Power storage device

Abstract

A power storage device (10) comprises: a bottomed cylindrical case (20) having an opening (20B); and a current collection member (30) welded to the outer surface of the case (20). The current collection member (30) has: an elastic portion (31) which is formed in an arc shape and welded to the outer surface of the case (20); and an extension portion (32) which is connected to the elastic portion (31) and extends outward in the radial direction of the case (20). The elastic portion (31) is disposed so as to surround at least half of the circumference but less than the entire circumference of the outer surface of the case (20), and the elastic portion (31) has a contact section (31T) in contact with the outer surface of the case (20). The contact section (31T) presses the outer surface of the case (20).

Description

Electric storage device

[0001] The present disclosure relates to an electric storage device.

[0002] The electric storage device has, for example, a bottomed cylindrical case, an electrode body housed in the case, and a sealing body that closes the opening of the case. Further, the electric storage device has a current collecting member connected to the sealing body as a positive electrode terminal or the case as a negative electrode terminal (for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2002-011448

[0004] In a configuration in which the current collecting member is connected to the shoulder portion of the case as in the electric storage device disclosed in Patent Document 1, when a misalignment occurs between the current collecting member and the shoulder portion of the case, it is difficult to connect the current collecting member and the shoulder portion of the case. Further, in a configuration in which the current collecting member is connected to the shoulder portion of the case, since both the shoulder portion of the case and the sealing body are located on the upper surface of the electric storage device, there is a risk of a short circuit between the positive and negative electrodes. Therefore, in the electric storage device, it is required to reduce the risk of misalignment between the current collecting member and the shoulder portion or a short circuit between the positive and negative electrodes and improve the reliability.

[0005] Therefore, an object of the present disclosure is to provide an electric storage device capable of improving reliability.

[0006] The electric storage device according to the present disclosure includes a bottomed cylindrical case having an opening, and a current collecting member welded to the outer surface of the case. The current collecting member is formed in an arc shape and has an elastic portion welded to the outer surface of the case and an extension portion connected to the elastic portion and extending radially outward of the case. The elastic portion is arranged so as to surround more than half a circumference and less than one circumference of the outer surface of the case, and the elastic portion has a contact portion that contacts the outer surface of the case, and the contact portion presses the outer surface of the case.

[0007] According to the electric storage device of the present disclosure, the reliability can be improved.

[0008] This is a cross-sectional view showing an example of an embodiment of a power storage device. This is a perspective view showing an example of an embodiment of a power storage device. This is a diagram illustrating a state in which the current collector has been removed. This is a plan view showing an example of an embodiment of a power storage device. This is a cross-sectional view showing an example of an embodiment of a current collector. This is a cross-sectional view showing another example of an embodiment of a current collector. This is a plan view showing another example of an embodiment of a current collector. This is a schematic diagram showing another example of an embodiment of a current collector. This is a schematic diagram showing another example of an embodiment of a current collector.

[0009] An example of an embodiment of this disclosure will be described in detail below. In the following description, specific shapes, materials, directions, numerical values, etc., are examples provided to facilitate understanding of this disclosure and can be modified as appropriate to suit the application, purpose, specifications, etc.

[0010] [Energy Storage Device] An example of an embodiment, an energy storage device 10, will be described using Figure 1.

[0011] The energy storage device 10 of this embodiment is a non-aqueous electrolyte secondary battery (lithium-ion battery) using a non-aqueous electrolyte. However, the energy storage device of this disclosure is not limited to the non-aqueous electrolyte secondary battery of this embodiment, and may be a primary battery or a battery using an aqueous electrolyte. Furthermore, the energy storage device 10 is a cylindrical battery.

[0012] In the following, each component may be described using the axial, radial, and circumferential directions of the energy storage device 10. Also, the side of the sealing body 21 in the axial direction (height direction) of the energy storage device 10 may be referred to as "upper," and the side of the bottom 20A of the case 20 in the axial direction may be referred to as "lower."

[0013] The energy storage device 10 comprises an electrode body 14, a non-aqueous electrolyte, a bottomed cylindrical case 20 having an opening for housing the electrode body 14 and the electrolyte, a sealing body 21 for closing the opening of the case 20, and a current collector member 30 welded to the outer surface of the case 20. The electrode body 14 includes a positive electrode 11, a negative electrode 12, and a separator 13 interposed between the positive electrode 11 and the negative electrode 12, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound around each other via the separator 13. The case 20 is a bottomed cylindrical container having a bottom 20A and an opening 20B.

[0014] The electrode body 14 has a long positive electrode 11, a long negative electrode 12, and two long separators 13. The electrode body 14 also has electrode leads, a positive electrode lead 15 joined to the positive electrode 11 and a negative electrode lead 16 joined to the negative electrode 12. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to suppress lithium deposition. Therefore, the lower end of the negative electrode 12 is positioned closer to the bottom 20A of the case 20 than the lower end of the positive electrode 11. The two separators 13 are formed to be at least slightly larger than the positive electrode 11 and are arranged, for example, to sandwich the positive electrode 11.

[0015] The positive electrode 11 comprises a positive electrode core and positive electrode mixture layers provided on both sides of the positive electrode core. The positive electrode core can be made of a metal foil that is stable within the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film with the metal arranged on its surface. The positive electrode mixture layers contain a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride (PVdF). The positive electrode 11 can be manufactured by applying a positive electrode mixture slurry containing the positive electrode active material, conductive agent, binder, etc., onto the positive electrode core, drying the coating, and then compressing it to form the positive electrode mixture layers on both sides of the positive electrode core.

[0016] For example, lithium transition metal composite oxides are used as positive electrode active materials. Examples of metal elements contained in lithium transition metal composite oxides include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, and W. An example of a suitable lithium transition metal composite oxide is a lithium metal composite oxide containing at least one of Ni, Co, and Mn. Specific examples include composite oxides containing Ni, Co, and Mn, and composite oxides containing Ni, Co, and Al.

[0017] The negative electrode 12 comprises a negative electrode core and negative electrode mixture layers provided on both sides of the negative electrode core. The negative electrode core can be made of a metal foil that is stable within the potential range of the negative electrode 12, such as copper or a copper alloy, or a film with the metal arranged on its surface. The negative electrode mixture layers contain a negative electrode active material and a binder such as styrene-butadiene rubber (SBR). The negative electrode 12 can be manufactured by applying a negative electrode mixture slurry containing the negative electrode active material and binder onto the negative electrode core, drying the coating, and then compressing it to form the negative electrode mixture layers on both sides of the negative electrode core.

[0018] The negative electrode active material can be natural graphite such as flake graphite, lump graphite, or clay-like graphite, or artificial graphite such as lump graphite or graphitized mesophase carbon microbeads. The negative electrode active material may also be metals that alloy with lithium, such as Si and Sn, alloys containing such metals, or compounds containing such metals, and these may be used in combination with graphite. A preferred example of the active material is SiO ２ This is a Si-containing material in which Si fine particles are dispersed in a silicate phase such as lithium silicate, or in an amorphous carbon phase.

[0019] For example, a porous sheet having ion permeability and insulating properties can be used for the separator 13. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. Suitable materials for the separator 13 include polyethylene, olefin resins such as polypropylene, and cellulose. The separator 13 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin resin. Alternatively, it may be a multilayer separator containing a polyethylene layer and a polypropylene layer, or a separator 13 with a material such as aramid resin or ceramic coated on its surface may be used.

[0020] Non-aqueous electrolytes include, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Non-aqueous solvents can include esters, ethers, nitriles, amides, and mixtures of two or more of these. The non-aqueous solvent may also contain halogen-substituted solvents in which at least some of the hydrogen atoms in the solvent are replaced with halogen atoms such as fluorine. Note that non-aqueous electrolytes are not limited to liquid electrolytes, but may also be solid electrolytes using gel-like polymers, etc. The electrolyte salt may be LiPF ６ Lithium salts such as these are used.

[0021] An upper insulating plate 17 and a lower insulating plate 18 are positioned above and below the electrode body 14, respectively. In the example shown in Figure 1, a positive electrode lead 15 attached to the positive electrode 11 extends towards the sealing body 21 through the opening in the upper insulating plate 17, and a negative electrode lead 16 attached to the negative electrode 12 extends towards the bottom 20A of the case 20 through the outside of the lower insulating plate 18. The positive electrode lead 15 is connected by welding or the like to the inner surface of the valve portion 21A of the sealing body 21 that faces inward towards the case 20, so that the sealing body 21 becomes the positive electrode terminal. The negative electrode lead 16 is connected by welding or the like to the inner surface of the bottom 20A of the case 20, so that the case 20 becomes the negative electrode terminal.

[0022] A gasket 19 is provided between the case 20 and the sealing body 21 to ensure airtightness inside the battery and insulation between the case 20 and the sealing body 21. The case 20 includes an opening 20B, an annular groove 20C along the circumferential direction, and an annular shoulder 20D. The groove 20C is formed by spinning the opening 20B to create a recess on the radially inward side. The shoulder 20D is formed when the opening 20B is folded radially inward and crimped to the periphery of the sealing body 21. The sealing body 21 is fixed to the case 20 by being sandwiched between the shoulder 20D and the groove 20C via the gasket 19 through the crimping process.

[0023] The sealing body 21 is a disc-shaped member equipped with an exhaust valve. The sealing body 21 has a valve portion 21A that ruptures when the internal pressure of the battery exceeds a predetermined threshold. The valve portion 21A includes a downward convex portion that is convex to the inside of the battery and located in the radial center, and a thin-walled portion formed around the downward convex portion. The thickness of the thin-walled portion decreases towards the radial outside. When the internal pressure rises due to a malfunction of the energy storage device 10, the thin-walled portion ruptures, forming a gas outlet.

[0024] [Current Collector] A current collector 30, which is an example of an embodiment, will be described using Figures 2 to 5.

[0025] As shown in Figure 2, the current collector 30 is a component that is electrically connected to the energy storage device 10. The current collector 30 is connected to the shoulder portion 20D of the case 20, which serves as the negative electrode terminal. The current collector 30 can improve the reliability of the energy storage device 10, as will be described in detail later. The current collector 30 is made of a conductive metal, for example, copper. The current collector 30 has an elastic portion 31 which is formed in an arc shape and welded to the outer surface of the case 20, and an extended portion 32 which is connected to the elastic portion 31 and extends radially outward from the case 20, as will be described in detail later.

[0026] The elastic portion 31 is formed in an arc shape. More specifically, the elastic portion 31 is positioned on the outer surface of the case 20 so as to surround more than half the circumference but less than one circumference of the outer surface of the case 20. The elastic portion 31 presses against the outer surface of the case 20 at the contact portion 31T, which will be described later. The elastic portion 31 is also welded to the outer surface of the case 20 at the contact portion 31T. As a result, the elastic portion 31 is electrically connected to the case 20 at the outer surface of the case 20.

[0027] As shown in Figure 3, the elastic portion 31 is elastic in the radial direction. More specifically, when the elastic portion 31 is expanded in the radial direction, it shrinks back to its original shape. Also, the inner diameter D1 of the elastic portion 31 is smaller than the outer diameter D2 of the case 20 when the current collector member 30 (elastic portion 31) is removed from the case 20. With this configuration, the elastic portion 31 is fitted onto the outer surface of the case 20. This fixes the elastic portion 31 to the outer surface of the case 20.

[0028] As shown in Figure 4, the elastic portion 31 has a contact portion 31T that contacts the outer surface of the case 20 and a non-contact portion 31N that does not contact the outer surface of the case 20, because, as described above, the inner diameter D1 of the elastic portion 31 is smaller than the outer diameter D2 of the case 20. The contact portion 31T includes one end 31A and the other end 31B of the elastic portion 31. The elastic portion 31 extends from one end 31A to the other end 31B and has a C-shape when viewed from the axial direction of the case 20. The contact portion 31T is provided at one end 31A and the other end 31B of the elastic portion 31. The contact portion 31T also includes a connecting portion 31C that connects to the extending portion 32. The connecting portion 31C may be an arc-shaped central portion of the elastic portion 31.

[0029] In this embodiment, the elastic portion 31 has one end 31A, the other end 31B, and the connecting portion 31C functioning as contact portions 31T, but the present invention is not limited thereto. In the present invention, portions other than the one end, the other end, and the connecting portion may also be contact portions. Furthermore, in the present invention, it is preferable that there are at least two or more contact portions.

[0030] As described above, the contact portion 31T presses the outer surface of the case 20 radially inward because the elastic portion 31 is elastic in the radial direction. More specifically, in this disclosure, one end 31A and the other end 31B press against the outer surface of the case 20. With this configuration, as described above, the elastic portion 31 is securely fitted to the outer surface of the case 20. This securely fixes the elastic portion 31 to the outer surface of the case 20.

[0031] The elastic portion 31 is welded to the outer surface of the case 20. This electrically connects the elastic portion 31 to the outer surface of the case 20. In this embodiment, the contact portion 31T (e.g., connecting portion 31C) and the non-contact portion 31N are welded to the outer surface of the case 20, but the disclosure is not limited thereto. In this disclosure, it is preferable that at least one contact portion is welded to the outer surface of the case. Welding the contact portion 31T to the case 20 increases the connection strength between the current collector member 30 and the case 20. The current collector member 30 and the case 20 may also be welded between the non-contact portion 31N and the outer surface of the case 20. Welding the non-contact portion 31N to the case 20 increases the welding area, making it less likely for the current collector member 30 and the case 20 to come loose. In this case, the non-contact portion 31N may be about 0.1 mm away from the case 20.

[0032] In this embodiment, the elastic portion 31 and the outer surface of the case 20 are joined by laser welding, but the disclosure is not limited thereto. In this disclosure, the elastic portion 31 and the outer surface of the case 20 may be joined by, for example, arc welding, ultrasonic welding, electron beam welding, etc.

[0033] Conventionally, in configurations where, for example, the current collector is connected to the shoulder of the case, and both the shoulder of the case and the sealing body acting as the positive terminal are located on the upper surface of the energy storage device, there was a risk of short-circuiting the positive and negative terminals. However, in this embodiment, where the current collector 30 is electrically connected to the outer surface of the case 20 of the energy storage device 10, the risk of short-circuiting the positive and negative terminals is reduced. This improves the reliability of the energy storage device 10.

[0034] Furthermore, in conventional configurations, for example, where the current collector is connected to the shoulder of the case, if there is a misalignment between the current collector and the shoulder, it becomes difficult to connect the current collector to the shoulder of the case. However, in this embodiment, where the current collector 30 is arranged to surround more than half the circumference but less than one circumference of the outer surface of the case 20, the position of the current collector 30 and the outer surface of the case 20 is determined with high precision, making it less likely for the current collector 30 and the outer surface of the case 20 to misalign, and making it easy to connect the current collector 30 to the outer surface of the case 20. This improves the reliability of the energy storage device 10.

[0035] As shown in Figure 5, the elastic portion 31 has an upper surface portion 31U. At the connection portion 31C of the elastic portion 31, the upper surface portion 31U is connected to the stretch portion 32. More specifically, the upper surface portion 31U is formed continuously with the stretch portion 32. Formed continuously means that the upper surface of the stretch portion 32 and the upper surface portion 31U of the elastic portion 31 are provided flush with each other. The elastic portion 31 and the stretch portion 32 are provided and connected from the same material, or they are provided by connecting the two materials by welding or the like. At the contact portion 31T of the elastic portion 31, the weld portion Y between the contact portion 31T and the outer surface of the case 20 is formed on the upper surface portion 31U. In other words, in the manufacturing process of the energy storage device 10, the contact portion 31T and the outer surface of the case 20 are welded from above the energy storage device 10. The weld marks have a shape that tapers downwards from above the energy storage device 10.

[0036] Conventionally, in configurations where the current collector is welded to the shoulder of the case, the horizontal portion of the gasket located below the shoulder (corresponding to 19A in the figure in this embodiment) was greatly affected by the heat from welding. Furthermore, the horizontal portion of the gasket located below the shoulder is the part that is crimped and compressed by the shoulder and greatly contributes to the sealing performance of the gasket. Therefore, the heat from welding the shoulder to the horizontal portion was significant, and there was a risk that the sealing performance of the gasket would deteriorate.

[0037] However, in this embodiment, where the contact portion 31T of the elastic portion 31 is welded to the outer surface of the case 20, the vertical portion 19B is significantly affected by the welding of the outer surface of the case 20. On the other hand, the horizontal portion 19A is less affected by the heat compared to the vertical portion 19B. Also, since the vertical portion 19B is not a part that is crimped and compressed by the shoulder portion 20D, its contribution to the sealing performance of the gasket 19 is small. As a result, the risk of heat effects due to welding between the current collector member 30 and the case 20 can be reduced compared to the conventional method. Consequently, the risk of a decrease in the sealing performance of the gasket 19 can be reduced. This improves the reliability of the energy storage device 10.

[0038] Again, as shown in FIGS. 2 and 3, the extension portion 32 is connected to the elastic portion 31 and extends radially outward of the case 20. One side of the extension portion 32 is connected to the connection portion 31C of the elastic portion 31. The other side of the extension portion 32 may be connected to, for example, the positive electrode terminal of another power storage device 10 or may be connected to the negative electrode terminal of another power storage device 10. Note that the other side of the extension portion 32 may be connected to the elastic portion of the current collecting member fitted to another power storage device 10 and connected to another power storage device 10.

[0039] [Another Embodiment (Current Collecting Member)] A current collecting member 30 which is another example of the embodiment will be described with reference to FIGS. 6 to 9.

[0040] In the embodiment described below, the same components as those of the current collecting member 30 described above are denoted by the same reference numerals and detailed description thereof is omitted. Also, in the embodiment described below, the current collecting member 30 has the same operations and effects as those described above.

[0041] As shown in FIGS. 6 and 7, the elastic portion 31 of the current collecting member 30 has a covering portion 31H that covers the upper surface of the case 20. The covering portion 31H is formed in an arc shape (C shape). The covering portion 31H is formed integrally with the elastic portion 31. A groove 31V is provided on the inner peripheral edge of the covering portion 31H. The groove 31V of the present embodiment is formed in a V shape in plan view, but the present disclosure is not limited thereto. The groove of the present disclosure may be formed in a rectangular shape, a semi-circular shape, or the like in plan view.

[0042] According to the covering portion 31H, the current collecting member 30 is stably fixed in the case 20. Thereby, it is possible to prevent the current collecting member 30 from falling off the case 2.In addition, the workability when welding the contact portion 31T of the elastic portion 31 and the outer surface of the case 20 can be improved. Also, according to the covering portion 31H, the axial position accuracy of the current collecting member 30 with respect to the case 20 can be improved.

[0043] Further, according to the groove 31V, for example, when the current collecting member 30 having the covering portion 31H is formed by bending, the covering portion 31H can be easily formed. Thereby, the workability during the manufacture of the power storage device 10 can be improved.

[0044] As shown in FIG. 8, one end portion 31A and the other end portion 31B of the elastic portion 31 of the current collector member 30 are bent outward in the radial direction to form bent portions 31R. The pair of bent portions 31R are preferably provided so as to taper when viewed from the outside in the radial direction. The bending angle of the bent portion 31R is not particularly limited. It is only necessary that the tips of the one end portion 31A and the other end portion 31B face outward in the radial direction. The bent portion 31R is preferably bent with a curvature of a predetermined ratio or less.

[0045] With the above configuration, when the elastic portion 31 of the current collector member 30 is fitted onto the outer surface of the case 20 from the radial direction, the bent portion 31R serves to prevent the fitting of the elastic portion 31 and the case 20 from getting caught and plays a role of guiding. Therefore, the elastic portion 31 can be easily pushed into the case 20. In other words, the elastic portion 31 of the current collector member 30 can be easily fitted onto the outer surface of the case 20 from the radial direction. Thereby, the workability during the manufacture of the power storage device 10 can be improved.

[0046] As shown in FIG. 9, the lower end portion 31S of the elastic portion 31 of the current collector member 30 is bent outward in the radial direction. In other words, the lower end portion 31S of the elastic portion 31 of the current collector member 30 is formed so as to increase the diameter with respect to the elastic portion 31. The bending angle of the lower end portion 31S with respect to the vertical direction is preferably 10° to 45°.

[0047] With the above configuration, when the elastic portion 31 of the current collector member 30 is fitted onto the outer surface of the case 20 from above in the axial direction, the lower end portion 31S serves to prevent the fitting of the elastic portion 31 and the case 20 from getting caught and plays a role of guiding. Therefore, the elastic portion 31 can be easily pushed into the case 20. In other words, the elastic portion 31 of the current collector member 30 can be easily fitted onto the outer surface of the case 20 from above in the axial direction. Thereby, the workability during the manufacture of the power storage device 10 can be improved.

[0048] [Summary] The present disclosure is further illustrated by the following embodiments. Configuration 1: A power storage device comprising a bottomed cylindrical case having an opening, and a current collector member welded to the outer surface of the case, wherein the current collector member has an arc-shaped elastic portion welded to the outer surface of the case, and an extendable portion connected to the elastic portion and extending radially outward from the case, wherein the elastic portion is arranged on the outer surface of the case to surround more than half a circumference but less than one circumference of the outer surface of the case, and the elastic portion has a contact portion that contacts the outer surface of the case, and the contact portion presses against the outer surface of the case. Configuration 2: The power storage device according to Configuration 1, wherein the contact portion includes one end of the elastic portion and the other end of the elastic portion. Configuration 3: A power storage device according to Configuration 2, wherein the elastic portion has a non-contact portion that is not in contact with the outer surface of the case, and the non-contact portion is located between the contact portion and the one end. Configuration 4: A power storage device according to Configuration 1, wherein when the current collector is removed from the case, the inner diameter of the elastic portion of the current collector is smaller than the outer diameter of the case. Configuration 5: A power storage device according to Configuration 1, further comprising an electrode body housed in the case, a sealing body positioned above the electrode body and closing the opening of the case, and a gasket sandwiched between the opening of the case and the sealing body, wherein the elastic portion and the outer surface of the case are welded together. Configuration 6: A power storage device according to Configuration 1, wherein the elastic portion includes an upper surface connected to the extension portion, and a welded portion between the elastic portion and the outer surface of the case is formed on the upper surface. Configuration 7: An energy storage device according to Configuration 1, wherein the current collector has a covering portion that covers the upper surface of the case, and the covering portion and the elastic portion are integrally formed. Configuration 8: An energy storage device according to Configuration 7, wherein the covering portion has a groove that is recessed in the direction from the inner circumference toward the outer circumference of the covering portion.Configuration 9: A power storage device according to any one of Configurations 1 to 8, wherein one end and the other end of the elastic part are bent radially outward. Configuration 10: A power storage device according to any one of Configurations 1 to 8, wherein the lower end of the elastic part is bent radially outward.

[0049] It should be noted that this disclosure is not limited to the embodiments and their modifications described above, and various changes and improvements are possible within the scope of the claims of this application.

[0050] 10 Energy storage device, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15 Positive electrode lead, 16 Negative electrode lead, 17 Upper insulating plate, 18 Lower insulating plate, 19 Gasket, 19A Horizontal part, 19B Vertical part, 20 Case, 20A Bottom part, 20B Opening, 20C Grooved part, 20D Shoulder part, 21 Sealing body, 21A Valve part, 30 Current collector, 31 Elastic part, 31A One end, 31B Other end, 31C Connection part, 31H Covering part, 31N Non-contact part, 31R Bent part, 31S Lower end, 31T Contact part, 31U Top surface part, 31V Groove, 32 Extending part, Y Welded part

Claims

1. A power storage device comprising a bottomed cylindrical case having an opening, and a current collector member welded to the outer surface of the case, wherein the current collector member is formed in an arc shape and has an elastic portion welded to the outer surface of the case, and an extendable portion connected to the elastic portion and extending radially outward from the case, the elastic portion is arranged on the outer surface of the case to surround more than half a circumference but less than one full circumference of the outer surface of the case, the elastic portion has a contact portion that contacts the outer surface of the case, and the contact portion presses against the outer surface of the case.

2. The energy storage device according to claim 1, wherein the contact portion includes one end of the elastic portion and the other end of the elastic portion.

3. The energy storage device according to claim 2, wherein the elastic portion has a non-contact portion that is not in contact with the outer surface of the case, and the non-contact portion is located between the contact portion and the one end.

4. The energy storage device according to claim 1, wherein when the current collector is removed from the case, the inner diameter of the elastic portion of the current collector is smaller than the outer diameter of the case.

5. The energy storage device according to claim 1, further comprising: an electrode body housed in the case; a sealing body positioned above the electrode body and closing the opening of the case; and a gasket sandwiched between the opening of the case and the sealing body, wherein the contact portion and the outer surface of the case are in contact, and the elastic portion and the outer surface of the case are welded together.

6. The energy storage device according to claim 1, wherein the elastic portion includes an upper surface portion formed continuously with the stretched portion, and a welded portion is formed on the upper surface portion between the elastic portion and the outer surface of the case.

7. The current collector has a covering portion that covers the upper surface of the case, and the covering portion and the elastic portion are integrally formed, as described in claim 1.

8. The energy storage device according to claim 7, wherein the covering portion has grooves that are recessed in the direction from the inner circumference toward the outer circumference of the covering portion.

9. The energy storage device according to any one of claims 1 to 8, wherein one end and the other end of the elastic portion are bent radially outward.

10. The lower end of the elastic portion is bent radially outward, the energy storage device according to any one of claims 1 to 8.

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