium salts, thereby providing durability, including corrosion resistance and chemical resistance.

[0101] The analysis of the surface treatment layer 72Z using X-ray photoelectron spectroscopy is specifically carried out using an X-ray photoelectron spectrometer under the following measurement conditions with reference to JIS K0162:2010.

[0102] Incident X-ray: Mg Kα (non-monochromatic X-ray, hν=1253.6eV) X-ray output: 10kV 20mA (200W) Photoelectron capture angle: 90 degrees (input lens positioned normal to the sample) Measurement area: 6mmφ Peak shift correction: Correction is performed so that the binding energy at which the peak intensity of the C1s peak becomes maximum is 285 eV.

[0103] When analyzing the peak position (binding energy) of the surface treatment layer 72Z using X-ray photoelectron spectroscopy, the bonded body 80 and the coating body 90 are physically peeled off without using water, an organic solvent, an aqueous solution of an acid or an alkali, or the like.

[0104] When the lid body 70 and the covering body 90 are peeled off, the bonding body 80 and the covering body 90 remaining on the surface 72X of the lid body 70 are removed by etching with Ar-GCIB. The surface treatment layer 72Z of the surface 72X of the lid body 70 obtained in this manner is analyzed using X-ray photoelectron spectroscopy.

[0105] The presence or absence of peak PCr can be easily confirmed as a detected peak displayed on the monitor screen of the X-ray photoelectron spectrometer if the peak PCr is clear. If the peak is small and unclear, it can be judged based on the area, half-width, and presence or absence of related peaks of the same atom.

[0106] Specifically, the judgment is made by the following procedures: (1) First, after subtracting the background and performing curve fitting by the Shirley method, if it can be determined from the peak area that the component is contained in an amount of 0.1% or more, the peak is judged to be present.

[0107] Furthermore, as a supplementary measure, the following criteria are used to determine whether the half-width of the peak that appears after fitting is greater than the energy resolution of the instrument, and whether, in addition to the main peak, peaks resulting from photoelectrons in outer shell orbitals beyond the main peak are also confirmed.X-ray photoelectron spectrometers usually come with analysis software, and we use "Vision Processing" from Kratos, the instrument manufacturer.

[0108] <2-3.Third modified example> In the above embodiment, the exterior film 50 of the electricity storage device 10 may protrude outward beyond at least one of the two lid bodies 60 in the FB direction. 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 eighth modification, when a convex portion is formed on the lid main body 70, the length of the convex portion is preferably long enough to be exposed from the portion of the exterior film 50 that protrudes outward beyond the lid body 60.

[0109] <2-4. Fourth 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 Gabeltop pouch or a brick pouch.

[0110] <2-5. Fifth 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. [Explanation of symbols]

[0111] 10: Energy storage device 20: Electrode body 30: Current collector 40: Exterior body 50: Exterior film 60: Lid 70: Lid body 72X: Surface 80 :zygote 90: Covering body

Claims

1. An electrode body; an exterior film that wraps the electrode body; a lid that seals the electrode body together with the exterior film, The lid body is a lid body including a conductive material; a cover including a resin material and covering the lid body; a joining body that joins the lid body and the cover body, Energy storage device.

2. The bonded body is configured to include a resin material having a polar group. The electricity storage device according to claim 1 .

3. The thickness of the bonded body is thinner than the thickness of the coating body. The electricity storage device according to claim 1 or 2.

4. The bonded body is a coating film. The electricity storage device according to claim 1 or 2.

5. The thickness of the bonded body is in the range of 0.5 μm to 20 μm. The electricity storage device according to claim 1 or 2.

6. The bonded body is a film. The electricity storage device according to claim 1 or 2.

7. The thickness of the bonded body is in the range of 5 μm to 500 μm. The electricity storage device according to claim 1 or 2.

8. The cover body further includes a surface treatment layer formed on at least a part of the surface to be joined with the joining body. The electricity storage device according to claim 1 or 2.

9. At least a portion of the surface of the lid body that is joined to the joining body is Analysis by X-ray photoelectron spectroscopy detects a peak originating from Cr2p3 / 2 of the chromium compound in the range of 576 eV to 581 eV. The electricity storage device according to claim 1 or 2.

10. At least a part of the surface of the lid body that is joined to the joining body is rough. The electricity storage device according to claim 1 or 2.

11. A lid body used as an exterior body of an electricity storage device, a lid body including a conductive material; a cover including a resin material and covering a portion of the lid body; a joining body that joins the lid body and the cover body, Lid body.

12. A method for manufacturing a lid body used as an exterior body of an electricity storage device, comprising: The lid body is a lid body including a conductive material; a cover including a resin material and covering the lid body; a joining body that joins the lid body and the cover body, The method for manufacturing the lid body includes: and joining the lid body and the cover body via the joining body. A method for manufacturing a lid body.

13. A method for manufacturing an electricity storage device, comprising: The electricity storage device is An electrode body; an exterior film that wraps the electrode body; a lid that seals the electrode body together with the exterior film, The lid body is a lid body including a conductive material; a cover including a resin material and covering a portion of the lid body; a joining body that joins the lid body and the cover body, The method for manufacturing the electricity storage device includes: and a step of placing the lid body on the electrode body. A method for manufacturing an electricity storage device.

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