Electricity storage device

Abstract

A power storage device is provided with: an electrode body (10); an outer can (20) that has a cylindrical part (21) and an opening part formed at one end of the cylindrical part (21), and that houses the electrode body (10); and a sealing member (24) that closes the opening, in which an annular groove (23) that is recessed inward is formed in the opening of the cylindrical section (21), a bent section (210) that is bent inward is formed at the peripheral edge of the opening, and the peripheral edge of the sealing member (24) is sandwiched from both sides by the groove (23) and the bent section (210). The wall thickness of a bent portion which transitions from a peripheral edge portion of the outer can (20) extending in the axial direction to a portion of the bent portion (210) extending inward is thicker than at least a portion of the bent portion (210).

Description

Technical Field

[0001] The present disclosure relates to a power storage device such as a secondary battery. Background Art

[0002] Among power storage devices such as lithium ion batteries, widely used ones include a bottomed cylindrical outer can that houses an electrode assembly responsible for power generation and a sealing member that seals the opening of the outer can.

[0003] Such power storage devices require high airtightness to prevent moisture from entering the outer can, etc. Therefore, the contact area between the outer can and the sealing member is sealed by crimping the peripheral edge of the sealing member to the upper portion of the outer can.

[0004] Specifically, a circular groove is formed inwardly around the upper end of the outer can, and the groove surrounds the outer can. The outer can is then bent inwardly with the peripheral edge of the sealing member placed on top of the groove. The groove and the bent edge secure the peripheral edge of the sealing member by clamping the outer can.

[0005] Furthermore, in Patent Document 1, a notch is formed in advance at the upper end of the outer can to prevent the inner tip from wrinkling when the upper end is bent inward.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-261083 Summary of the Invention

[0009] The above-described power storage device improves sealing reliability. However, as the capacity and high output of power storage devices increase, further improvements in their reliability are desired. Therefore, the present disclosure aims to provide a power storage device with excellent reliability.

[0010] The electricity storage device of the present invention includes: an electrode body; an outer can having a cylindrical portion and an opening formed at one end of the cylindrical portion, the outer can accommodating the electrode body; and a sealing member that seals the opening, wherein an annular groove recessed inward is formed in the opening of the cylindrical portion, and a bent portion bent inward is formed at the peripheral edge of the opening, the peripheral portion of the sealing member is clamped from both sides by the groove and the bent portion, and the wall thickness of the bent portion transitioning from the axially extending peripheral portion of the outer can to the inwardly extending portion of the bent portion is thicker than at least a portion of the bent portion.

[0011] With the power storage device of the present disclosure, reliability is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a cross-sectional view of a battery 1 as an example of the power storage device according to the embodiment.

[0013] Figure 2 It is a diagram illustrating a wound state of the electrode assembly 10 .

[0014] Figure 3 It is a longitudinal sectional view of an example of a bent portion 210 formed by bending the upper end of the exterior can 20 inward.

[0015] Figure 4 2 is a diagram showing the structure of the bent portion 210 . DETAILED DESCRIPTION

[0016] Hereinafter, an example of an embodiment of the power storage device of the present disclosure will be described in detail with reference to the drawings. In addition, the present disclosure includes a configuration in which a plurality of embodiments and modifications described below are selectively combined.

[0017] "Overall structure"

[0018] Figure 1 1 is a cross-sectional view of a battery 1 as an example of an electrical storage device according to an embodiment. Note that electrical storage devices also include capacitors and the like.

[0019] like Figure 1 As shown, the battery 1 includes an electrode body 10 and an outer can 20 for storing the electrode body 10. The outer can 20 includes a barrel 21 and a bottom 22 for sealing one end of the barrel 21. An opening is formed at the other end of the barrel 21, and the opening is sealed by a sealing member 24. In addition, an electrolyte is stored in the outer can 20 together with the electrode body 10. The electrolyte can be an aqueous electrolyte, but a non-aqueous electrolyte is used in this embodiment. In addition, a solid electrolyte can also be used instead of the electrolyte. As the solid electrolyte, for example, a solid or gel-like polymer electrolyte, an inorganic solid electrolyte, etc. are used.

[0020] In the height direction, an annular groove 23 is provided on the opening side of the cylindrical portion 21, projecting radially inward of the battery (or outer can). A sealing member 24 is supported by the groove 23 and seals the opening of the outer can 20. For convenience, the battery 1 side facing the sealing member 24 is considered to be at the top, and the side facing the bottom 22 of the outer can 20 is considered to be at the bottom. Alternatively, the outer can used in the power storage device of the present disclosure may be open at both ends in the height direction, with each opening sealed by a sealing member.

[0021] Battery 1 also includes a plurality of electrode leads extending from various locations of electrode body 10 toward sealing member 24 and directly connecting the first electrode constituting electrode body 10 to current collector plate 26 of sealing member 24. Furthermore, an upper insulating plate 34, for example, is disposed between electrode body 10 and sealing member 24.

[0022] The electrode body 10 is a wound electrode body formed by winding a first electrode and a second electrode with a separator interposed therebetween. In this embodiment, the first electrode is a positive electrode, the second electrode is a negative electrode, and the electrode lead is a positive electrode lead 19. As described later, a plurality of positive electrode leads 19 are arranged at predetermined intervals in the longitudinal direction of the positive electrode and extend upward from the upper portion of the positive electrode.

[0023] The positive electrode lead 19 electrically connects the positive electrode to the metal component of the sealing member 24. Furthermore, the negative electrode is electrically connected to the outer can 20 by, for example, contacting the outer can 20 with a protruding portion of its core material via a negative electrode current collector plate. Thus, the sealing member 24 functions as the positive electrode terminal, and the outer can 20 functions as the negative electrode terminal. The upper insulating plate 34 prevents the positive electrode and the positive electrode lead 19 from contacting the outer can 20, and also prevents the positive electrode lead 19 from contacting the negative electrode of the electrode assembly 10. Alternatively, the negative electrode may be electrically connected to the bottom of the outer can via a lead.

[0024] Figure 2 : is a diagram illustrating the winding state of the electrode body 10. The electrode body 10 includes a positive electrode 11, a negative electrode 12, and a separator 13 between the positive electrode 11 and the negative electrode 12, all of which are strip-shaped long strips, which are spirally wound and alternately stacked in the radial direction of the electrode body 10. The positive electrode 11 and the negative electrode 12 each have a composite layer on their respective surfaces. Usually, in order to prevent the precipitation of lithium, the composite material layer of the negative electrode 12 is formed to be one size larger than the composite material layer of the positive electrode 11. That is, the composite material layer of the negative electrode 12 is formed longer than the composite material layer of the positive electrode 11 in the long side direction and the width direction (short side direction). In Figure 2 In the example shown, the inner starting end of the positive electrode 11 is located outside the starting end of the negative electrode 12, and only the negative electrode 12 and separator 13 are wound around the center of the electrode body 10. Separator 13 is formed to be at least one size larger than the positive electrode 11, and two separators are arranged to sandwich the positive electrode 11. Thus, separator 13 is interposed between the positive electrode 11 and the negative electrode 12 during winding.

[0025] The positive electrode 11 has a strip-shaped positive electrode core and a positive electrode composite material layer formed on at least one surface of the core. For the positive electrode core, a foil of a metal such as aluminum or aluminum alloy that is stable within the potential range of the positive electrode, a film in which the metal is arranged on the surface, etc. can be used. Preferably, the positive electrode composite material layer comprises a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride, and the positive electrode composite material layer is formed on both surfaces of the positive electrode core. For the positive electrode active material, for example, a lithium transition metal composite oxide is used. The positive electrode lead 19 is connected to the positive electrode, but is preferably directly joined to the positive electrode core by welding or the like.

[0026] The negative electrode 12 has a strip-shaped negative electrode core and a negative electrode composite material layer formed on at least one surface of the core. For the negative electrode core, a foil of a metal such as copper or copper alloy that is stable within the potential range of the negative electrode, a film in which the metal is arranged on the surface, etc. can be used. Preferably, the negative electrode composite material layer contains a negative electrode active material and a binder such as styrene-butadiene rubber (SBR), and the negative electrode composite material layer is formed on both surfaces of the negative electrode core. For the negative electrode active material, for example, graphite, a silicon-containing compound, etc. are used. In addition, a tongue-shaped negative electrode lead can also be directly joined to the negative electrode core and to the collector plate by welding or the like.

[0027] The non-aqueous electrolyte contained in the outer can 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.

[0028] Return to Figure 1 The outer can 20 is a metal container with a bottomed cylindrical shape and an opening at its upper axial end. It has a cylindrical barrel 21 and a bottom 22 that is circular when viewed from above. The outer can 20 is typically made of a metal primarily composed of iron. However, when the outer can 20 is electrically connected to the positive electrode, the outer can 20 may also be made of a metal primarily composed of aluminum or the like. Furthermore, the outer can 20 has a groove 23 formed along the circumference of the barrel 21. The groove 23 is formed near the opening of the outer can 20 at a position spaced apart from the edge of the opening (the upper end of the outer can 20) by a predetermined length, below the edge of the opening (the upper end of the outer can 20). The predetermined length is, for example, 1% to 20% of the axial length of the outer can 20.

[0029] In this embodiment, a safety valve mechanism is provided at the bottom 22 of the outer can 20 to activate when an abnormality occurs in the battery 1. For example, a thin-walled portion is formed at the bottom 22. When an abnormality occurs in the battery 1 and the internal pressure rises, this thin-walled portion ruptures first, forming a gas discharge outlet at the bottom 22.

[0030] The groove 23 is a portion of the barrel 21 that extends toward the inside of the outer can 20. For example, the barrel 21 is spun from the outside to form the groove 23. Furthermore, the outer can 20 is reduced in diameter at the location where the groove 23 is formed, forming a thin linear groove on the outer circumference of the barrel 21. Preferably, the groove 23 has a substantially U-shaped cross-section and is formed in an annular shape along the entire circumferential length of the barrel 21. Preferably, the groove 23 is formed by machining the barrel 21 after the electrode body 10 is housed in the outer can 20.

[0031] The inner diameter of the outer can 20 at the location where the groove 23 is formed is, for example, 80% to 99% of the maximum inner diameter of the outer can 20. The length of the groove 23 along the radial direction of the outer can 20 is, for example, 0.5 mm to 2.0 mm. Because the diameter of the electrode body 10 is approximately the same as the maximum inner diameter of the outer can 20, the electrode body 10 and the groove 23 overlap in the vertical direction of the battery 1. In this embodiment, the lower end of the positive electrode lead 19 is connected to the upper end of the positive electrode at multiple locations, and the other end of the positive electrode lead 19 is connected to the lid 25 via the current collector plate 26.

[0032] The sealing member 24 includes, for example, a cover 25, a current collector plate 26, and an electrically insulating gasket 33, and is generally disc-shaped. The sealing member 24 is disposed on the groove 23 of the outer can 20 and fixed to the opening of the outer can 20. The upper end of the opening is bent inward and is bent relative to the sealing member 24 via the gasket 33 to form a bent portion. In other words, the sealing member 24 is fixed to the upper end of the outer can 20 via the groove 23 and the bent portion of the outer can 20, thereby sealing the opening of the outer can 20. The bent portion is formed in an annular shape along the circumference of the outer can 20 and, together with the groove 23, holds the sealing member 24. The sealing member 24 also includes a member such as an upper insulating plate 34 for covering the upper opening of the outer can 20. Furthermore, the sealing member 24 may also include a metal break plate or the like.

[0033] The cover 25 is a disc-shaped metal member that is exposed to the outside of the outer can 20 and forms the top surface of the battery 1. The cover 25 has a shape (raised portion) with the radial center portion protruding toward the outside of the battery 1. When the battery 1 is modularized to form a battery pack, wiring materials are connected to the cover 25. Therefore, the cover 25 functions as an external terminal of the battery 1 and is also called an external terminal or top cover. In this embodiment, the positive lead 19 is connected to the collector plate 26, and the cover 25 functions as a positive external terminal.

[0034] The collector plate 26 is a metal member having a diameter approximately the same as that of the cover 25 and is arranged at a position closer to the electrode body 10 than the cover 25. The collector plate 26 has an opening 26a in the radial center and is formed in an annular shape. The cover 25 and the collector plate 26 are welded together, and the collector plate 26 is welded, for example, to a position where the distance from the radial center of the cover 25 is greater than the distance from the outer periphery. The collector plate 26 is formed with an annular protrusion 26b, which will be described later, and the protrusion 26b serves as a welded portion to the cover 25. Since the positive lead 19 connected to the positive electrode of the electrode body 10 is connected to the collector plate 26 as described above, the collector plate 26 functions as a positive electrode collector plate. In addition, it is also possible that no positive electrode collector plate is provided and the positive electrode lead is directly joined to the cover.

[0035] A gasket 33 is provided around the outer periphery of the stack of the lid 25 and the current collector plate 26. The gasket 33 is an annular resin or rubber member that prevents contact between the lid 25 and the current collector plate 26 and the outer can 20, thereby ensuring electrical insulation between the outer can 20 and the sealing member 24. The gasket 33 covers the upper surface of the lid 25, the side surfaces of the lid 25 and the current collector plate 26, and the lower surface of the current collector plate 26 along the outer periphery of the stack. Furthermore, the gasket 33 seals the gap between the outer can 20 and the sealing member 24, thereby hermetically sealing the interior of the battery 1.

[0036] The gasket 33 is formed to cover most of the lower surface of the collector plate 26 and is interposed between the collector plate 26 and the upper insulating plate 34. An opening portion 33a is formed in the radial center portion of the gasket 33, which overlaps with the opening portion 26a of the collector plate 26 in the up and down directions. In addition, a through hole 33b may also be formed in the portion of the gasket 33 located below the collector plate 26. It is envisaged that electrolyte is stored on the upper surface area of ​​the gasket 33, but by providing the through hole 33b, the electrolyte can be efficiently returned to the electrode body 10 side. For example, a plurality of through holes 33b are formed along the circumference of the gasket 33. In addition, the gasket 33 has an inner extension portion 33c extending inward from the outer peripheral portion of the cover 25.

[0037] The upper end of the outer can 20 is bent (curved) inward to form a bent portion 210. This bent portion 210 can be used as a negative electrode external terminal.

[0038] "Structure of the bending portion 210"

[0039] Figure 3 This is a longitudinal (radial) cross-sectional view of an example of a bent portion 210 formed by bending the upper end of the outer can 20 inward. Thus, the bent portion 210 is formed by bending inward at the upper end of the axially (vertically) extending portion 211 of the cylindrical portion 21. This bent portion 210 is formed by spinning and crimping as described below.

[0040] The bent portion 210 includes a curved portion 212 that bends inward, an intermediate portion 213 that extends inward from the curved portion 212, and a top end portion 214 that serves as an inner end. Furthermore, the top end portion 214 is thicker than the thin-walled portion located radially outward from the top end portion. Furthermore, the top end portion 214 protrudes further toward the sealing member than the thin-walled portion in the height direction of the outer can. Furthermore, the curved portion 212 and the top end portion 214 serve as thick-walled portions. Furthermore, the intermediate portion 213 has a thin-walled portion 213-2 on the side close to the top end portion 214, a thick-walled portion 213-1 near the center of the intermediate portion 213, and a thin-walled portion 213-3 on the side close to the curved portion 212.

[0041] In addition, the sealing member side of the top of the bent portion 210 extends further inward to form an annular slope surface. With this shape, the top portion is formed thick, making it easy to suppress (get caught) the inner extension portion 33c of the gasket 33.

[0042] In this way, the bent portion 210 has a thick-walled top portion 214 and a thin-walled portion 213-2 near its inner side. By making the top portion 214 thicker, the pressing force on the gasket below it can be increased. This increased pressing force increases the reaction force of the inner extension 33c of the gasket 33, which can reliably seal the portion of the inner extension 33c of the gasket 33 located near the top portion 214. Furthermore, since the thin-walled portion 213-2 is formed radially outward of the outer can at the top portion 214, the upper surface of the bent portion 210 (the surface facing outward in the thickness direction of the bent portion) can be relatively flat even if the radial dimension of the bent portion is increased. This ensures a sufficient welding area when welding the negative terminal, etc., to the bent portion 210. Furthermore, a surface of the bent portion 210 facing the gasket 33 in a region radially inward of the thin portion 213 has an inclined surface radially inwardly approaching the gasket, and the thickness of this region increases toward the inner side.

[0043] Here, as shown in the accompanying drawings, when the thickness of the portion 211 corresponding to the upper portion of the cylindrical portion 21 (the portion excluding the bent portion and located above the groove portion) is set to W1, the thickness of the bent portion 212 is set to W2, the thickness of the thin-walled portion 213-3 near the middle portion 213 is set to W3, the thickness of the thick-walled portion 213-1 of the middle portion is set to W4, the thickness of the thin-walled portion 213-2 on the top side of the middle portion 213 is set to W5, and the thickness of the top portion is set to W6, the bent portion 210 can satisfy the condition of W5<W6. In addition, the bent portion 210 can further satisfy the condition of W5<W4. In addition, the bent portion can satisfy the condition of W3<W4 and can satisfy the condition of W3<W2. It can satisfy the condition of W1<W2. In addition, for the sloped surface of the top portion 214, when the thickness in the inclined direction is set to W7, it becomes W6<W7. Alternatively, W2>W4 may be set.

[0044] In addition, in Figure 3 Assuming the bending amount of the bent portion 210 is dimensioned as A, the tip portion 212 is located on the 0.5A to A side. Furthermore, the region between 0.9A and A is particularly defined as the tip portion. To improve the sealing performance between the bent portion 210 and the inner extension portion 33c, the thickness W6 or W7 of the tip portion may be increased by at least 120% relative to the minimum thickness W4 of the middle portion of the outer can 20, particularly within the range of 0.5A to 0.9A from the outer diameter.

[0045] In this example, the curved portion 212 is thicker than its surroundings. By making the curved portion 212 thicker, the mechanical strength of the curved portion 212 can be improved. This prevents the occurrence of through-cracks or suppresses through-cracks from reaching the interior, thereby preventing moisture intrusion and electrolyte leakage.

[0046] "Flanging"

[0047] Here, the thickness of the bent portion 210 varies in the radial direction. Such a thickness can be formed by a crimping device. Since the crimping device uses a motor to rotate the main body while performing the crimping process, this is called spinning crimping.

[0048] A motor is fixed to the frame of the bending device, and a rotating shaft of the motor extends in the vertical direction. A main body is fixed to the lower end of the rotating shaft, and the main body rotates in a horizontal plane.

[0049] Around the lower end of the main body, rollers are rotatably supported on a shaft extending in the horizontal direction. Furthermore, the frame can move up and down, and the bending device as a whole can move up and down. Furthermore, the shaft can extend in directions other than the horizontal direction.

[0050] The crimping device is positioned above the outer can 20, and the motor is rotated to rotate the main body. In this state, when the crimping device is moved downward, the roller contacts the upper end of the peripheral edge of the outer can 20. The roller, functioning as a crimping die, is rotatable and moves while passively rotating over the upper end of the outer can 20. Further lowering the crimping device in this state gradually bends the upper end of the barrel 21 inward.

[0051] By gradually lowering the roller, the upper end of the barrel 21 is bent inward to form a bent portion 210, which is pressed against the sealing member 24 together with the gasket 33. A notch is formed on the outer peripheral surface of the roller, which serves as the abutting surface against the barrel. The inner surface of the notch is in line contact with the barrel. The inner surface of the notch has: a first surface, which is opposite to the upper end of the barrel 21 in the height direction of the outer can; a second surface, which is separate from the outer peripheral surface of the barrel in the radial direction; and a curved R portion, which is located at the corner where one end of the first surface and one end of the second surface are connected. At this time, at the beginning stage of the bending edge where the top end abuts against the notch of the roller, the top end is thickened. When the top end is thickened, the R portion abutting against the top end is represented by an arc of a circle with a radius of less than 3 mm in the cross section of the roller obtained along the radial cutting line. Alternatively, the arc may be a circle with a radius of 2.5 mm or less, or a circle with a radius of 2.0 mm or less. Furthermore, in the final stage of bending, the curved portion in the middle is thickened. In this case, the curved portion can be thickened by utilizing the diameter of the rounded portion of the notch in the roller.

[0052] Bend length

[0053] exist Figure 4 FIG2 shows an example structure of the bent portion 210. In this example, the bent portion 210 is relatively short. However, the thickness of the bent portion 212 is greater than that of the other portions. This structure can also prevent the generation of through cracks in the bent portion or prevent through cracks from reaching the inside of the barrel.

[0054] In this embodiment, the bent portion is thickened during bending to suppress the occurrence of cracks, and the distance of crack propagation is increased to suppress crack penetration.

[0055] Description of Reference Numerals

[0056] 1. Battery; 10. Electrode body; 11. Positive electrode; 12. Negative electrode; 13. Spacer; 19. Positive electrode lead; 20. Outer can; 21. Cylinder; 22. Bottom; 23. Groove; 24. Sealing member; 25. Cover; 26. Collector plate; 26a. Opening; 26b. Protrusion; 33. Gasket; 34. Upper insulating plate; 210. Bend; 211. Part; 212. Bend; 213. Middle; 213-1. Thick-walled portion; 213-2. Thin-walled portion; 213-3. Thin-walled portion; 214. Top portion.

Claims

1. A power storage device, wherein: The power storage device comprises: Electrode body; an outer can having a cylindrical portion and an opening formed at one end of the cylindrical portion, the outer can housing the electrode assembly; and a sealing member that seals the opening, An annular groove recessed inward is formed at the opening of the cylinder. A bent portion bent inward is formed at the periphery of the opening. The peripheral portion of the sealing member is sandwiched from both sides by the groove portion and the bent portion. The wall thickness of the bent portion transitioning from the peripheral edge portion extending in the axial direction of the outer can to the inwardly extending portion of the bent portion is thicker than that of at least a portion of the bent portion.

2. The power storage device according to claim 1, wherein The curved portion has a thickness thicker than that of the peripheral wall portion.

3. The power storage device according to claim 1, wherein In the bent portion, the thickness of the tip portion located radially inward of the outer can is greater than that of at least the thin-walled portion located radially outward of the outer can. The top end portion protrudes toward the sealing member in a height direction of the outer can.

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