Electricity storage device

Abstract

A power storage device (10) is provided with: an electrode body (14) in which a positive electrode plate (11) and a negative electrode plate (12) are laminated with a separator (13) interposed therebetween; and a negative electrode collector plate (40) disposed on one end side in the axial direction (P) of the electrode body (14), the negative electrode collector plate (40) having an extension part (43) extending in the stacking direction of the positive electrode plate (11) and the negative electrode plate (12), and an urging part (46) for urging the inside of the outer can (20) being provided at an end part on the outer peripheral side of the extension part (43).

Description

Technical Field

[0001] The present invention relates to a current collector plate for an electricity storage device. Background Art

[0002] Cylindrical batteries, one type of energy storage device, have a wound electrode body composed of a positive electrode plate and a negative electrode plate wound with a separator interposed therebetween. In addition, large-diameter cylindrical batteries sometimes have a structure in which a negative electrode current collector plate is bonded to the exposed portion of the negative electrode core material protruding from the wound electrode body (hereinafter referred to as an end-face current collection structure) (e.g., Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-203374 Summary of the Invention

[0006] On the other hand, power storage devices are required to have high capacity and high output, and these requirements are accompanied by a demand for reliability.

[0007] Therefore, an object of the present invention is to provide a power storage device capable of improving reliability.

[0008] The present invention provides an electricity storage device comprising: an electrode body formed by stacking a first electrode plate and a second electrode plate with a separator therebetween; a current collector plate arranged on one axial end side of the electrode body; and an outer can that accommodates the electrode body and the current collector plate, characterized in that the current collector plate has an extension portion that extends along the stacking direction of the first electrode plate and the second electrode plate, and a force applying portion that applies force to the inner side of the outer can is provided at the end portion on the outer peripheral side of the extension portion.

[0009] According to the power storage device of the present invention, reliability can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic cross-sectional view showing an electric storage device as an example of an embodiment.

[0011] Figure 2 It is a perspective view showing a negative electrode current collector plate as an example of an embodiment.

[0012] Figure 3 This is another perspective view showing a negative electrode current collector plate as an example of an embodiment.

[0013] Figure 4 It is a perspective view showing a force applying portion.

[0014] Figure 5A This is a schematic diagram showing a state where the negative electrode current collecting plate and the outer can are not centered.

[0015] Figure 5B This is a schematic diagram showing the negative electrode current collector plate and the outer can in a centered state. DETAILED DESCRIPTION

[0016] In the following description, specific shapes, materials, directions, numerical values, etc. are illustrative for easy understanding of the present invention and can be appropriately changed according to the application, purpose, specifications, etc.

[0017] [Electricity Storage Device]

[0018] use Figure 1 A power storage device 10 as an example of an embodiment will be described.

[0019] The power storage device 10 is used, for example, as a power source for electric vehicles. However, the power storage device of the present invention is not limited to power sources for electric vehicles. For example, it can also be used as a power source for motor-driven electric devices such as power tools, power-assisted bicycles, electric motorcycles, electric wheelchairs, electric tricycles, and electric scooters. Furthermore, the power storage device of the present invention can also be used as a power source for various electrical devices used indoors and outdoors, such as cleaners, wireless devices, lighting devices, digital cameras, and video cameras.

[0020] The electricity storage device 10 includes a wound electrode assembly 14 formed by winding a positive electrode plate 11 (a first electrode plate) and a negative electrode plate 12 (a second electrode plate) with a separator 13 interposed therebetween; an outer can 20 that houses the electrode assembly 14; and a sealing member 30 that seals the opening of the outer can 20. The outer can 20 houses an electrolyte along with the electrode assembly 14. While the electrolyte in this embodiment is a non-aqueous electrolyte, an aqueous electrolyte may also be used. The electricity storage device may also be a capacitor.

[0021] Hereinafter, each component may be described using the axial direction P, the circumferential direction R, and the radial direction D. For convenience of description, the side in the axial direction P where the sealing body 30 is provided is sometimes described as the upper side, and the side where the bottom 20B of the outer can 20 is formed is sometimes described as the lower side.

[0022] The positive electrode plate 11, the negative electrode plate 12 and the separator 13 are all strip-shaped long bodies, which are wound in a spiral shape. At this time, the positive electrode plate 11 and the negative electrode plate 12 are staggered and stacked in a manner that protrudes to opposite sides in the axial direction P (the height direction of the storage device 10). In order to prevent the precipitation of lithium, the composite material layer of the negative electrode plate 12 can be formed to be one size larger than the composite material layer of the positive electrode plate 11. That is, the composite material layer of the negative electrode plate 12 can be formed to be longer than the composite material layer of the positive electrode plate 11 in the long side direction and the width direction (short side direction). The separator 13 is formed to be at least one size larger than the positive electrode plate 11. For example, two separators 13 are arranged in a manner that sandwiches the positive electrode plate 11. In addition, the electrode body 14 does not necessarily have to be composed of a state in which the positive electrode plate 11 and the negative electrode plate 12 are wound. For example, the electrode body 14 can also be composed of a plurality of positive electrode plates 11 and a plurality of negative electrode plates 12 alternately stacked.

[0023] The positive electrode plate 11 includes a positive electrode core and a positive electrode mixture layer formed on at least one surface of the core. The positive electrode core can be made of a metal foil, such as aluminum or an aluminum alloy, that is stable within the potential range of the positive electrode plate 11, or a film having such a metal disposed on the surface. The positive electrode mixture layer includes, for example, a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride. The positive electrode mixture layer is preferably formed on both surfaces of the positive electrode core. For example, a lithium transition metal composite oxide is used as the positive electrode active material.

[0024] The negative electrode plate 12 includes a negative electrode core and a negative electrode mixture layer formed on at least one surface of the core. The negative electrode core can be made of a metal foil, such as copper or a copper alloy, that is stable within the potential range of the negative electrode plate 12, or a thin film having the metal disposed on the surface. The negative electrode mixture layer includes, for example, a negative electrode active material and a binder such as styrene-butadiene rubber (SBR), and is preferably formed on both surfaces of the negative electrode core. For example, graphite or a silicon-containing compound can be used as the negative electrode active material.

[0025] The non-aqueous electrolyte contained in the outer tank 20 includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. For the non-aqueous solvent, for example, esters, ethers, nitriles, amides and mixed solvents of two or more thereof can be used. The non-aqueous solvent may contain a halogen substituted body obtained by replacing at least a portion of the hydrogen atoms of these solvents with halogen atoms such as fluorine. As an example of a non-aqueous solvent, ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC) and mixed solvents thereof can be cited. For the electrolyte salt, for example, lithium salts such as LiPF6 can be used. In addition, the non-aqueous electrolyte may also be a gel electrolyte, a solid electrolyte, etc. instead of an electrolyte solution.

[0026] Above the electrode body 14, there are provided a positive electrode lead 15 extending from the upper end of the electrode body 14 in the axial direction P and connecting the positive electrode plate 11 constituting the electrode body 14 to the current collector 32 of the sealing body 30; and an upper insulating plate 16 disposed between the electrode body 14 and the sealing body 30. The positive electrode lead 15 electrically connects the positive electrode plate 11 and the sealing body 30. As a result, the positive electrode cap 31 of the sealing body 30 functions as a positive electrode external terminal, which serves as a first electrode external terminal. The upper insulating plate 16 prevents the positive electrode plate 11 and the positive electrode lead 15 from contacting the outer can 20 and prevents the positive electrode lead 15 from contacting the negative electrode plate 12 of the electrode body 14.

[0027] A negative electrode collector plate 40, which will be described in detail later, is provided below the electrode body 14. On the lower side of the axial direction P of the negative electrode plate 12, there is a negative electrode core material exposure portion (not shown) protruding from the negative electrode core material where no negative electrode mixture layer is provided. The negative electrode core material exposure portion is formed from the end of the winding start side of the long side direction (circumferential direction R) of the long strip of negative electrode plate 12 to the end of the winding end side. The negative electrode core material exposure portion is joined to the negative electrode collector plate 40, so that the negative electrode plate 12 is electrically connected to the negative electrode collector plate 40. In addition, the negative electrode collector plate 40 is joined to the inner surface of the bottom 20B of the outer can 20, so that the negative electrode collector plate 40 is electrically connected to the outer can 20.

[0028] The outer can 20 is a metal container with a bottomed cylindrical shape, open at the upper end in the axial direction P. The outer can 20 is typically made of a metal primarily composed of iron, but can also be made of a metal primarily composed of aluminum, etc., when connected to the positive electrode plate 11. The outer can 20 includes a cylindrical barrel 20A, a bottom 20B that appears circular when viewed from above, an annular shoulder 20C formed along the circumferential direction R of the outer can 20 at the open end of the barrel 20A, and a groove 20D formed along the circumferential direction R of the barrel 20A. The outer can 20 is also provided with a negative electrode cap 21, which serves as a second external terminal (negative external terminal).

[0029] The groove 20D is formed near the opening of the outer can 20, spaced a predetermined length apart from the shoulder 20C. The groove 20D is formed by partially extending the cylindrical portion 20A toward the inside of the outer can 20. For example, the cylindrical portion 20A is spun from the outside to form the groove 20D. Furthermore, the outer can 20 is reduced in diameter at the location where the groove 20D is formed, forming a thin linear groove on the outer circumference of the cylindrical portion 20A. Preferably, the groove 20D has a substantially U-shaped cross-section and is formed in an annular shape along the entire length of the cylindrical portion 20A in the circumferential direction R.

[0030] The negative electrode cap 21 is electrically connected to the negative electrode plate 12 via the outer can 20 and functions as a negative electrode external terminal. The negative electrode cap 21 is formed into an annular shape with an opening at the center in the radial direction D. The negative electrode cap 21 is welded to the shoulder 20C of the outer can 20 and is electrically connected to the outer can 20.

[0031] The sealing body 30 is generally disc-shaped and comprises a positive electrode cap 31, a current collector plate 32, a gasket 33, and an insulating member 34. The sealing body 30 is positioned within the groove 20D of the outer can 20 and secured to the upper end of the outer can 20. More specifically, the shoulder 20C of the outer can 20 is bent inward in the radial direction D and crimped onto the sealing body 30. The sealing body 30 is secured to the upper end of the outer can 20 via the shoulder 20C and groove 20D of the outer can 20, thereby sealing the opening of the outer can 20.

[0032] The positive electrode cap 31 is electrically connected to the positive electrode plate 11 via the positive electrode lead 15 and the current collector plate 32, functioning as a positive external terminal. The positive electrode cap 31 is a disc-shaped metal member having a raised portion 31A protruding from its center in the radial direction D toward the outside of the energy storage device 10, and a flange portion 31B formed around the raised portion 31A. The positive electrode cap 31 is positioned on the upper surface of the sealing body 30 and is exposed to the exterior of the outer can 20, forming the top surface of the energy storage device 10. The positive electrode tab, etc., of the current collector component of the energy storage module, is welded to the raised portion 31A.

[0033] The current collector plate 32 is electrically connected to the positive electrode plate 11 via the positive electrode lead 15 and functions as a positive electrode current collector plate. The current collector plate 32 is a metal member having a diameter approximately the same as that of the positive electrode cap 31. The current collector plate 32 is formed into a ring shape with an opening at the center in the radial direction D. The current collector plate 32 is positioned closer to the electrode body 14 than the positive electrode cap 31. The current collector plate 32 is welded to the positive electrode cap 31, for example, at a position closer to the outer periphery of the positive electrode cap 31 than the center in the radial direction D of the positive electrode cap 31.

[0034] The gasket 33 is a rubber or resin member that prevents contact between the positive electrode cap 31 and the current collector plate 32 and the outer can 20, thereby ensuring electrical insulation between the outer can 20 and the sealing body 30. Furthermore, the gasket 33 seals the gap between the outer can 20 and the sealing body 30, thereby sealing the interior of the power storage device 10. The gasket 33 is disposed between the outer can 20 and the outer can 20, and the outer can 20. Along the outer periphery of the stacked structure, the gasket 33 covers the upper surface of the flange 31B of the positive electrode cap 31, the side surfaces of the positive electrode cap 31 and the current collector plate 32, and the lower surface of the current collector plate 32.

[0035] The insulating member 34 is a rubber or resin member that prevents contact between the positive electrode cap 31 and the negative electrode cap 21 and ensures electrical insulation between the positive electrode cap 31 and the negative electrode cap 21. The insulating member 34 is formed in an annular shape with an opening at the center in the radial direction D.

[0036] [Negative electrode collector plate]

[0037] use Figure 26 , a negative electrode current collector plate 40 is described as an example of an embodiment.

[0038] The negative electrode current collector plate 40 as a current collector is joined to the exposed portion of the negative electrode core material protruding from the lower side of the electrode body 14 in the axial direction P. In addition, the negative electrode current collector plate 40 is joined to the bottom 20B of the outer can 20, so that the outer can 20 functions as a negative electrode external terminal (see Figure 1 ). The negative electrode current collector plate 40 can improve reliability, which will be described in detail later.

[0039] like Figure 2 As shown, the negative electrode current collector plate 40 is preferably made of a metal, such as copper, a copper alloy, nickel or a nickel alloy, or a material formed by nickel plating an iron material. The negative electrode current collector plate 40 is disposed on the lower side of the electrode body 14 in the axial direction P and is housed in the outer can 20 together with the electrode body 14. In other words, the negative electrode current collector plate 40 is positioned between the electrode body 14 and the bottom 20B of the outer can 20.

[0040] like Figure 3 As shown, the negative electrode current collector plate 40 includes a central portion 41 and an extension portion 43, each described in detail below. The central portion 41 is located at the center in the radial direction D (the stacking direction of the positive electrode plates 11 and the negative electrode plates 12), and the extension portion 43 extends from the central portion 41 along the radial direction D. The central portion 41 includes a can bottom joint portion 42 surrounded by a circular groove. The can bottom joint portion 42 is joined to the bottom portion 20B of the outer can 20 by welding.

[0041] The plurality of extension portions 43 extend from the central portion 41 along the radial direction D. The plurality of extension portions 43 are arranged at intervals in the circumferential direction R. Figure 3 In the example shown, four extension portions 43 are radially arranged at 90° intervals from the central portion 41. Furthermore, in this embodiment, the extension portions 43 extend in four directions, but may extend in one, two, three, or five or more directions.

[0042] The extension portion 43 includes a joining portion 44 and an edge portion 45, each of which will be described in detail later. The joining portion 44 extends in the radial direction D and has a flat plate shape. The edge portion 45 is formed at both ends of the joining portion 44 in the circumferential direction R. The edge portion 45 may be provided at both ends of a single joining portion 44, or may be formed only at one end in the circumferential direction.

[0043] The joint 44 is welded to the exposed portion of the negative electrode core material. More specifically, the exposed portion of the negative electrode core material is welded to the upper surface of the joint 44 in the axial direction P. The joint 44 extends along the radial direction D and forms a portion corresponding to the bottom of a concave shape when viewed from the radial direction D. A force-applying portion 46, described in detail below, is formed at the outer end of the joint 44 in the radial direction D.

[0044] The edge 45 is the portion that contacts the exposed portion of the negative electrode core material. The edge 45 can be provided at both ends of the joint 44 in the circumferential direction R, or it can be formed only at one end in the circumferential direction R. While the edge 45 of this embodiment is formed substantially horizontally, it can also be formed obliquely relative to the horizontal direction.

[0045] like Figure 4 As shown, as described above, the force-applying portion 46 is formed at the outer end of the joint 44 in the radial direction D. The force-applying portion 46 applies force to the inner side of the outer can 20 when the negative electrode current collector plate 40 is housed within the outer can 20. The force-applying portion 46 enables centering of the negative electrode current collector plate 40 and the outer can 20, as will be described in detail later.

[0046] The force-applying portion 46 extends outward from the end portion on the outside of the radial direction D of the joint 44 and is bent toward the upper side of the axial direction P in such a manner as to form a curved surface opposite to the inner circumferential surface of the outer can 20. Thus, the force-applying portion 46 can be formed only by bending. That is, there is no need to additionally provide a force-applying member such as a spring member, and the force-applying member can be formed with a simple structure. In addition, since the bent portion is in contact with the inside of the outer can 20, metal powder dust can be suppressed when the inside of the outer can 20 contacts the force-applying portion 46. In addition, the radial dimension of the negative electrode collector plate 40 including the force-applying portion 46 is larger than the radial dimension (or stacking direction) of the electrode body 14.

[0047] The biasing portion 46 is bent upward in the axial direction P while biasing the outer can 20 inward and is accommodated in the concave shape of the extension portion 43 formed with the joint 44 as the bottom.

[0048] In addition, in this embodiment, the structure is set as having four extension portions 43 with force applying portions 46 formed thereon, but the present invention is not limited to this. It is sufficient as long as the structure has at least three extension portions 43 with force applying portions 46 formed thereon. In addition, a structure may have three or more extension portions 43, with force applying portions 46 formed on at least three of the extension portions 43.

[0049] use Figure 5A and Figure 5B The effects of the negative electrode current collector plate 40 will be described in comparison with the conventional negative electrode current collector plate 140 .

[0050] like Figure 5AAs shown, when the negative electrode collector plate 140 and the outer can 120 are welded together, if the center of the negative electrode collector plate 140 is inconsistent with the center of the outer can 20 when viewed from the axial direction P (hereinafter referred to as the negative electrode collector plate 140 and the outer can 120 are not centered), then when the positive electrode plate and the negative electrode plate expand during charging and discharging, the surface pressure inside the electrode body 114 will become unbalanced, resulting in uneven reaction, which may reduce the cycle life or cause a short circuit.

[0051] Furthermore, if the negative electrode current collector plate 140 and the outer can 120 are not centered, the expansion force of the electrode body 114 may cause the electrode body 114 to come into contact with the outer can 120. Furthermore, the expansion force of the electrode body 114 may generate stress at the welded joint between the negative electrode current collector plate 140 and the outer can 120. Furthermore, stress may also be generated at the welded joint between the negative electrode current collector plate 140 and the electrode body 114.

[0052] like Figure 5B As shown, by providing a force-applying portion 46 on the extension portion 43 of the negative electrode current collector plate 40 , when the negative electrode current collector plate 40 is housed inside the outer can 20 , the force-applying portion 46 can apply force to the inner side of the outer can 20 to center the negative electrode current collector plate 40 and the outer can 20 .

[0053] This structure prevents the surface pressure within the electrode body 14 from becoming unbalanced when the positive and negative electrode plates 11 and 12 expand during charge and discharge of the electricity storage device 10. Furthermore, the expansion force of the electrode body 14 prevents contact between the electrode body 14 and the outer can 20, and prevents stress from being generated at the welded joint between the negative electrode current collector plate 40 and the outer can 20, or at the welded joint between the negative electrode current collector plate 40 and the electrode body 14. This improves the reliability of the electricity storage device 10.

[0054] Furthermore, the present invention is not limited to the above-described embodiment and its modifications, and various modifications and improvements can be made within the scope of the claims of this application. While the structure of the current collector plate used in the power storage device of the present invention has been described above as a negative electrode current collector plate, the current collector plate of the present invention may also be a positive electrode current collector plate.

[0055] Description of Reference Numerals

[0056] 10. Energy storage device; 11. Positive electrode plate (first electrode plate); 12. Negative electrode plate (second electrode plate); 13. Spacer; 14. Electrode body; 15. Positive electrode lead; 16. Upper insulating plate; 20. Outer can; 20A. Barrel; 20B. Bottom; 20C. Shoulder; 20D. Groove; 21. Negative electrode cover; 30. Sealing body; 31. Positive electrode cover; 31A. Raised portion; 31B. Flange; 32. Collector plate; 33. Gasket; 34. Insulating member; 40. Negative collector plate; 41. Central portion; 43. Extended portion; 44. Joint; 45. Edge; 46. Force-applying portion; 114. Electrode body; 120. Outer can; 140. Negative collector plate.

Claims

1. A power storage device comprising: an electrode body formed by laminating a first electrode plate and a second electrode plate with a separator interposed therebetween; a current collector plate disposed on one axial end side of the electrode body; and an outer can housing the electrode body and the current collector plate, wherein: The current collector plate has an extension portion extending along a stacking direction of the first electrode plate and the second electrode plate. A biasing portion for biasing the inner side of the outer can is provided at an end portion on the outer peripheral side of the extending portion.

2. The power storage device according to claim 1, wherein The first electrode plate and the second electrode plate are wound with the separator interposed therebetween. The outer tank is cylindrical in shape. The urging portion is provided at a radially outer end portion of the extending portion.

3. The power storage device according to claim 1 or 2, wherein This power storage device includes at least three extending portions provided with the biasing portions.

4. The power storage device according to any one of claims 1 to 3, wherein The urging portion extends radially outward from the extending portion and has a curved surface formed at a tip thereof.

5. The power storage device according to claim 4, wherein The extension portion has a joint portion extending in the radial direction and formed as a portion of a bottom portion having a concave shape when viewed from the radial direction. The urging portion is accommodated in the concave shape when applying a force.

Images