Gaskets and cylindrical batteries

Abstract

To provide a gasket capable of preventing short circuit at a lead part while improving workability during assembly, and a cylindrical battery.SOLUTION: A gasket 28 of a cylindrical battery in one embodiment includes: a cylindrical part 60; and a circular part 61 that extends from one end in an axial direction of a cylindrical part 60 to radially inward. A surface 67 opposite to the cylindrical part 60 side in the axial direction of circular part 61 is generally a flat surface. At the cylindrical part 60 side in the axial direction of the circular part 61, on both radial inner ends 69 of cylindrical part 60 and the circular part 61, protrusions 57 arranged at intervals in the radial direction and projecting in the axial direction are provided.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a gasket for a cylindrical battery and a cylindrical battery. [Background technology]

[0002] Conventionally, a cylindrical battery is described in Patent Document 1. This cylindrical battery includes an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, an electrolyte, a cylindrical outer can with a bottom that houses the electrode assembly and the electrolyte, a sealing body, and an annular gasket interposed between the outer can and the sealing body.

[0003] The outer can has a groove extending circumferentially on its outer surface, forming a protrusion on its inner periphery that protrudes radially inward. The open end of the outer can is bent inward and crimped to the sealing body, thereby sandwiching the sealing body between the protrusion and the crimped portion of the outer can via a gasket and fixing it to the outer can. A positive electrode lead extending from the positive electrode of the electrode assembly is connected to the bottom surface of the sealing body by welding. The gasket also has a cylindrical covering portion that extends axially and covers a portion of the protrusion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-320562 Summary of the Invention [Problem to be solved by the invention]

[0005] In conventional cylindrical batteries, the gasket covering part covers a portion of the radially inner side of the protrusion, reliably preventing a short circuit between the outer can, which serves as the negative electrode terminal, and the positive electrode lead. However, the following problem exists. Two methods for manufacturing cylindrical batteries are available: one involves assembling the gasket to a sealing body and then fitting it into the outer can; the other involves fitting the gasket into the outer can and then fitting the integrated structure of the electrode body and sealing body, which are integrated via the positive electrode lead, into the outer can. In the former method, the cylindrical covering part of the gasket covers the welding surface of the positive electrode lead on the sealing body, making it difficult to weld the positive electrode lead to the sealing body. Furthermore, the latter method requires two fitting steps during battery assembly, which reduces workability and increases the likelihood of short circuits between the sealing body and the outer can, which are not covered by the gasket.

[0006] Therefore, an object of the present disclosure is to provide a gasket and a cylindrical battery that can prevent short circuits between the lead portion that electrically connects the sealing body and the electrode body and the outer can, and that can also improve workability during assembly. [Means for solving the problem]

[0007] In order to solve the above problems, the gasket of the present disclosure is a gasket for a cylindrical battery, and comprises a cylindrical portion and an annular portion extending radially inward from one axial end of the cylindrical portion, the surface of the annular portion opposite the axial side of the cylindrical portion being a substantially flat surface, and the axial side of the annular portion has a protrusion that is disposed radially apart from both the cylindrical portion and the radial inner end of the annular portion and protrudes axially.

[0008] The requirement that "the surface of the annular portion opposite the cylindrical portion in the axial direction is a substantially flat surface" is also satisfied when the surface of the annular portion opposite the cylindrical portion in the axial direction has at least one of one or more minute recesses and one or more minute protrusions that do not hinder the flowability during battery assembly (do not reduce the workability of the battery assembly process). Furthermore, recesses with a depth of 1 mm or less are included in the above-mentioned minute recesses, and protrusions with a height of 1 mm or less are included in the above-mentioned minute protrusions. Therefore, the requirement that the surface of the annular portion opposite the cylindrical portion in the axial direction be a substantially flat surface is satisfied even if there are recesses with a depth of 1 mm or less or protrusions with a height of 1 mm or less on the surface.

[0009] Furthermore, the cylindrical battery according to the present disclosure is a cylindrical battery comprising: an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; an electrolyte; a bottomed cylindrical outer can that houses the electrode assembly and the electrolyte; a sealing body; and an annular gasket interposed between the outer can and the sealing body, wherein the outer can has an annular groove that extends circumferentially on its outer surface and protrudes radially inward, and a protrusion that protrudes radially inward from the annular groove, and the gasket includes a covering portion that covers at least a portion of the radially inner portion of the protrusion, and a supporting portion that supports the bottom surface of the outer can in the axial direction in the sealing body, wherein the covering portion is inclined so as to move radially inward as it approaches the bottom in the axial direction, and the supporting portion includes a protrusion whose tip contacts the sealing body. [Effects of the Invention]

[0010] The gasket and cylindrical battery of the present disclosure can prevent short circuits in the lead portions and improve workability during assembly. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is an axial cross-sectional view of a cylindrical battery according to one embodiment of the present disclosure. [Figure 2] FIG. 2 is a perspective view of the electrode body of the cylindrical battery. [Figure 3] FIG. 3 is an enlarged cross-sectional view of the periphery of the sealing body of the cylindrical battery. [Figure 4]FIG. 4 is an enlarged cross-sectional view of the periphery of the annular groove of the outer can in FIG. [Figure 5] FIG. 5 is a cross-sectional view of one side portion of the annular gasket located on one side of the central axis before being assembled into the outer can. [Figure 6] FIG. 6 is a diagram illustrating the operation of incorporating a gasket into an outer can. [Figure 7] FIG. 7 is a diagram illustrating the operation of incorporating a gasket into an outer can. [Figure 8] FIG. 8 is a cross-sectional view of the gasket of the reference example, corresponding to FIG. [Figure 9] FIG. 9 is a cross-sectional view of a modified gasket corresponding to FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of a cylindrical battery according to the present disclosure will be described in detail with reference to the drawings. The cylindrical battery according to the present disclosure may be a primary battery or a secondary battery. It may also be a battery using an aqueous electrolyte or a battery using a non-aqueous electrolyte. In the following, a non-aqueous electrolyte secondary battery (lithium ion battery) using a non-aqueous electrolyte will be exemplified as a cylindrical battery 10 according to one embodiment, but the cylindrical battery according to the present disclosure is not limited thereto.

[0013] When multiple embodiments and variations are included below, it is anticipated from the beginning that new embodiments can be constructed by appropriately combining their characteristic features. In the following embodiments, the same components are designated by the same reference numerals in the drawings, and redundant explanations are omitted. Furthermore, multiple drawings include schematic diagrams, and the dimensional ratios of the length, width, height, etc. of each component between different drawings do not necessarily match. For convenience of explanation, in this specification, the direction along the axial direction of the battery case 15 is defined as the height direction, the side of the sealing body 17 in the height direction is defined as "upper," and the bottom side of the outer can 16 in the height direction is defined as "lower." Among the components described below, components not recited in the independent claims representing the highest concept are optional components and not essential components.

[0014] FIG. 1 is an axial cross-sectional view of a cylindrical battery 10 according to one embodiment of the present disclosure, and FIG. 2 is a perspective view of an electrode assembly 14 of the cylindrical battery 10. As shown in FIG. 1, the cylindrical battery 10 includes a wound electrode assembly 14, a non-aqueous electrolyte (not shown), and a battery case 15 that accommodates the electrode assembly 14 and the non-aqueous electrolyte. As shown in FIG. 2, the electrode assembly 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 with the separator 13 interposed therebetween. Referring again to FIG. 1, the battery case 15 includes a cylindrical outer can 16 with a bottom and a sealing member 17 that closes the opening of the outer can 16. The cylindrical battery 10 also includes a resin gasket 28 interposed between the outer can 16 and the sealing member 17.

[0015] The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent include esters, ethers, nitriles, amides, and mixtures of two or more of these. The non-aqueous solvent may contain a halogen-substituted compound in which at least a portion of the hydrogen atoms in these solvents are replaced with halogen atoms such as fluorine. The non-aqueous electrolyte is not limited to a liquid electrolyte, but may also be a solid electrolyte using a gel polymer or the like. The electrolyte salt is a lithium salt such as LiPF6.

[0016] As shown in FIG. 2, the electrode assembly 14 has a long positive electrode 11, a long negative electrode 12, and two long separators 13. The electrode assembly 14 also has a positive electrode lead 20 joined to the positive electrode 11 and a negative electrode lead 21 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, and is formed to be longer than the positive electrode 11 in the longitudinal direction and width direction (short direction). The two separators 13 are also formed to be at least slightly larger than the positive electrode 11, and are arranged to sandwich the positive electrode 11, for example. .

[0017] The positive electrode 11 has a positive electrode current collector and a positive electrode mixture layer formed on both sides of the current collector. The positive electrode current collector can be a foil of a metal, such as aluminum or an aluminum alloy, that is stable within the potential range of the positive electrode 11, or a film with such a metal disposed on the surface layer. The positive electrode mixture layer contains a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 can be produced, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, etc., onto the positive electrode current collector, drying the coating, and then compressing it to form a positive electrode mixture layer on both sides of the current collector.

[0018] The positive electrode active material is mainly composed of a lithium-containing metal composite oxide. Examples of metal elements contained in the lithium-containing metal composite oxide 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 preferred lithium-containing metal composite oxide is a composite oxide containing at least one of Ni, Co, Mn, and Al.

[0019] Examples of conductive agents contained in the positive electrode mixture layer include carbon materials such as carbon black, acetylene black, ketjen black, and graphite. Examples of binders contained in the positive electrode mixture layer include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide, acrylic resin, and polyolefin. These resins may be used in combination with cellulose derivatives such as carboxymethyl cellulose (CMC) or its salts, and polyethylene oxide (PEO).

[0020] The negative electrode 12 has a negative electrode current collector and a negative electrode mixture layer formed on both sides of the current collector. The negative electrode current collector can be a foil of a metal, such as copper or a copper alloy, that is stable within the potential range of the negative electrode 12, or a film with such a metal disposed on the surface layer. The negative electrode mixture layer contains a negative electrode active material and a binder. The negative electrode 12 can be produced, for example, by applying a negative electrode mixture slurry containing the negative electrode active material and the binder onto the negative electrode current collector, drying the coating, and then compressing it to form a negative electrode mixture layer on both sides of the current collector.

[0021] The negative electrode active material generally uses a carbon material that reversibly absorbs and releases lithium ions. Preferred carbon materials include natural graphite such as flake graphite, lump graphite, and amorphous graphite, and artificial graphite such as lump artificial graphite and graphitized mesophase carbon microbeads. The negative electrode mixture layer may contain a Si-containing compound as the negative electrode active material. Furthermore, the negative electrode active material may include a metal other than Si that alloys with lithium, an alloy containing such a metal, or a compound containing such a metal.

[0022] The binder contained in the negative electrode mixture layer may be a fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, or the like, as in the case of the positive electrode 11. Preferably, styrene-butadiene rubber (SBR) or a modified product thereof is used. The negative electrode mixture layer may contain, in addition to SBR, for example, CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, or the like.

[0023] The separator 13 is a porous sheet having ion permeability and insulating properties. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. Preferred materials for the separator 13 include olefin resins such as polyethylene and polypropylene, and cellulose. The separator 13 may have either a single-layer structure or a laminated structure. A heat-resistant layer or the like may be formed on the surface of the separator 13. The negative electrode 12 may form the winding start end of the electrode assembly 14, but typically the separator 13 extends beyond the winding start end of the negative electrode 12, and the winding start end of the separator 13 becomes the winding start end of the electrode assembly 14.

[0024] In the example shown in FIGS. 1 and 2 , the positive electrode lead 20 is electrically connected to an intermediate portion, such as the center portion, of the positive electrode core in the winding direction, and the negative electrode lead 21 is electrically connected to the end of the negative electrode core in the winding direction. However, the negative electrode lead may be electrically connected to the end of the negative electrode core in the winding direction where the winding begins. Alternatively, the electrode body may have two negative electrode leads, one of which is electrically connected to the end of the negative electrode core in the winding direction where the winding begins, and the other negative electrode lead is electrically connected to the end of the negative electrode core in the winding direction. Alternatively, the end of the negative electrode core in the winding direction on the winding side may be abutted against the inner surface of the outer can, thereby electrically connecting the negative electrode and the outer can.

[0025] As shown in FIG. 1 , the cylindrical battery 10 further includes an insulating plate 18 disposed above the electrode assembly 14 and an insulating plate 19 disposed below the electrode assembly 14. In the example shown in FIG. 1 , a positive electrode lead 20 attached to the positive electrode 11 passes through a through-hole in the insulating plate 18 and extends toward the sealing body 17, and a negative electrode lead 21 attached to the negative electrode 12 passes outside the insulating plate 19 and extends toward the bottom 68 of the outer can 16. The positive electrode lead 20 is connected by welding or the like to the underside of a terminal plate 23, which is the bottom plate of the sealing body 17, and a valve body 27, which is the top plate of the sealing body 17 and is electrically connected to the terminal plate 23, serves as the positive electrode terminal. The negative electrode lead 21 is connected by welding or the like to the inner surface of the bottom 68 of the outer can 16, and the outer can 16 serves as the negative electrode terminal.

[0026] The outer can 16 is a metal container having a cylindrical portion with a bottom. An annular gasket 28 seals the space between the outer can 16 and the sealing body 17, sealing the interior space of the battery case 15. In this way, the gasket 28 serves as a sealing material to maintain airtightness inside the battery. The gasket 28 also includes a clamping portion 32 that is clamped between the outer can 16 and the sealing body 17, and insulates the sealing body 17 from the outer can 16. In this way, the gasket 28 also serves as an insulating material to prevent short-circuiting between the outer can 16 and the sealing body 17.

[0027] The outer can 16 has a protrusion 36 on its inner periphery that protrudes radially inward by providing an annular groove 35 along a portion of the height direction of the cylindrical outer periphery of the outer can 16. The annular groove 35 can be formed, for example, by spinning a portion of the cylindrical outer periphery radially inward to recess it radially inward. The outer can 16 has a bottomed tubular portion 30 including the protrusion 36 and an annular shoulder portion 33. The bottomed tubular portion 30 accommodates the electrode assembly 14 and the nonaqueous electrolyte. The shoulder portion 33 is bent radially inward from the end of the bottomed tubular portion 30 on the open side and extends inward. The shoulder portion 33 is formed when the upper end of the outer can 16 is bent inward and crimped to the peripheral edge 31 of the sealing body 17. The crimping secures the sealing body 17 to the outer can 16 via a gasket 28 at the shoulder 33 and the upper side of the protrusion 36.

[0028] Next, the sealing body 17 will be described. FIG. 3 is an enlarged cross-sectional view of the sealing body periphery of the cylindrical battery 10. As shown in FIG. 3, the sealing body 17 has a structure in which, from the electrode body 14 side, a terminal plate 23, an annular insulating plate 25, and a valve body 27 are stacked. The valve body 27 has a circular shape in a plan view. The valve body 27 can be produced, for example, by pressing a plate material made of aluminum or an aluminum alloy. Aluminum and aluminum alloys are preferred materials for the valve body 27 because they have excellent flexibility.

[0029] Valve element 27 has a circular shape in a plan view, and a thin-walled portion 27c is formed in the middle portion connecting central portion 27a and outer peripheral portion 27b. When the internal pressure of the battery increases, thin-walled portion 27c inverts and breaks, allowing valve element 27 to function as an explosion-proof valve. Central portion 27a is formed to protrude toward terminal plate 23, making it easy to connect valve element 27 and terminal plate 23.

[0030] The insulating plate 25 is formed in a circular ring shape in a plan view, and has a through-hole 25a in the center. The insulating plate 25 is fitted and fixed to a protrusion 27d formed so as to protrude downward from the outer periphery 27b of the valve body 27. The insulating plate 25 is provided to ensure insulation, and is designed to prevent the battery characteristics from being affected. It is preferable that the insulating plate 25 is made of a material that cannot withstand strong winds. Examples of the material for the insulating plate 25 include polymer resins, such as polypropylene (PP) resin and polybutylene terephthalate (PBT) resin. The insulating plate 25 has ventilation holes 25b on its outer periphery that penetrate it in the height direction. The insulating plate 25 also has an annular skirt portion 25c that extends downward at its outer periphery.

[0031] Terminal plate 23 has a circular outer shape with a smaller diameter than insulating plate 25 in a plan view, and has a thin-walled central portion 23a. Terminal plate 23 is disposed opposite valve body 27 with insulating plate 25 sandwiched therebetween. Terminal plate 23 is attached to insulating plate 25 by fitting its outer peripheral surface into and fixing it to the inner peripheral surface of skirt portion 25c of insulating plate 25. Valve body 27 and terminal plate 23 are connected at their centers via through-hole 25a in insulating plate 25.

[0032] Terminal plate 23 is preferably made of aluminum or an aluminum alloy, similar to valve body 27. This facilitates the connection of the central portions of valve body 27 and terminal plate 23. Metallurgical joining is preferably used as the connection method, and laser welding is an example of such metallurgical joining. Air vents 23b are formed on the outer periphery of terminal plate 23, penetrating terminal plate 23 in the height direction. Air vents 23b are connected to air vents 25b in insulating plate 25. As shown in FIG. 3 , the inner peripheral surface of skirt portion 25c may have a truncated cone shape whose inner diameter decreases downward, and the outer peripheral surface of terminal plate 23 may have a truncated cone shape corresponding to the inner peripheral surface. In such a case, terminal plate 23 can be press-fitted into skirt portion 25c to reliably prevent misalignment of terminal plate 23 relative to valve body 27.

[0033] Next, the short-circuit prevention structure of the positive electrode lead 20 in the gasket 28 and the support structure of the sealing body 17 will be described. FIG. 4 is an enlarged cross-sectional view of the periphery of the annular groove 35 of the outer can 16 in FIG. 1. As shown in FIG. 4, the gasket 28 includes a covering portion 41 in addition to the clamping portion 32 described above. The covering portion 41 is inclined so as to move radially inward as it moves downward in the height direction from the lower end of the clamping portion 32. The covering portion 41 covers at least a portion of the radially inner portion of the protruding portion 36. The covering portion 41 extends from the upper end of the protruding portion 36 to a position located below the minimum inner diameter portion 39, which has the smallest inner diameter of the protruding portion 36. This reliably prevents the positive electrode lead 20 (see FIG. 1) from shorting to the protruding portion 36.

[0034] Gasket 28 also includes support portion 42 that supports lower surface 45 of sealing member 17 on the lower side in the height direction (the surface facing bottom 68 (see FIG. 1 ) of outer can 16 in the height direction). At least a portion of support portion 42 is included in clamping portion 32. An inner peripheral surface 55 on the radially inward side of support portion 42 includes inclined surface portion 55a that moves radially outward as it approaches the lower side in the height direction. Support portion 42 also has protrusion 57 whose tip portion 57a ​​contacts undersurface 45 of sealing member 17, and a recess 59 exists between support portion 42 and undersurface 45 of sealing member 17, radially outward of protrusion 57. Inclined surface portion 55a on inner peripheral surface 55 of support portion 42 increases the support area of ​​support portion 42 for sealing member 17, allowing support portion 42 to be reliably supported by gasket 28. As shown in FIG. 4, it is preferable that the lower end 29 of the gasket 28 is positioned at a distance in the height direction from the insulating plate 18, and it is more preferable that the distance in the height direction between the lower end 29 of the gasket 28 and the insulating plate 18 is 1 mm or more.

[0035] Next, a method for forming the gasket 28 having the above structure inside the outer can 16 of the cylindrical battery 10 will be described. Figure 5 is a cross-sectional view of one side portion of the annular gasket 28 located on one side of the central axis before being incorporated into the outer can 16. First, the structure of the gasket 28 before being incorporated into the outer can 16 will be described using Figure 5.

[0036] As shown in FIG. 5, the gasket 28 includes a cylindrical portion 60 and an annular portion 61, and the annular portion 61 extends radially inward from one axial end of the cylindrical portion 60. A surface 67 of the annular portion 61 on the opposite side of the axial side from the cylindrical portion 60 is a substantially flat surface. A protrusion 57 is provided on the cylindrical portion 60 side facing the annular portion 61, the protrusion 57 being disposed radially apart from both the cylindrical portion 60 and a radial inner end 69 of the annular portion 61 and protruding in the axial direction. Furthermore, the axial thickness t1 of an outer portion 70 of the annular portion 61 located radially outward from the protrusion 57 is greater than the axial thickness t2 of an inner portion 71 of the annular portion 61 located radially inward from the protrusion 57. Of course, the axial thickness t1 of the outer portion 70 of the annular portion 61 located radially outward from the protrusion 57 and the axial thickness t2 of the inner portion 71 of the annular portion 61 located radially inward from the protrusion 57 may satisfy the relationship t1≦t2.

[0037] Next, the operation of incorporating (fitting) the gasket 28 into the outer can 16 will be described. Figures 6 and 7 are enlarged axial cross-sectional views of a portion of the cylindrical battery 10, showing the state of the gasket 28 during this operation. Figure 8 is an enlarged cross-sectional view of a reference example gasket 228, corresponding to Figure 5.

[0038] When assembling the cylindrical battery 10, it is preferable to first fit and secure the gasket 28 to the radially outer side of the sealing body 17. In this way, compared to when the gasket 28 and the sealing body 17 are fitted to the outer can 16 independently, the fitting process to the outer can 16 can be completed in one go, and covering the sealing body 17 with the gasket 28 reliably prevents a short circuit between the sealing body 17 and the outer can 16. Thereafter, the positive electrode lead 20 (see FIG. 1 ) extending from the electrode body 14 is electrically connected to the underside of the sealing body 17 by welding. In the gasket 28 of this embodiment, the lower surface 67 of the annular portion 61 is substantially flat. 8 , that is, gasket 228 having an annular flange 250 that protrudes downward in the height direction from the radially inner end of annular portion 261, the underside of sealing body 17 is not covered by flange 250, and the welding operation of positive electrode lead 20 to sealing body 17 can be carried out smoothly. Note that after sealing body 17 is welded to positive electrode lead 20, sealing body 17 may be fitted to gasket 28 that has been fitted to outer can 16 in advance.

[0039] Next, the gasket 28 integrated with the electrode body 14 and the sealing body 17 is fitted into the inner circumferential surface of the pre-crimped outer can 16, and then the upper end of the outer can 16 is deformed radially inward to form a shoulder 33. Then, as shown in Fig. 6 , an upper side 75 of the tubular portion 60 of the gasket 28 is bent radially inward, and the gasket 28 is compressed in the axial direction (height direction). As a result, a lower portion 74 of the gasket 28 located below the lower surface 45 of the sealing body 17 is stretched radially inward as indicated by arrow A.

[0040] 7, as the crimping of the outer can 16 progresses and the shoulder 33 deforms downward, the lower portion 74 is further compressed in the height direction, causing the protrusion 57 to deform so as to move radially inward as it moves upward in the height direction. At this time, an inclined surface portion 55a is formed on the inner circumferential surface 55 on the radially inner side of the protrusion 57.

[0041] Furthermore, due to the downward force that protrusion 57 receives from sealing body 17, inner portion 74a, which is located radially inward of protrusion 57 in lower portion 74, deforms diagonally downward as indicated by arrow B, starting from protrusion 57. As a result, the radially inner side of protrusion 36, in the height direction, from the upper end of protrusion 36 to a point located below minimum inner diameter portion 39, which has the smallest inner diameter, is covered with covering portion 41 formed by bending inner portion 74a.

[0042] As described above, in the gasket 28 of the present disclosure, the surface 67 of the annular portion 61 opposite the axial side of the cylindrical portion 60 is a substantially flat surface before being fitted into the outer can 16. Furthermore, the protrusions 57 protruding in the axial direction are provided on the inner end 69 of the cylindrical portion 60 and the annular portion 61 at a radial interval on the cylindrical portion 60 side of the annular portion 61.

[0043] Therefore, the surface 67 of the annular portion 61 opposite the axial side of the cylindrical portion 60 is a substantially flat surface, so that even if the gasket 28 is fixed to the sealing body 17, the positive electrode lead 20 can be easily welded to the sealing body 17.

[0044] Furthermore, the surface 67 of the annular portion 61 opposite the axial side of the cylindrical portion 60 is an approximately flat surface, so that the lower surface 67 of the annular portion 61 does not get caught on other members or parts while handling the gasket 28, and work related to the gasket 28 can be carried out smoothly.

[0045] Furthermore, because the gasket 28 has the above-mentioned protrusion 57, when the gasket 28 integrated with the sealing body 17 is fitted into the outer can 16, simply by crimping the outer can 16, the leading end side of the annular portion 61 of the gasket 28 can be easily deformed obliquely downward starting from the protrusion 57. Therefore, the covering portion 41 that covers the radially inner side of at least a portion of the protruding portion 36 of the outer can 16 can be easily formed.

[0046] Therefore, it is possible to reliably prevent short circuits between the positive electrode lead 20 and the outer casing 16, and the workability (process fluidity) during assembly of the cylindrical battery 10 can be significantly improved.

[0047] In addition, the forward thickness t1 of the outer side portion 70 located radially outward of the protrusion 57 in the annular portion 61 may be greater than the axial thickness t2 of the inner side portion 71 located radially inward of the protrusion 57 in the annular portion 61.

[0048] The above configuration reduces the rigidity of the inner portion 71, which is deformed when the gasket 28 is fitted into the outer can 16. Therefore, the inner portion 71 can be reliably bent diagonally downward when the gasket 28 is fitted into the outer can 16, and the covering portion 41 formed by bending the inner portion 71 diagonally can reliably cover at least a portion of the protrusion 36.

[0049] Furthermore, according to the cylindrical battery 10 of the present disclosure, the gasket 28 includes a support portion 42 (see FIG. 4) that supports a surface 45 (see FIG. 4) on the bottom 68 (see FIG. 1) side of the outer can 16 in the height direction (axial direction) of the sealing body 17, and an inner peripheral surface 55 on the radially inward side of the support portion 42 includes an inclined surface portion 55a that moves radially outward as it goes downward in the height direction.

[0050] Therefore, the area of ​​support portion 42 that supports lower surface 45 of sealing body 17 can be increased, and sealing body 17 can be supported stably.

[0051] Furthermore, support portion 42 may have protrusion 57 with tip portion 57 a contacting sealing body 17 .

[0052] According to the above configuration, the force that the protrusion 57 receives from the sealing body 17 can reliably cause the covering portion 41 to face downward, starting from the protrusion 57. This can reliably protect the positive electrode lead 20 from the protrusion 36, and more reliably prevent a short circuit between the positive electrode lead 20 and the protrusion 36.

[0053] Furthermore, the covering portion 41 may cover the radially inner side of the minimum inner diameter portion 39 of the protruding portion 36, which has the smallest inner diameter.

[0054] According to the above configuration, the portion of the protrusion 36 closest to the center is covered with the gasket 28. Therefore, short-circuiting of the positive electrode lead 20 can be reliably prevented.

[0055] The present disclosure is not limited to the above-described embodiment and its modifications, and various improvements and modifications are possible within the scope of the claims of the present application and their equivalents. be.

[0056] For example, with respect to the gasket before being fitted into the outer can, the axial thickness of the outer portion of the annular portion that is located radially outward from the protrusion may be equal to or less than the axial thickness of the inner portion of the annular portion that is located radially inward from the protrusion.

[0057] Also, the gasket 28 has been described as having a protrusion 57 that is generally rectangular in axial cross section, as shown in Fig. 5. However, as shown in Fig. 9, that is, a cross-sectional view of a modified gasket 128 corresponding to Fig. 5, the inner circumferential surface 157a on the radially inner side of the protrusion 157 may be a tapered surface that moves radially inward as it approaches a generally flat surface 167 in the axial direction.

[0058] In essence, the gasket of the present disclosure comprises a cylindrical portion and an annular portion extending radially inward from one axial end of the cylindrical portion, the surface of the annular portion opposite the axial side of the cylindrical portion being a substantially flat surface, and the axial side of the annular portion being provided with a protrusion that is radially spaced apart from both the cylindrical portion and the radial inner end of the annular portion and that protrudes axially, so long as this protrusion is provided.

[0059] Furthermore, in the cylindrical battery 10, the covering portion 41 has been described as covering the radially inner side of the minimum inner diameter portion 39, which has the smallest inner diameter, of the protruding portion 36. However, the covering portion does not have to cover the radially inner side of the minimum inner diameter portion, which has the smallest inner diameter, of the protruding portion.

[0060] Assume that a gasket used in a cylindrical battery has the following configuration: the gasket has a cylindrical portion and an annular portion extending radially inward from one axial end of the cylindrical portion. A protrusion is provided on the axial side of the annular portion facing the cylindrical portion, the protrusion being spaced radially from both the cylindrical portion and the radially inner end of the annular portion and protruding in the axial direction. Furthermore, the axial thickness of an outer portion of the annular portion located radially outward from the protrusion is greater than the axial thickness of an inner portion of the annular portion located radially inward from the protrusion.

[0061] In a gasket having the above configuration, the thickness of the outer portion is greater than the thickness of the inner portion, and therefore the rigidity of the inner portion is less than the rigidity of the outer portion. Therefore, with this configuration, even if the surface of the annular portion opposite the cylindrical portion in the axial direction is not substantially flat but has at least one or more recesses and one or more protrusions that reduce process fluidity (handling ease) during battery assembly, the inner portion is likely to bend downward from the protrusion when the gasket is fitted into the outer can. Therefore, the covering portion formed by the bending of the inner portion is likely to cover at least a portion of the protrusion. [Explanation of symbols]

[0062] 10 Cylindrical battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 16 Outer can, 17 Sealing body, 28, 128 Gasket, 32 Gasket clamping portion, 35 Annular groove, 36 Protrusion, 39 Minimum inner diameter portion, 41 Covering portion, 42 Support portion, 45 Bottom surface of outer can in the axial direction of the sealing body, 55 Inner surface of support portion, 55a Inclined surface portion, 57, 157 Protrusion, 57a Tip portion of protrusion, 60 Cylindrical portion, 61 Ring portion, 67, 167 Axial surface of ring portion opposite to the cylindrical portion side, 68 Bottom of outer can, 69 Radial inner end of ring portion, 70 Outer side portion, 71 Inner side portion, t1 t1: Axial thickness of outer side portion, t2: Axial thickness of inner side portion.

Claims

1. A cylindrical battery comprising a bottomed cylindrical outer can containing an electrode body, a sealing body, a negative electrode lead connected to the outer can, and a positive electrode lead connected to the sealing body, wherein an annular gasket is interposed between the outer can and the sealing body to prevent a short circuit between the outer can and the sealing body, The gasket before being incorporated into the outer can is A cylindrical portion; a ring portion extending radially inward from one axial end of the cylindrical portion, the annular portion has only one protrusion protruding in the axial direction from the cylindrical portion side in the axial direction, the protrusion is positioned at a distance in the radial direction from both the cylindrical portion and the inner end of the annular portion in the radial direction, a minimum value of the axial thickness of an outer side portion of the annular portion located radially outward from the protrusion is greater than a maximum value of the axial thickness of an inner side portion of the annular portion located radially inward from the protrusion; gasket.

2. a surface of the annular portion opposite to the cylindrical portion in the axial direction is a substantially flat surface; The gasket of claim 1.

3. The radially inner inner peripheral surface of the protrusion is a tapered surface that moves radially inward as it approaches the surface of the annular portion opposite the cylindrical portion in the axial direction, The gasket according to claim 1 or 2, wherein the inner peripheral surface has a larger area in the axial direction than the outer peripheral surface of the projection on the radially outer side.

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