Storage device, electrode terminal unit, and exterior body set

Abstract

A power storage device comprising 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 another end part arranged along a first direction, the one end part being connected to the electrode body, the other end part projecting to outside the exterior body, and the electrode terminal being composed of a first material. The exterior body has 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, the fixing member being composed of a second material that is different from the first material. The relationship (h×T)2×(α1 / α2)÷L0≥0.222 is satisfied, where h (HV) is the Vickers hardness of the first material, T (mm) is the thickness of the electrode terminal along a direction orthogonal to the first direction and the second direction, α1 is the linear expansion coefficient of the first material, α2 is the linear expansion coefficient of the second material, and L0 (mm) is the length of the electrode terminal fixed to the fixing member along the second direction.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a power storage cell. The power 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 joined to the sheet member so as to close a first opening of the sheet member. The power storage cell further includes a positive electrode tab and a negative electrode tab electrically connected to the battery element. The positive electrode tab and the negative electrode tab are led out to the outside 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 formed of the same resin member as the first resin member.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] One of the tests for evaluating the long-term reliability of a power storage device such as that of Patent Document 1 is a thermal shock test (heat shock test). In this test, a test article is exposed to an environment where rapid temperature changes are repeated, and the resistance of the test article to temperature changes is evaluated. In such a thermal shock test, deformation may occur in the tabs fixed to the resin member, that is, the electrode terminals. However, this is not considered in Patent Document 1.

[0005] An object of the present invention is to provide a power storage device with improved deformation resistance of electrode terminals against temperature changes.

Means for Solving the Problems

[0006] The power storage device according to the first aspect of the present invention includes an electrode body, an exterior body, and an electrode terminal. The exterior body seals the electrode body. The electrode terminal has one end portion and the other end portion arranged along a first direction, the one end portion is connected to the electrode body, the other end portion is an electrode terminal protruding outside the exterior body, and is made of a first material. The exterior body has a fixing member made of a second material different from the first material and fixed to the electrode terminal along a second direction intersecting the first direction between the one end portion and the other end portion of the electrode terminal. When the Vickers hardness of the first material is h (HV), the thickness of the electrode terminal along a direction orthogonal 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 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.

[0007] The power storage device according to the second aspect of the present invention is the power storage device according to the first aspect, wherein the first material is a metal and the second material is a resin.

[0008] The electrode terminal unit for a power storage device according to the third aspect of the present invention includes an electrode terminal and a fixing member. The electrode terminal has one end portion and the other end portion arranged along a first direction, the one end portion is configured to be connected to the electrode body of the power storage device, and is made of a first material. The fixing member is fixed to the electrode terminal along a second direction intersecting the first direction between the one end portion and the other end portion of the electrode terminal, and is made of a second material different from the first material. When the Vickers hardness of the first material is h (HV), the thickness of the electrode terminal along a direction orthogonal 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 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.

[0009] The exterior body set for a power storage device according to the fourth aspect of the present invention includes an electrode terminal unit for a power storage device according to the third aspect and an exterior film joined to the electrode terminal unit.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a power storage device with improved deformation resistance of the electrode terminal against temperature changes.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out 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 descriptions are not repeated. In this embodiment, the numerical range indicated by "~" means "or more" and "or less". For example, the notation of 2~15 mm means 2 mm or more and 15 mm or less. In the numerical ranges described step by step in this embodiment, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical range of other step-by-step descriptions. Further, the upper limit value and the upper limit value, the upper limit value and the lower limit value, or the lower limit value and the lower limit value described separately may be combined to form a numerical range, respectively.

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

[0014] Referring to FIG. 1, the power storage device 10 includes an electrode body 20, an electrode terminal 30, and an exterior body 40. The electrode body 20 includes, for example, electrodes (positive electrode and negative electrode) constituting a power storage member such as a lithium ion battery, a capacitor, an all-solid-state battery, a semi-solid-state battery, a quasi-solid-state battery, a polymer battery, an all-resin battery, a lead storage battery, a nickel-hydrogen storage battery, a nickel-cadmium storage battery, a nickel-iron storage battery, a nickel-zinc storage battery, a silver oxide-zinc storage battery, a metal-air battery, a polyvalent cation battery, or a capacitor, as well as a separator and the like. In this embodiment, the shape of the electrode body 20 is substantially a rectangular parallelepiped. Note that the "substantially rectangular parallelepiped" includes, in addition to a perfect rectangular parallelepiped, a solid that can be regarded as a rectangular parallelepiped by modifying the shape of a part of the outer surface, for example. The shape of the electrode body 20 may be, for example, a cylinder or a polygonal prism.

[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 such that a pair of openings 40A are formed. In the present embodiment, the exterior film 50 is wound around the electrode body 20 such that a pair of openings 40A are formed. However, wrapping the electrode body 20 with the exterior film 50 is not limited to winding the exterior film 50, and the electrode body 20 may be disposed inside the exterior film 50 that is formed in a cylindrical shape in advance. The exterior film 50 has an overhanging portion 50X that protrudes outward from the portion that wraps the electrode body 20 in a state of wrapping the electrode body 20. The pair of lid bodies 60 are respectively disposed on the sides of the electrode body 20 so as to close the pair of openings 40A. As will be described later, the pair of lid bodies 60 is an example of the fixing member of the present invention.

[0016] [Exterior film] FIG. 2 is a cross-sectional view showing the layer configuration of the exterior film 50 included in the power storage device 10 of FIG. 1. The exterior film 50 is, for example, a laminate (laminate film) having a base material layer 51, a barrier layer 52, and a heat-sealable resin layer 53 in this order. Note that all of these layers do not necessarily need to be included in the exterior film 50, and for example, the barrier layer 52 may not be included. That is, the exterior film 50 may be made of a material having flexibility and being easily bendable, and may be made of, for example, a resin film. The innermost layer and the outermost layer of the exterior film 50 may be the heat-sealable resin layer 53. In this case, the exterior film 50 may wrap the electrode body 20 and the lid body 60 by joining the outermost layer and the innermost layer.

[0017] The base material layer 51 is a layer that imparts heat resistance to the exterior film 50 and suppresses the occurrence of pinholes that may occur during processing or distribution. The base material layer 51 is composed of, for example, at least one of a stretched polyester resin layer and a stretched polyamide resin layer. For example, by including at least one of a stretched polyester resin layer and a stretched polyamide resin layer in the base material layer 51, the barrier layer 52 can be protected during processing of the exterior film 50, and breakage of the exterior film 50 can be suppressed. Also, 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. Note that the base material layer 51 may be composed of both a stretched polyester resin layer and a stretched polyamide resin layer. The thickness of the base material layer 51 is preferably, for example, 5 to 300 μm, and more preferably 5 to 150 μm, from the viewpoint of film strength.

[0018] The barrier layer 52 is joined to the base material layer 51 via, for example, an adhesive layer 54. The barrier layer 52 included in the exterior film 50 is composed of, for example, a metal foil having barrier properties, in terms of processability such as moisture resistance and ductility, and cost. Examples of the metal foil include aluminum alloy, stainless steel, titanium steel, or 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% by mass, and more preferably 0.7 to 2.0% by mass. When the iron content is 0.5% by mass or more, packaging suitability, excellent pinhole resistance, and ductility of the exterior film 50 can be obtained. Also, when the iron content is 5.0% by mass or less, excellent flexibility of the exterior film 50 can be obtained. The barrier layer 52 may include, in addition to the above metal foil, a vapor deposition film and a resin layer.

[0019] The thickness of the barrier layer 52 is preferably, for example, 5 to 200 μm, more preferably 30 to 80 μm, from the viewpoints of barrier properties, pinhole resistance, and packaging suitability. When the thickness of the barrier layer 52 is 15 μm or more, the outer packaging 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 outer packaging film 50 can be reduced, and a decrease in the weight energy density of the power storage device 10 can be suppressed.

[0020] Further, when the barrier layer 52 is an aluminum foil, it is preferable to provide a corrosion-resistant film on at least the surface opposite to the base material layer 51 in order to prevent dissolution and corrosion. The barrier layer 52 may be provided with corrosion-resistant films on both surfaces. Here, the corrosion-resistant film refers to, for example, a thin film that is formed on the surface of the barrier layer 52 by a hydrothermal transformation treatment such as a boehmite treatment, a chemical conversion treatment, an anodizing treatment, a plating treatment such as nickel or chromium, or a corrosion prevention treatment of applying a coating agent, and that imparts corrosion resistance (for example, acid resistance, alkali resistance, etc.) to the barrier layer 52. Specifically, the corrosion-resistant film means a film that improves the acid resistance of the barrier layer 52 (acid-resistant film), a film that improves the alkali resistance of the barrier layer 52 (alkali-resistant film), and the like. As the treatment for forming the corrosion-resistant film, one type may be performed, or two or more types may be combined. Further, not only a single layer but also a multilayer structure can be formed. Furthermore, among these treatments, the hydrothermal transformation treatment and the anodizing treatment are treatments that dissolve the surface of the metal foil with a treatment agent and form a metal compound having excellent corrosion resistance. Note that these treatments may be included in the definition of the chemical conversion treatment. Further, when the barrier layer 52 is provided with a corrosion-resistant film, the barrier layer 52 includes the corrosion-resistant film.

[0021] The corrosion-resistant film prevents delamination between the barrier layer 52 (e.g., aluminum alloy foil) and the base material layer 51 during the molding of the outer packaging film 50, and prevents dissolution and corrosion of the surface of the barrier layer 52 by hydrogen fluoride generated by the reaction of the electrolyte and moisture, particularly when the barrier layer 52 is an aluminum alloy foil, the aluminum oxide present on the surface of the barrier layer 52 is dissolved and corroded. In addition, it improves the adhesiveness (wettability) of the surface of the barrier layer 52, and shows the effect of preventing delamination between the base material layer 51 and the barrier layer 52 during heat sealing and preventing delamination between the base material layer 51 and the barrier layer 52 during molding.

[0022] The heat-sealable resin layer 53 is joined to the barrier layer 52 via, for example, an adhesive layer 55. The heat-sealable resin layer 53 contained in the outer packaging film 50 is a layer that imparts heat-sealing property to the outer packaging film 50. Examples of the heat-sealable resin layer 53 include polyester-based resins such as polyethylene terephthalate-based resins and polybutylene terephthalate-based resins, polyolefin-based resins such as polyethylene-based resins and polypropylene-based resins, or resin films made of acid-modified polyolefin-based resins obtained by graft-modifying these polyolefin-based resins with an acid such as maleic anhydride. From the viewpoints of sealing property 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 outer packaging film 50 preferably has one or more layers having a buffering 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 outside the base material layer 51, or the base material layer 51 may also serve as the buffer layer. When the outer packaging film 50 has a plurality of buffer layers, the plurality of buffer layers may be adjacent to each other, or may be laminated via the base material layer 51 or the barrier layer 52 or the like.

[0024] The material constituting the buffer layer can be arbitrarily selected from materials having cushioning properties. Materials having cushioning properties are, for example, rubber, non-woven fabric, or foamed sheet. Rubber is, for example, natural rubber, fluororubber, or silicone rubber. The rubber hardness is preferably about 20 to 90. The material constituting the non-woven fabric is preferably a material having excellent heat resistance. When the buffer layer is constituted by a non-woven fabric, the lower limit value of the thickness of the buffer layer is preferably 100 μm, more preferably 200 μm, still more preferably 1000 μm. When the buffer layer is constituted by a non-woven fabric, the upper limit value of the thickness of the buffer layer is preferably 5000 μm, more preferably 3000 μm. The preferable range of the thickness of the buffer layer is 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. Among these, the range of the thickness of the buffer layer is most preferably 1000 μm to 3000 μm.

[0025] When the buffer layer is constituted by rubber, the lower limit value of the thickness of the buffer layer is preferably 0.5 mm. When the buffer layer is constituted by rubber, the upper limit value of the thickness of the buffer layer is preferably 10 mm, more preferably 5 mm, still more preferably 2 mm. When the buffer layer is constituted by rubber, the preferable range of the thickness of the buffer layer is 0.5 mm to 10 mm, 0.5 mm to 5 mm, or 0.5 mm to 2 mm.

[0026] When the exterior film 50 has a buffer layer, since the buffer layer functions as a cushion, it is possible to suppress the exterior film 50 from being damaged by the impact when the power storage device 10 falls or by the handling during the manufacture of the power storage device 10.

[0027] Here, for example, there is a method of forming a housing portion (depression) for housing the electrode body 20 in the exterior film 50 through cold forming. However, it is not always easy to form a deep housing portion by such a method. If an attempt is made to deeply form the housing portion (depression) (for example, a forming depth of 15 mm) by cold forming, pinholes or cracks are likely to occur in the exterior film 50, increasing the possibility of deterioration of battery performance. On the other hand, in the present embodiment, since the exterior body 40 seals the electrode body 20 by winding the exterior film 50 around the electrode body 20, the electrode body 20 can be easily sealed regardless of the thickness of the electrode body 20. In order to reduce the dead space between the electrode body 20 and the exterior film 50 to improve the volumetric energy density of the power storage device 10, and in order to improve the cooling efficiency, a state in which the exterior film 50 is wound so as to contact the outer surface of the electrode body 20 is preferable. Also, in the all-solid-state battery, from the viewpoint that it is necessary to uniformly apply a high pressure from the outer surface of the battery to exhibit battery performance, it is also necessary to eliminate the space between the electrode body 20 and the exterior film 50, so a state in which the exterior film 50 is wound so as to contact the outer surface of the electrode body 20 is preferable.

[0028] In the present embodiment, with the exterior film 50 wound around the electrode body 20 so as to have the opening 40A, the surfaces (heat-sealable resin layers 53) of the exterior film 50 facing each other among the overhanging portions 50X are heat-sealed to form the first sealing portion 70.

[0029] The protruding portion 50X is configured to include a portion where a pair of opposing edge ends 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. In the exterior body 40, the position where the first sealing portion 70 is formed can be arbitrarily selected. In the present embodiment, it is preferable that the base 70X of the first sealing portion 70 is located on the side 43 at the boundary between the first surface 41 and the second surface 42 of the exterior body 40. The area of the first surface 41 is larger than that of 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 making the power storage device 10 compact, during use of the power storage device 10, the protruding portion 50X is folded, for example, onto the first surface 41 or the second surface 42 of the exterior body 40. In the present embodiment, during use of the power storage device 10, the protruding portion 50X is folded toward the second surface 42 of the exterior body 40.

[0030] In the present embodiment, the second sealing portion 80 is formed by heat-sealing the heat-fusible resin layer 53 of the exterior film 50 and the lid sealing portion 63 of the lid body 60 described later. That is, the exterior film 50 is joined to the lid body 60.

[0031] [Fixing member] FIG. 3 is a perspective view of the lid body 60 according to the present 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 total amount of the material constituting the lid body 60 is 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 still more preferably 95% by mass or more. That is, the material constituting the lid body 60 can contain materials other than the second material in addition to the second material.

[0032] The second material according to this embodiment is a resin. Specific examples of the resin include resins such as polyester, polyolefin, polyamide, epoxy resin, acrylic resin, fluororesin, polyurethane, silicone resin, and phenolic resin, and thermoplastic resins such as modified products of these resins. Further, the second material may be a mixture of these resins, a copolymer, or a modified product of a copolymer. Among these, the second material is preferably a heat-fusible resin such as polyester or polyolefin, and more preferably polyolefin. When the second material is a resin, the lid 60 may be molded by any molding method.

[0033] Specific examples of the polyester include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, copolyester, etc. Specific examples of the copolyester include copolyester having ethylene terephthalate as the main repeating unit. Specifically, a copolymer polyester obtained by polymerizing ethylene isophthalate with ethylene terephthalate as the main repeating unit (hereinafter abbreviated following polyethylene(terephthalate / isophthalate)), polyethylene(terephthalate / adipate), polyethylene(terephthalate / sodium sulfoisophthalate), polyethylene(terephthalate / sodium isophthalate), polyethylene(terephthalate / phenyl-dicarboxylate), polyethylene(terephthalate / decanedicarboxylate), etc. Among these, the second material is preferably polybutylene terephthalate from the viewpoint of enhancing heat resistance and pressure resistance.

[0034] In addition, examples of the polyolefin include polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; polypropylene such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); propylene-α-olefin copolymers; and terpolymers of ethylene-butene-propylene. The polyolefin resin in the case of being a copolymer may be a block copolymer or a random copolymer. Among these, polypropylene is preferable as the second material because it is excellent in heat sealability and electrolyte resistance.

[0035] The resin as the second material may contain a filler as necessary. Specific examples of the filler include glass beads, graphite, glass fibers, and carbon fibers. By containing the filler in the resin as the second material, the deformation resistance of the lid body 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 body 20. The second surface 62 is the surface on the opposite side of 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 constitutes the upper surface of the lid body 60. The first seal surface 63A extends in the width direction (LR direction) of the power storage device 10 in a front view of the lid body 60. The second seal surface 63B and the third seal surface 63C are connected to the first seal surface 63A and constitute the side surfaces of the lid body 60. The second seal surface 63B and the third seal surface 63C extend in the thickness direction (UD direction) of the power storage device 10 that intersects the width direction in a front view of the lid body 60. In the present embodiment, in a front view of the lid body 60, the width direction of the power storage device 10 and the thickness direction of the power storage device 10 are orthogonal to each other. The fourth seal surface 63D constitutes the lower surface of the lid body 60. The fourth seal surface 63D extends in the width direction (LR direction) in a front view of the lid body 60.

[0037] In the lid body 60 according to the present embodiment, a through hole 60X penetrating the first surface 61 and the second surface 62 is formed. The through hole 60X is rectangular in a front view of the lid body 60 in the present embodiment. The electrode terminal 30 penetrates the through hole 60X so as to protrude to the outside of the exterior body 40 in a state where the electrode body 20 is accommodated. In the present embodiment, the inner wall surface of the through hole 60X and the outer peripheral surface of the electrode terminal 30 facing the inner wall surface are adhesively fixed to each other via an adhesive film 31 described later. Thereby, as will be described later, the lid body 60 is fixed to the electrode terminal 30 along the second direction between one end portion 300 and the other end portion 301 of the electrode terminal 30. Hereinafter, as shown in FIG. 4, the lid body 60 to which the electrode terminal 30 is fixed may be referred to as an electrode terminal unit 600.

[0038] When the lid body 60 is plate-shaped, even when the power storage devices 10 are stacked, the lid body 60 preferably has a certain thickness so that the exterior body 40 is prevented from deforming. From another perspective, when the lid body 60 is plate-shaped, the lid seal portion 63 of the lid body 60 preferably has a certain 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 value of the 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 value of the thickness of the lid body 60 is, for example, 20 mm, more preferably 15 mm, and even more preferably 12 mm. The preferable range of the thickness of the material constituting the lid body 60 is 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, 4.0 mm to 12 mm. In the present embodiment, when the lid body 60 is described as plate-shaped, the film defined by the [Packaging Terms] standard of JIS (Japanese Industrial Standards) is not included as the material constituting the lid body 60. Note that the thickness of the lid body 60 may vary depending on the part of the lid body 60. When the thickness of the lid body 60 varies depending on the part, the thickness of the lid body 60 is the thickness of the thickest part.

[0039] In addition, from the perspective of suppressing the intrusion of at least one of moisture and gas into the exterior body 40 from between the lid body 60 and the exterior film 50, a barrier film 90 may be joined to the lid body 60. The barrier film 90 only needs to cover at least a part of the lid seal portion 63 of the lid body 60. In the present 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 body 60. The barrier film 90 may cover the boundaries 64 to 67. Since the barrier film 90 covers the lid seal portion 63, the boundaries 64 to 67, the second surface 62, and the inside of the through hole 60X, the intrusion of moisture into the exterior body 40 from between the electrode terminal 30 and the through hole 60X is suppressed. The barrier film 90 may be composed of a single film. For example, the portion covering the lid seal portion 63 and the portion covering the second surface 62 of the barrier film 90 may be configured separately. In other words, the barrier film 90 may be a plurality of divided films.

[0040] FIG. 6 is a cross-sectional view showing an example of the lid body 60 and the barrier film 90 joined thereto. The positions of the end portions 90A of the portion of the barrier film 90 covering the lid seal portion 63 and the end portions 90B of the portion covering the inside of the through hole 60X of the lid body 60 can be arbitrarily selected. When the power storage device 10 is a battery containing an electrolytic solution such as a lithium ion battery, there is a possibility that the gas such as hydrogen fluoride generated from the electrolytic solution comes into contact with the end portions 90A and 90B of the barrier film 90 and corrodes the barrier layer 91 provided in the barrier film 90 described later.

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

[0042] Figs. 7 to 9 are cross-sectional views showing examples of the layer structure of the barrier film 90. As shown in Fig. 7, the barrier film 90 only needs to include at least a barrier layer 91. The specifications regarding the barrier layer 91 are the same as those regarding 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 of only the barrier layer 91, one surface of the barrier layer 91 is joined to the lid body 60 by an adhesive or the like. When the barrier film 90 is a single layer of only the barrier layer 91, the other surface of the barrier layer 91 is joined to the heat-sealable resin layer 53 of the exterior film 50 by 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 joined to the lid body 60. The outer layer 92 serves, for example, as a base material layer or a heat-sealable resin layer. The role of the base material layer is to protect the barrier layer 91. The role of the heat-sealable resin layer is to heat-seal with the heat-sealable resin layer 53 of the outer packaging film 50. When the outer layer 92 serves as a base material layer, the specifications of the outer layer 92 as the base material layer are the same as those of the base material layer 51 of the outer packaging film 50. When the outer layer 92 serves as a heat-sealable resin layer, the specifications of the outer layer 92 as the heat-sealable resin layer are the same as those of the heat-sealable resin layer 53 of the outer packaging film 50. When the outer layer 92 serves as a heat-sealable resin layer, the outer layer 92 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 material layer, the barrier layer 91 is protected. When the outer layer 92 is a base material layer, the outer layer 92 and the heat-sealable resin layer 53 are joined, for example, by 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 preferably joined by heat-sealing. The barrier layer 91 and the outer layer 92 may be joined by 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 joined to the lid body 60. The specifications of the heat-sealable resin layer 93 are the same as those of the heat-sealable resin layer 53 of the outer packaging 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 body 60 can be preferably joined by heat-sealing. The barrier layer 91 and the heat-sealable resin layer 93 may be joined by an adhesive layer 55.

[0045] In addition, when the barrier film 90 is joined to the lid body 60, the material constituting the lid body 60 shall 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 power input / output in the electrode body 20. The electrode terminal 30 according to the present embodiment is formed, for example, in a plate shape having a thickness. Hereinafter, the thickness of the electrode terminal 30 is denoted as T (mm). The thickness T is the average value of the thickness values measured at three arbitrarily extracted locations in the portion of the electrode terminal 30 fixed to the lid body 60. In the present embodiment, the thickness direction of the electrode terminal 30 coincides with the thickness direction (UD direction) of the power storage device 10.

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

[0048] The electrode terminal 30 is composed of a first material. Here, "composed of a first material" means that when the total amount of the material constituting the electrode terminal 30 is 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 still more preferably 95% by mass or more. For example, when the electrode terminal 30 is composed of a metal containing an alloy, the metal becomes the first material. Further, for example, when the electrode terminal 30 has a main body composed of a metal containing an alloy and a plating layer composed of a metal containing an alloy and laminated on the outer surface of the main body, the metal constituting the main body becomes the first material.

[0049] The first material according to this embodiment is a metal. The metal is, for example, 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 usually aluminum or an aluminum alloy. On the other hand, the first material of the electrode terminal 30 connected to the negative electrode is usually copper, nickel, or a copper alloy. In this case, for example, the electrode terminal 30 can be a body made of copper as the first material with nickel plating applied thereto.

[0050] From the viewpoint of enhancing the electrolytic solution resistance, it is preferable that the surface of the electrode terminal 30 is subjected to formation treatment. For example, when the electrode terminal 30 is formed of aluminum, specific examples of the formation treatment include known methods for forming a corrosion-resistant film such as a phosphate, a chromate, a fluoride, or a triazine thiol compound. Among the methods for forming a corrosion-resistant film, a phosphoric acid chromate treatment using a composition composed of three components of a phenolic resin, a chromium(III) fluoride compound, and phosphoric acid is preferable.

[0051] An adhesive film 31 is joined to the outer peripheral surface of the electrode terminal 30 according to this embodiment. The adhesive film 31 can be arbitrarily selected as long as it is a film capable of bonding the electrode terminal 30 made of a metal as the first material and the lid body 60 made of a resin as the second material. The adhesive film 31 can use, for example, a polyolefin resin such as a polyethylene-based resin or a polypropylene-based 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 or a film of two or more layers thereof. In this embodiment, the adhesive film 31 is joined to the entire portion of the outer peripheral surface of the electrode terminal 30 that faces at least the inner wall surface of the through hole 60X.

[0052] Here, when viewed from the thickness direction of the power storage device 10, the direction in which the lid body 60 intersects the electrode terminal 30 is referred to as the second direction. The second direction intersects the first direction in the same plane as the first direction, while being orthogonal 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 the present embodiment, the second direction is orthogonal to the first direction and coincides with the width direction of the electrode terminal 30 and the width direction (LR direction) of the power storage device 10. Let the length in 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 be L0 (mm). In the present embodiment, since 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. Note that the length L1 is the average of the values obtained by measuring the lengths along the second direction at three arbitrarily selected locations on the portion of the electrode terminal 30 that is fixed to the lid body 60.

[0053] [Deformation resistance] The thermal shock test is a test for evaluating the deformation resistance of the power storage device 10 against temperature changes. The thermal shock test can be performed, for example, by a test apparatus that repeatedly moves a sample basket containing the power storage device 10 between a low-temperature chamber and a high-temperature chamber alternately, thereby subjecting the power storage device 10 to rapid temperature changes. 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 basket containing the power storage device 10 is, for example, 100 to 1500 times.

[0054] As a result of intensive studies, the present inventors have found that the degree of deformation of the electrode terminal 30 in the thermal shock test is contributed by the Vickers hardness h (HV) of the first material, the thickness T (mm) of the electrode terminal 30, the length L0 (mm), the linear expansion coefficient α1 (10 -6 / °C) of the first material, and the linear expansion coefficient α2 (10 -6 / °C) of the second material. More specifically, the "deformation resistance P (mm×HV 2 )", which is an index indicating the deformation resistance of the electrode terminal 30 in the thermal shock test, is defined as in the following formula (1). P = (h × T) 2 × (α1 / α2) ÷ L0 (1)

[0055] The ease of deformation of the electrode terminal 30 is contributed by 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. The larger the thickness T or the larger the Vickers hardness h of the first material, the more deformation is suppressed. In addition to this, it is considered that the ease of deformation of the electrode terminal 30 is also contributed by the fixing mechanism between the electrode terminal 30 and the lid body 60 and the difference in relative physical properties between the two. Specifically, the shorter the length in which the electrode terminal 30 is fixed to the inner wall surface of the through-hole 60X along the second direction, the less the electrode terminal 30 is affected by the dimensional change due to the temperature change of the lid body 60, and it is considered that the deformation is suppressed. Also, the smaller the difference in the dimensional change rate due to the temperature change between the electrode terminal 30 and the lid body 60, the less the electrode terminal 30 is affected by the dimensional change due to the temperature change of the lid body 60, and it is considered that the deformation is suppressed. The difference in the dimensional change rate due to the temperature change between the electrode terminal 30 and the lid body 60 can be specifically represented by 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 confirmed by 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 when a temperature change of -40 to 70 °C is performed 100 cycles. The deformation of the electrode terminal 30 was particularly prominent in the portion from the peripheral edge of the through-hole 60X, which is the fixed portion between the electrode terminal 30 and the lid body 60, to the other end portion 301. On the other hand, the inventors confirmed that when the deformation resistance P is 0.222 or more, no visible deformation occurs in the electrode terminal 30 even when the same cycle is performed.

[0057] The Vickers hardness h is a hardness evaluated by pressing a diamond indenter in the shape of a regular square pyramid onto the test surface of one sample of the first material at a test temperature of 23°C under a predetermined test force F (N), releasing the test load, and then calculating the average d (mm) of the lengths of a pair of diagonals of the indentation remaining on the sample surface. The test surface of the above sample shall coincide with the surface facing in the UD direction at the electrode terminal 30. The test force F during the measurement of the Vickers hardness h shall be 1.961 N, the pressing speed of the diamond indenter shall be 0.1 mm / s, the time until reaching the above test force F shall be 4 seconds, and the holding time of the test force shall be 12 seconds. Other measurement conditions shall be those described in JIS Z2244-1:2020. For existing energy storage devices, samples of the above first material can be obtained by removing the plating from the electrode terminals.

[0058] The linear expansion coefficient of a metal is the value measured by a push-in test using one sample of the metal in accordance with the method specified in JIS Z 2285:2003 and subjected to a total expansion type thermomechanical analyzer specified in JIS Z 2285:2003. The sample of the above metal shall be in the shape of a cube with a length of 1 mm × width of 1 mm × thickness of 1 mm, and the length direction shall coincide with the FB direction at the electrode terminal 30, the width direction shall coincide with the LR direction at the electrode terminal 30, and the thickness direction shall coincide with the UD direction at the electrode terminal 30. The parallelism tolerances at both ends in the length direction of the sample of the above metal shall be 25 μm as specified in JIS B 0621. The push-in load by the total expansion type thermomechanical analyzer shall be 10 g, the measurement temperature range shall be 20°C to 300°C, and the temperature increase rate shall be 5°C / min. As the reference material, quartz glass having the same shape and dimensions as the sample and having recommended values for thermal expansion and linear expansion coefficient shall be used. Also, the linear expansion coefficient of a resin is the value measured by a push-in test using one test piece of the resin in accordance with the method specified in JIS K 7197:2012 and subjected to a thermomechanical analysis (TMA) apparatus specified in JIS K 7197:2012. The test piece of the above resin shall be in the shape of a cube with a length of 1 mm × width of 1 mm × thickness of 1 mm, and the length direction shall coincide with the FB direction at the lid 60, the width direction shall coincide with the LR direction at the lid 60, and the thickness direction shall coincide with the UD direction at the lid 60. The parallelism at both ends in the length direction of the test piece of the above resin shall be ±25 μm. The push-in load by the thermomechanical analyzer shall be 10 g, the measurement temperature range shall be 20°C to 120°C, and the temperature increase rate shall be 5°C / min.

[0059] In the case where it is impossible to obtain a 1-mm thick metal sample along the UD direction from the electrode terminal of an existing power storage device, the method for measuring the coefficient of linear expansion of the first material may be changed. Specifically, the metal sample obtained from the electrode terminal can be sized to 15 mm in length (FB direction at the electrode terminal) × 3 mm in width (LR direction at the electrode terminal) × the thickness that can be collected (UD direction at the electrode terminal). In this case, the coefficient of linear expansion of the first material is the ratio of the change in the length of the sample with respect to temperature, which is measured by stretching the metal sample in the length direction using the above thermomechanical analyzer. The measurement temperature range in this measurement is set to 20°C to 300°C, and the temperature increase rate is 5°C / min. Also, the tensile load in the tensile test using the thermomechanical analyzer is 4 g. When the coefficient of linear expansion of the first material is measured by this method, or in the case where it is impossible to obtain the test piece of the above resin from the lid of an existing power storage device, the method for measuring the coefficient of linear expansion of the second material may be changed. Specifically, the test piece of resin obtained from the lid can be sized to 15 mm in length (FB direction at the lid) × 3 mm in width (LR direction at the lid) × the thickness that can be collected (UD direction at the lid). In this case, the coefficient of linear expansion of the second material is the ratio of the change in the length of the test piece with respect to temperature, which is measured by stretching the resin test piece in the length direction using the above thermomechanical analyzer. The measurement temperature range in this measurement is set to 20°C to 120°C, and the temperature increase rate is 5°C / min. Also, the tensile load in the tensile test using the thermomechanical analyzer is 4 g.

[0060] <2. Modification Example> As described above, several embodiments of the present invention have been explained, but the present invention is not limited to the above embodiments, and various changes are possible without departing from the spirit thereof. For example, the following changes are possible. Also, the gists of the following modification examples can be combined as appropriate.

[0061] (1) In the above-described embodiment, the electrode terminal 30 was fixed to the lid body 60 so as to penetrate the through-hole 60X of the lid body 60. However, as shown in FIG. 5, the lid body 60 may not have the through-hole 60X, and the electrode terminal 30 may be fixed between the first seal surface 63A or the fourth seal surface 63D and the heat-sealable resin layer 53 of the exterior film 50. Also in this case, the above formula (1) can be applied to calculate the deformation resistance P. In this case, the length L0 (mm) by which the electrode terminal 30 is fixed to the lid body 60 along the second direction is equal to the length L1 (mm) of the electrode terminal 30 along the second direction. Hereinafter, as shown in FIG. 5, the one in which the electrode terminal 30 is fixed to the lid body 60 may be referred to as an electrode terminal unit 601.

[0062] (2) In the above-described embodiment, the exterior body 40 had the exterior film 50 and the pair of lid bodies 60. However, the configuration of the exterior body 40 is not limited to that of the above-described embodiment. For example, the exterior film 50 may not be wound so as to contact the outer surface of the electrode body 20. Also, the location where the overhang portion 50X is formed is not limited to that of the above-described embodiment, and the overhang portion 50X itself may be omitted. Further, instead of the exterior film 50, a plurality of plate-like members made of the same material as that constituting the lid body 60 may be used to seal the electrode body.

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

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

[0065] (5) The exterior film 50 of the power storage device 10 may protrude outward from the lid body 60 in the depth direction (FB direction). The portion of the exterior film 50 that protrudes beyond the lid body 60 may be folded like a gable-top pouch or a brick-type pouch.

[0066] (6) The lid body 60 is not limited to a substantially rectangular shape. For example, it may be substantially circular, substantially elliptical, or substantially polygonal.

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

[0068] (1) The present invention can be implemented as electrode terminal units 600, 601 for a power storage device that at least partially constitute an exterior body 40 that seals the electrode body 20 of the power storage device 10, in addition to the power storage device 10 itself. 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 arranged along a first direction, and is configured such that one end 300 is connected to the electrode body 20 of the power storage device 10. The fixing member is fixed to the electrode terminal 30 along a second direction intersecting the first direction between the one end 300 and the other end 301 of the electrode terminal 30, and is made of a second material different from the first material. Let the Vickers hardness of the first material be h (HV), the thickness of the electrode terminal 30 along the direction orthogonal to the first direction and the second direction be T (mm), the linear expansion coefficient of the first material be α1, the linear expansion coefficient of the second material be α2, and the length of the electrode terminal fixed to the fixing member along the second direction be L0 (mm). Then, (h × T) 2 × (α1 / α2) ÷ L0 ≥ 0.222 is satisfied.

[0069] Each of the above electrode terminal units 600, 601 may have an adhesive film 31 and a barrier film 90.

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

Example

[0071] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

[0072] <Experiment> A lid made of resin and an electrode terminal made of metal were created, and these were fixed to each other using an adhesive resin to obtain samples of the exterior bodies according to Examples 1 to 5 and Comparative Examples 1 to 2. The lid and the electrode terminal were each formed to have a rectangular plate-like outer shape in all samples. The electrode terminal had one end and the other end along a first direction in all samples, and was fixed to the lid along a second direction orthogonal to the first direction between the one end and the other end. More specifically, the electrode terminal was fixed to the lid such 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. As shown in FIG. 4, the fixing mode of the lid and the electrode terminal was Mode 1 in which both surfaces of the electrode terminal penetrated through through holes formed in the lid, and as shown in FIG. 5, Mode 2 in which one surface of the electrode terminal was fixed to the sealing surface of the lid. A common adhesive film was used for fixing the lid and the electrode terminal in each sample. The first material constituting the electrode terminal according to 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) along the second direction in which the electrode terminal was fixed, the fixing mode of the electrode terminal, the second material constituting the lid, the linear expansion coefficient α1 (10 -6 / °C) of the first material, the linear expansion coefficient α2 (10 -6 / °C) of the second material, and the calculated deformation resistance P (mm × HV 2) was as shown in Table 1 below. The Vickers hardness h, the linear expansion coefficient α1, and the linear expansion coefficient α2 were measured by the methods described above. For reference, Table 1 also shows the alloy symbol and quality symbol of the metal used as the material constituting the electrode terminal.

Table 1

[0073] <Experimental Results> For each sample according to Examples 1 to 5 and Comparative Examples 1 to 2, it was visually confirmed that no deformation occurred in the electrode terminal before the thermal shock test. Next, each sample was set in the sample basket of the thermal shock test apparatus, and the operation of alternately moving between the low-temperature chamber maintained at -40°C and the high-temperature chamber maintained at 70°C was repeated 100 cycles (one round trip is one cycle). Then, each sample was taken out from the thermal shock test apparatus, and it was visually confirmed whether or not deformation occurred in the electrode terminal. The results were as shown in Table 2 below. A small thermal shock apparatus (TSE-12-A, manufactured by Espec Corporation) was used as the thermal shock test apparatus, but the apparatus used in the thermal shock test is not limited to this.

Table 2

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

Explanation of Signs

[0075] 10 Storage device 20 Electrode body 30 Electrode terminal 31 Adhesive film 40 Exterior body 50 Exterior film 60 Lid body (fixing member) 300 One end 301 The other end h Vickers hardness T Thickness Fixing length between the L0 cover and the electrode terminal α1, α2 Coefficient of linear expansion

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 is An exterior film that wraps the electrode body; a fixing member is provided 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 the first direction, the fixing member being made of a second material different from the first material; The fixing member is a separate element from the exterior film, 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 Fulfilling The first material is aluminum, copper, or an aluminum alloy, and the second material is polypropylene. Energy storage device.

2. an electrode terminal having one end and another end arranged along a first direction, the one end being 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 between the one end and the other end of the electrode terminal along a second direction intersecting the first direction, the fixing member being made of a second material different from the first material; Equipped with the fixing member is an element separate from an exterior film that encases the electrode body, 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 Fulfilling The first material is aluminum, copper, or an aluminum alloy, and the second material is polypropylene. An electrode terminal unit for an electricity storage device.

3. The electrode terminal unit for an electricity storage device according to claim 2; the exterior film joined to the electrode terminal unit; Equipped with An exterior body set for an energy storage device.

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