Cylindrical battery and its manufacturing method

Abstract

A cylindrical battery (10) comprises: an outer can (16) having a bottomed cylinder shape; an electrode body (14) that is accommodated inside the outer can (16), and in which an elongated positive electrode (11) and an elongated negative electrode (12) having different polarities from each other are wound with a separator (13) interposed therebetween; a metal plate (19) that is disposed between the electrode body (14) and a bottom part (68) of the outer can (16); and a plurality of negative electrode lead parts (21) that extend from the negative electrode (12) towards the bottom part (68). A tip part (21a) of each negative electrode lead part (21) is sandwiched between the metal plate (19) and the bottom part (68), and is electrically connected to the bottom part (68).

Description

[Technical Field]

[0001] The present disclosure relates to cylindrical batteries and methods for manufacturing the same. [Background technology]

[0002] A conventional cylindrical battery is described in Patent Document 1. This cylindrical battery includes a negative electrode current collector disposed between an electrode assembly and an outer can. In this cylindrical battery, multiple negative electrode leads protruding from the negative electrode of the electrode assembly are welded to the surface of the negative electrode current collector facing the electrode assembly. In addition, a protrusion protruding from a portion of the negative electrode current collector toward the bottom of the outer can is provided, and the protrusion is positioned in a recess provided on the inner surface of the bottom, thereby electrically connecting the negative electrode current collector to the outer can. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-126708 Summary of the Invention [Problem to be solved by the invention]

[0004] In the cylindrical battery, the negative electrode lead is electrically connected to the outer can via the negative electrode current collector, and the presence of the negative electrode current collector increases electrical resistance. Therefore, an object of the present disclosure is to provide a cylindrical battery that can reduce internal resistance. [Means for solving the problem]

[0005] In order to solve the above problems, the cylindrical battery of the present disclosure comprises a bottomed cylindrical outer can, an electrode body housed within the outer can and formed by winding a first elongated electrode and a second elongated electrode having opposite polarities with a separator interposed therebetween, a metal plate disposed between the bottom of the outer can and the electrode body, and a plurality of second electrode lead portions extending from the second electrode toward the bottom, with the tip of each second electrode lead portion being sandwiched between the metal plate and the bottom and electrically connected to the bottom of the outer can. [Effects of the Invention]

[0006] According to the cylindrical battery of the present disclosure, the multiple second electrode lead portions can be electrically connected to the outer can without using a metal plate, thereby reducing internal resistance. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is an axial cross-sectional view of a cylindrical battery according to an embodiment of the present disclosure. [Figure 2] FIG. [Figure 3] FIG. 2 is a schematic plan view of the negative electrode as viewed in the thickness direction. [Figure 4] FIG. 2 is a schematic diagram showing the position of the negative electrode lead portion and the laser light irradiation area when the cylindrical battery of the example is viewed from the bottom of the outer can. [Figure 5A] FIG. 2 is a schematic diagram showing the bottom side of the cylindrical battery of FIG. [Figure 5B] FIG. 5B is a schematic diagram corresponding to FIG. 5A of a cylindrical battery according to a second embodiment. [Figure 5C] FIG. 5B is a schematic diagram corresponding to FIG. 5A of a cylindrical battery according to a third embodiment. [Figure 5D] FIG. 5B is a schematic diagram corresponding to FIG. 5A of a cylindrical battery according to a fourth embodiment. [Figure 6A] FIG. 5 is a schematic diagram corresponding to FIG. 4, illustrating a laser light irradiation region in a modified example. [Figure 6B] FIG. 5 is a schematic diagram corresponding to FIG. 4, illustrating a laser light irradiation region in another modified example. [Figure 6C] FIG. 5 is a schematic diagram corresponding to FIG. 4, illustrating a laser light irradiation region in another modified example. [Figure 7] FIG. 4 is a schematic plan view of a negative electrode according to a modified example, corresponding to FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of a cylindrical battery according to the present disclosure will be described in detail with reference to the drawings. The cylindrical battery according to the present disclosure may be a primary battery or a secondary battery. It may also be a battery using an aqueous electrolyte or a battery using a non-aqueous electrolyte. In the following, a non-aqueous electrolyte secondary battery (lithium ion battery) using a non-aqueous electrolyte will be exemplified as a cylindrical battery 10 according to one embodiment, but the cylindrical battery according to the present disclosure is not limited thereto.

[0009] When multiple embodiments and variations are included below, it is anticipated from the beginning that new embodiments can be constructed by appropriately combining their characteristic features. In the following embodiments, the same components are denoted 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. In this specification, the side of the sealing body 17 in the axial direction (height direction) of the battery case 15 is referred to as "top," and the bottom side of the outer can 16 in the axial direction is referred to as "bottom." Among the components described below, components not recited in the independent claims representing the highest concepts are optional components and not essential components.

[0010] FIG. 1 is an axial cross-sectional view of a cylindrical battery 10 according to an embodiment of the present disclosure, and FIG. 2 is a perspective view of an electrode assembly 14 of the cylindrical battery 10. As shown in FIG. 1, the cylindrical battery 10 includes a wound electrode assembly 14, a non-aqueous electrolyte (not shown), and a battery case 15 that accommodates the electrode assembly 14 and the non-aqueous electrolyte. The electrode assembly 14 includes a positive electrode 11 as an example of a first electrode, a negative electrode 12 as an example of a second electrode, and a separator 13 interposed between the positive electrode 11 and the negative electrode 12. The electrode assembly 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 battery case 15 includes a cylindrical outer can 16 with a bottom and a sealing member 17 that closes the opening of the outer can 16. The cylindrical battery 10 also includes a resin gasket 28 disposed between the outer can 16 and the sealing member 17.

[0011] The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent include esters, ethers, nitriles, amides, and mixtures of two or more of these. The non-aqueous solvent may contain a halogen-substituted compound in which at least a portion of the hydrogen atoms of these solvents are substituted with halogen atoms such as fluorine. The non-aqueous electrolyte is not limited to a liquid electrolyte, but may also be a solid electrolyte using a gel polymer or the like. The electrolyte salt is a lithium salt such as LiPF6.

[0012] 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. A positive electrode lead 20 is joined to the positive electrode 11, and a plurality of negative electrode lead portions 21 (only one of which is shown in FIG. 2) are electrically connected to the negative electrode 12. The negative electrode lead portion 21 constitutes a second electrode lead portion. The structure of the plurality of negative electrode lead portions 21 will be described in detail later with reference to FIG. 3. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to suppress lithium deposition, and is formed to be longer than the positive electrode 11 in the longitudinal direction and width direction (short direction). Furthermore, the two separators 13 are formed to be at least slightly larger than the positive electrode 11 and are arranged, for example, to sandwich the positive electrode 11.

[0013] The positive electrode 11 has a positive electrode current collector and a positive electrode mixture layer formed on both sides of the positive electrode current collector. The positive electrode current collector can be 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 current collector, drying the coating, and then compressing it to form a positive electrode mixture layer on both sides of the current collector.

[0014] 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.

[0015] 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, and polyethylene oxide (PEO).

[0016] The negative electrode 12 has a negative electrode current collector and a negative electrode mixture layer formed on both sides of the negative electrode current collector. The negative electrode current collector can be 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. The negative electrode mixture layer contains a negative electrode active material and a binder. The negative electrode 12 can be produced, for example, by applying a negative electrode mixture slurry containing the negative electrode active material and the binder onto the negative electrode current collector, drying the coating, and then compressing it to form a negative electrode mixture layer on both sides of the current collector.

[0017] The negative electrode active material generally uses a carbon material that reversibly absorbs and releases lithium ions. Preferred carbon materials include natural graphite, such as flake graphite, lump graphite, and amorphous graphite, and artificial graphite, such as lump artificial graphite and graphitized mesophase carbon microbeads. The negative electrode mixture layer may contain a 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.

[0018] The binder contained in the negative electrode mixture layer may be a fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, or the like, as in the case of the positive electrode 11. Preferably, styrene-butadiene rubber (SBR) or a modified product thereof is used. The negative electrode mixture layer may contain, in addition to SBR, for example, CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, or the like.

[0019] The separator 13 is a porous sheet having ion permeability and insulating properties. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. Preferred materials for the separator 13 include 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. The negative electrode 12 may form the winding start end of the electrode assembly 14, but typically the separator 13 extends beyond the winding start end of the negative electrode 12, and the winding start end of the separator 13 becomes the winding start end of the electrode assembly 14.

[0020] As shown in Figure 1, cylindrical battery 10 includes an insulating plate 18 disposed above electrode body 14 and a metal plate 19 disposed below electrode body 14. A positive electrode lead 20 attached to positive electrode 11 passes through a through-hole in insulating plate 18 and extends toward sealing body 17. Positive electrode lead 20 is connected by welding or the like to the underside of terminal plate 23, which is the bottom plate of sealing body 17, and sealing plate 27, which is the top plate of sealing body 17 and is electrically connected to terminal plate 23, serves as the positive electrode terminal.

[0021] On the other hand, the multiple negative electrode lead portions 21 pass radially outside the metal plate 19 and then fold back radially inward. The tip portion 21a of each negative electrode lead portion 21 is located between the metal plate 19 and the bottom portion 68 of the outer can 16. The bottom portion 68, the tip portions 21a of each negative electrode lead portion 21, and the metal plate 19 are joined together, and the outer can 16 serves as a negative electrode terminal.

[0022] The outer can 16 is a metal container having a cylindrical portion with a bottom. The space between the outer can 16 and the sealing body 17 is sealed with an annular gasket 28, thereby hermetically sealing the interior space of the battery case 15. The gasket 28 is also sandwiched between the outer can 16 and the sealing body 17, and insulates the sealing body 17 from the outer can 16. In other words, the gasket 28 serves as a sealant to maintain airtightness inside the battery and as an insulator to insulate the outer can 16 and the sealing body 17.

[0023] The outer can 16 has an annular grooved portion 35 along a portion of the cylindrical outer surface in the height direction. The grooved portion 35 can be formed, for example, by spinning a portion of the cylindrical outer surface radially inward to create a recess in the radial direction. The outer can 16 has a bottomed tubular portion 30 including the grooved portion 35 and an annular shoulder portion 33. The bottomed tubular portion 30 accommodates the electrode assembly 14 and the nonaqueous electrolyte, and the shoulder portion 33 is bent radially inward from the end of the open side of the bottomed tubular portion 30 and extends inward. The shoulder portion 33 is formed when the upper end of the outer can 16 is bent inward and crimped to the peripheral edge portion 31 of the sealing body 17. The sealing body 17 is crimped to the outer can 16 with a gasket 28 interposed between the shoulder portion 33 and the grooved portion 35.

[0024] [Cylindrical battery of the embodiment] Next, an example of a method for producing the cylindrical battery 10 will be specifically described. <Preparation of positive electrode> LiNi as the positive electrode active material 0.8 Co 0.15 Al 0.05 O2 was used. A positive electrode mixture paste was prepared by mixing 100 parts by weight of the positive electrode active material, 1.7 parts by weight of polyvinylidene fluoride as a binder, and 2.5 parts by weight of acetylene black as a conductive agent with a liquid component. The positive electrode mixture paste was applied to both sides of an aluminum foil positive electrode current collector, excluding the connection portion of the positive electrode lead, and then dried. The positive electrode was then rolled to a predetermined thickness to obtain a positive electrode. The positive electrode was cut to the predetermined dimensions, and an aluminum positive electrode lead was connected to the exposed portion of the current collector by ultrasonic welding.

[0025] <Preparation of negative electrode> Graphitizable carbon was used as the negative electrode active material. 100 parts by mass of the negative electrode active material, 0.6 parts by mass of polyvinylidene fluoride as a binder, 1 part by mass of carboxymethyl cellulose as a thickener, and an appropriate amount of water were mixed in a twin-arm kneader to form a negative electrode. combination drug The negative electrode mixture paste was applied to both sides of a long negative electrode current collector made of copper foil. When applying the paste to both sides, the negative electrode mixture paste was applied to predetermined regions in the width direction of the long negative electrode current collector on both sides. combination drug A non-coated portion was provided where no paste was applied. Subsequently, both sides of the negative electrode current collector were dried, and then the negative electrode was obtained by rolling to a predetermined thickness. The negative electrode was then cut to a predetermined size so that a non-coated portion was formed on one side in the width direction of the negative electrode. The non-coated portion made of copper foil was then subjected to a press punching process to form a plurality of negative electrode lead portions 21 made up of a portion of the non-coated portion.

[0026] FIG. 3 is a schematic plan view of the fabricated negative electrode 12 as viewed in its thickness direction, and is a schematic plan view for illustrating the structure of the negative electrode lead portion 21. Note that the left edge of the paper in FIG. 3 is the winding start end. As shown in FIG. 3, the negative electrode 12 includes a negative electrode current collector 25 and a negative electrode mixture layer 26 provided on both sides of the negative electrode current collector 25. A non-coated portion 29, from which the negative electrode current collector 25 is exposed, is provided on one side in the width direction of both sides of the negative electrode 12. A portion of the non-coated portion 29 protrudes in the width direction of the negative electrode 12, thereby forming a plurality of negative electrode lead portions 21. That is, the plurality of negative electrode lead portions 21 are formed from the metal foil (copper foil in this embodiment) that constitutes the negative electrode current collector 25. The plurality of negative electrode lead portions 21 are formed integrally with the negative electrode current collector 25 by the press punching process.

[0027] The plurality of negative electrode lead portions 21 are arranged at intervals from one another in the longitudinal direction of the negative electrode 12. In this embodiment, the negative electrode lead portion 21 is not present at the end portion on the longitudinal winding start side, but may be arranged at either the end portion on the longitudinal winding start side or the end portion on the longitudinal winding end side. The longitudinal interval (pitch) between two adjacent negative electrode lead portions 21 increases toward the longitudinal winding end side. Furthermore, the length of the negative electrode lead portion 21 increases toward the longitudinal winding end side. In this way, as shown in FIG. 1 , when the negative electrode lead portion 21 is folded back radially inward, the radial positions of the tip portions 21 a of all the negative electrode lead portions 21 are approximately the same. The tip portions 21 a of the negative electrode lead portions 21 are welded to the bottom 68 of the outer can 16 in such a way that the positioning of the tip portions 21 a of the negative electrode lead portions 21 is facilitated during laser welding, which will be described later. At this time, it is not necessary that the tip portions 21a of all the negative electrode lead portions 21 are joined to the bottom 68 of the outer can 16. As long as the tip portion 21a of at least one negative electrode lead portion 21 is joined to the bottom 68 of the outer can 16, the tip portion 21a of the negative electrode lead portion 21 is joined to the bottom 68 of the outer can 16. a By joining the negative electrode lead portions 21 to each other, the tip portions 21a of all of the negative electrode lead portions 21 can be electrically connected to the bottom of the outer can 16. The longitudinal distance (pitch) between two adjacent negative electrode lead portions 21 may be the same for two or more sets of two adjacent negative electrode lead portions 21. The plurality of negative electrode lead portions 21 may also include two or more negative electrode lead portions having the same length.

[0028] <Preparation of non-aqueous electrolyte> A non-aqueous electrolyte solution was prepared by dissolving lithium hexafluorophosphate (LiPF6) as an electrolyte in a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) to a concentration of 1.0 mol / L.

[0029] <Preparing the sealing body> Thin portion 23a (see FIG. 1) was provided in the center of metal terminal plate 23, which was circular in plan view, and then terminal plate 23, annular insulating plate 24 (see FIG. 1), and sealing plate 27 were combined to produce sealing body 17. Thin portion 23a was joined to the center of the underside of sealing plate 27 by welding.

[0030] <Battery assembly> The positive electrode 11 and the negative electrode 12 were spirally wound with a polyolefin resin separator 13 interposed therebetween to produce an electrode assembly 14. A nickel metal plate 19 was then placed on the end face of the electrode assembly 14 from which the negative electrode lead portion 21 extended, and the negative electrode lead portion 21 was bent so that its tip portion 21a was aligned with the underside of the metal plate 19. The electrode assembly 14 was then inserted into an outer can 16, and a laser beam was applied axially from the outside of the bottom 68 of the outer can 16 to laser-weld the outer can 16 and the negative electrode lead portion 21. The laser welding can be performed under conditions conventionally used for welding cylindrical batteries. The wavelength and intensity of the laser beam used in the laser welding can be appropriately adjusted based on the thickness of the outer can 16, etc. This laser welding joined the bottom 68 of the outer can 16, the tip portions 21a of the multiple negative electrode lead portions 21, and the metal plate 19 into a single integrated unit. In this case, it is not necessary that the tip portions 21a of all the negative electrode lead portions 21 are directly joined to the bottom 68 of the outer can 16. Department 21 are integrated by laser welding, and at least one negative electrode lead Department 21 is bonded to the bottom 68 of the outer can 16, all of the negative electrode leads Department 21 is electrically connected to the bottom 68 of the outer can 16 .

[0031] FIG. 4 is a schematic diagram illustrating the position of the negative electrode lead portion 21 and the laser light irradiation area when the cylindrical battery 10 is viewed from the bottom 68. In FIG. 4, the hatched area is the laser light irradiation area. As shown in FIG. 4, in this example, the multiple negative electrode lead portions 21 were bent radially inward from multiple directions, so that, for example, four negative electrode lead portions 21 were positioned closest to the can bottom with a small circumferential gap between them. The multiple negative electrode lead portions 21 extended radially to near the radial center. The laser light irradiation area was circular (dot-shaped), and the laser light was irradiated onto a circular area having a predetermined radius centered on the radial center of the outer can 16.

[0032] In this way, the bottom 68 of the outer can 16, the plurality of negative electrode lead portions 21, and the metal plate 19 were joined. Thereafter, the positive electrode lead 20 connected to the positive electrode 11 was electrically connected to the sealing body 17 by welding. Next, after an electrolyte was poured into the outer can 16, the sealing body 17 was inserted into the outer can 16, and the open end of the outer can 16 and the sealing body 17 were crimped to produce the cylindrical battery 10 of the example.

[0033] [Essential configurations of the cylindrical battery of the present disclosure and their effects] The cylindrical battery 10 of the present disclosure includes a cylindrical outer can 16 with a bottom, an electrode assembly 14 housed within the outer can 16 and formed by winding an elongated positive electrode 11 (first electrode) and an elongated negative electrode 12 (second electrode) with a separator 13 interposed therebetween, and a metal plate 19 disposed between the bottom 68 of the outer can 16 and the electrode assembly 14. The cylindrical battery 10 also includes a plurality of negative electrode lead portions 21 (second electrode lead portions) extending from the negative electrode 12 toward the bottom 68. The tip portion 21a of each negative electrode lead portion 21 is sandwiched between the metal plate 19 and the bottom 68 and is electrically connected to the bottom 68.

[0034] Therefore, since the multiple negative electrode lead portions 21 are electrically connected to the outer can 16 without the metal plate 19, resistance loss in the path from the negative electrode 12 to the outer can 16 can be reduced, thereby reducing power loss. Furthermore, since at least one negative electrode lead portion 21 can be joined to the bottom 68 while the multiple negative electrode lead portions 21 are sandwiched between the metal plate 19 and the bottom 68, the joining can be performed reliably. Furthermore, when laser welding is used as the joining method, the metal plate 19 can be used as a laser welding receiver. That is, when the negative electrode lead portion 21 and the bottom 68 are joined by irradiating a laser beam from the outside of the can bottom, spatter occurs. However, this spatter can be received by the metal plate 19, and scattering of the spatter toward the electrode body 14 can be substantially suppressed or prevented. Therefore, intrusion of spatter into the electrode body can be substantially suppressed, and a high-quality cylindrical battery 10 can be produced.

[0035] [Preferable cylindrical battery configuration and its effects] Furthermore, it is preferable that the plurality of negative electrode lead portions 21 be made of the same metal foil as the metal foil that forms the negative electrode current collector 25 .

[0036] According to the above configuration, the plurality of negative electrode lead portions 21 can be formed simply and inexpensively.

[0037] In addition, it is preferable that at least one of the plurality of negative electrode lead portions 21 is joined to the metal plate 19 .

[0038] According to the above configuration, it is possible to further ensure the electrical connection between the plurality of negative electrode lead portions 21 and the outer can 16. In addition, it is possible to fix the metal plate 19 inside the outer can 16.

[0039] Furthermore, it is preferable that the plurality of negative electrode lead portions 21 and the bottom portion 68 are electrically connected by laser light irradiated from the outside of the outer can 16 .

[0040] [Other embodiments and modifications] The present disclosure is not limited to the above-described embodiments and their modifications, and various improvements and modifications are possible within the scope of the claims of the present application and their equivalents.

[0041] For example, in the above embodiment, the metal plate 19 and the bottom 68 of the outer can 16 are not directly joined, but the metal plate and the bottom of the outer can may be directly joined.

[0042] FIG. 5A is a schematic diagram showing the bottom 68 side of a cylindrical battery 10. FIG. 5B is a schematic diagram corresponding to FIG. 5A of a cylindrical battery 110 of a second embodiment. In this case, as shown in FIG. 5B, the length of each negative electrode lead portion 121 may be slightly shortened so that each negative electrode lead portion 121 can only reach a predetermined region radially inward of the metal plate 119 and cannot reach the radial center. A protrusion 119a may be provided below the center of the metal plate 119, protruding downward from the radial center where each negative electrode lead portion 121 cannot reach. This protrusion 119a may then be laser-welded to the bottom 68 of the outer can 16 using a laser beam irradiated from below the outer can 16. This configuration ensures reliable joining of the bottom 68 and the metal plate 119, further enhancing the electrical connection between the multiple negative electrode lead portions 121 and the outer can 16. Furthermore, the metal plate 119 can be reliably positioned within the outer can 16.

[0043] 5C, i.e., a schematic diagram corresponding to FIG. 5A of a cylindrical battery 210 of the third embodiment, each negative electrode lead portion 221 may not reach the radial center. Alternatively, a protrusion 219a that protrudes downward may be provided below the center of the metal plate 219. Then, a recess 277 having a shape corresponding to the shape of the protrusion 219a may be provided on the inner surface of the bottom 268 of the outer can 216, and the protrusion 219a may be fitted into the recess 277.

[0044] Alternatively, as shown in FIG. 5D, i.e., a schematic diagram corresponding to FIG. 5A of a cylindrical battery 310 of the fourth embodiment, each negative electrode lead portion 321 may not reach the radial center. Alternatively, a recess 319a recessed upward may be provided below the center of the metal plate 319. A protrusion 377 having a shape corresponding to the recess 319a may be provided on the inner surface of the bottom 368 of the outer can 316, and the protrusion 377 may fit into the recess 319a. Forming an uneven shape on the metal plates 219, 319 and the bottoms 268, 368 of the outer cans 216, 316, as in these embodiments, can improve the contact between the metal plates 219, 319 and the bottoms 268, 368. This further improves the stability of the welding and allows for precise positioning of the metal plates 219, 319.

[0045] FIG. 6A is a schematic diagram corresponding to FIG. 4 illustrating the laser beam irradiation region of a modified example, and FIGS. 6B and 6C are schematic diagrams corresponding to FIG. 4 illustrating the laser beam irradiation region of other modified examples. In FIGS. 6A, 6B, and 6C, the hatched regions are the laser beam irradiation region. As shown in FIG. 6A, laser welding may be performed by irradiating the laser beam from the outside of the can bottom in a ring shape. Alternatively, as shown in FIG. 6B, the plurality of negative electrode lead portions 421 may be bent from only one direction and then irradiated with laser beam. Alternatively, as shown in FIG. 6C, the laser beam irradiation region may be provided in a plurality of positions corresponding to the positions where the plurality of negative electrode lead portions 521 are bent.

[0046] In the example, the plurality of negative electrode lead portions 21 are formed integrally with the negative electrode current collector 25 by press-punching the metal foil. However, the plurality of negative electrode lead portions may also be formed by cutting the metal foil using a laser beam.

[0047] Alternatively, as shown in FIG. 7, that is, a schematic plan view corresponding to FIG. 3 of a modified negative electrode 612, a plurality of negative electrode lead portions 621 may be formed by joining a plurality of metallic (e.g., copper) lead plates to a non-coated portion 631 of a negative electrode current collector 625 that is adjacent to the negative electrode mixture layer 626 in the width direction.

[0048] Furthermore, although the bottom 68 of the outer can 16 was welded using laser welding, the bottom of the outer can may also be welded using resistance welding or ultrasonic welding. Furthermore, although nickel was used as the material for the metal plate 19, other metals such as cast iron, copper, or nickel-plated iron may also be used as the material for the metal plate.

[0049] Furthermore, in the electrode assembly 14, the axial length of the separator 13 is longer than the axial length of the positive electrode 11 and the axial length of the negative electrode 12. Therefore, even if a metal plate 19 is placed below the electrode assembly 14, the separator 13 will not get in the way and the positive electrode 11 and the negative electrode 12 will not be short-circuited via the metal plate 19. However, it is preferable that an insulating layer be placed between the metal plate 19 and the electrode assembly 14. Examples of insulating layers include an insulating plate, insulating tape, and an insulating coating film.

[0050] In order to reduce the electrical resistance of the path electrically connecting the electrode body and the outer can, it is preferable to make the negative electrode lead portion protrude from the winding start side in the longitudinal direction of the negative electrode. The negative electrode lead portion formed on the winding start side in the longitudinal direction of the negative electrode can be, for example, folded back radially outward along the upper surface of the metal plate and then folded back radially inward along the lower surface of the metal plate, thereby enabling electrical connection with the bottom of the outer can.

[0051] Alternatively, a through hole may be provided in the metal plate at a position overlapping the hollow portion of the electrode body in the axial direction, and one or more negative electrode lead portions protruding from the winding start side of the negative electrode in the longitudinal direction may be passed through the through hole in the metal plate and then welded to the bottom of the outer can.

[0052] In one embodiment of the present disclosure, the case where the second electrode electrically connected to the outer can 16 is a negative electrode has been described. However, the first electrode may be a negative electrode and the second electrode may be a positive electrode. In this case, the outer can serves as the positive electrode terminal. [Explanation of symbols]

[0053] 10,110,210,310 Cylindrical battery, 11 Positive electrode, 12,612 Negative electrode, 13 Separator, 14 Electrode body, 15 Battery case, 16,216 Outer can, 17 Sealing body, 18 Insulating plate, 19,119,219,319 Metal plate, 20 Positive electrode lead, 21,121,221,321,421,521,621 Negative electrode lead portion, 21a Tip portion, 23 Terminal plate, 23a Thin portion, 24 Insulating plate, 25,625 Negative electrode current collector, 26,626 Negative electrode mixture layer, 27 Sealing plate, 28 Gasket, 29 Non-coated portion, 30 Bottomed cylindrical portion, 31 Peripheral portion, 33 Shoulder portion, 35 Grooved portion, 39 Band portion, 68,268 Bottom portion, 119a,219a Protruding portion, 277 Recessed portion, 319a Recessed portion, 377 Convex portion, 631 Non-coated portion.

Claims

1. a cylindrical outer can with a bottom; an electrode assembly housed in the outer can, the electrode assembly being formed by winding a first elongated electrode and a second elongated electrode having opposite polarities with a separator interposed therebetween; a metal plate disposed between the bottom of the outer can and the electrode body; a plurality of second electrode lead portions extending from the second electrode toward the bottom portion, the second electrode lead is bent toward the metal plate so as not to extend beyond the radial center of the electrode body; a cylindrical battery, wherein a tip end of each of the second electrode lead portions is sandwiched between the metal plate and the bottom portion and is electrically connected to the bottom portion.

2. The cylindrical battery according to claim 1 , wherein the plurality of second electrode lead portions are formed from a metal foil that constitutes a current collector of the second electrode.

3. The cylindrical battery according to claim 1 or 2, wherein at least one of the plurality of second electrode lead portions is joined to the metal plate.

4. The cylindrical battery according to claim 1 , wherein an insulating layer is disposed between the metal plate and the electrode body.

5. The cylindrical battery according to claim 1 , wherein the metal plate is joined to the bottom without the second electrode lead portion being interposed therebetween.

6. The cylindrical battery according to claim 1 , wherein the second electrode lead portions and the bottom portion are electrically connected by laser light irradiated from outside the outer can.

7. A method for manufacturing a cylindrical battery according to any one of claims 1 to 5, a cylindrical battery manufacturing method, wherein the plurality of second electrode lead portions and the bottom portion are electrically connected by irradiating them with laser light from outside the outer can.

Images