Cylindrical battery and method for manufacturing cylindrical battery

Abstract

This cylindrical battery includes an electrode body, an exterior can (20), and a sealing body (19) swaged and fixed to the opening of the exterior can (20) via a gasket (24). The exterior can (20) has: a tip bent part (30) bent so as to extend inward in the radial direction in an opening adjacent to the gasket (24); and a tip cylindrical part (31) extending in the axial direction. The gasket (24) has a non-continuous part (48) that can be separated in the axial direction at an opposing part (45) that faces the radially inner side of the tip cylindrical part (31).

Description

Cylindrical battery and manufacturing method thereof

[0001] The present disclosure relates to cylindrical batteries and methods for manufacturing cylindrical batteries.

[0002] Conventionally, a cylindrical battery has been known that includes an electrode assembly, a cylindrical outer can with a bottom that houses the electrode assembly, and a sealing body that closes the opening of the outer can. Patent Document 1 describes a cylindrical battery in which a cap (sealing body) is crimped and fixed to the opening of the outer can via a gasket.

[0003] Japanese Patent Application Publication No. 11-307067

[0004] In the configuration described in Patent Document 1, to fix the sealing body to the opening of the outer can via a gasket, the front end of the outer can is extended in the axial direction, the gasket is placed inside the can, and the front end of the outer can is bent radially inward. Furthermore, forces are generated between a constricted portion (grooved portion) located in the middle of the outer can and the front end of the outer can in opposing directions, which further deforms the front end of the outer can and compresses the gasket. During this compression, tensile stress is generated outward at the corner of the outer can adjacent to the front end of the outer can, and large stress is applied inward from the compressed gasket, resulting in stress concentration. This may cause damage to the corner when the battery is used under harsh conditions.

[0005] Therefore, an object of the present disclosure is to provide a cylindrical battery and a method for manufacturing a cylindrical battery that can reduce stress concentration at the corners of the outer can when the gasket is compressed by the tip of the outer can.

[0006] 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; a bottomed cylindrical outer can that houses the electrode assembly; and a sealing body that is crimped and fixed to the opening of the outer can via a gasket; the outer can includes a tip bent portion that is bent so as to extend radially inward at the opening adjacent to the gasket, and a tip tubular portion that extends in the axial direction; and the gasket has a discontinuous portion that is axially separable at an opposing portion that faces the radially inward side of the tip tubular portion.

[0007] The manufacturing method of a cylindrical battery according to the present disclosure is a manufacturing method of a cylindrical battery including an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, a bottomed cylindrical outer can that houses the electrode assembly, and a sealing body that is crimped and fixed to the opening of the outer can via a gasket, in which a gasket is placed adjacent to the inside of the opening of the outer can, and the front end of the outer can is bent radially inward by 90 degrees or more from a state in which it extends in the axial direction, to form a front bent portion and a front tubular portion that is located on the bottom side of the front bent portion and extends in the axial direction, and the gasket is axially compressed via the front bent portion from a state in which the gasket is separated in the axial direction via a gap at an opposing portion that faces the radially inner side of the front tubular portion.

[0008] According to the cylindrical battery and method for manufacturing a cylindrical battery according to the present disclosure, stress concentration at the corners of the outer can can be reduced when the gasket is compressed by the leading end of the outer can.

[0009] Fig. 2 is an axial cross-sectional view of a cylindrical battery according to an embodiment of the present disclosure. Fig. 3 is an enlarged cross-sectional view of a portion in the circumferential direction of a gasket before being incorporated into the cylindrical battery of Fig. 1. Fig. 4 is an enlarged cross-sectional view corresponding to part A of Fig. 1, illustrating a method of incorporating a gasket into the outer can of the cylindrical battery of Fig. 1, bending the front end of the outer can, and further compressing the gasket in the axial direction. Fig. 5 is an enlarged cross-sectional view corresponding to part A of Fig. 1, illustrating damage to the outer can due to use under harsh conditions, after incorporating a gasket into the outer can of a comparative cylindrical battery, bending the front end of the outer can, and further compressing the gasket in the axial direction. Fig. 6 is a view corresponding to Fig. 3 of a cylindrical battery of another example of an embodiment.

[0010] 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. Hereinafter, 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, and the electrolyte may also be an aqueous electrolyte.

[0011] It is anticipated from the beginning that new embodiments may be constructed by appropriately combining the features of the embodiments and variations described below. 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, and other dimensions of each component between different drawings do not necessarily match. In this specification, the sealing body 19 side in the axial direction (height direction) of the cylindrical battery 10 is referred to as "upper," and the bottom 20a side of the outer can 20 in the axial direction is referred to as "lower." Furthermore, among the components described below, components not recited in the independent claims representing the highest concept are optional components and not essential components. Furthermore, the present disclosure is not limited to the following embodiments and their variations, and various improvements and modifications are possible within the scope of the claims of this application and their equivalents.

[0012] Fig. 1 is an axial cross-sectional view of a cylindrical battery 10 according to an embodiment of the present disclosure. As shown in Fig. 1, the cylindrical battery 10 includes an electrode assembly 14, a non-aqueous electrolyte, a bottomed cylindrical outer can 20 that accommodates the electrode assembly 14 and the electrolyte, and a sealing body 19 that closes the opening of the outer can 20. 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. The outer can 20 is a bottomed cylindrical container having a bottom 20a and a cylindrical portion 20b.

[0013] The non-aqueous electrolyte includes, for example, 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 mixed solvents 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 substituted with halogen atoms such as fluorine. The non-aqueous electrolyte is not limited to a liquid electrolyte, and may be a solid electrolyte using a gel polymer or the like. The electrolyte salt may be LiPF ６ Lithium salts such as

[0014] 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, as electrode leads, a positive electrode lead 17 joined to the positive electrode 11 and a negative electrode lead 18 joined to the negative electrode 12. The negative electrode 12 is formed to have dimensions slightly larger than the positive electrode 11 in order to suppress lithium deposition. The two separators 13 are formed to have dimensions at least slightly larger than the positive electrode 11 and are arranged to sandwich the positive electrode 11, for example.

[0015] The positive electrode 11 has a positive electrode core and a positive electrode mixture layer provided on both sides of the positive electrode core. The positive electrode core 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. The positive electrode mixture layer contains a positive electrode active material, a conductive agent, such as acetylene black, and a binder, such as polyvinylidene fluoride (PVDF). The positive electrode 11 can be produced by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder to the positive electrode core, drying the coating, and then compressing it to form a positive electrode mixture layer on both sides of the positive electrode core.

[0016] For example, a lithium transition metal composite oxide is used as the positive electrode active material. Examples of metal elements contained in the lithium transition 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 suitable lithium transition metal composite oxide is a lithium metal composite oxide containing at least one of Ni, Co, and Mn. Specific examples include a composite oxide containing Ni, Co, and Mn, and a composite oxide containing Ni, Co, and Al.

[0017] The negative electrode 12 has a negative electrode core and a negative electrode mixture layer provided on both sides of the negative electrode core. The negative electrode core 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 such as styrene butadiene rubber (SBR). The negative electrode 12 can be produced by applying a negative electrode mixture slurry containing the negative electrode active material and the binder to the negative electrode core, drying the coating, and then compressing it to form a negative electrode mixture layer on both sides of the negative electrode core.

[0018] The negative electrode active material may be, for example, natural graphite such as flake graphite, lump graphite, or amorphous graphite, or artificial graphite such as lump artificial graphite or graphitized mesophase carbon microbeads. The negative electrode active material may be a metal that alloys with lithium, such as Si or Sn, an alloy containing such a metal, or a compound containing such a metal, which may be used in combination with graphite. A suitable example of such an active material is SiO ２ The Si-containing material is a Si-containing material in which fine Si particles are dispersed in a silicate phase such as lithium silicate or an amorphous carbon phase.

[0019] Insulating plates 15 and 16 are disposed above and below the electrode body 14. In the example shown in Fig. 1 , a positive electrode lead 17 attached to the positive electrode 11 passes through a through-hole in the insulating plate 15 and extends toward the sealing body 19, and a negative electrode lead 18 attached to the negative electrode 12 passes outside the insulating plate 16 and extends toward the bottom 20a of the outer can 20. The positive electrode lead 17 is connected by welding or the like to the inner surface of the sealing body 19 facing inward, and the sealing body 19 serves as a positive electrode terminal. The negative electrode lead 18 is connected by welding or the like to the inner surface of the bottom 20a of the outer can 20, and the outer can 20 serves as a negative electrode terminal.

[0020] A gasket 24 is provided between the outer can 20 and the sealing body 19, ensuring sealing of the battery interior and insulation between the outer can 20 and the sealing body 19. The tubular portion 20b includes a tip bent portion 30 bent to extend radially inward around the entire circumference, and a tip tubular portion 31 that is provided axially closer to the bottom 20a than the tip bent portion 30. The tubular portion 20b also includes an annular grooved portion 32 that is provided axially closer to the bottom 20a than the tip tubular portion 31. The grooved portion 32 is a portion of the outer can 20 that protrudes radially inward around the entire circumference, on the bottom 20a side of the tip tubular portion 31 of the tubular portion 20b. The grooved portion 32 is formed by, for example, recessing a portion of the tubular portion 20b radially inward by spinning or the like.

[0021] The bent tip portion 30 extends radially inward and is formed when the upper end of the cylindrical portion 20b is bent radially inward and crimped onto the peripheral edge 33 of the sealing body 19. By this crimping, the sealing body 19 is sandwiched between the bent tip portion 30 and the grooved portion 32 via the gasket 24 and fixed to the outer can 20.

[0022] The sealing body 19 is a disk-shaped member equipped with a current interruption mechanism. The sealing body 19 has a structure in which an internal terminal plate 21, an insulating plate 23, and a rupture plate 22 are stacked in this order from the electrode body 14 side. The internal terminal plate 21 has a thin-walled portion in the center that is thinner than the outer annular portion to which the positive electrode lead 17 is connected.

[0023] The insulating plate 23 is a disk-shaped member made of an insulating material and has an opening 23a in the center. The rupture plate 22 is disposed opposite the internal terminal plate 21, with the insulating plate 23 sandwiched therebetween. The center of the rupture plate 22 is connected to the thin-walled portion in the center of the internal terminal plate 21 through the opening 23a of the insulating plate 23 by welding or the like.

[0024] Furthermore, the rupture plate 22 has an easily breakable portion 22a in the radially intermediate portion. The easily breakable portion 22a is formed by a ring-shaped thin portion 22b formed in a radial portion of the rupture plate 22. The easily breakable portion 22a is formed by forming an annular groove 22c in a radial portion of the inner surface (lower surface in FIG. 1 ) of the rupture plate 22. The groove for forming the easily breakable portion 22a may be formed in the outer surface (upper surface in FIG. 1 ) of the rupture plate 22. A valve portion 22d is formed by a portion of the rupture plate 22 radially inward from the easily breakable portion 22a.

[0025] The sealing body 19 is fixed by crimping to the outer can 20 via a gasket 24, radially outward from the easily breakable portion 22a. The pressure inside the battery acts on the groove 22c of the rupture plate 22 through the vent holes formed in the internal terminal plate 21 and the insulating plate 23.

[0026] When the internal pressure of the battery rises and exceeds a predetermined threshold, the easily breakable portion 22a of the rupture plate 22 breaks, and the valve portion 22d radially inward of the easily breakable portion 22a moves away from the outer can 20.

[0027] In the cylindrical battery 10, the internal terminal plate 21, to which the positive electrode lead 17 is connected, is electrically connected to the rupture plate 22, forming a current path from the electrode body 14 to the rupture plate 22. If an abnormality occurs in the battery and the internal pressure rises, the internal terminal plate 21 breaks, the thin-walled portion of the internal terminal plate 21 is separated from its outer annular portion, and the valve portion 22d deforms so that it protrudes toward the outside of the battery. This interrupts the current path. If the internal pressure of the battery rises further, the fragile portion 22a breaks as described above, forming a gas outlet.

[0028] The structure of sealing body 19 is not limited to the structure shown in Fig. 1. For example, sealing body 19 may be composed of only a rupture plate. Alternatively, sealing body 19 may have a laminated structure including two rupture plates, and may have a convex sealing body cap that covers the rupture plate.

[0029] The structure of the gasket 24 and the method for crimping and fixing the sealing body 19 to the outer can 20 via the gasket 24 will be described in detail below with reference to FIGS. 2 and 3 . FIG. 2 is a cross-sectional view of the gasket 24 before battery assembly. As shown in FIG. 2 , the gasket 24 is formed of resin with a generally L-shaped cross section and a generally circular ring shape. Specifically, before battery assembly, the gasket 24 includes a circular ring-shaped plate portion 41 and a generally cylindrical tube portion 44 extending from the outer periphery of the plate portion 41. The plate portion 41 includes a circular ring-shaped main body plate portion 42 and a circular ring-shaped thin-walled portion 43 that extends radially inward from the bottom 20a (lower side) of the inner circumferential surface of the main body plate portion 42 and is thinner than the main body plate portion. The thin-walled portion 43 forms a covering portion 55 (see FIG. 1 ) that covers the radially inward end of the grooved portion 32 in the cylindrical battery 10. The thin-walled portion 43 constitutes the covering portion 55, thereby reliably preventing a short circuit between the outer can 20 and the sealing body 19.

[0030] An annular protrusion 42a protrudes from the upper surface on the inner circumferential side of the main body plate portion 42. As will be described later, when the gasket 24 is compressed in the axial direction by the tip bent portion 30 extending radially inward of the outer can 20 and the grooved portion 32 via the rupture plate 22, the protrusion 42a is pressed against the lower surface of the rupture plate 22, and the thin-walled portion 43 is deformed downward. At that time, the thin-walled portion 43 can cover the tip of the grooved portion 32 on the radially inner side.

[0031] Furthermore, an easily breakable portion 46 is formed in a facing portion 45 of the tubular portion 44 of the gasket 24 that faces the radially inner side of the front tubular portion 31 of the outer can 20. The easily breakable portion 46 is provided by forming a notch 47 along the entire circumferential direction on the inner peripheral surface of the facing portion 45, and is a thin-walled portion that has a smaller radial thickness than other portions. For example, the notch 47 has a generally V-shaped cross section or a generally linear cross section extending in the radial direction. The easily breakable portion 46 makes it easy to break the gasket 24 so as to separate it into two, upper and lower, parts when the gasket 24 is placed inside the opening of the outer can 20 and the front end of the outer can 20 is bent radially inward, as described below.

[0032] The resin constituting the gasket 24 is not limited to a specific type as long as it can be deformed during crimping. The resin constituting the gasket 24 may also be a material that can be produced by injection molding. Examples of resins that can be used to form the gasket 24 include polypropylene (PP), polybutylene terephthalate (PBT), and perfluoroalkoxyalkane (PFA).

[0033] On the other hand, the outer can 20 is produced, for example, by the following procedure. First, a portion of the cylindrical portion 20b of the outer can 20 is spun to form a recess radially inward, thereby forming a grooved portion 32. Next, the sealing body 19 and the gasket 24 are placed on the grooved portion 32 so that the gasket 24 is positioned between the outer can 20 and the sealing body 19.

[0034] 3(a), in the state where the portion of the cylindrical portion 20b of the outer can 20 that is on the tip side of the grooved portion 32 extends in the axial direction, the gasket 24 is inserted inside the tip side portion, and after the gasket 24 is placed on the grooved portion 32, the tip portion of the cylindrical portion 20b is bent slightly radially inward from the state where it extends in the axial direction. In this state, the gasket 24 is placed adjacent to the inside of the opening of the outer can 20.

[0035] Next, as shown in Figure 3(b), the tip of the cylindrical portion 20b of the outer can 20 is bent radially inward at an angle of 90 degrees or slightly greater than 90 degrees. This forms the tip bent portion 30 and the tip cylindrical portion 31, which is located axially closer to the bottom portion 20a than the tip bent portion 30 and extends in the axial direction. At this time, the outer side of the fragile portion 46 of the gasket 24 is stretched by the tip of the outer can 20, causing tensile stress in the fragile portion 46 and causing it to break. This causes the gasket 24 to separate in the axial direction via the gap G1.

[0036] Next, as shown in FIG. 3( c), from a state in which the gasket 24 is separated in the axial direction via the gap G1, the gasket 24 is compressed in the axial direction with the peripheral portion 33 of the rupture plate 22 sandwiched between the tip bent portion 30 and the upper portion of the grooved portion 32. As a result, the gasket 24 is compressed in the axial direction so as to be sandwiched between the tip bent portion 30 and the grooved portion 32. At this time, the gap between the separated portions of the gasket 24 becomes smaller. Therefore, the gasket 24 is sandwiched in the axial direction between the tip bent portion 30 and the grooved portion 32. The tip bent portion 30 is further bent downward and crimped to the peripheral portion 33 of the rupture plate 22, thereby completing the cylindrical battery 10. The bending of the tip of the tubular portion 20b and the compression of the gasket 24 can be performed by machining.

[0037] As shown in FIG. 3( c), when the cylindrical battery 10 is assembled, the gasket 24 is positioned adjacent to the inside of the opening including the bent tip portion 30 and the tubular tip portion 31. In this state, a discontinuous portion 48 that can be separated in the axial direction is formed in the facing portion 45 of the gasket 24 that faces the radially inner side of the tubular tip portion 31 of the outer can 20. In the example of FIG. 3( c), the axially facing surfaces of the gasket 24 at the discontinuous portion 48 are in contact with each other only partially, and gaps G2, G3 are formed between the facing surfaces. Each gap G2, G3 is a notched space formed around the entire circumferential direction of the gasket 24. The gap may be formed only at either the radially outer end portion or the radially inner end portion. Alternatively, the axially facing surfaces at the discontinuous portion 48 may be in contact with each other over the entire area. In this case, no gap is formed between the opposing surfaces, but the gasket 24 can remain separable into an upper portion and a lower portion at the discontinuous portion 48, so that the discontinuous portion 48 relieves stress inside the gasket 24 and reduces stress concentration at the corners of the outer can 20. However, the formation of the gap at the discontinuous portion 48 significantly exerts the above-mentioned effect. The opposing surfaces at the discontinuous portion 48 may be completely separated from each other.

[0038] Furthermore, curved surface portions S1, S2 having an arc-shaped cross section are formed on one or both of the opposing surfaces of the discontinuous portion 48 of the gasket 24.

[0039] In the cylindrical battery 10 described above, the opposing portion 45 of the gasket 24 has a discontinuous portion 48 formed therein that is separable in the axial direction. Furthermore, in the manufacturing method for the cylindrical battery described above, the gasket 24 is compressed in the axial direction via the bent tip portion 30 while being separable in the axial direction. This reduces the stress applied from the gasket 24 to the corners of the outer can 20 when the gasket 24 is compressed by the tip of the outer can 20 when the tip of the outer can 20 is crimped onto the peripheral edge 33 of the sealing body 19. This reduces stress concentration at the corners of the outer can 20, thereby preventing damage to the corners. Furthermore, the formation of a gap between the opposing surfaces of the discontinuous portion 48 significantly enhances the above-described effects.

[0040] Furthermore, the facing portion 45 of the gasket 24, where the gaps G2 and G3 are formed, is a portion where tensile stress is likely to occur in the gasket 24 due to bending of the front end portion of the outer can 20. Therefore, by providing the easily breakable portion 46 in the facing portion 45, the easily breakable portion 46 is more likely to break due to tensile stress. It is more preferable to provide the easily breakable portion 46 in the portion of the facing portion 45 of the gasket 24 that faces the outer peripheral surface of the sealing body 19.

[0041] Furthermore, curved surface portions S1, S2 having an arc-shaped cross section are formed on at least one of the opposing surfaces of the portions of the gasket 24 that are separated in the axial direction by gaps G2, G3. This makes it easier to form gaps G2, G3 in the discontinuous portion 48 of the gasket 24.

[0042] Furthermore, in the manufacturing method for the cylindrical battery of this example, before compressing the gasket 24 in the axial direction, an easily breakable portion 46 is formed in the gasket 24 in the facing portion 45 that faces the front tube portion 31. Then, when the front end of the outer can 20 is bent, the easily breakable portion 46 breaks, causing the gasket 24 to separate in the axial direction via the gap G1, and the gasket 24 is then compressed in the axial direction via the front bent portion 30. This allows the gasket 24 to be handled as a single, inseparable component before being assembled into the battery, thereby improving manufacturing workability.

[0043] FIG. 4 is an enlarged cross-sectional view corresponding to portion A in FIG. 1 , showing damage to the outer can 20 of a comparative cylindrical battery after the gasket 24a is assembled into the outer can 20, the front end of the outer can 20 is bent, and the gasket 24a is further compressed in the axial direction. In the comparative example, the gasket 24a does not have a discontinuous portion that can be separated in the axial direction via a gap at the facing portion 45a of the gasket 24a that faces the radially inward side of the front tubular portion 31 of the outer can 20. Consider the case where the front end of the outer can 20 is bent and crimped to the sealing body 19 via the gasket 24a in this comparative example. In this case, stress from the gasket 24a tends to concentrate at the corner 34 of the outer can 20, for example, at the position indicated by arrow P in FIG. 4( b). Therefore, when the cylindrical battery 10 is used under harsh conditions, such as when subjected to high vibrations, damage may occur at the corner 34 of the outer can 20, for example, at the portion indicated by the dashed line B in FIG. 4( b). According to the embodiment shown in FIGS. 1 to 3, stress concentration at the corners of the outer can can be reduced, thereby preventing such inconvenience.

[0044] 1 to 3, the facing portion 45 of the gasket 24 has a notch 47 formed in the inner peripheral surface thereof, thereby providing the easily breakable portion 46 in the facing portion 45. On the other hand, the facing portion of the gasket may have a notch having a substantially V-shaped cross section or the like formed in the outer peripheral surface thereof, thereby providing the easily breakable portion in the facing portion.

[0045] FIG. 5 is a view corresponding to FIG. 3 of a cylindrical battery according to another embodiment. In this configuration, the gasket 24b does not have a fragile portion before being assembled into the cylindrical battery. Instead, the gasket 24b is completely separated into two parts, an upper portion 60 and a lower portion 61, before being assembled into the cylindrical battery. For example, the lower portion 61 has a shape in which the plate portion 41 and the base end of the tubular portion 44 of the gasket 24 shown in FIG. 2 are integrally formed. The upper portion 60 has a shape similar to that of the gasket 24 shown in FIG. 2, excluding the base end of the tubular portion 44 and the plate portion 41. When performing crimping of the outer can 20, as shown in FIG. 5(a), the lower portion 61 of the gasket 24b is inserted inside the tip tubular portion 31 of the outer can 20, and then the rupture plate 22 is placed on the lower portion 61.

[0046] Next, with the upper portion of the gasket 24b inserted inside the cylindrical portion 20b of the outer can 20, as shown in FIG. 5(b), the front end of the outer can 20 is bent radially inward by 90 degrees or more to form the bent front end portion 30. At this time, the bent portion of the front end of the outer can 20 deforms the upper portion 60 so as to push it radially inward, thereby forming a gap G1 between the upper portion 60 and the lower portion 1. Alternatively, the front end of the outer can 20 may be bent radially inward while the upper portion 60 is being lifted upward, thereby forming the gap G1. Next, as shown in FIG. 5(c), the bent front end portion 30 and the grooved portion 32 compress the gasket 24b in the axial direction via the rupture plate 22.

[0047] In a cylindrical battery using this type of alternative gasket 24b, as shown in FIG. 5(c), a discontinuous portion 48b that can be separated in the axial direction can be formed in the gasket 24b at the facing portion 45b that faces the radially inner side of the tubular tip portion 31 of the outer can 20. This allows the discontinuous portion 48b to relieve stress on the gasket 24b, thereby reducing the stress applied from the gasket 24b to the corner portion 34 of the outer can 20. This reduces stress concentration at the corner portion 34. In this example, the other configurations and functions are the same as those in FIGS. 1 to 3.

[0048] REFERENCE SIGNS LIST 10 Cylindrical battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15, 16, 23 Insulating plate, 17 Positive electrode lead, 18 Negative electrode lead, 19 Sealing body, 20 Outer can, 20a Bottom, 20b Cylindrical portion, 21 Internal terminal plate, 22 Rupture plate, 22a Easily breakable portion, 22b Thin portion, 22c Groove, 22d Valve portion, 23a Opening, 24, 24a, 24b Gasket, 30 Tip bent portion, 31 Tip cylindrical portion, 32 Grooved portion, 33 Peripheral portion, 34 Corner portion, 41 Plate portion, 42 Main body plate portion, 42a Protrusion, 43 Thin portion, 44 Cylindrical portion, 45, 45a, 45b Opposing portion, 46 Easily breakable portion, 47 Notch, 48, 48b: discontinuous portion, 55: covering portion, 60: upper portion, 61: lower portion.

Claims

1. A cylindrical battery comprising: an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; a bottomed, cylindrical exterior can containing the electrode assembly; and a sealing body that is crimped and fixed to an opening of the exterior can via a gasket, wherein the exterior can includes a bent tip portion that is bent so as to extend radially inward at the opening adjacent to the gasket, and a tip tubular portion that extends in the axial direction, and the gasket has a discontinuous portion that is axially separable at an opposing portion that faces the radially inward side of the tip tubular portion.

2. The cylindrical battery according to claim 1, wherein the gasket has the discontinuous portion in a portion of the facing portion that faces the outer circumferential surface of the sealing body.

3. The cylindrical battery according to claim 1, wherein the gasket has a gap formed between opposing surfaces that face each other in the axial direction at the discontinuous portion.

4. The cylindrical battery according to claim 1, wherein at least one of the axially opposing surfaces of the gasket in the discontinuous portion is formed with a curved portion having an arc-shaped cross section.

5. The cylindrical battery according to claim 1, wherein the outer can has a grooved portion formed so as to protrude radially inward from the tip tube portion on the axial bottom side, and the gasket is sandwiched in the axial direction between the tip bent portion and the grooved portion.

6. A method for manufacturing a cylindrical battery comprising: an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; a bottomed, tubular outer can containing the electrode assembly; and a sealing body that is crimped and fixed to the opening of the outer can via a gasket, comprising: arranging the gasket adjacent to the inside of the opening of the outer can; bending the tip of the outer can from a state in which it extends in the axial direction to face radially inward by more than 90 degrees to form a tip bent portion and a tip tubular portion that is located on the bottom side of the tip bent portion and extends in the axial direction; and compressing the gasket in the axial direction via the tip bent portion from a state in which the gasket is separated in the axial direction via a gap at an opposing portion that faces the radially inward of the tip tubular portion.

7. A method for manufacturing a cylindrical battery as described in claim 6, wherein an easily breakable portion is formed in the gasket in advance at the opposing portion before the gasket is compressed in the axial direction, and the gasket is compressed in the axial direction via the bent tip portion from a state in which the gasket is separated in the axial direction via the gap due to the easily breakable portion being broken by bending the tip of the outer can.

8. The method for manufacturing a cylindrical battery as set forth in claim 7, wherein the easily breakable portion is formed in a portion of the facing portion that faces the outer circumferential surface of the sealing body.

9. A method for manufacturing a cylindrical battery as described in claim 6, wherein the outer can has a grooved portion formed so as to protrude radially inward on the bottom side in the axial direction from the tip tube portion, and the gasket is compressed in the axial direction so as to be sandwiched between the tip bent portion and the grooved portion.

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