Power storage device, electrode terminal unit, and exterior body set

Abstract

To provide a power storage device in which resistance to deformation of an electrode terminal with respect to a temperature change is improved.SOLUTION: A power storage device includes: an electrode body; an exterior body; and an electrode terminal. The exterior body seals the electrode body. The electrode terminal has one end part and the other end part arranged along a first direction. The one end part is connected to the electrode body, and the other end part is the electrode terminal protruding to an outside of the exterior body, and is made of a first material. The exterior body includes a fixing member that is fixed to the electrode terminal along a second direction intersecting the first direction between the one end part and the other end part of the electrode terminal and is made of a second material different from the first material. When assuming that a Vickers hardness of the first material is h(HV), a thickness of the electrode terminal along a direction orthogonal to the first direction and the second direction is T (mm), a linear expansion coefficient of the first material is α1, a linear expansion coefficient of the second material is α2, and the length of the electrode terminal fixed to the fixing member along the second direction is L0 (mm), (h×T)2×(α1 / α2)÷L0≥0.222 is satisfied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electricity storage device, an electrode terminal unit, and an exterior body set. [Background technology]

[0002] Patent Document 1 discloses an energy storage cell. The energy storage cell includes a battery element and an exterior body that houses the battery element. The exterior body has a cylindrical sheet member and a first resin member that is joined to the sheet member so as to close a first opening of the sheet member. The energy storage cell further includes a positive electrode tab and a negative electrode tab that are electrically connected to the battery element. The positive electrode tab and the negative electrode tab are led out of the exterior body through a sealing portion between the inner surface of the sheet member and the first resin member. The sealing portion is made of the same resin member as the first resin member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-040929 Summary of the Invention [Problem to be solved by the invention]

[0004] One test for evaluating the long-term reliability of an electricity storage device such as that described in Patent Document 1 is a thermal shock test (heat shock test). This test involves exposing a test specimen to an environment in which rapid temperature changes are repeated, and evaluating the test specimen's resistance to temperature changes. In such a thermal shock test, deformation may occur in the tabs fixed to the resin member, i.e., the electrode terminals. However, this is not taken into consideration in Patent Document 1.

[0005] An object of the present invention is to provide an electricity storage device in which the electrode terminals have improved resistance to deformation due to temperature changes. [Means for solving the problem]

[0006] An electricity storage device according to a first aspect of the present invention includes an electrode assembly, an exterior body, and an electrode terminal. The exterior body seals the electrode assembly. The electrode terminal has one end and another end arranged along a first direction, the one end being connected to the electrode assembly, and the other end being an electrode terminal that protrudes to the outside of the exterior body, and is made of a first material. The exterior body has a fixing member between the one end and the other end of the electrode terminal, the fixing member being made of a second material different from the first material and being fixed to the electrode terminal along a second direction intersecting with the first direction. When the Vickers hardness of the first material is h (HV), the thickness of the electrode terminal along a direction perpendicular to the first direction and the second direction is T (mm), the linear expansion coefficient of the first material is α1, the linear expansion coefficient of the second material is α2, and the length over which the electrode terminal is fixed to the fixing member along the second direction is L0 (mm), (h×T) 2 ×(α1 / α2)÷L0≧0.222 Meet the following.

[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 first material is a metal and the second material is a resin.

[0008] An electrode terminal unit for an electricity storage device according to a third aspect of the present invention comprises an electrode terminal and a fixing member. The electrode terminal has one end and the other end arranged along a first direction, the one end being configured to be connected to an electrode body of the electricity storage device, and is made of a first material. The fixing member is fixed to the electrode terminal between the one end and the other end of the electrode terminal along a second direction intersecting with the first direction, and is made of a second material different from the first material. Let h (HV) be the Vickers hardness of the first material, T (mm) be the thickness of the electrode terminal along a direction perpendicular to the first direction and the second direction, α1 be the linear expansion coefficient of the first material, α2 be the linear expansion coefficient of the second material, and L0 (mm) be the length over which the electrode terminal is fixed to the fixing member along the second direction. (h×T) 2 ×(α1 / α2)÷L0≧0.222 Meet the following.

[0009] An exterior body set for an electricity storage device according to a fourth aspect of the present invention comprises the electrode terminal unit for an electricity storage device according to the third aspect, and an exterior film joined to the electrode terminal unit. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an electricity storage device in which the electrode terminals have improved resistance to deformation due to temperature changes. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view schematically illustrating an electricity storage device according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing an example of a layer structure of the exterior member of FIG. [Figure 3] FIG. 2 is a perspective view schematically illustrating a configuration of a fixing member. [Figure 4] FIG. 2 is a perspective view schematically illustrating a configuration around an electrode terminal according to an embodiment. [Figure 5] FIG. 10 is a perspective view schematically illustrating a configuration around an electrode terminal according to another embodiment. [Figure 6] FIG. 2 is a cross-sectional view showing an example of a fixing member and a barrier film bonded thereto. [Figure 7] FIG. 1 is a cross-sectional view showing an example of a layer structure of a barrier film. [Figure 8] FIG. 2 is a cross-sectional view showing another example of the layer structure of the barrier film. [Figure 9] FIG. 10 is a cross-sectional view showing yet another example of the layer structure of the barrier film. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their description will not be repeated. In the present embodiment, a numerical range indicated by "to" means "greater than or equal to" or "less than or equal to." For example, the notation 2 to 15 mm means 2 mm or more and 15 mm or less. In the numerical ranges described in stages in this embodiment, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, separately described upper and lower limits, upper and lower limits, or lower and lower limits may each be combined to form a numerical range.

[0013] <1. Configuration of the power storage device> Fig. 1 is a perspective view schematically showing an electricity storage device 10 according to this embodiment. In Fig. 1, the direction of arrows UD indicates the thickness direction of the electricity storage device 10, and the direction of arrows LR indicates the width direction of the electricity storage device 10. Furthermore, the direction of arrows FB indicates the depth direction of the electricity storage device 10. The directions indicated by the arrows UDLRFB are the same in the subsequent figures.

[0014] Referring to FIG. 1 , the energy storage device 10 includes an electrode assembly 20, an electrode terminal 30, and an exterior housing 40. The electrode assembly 20 includes electrodes (positive and negative electrodes) constituting an energy storage member such as a lithium-ion battery, 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 polycation battery, or a 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.

[0015] The exterior body 40 seals the electrode body 20. The exterior body 40 includes an exterior film 50 and a pair of lid bodies 60. The exterior film 50 wraps the electrode body 20 so as to form a pair of openings 40A. In this embodiment, the exterior film 50 is wrapped around the electrode body 20 so as to form a pair of openings 40A. However, wrapping the electrode body 20 with the exterior film 50 is not limited to wrapping the exterior film 50, and the electrode body 20 may be placed inside the exterior film 50 that has been pre-formed into a cylindrical shape. The exterior film 50 has a protruding portion 50X that protrudes outward from the portion wrapping the electrode body 20 when the exterior film 50 wraps the electrode body 20. The pair of lid bodies 60 are respectively arranged on the sides of the electrode body 20 so as to close the pair of openings 40A. As will be described later, the pair of lid bodies 60 are an example of a fixing member of the present invention.

[0016] [Exterior film] FIG. 2 is a cross-sectional view showing the layer structure of the exterior film 50 included in the electricity storage device 10 of FIG. 1. The exterior film 50 is, for example, a laminate film having a base 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, and may be made of, for example, a resin film. The interior and exterior 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.

[0017] The substrate layer 51 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 may include, for example, at least one layer of a stretched polyester resin layer and a stretched polyamide resin layer. For example, the substrate layer 51 may include at least one layer of a stretched polyester resin layer and a stretched polyamide resin layer, thereby protecting the barrier layer 52 during processing of the exterior film 50 and preventing breakage of the exterior film 50. To increase 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. To achieve 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 include 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, more preferably 5 to 150 μm, from the viewpoint of film strength.

[0018] The barrier layer 52 is bonded to the base layer 51 via, for example, an adhesive layer 54. The barrier layer 52 included in the packaging film 50 is composed of, for example, a metal foil having barrier properties, from the viewpoints of processability (e.g., moisture resistance and ductility) and cost. Examples of metal foil include aluminum alloy, stainless steel, titanium steel, and steel plate. The aluminum alloy foil preferably contains iron from the viewpoints of packaging suitability and pinhole resistance when packaging the electrode body 20. The iron content in the aluminum alloy foil is preferably 0.5 to 5.0 mass%, more preferably 0.7 to 2.0 mass%. An iron content of 0.5 mass% or more provides the packaging suitability, pinhole resistance, and ductility of the packaging film 50. Furthermore, an iron content of 5.0 mass% or less provides the packaging film 50 with excellent flexibility. The barrier layer 52 may include a vapor deposition film and a resin layer in addition to the metal foil.

[0019] From the viewpoints of barrier properties, pinhole resistance, and packaging suitability, the thickness of the barrier layer 52 is preferably, for example, 5 to 200 μm, and more preferably 30 to 80 μm. When the thickness of the barrier layer 52 is 15 μm or more, the exterior film 50 is less likely to break even when stress is applied during packaging processing. When the thickness of the barrier layer 52 is 200 μm or less, an increase in the mass of the exterior film 50 can be reduced, and a decrease in the weight energy density of the electricity storage device 10 can be suppressed.

[0020] 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 using 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] When the buffer layer is made of rubber, the lower limit of the buffer layer thickness is 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 range of the buffer layer thickness is 0.5 mm to 10 mm, 0.5 mm to 5 mm, or 0.5 mm to 2 mm.

[0026] 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.

[0027] Here, 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 such a 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, leading to a decrease in battery performance. On the other hand, in this embodiment, the exterior body 40 seals the electrode assembly 20 by wrapping the exterior film 50 around the electrode assembly 20, so that the electrode assembly 20 can be easily sealed 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 to improve the volumetric energy density of the electricity storage device 10 and to improve cooling efficiency, 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 high pressure uniformly from the outer surface of the battery in order to exert battery performance, and therefore it is necessary to eliminate the space between the electrode body 20 and the exterior film 50. Therefore, it is preferable that the exterior film 50 is wrapped around the electrode body 20 so as to contact the outer surface of the electrode body 20.

[0028] 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 surfaces (heat-fusible resin layers 53) of the exterior film 50 facing each other in the protrusion portion 50X.

[0029] The protruding portion 50X includes a portion where a pair of opposing edges of the exterior film 50 shown in FIG. 2 are overlapped. The first sealing portion 70 extends in the longitudinal direction (FB direction) of the exterior body 40. The position where the first sealing portion 70 is formed in the exterior body 40 can be selected arbitrarily. In the present embodiment, the base 70X of the first sealing portion 70 is preferably located on the side 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 sealing portion 70 may be located on any surface of the exterior body 40. From the viewpoint of configuring the energy storage device 10 compactly, when the energy storage device 10 is in use, the protruding portion 50X is folded, for example, toward the first surface 41 or the second surface 42 of the exterior body 40. In the present embodiment, when the energy storage device 10 is in use, the protruding portion 50X is folded toward the second surface 42 of the exterior body 40.

[0030] In this embodiment, the heat-fusible resin layer 53 of the exterior film 50 and a lid seal portion 63 of the lid body 60, which will be described later, are heat-sealed to form the second sealing portion 80. In other words, the exterior film 50 is joined to the lid body 60.

[0031] [Fixed part] 3 is a perspective view of the lid body 60 according to this embodiment. The lid body 60 is, for example, in the shape of a substantially rectangular plate, and constitutes the exterior body 40 together with the exterior film 50. The lid body 60 is made of a second material. Here, "made of a second material" means that, when the entire material constituting the lid body 60 is taken as 100% by mass, the content of the second material is 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. In other words, the material constituting the lid body 60 can contain, in addition to the second material, materials other than the second material.

[0032] The second material according to this embodiment is a resin. 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 second material may be a mixture of these resins, a copolymer, or a modified version of the copolymer. Among these, the second material is preferably a heat-sealable resin such as polyester or polyolefin, and more preferably polyolefin. When the second material is a resin, the lid 60 may be molded using any molding method.

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

[0034] Specific examples of polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; polypropylenes such as homopolypropylene, polypropylene block copolymers (e.g., propylene and ethylene block copolymers), and polypropylene random copolymers (e.g., propylene and ethylene random copolymers); 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 second material because of its excellent heat-sealing properties and electrolyte resistance.

[0035] The resin as the second 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 second material, the deformation resistance of the lid 60 against temperature changes can be improved.

[0036] The lid body 60 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 to the first surface 61. The lid seal portion 63 is connected to 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 the width direction (LR direction) of the electricity storage device 10 when the lid body 60 is viewed from the front. 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 thickness direction (UD direction) of the electricity storage device 10 that intersects with the width direction when the lid body 60 is viewed from the front. In this embodiment, when the lid body 60 is viewed from the front, the width direction and the thickness direction of the electricity storage device 10 are perpendicular to each other. The fourth sealing surface 63D forms the lower surface of the lid body 60. When the lid body 60 is viewed from the front, the fourth sealing surface 63D extends in the width direction (LR direction).

[0037] The lid 60 according to this embodiment has a through-hole 60X that penetrates the first surface 61 and the second surface 62. In this embodiment, the through-hole 60X has a rectangular shape when viewed from the front of the lid 60. When the electrode assembly 20 is housed in the lid 60, the electrode terminal 30 penetrates the through-hole 60X so as to protrude to the outside of the exterior body 40. In this embodiment, the inner wall surface of the through-hole 60X and the outer circumferential surface of the electrode terminal 30 facing the inner wall surface are adhesively fixed to each other via an adhesive film 31, which will be described later. As a result, the lid 60 is fixed to the electrode terminal 30 along the second direction between one end 300 and the other end 301 of the electrode terminal 30, as will be described later. Hereinafter, the lid 60 to which the electrode terminal 30 is fixed, as shown in FIG. 4, may be referred to as an electrode terminal unit 600.

[0038] When the lid body 60 is plate-shaped, it is preferable that the lid body 60 has a certain degree of thickness so that deformation of the exterior body 40 is suppressed even when the electricity 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 63 of the lid body 60 has a certain degree of thickness so that the lid seal portion 63 of the lid body 60 and the exterior film 50 can be suitably heat-sealed when forming the second sealing portion 80. 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 12 mm. The 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 12 mm, 3.0 mm to 20 mm, 3.0 mm to 15 mm, 3.0 mm to 12 mm, 4.0 mm to 20 mm, 4.0 mm to 15 mm, and 4.0 mm to 12 mm. In this embodiment, when the lid body 60 is described as being plate-shaped, films defined by the JIS (Japanese Industrial Standards) "Packaging Terminology" standard are not included as materials constituting the lid body 60. 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.

[0039] A barrier film 90 may be bonded to the lid 60 to prevent at least one of moisture and gas from penetrating into the exterior body 40 from between the lid 60 and the exterior film 50. The barrier film 90 may cover at least a portion of the lid seal portion 63 of the lid 60. In this embodiment, the barrier film 90 covers the entire lid seal portion 63, the second surface 62, and the inside of the through-hole 60X of the lid 60. The barrier film 90 may also cover the boundaries 64 to 67. Because the barrier film 90 covers the lid seal portion 63 and the boundaries 64 to 67, as well as the second surface 62 and the inside of the through-hole 60X, moisture is prevented from penetrating into the interior of the exterior body 40 from between the electrode terminal 30 and the through-hole 60X. The barrier film 90 may be formed from a single film. For example, the portion covering the lid seal portion 63 and the portion covering the second surface 62 may be formed as separate pieces. In other words, the barrier film 90 may be a film divided into a plurality of parts.

[0040] 6 is a cross-sectional view showing an example of a lid 60 and a barrier film 90 bonded thereto. The position of an end 90A of the portion of the barrier film 90 covering the lid seal portion 63 and the position of an end 90B of the portion covering the inside of the through-hole 60X of the lid 60 can be selected arbitrarily. When the electricity storage device 10 is a battery containing an electrolyte solution such as a lithium ion battery, the ends 90A and 90B of the barrier film 90 may come into contact with gas such as hydrogen fluoride generated from the electrolyte solution, which may corrode a barrier layer 91 provided in the barrier film 90, which will be described later.

[0041] For this reason, from the viewpoint of suppressing corrosion of the barrier layer 91, it is preferable that the end 90A be located closer to the second surface 62 than to the boundary between the lid seal portion 63 and the first surface 61. From the same viewpoint, it is preferable that the end 90B be located closer to the opening of the through-hole 60X on the second surface 62 side than to the opening of the through-hole 60X on the first surface 61 side. Note that the end 90A may be located at the boundary between the lid seal portion 63 and the first surface 61, or may extend to a position closer to the electrode body 20 than to the lid body 60. The end 90B may be located near the opening of the through-hole 60X on the first surface 61 side, or may extend to a position closer to the electrode body 20 than to the lid body 60.

[0042] 7 to 9 are cross-sectional views showing examples of the layer structure of a barrier film 90. As shown in FIG. 7, the barrier film 90 only needs to include at least a barrier layer 91. The specifications of the barrier layer 91 are the same as the specifications of the barrier layer 52 of the exterior film 50. The barrier layer 91 may be thinner than the barrier layer 52 of the exterior film 50. When the barrier film 90 is a single layer consisting of only the barrier layer 91, one surface of the barrier layer 91 is bonded to the lid 60 with an adhesive or the like. When the barrier film 90 is a single layer consisting of only the barrier layer 91, the other surface of the barrier layer 91 is bonded to the heat-sealable resin layer 53 of the exterior film 50 with an adhesive or the like.

[0043] As shown in FIG. 8 , the barrier film 90 may include an outer layer 92 laminated on the surface of the barrier layer 91 opposite to the surface bonded to the lid 60. The outer layer 92 serves as, for example, a base layer or a heat-sealable resin layer. As a base layer, it protects the barrier layer 91. As a heat-sealable resin layer, it is heat-sealed to the heat-sealable resin layer 53 of the exterior film 50. When the outer layer 92 serves as a base layer, the specifications of the outer layer 92 as a base layer are the same as the specifications of the base layer 51 of the exterior film 50. When the outer layer 92 serves as a heat-sealable resin layer, the specifications of the outer layer 92 as a heat-sealable resin layer are the same as the specifications of the heat-sealable resin layer 53 of the exterior film 50. When the outer layer 92 serves as a heat-sealable resin layer, it may be thinner than the heat-sealable resin layer 53. When the outer layer 92 serves as a heat-sealable resin layer, the thickness of the outer layer 92 may be, for example, 5 to 20 μm. When the outer layer 92 is a base layer, the barrier layer 91 is protected. When the outer layer 92 is a base layer, the outer layer 92 and the heat-sealable resin layer 53 are bonded together, for example, with an adhesive or the like. When the outer layer 92 is a heat-sealable resin layer, the outer layer 92 and the heat-sealable resin layer 53 can be suitably bonded together by heat fusion. The barrier layer 91 and the outer layer 92 may be bonded together with an adhesive layer 54.

[0044] As shown in FIG. 9 , the barrier film 90 may include a heat-sealable resin layer 93 laminated on the surface of the barrier layer 91 that is to be bonded to the lid 60. The specifications of the heat-sealable resin layer 93 are the same as those of the heat-sealable resin layer 53 of the exterior film 50. The heat-sealable resin layer 93 may be thinner than the heat-sealable resin layer 53. The thickness of the heat-sealable resin layer 93 may be, for example, 5 to 20 μm. When the barrier film 90 includes the heat-sealable resin layer 93, the barrier film 90 and the lid 60 can be suitably bonded together by heat fusion. The barrier layer 91 and the heat-sealable resin layer 93 may be bonded together by an adhesive layer 55.

[0045] When the barrier film 90 is bonded to the lid 60, the material constituting the lid 60 does not include the material constituting the barrier film 90.

[0046] [Electrode terminal] FIG. 4 is a perspective view showing the configuration near the electrode terminal 30. The electrode terminal 30 is a conductive member electrically connected to the electrode body 20 (positive electrode or negative electrode), and is a terminal used for inputting and outputting power to and from the electrode body 20. The electrode terminal 30 according to this embodiment is formed, for example, in the shape of a plate having a certain thickness. Hereinafter, the thickness of the electrode terminal 30 is represented as T (mm). The thickness T is the average value of thickness values ​​measured at three locations arbitrarily selected from the portion of the electrode terminal 30 that is fixed to the lid body 60. In this embodiment, the thickness direction of the electrode terminal 30 coincides with the thickness direction (UD direction) of the electricity storage device 10.

[0047] The electrode terminal 30 has one end 300 and the other end 301 arranged along a first direction. In this embodiment, the first direction coincides with the depth direction (FB direction) of the electricity storage device 10. The one end 300 of the electrode terminal 30 is connected to the electrode body 20. The other end 301 of the electrode terminal 30 protrudes outside the exterior body 40.

[0048] The electrode terminal 30 is made of a first material. Here, "made of a first material" means that, when the entire material constituting the electrode terminal 30 is taken as 100% by mass, the content of the first 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. For example, if the electrode terminal 30 is made of a metal containing an alloy, the metal is the first material. Also, for example, if the electrode terminal 30 is made of a main body made of a metal containing an alloy and has a plating layer made of a metal containing an alloy and laminated on the outer surface of the main body, the metal constituting the main body is the first material.

[0049] The first material according to this embodiment is a metal. Examples of metals include aluminum, nickel, copper, and alloys thereof. For example, when the electrode body 20 is a lithium-ion battery, the first material of the electrode terminal 30 connected to the positive electrode is typically aluminum or an aluminum alloy. On the other hand, the first material of the electrode terminal 30 connected to the negative electrode is typically copper, nickel, or a copper alloy. In this case, for example, the electrode terminal 30 may be formed by plating a body made of copper, which is the first material, with nickel.

[0050] The surface of the electrode terminal 30 is preferably subjected to a chemical conversion treatment in order to enhance electrolyte resistance. For example, when the electrode terminal 30 is made of aluminum, specific examples of the chemical conversion treatment include known methods for forming a corrosion-resistant coating using phosphates, chromates, fluorides, triazine thiol compounds, etc. Among the methods for forming a corrosion-resistant coating, a preferred method is phosphate chromate treatment, which uses a three-component solution consisting of phenolic resin, a chromium (III) fluoride compound, and phosphoric acid.

[0051] An adhesive film 31 is bonded to the outer peripheral surface of the electrode terminal 30 according to this embodiment. The adhesive film 31 can be any film capable of bonding the electrode terminal 30, which is made of a metal as the first material, and the lid 60, which is made of a resin as the second material. The adhesive film 31 can be, for example, 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 at least the entire outer peripheral surface of the electrode terminal 30, the portion facing the inner wall surface of the through-hole 60X.

[0052] Here, the direction in which the lid body 60 intersects with the electrode terminal 30 when viewed from the thickness direction of the electricity storage device 10 is referred to as the second direction. The second direction intersects with the first direction in the same plane as the first direction, but is perpendicular to the thickness direction of the electrode terminal 30. The electrode terminal 30 is fixed to the lid body 60 along the second direction by the above-described adhesive film 31. In this embodiment, the second direction is perpendicular to the first direction and coincides with the width direction of the electrode terminal 30 and the width direction (LR direction) of the electricity storage device 10. The length by which the electrode terminal 30 is fixed to the lid body 60 (more precisely, the inner wall surface of the through hole 60X) along the second direction is defined as L0 (mm). In this embodiment, because the front and back surfaces of the electrode terminal 30 are fixed to the inner wall surface of the through hole 60X, the length L0 is equal to (L1 × 2), where L1 is the length of the electrode terminal 30 along the second direction. The length L1 is the average of the lengths measured along the second direction at three locations arbitrarily selected from the portion of the electrode terminal 30 that is fixed to the lid 60.

[0053] [Deformation Strength] The thermal shock test is a test for evaluating the deformation resistance of the electricity storage device 10 against temperature changes. The thermal shock test can be performed, for example, using a test device that repeatedly moves a sample cage containing the electricity storage device 10 between a low-temperature chamber and a high-temperature chamber, thereby subjecting the electricity storage device 10 to a sudden temperature change. The temperature of the low-temperature chamber is maintained at, for example, −40° C., −30° C., or −20° C., and the temperature of the high-temperature chamber is maintained at, for example, 60° C., 70° C., or 80° C. The number of cycles of movement of the sample cage containing the electricity storage device 10 is, for example, 100 to 1500 times.

[0054] As a result of intensive investigation, the inventors have found that the degree of deformation of the electrode terminal 30 in a thermal shock test depends on the Vickers hardness h (HV) of the first material, the thickness T (mm), the length L0 (mm) of the electrode terminal 30, and the linear expansion coefficient α1 (10 -6 / ℃) and the linear expansion coefficient α2(10 -6 / °C) contributes to the deformation resistance of the electrode terminal 30 in a thermal shock test. 2 ) is defined as follows: P = (h × T) 2 ×(α1 / α2)÷L0 (1)

[0055] The ease of deformation of the electrode terminal 30 is attributed to the structure and properties of the electrode terminal 30 itself, such as the thickness T of the electrode terminal 30 and the Vickers hardness h of the first material. It is believed that the greater the thickness T or the greater the Vickers hardness h of the first material, the more suppressed the deformation. In addition, the mechanism for fastening the electrode terminal 30 to the lid 60 and the relative physical property differences between them are also considered to contribute to the ease of deformation of the electrode terminal 30. Specifically, the shorter the length over which the electrode terminal 30 is fixed to the inner wall surface of the through-hole 60X in the second direction, the less susceptible the electrode terminal 30 is to dimensional changes in the lid 60 due to temperature changes, and the more suppressed the deformation. Furthermore, the smaller the difference in the rate of dimensional change due to temperature changes between the electrode terminal 30 and the lid 60, the less susceptible the electrode terminal 30 is to dimensional changes in the lid 60 due to temperature changes, and the more suppressed the deformation. The difference in the rate of dimensional change due to temperature changes between the electrode terminal 30 and the lid 60 can be specifically expressed as the ratio (α1 / α2) of the linear expansion coefficient α1 of the first material to the linear expansion coefficient α2 of the second material.

[0056] The inventors have confirmed through experiments that when the deformation resistance P calculated according to the above formula is less than 0.222, visible deformation occurs in the electrode terminal 30 after 100 cycles of temperature changes from -40 to 70°C. The deformation of the electrode terminal 30 was particularly noticeable in the portion from the periphery of the through-hole 60X, which is the fixing portion between the electrode terminal 30 and the lid 60, to the other end 301. On the other hand, the inventors have confirmed that when the deformation resistance P is 0.222 or more, no visible deformation occurs in the electrode terminal 30 even after the same cycles are performed.

[0057] The Vickers hardness (h) is measured by pressing a square pyramidal diamond indenter into the test surface of a sample of the first material at a test temperature of 23°C under a predetermined test force (F (N)). After the test load is released, the average length (d (mm)) of a pair of diagonals of the indentation remaining on the sample surface is calculated. The test surface of the sample corresponds to the UD surface of the electrode terminal 30. The test force (F) during Vickers hardness (h) measurement is 1.961 N, the diamond indenter pressing speed is 0.1 mm / s, the time to reach the test force (F) is 4 seconds, and the test force is held for 12 seconds. Other measurement conditions are as specified in JIS Z2244-1:2020. For existing energy storage devices, a sample of the first material can be obtained by removing the plating from the electrode terminal.

[0058] The linear expansion coefficient for metals is measured by an indentation test using a dilatometric thermomechanical analyzer specified in JIS Z 2285:2003, using a single metal sample. The metal sample is a cube measuring 1 mm in length, 1 mm in width, and 1 mm in thickness. The length direction corresponds to the FB direction of the electrode terminal 30, the width direction corresponds to the LR direction of the electrode terminal 30, and the thickness direction corresponds to the UD direction of the electrode terminal 30. The longitudinal ends of the metal sample have a parallelism tolerance of 25 μm as specified in JIS B 0621. The indentation load for the dilatometric thermomechanical analyzer is 10 g, the measurement temperature range is 20°C to 300°C, and the temperature rise rate is 5°C / min. The reference material is quartz glass with the same shape and dimensions as the sample and the recommended thermal and linear expansion coefficients. The linear expansion coefficient of a resin is measured by an indentation test using a thermomechanical analyzer (TMA) according to the method specified in JIS K 7197:2012. The resin test piece is a cube measuring 1 mm in length, 1 mm in width, and 1 mm in thickness, with the length direction aligned with the front-to-back direction of the lid 60, the width direction aligned with the left-to-right direction of the lid 60, and the thickness direction aligned with the universal direction of the lid 60. The parallelism of both ends of the resin test piece in the length direction is ±25 μm. The indentation load for the thermomechanical analyzer is 10 g, the measurement temperature range is 20°C to 120°C, and the temperature rise rate is 5°C / min.

[0059] If a metal sample 1 mm thick in the UD direction cannot be obtained from the electrode terminal of an existing power storage device, the measurement method for the linear expansion coefficient of the first material may be changed. Specifically, the metal sample obtained from the electrode terminal may have a size of 15 mm in length (FB direction of the electrode terminal) × 3 mm in width (LR direction of the electrode terminal) × the available thickness (UD direction of the electrode terminal). In this case, the linear expansion coefficient of the first material is the ratio of the change in length of the metal sample to the temperature measured by stretching the metal sample in the longitudinal direction using the thermomechanical analyzer. The measurement temperature range for this measurement is 20°C to 300°C, and the temperature rise rate is 5°C / min. The tensile load for the tensile test using the thermomechanical analyzer is 4 g. If the linear expansion coefficient of the first material is measured using this method or if a test piece of the resin cannot be obtained from the lid of an existing power storage device, the measurement method for the linear expansion coefficient of the second material may be changed. Specifically, the resin test piece obtained from the lid can be sized to have a length of 15 mm (in the FB direction of the lid) × width of 3 mm (in the LR direction of the lid) × thickness that can be extracted (in the UD direction of the lid). In this case, the linear expansion coefficient of the second material is the ratio of the change in length of the test piece to the temperature, measured by pulling the resin test piece in the longitudinal direction using the thermomechanical analyzer. The temperature range for this measurement is 20°C to 120°C, and the temperature rise rate is 5°C / min. The tensile load for the tensile test using the thermomechanical analyzer is 4 g.

[0060] <2. Modifications> Although several embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the present invention. For example, the following modifications are possible. Furthermore, the gist of the following modifications can be combined as appropriate.

[0061] (1) In the above embodiment, the electrode terminal 30 is fixed to the lid 60 so as to pass through the through-hole 60X of the lid 60. However, as shown in FIG. 5 , it is also possible to fix the electrode terminal 30 between the first sealing surface 63A or the fourth sealing surface 63D and the heat-sealable resin layer 53 of the exterior film 50 without forming the through-hole 60X in the lid 60. In this case, the deformation resistance P can be calculated by applying the above formula (1). In this case, the length L0 (mm) of the electrode terminal 30 fixed to the lid 60 along the second direction is equal to the length L1 (mm) of the electrode terminal 30 along the second direction. Hereinafter, the lid 60 with the electrode terminal 30 fixed thereto as shown in FIG. 5 may be referred to as an electrode terminal unit 601.

[0062] (2) In the above embodiment, the exterior body 40 includes an exterior film 50 and a pair of lid bodies 60. However, the configuration of the exterior body 40 is not limited to that of the above embodiment. For example, the exterior film 50 does not have to be wrapped around the outer surface of the electrode body 20 so as to be in contact with it. Furthermore, the location where the protruding portion 50X is formed is not limited to that of the above embodiment, and the protruding portion 50X itself may be omitted. Furthermore, instead of the exterior film 50, the electrode body may be sealed using a plurality of plate-shaped members made of the same material as that of the lid body 60.

[0063] (3) The second material is not limited to the resin exemplified in the above embodiment, but may be, for example, a metal oxide, a carbon fiber reinforced plastic, or a rubber material, or may be a combination of two or more of these materials, or a combination of at least one of these materials with a resin.

[0064] (4) The electrode body 20 may be fixed to the lid body 60 without using the adhesive film 31. The electrode body 20 and the lid body 60 may be fixed, for example, by a heat-sealing resin that fills the gap between them or by an adhesive.

[0065] (5) The exterior film 50 of the electricity storage device 10 may protrude outward beyond the lid body 60 in the depth direction (FB direction). The portion of the exterior film 50 protruding beyond the lid body 60 may be folded like a Gabeltop pouch or a brick pouch.

[0066] (6) The shape of the lid 60 is not limited to a substantially rectangular shape, but may be, for example, a substantially circular shape, a substantially elliptical shape, or a substantially polygonal shape.

[0067] <3. Additional Notes> The present invention further includes the following embodiments.

[0068] (1) The present invention can be embodied not only as an electricity storage device 10, but also as electrode terminal units 600, 601 for an electricity storage device that at least partially constitute an exterior body 40 that seals the electrode body 20 of the electricity storage device 10. The electrode terminal units 600, 601 include an electrode terminal 30 and a fixing member (lid body 60). The electrode terminal 30 has one end 300 and the other end 301 that are arranged along a first direction, and is configured so that the one end 300 is connected to the electrode body 20 of the electricity storage device 10. The fixing member is fixed to the electrode terminal 30 between the one end 300 and the other end 301 of the electrode terminal 30 along a second direction that intersects with the first direction, and is made of a second material different from the first material. Let h (HV) be the Vickers hardness of the first material, T (mm) be the thickness of the electrode terminal 30 in the direction perpendicular to the first direction and the second direction, α1 be the linear expansion coefficient of the first material, α2 be the linear expansion coefficient of the second material, and L0 (mm) be the length by which the electrode terminal is fixed to the fixing member in the second direction. Then, (h×T) 2 × (α1 / α2) ÷ L0 ≥ 0.222.

[0069] The electrode terminal units 600 and 601 may each have an adhesive film 31 and a barrier film 90.

[0070] (2) The present invention can be embodied as an exterior body set for an electricity storage device that at least partially constitutes the exterior body 40 that seals the electrode body 20 of the electricity storage device 10. The exterior body set includes the electrode terminal unit 600 or 601 for the electricity storage device described in (1) and an exterior film 50 that is joined to the electrode terminal unit 600 or 601. [Example]

[0071] Examples of the present invention will be described in detail below, but the present invention is not limited to the following examples.

[0072] <Experiment> A resin lid and a metal electrode terminal were fabricated and fixed together using an adhesive resin to produce samples of exterior bodies according to Examples 1 to 5 and Comparative Examples 1 and 2. The lid and electrode terminal were formed to have a rectangular plate-like outer shape in each sample. In each sample, the electrode terminal had one end and the other end along a first direction, and was fixed to the lid between the one end and the other end along a second direction perpendicular to the first direction. More specifically, the electrode terminal was fixed to the lid so that the first direction was parallel to the thickness direction of the lid and the second direction was parallel to the width direction of the lid. The lid and electrode terminal were fixed in two different ways: Mode 1, in which both sides of the electrode terminal were fixed so that the electrode terminal passed through a through-hole formed in the lid, as shown in FIG. 4; and Mode 2, in which one side of the electrode terminal was fixed to the sealing surface of the lid, as shown in FIG. 5. A common adhesive film was used to fix the lid and electrode terminal in each sample. The first material constituting the electrode terminal for each sample, the Vickers hardness h (HV) of the first material, the thickness T (mm) of the electrode terminal, the length L1 (mm) of the electrode terminal along the second direction, the length L0 (mm) of the electrode terminal fixed along the second direction, the fixing manner of the electrode terminal, the second material constituting the lid, the linear expansion coefficient α1 (10 -6 / ℃), the linear expansion coefficient of the second material α2(10 -6 / ℃), and the calculated deformation strength P (mm × HV 2) are as shown in Table 1 below. The Vickers hardness h, linear expansion coefficient α1, and linear expansion coefficient α2 were measured by the methods described above. For reference, Table 1 also shows the alloy symbols and quality symbols of the metals used as materials for forming the electrode terminals. [Table 1]

[0073] <Experimental Results> For each sample according to Examples 1 to 5 and Comparative Examples 1 and 2, it was visually confirmed that there was no deformation in the electrode terminals before the thermal shock test. Next, each sample was placed in a sample basket of a thermal shock tester, and the sample was repeatedly moved alternately between a low-temperature chamber maintained at -40°C and a high-temperature chamber maintained at 70°C for 100 cycles (one round trip is one cycle). Thereafter, each sample was removed from the thermal shock tester, and the electrode terminals were visually inspected for deformation. The results are shown in Table 2 below. The thermal shock tester used was a small thermal shock tester (TSE-12-A, manufactured by Espec Corporation), but the device used in the thermal shock test is not limited to this. [Table 2]

[0074] From the above results, it was confirmed that when the electricity storage device satisfies the deformation resistance P≧0.222, deformation of the electrode terminals due to temperature changes can be suppressed. [Explanation of symbols]

[0075] 10. Energy storage devices 20 Electrode body 30 electrode terminal 31 Adhesive film 40 Exterior body 50 exterior film 60 Lid (fixing member) 300 One end 301 Other end h Vickers hardness T Thickness L0: Fixing length between the lid and the electrode terminal α1, α2 linear expansion coefficient

Claims

1. An electrode body; an exterior body that seals the electrode body; an electrode terminal having one end and the other end arranged along a first direction, the one end being connected to the electrode body and the other end being protruding to the outside of the exterior body, the electrode terminal being made of a first material; Equipped with the exterior body has a fixing member between the one end and the other end of the electrode terminal, the fixing member being fixed to the electrode terminal along a second direction intersecting with the first direction, the fixing member being made of a second material different from the first material; Let h (HV) be the Vickers hardness of the first material, T (mm) be the thickness of the electrode terminal along a direction perpendicular to the first direction and the second direction, α1 be the linear expansion coefficient of the first material, α2 be the linear expansion coefficient of the second material, and L0 (mm) be the length by which the electrode terminal is fixed to the fixing member along the second direction. (h×T) 2 ×(α1 / α2)÷L0≧0.2222 fulfill, Energy storage device.

2. The first material is a metal and the second material is a resin. The electricity storage device according to claim 1 .

3. an electrode terminal having one end and the other end arranged along a first direction, the one end configured to be connected to an electrode body of an electricity storage device, and made of a first material; a fixing member that is fixed to the electrode terminal along a second direction intersecting with the first direction between the one end and the other end of the electrode terminal, the fixing member being made of a second material different from the first material; Equipped with Let h (HV) be the Vickers hardness of the first material, T (mm) be the thickness of the electrode terminal along a direction perpendicular to the first direction and the second direction, α1 be the linear expansion coefficient of the first material, α2 be the linear expansion coefficient of the second material, and L0 (mm) be the length by which the electrode terminal is fixed to the fixing member along the second direction. (h×T) 2 ×(α1 / α2)÷L0≧0.2222 fulfill, Electrode terminal unit for power storage devices.

4. The electrode terminal unit for an electricity storage device according to claim 3; an exterior film joined to the electrode terminal unit; Equipped with An exterior body set for an energy storage device.

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