Cylindrical battery

Abstract

A tip end part (41) on the upper side (opposite side from an electrode body in the axial direction) of a gasket (28) prior to deformation which is used in a cylindrical battery can be divided into nine sections (imaginary sections; a1 to a9) in the circumferential direction which have substantially the same circumferential direction length, wherein three sections among the nine sections (a1 to a9) that are positioned at substantially equal intervals in the circumferential direction each have one or more recesses (40). When N is defined as an integer not less than 3, a plurality of recesses (40) provided to the gasket (28) may include N substantially identical uniformly arranged recesses (42) that are arranged at substantially equal intervals in the circumferential direction.

Description

Cylindrical battery

[0001] The present disclosure relates to a cylindrical battery.

[0002] Conventionally, as a cylindrical battery, there is one described in Patent Document 1. This cylindrical battery includes an electrode body, a bottomed cylindrical outer can that houses the electrode body, a sealing body that closes the opening of the outer can, and an annular gasket sandwiched between the outer can and the sealing portion. The cylindrical portion of the outer can has a grooved portion and an annular shoulder portion. The grooved portion is formed by recessing a part of the cylindrical portion inward in the radial direction. The shoulder portion is formed when the tip portion of the cylindrical portion is bent inward and caulked to the peripheral edge portion of the sealing body, and extends inward in the radial direction. The sealing body is fixed to the outer can by being sandwiched between the shoulder portion and the grooved portion via the gasket by caulking.

[0003] Japanese Patent Application Laid-Open No. 09-274923

[0004] When the tip portion of the cylindrical portion is bent inward and caulked to the peripheral edge portion of the sealing body, the tip side of the gasket is also bent inward and its diameter is reduced. The degree of diameter reduction increases toward the tip of the gasket, and a circumferential compressive stress that increases toward the tip is generated inside the gasket. Against this background, if the compressive stress on the tip side of the gasket exceeds the buckling load due to dimensional tolerances of battery component parts, etc., the tip portion of the gasket buckles, causing wrinkles at the tip portion of the gasket, and there is a risk that the sealing performance of the cylindrical battery will deteriorate due to these wrinkles. Therefore, an object of the present disclosure is to provide a cylindrical battery capable of suppressing the generation of wrinkles on the tip side of the gasket.

[0005] The cylindrical battery according to the present disclosure includes an electrode body, an outer can that houses the electrode body, and a sealing body that seals the opening of the outer can via an annular gasket, and the tip portion of the gasket before deformation that does not contact the outer can on the side opposite to the electrode body side in the axial direction can be divided into nine circumferential sections having substantially the same circumferential length, and one or more recesses are present in each of three sections that are positioned at substantially equal intervals in the circumferential direction among the nine sections.

[0006] According to the cylindrical battery according to the present disclosure, the generation of wrinkles on the tip side of the gasket can be suppressed.

[0007] This is an axial cross-sectional view of a cylindrical battery according to one embodiment of the present disclosure. (a) is a side view of the gasket before deformation, which is not in contact with the outer casing, as seen from the radially outward side, and (b) is a top view of the gasket before deformation, as seen from the axially upper side. (a) is a side view of the gasket of the reference example, corresponding to Figure 2(a), and (b) is a top view of the gasket of the reference example, corresponding to Figure 2(b). This is a cross-sectional view of a portion of the tip side of the gasket of the reference example after crimping in a harsh test under severe conditions with excessively high compression and diameter reduction ratios, when cut in a plane including the radial and axial directions. (a) is a cross-sectional view of the gasket before deformation when it is cut by a cylindrical surface that centers on the central axis of the gasket before deformation of the embodiment, and passes through the upper end surface of the gasket before deformation, illustrating the shape of the recess. (b) is a cross-sectional view of the gasket before deformation of the first modified example, corresponding to (a); (c) is a cross-sectional view of the gasket before deformation of the second modified example, corresponding to (a); and (d) is a cross-sectional view of the gasket before deformation of the third modified example, corresponding to (a).

[0008] Hereinafter, embodiments of the cylindrical battery according to this disclosure will be described in detail with reference to the drawings. The cylindrical battery of this disclosure may be a primary battery or a secondary battery. Furthermore, the cylindrical battery of this disclosure may be a battery using an aqueous electrolyte or a battery using a non-aqueous electrolyte. In the following, a cylindrical lithium-ion secondary battery using a non-aqueous electrolyte will be given as an example of one embodiment of the cylindrical battery 10, but the cylindrical battery of this disclosure is not limited to this.

[0009] It is intended from the outset that new embodiments can be constructed by appropriately combining the characteristic features of the embodiments and modifications described below. In the following embodiments, the same reference numerals are used for the same components in the drawings, and redundant explanations are omitted. In addition, multiple drawings include schematic diagrams, and the dimensional ratios such as length, width, and height of each component do not necessarily match between different drawings. In this specification, the side of the cylindrical battery 10 with the sealing body 17 in the axial direction (height direction) is referred to as "upper," and the side of the outer casing 16 with the bottom 31 in the axial direction is referred to as "lower." Furthermore, among the components described below, components that are not described in the independent claim indicating the highest-level concept are optional components and are not essential components.

[0010] Figure 1 is an axial cross-sectional view of a cylindrical battery 10 according to one embodiment of the present disclosure. As shown in Figure 1, the cylindrical battery (hereinafter simply referred to as "battery") 10 comprises an electrode body 14, a non-aqueous electrolyte (not shown), a metal, bottomed cylindrical outer casing 16 that houses the electrode body 14 and the non-aqueous electrolyte, and a sealing body 17 that closes the opening of the outer casing 16 via an annular gasket 28. The gasket 28 is preferably made of an insulating material with excellent compressibility and resistance, for example, a polyolefin, and more specifically, preferably PP (polypropylene), PPS (polyphenylene sulfide), PFA (perfluoroalkoxyalkane), or PPT (polypropylene terephthalate). The outer casing may have openings at both ends in the axial direction, and the cylindrical battery may have a configuration in which the upper and lower openings of the outer casing are each closed by one or more members.

[0011] The electrode body 14 includes a long positive electrode 11, a long negative electrode 12, and two long separators 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 along the longitudinal direction via the separators 13. The negative electrode 12 is formed to be slightly larger in dimensions than the positive electrode 11 in order to prevent lithium deposition. The negative electrode 12 is formed to be longer than the positive electrode 11 in the winding direction and in the axial direction. The two separators 13 are formed to be slightly larger in dimensions than the positive electrode 11 and are arranged to sandwich the positive electrode 11. The separators 13 protrude above and below the positive electrode 11 and the negative electrode 12.

[0012] Non-aqueous electrolytes are ionic conductive (e.g., lithium ion conductive). Non-aqueous electrolytes may be liquid electrolytes (electrolytes) or solid electrolytes. Liquid electrolytes (electrolytes) contain a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents include esters, ethers, nitriles, amides, and mixtures of two or more of these. Examples of non-aqueous solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixtures thereof. Non-aqueous solvents may contain halogen-substituted solvents (e.g., fluoroethylene carbonate) in which at least some of the hydrogen atoms of these solvents are replaced with halogen atoms such as fluorine. Examples of electrolyte salts include LiPF4. ６ Lithium salts such as these are used.

[0013] As solid electrolytes, for example, solid or gel-like polymer electrolytes, inorganic solid electrolytes, etc., are used. Polymer electrolytes include, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt and a matrix polymer. As matrix polymers, for example, polymer materials that absorb non-aqueous solvents and gel are used. As polymer materials, for example, fluororesins, acrylic resins, polyether resins, etc., are used. As inorganic solid electrolytes, for example, materials known for all-solid-state lithium-ion secondary batteries, etc. (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.) are used.

[0014] The positive electrode 11 has a positive electrode core and a positive electrode mixture layer formed on both sides of the positive electrode core. The positive electrode core can be made of a metal foil that is stable within the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film with the metal arranged on its surface. The positive electrode mixture layer contains a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 is manufactured, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder onto the positive electrode core, drying the coating, and then compressing it to form the positive electrode mixture layer on both sides of the positive electrode core.

[0015] 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. A preferred example of a lithium-containing metal composite oxide is a composite oxide containing at least one of Ni, Co, Mn, and Al.

[0016] Examples of conductive agents included in the positive electrode mixture layer include carbon black such as acetylene black and Ketjen black, and carbon materials such as graphite. Examples of binders included in the positive electrode mixture layer include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. These resins may be used in combination with cellulose derivatives such as carboxymethylcellulose (CMC) or its salts, polyethylene oxide (PEO), etc.

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

[0018] Generally, carbon materials that reversibly intercept and release lithium ions are used as the negative electrode active material. Preferred carbon materials are graphite such as natural graphite such as flake graphite, lump graphite, and clay graphite, and artificial graphite such as lump graphite and graphitized mesophase carbon microbeads. The negative electrode mixture layer may contain silicon (Si) material as the negative electrode active material. In addition, metals that alloy with lithium other than Si, alloys containing such metals, compounds containing such metals, etc., may be used as the negative electrode active material.

[0019] The binder included in the negative electrode mixture layer may be fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, etc., as in the case of the positive electrode 11, but preferably styrene-butadiene rubber (SBR) or a modified version thereof is used. In addition to SBR, the negative electrode mixture layer may also contain, for example, CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, etc.

[0020] A porous sheet having ion permeability and insulating properties is used for the separator 13. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. The material of the separator 13 is preferably polyethylene, polyolefin resins such as polypropylene, or 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.

[0021] An upper insulating plate 18 is positioned above the electrode body 14, and a lower insulating plate 19 is positioned below the electrode body 14. In the example shown in Figure 1, a single positive electrode lead 20 attached to the positive electrode 11 extends through a through-hole in the upper insulating plate 18 towards the sealing body 17 and is joined to the lower surface of the sealing body 17. One end of the positive electrode lead 20 is joined to the positive electrode 11 of the electrode body 14 by ultrasonic welding or the like, and the other end of the positive electrode lead 20 is joined to the lower surface of the sealing body 17 by welding or the like. On the other hand, the negative electrode lead 21 attached to the negative electrode 12 extends through the outside of the lower insulating plate 19 towards the bottom 31 of the outer container 16 and is joined to the inner surface of the bottom 31. One end of the negative electrode lead 21 is joined to the negative electrode 12 of the electrode body 14 by ultrasonic welding or the like, and the other end of the negative electrode lead 21 is joined to the bottom 31 by welding or the like.

[0022] To effectively suppress short circuits, it is preferable that the area around the joint that connects the positive electrode 11 to the positive electrode lead 20 is covered with insulating tape (not shown), and it is preferable that the area around the joint that connects the negative electrode 12 to the negative electrode lead 21 is covered with insulating tape (not shown). Here, these insulating tapes are made of an insulating material, for example, a polyimide film may be used as the base material and a silicone adhesive may be used.

[0023] In the example shown in Figure 1, the positive lead 20 is electrically connected to an intermediate part of the positive core, such as the center in the winding direction, and the negative lead 21 is electrically connected to the winding end in the negative core. However, the positive lead may be electrically connected to a location other than the intermediate part of the positive core in the winding direction, and the negative lead may be electrically connected to a location other than the winding end in the negative core.

[0024] The electrode body may have two negative electrode leads, with one end of one negative electrode lead electrically connected to the winding start end in the winding direction of the negative electrode core body, and the other end of the negative electrode lead electrically connected to the bottom of the outer can. Then, one end of the other negative electrode lead may be electrically connected to the winding end in the winding direction of the negative electrode core body, and the other end of the other negative electrode lead electrically connected to the bottom of the outer can. Alternatively, the negative electrode and the bottom of the outer can may be electrically connected by bringing the exposed negative electrode core portion, which constitutes part or all of the outer surface of the electrode body and exposes the negative electrode core body, into contact with the inner surface of the outer can.

[0025] Furthermore, there may be multiple positive electrode leads (for example, eight positive electrode leads) whose one end is joined to the positive electrode core at intervals along the longitudinal direction of the positive electrode, and the other ends of the multiple positive electrode leads may be joined to a metal current collector plate included in the sealing body by laser welding or the like. Alternatively, the upper end of the positive electrode core may constitute the upper end of the electrode body, and the upper end of the positive electrode core may be joined to a metal current collector plate included in the sealing body by laser welding or the like. Also, the lower end of the negative electrode core may constitute the lower end of the electrode body. The lower end of the negative electrode core may be joined to the upper surface of a metal current collector plate by laser welding or the like, and the lower surface of the current collector plate may be joined to the bottom of the outer casing by laser welding or the like. Furthermore, the negative electrode may be electrically connected to the sealing body, and the positive electrode may be electrically connected to the outer casing.

[0026] The outer can 16 is made of a metal mainly composed of iron, for example, iron with nickel plating, or a metal mainly composed of aluminum. The outer can 16 has a cylindrical portion 39 and a bottom portion 31, and the cylindrical portion 39 includes an annular grooved portion 22 and an annular shoulder portion 29. The grooved portion 22 is formed by spinning a part of the cylindrical portion 39 to create a recess radially inward along the entire circumference. The shoulder portion 29 is formed when the upper end of the cylindrical portion 39 is bent radially inward and crimped to the peripheral edge portion 33 of the sealing body 17, and extends radially inward at the upper end of the cylindrical portion 39.

[0027] The sealing body 17 is fixed to the outer can 16 by crimping, with a gasket 28 sandwiched between the shoulder portion 29 and the grooved portion 22. The grooved portion 22 is formed at a predetermined distance from the upper end of the outer can 16. The predetermined length is, for example, 1 to 20% of the axial length of the outer can 16. The gasket 28 is strongly compressed by the shoulder portion 29, and a portion of the gasket 28 protrudes radially inward from between the shoulder portion 29 and the sealing body 17.

[0028] The sealing body 17 has a structure in which a terminal plate 23, a lower valve body 24, an annular insulating plate 25, an upper valve body 26, and a terminal cap 27 are stacked in this order from the electrode body 14 side. The terminal plate 23, the lower valve body 24, and the upper valve body 26 have a substantially circular shape when viewed from above in the axial direction, and the insulating plate 25 has a substantially annular shape when viewed from above in the axial direction. The members of the sealing body 17, excluding the insulating plate 25, are electrically connected to each other. The terminal cap 27 has a convex shape with its radial center portion protruding outward. The convex portion 27a of the terminal cap 27 includes an annularly formed slanted portion and a flat top portion surrounded by the slanted portion. One or more ventilation holes 27b are formed in the top portion. The convex portion of the terminal cap 27 may have a cylindrical portion instead of the annular slanted portion.

[0029] The lower valve body 24, the insulating plate 25, and the upper valve body 26 constitute a current interruption mechanism. The lower valve body 24 and the upper valve body 26 are connected at their respective centers, and the insulating plate 25 is interposed between the peripheral edges of the lower valve body 24 and the upper valve body 26. When the battery 10 overheats abnormally and the internal pressure rises, the lower valve body 24 deforms and breaks, pushing the upper valve body 26 towards the terminal cap 27, thereby interrupting the current path between the lower valve body 24 and the upper valve body 26. Because the annular insulating plate 25 is interposed between the peripheral edges of the lower valve body 24 and the upper valve body 26, re-conduction between the lower valve body 24 and the upper valve body 26 is prevented. If the internal pressure rises further, the upper valve body 26 breaks, and the contents (high-temperature gas and molten material) are discharged from the vent hole 27b of the terminal cap 27. By releasing the contents in this way, it is possible to prevent the internal pressure of the battery 10 from rising excessively and causing the battery 10 to rupture, thereby increasing the safety of the battery 10.

[0030] In this embodiment, one end of the positive lead 20 is connected to the lower surface of the terminal plate 23 by welding or ultrasonic welding, and the terminal cap 27, which is the top plate of the sealing body 17 electrically connected to the terminal plate 23, becomes the positive terminal. The negative lead 21 is connected to the inner surface of the bottom 31 of the outer can 16 by welding or ultrasonic welding, and the outer can 16 becomes the negative terminal.

[0031] The case described above has been in which the sealing body 17 has a laminated structure including two rupture plates (lower valve body 24 and upper valve body 26) and a convex terminal cap 27 covering the two rupture plates. However, the sealing body may consist only of one rupture plate having a rupture portion that breaks as the internal pressure rises, or it may have a structure in which an internal terminal plate, an annular insulating plate, and a rupture plate are laminated in order from the electrode body side. Alternatively, the sealing body may not have rupture plates, and for example, the sealing body may have a structure in which the sealing plate and the current collector plate are integrated, comprising a sealing plate and a current collector plate on which a plurality of positive electrode leads are welded by laser welding or the like. Alternatively, the sealing body may have a structure in which the sealing plate and the current collector plate are integrated, comprising a sealing plate and a current collector plate on which a positive electrode core exposed portion provided at one end of the electrode body in the height direction is welded by laser welding or the like. If the sealing body does not have a rupture plate, it is preferable that the bottom of the outer can has a thin, easily breakable section that ruptures as the internal pressure increases.

[0032] Figure 2(a) is a side view of the gasket 28 before deformation, when viewed from the radially outward side, and Figure 2(b) is a top view of the gasket 28 before deformation, when viewed from the axially upper side. As shown in Figure 2, a plurality of recesses 40 are provided on the upper end face of the gasket 28. The gasket 28 before deformation, having the plurality of recesses 40, can be easily manufactured by simply providing protrusions in the mold used to manufacture the gasket 28 before deformation by injection molding, at locations corresponding to the recesses 40.

[0033] As shown in Figure 2(b), the tip 41 of the gasket 28 before deformation, on the side opposite to the electrode body 14 in the axial direction, is divided into nine circumferential sections (virtual sections) a1 to a9 having substantially the same circumferential length, and each of the nine sections a1 to a9 has one or more recesses 40 in three sections that are substantially equally spaced in the circumferential direction. In this embodiment, the sets of three sections are as follows: section a1, section a4 and section a7; section a2, section a5 and section a8; and section a3, section a6 and section a9.

[0034] In this embodiment, when N is an integer of 3 or more, the plurality of recesses 40 provided in the gasket 28 include N substantially identical, evenly spaced recesses 42 arranged at substantially equal intervals in the circumferential direction, and furthermore, the plurality of recesses 40 provided at the upper end of the gasket 28 are composed only of N evenly spaced recesses 42. In this embodiment, the recesses 40 have a substantially rectangular shape in a cross-section obtained by cutting the gasket 28 before deformation, with the central axis of the gasket 28 as the central axis and passing through the upper end surface 45 of the gasket 28 before deformation as the central axis (see Figure 5(a)).

[0035] Next, the effects of the battery 10 of this disclosure will be described. Figure 3(a) is a side view of the gasket 428 of the reference example corresponding to Figure 2(a), and Figure 3(b) is a top view of the gasket 428 of the reference example corresponding to Figure 2(b). The gasket 428 of the reference example shown in Figure 3 differs from the gasket 28 of this embodiment in that it does not have a recess 40 at its upper end.

[0036] When the upper end of the outer can is folded inward and crimped to the periphery of the sealing body, the tip of the gasket is also folded inward and its diameter is reduced. The degree of diameter reduction increases towards the tip of the gasket, and a circumferential compressive stress that increases towards the tip is generated within the gasket. Against this backdrop, if a recess 40 is not provided at the upper end, as in the gasket 428 of the reference example, the compressive stress at the tip of the gasket 428 may exceed the buckling load due to dimensional tolerances of the battery components, etc. If the compressive stress exceeds the buckling load, the upper tip 441 of the gasket 428 will buckle, causing wrinkles to form at the tip 441 of the gasket 428, and these wrinkles may reduce the sealing performance of the cylindrical battery.

[0037] In contrast, according to the battery 10 of this disclosure, one or more recesses 40 are provided in each of the three sections at the upper end of the gasket 28. Therefore, when the upper end of the outer casing 16 is folded inward and crimped to the peripheral edge 33 of the sealing body 17, and the tip of the gasket 28 is reduced in diameter, the material around the recess 50 can be released into the recess 40 so as to narrow the circumferential length of the recess 40 for at least three recesses that are arranged at nearly equal intervals in the circumferential direction. Thus, the compressive stress on the tip of the gasket 28 during crimping is relieved, and the occurrence of wrinkles on the tip of the gasket 28 can be suppressed. As a result, the sealing performance of the battery 10 is more likely to be excellent, and the occurrence of rust due to electrolyte leakage can be effectively suppressed. Note that as the diameter reduction on the tip of the gasket 28 progresses, the recesses 40 gradually collapse and become invisible or almost invisible after crimping.

[0038] The inventors conducted a cruel test on a cylindrical battery of a reference example, comparing it to the battery 10 in which a plurality of identical recesses 40, each with a circumferential width of 0.3 mm and a depth of 0.2 mm, are evenly arranged in the main direction, and the ratio of the circumferential length of the recess 40 formation area on the circumference to the circumferential length of the circumference passing through the radial center of the upper end surface 45 of the gasket 28 before deformation is 20%, in which the gasket 428 of the reference example is used instead of the gasket 28. The inventors subjected the battery 10 to a cruel test under harsh conditions in which the gasket compression ratio and diameter reduction ratio were excessively high.

[0039] Furthermore, through this tricky test, the circumferential average of the upper wrinkle height (outer wrinkle height) b1 (see Figure 4) and the circumferential average of the lower wrinkle height (inner wrinkle height) b2 (see Figure 4) of the wrinkles 470 formed on the gasket 428 of a cylindrical battery made using a reference example gasket 428 without the recess 40 were calculated. In addition, through this tricky test, the circumferential average of the upper wrinkle height (outer wrinkle height) b1 and the circumferential average of the lower wrinkle height (inner wrinkle height) b2 of the wrinkles formed on the gasket 28 of the battery 10 were also calculated.

[0040] Furthermore, in the aforementioned tricky test, it was confirmed that the circumferential average of the upper wrinkle height (outer wrinkle height) b1 of the battery 10's gasket 28 could be drastically reduced by 51% when compared with a reference example cylindrical battery made using a reference example gasket 428 without the recess 40. In addition, in the same tricky test, it was confirmed that the circumferential average of the lower wrinkle height (inner wrinkle height) b2 of the battery 10's gasket 28 could be drastically reduced by 40% when compared with the circumferential average of the lower wrinkle height (inner wrinkle height) b2 of a reference example cylindrical battery made using a reference example gasket 428 without the recess 40.

[0041] It is preferable that the circumferential width of each recess 40 provided at the upper end of the gasket 28 before deformation is 0.25 mm or more, as this effectively suppresses the occurrence of wrinkles and makes it easier to achieve good sealing of the battery 10. It is preferable that the circumferential width of each recess 40 provided at the upper end of the gasket 28 before deformation is 0.5 mm or less, as this makes it easier for the circumferential compressive stress on the tip side of the gasket 28 to be large enough to achieve good sealing of the battery 10. It is preferable that the depth of each recess 40 provided at the upper end of the gasket 28 before deformation is 0.05 mm or more, as this effectively suppresses the occurrence of wrinkles and makes it easier to achieve good sealing of the battery 10. It is preferable that the depth of each recess 40 provided at the upper end of the gasket 28 before deformation is 0.25 mm or less, as this makes it easier for the circumferential compressive stress on the tip side of the gasket 28 to be large enough to achieve good sealing of the battery 10.

[0042] Since it is possible to effectively suppress the occurrence of wrinkles and facilitate the realization of good sealing performance of the battery 10, it is preferable that the ratio of the circumferential length of the portion where the concave portion 40 is formed in the circumference passing through the radial center of the upper end surface 45 of the gasket 28 before deformation to the circumferential length of the circumference is 15% or more. Since the circumferential compressive stress on the tip side of the gasket 28 is likely to be of a magnitude that can achieve good sealing performance of the battery 10, it is preferable that the ratio of the circumferential length of the portion where the concave portion 40 is formed in the circumference passing through the radial center of the upper end surface 45 of the gasket 28 before deformation to the circumferential length of the circumference is 40% or less.

[0043] The present disclosure is not limited to the above-described embodiments and their modified examples, and various improvements and modifications can be made within the scope of the matters described in the claims of the present application and their equivalent scope. For example, in the above-described embodiment, the case where a plurality of substantially identical concave portions 40 (equally arranged concave portions 42) are provided at substantially equal intervals in the circumferential direction at the upper end portion of the gasket 28 before deformation (corresponding to the tip portion on the opposite side of the axial electrode body 14 side in the gasket 28 in the state incorporated in the battery 10) has been described.

[0044] However, a plurality of substantially identical concave portions may be provided at non-uniform intervals in the circumferential direction at the upper end portion of the gasket before deformation. In this case, three or more concave portions (equally arranged concave portions) arranged at equal intervals may be included in the plurality of concave portions. Alternatively, a plurality of substantially identical concave portions may be provided at non-uniform intervals in the circumferential direction at the upper end portion of the gasket before deformation. In this case, three or more concave portions (equally arranged concave portions) arranged at equal intervals may not exist in the plurality of concave portions. Further, two or more different concave portions may be included in the plurality of concave portions provided at the upper end portion of the gasket before deformation.

[0045] As shown in Figure 5(a), the case described above has been described in which all recesses 40 have a substantially rectangular shape in the cross-section obtained when the gasket 28 is cut using a cylindrical surface with the central axis of the gasket 28 before deformation as its central axis and passing through the upper end surface 45 of the gasket 28 before deformation. However, each recess may have any shape in the cross-section obtained when the gasket is cut using a cylindrical surface with the central axis of the gasket before deformation as its central axis and passing through the upper end surface of the gasket before deformation. For example, in the cross-section obtained when the gasket is cut using a cylindrical surface with the central axis of the gasket before deformation as its central axis and passing through the upper end surface of the gasket before deformation, some recesses may have a substantially rectangular shape, while one or more recesses have a shape that is not substantially rectangular.

[0046] Furthermore, as shown in Figure 5(b), in a cylindrical surface with the central axis of the gasket 128 before deformation as its central axis, and passing through the upper end surface 145 of the gasket 128 before deformation, at least one recess 140 (or all recesses) may have a substantially semi-elliptical shape in the cross-section when the gasket 128 before deformation is cut. Furthermore, as shown in Figure 5(c), in a cylindrical surface with the central axis of the gasket 228 before deformation as its central axis, and passing through the upper end surface 245 of the gasket 228 before deformation, at least one recess 240 (or all recesses) may have a substantially semi-circular shape in the cross-section when the gasket 228 before deformation is cut.

[0047] Alternatively, as shown in FIG. 5(d), it may be a cylindrical surface centered on the central axis of the gasket 328 before deformation, passing through the upper end surface 345 of the gasket 328 before deformation. In the cross-section when the gasket 328 before deformation is cut, at least one recess 340 (it may be all the recesses) may have a shape of a substantially isosceles triangle (including a substantially equilateral triangle) whose circumferential width decreases as the depth increases. When the recess 340 having a substantially isosceles triangle in the cross-section is formed in the gasket 328, stress can be concentrated at the tip 348 of the recess 340 during diameter reduction. Therefore, during diameter reduction, the gasket 328 can be smoothly deflected starting from the tip 348. Thus, the recess 340 can be smoothly crushed during diameter reduction, and the generation of wrinkles can be more effectively suppressed.

[0048] The cylindrical battery of this disclosure may have the following configurations: Configuration 1: A cylindrical battery comprising an electrode body, an outer casing for housing the electrode body, and a sealing body for sealing the opening of the outer casing via an annular gasket, wherein the tip of the gasket, before deformation and not in contact with the outer casing, on the side opposite to the electrode body in the axial direction, can be divided into nine circumferential sections having substantially the same circumferential length, and each of the nine sections having one or more recesses in three sections that are substantially equally spaced in the circumferential direction. Configuration 2: The cylindrical battery according to Configuration 1, wherein when N is an integer of 3 or more, the plurality of recesses provided in the gasket include the N substantially identical, evenly spaced recesses arranged substantially equally in the circumferential direction. Configuration 3: The cylindrical battery according to Configuration 2, wherein the plurality of recesses consist only of the N evenly spaced recesses. Configuration 4: The cylindrical battery according to any one of Configurations 1 to 3, wherein the circumferential width of each recess is 0.25 mm or more and 0.5 mm or less. Configuration 5: A cylindrical battery according to any one of Configurations 1 to 4, wherein the depth of each recess is 0.05 mm or more and 0.25 mm or less. Configuration 6: A cylindrical battery according to any one of Configurations 1 to 5, wherein the cylindrical surface has the central axis of the gasket before deformation as its central axis, and the cylindrical surface passes through the end face on the tip side in the axial direction of the gasket before deformation, and in the cross-section when the gasket before deformation is cut, each recess has the shape of a substantially isosceles triangle in which the circumferential width decreases as the depth increases.

[0049] 10 Battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 16 Outer casing, 17 Sealing body, 18 Upper insulating plate, 19 Lower insulating plate, 20 Positive electrode lead, 21 Negative electrode lead, 22 Grooved section, 23 Terminal plate, 24 Lower valve body, 25 Insulating plate, 26 Upper valve body, 27 Terminal cap, 27a Protrusion, 27b Ventilation hole, 28, 128, 228, 328, 428 Gasket, 29 Shoulder section, 31 Bottom section, 33 Peripheral section, 39 Cylindrical section, 40, 140, 240, 340 Recess, 41 Upper tip of gasket, 42 Evenly distributed recesses, 45, 145, 245, 345 Upper end surface of the gasket, 348 Tip of the recess, 470 Wrinkle, a1, a2, a3, a4, a5, a6, a7, a8, a9 Sections.

Claims

1. A cylindrical battery comprising: an electrode body; an outer can for housing the electrode body; and a sealing body for sealing the opening of the outer can via an annular gasket, wherein the tip of the gasket, before deformation and not in contact with the outer can, on the side opposite to the electrode body in the axial direction, can be divided into nine circumferential sections having substantially the same circumferential length, and each of the nine sections having one or more recesses in three sections that are substantially equally spaced in the circumferential direction.

2. When N is an integer of 3 or more, the cylindrical battery according to claim 1, wherein the plurality of recesses provided in the gasket include the N substantially identical and evenly spaced recesses arranged at substantially equal intervals in the circumferential direction.

3. The cylindrical battery according to claim 2, wherein the plurality of recesses are composed only of the N evenly spaced recesses.

4. The cylindrical battery according to any one of claims 1 to 3, wherein the circumferential width of each recess is 0.25 mm or more and 0.5 mm or less.

5. The cylindrical battery according to any one of claims 1 to 3, wherein the depth of each recess is 0.05 mm or more and 0.25 mm or less.

6. A cylindrical battery according to any one of claims 1 to 3, wherein the cylindrical surface has the central axis of the gasket before deformation as its central axis, and the cylindrical surface passes through the end face on the tip side in the axial direction of the gasket before deformation, and in the cross-section when the gasket before deformation is cut, each of the recesses has the shape of a substantially isosceles triangle in which the circumferential width decreases as the depth increases.

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