Cylindrical battery

Abstract

A battery (10) comprises: an electrode body in which a positive electrode and a negative electrode are wound with a separator therebetween; a bottomed cylindrical outer can that accommodates the electrode body; a sealing body that is fixed to an opening of the outer can by caulking through a gasket; a plurality of electrode leads (20) that are joined to the positive electrode at intervals in a longitudinal direction of the positive electrode; and an upper current collector plate (50) included in the sealing body and to which the leading end side of the positive electrode leads (20) is welded by a plurality of dot-shaped welds (70) positioned at intervals in a circumferential direction. According to the battery (10), the plurality of electrode leads (20) can be welded to the upper current collector plate (50) more reliably, and are less likely to be damaged.

Description

Cylindrical battery

[0001] The present disclosure relates to cylindrical batteries.

[0002] A conventional cylindrical battery is described in Patent Document 1. This cylindrical battery includes an electrode assembly, a cylindrical outer can with a bottom that houses the electrode assembly, a sealing body that closes the opening of the outer can, and a gasket that is sandwiched between the outer can and the sealing body. The electrode assembly has a structure in which a positive electrode and a negative electrode are wound with a separator interposed therebetween. The positive electrode and the sealing body are electrically connected via a positive electrode lead, and the negative electrode and the bottom of the outer can are electrically connected via a negative electrode lead.

[0003] Japanese Patent Application Publication No. 09-274923

[0004] 9 is an axial cross-sectional view of a cylindrical battery of the reference example. The cylindrical battery 210 of the reference example is not publicly known and cannot be considered prior art for the cylindrical battery of the present disclosure, and therefore cannot be considered technology that negates the patentability of the cylindrical battery of the present disclosure. As shown in FIG. 9, the cylindrical battery 210 of the reference example has multiple positive electrode leads 20 joined to the positive electrode of the electrode assembly 14 at intervals in the longitudinal direction of the positive electrode.

[0005] The tip of each positive electrode lead 20 is bent so as to fit along the upper side of an upper current collector plate 50 having a circular ring shape in a plan view, and is sandwiched between the upper current collector plate 50 and a circular metal ring 290. With the tip of each positive electrode lead 20 sandwiched between the upper current collector plate 50 and the circular metal ring 290, a laser beam is scanned circularly from above in the circumferential direction and irradiated onto the metal ring 290, thereby welding the upper current collector plate 50, the positive electrode lead 20, and the metal ring 290 to one another. The positive electrode is electrically connected to a terminal cap 27 joined to the upper current collector plate 50.

[0006] In the cylindrical battery 210 of the reference example, each of the multiple positive electrode leads 20 joined to the positive electrode at intervals along the positive electrode longitudinal direction is electrically connected to the terminal cap 27, thereby shortening the current collection path and reducing electrical resistance. However, the present inventors discovered that laser welding, in which a laser beam is continuously scanned in a circular pattern from above in the circumferential direction, can damage the positive electrode lead 20. Therefore, an object of the present disclosure is to provide a cylindrical battery in which multiple electrode leads can be easily and reliably welded to the current collector plate and the electrode leads are less likely to be damaged.

[0007] In order to solve the above problems, the cylindrical battery according to the present disclosure comprises an electrode body in which a first electrode and a second electrode are wound with a separator interposed therebetween, a bottomed cylindrical outer can that houses the electrode body, a sealing body that is crimped and fixed to the opening of the outer can via a gasket, a plurality of electrode leads that are joined to the first electrode at intervals in the longitudinal direction of the first electrode, and a current collector plate that is included in the sealing body and has the tip sides of the electrode leads welded by a plurality of dot-shaped welds that are positioned at intervals in the circumferential direction.

[0008] Another aspect of a cylindrical battery according to the present disclosure includes an electrode assembly in which a first electrode and a second electrode are wound with a separator interposed therebetween, a bottomed cylindrical outer can that houses the electrode assembly, a sealing body that is crimped and fixed to the opening of the outer can via a gasket, a plurality of electrode leads that are joined to the first electrode at intervals in the longitudinal direction of the first electrode, and a current collector plate that is included in the sealing body and to which the tip sides of the electrode leads are welded by welds that extend circumferentially, and in a plan view seen from the axial direction, both the radially inner edge and the radially outer edge of the weld have a wave shape with alternating concave and convex shapes.

[0009] According to the cylindrical battery according to the present disclosure, the electrode leads can be reliably welded to the current collector plate, and the electrode leads are less likely to be damaged.

[0010] 1 is an axial cross-sectional view of a cylindrical battery according to an embodiment of the present disclosure; FIG. 2 is a perspective view showing a portion of an electrode body and a positive electrode lead; FIG. 3 is a plan view of an upper current collector plate to which a positive electrode lead has been welded, as viewed from above in the axial direction; FIG. 4 is an axial cross-sectional view showing a portion of a cross section including concentric circles on which a plurality of dot-shaped welds have been formed and the axial direction, developed into a band shape; FIG. 5 is a plan view corresponding to FIG. 3 of a cylindrical battery of a reference example; FIG. 6 is a schematic diagram for explaining problems with laser welding of two positive electrode leads constituting each set in the battery of the reference example; FIG. 7 is a schematic plan view corresponding to FIG. 3 of a battery of a modified example; and FIG. 8 is a schematic plan view corresponding to FIG. 7 of the battery of the reference example.

[0011] 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.

[0012] When multiple embodiments and variations are included below, it is assumed from the beginning that new embodiments can be constructed by appropriately combining their characteristic features. Furthermore, in the following embodiments, the same components are designated by the same reference numerals in the drawings, and redundant explanations are omitted. Furthermore, multiple drawings include schematic diagrams, and the dimensional ratios of the length, width, height, etc. of each component between different drawings do not necessarily match. Furthermore, in this specification, the side of the sealing body 17 in the axial direction (height direction) of the cylindrical battery 10 is referred to as "upper," and the side of the bottom 68 of the outer can 16 in the axial direction is referred to as "lower."

[0013] In the following description, the first electrode is a positive electrode, the second electrode is a negative electrode, the longitudinal direction of the first electrode is the longitudinal direction of the positive electrode, and the electrode lead is a positive electrode lead. However, the first electrode may be a negative electrode, the second electrode may be a positive electrode, the longitudinal direction of the first electrode is the longitudinal direction of the negative electrode, and the electrode lead may be a negative electrode lead. In addition, among the components described below, components not recited in the independent claim representing the highest concept are optional components and are not essential components.

[0014] Fig. 1 is an axial cross-sectional view of a cylindrical battery 10 according to one embodiment of the present disclosure. As shown in Fig. 1, the cylindrical battery (hereinafter simply referred to as battery) 10 includes a wound electrode assembly 14, a non-aqueous electrolyte (not shown), a cylindrical metal outer can 16 with a bottom that houses the electrode assembly 14 and the non-aqueous electrolyte, and a sealing body 17 that is crimped to the opening of the outer can 16 via a gasket 28.

[0015] The non-aqueous electrolyte has ion conductivity (e.g., lithium ion conductivity). The non-aqueous electrolyte may be a liquid electrolyte (electrolytic solution) or a solid electrolyte. The liquid electrolyte (electrolytic solution) includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent include esters, ethers, nitriles, amides, and mixed solvents of two or more of these. Examples of the non-aqueous solvent include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixed solvents of these. The non-aqueous solvent may contain a halogen-substituted compound (e.g., fluoroethylene carbonate) in which at least a portion of the hydrogen atoms of these solvents are substituted with halogen atoms such as fluorine. The electrolyte salt may include, for example, LiPF ６ Lithium salts such as

[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] FIG. 2 is a perspective view showing a portion of the electrode assembly 14 and the positive electrode lead 20. As shown in FIG. 2, the electrode assembly 14 has a long positive electrode 11, a long negative electrode 12, and two long separators 13, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound with the separator 13 interposed therebetween. A plurality of positive electrode leads 20 are joined to the positive electrode 11 at intervals in the longitudinal direction of the positive electrode 11 for electrical connection. As shown in FIG. 2, in this embodiment, eight positive electrode leads 20 are joined at approximately equal intervals in the longitudinal direction, and there are four pairs of two positive electrode leads 20 having radial overlapping portions that overlap in the radial direction. The four pairs of positive electrode leads 20 are arranged at intervals from each other in the circumferential direction.

[0018] The negative electrode 12 is formed to have dimensions slightly larger than the positive electrode 11 in order to prevent lithium precipitation. That is, the negative electrode 12 is formed to be longer in the longitudinal direction and width direction (short direction) than the positive electrode 11. Furthermore, the two separators 13 are formed to have dimensions slightly larger than the positive electrode 11 and are arranged to sandwich the positive electrode 11. The separator 13 protrudes upward beyond the positive electrode 11 and the negative electrode 12, and the negative electrode 12 protrudes downward beyond the positive electrode 11 and the separator 13.

[0019] The negative electrode 12 has a negative electrode core exposed portion 41, where the negative electrode mixture layer 42 is not provided on the negative electrode core 40, at the axial lower end from the winding start end to the winding end end in the longitudinal direction of the long negative electrode 12. Therefore, the axial lower end of the electrode assembly 14 is formed by the negative electrode core exposed portion 41. The negative electrode 12 may form the winding start end of the electrode assembly 14. However, typically, the separator 13 extends beyond the winding start end of the negative electrode 12, and the winding start end of the separator 13 becomes the winding start end of the electrode assembly 14.

[0020] The positive electrode 11 has a positive electrode core and positive electrode mixture layers formed on both sides of the positive electrode core. The positive electrode core can be made of a metal foil, such as aluminum or an aluminum alloy, that is stable within the potential range of the positive electrode 11, or a film with such a metal disposed on the surface layer. The positive electrode mixture layer contains a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 can be produced, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, etc., onto the positive electrode core, drying the coating, and then compressing it to form positive electrode mixture layers on both sides of the positive electrode core.

[0021] The positive electrode active material is mainly composed of a lithium-containing metal composite oxide. Examples of metal elements contained in the lithium-containing metal composite oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, and W. An example of a preferred lithium-containing metal composite oxide is a composite oxide containing at least one of Ni, Co, Mn, and Al.

[0022] Examples of conductive agents contained in the positive electrode mixture layer include carbon materials such as carbon black, acetylene black, ketjen black, and graphite. Examples of binders contained in the positive electrode mixture layer include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. These resins may be used in combination with cellulose derivatives such as carboxymethyl cellulose (CMC) or its salts, polyethylene oxide (PEO), and the like.

[0023] The positive electrode 11 is arranged at approximately equal intervals in the longitudinal direction and has the same number of positive electrode core exposed portions as the positive electrode leads 20 in the intermediate portion in the longitudinal direction, excluding both end portions. The positive electrode lead 20 is joined to the positive electrode core exposed portions. By joining the multiple positive electrode leads 20 at intervals in the longitudinal direction of the strip-shaped positive electrode core, preferably at approximately equal intervals in the longitudinal direction, the current path in the longitudinal direction of the positive electrode 11 can be shortened, and the internal resistance of the battery 10 can be reduced. The positive electrode lead 20 is covered, for example, with insulating tape (not shown), thereby suppressing short circuits between the positive electrode 11 and the negative electrode 12. It is preferable that the insulating tape cover all of the positive electrode core exposed portions.

[0024] The negative electrode 12 has a negative electrode core 40 and a negative electrode mixture layer 42 formed on both sides of the negative electrode core 40. For the negative electrode core 40, a metal foil 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, can be used. The negative electrode mixture layer 42 contains a negative electrode active material and a binder. The negative electrode 12 can be produced, for example, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder, etc., onto the negative electrode core 40, drying the coating, and then compressing it to form the negative electrode mixture layer 42 on both sides of the negative electrode core 40.

[0025] The negative electrode active material generally uses a carbon material that reversibly absorbs and releases lithium ions. Preferred carbon materials include natural graphite such as flake graphite, lump graphite, and amorphous graphite, and artificial graphite such as lump artificial graphite and graphitized mesophase carbon microbeads. The negative electrode mixture layer 42 may contain a silicon (Si) material as the negative electrode active material. Furthermore, the negative electrode active material may include a metal other than Si that alloys with lithium, an alloy containing such a metal, or a compound containing such a metal.

[0026] As in the case of the positive electrode 11, fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, or the like may be used as the binder contained in the negative electrode mixture layer 42, but styrene-butadiene rubber (SBR) or a modified product thereof is preferably used. In addition to SBR or the like, the negative electrode mixture layer may also contain, for example, CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, or the like.

[0027] A porous sheet having ion permeability and insulating properties is used for the separator 13. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. Preferred materials for the separator 13 include polyolefin resins such as polyethylene and polypropylene, and cellulose. The separator 13 may have either a single-layer structure or a laminated structure. A heat-resistant layer or the like may be formed on the surface of the separator 13.

[0028] As shown in FIG. 1 , the battery 10 includes an annular insulating plate 18 on the upper side of the electrode body 14. A positive electrode lead 20 attached to the positive electrode 11 passes through a through-hole in the insulating plate 18 and extends toward the sealing body 17. The sealing body 17 includes an upper current collector plate 50 and a terminal cap 27. The upper current collector plate 50 is a metal annular plate member with a through-hole 50a in its radial center. The terminal cap 27 is a metal plate member without a through-hole and is located axially above the sealing body 17. The axially upper end face of the terminal cap 27 is exposed to the outside except for the outer edge, and this exposed portion forms the positive electrode terminal.

[0029] Each positive electrode lead 20 passes from the positive electrode 11 through a through-hole 50a in the upper current collector plate 50 and is bent along the upper surface of the upper current collector plate 50. The overlapping portion 20a located at the tip side of the positive electrode lead 20 overlaps the upper current collector plate 50 in the axial direction. The overlapping portion 20a and the upper current collector plate 50 are joined by laser welding. The welding method and welding structure of the overlapping portion 20a and the upper current collector plate 50 will be described in detail later.

[0030] The sealing body 17 has a laminated portion 60 on its radially outer periphery, in which a terminal cap 27 and an upper current collector plate 50 are laminated. By irradiating the laminated portion 60 with a laser beam from above in the axial direction, the terminal cap 27 and the upper current collector plate 50 are laser-welded and electrically connected. The annular upper surface of the upper current collector plate 50 has an annular recess that is open axially upward and radially inward, radially inward from the laminated portion 60, and an annular space 65 that is open only radially inward is provided between the upper current collector plate 50 and the terminal cap 27 in the axial direction. Each positive electrode lead 20 is joined to the upper current collector plate 50 within the annular space 65.

[0031] The battery 10 includes a metal lower current collector plate 52 axially below the electrode assembly 14. Referring to FIGS. 1 and 2 , the electrode assembly 14 is pressed against the upper surface of the lower current collector plate 52 so as to tilt the strip-shaped negative electrode substrate exposed portion 41 radially inward. Laser light is irradiated from the lower surface of the lower current collector plate 52, thereby laser-welding and joining the negative electrode substrate exposed portion 41 to the upper surface of the lower current collector plate 52 over a wide area. Laser light is also irradiated from the lower side of the outer can 16, thereby laser-welding the bottom 68 of the outer can 16 to the lower current collector plate 52. This electrically connects the negative electrode 12 of the electrode assembly 14 to the outer can 16 via the lower current collector plate 52. Joining the negative electrode substrate exposed portion 41 to the upper surface of the lower current collector plate 52 over a wide area prevents current from flowing long distances along the longitudinal direction of the elongated negative electrode 12, thereby reducing the electrical resistance of the battery 10.

[0032] The outer can 16 has a cylindrical portion 39 and a bottom 68. 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 portion of the cylindrical portion 39 to recess it radially inward around the entire circumferential direction. The sealing body 17 is placed on the grooved portion 22 and is fixed to the opening of the outer can 16 by crimping via a resin gasket 28. The shoulder portion 29 is formed when the upper end of the cylindrical portion 39 is bent radially inward and crimped to the flange portion of the sealing body 17, and extends radially inward at the upper end of the cylindrical portion 39.

[0033] The gap between the outer can 16 and the sealing body 17 is sealed with an annular gasket 28, thereby sealing the internal space of the battery 10. The gasket 28 is sandwiched between the outer can 16 and the sealing body 17 and insulates the sealing body 17 from the outer can 16. The gasket 28 serves as a sealant to maintain airtightness inside the battery and as an insulating material to insulate the outer can 16 from the sealing body 17. The gasket 28 may have a through-hole 28a. When the nonaqueous electrolyte is a liquid electrolyte (electrolytic solution), providing the through-hole 28a in the gasket 28 facilitates the flow of the electrolyte within the battery 10, thereby improving the circulation of the liquid within the battery 10. The terminal cap 27 electrically connected to the positive electrode lead 20 serves as a positive electrode terminal, and the outer can 16 electrically connected to the negative electrode core exposed portion 41 via the lower current collector plate 52 serves as a negative electrode terminal.

[0034] The battery 10 has a thin, easily breakable portion 68a on the bottom 68 of the exterior can 16. The easily breakable portion 68a is formed, for example, by stamping a circle or a C-shape on the underside of the bottom 68. If the bottom 68 has the easily breakable portion 68a, when the battery 10 abnormally heats up, the easily breakable portion 68a breaks, allowing high-temperature gas inside the battery 10 to be discharged to the outside, thereby improving the safety of the battery 10. The thin, easily breakable portion may also be provided on the terminal cap 27.

[0035] FIG. 3 is a plan view of the upper current collector plate 50 to which the positive electrode lead 20 is welded, as viewed from above in the axial direction. As shown in FIG. 3 , the tip side of the positive electrode lead 20 is welded to the upper current collector plate 50 by a plurality of dot-shaped welds 70 spaced apart in the circumferential direction. Specifically, the two positive electrode leads 20 constituting each set have lead overlapping portions 20b that overlap with each other in the axial direction. For example, by using a pulsed laser, laser light is irradiated from above in a perforated pattern at intervals in the circumferential direction on a concentric circle that includes portions of the two axially overlapping lead overlapping portions 20b along the upper surface of the upper current collector plate 50. As a result, the two axially overlapping lead overlapping portions 20b are welded by the plurality of dot-shaped welds 70 spaced apart in the circumferential direction, and the two welded lead overlapping portions 20b and the upper current collector plate 50 are also welded by the plurality of dot-shaped welds 70.

[0036] 4 is an axial cross-sectional view showing a portion of a cross section including the axial direction and concentric circles on which a plurality of dot-shaped welds 70 are formed, expanded into a band shape. The left-right direction in FIG. 4 corresponds to the circumferential direction of the upper current collector plate 50, and the up-down direction in FIG. 4 corresponds to the thickness direction of the upper current collector plate 50. Of the two positive electrode leads 20 constituting each set, the upper positive electrode lead 20 may have a portion that does not overlap with the lower positive electrode lead 20 in the axial direction due to a circumferential phase difference between the joining positions of the two positive electrode leads 20 to the positive electrode 11.

[0037] The dot-shaped weld 70a located on the left side of Fig. 4 is a weld 70 that welds a portion of the upper positive electrode lead 20c located on the upper side that does not overlap the lower positive electrode lead 20d located on the lower side in the axial direction to the upper current collector plate 50. In addition, the dot-shaped weld 70b located in the center of Fig. 4 and the dot-shaped weld 70c located on the right side are welds 70 that are provided at positions where the upper positive electrode lead 20c and the lower positive electrode lead 20d overlap in the axial direction. As shown in Fig. 4, a gap 85 is formed between the portion of the upper positive electrode lead 20c that does not overlap the lower positive electrode lead 20d in the axial direction and the upper current collector plate 50.

[0038] Next, the effects of the cylindrical battery 10 according to the present disclosure will be described. FIG. 5 is a plan view of a battery 210 according to a reference example, corresponding to FIG. 3 . As shown in FIG. 5 , in the battery 210 according to the reference example, the tip end of each positive electrode lead 20 (see FIG. 9 ) is bent to fit along the upper side of an upper current collector 50, which has a circular ring shape in plan view, and is sandwiched between the upper current collector 50 and a circular metal ring 290. Furthermore, with the tip end of each positive electrode lead 20 sandwiched between the upper current collector 50 and the circular metal ring 290, laser light is continuously scanned in a circular pattern from above in the circumferential direction, irradiating the metal ring 290, thereby welding the upper current collector 50, the positive electrode lead 20, and the metal ring 290 to one another. In the battery 210 according to the reference example, a circular weld 270 having a substantially uniform width is formed around the entire circumference in a plan view when viewed from above in the axial direction.

[0039] FIG. 6 is a schematic diagram illustrating problems with laser welding of two positive electrode leads 20 constituting each pair in a battery 210 of the reference example. As shown in FIG. 6 , in the battery 210 of the reference example, laser light is continuously irradiated over the entire circumferential direction. Therefore, the laser light is irradiated over the entire circumferential direction, even to a portion of the upper positive electrode lead 20c that does not axially overlap with the lower positive electrode lead 20d, i.e., the low-rigidity portion 33 where a gap 85 is formed below the upper positive electrode lead 20c and where the rigidity is low. Therefore, there is a risk that holes will be formed in the low-rigidity portion 33, or that cracks generated in the low-rigidity portion 33 will become continuous and cause breaks in the low-rigidity portion 33, making it difficult to stabilize quality.

[0040] In contrast, in the battery 10, the tip side of the positive electrode lead 20 is welded to the upper current collector plate 50 by a plurality of dot-shaped welds 70 spaced apart in the circumferential direction. Therefore, unlike the case shown in Fig. 5, the welds 70 are not formed over the entire circumferential area of ​​the low-rigidity portion 33, and excessive force is not applied to the low-rigidity portion 33. Furthermore, even if a crack occurs in the low-rigidity portion 33 due to irradiation with laser light, the crack does not become continuous, and the position where the crack occurs is limited to a local position in the low-rigidity portion 33.

[0041] As a result, even if the output of the laser light is increased to an output that can reliably weld the positive electrode lead 20 to the upper current collecting plate 50, it is possible to suppress damage to the positive electrode lead 20. Therefore, the multiple positive electrode leads 20 can be easily and reliably welded to the upper current collecting plate 50, and the positive electrode leads 20 are less likely to be damaged.

[0042] Furthermore, in comparison with the reference example battery 210, the battery 10 eliminates the metal ring 290 and has fewer parts, thereby reducing manufacturing costs and simplifying the manufacturing process, thereby improving the mass productivity of the battery 10.

[0043] To ensure sufficient weld strength between the positive electrode lead 20 and the upper current collector plate 50, the distance between adjacent welds 70 in the circumferential direction is preferably 3 mm or less. To ensure sufficient weld strength between the positive electrode lead 20 and the upper current collector plate 50, the width of the welds 70 is preferably 0.01 mm or more. To ensure sufficient weld strength between the positive electrode lead 20 and the upper current collector plate 50, the ratio of the axial thickness of the welds 70 to the axial thickness of the upper current collector plate 50 in an axial cross section including the welds 70 is preferably 0.05 or more.

[0044] The width of welded portion 70 is preferably 5 mm or less, since this makes it difficult for damage to occur in the portion irradiated with the laser light. In order to prevent the laser light from penetrating into upper current collecting plate 50, the ratio of the axial thickness of welded portion 70 to the axial thickness of upper current collecting plate 50 in an axial cross section including welded portion 70 is preferably 0.95 or less.

[0045] The present disclosure is not limited to the above-described embodiment and its variations, and various improvements and modifications are possible within the scope of the claims of the present application and their equivalents. For example, in the above-described embodiment, as shown in FIG. 7( a), the tip side of the positive electrode lead 20 is joined to the upper current collector plate 50 by a plurality of dot-shaped welds 70 spaced apart in the circumferential direction. However, as shown in FIGS. 7( b) and 8, the tip side of the positive electrode lead 20 may be welded to the upper surface of the upper current collector plate 50 by a circumferentially extending weld 170 using a pulsed laser. In a plan view seen from the axial direction, both a radially inner edge 171 and an outer edge 172 of the weld 170 may have a wave shape with alternating concave and convex portions.

[0046] Even in the case of the modified example, compared to when laser light is continuously irradiated concentrically, i.e., when the positive electrode lead 20 and the upper current collecting plate 50 are laser welded at a circular welding portion 270 having approximately the same width around the entire circumference (see Figure 7 (c)), excessive force is less likely to be applied to the low rigidity portion 33, the multiple positive electrode leads 20 are more likely to be reliably welded to the upper current collecting plate 50, and damage to the positive electrode lead 20 is less likely to occur.

[0047] In addition, the battery 10 has eight positive electrode leads 20, and four pairs of two positive electrode leads 20 each having a lead overlap portion 20b that overlaps with each other in the axial direction have been described. However, the battery may have multiple positive electrode leads, and one, two, three, five or more pairs of two positive electrode leads each having a lead overlap portion that overlaps with each other in the axial direction. Alternatively, the battery may have multiple positive electrode leads, and there may be no pairs of two positive electrode leads each having a lead overlap portion that overlaps with each other in the axial direction. Even in this case, continuous cracks can be prevented from occurring in the positive electrode leads.

[0048] Also, the case where the negative electrode substrate exposed portion 41 is electrically connected to the bottom 68 of the outer can 16 via the lower current collector plate 52 has been described. However, the negative electrode substrate exposed portion may also be electrically connected to the bottom of the outer can via one or more negative electrode leads. Alternatively, the outermost peripheral surface of the electrode assembly may include the negative electrode substrate exposed portion, and the negative electrode substrate exposed portion on this outermost peripheral surface may be brought into contact with the inner peripheral surface of the outer can, thereby electrically connecting the negative electrode to the outer can. Alternatively, in addition to the contact of the negative electrode substrate exposed portion on this outermost peripheral surface with the inner peripheral surface of the outer can, a negative electrode substrate exposed portion provided at the end of the negative electrode on the winding start side may also be electrically connected to the bottom of the outer can via a negative electrode lead.

[0049] In addition, the case where the tip side of the positive electrode lead 20 is welded only to the upper current collector plate 50, and only the tip side of the positive electrode lead 20 welded to the upper current collector plate 50 is disposed in the annular space provided axially between the upper current collector plate 50 and the terminal cap 27 has been described. However, the battery may include an annular metal ring, and the tip side of the positive electrode lead may be sandwiched between the upper current collector plate and the metal ring. The tip side of the positive electrode lead welded to the upper current collector plate may be laser-welded to the metal ring by irradiating the metal ring with laser light from above using the method disclosed herein. Furthermore, the tip side of the positive electrode lead 20 welded to the upper current collector plate 50 and at least a portion of the metal ring may be disposed in the annular space provided axially between the upper current collector plate and the terminal cap.

[0050] The cylindrical battery of the present disclosure may also have the following configurations: Configuration 1: A cylindrical battery comprising: an electrode assembly in which a first electrode and a second electrode are wound with a separator interposed therebetween, a bottomed cylindrical outer can that houses the electrode assembly, a sealing body that is fixed to the opening of the outer can by crimping via a gasket, a plurality of electrode leads that are joined to the first electrode at intervals in the longitudinal direction of the first electrode, and a current collector plate that is included in the sealing body and to which tip sides of the electrode leads are welded by a plurality of dot-shaped welds that are positioned at intervals in the circumferential direction. a cylindrical battery comprising: an electrode assembly in which a first electrode and a second electrode are wound with a separator interposed therebetween, a bottomed tubular outer can containing the electrode assembly, a sealing body crimped to an opening of the outer can via a gasket, a plurality of electrode leads joined to the first electrode at intervals in the longitudinal direction of the first electrode, and a current collector plate included in the sealing body and to which the tip ends of the electrode leads are welded by welds extending in the circumferential direction, wherein, in a plan view seen from the axial direction, both the radially inner edge and the radially outer edge of the weld have a wave shape with alternating concave and convex shapes. Configuration 4: A cylindrical battery according to any one of configurations 1 to 3, wherein the radially outer side of the current collector plate is joined to a terminal cap constituting an external terminal, an annular space that is open only radially inward is provided between the current collector plate and the terminal cap in the axial direction, and only the tip side of the electrode lead welded to the current collector plate is disposed within the annular space.Configuration 5: A cylindrical battery according to configuration 1, wherein the distance between adjacent welds in the circumferential direction is 3 mm or less.Configuration 6: A cylindrical battery according to any one of configurations 1 to 5, wherein the width of the weld is 0.01 mm or more and 3 mm or less.Configuration 7: A cylindrical battery according to any one of configurations 1 to 6, wherein the ratio of the axial thickness of the weld to the axial thickness of the current collector plate in an axial cross section including the weld is 0.05 or more and 0.95 or less.Configuration 8: A cylindrical battery according to any one of configurations 1 to 7, wherein there are four pairs of two electrode leads, each pair having a lead overlap portion that overlaps with each other in the axial direction, the four pairs of electrode leads are positioned at intervals in the circumferential direction, the two lead overlap portions that overlap in the axial direction are welded, and the two welded lead overlap portions and the current collector plate are also welded.

[0051] REFERENCE SIGNS LIST 10 Battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 16 Outer can, 17 Sealing body, 18 Insulating plate, 20 Positive electrode lead, 20a Overlapping portion, 20b Lead overlapping portion, 20c Upper positive electrode lead, 20d Lower positive electrode lead, 22 Grooved portion, 27 Terminal cap, 28 Gasket, 28a Through hole, 29 Shoulder portion, 33 Low rigidity portion, 39 Cylindrical portion, 40 Negative electrode core, 41 Negative electrode core exposed portion, 42 Negative electrode mixture layer, 50 Upper current collector plate, 50a Through hole, 52 Lower current collector plate, 60 Stacked portion, 65 Annular space, 68 Bottom portion, 68a Easy-to-break portion, 70, 70a, 70b, 70c, 170 welded portion, 85 gap, 171 radially inner edge of welded portion, 172 radially outer edge of welded portion.

Claims

1. A cylindrical battery comprising: an electrode body in which a first electrode and a second electrode are wound with a separator interposed therebetween; a bottomed, cylindrical outer can containing the electrode body; a seal body that is crimped and fixed to the opening of the outer can via a gasket; a plurality of electrode leads joined to the first electrode at intervals in the longitudinal direction of the first electrode; and a current collector plate that is included in the seal body and has the tips of the electrode leads welded to it by a plurality of dot-shaped welds positioned at intervals in the circumferential direction.

2. A cylindrical battery comprising: an electrode body in which a first electrode and a second electrode are wound with a separator interposed therebetween; a bottomed, cylindrical outer can containing the electrode body; a sealing body which is crimped and fixed to the opening of the outer can via a gasket; a plurality of electrode leads which are joined to the first electrode at intervals in the longitudinal direction of the first electrode; and a current collector plate which is included in the sealing body and to which the tips of the electrode leads are welded by welds which extend in the circumferential direction, wherein, in a plan view seen from the axial direction, both the radially inner edge and the radially outer edge of the welds have a wavy shape with alternating concaves and convexes.

3. The cylindrical battery according to claim 1 or 2, wherein the tip side of the electrode lead is welded only to the current collector plate.

4. A cylindrical battery as described in claim 1 or 2, wherein the radially outer side of the current collecting plate is joined to a terminal cap constituting an external terminal, an annular space which is open only to the radially inner side is provided between the current collecting plate and the terminal cap in the axial direction, and only the tip side of the electrode lead welded to the current collecting plate is positioned within the annular space.

5. The cylindrical battery according to claim 1, wherein the distance between adjacent welded portions in the circumferential direction is 3 mm or less.

6. The cylindrical battery according to claim 1 or 2, wherein the width of the welded portion is 0.01 mm or more and 3 mm or less.

7. A cylindrical battery as described in claim 1 or 2, wherein the ratio of the axial thickness of the welded portion to the axial thickness of the current collector plate in an axial cross section including the welded portion is 0.05 or more and 0.95 or less.

8. A cylindrical battery as described in claim 1 or 2, wherein there are four sets of two electrode leads, each set having a lead overlap portion that overlaps with each other in the axial direction, the four sets of electrode leads are positioned at intervals in the circumferential direction, the two lead overlap portions that overlap in the axial direction are welded, and the two welded lead overlap portions and the current collecting plate are also welded.

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