Cylindrical secondary battery

Abstract

This cylindrical secondary battery (10) includes an electrode group (14), a current collector which is connected to the electrode group, a sealing body (19) which is disposed on the upper side of the electrode group and to which the current collector is connected, and a bottomed cylindrical battery can (20) which houses the electrode group. The sealing body is fixed to the inside of the opening-side end of the battery can in the axial direction, and closes the opening of the battery can. A cap (40) is attached to the opening-side end of the battery can. The cap has: a cylinder part (41) which has a female screw (43) on the inner peripheral surface; and a pressing plate part (42) that is continuous with one end of the cylinder part and is pressed against the outer side of the opening-side end of the battery can in the axial direction. The battery can has a male screw (53) on the outer peripheral surface. The battery can and the cap are screw-coupled with each other by means of the female screw and the male screw.

Description

Cylindrical secondary battery

[0001] The present disclosure relates to a cylindrical secondary battery, and more particularly to improving the pressure resistance of a battery that includes a cylindrical battery can with a bottom and a sealing body that functions as an electrode terminal.

[0002] Conventionally, cylindrical secondary batteries have been known that include an electrode group, a cylindrical battery can with a bottom that houses the electrode group, and a sealing body that closes the opening of the battery can. The electrode group is connected to the sealing body via a current collector. This allows the sealing body to function as an electrode terminal. Furthermore, Patent Document 1 describes a cylindrical secondary battery in which the sealing body is crimped and fixed to the end of the battery can via an insulating resin gasket, thereby closing the opening of the battery can with the sealing body.

[0003] Japanese Patent Application Laid-Open No. 2008-204839

[0004] In a cylindrical secondary battery having an opening of the battery can sealed by a sealing body, as in the configuration described in Patent Document 1, the opening end of the battery can is crimped and the sealing body is crimped and fixed to this opening end to prevent the sealing body from coming off the battery can due to an increase in internal pressure caused by a battery abnormality such as an internal short circuit.

[0005] On the other hand, in recent years, there has been a demand for the development of batteries with higher energy densities. Increasing the energy density of a battery increases the internal pressure when a battery malfunction occurs. This can lead to the crimped portion at the open end of the battery can opening, potentially causing the closed opening of the battery can to open unexpectedly. This has led to a demand for improved pressure resistance of batteries.

[0006] Therefore, an object of the present disclosure is to provide a cylindrical secondary battery that can improve pressure resistance in a configuration in which the opening of a bottomed cylindrical battery can is closed by a sealing body that also functions as an electrode body.

[0007] The cylindrical secondary battery according to the present disclosure includes an electrode group in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, a current collector connected to the electrode group, a sealing body arranged above the electrode group, to which the current collector is connected and which functions as an electrode terminal, and a bottomed cylindrical battery can that houses the electrode group, wherein the sealing body is fixed to the axially inner side of the open end of the battery can and closes the opening of the battery can, and a cap is attached to the open end of the battery can, the cap having a tubular portion with a female thread on its inner peripheral surface and a pressing plate portion that is continuous from one end of the tubular portion and extends radially inward along the radial direction and is pressed against the axially outer side of the open end of the battery can, and the battery can has a male thread on its outer peripheral surface, and the battery can and the cap are screwed together by the female thread and the male thread.

[0008] In the cylindrical secondary battery according to the present disclosure, the opening of a cylindrical battery can with a bottom is closed by a sealing body that also functions as an electrode terminal, and the sealing body is attached to the open end of the battery can by screwing a cap, and the pressing plate of the cap is pressed axially outward against the open end of the battery can, thereby improving the pressure resistance of the cylindrical secondary battery.

[0009] It is an axial cross-sectional view of a cylindrical secondary battery according to an embodiment of the present disclosure. It is an enlarged view of part A in Fig. 1. It is an axial cross-sectional view of a cylindrical secondary battery according to another embodiment. It is an enlarged cross-sectional view of the periphery of a grooved portion in Fig. 3.

[0010] Hereinafter, with reference to the drawings, an embodiment of a cylindrical secondary battery according to the present disclosure will be described in detail. Note that the cylindrical secondary battery according to the present disclosure may be a battery using an aqueous electrolyte or a battery using a nonaqueous electrolyte. Hereinafter, a nonaqueous electrolyte secondary battery (lithium ion battery) using a nonaqueous electrolyte will be exemplified as a cylindrical secondary battery according to one embodiment, but the cylindrical secondary battery according to the present disclosure is not limited thereto, and the electrolyte may 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, identical components are designated by the same reference numerals in the drawings, and redundant descriptions 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 axial direction of the sealing body 19 of the cylindrical secondary battery 10 is referred to as "upper," and the axial direction of the bottom 20a of the battery can 20 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 variations thereof, and various improvements and modifications are possible within the scope of the claims and their equivalents.

[0012] Fig. 1 shows an axial cross-sectional view of a cylindrical secondary battery 10 according to an embodiment of the present disclosure. Fig. 2 is an enlarged view of portion A in Fig. 1. The axial cross-sectional view in Fig. 1 shows a cross-section including the central axis of the cylindrical secondary battery 10. As shown in Fig. 1, the cylindrical secondary battery 10 includes an electrode group 14, a non-aqueous electrolyte, a battery can 20 which is a cylindrical metal container with a bottom that accommodates the electrode group 14 and the non-aqueous electrolyte, a sealing body 19 that closes the opening of the battery can 20, a gasket 30, and a cap 40.

[0013] The electrode group 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 battery can 20 has a bottom 20a and a cylindrical portion 20b.

[0014] The non-aqueous electrolyte has ion conductivity (e.g., lithium ion conductivity). The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous electrolyte is not limited to a liquid electrolyte (nonaqueous electrolytic solution), and may be a solid electrolyte using a gel polymer or the like. The cylindrical secondary battery 10 is preferably a lithium ion battery. The electrolyte salt may be, for example, LiBF ４ , LiPF ６Examples of the non-aqueous solvent include esters such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl propionate (MP), ethers, nitriles, amides, and mixed solvents of two or more of these. The non-aqueous solvent may contain a halogen-substituted product in which at least a portion of the hydrogen atoms of these solvents are substituted with halogen atoms such as fluorine.

[0015] Examples of halogen-substituted compounds include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated chain carbonates, and fluorinated chain carboxylic acid esters such as methyl fluoropropionate (FMP). From the viewpoint of suppressing a decrease in the charge-discharge cycle characteristics of a cylindrical secondary battery or improving input characteristics, the non-aqueous electrolyte preferably contains 5% by mass or more of FEC, and more preferably 5% by mass to 15% by mass of FEC, relative to the mass of the non-aqueous electrolyte.

[0016] Examples of the solid electrolyte include solid or gel polymer electrolytes and inorganic solid electrolytes. The polymer electrolyte includes, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt, and a matrix polymer. Examples of the matrix polymer include a polymer material that absorbs the non-aqueous solvent and gels. Examples of the polymer material include fluororesin, acrylic resin, and polyether resin. Examples of the inorganic solid electrolyte include materials known in all-solid-state lithium ion secondary batteries (e.g., oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.).

[0017] As described above, the electrode group 14 has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound with the separator 13 interposed therebetween. The positive electrode 11, the negative electrode 12, and the separator 13 are all long, strip-like bodies that are spirally wound and alternately stacked in the radial direction of the electrode group 14. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium deposition. That is, the negative electrode 12 is formed to be longer in both the longitudinal and lateral directions than the positive electrode 11. The separator 13 is formed to be at least slightly larger than the positive electrode 11, and, for example, two separators 13 are arranged to sandwich the positive electrode 11.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] Insulating plates 15 and 16 are disposed above and below the electrode group 14. In the example shown in FIG. 1 , a positive electrode current collector 17 attached to the positive electrode 11 passes through a through-hole in the insulating plate 15 and extends toward the sealing body 19, while a negative electrode current collector 18 attached to the negative electrode 12 passes outside the insulating plate 16 and extends toward the bottom 20a of the battery can 20. The positive electrode current collector 17 and the negative electrode current collector 18 are each formed into a long plate shape from a conductive material. The positive electrode current collector 17 is connected to the inner surface of the sealing body 19 facing inward of the battery can 20 by welding or the like, and the sealing body 19 functions as a positive electrode terminal. The negative electrode current collector 18 is connected to the inner surface of the bottom 20a of the battery can 20 by welding or the like, and the battery can 20 functions as a negative electrode terminal.

[0023] An annular gasket 30 is interposed between the battery can 20 and the sealing body 19 to ensure the sealing of the inside of the battery and the insulation between the battery can 20 and the sealing body 19 .

[0024] A radially bent portion 20c that is bent radially inward around the entire circumference is formed at the upper end portion, which is the end portion on the opening side of the battery can 20, and the sealing body 19 is thereby fixed by crimping to the upper end portion of the battery can 20 via a gasket 30. In this way, the sealing body 19 is fixed to the axially inner side of the upper end portion of the battery can 20.

[0025] An annular grooved portion 24 is provided at the upper end, which is the axial opening end side, of the cylindrical portion 20b of the battery can, closer to the bottom portion 20a than the radially bent portion 20c. The grooved portion 24 is a portion that protrudes radially inward around the entire circumference in a portion adjacent to the lower side of the opening-side cylindrical portion 20d provided at the upper end side of the cylindrical portion 20b of the battery can 20. The grooved portion 24 is formed by, for example, recessing a portion of the cylindrical portion 20b radially inward by spinning or the like. The grooved portion 24 supports the sealing body 19 (described below) via a gasket 30. In FIG. 2 , the outer diameter of the opening-side cylindrical portion 20d is smaller than the outer diameter of the portion of the cylindrical portion 20b below the grooved portion 24. The opening-side cylindrical portion 20d is a portion of the battery can 20 that is fitted inside the cap 40 (described below). The outer diameter of the opening-side cylindrical portion 20d may be the same as or larger than the outer diameter of the portion of the cylindrical portion 20b below the grooved portion 24.

[0026] An elastic insulating resin can be used for the gasket 30. Examples of such resins include polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), perfluoroalkoxy fluororesin (PFA), nylon, etc.

[0027] Gating body 19 is a disk-shaped member equipped with a current interruption mechanism. Gating 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 group 14 side. Internal terminal plate 21 has a thin-walled portion in the center that is thinner than the outer annular portion to which positive electrode current collector 17 is connected.

[0028] 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 via the insulating plate 23. 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, thereby establishing electrical continuity.

[0029] Furthermore, the rupture plate 22 has an easily breakable portion 22a in the radially intermediate portion. The easily breakable portion 22a is a ring-shaped thin portion formed by a ring-shaped groove formed on 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 on the outer surface (upper surface in FIG. 1 ) of the rupture plate 22. The pressure inside the battery acts on the ring-shaped groove of the rupture plate 22 through vent holes formed in the internal terminal plate 21 and the insulating plate 23.

[0030] When the internal pressure of the battery rises and reaches or exceeds a predetermined threshold, the second predetermined pressure described below, the rupture plate 22 deforms outward, the easily breakable portion 22a breaks, and the radially inner portion of the easily breakable portion 22a moves away from the battery can 20.

[0031] In the cylindrical secondary battery 10, the internal terminal plate 21, to which the positive electrode current collector 17 is connected, is electrically connected to the rupture plate 22, thereby forming a current path from the electrode group 14 to the rupture plate 22. If an abnormality occurs in the battery and the internal pressure rises above a first predetermined pressure, the internal terminal plate 21 breaks, and the thin-walled portion of the internal terminal plate 21 is separated from its outer annular portion and deformed to become convex toward the outside of the battery. This interrupts the current path. If the internal pressure of the battery further rises above a second predetermined pressure that is greater than the first predetermined pressure, the easily breakable portion 22a breaks as described above, forming an opening for venting gas inside the battery. The gas released from this opening is discharged to the outside of the battery through an opening 42a formed in the cap 40, which will be described later.

[0032] The structure of sealing body 19 is not limited to the structure shown in Fig. 1. For example, a cap having a gas vent hole may be placed on the outside of the rupture plate and crimped together with the rupture plate to the open end of battery can 20.

[0033] As described above, in a configuration in which the opening of the battery can 20 is closed by the sealing body 19, there is a possibility that the internal pressure will increase if a battery abnormality occurs when the energy density is increased, and therefore improvement in pressure resistance is desired. For this reason, in this embodiment, a cap is attached to the end of the opening side of the battery can 20, and a pressing plate portion of the cap is pressed axially outwardly against the upper end of the battery can, and the cap and the battery can 20 are screwed together.

[0034] Specifically, a cap 40 is attached to the upper end, which is the open end, of the battery can 20, and the cap 40 is pressed against the axially outward side of the upper end of the battery can. The cap 40 is formed from a metal such as steel or an aluminum alloy, and has a cylindrical tube portion 41 and an annular plate-shaped pressing plate portion 42 that is continuous with one end of the tube portion 41, extends radially inward in the radial direction, and is pressed against the axially outward side of the radially bent portion 20c at the upper end of the battery can 20. An opening 42a is formed in the pressing plate portion 42 to expose the upper surface of the circular sealing body 19.

[0035] 2 , a female thread 43 is formed on the inner circumferential surface of the cylindrical portion 41 of the cap 40. The female thread 43 is threadedly coupled to a male thread 53 (described later) formed on the battery can 20. The female thread 43 is formed on the inner circumferential surface of the cylindrical portion 41 of the cap 40 from the lower end to the middle in the vertical direction. The battery can 20 and the cap 40 are threadedly coupled to each other via the female thread 43 and the male thread 53, thereby attaching the cap 40 to the upper end of the battery can 20. With this cylindrical secondary battery 10, the pressure resistance can be improved in a configuration in which the opening of the bottomed cylindrical battery can 20 is closed by the sealing body 19.

[0036] Specifically, when the cap 40 is threadedly coupled to the battery can 20 using the male thread 53 of the battery can 20 and the female thread 43 of the cap 40, the multiple threads of the male thread 53 and the multiple threads of the female thread 43 engage in the axial direction at the threaded coupling portion, and the tightening of the male thread 53 and the female thread 43 causes the threads to deform so as to bite into each other in the circumferential direction. As a result, when a force acts to separate the battery can 20 and the cap 40 in the axial direction, resistance to the force is increased. Therefore, even if the internal pressure of the battery increases and a force is applied to the sealing body 19 to separate it axially outward from the battery can 20, separation of the cap 40 and the sealing body 19 from the battery can 20 can be prevented.

[0037] Furthermore, in this embodiment, a radially bent portion 20c bent radially inward is formed at the upper end of the battery can 20, and the sealing body 19 is crimped and fixed to this upper end via a gasket 30. The inner surface of the pressing plate portion 42 of the cap 40 is pressed against the outer surface of the radially bent portion 20c. As a result, even if the internal pressure of the battery increases as described above and a force is applied to the radially bent portion 20c from the sealing body 19 side to push the battery can 20 outward in the axial direction, the pressing plate portion 42 of the cap 40 suppresses outward deformation of the upper end of the battery can 20. This more firmly suppresses detachment of the sealing body 19 from the battery can 20, thereby improving the pressure resistance of the cylindrical secondary battery 10.

[0038] Furthermore, as described above, when the internal pressure of the battery rises to or exceeds the second predetermined pressure, high-pressure gas generated inside the battery can be appropriately released through the inside of the opening 42 a of the cap 40. Even in this case, it is possible to prevent the cap 40 and the sealing body 19 from unexpectedly coming off from the battery can 20.

[0039] The female thread 43 may be provided in a height range T2 that is 50% or more of the axial height T1 on the inner circumferential surface of the cylindrical portion 41 of the cap 40. This increases the joining strength between the battery can 20 and the cap 40 at the threaded joint.

[0040] Meanwhile, a male thread 53 is formed on the outer peripheral surface of the opening-side tubular portion 20d of the battery can 20, which is fitted inside the cap 40. The male thread 53 may be provided in a height range T4 that is 50% or more of the axial height T3 of the opening-side tubular portion 20d. This also increases the bonding strength between the battery can 20 and the cap 40 via the threaded coupling. Furthermore, to increase the bonding strength between the battery can 20 and the cap 40, a configuration may be adopted in which the female thread 43 is provided in a height range T2 that is 50% or more of the axial height T1 on the inner peripheral surface of the tubular portion 41 of the cap 40, and the male thread 53 is provided in a height range T4 that is 50% or more of the axial height T3 of the opening-side tubular portion 20d.

[0041] To assemble the cylindrical secondary battery 10, first, the lower insulating plate 16, the electrode group 14, and the upper insulating plate 15 are housed within the cylindrical portion 20b of the battery can 20 while the cylindrical portion 20b is extended in the axial direction. Then, a circular groove 24 with a generally U-shaped cross section that protrudes radially inward is formed in a portion of the upper end of the cylindrical portion 20b by spinning or other processing. After an electrolyte is injected into the inside of the cylindrical portion 20b from above, the sealing body 19 and the gasket 30 are placed above the groove 24 within the cylindrical portion 20b, and the upper end of the cylindrical portion 20b is crimped radially inward along its entire circumference, thereby forming a radially bent portion 20c at the upper end of the battery can 20. This crimps the sealing body 19 to the upper end of the battery can 20 via the gasket 30. Thereafter, the cap 40 is screwed onto the upper end of the battery can 20 from above, and the pressing plate portion 42 of the cap 40 is pressed against the axially outer side of the radially bent portion 20c of the battery can 20. In this way, the cylindrical secondary battery 10 is formed.

[0042] According to the cylindrical secondary battery 10 described above, the cap 40 is attached to the open end of the battery can 20 by screw connection, and the pressing plate portion 42 of the cap 40 is pressed against the axially outward side of the open end of the battery can 20. This improves the pressure resistance of the cylindrical secondary battery 10.

[0043] Although not shown in the drawings, in another embodiment, a crimped portion may be formed on the cap after a radially bent portion is formed by crimping on the upper end of the battery can. For example, in the configuration shown in Figures 1 and 2, with the sealing body 19 crimped and fixed to the battery can 20 by the radially bent portion 20c, the cap 40 may be screwed onto the upper end of the battery can 20, and then the lower end, which is the tip of the cap 40, may be crimped around the entire circumference radially toward the inside of the grooved portion 24. This allows the cap 40 to be fixed to the battery can 20 even more firmly.

[0044] Fig. 3 is an axial cross-sectional view of a cylindrical secondary battery 10a according to another embodiment of the present invention, and Fig. 4 is an enlarged cross-sectional view of the periphery of a grooved portion 24 in Fig. 3 .

[0045] In the cylindrical secondary battery 10a of this example, the sealing body 19a is configured to include an upper current collecting plate 60, a terminal cap 70, and a metal plate 61. The terminal cap 70 is a metal plate-like member without a through hole, has a flange on the outer periphery, has an outer periphery that slopes upward in the center so that the diameter decreases, and is hat-shaped with a convex portion that is closed at the upper end.

[0046] The upper current collector 60 is a metal annular plate member having a through-hole 60a in the radially central portion. The upper current collector 60 corresponds to a positive electrode current collector. An annular recess 65 is formed on the radially inner side of the upper surface of the upper current collector 60. The lower surface of the flange of the terminal cap 70 is electrically connected to the radially outer side of the upper surface of the upper current collector 60, for example, by laser welding. As a result, the sealing body 19a has a laminated portion 64 on its outer periphery, where the terminal cap 70 and the upper current collector 60 are laminated. This outer periphery is fixed to the upper end of the battery can 20 by crimping via a gasket 30a, as described below.

[0047] The upper end of the protrusion of the terminal cap 70 protrudes upward through an opening provided in the center of the cap 40a (described later) and is exposed to the outside. The exposed portion of the upper end surface of the terminal cap 70 constitutes the positive electrode terminal.

[0048] The metal plate 61 is a metal annular member having a cylindrical through-hole 61 a. The metal plate 61 is disposed between the lower surface of the flange of the terminal cap 70 and the upper surface of the recess 65 of the upper current collecting plate 60.

[0049] Furthermore, a plurality of (e.g., eight) positive electrode leads 17a are connected to a plurality of positions (e.g., eight positions) in the longitudinal direction corresponding to the winding direction of the positive electrode 11 (see FIG. 1), and the plurality of positive electrode leads 17a are led out upward from the upper end of the electrode group 14. In FIG. 3, the electrode group 14 is illustrated in a simplified manner.

[0050] The upper ends of the multiple positive electrode leads 17a are led outward through the through holes in the upper insulating plate 15, and the radially outwardly bent portions of the upper ends of the positive electrode leads 17a are sandwiched between the upper surface of the recess 65 of the upper current collector plate 60 and the metal plate 61. In this state, each positive electrode lead 17a is joined to the upper surface of the upper current collector plate 60. The upper current collector plate 60 and the metal plate 61 are also joined, and each positive electrode lead 17a and the metal plate 61 are also joined. These joinings can be achieved, for example, by laser welding the tip end of each positive electrode lead 17a sandwiched between the upper current collector plate 60 and the metal plate 61 by irradiating the metal plate 61 with a laser beam in the axial direction from above. By laser welding the tip end of the positive electrode lead 17a sandwiched between the upper current collector plate 60 and the metal plate 61, the positive electrode lead 17a can be reliably and easily welded and joined to the upper current collector plate 60.

[0051] The upper current collector 60 does not have to be joined to the metal plate 61, and the positive electrode lead 17a does not have to be joined to the metal plate 61. In addition, in a cylindrical secondary battery, the positive electrode lead 17a may be joined to the upper current collector 60 without having the metal plate 61. In addition, the positive electrode lead 17a may be joined to the lower surface of the upper current collector 60.

[0052] The negative electrode 12 (see FIG. 1 ) is connected to the bottom 20 a of the battery can 20 via a negative electrode current collector 76. Specifically, the negative electrode current collector 76, which is a metal plate-shaped member, is disposed on the upper surface of the bottom 20 a. A strip-shaped negative electrode core exposed portion (not shown) is provided at the lower end of the negative electrode 12, extending from the end at the start of winding in the longitudinal direction to the end at the end at the end of winding. In the negative electrode core exposed portion, the portion of the electrode group 14 extending below the lower ends of the positive electrode 11 and separator 13 (see FIG. 1 ) is tilted radially inward, and the electrode group 14 is pressed against the upper surface of the negative electrode current collector 76. In this state, the negative electrode core exposed portion is joined to the upper surface of the negative electrode current collector 76 by laser welding, for example, by irradiating the lower surface of the negative electrode current collector 76 with a laser beam. Furthermore, the negative electrode current collector 76 is joined to the bottom 20a of the battery can 20 by laser welding, for example, by irradiating the bottom 20a with laser light from below.

[0053] The cylindrical secondary battery 10a has a thin, easily breakable portion 20e on the bottom 20a of the battery can 20. The easily breakable portion 20e is formed, for example, by stamping a circle or a C-shape on the underside of the bottom 20a. If the easily breakable portion 20e is provided on the bottom 20a, when the cylindrical secondary battery 10a generates abnormal heat, the easily breakable portion 20e breaks, allowing high-temperature gas inside the cylindrical secondary battery 10a to be discharged to the outside. The thin, easily breakable portion may also be provided on the terminal cap 70.

[0054] Furthermore, a radially bent portion 20c that is bent radially inward is formed at the upper end of the battery can 20, and the outer peripheral edge of the sealing body 19a is crimped and fixed to this upper end via a gasket 30a.

[0055] A cap 40a is attached to the upper end of the battery can 20 by screwing. The cap 40a continues from the upper end of the cylindrical portion 82, extends radially inward, and has a circular pressing plate portion 81 that is pressed against the axially outer side of the radially bent portion 20c at the upper end of the battery can 20. In this example, the pressing plate portion 81 extends radially inward from the radially inner end of the radially bent portion 20c to near the outer peripheral surface of the convex portion of the terminal cap 70. The cap 40a is screwed to the battery can 20 by a female thread 43a ( FIG. 4 ) provided on the inner peripheral surface of the cylindrical portion 82 of the cap 40a and a male thread 53a ( FIG. 4 ) provided on the outer peripheral surface of the opening-side cylindrical portion 20d of the battery can 20.

[0056] When multiple cylindrical secondary batteries 10a are electrically connected to form a battery module, for example, an external lead (not shown) is joined to the pressing plate portion 81 of the cap 40a, which serves as the negative electrode terminal, or to the upper surface of the protruding portion of the terminal cap 70, which serves as the positive electrode terminal. In this example, the pressing plate portion 81 extends radially inward beyond the radially bent portion 20c of the battery can 20. This makes it easier to join the external lead to the negative electrode terminal when multiple cylindrical secondary batteries 10a are electrically connected to form a battery module than when the radially bent portion 20c serves as the negative electrode terminal without using the cap 40a. In this example, the other configurations and functions are the same as those in FIGS. 1 and 2 .

[0057] In each of the above embodiments, a configuration has been described in which the sealing bodies 19, 19a are crimped and fixed to the upper end of the battery can 20, but the sealing bodies 19, 19a may be fixed to the battery can 20 by a method other than crimping, as long as the sealing bodies 19, 19a can be fixed to the axially inner side of the upper end of the battery can 20.

[0058] Furthermore, in the configurations of the above-described embodiments, the case has been described in which the male threads 53, 53a are provided on the outer peripheral surface of the opening-side cylindrical portion 20d of the battery can 20. On the other hand, the axial height of the cylindrical portion of the cap 40 shown in Figures 1 and 2 may be greater than that of the configurations shown in Figures 1 and 2, and the inner and outer diameters of the cylindrical portion may be increased, so that the battery can 20 and the cap 40 are threadably coupled together by a female thread formed on the inner peripheral surface of the cylindrical portion and a male thread formed on the outer peripheral surface of the cylindrical portion 20b of the battery can 20 below the grooved portion 24.

[0059] Furthermore, in the configuration of the present disclosure, the pressing plate portion of the cap is not limited to a circular plate-shaped portion, and may be configured, for example, such that an opening for connecting an external lead to the sealing body 19, 19a is formed in a part of the circular plate portion.

[0060] REFERENCE SIGNS LIST 10, 10a Cylindrical secondary battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode group, 15, 16 Insulating plate, 17 Positive electrode current collector, 17a Positive electrode lead, 18 Negative electrode current collector, 19, 19a Sealing body, 20 Battery can, 20a Bottom, 20b Cylindrical portion, 20c Radial bending portion, 20d Opening side cylindrical portion, 20e Easy-to-break portion, 21 Internal terminal plate, 22 Rupture plate, 22a Easy-to-break portion, 23 Insulating plate, 24 Grooved portion, 30, 30a Gasket, 40, 40a Cap, 41 Cylindrical portion, 42 Pressing plate portion, 42a Opening, 43 Female screw, 60 Upper current collector plate, 61 Metal plate, 61a Through hole, 64 Laminated portion, 65 Recessed portion, 70 Terminal cap, 76 negative electrode current collector, 81 pressing plate portion, 82 cylindrical portion.

Claims

1. A cylindrical secondary battery comprising: an electrode group in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; a current collector connected to the electrode group; a sealing body arranged on top of the electrode group, to which the current collector is connected and which functions as an electrode terminal; and a bottomed cylindrical battery can containing the electrode group, wherein the sealing body is fixed to the inside axial direction of an open end of the battery can and closes the opening of the battery can, and a cap is attached to the open end of the battery can, the cap having a tubular portion with a female thread on its inner circumferential surface and a pressing plate portion continuing from one end of the tubular portion and pressed against the outside axial direction of the open end of the battery can, the battery can having a male thread on its outer circumferential surface, and the battery can and the cap are screwed together by the female thread and the male thread.

2. The cylindrical secondary battery according to claim 1, wherein the female thread is provided in a height range that is 50% or more of the axial height of the inner circumferential surface of the cylindrical portion.

3. A cylindrical secondary battery as described in claim 1 or 2, wherein a radially bent portion bent radially inward is formed at the open end of the battery can, and the sealing body is crimped and fixed to the open end via a gasket.