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 the lower end side in the axial direction (P) of the electrode body (14), the negative electrode collector plate (40) having a negative electrode joining section (44) extending along the radial direction (D) of the electrode body (14) and joined to the negative electrode plate (12), the negative electrode joining section (44) being inclined when viewed from the circumferential direction (R).

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] In the above-mentioned end face current collection structure, the joining process between the current collector plate and the electrode plate is complicated, which may reduce the productivity in the manufacturing process of the power storage device.

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

[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; and a current collector plate arranged on one axial end side of the electrode body, characterized in that the current collector plate has a joint portion extending along the stacking direction of the first electrode plate and the second electrode plate and joined to the second electrode plate, and the joint portion is inclined in a direction intersecting the stacking direction.

[0009] According to the power storage device of the present invention, productivity 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 This is a perspective view of the connection between the negative electrode current collector plate and the electrode body as viewed from below.

[0012] Figure 3 It is a perspective view showing a negative electrode current collector plate as an example of an embodiment, as viewed from below.

[0013] Figure 4 yes Figure 3 AA cross-sectional view.

[0014] Figure 5 It is a cross-sectional view taken along line AA of a negative electrode current collector plate as another example of the embodiment.

[0015] Figure 6A This is a schematic diagram showing reflected light during welding of a conventional negative electrode current collector plate.

[0016] Figure 6B This is a schematic diagram showing reflected light during welding of the negative electrode current collector plate of the present invention. DETAILED DESCRIPTION

[0017] 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.

[0018] [Electricity Storage Device]

[0019] use Figure 1 A power storage device 10 as an example of an embodiment will be described.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] The positive electrode plate 11, the negative electrode plate 12 and the separator 13 are all strip-shaped elongated 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 they protrude to opposite sides in the axial direction P (the height direction of the storage device). 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 and a plurality of negative electrode plates alternately stacked.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] A negative electrode current collector plate 40, which will be described in detail later, is provided below the electrode body 14. A negative electrode core material exposed portion 18 (see FIG. 1 ) protrudes from the lower side of the negative electrode plate 12 in the axial direction P, where the negative electrode core material is not provided with a negative electrode mixture layer. Figure 2 The exposed negative electrode core material portion 18 extends from the end of the long strip of negative electrode plate 12 at the start of winding in the longitudinal direction (circumferential direction R) to the end of winding. The exposed negative electrode core material portion 18 is bonded to the negative electrode current collector plate 40, thereby electrically connecting the negative electrode plate 12 to the negative electrode current collector plate 40. Furthermore, the negative electrode current collector plate 40 is bonded to the inner surface of the bottom portion 20B of the outer can 20, thereby electrically connecting the negative electrode current collector plate 40 to the outer can 20.

[0029] 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).

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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 electrode 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. A positive electrode tab and the like are welded to the raised portion 31A.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] [Negative electrode collector plate]

[0038] use Figure 2 6 , a negative electrode current collector plate 40 is described as an example of an embodiment.

[0039] like Figure 2 As shown, a negative electrode current collector plate 40, serving as a current collector, is joined to the exposed negative electrode core material portion 18 protruding from the lower side in the axial direction P of the electrode body 14. Furthermore, the negative electrode current collector plate 40 is joined to the bottom 20B of the outer can 20, allowing the outer can 20 to function as a negative electrode external terminal. The negative electrode current collector plate 40 can improve the productivity of the electricity storage device 10, as will be described in detail later.

[0040] The negative electrode current collector plate 40 is preferably made of metal, such as copper, copper alloy, nickel or nickel alloy, or a material obtained by plating nickel on the surface of 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 disposed between the electrode body 14 and the bottom 20B of the outer can 20 (see FIG. 2 ). Figure 1 ).

[0041] like Figure 2 and Figure 3 As shown, the negative electrode current collector plate 40 includes a central portion 41 and an extension portion 43, each of which will be described in detail later. The central portion 41 is provided 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 is joined to the bottom portion 20B of the outer can 20 by welding.

[0042] 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.

[0043] like Figures 2 to 4 As shown, the extension portion 43 includes a joint portion 44 extending along the radial direction D and edge portions 45 formed at both ends of the joint portion 44 in the circumferential direction R. The joint portion 44 is welded to the exposed negative electrode core member 18. More specifically, the exposed negative electrode core member 18 is welded to the upper surface of the joint portion 44 in the axial direction P. The joint portion 44 extends along the radial direction D and is formed to correspond to the bottom edge of the concave shape when viewed from the radial direction D. In other words, the joint portion 44 is formed on the bottom surface of the concave shape.

[0044] The joint 44 is inclined when viewed from the radial direction D. In other words, the joint 44 extends obliquely along a direction intersecting the radial direction D (for example, a direction orthogonal to the radial direction D). The inclination angle of the joint 44 when viewed from the radial direction D is greater than 3° and less than 10° relative to the horizontal plane, preferably greater than 5° and less than 10°. The inclination angle of the joint 44 is preferably the same along the radial direction D. In addition, the inclination direction of the joint 44 (when viewed from the outside of the radial direction D, the right side is the upper side or the left side is the upper side) is not particularly limited. Compared with the structure inclined along the radial direction D, the structure inclined along the circumferential direction R intersecting the radial direction D can suppress the distance between the light source and the irradiated surface from being different in the radial direction when the light source of the laser is moved along the radial direction D and irradiated, and can suppress the degree of melting of the joint from becoming uneven.

[0045] The edge 45 is a portion that contacts the negative electrode core member exposed portion 18. The edge 45 may be provided at both ends of the joint 44 in the circumferential direction R, or may be formed only at one end in the circumferential direction R. The edge 45 of this embodiment is formed substantially horizontally, but may also be formed obliquely.

[0046] like Figure 5 As shown, the joint 44 may be formed as a portion corresponding to one side of a V-shape when viewed from the radial direction D. In this case, when viewed from the radial direction D, one inclined surface corresponding to the joint 44 is preferably formed longer than the other inclined surface. By configuring in this way, the inclined surface can be irradiated with a laser more reliably than, for example, a negative electrode current collector plate in which the connection position of the inclined surface is located at the center of the recess. In this case, the joint serving as the inclined surface is preferably provided with a solidified portion formed by irradiating the laser between the two ends in the circumferential direction R. As described above, the joint 44 is inclined when viewed from the radial direction D. The inclination angle of the joint 44 as viewed from the radial direction D is greater than 3° and less than 10° relative to the horizontal plane, preferably greater than 5° and less than 10°.

[0047] use Figure 6A and Figure 6B The negative electrode current collector plate 40 will be described by comparison with the conventional negative electrode current collector plate 140 .

[0048] In the end-face current collection structure, a long negative electrode current collector plate 140 is welded to an exposed negative electrode core material portion 118, which projects downward and is bent from the electrode body 114, along the radial direction D of the electrode body 114. During the joining process for the end-face current collection structure, the negative electrode current collector plate 140 is irradiated with a laser or the like from the lower side, thereby fusing and joining the negative electrode current collector plate 140 and the exposed negative electrode core material portion 118, which is in close contact with the upper surface of the negative electrode current collector plate.

[0049] The negative electrode collector plate 140 can be made of copper or aluminum, which is a highly reflective material. In addition, in the laser oscillator L, if the reflected light caused by the laser irradiation returns to the inside of the laser oscillator L, the laser irradiation becomes unstable, which may cause a failure of the laser oscillator L. Therefore, in the laser oscillator L, when the reflected light toward the laser oscillator L is detected, control is performed to stop the laser irradiation. Therefore, if Figure 6A As shown, when laser welding the joint 144 of the negative electrode current collector plate 140 and the negative electrode core member exposed portion 118 , the amount of light reflected toward the laser oscillator L is large, so the laser oscillator L may detect the reflected light and stop.

[0050] As a countermeasure to the above problem, for example, a method of tilting the laser oscillator for laser irradiation is also considered. However, this requires the use of a robot supporting the laser oscillator, an XY stage, etc. to track the laser incident angle, which slows down production speed and thus risks reducing productivity.

[0051] In the negative electrode current collector plate 40 of this embodiment, since the joint portion 44 is inclined when viewed from the radial direction D (inclined in a direction intersecting the radial direction D), it is possible to suppress reflected light returning to the laser oscillator L. More specifically, when laser welding the negative electrode current collector plate 40 and the negative electrode core material exposed portion 18, since the joint portion 44 is inclined when viewed from the radial direction D, the laser irradiation surface is inclined, which can suppress reflected light heading toward the laser oscillator L. This can prevent the laser oscillator L from being stopped by the return of reflected light.

[0052] Furthermore, in the negative electrode current collector plate 40 of this embodiment, since the joint portion 44 is inclined when viewed from the radial direction D, the length of the joint portion 44 in the circumferential direction R is longer than when the joint portion 44 is horizontal when viewed from the radial direction D. This increases the weld width between the negative electrode current collector plate 40 and the electrode body 14.

[0053] Furthermore, in the negative electrode current collector plate 40 of this embodiment, since the joint 44 is inclined when viewed from the radial direction D, the deepest portion of the joint 44 is more deeply embedded in the exposed negative electrode core material portion 18 than when the joint 44 is horizontal when viewed from the radial direction D. This improves the bond strength between the negative electrode current collector plate 40 and the electrode body 14. Furthermore, when the negative electrode current collector plate 40 has multiple joints 44, the inclination direction of the inclined surfaces is preferably the same in the circumferential direction. This structure can more reliably limit displacement in the winding direction that occurs during charge and discharge of the wound electrode body 14.

[0054] In addition, the present invention is not limited to the above-mentioned embodiment and its modified examples, and it is self-evident that various changes and improvements can be made within the scope of the matters described in the claims of this application. Above, the structure of the collector plate used in the power storage device of the present invention is described as a negative electrode collector plate, but the collector plate of the present invention can also be a positive electrode collector plate. In addition, the collector plate of the present invention can also be joined to the sealing body instead of the outer can. Alternatively, the collector plate of the present invention can also be arranged on the opening side of the outer can and serve as a sealing body.

[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; 18. Negative electrode core material exposed portion; 20. Outer can; 20A. Cylinder; 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 electrode collector plate; 41. Central portion; 43. Extended portion; 44. Joint; 45. Edge; 118. Negative electrode core material exposed portion; 140. Negative electrode collector plate; 144. Joint.

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; and a current collector plate disposed on one end side of the electrode body in an axial direction, wherein: The current collector plate has a joint portion extending along a stacking direction of the first electrode plate and the second electrode plate and joined to the second electrode plate. The joining portion is inclined in a direction intersecting the stacking direction.

2. The power storage device according to claim 1, wherein The joining portion is formed into a concave bottom surface when viewed from the stacking direction.

3. The power storage device according to claim 2, wherein A solidified portion is formed between both ends of the joint portion in an inclined direction of the joint portion.

4. The power storage device according to claim 1, wherein When viewed from the stacking direction, the joining portion is one side of a V-shape.

5. The power storage device according to any one of claims 1 to 4, wherein The inclination angle of the joining portion is greater than or equal to 5° and less than or equal to 10°.

6. The power storage device according to any one of claims 1 to 5, wherein The joining portion is joined by welding using laser irradiation.

7. The power storage device according to any one of claims 1 to 6, wherein The first electrode plate and the second electrode plate are wound with the separator interposed therebetween. The electrode body is cylindrical in shape, The joining portion extends in a radial direction of the electrode body.

8. The power storage device according to any one of claims 1 to 7, wherein The current collector plate has a plurality of the joints. The plurality of joining portions are inclined in the same direction in the circumferential direction of the electrode body.

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