Method for manufacturing cylindrical battery, and cylindrical battery

Abstract

This method for manufacturing a cylindrical battery (10) includes a welding step for welding a negative-electrode core-exposed part (41) constituting a height-direction end of an electrode body (14) to a lower current collector plate (19). The method for manufacturing the cylindrical battery (10) includes performing, before the welding step, a first bending step for bending the negative-electrode core-exposed part (41) inward in the radial direction, and a second bending step for bending a core-exposed portion (41a) that protrudes toward a hollow section (14a) of the electrode body (14) due to the first bending step toward the height-direction center of the electrode body (14).

Description

Cylindrical battery manufacturing method and cylindrical battery

[0001] The present disclosure relates to a method for manufacturing a cylindrical battery, and a cylindrical battery.

[0002] A conventional cylindrical battery is described in Patent Document 1. In this cylindrical battery, the bottom end of the outer can in the axial direction of the electrode assembly is configured as a negative electrode, and this bottom end is pressed against the negative electrode current collector. In this way, a wide longitudinal area of ​​the strip-shaped negative electrode is electrically connected to the negative electrode current collector, thereby shortening the current path on the negative electrode side and reducing the electrical resistance of the cylindrical battery.

[0003] JP 2014-186912 A

[0004] The present inventors have discovered the following problem. By configuring one axial end of the electrode body as a negative electrode substrate exposed portion, welding the negative electrode substrate exposed portion to a negative electrode current collector plate, and then welding the negative electrode current collector plate to the bottom of an outer can, a wide longitudinal area of ​​the negative electrode can be reliably and stably electrically connected to the negative electrode current collector plate. Furthermore, by bending the negative electrode substrate exposed portion of the electrode body so that it is tilted radially inward when welding the negative electrode substrate exposed portion to the negative electrode current collector plate, the bent portion can be made to abut favorably with the negative electrode current collector plate, allowing for reliable and easy welding.

[0005] In this context, if the exposed portion of the negative electrode substrate on the inner periphery of the electrode body is intentionally not tilted radially inward to prevent it from being formed, it is possible to determine whether the exposed portion of the negative electrode substrate on the outer periphery of the electrode body has been reliably welded by checking a scanning ion microscope (SIM) image, etc., using the portion where the forming was not performed as a reference. However, in this case, it is difficult to achieve good contact of the exposed portion of the negative electrode substrate on the inner periphery with the negative electrode current collector plate, making it difficult to stably weld the exposed portion of the negative electrode substrate on the inner periphery.

[0006] On the other hand, if the negative electrode substrate exposed portion is formed up to its inner periphery and then welded to the negative electrode current collector plate, good welding of the negative electrode substrate exposed portion and the negative electrode current collector plate can be achieved. However, in this case, the presser bar inserted into the hollow portion of the electrode body to press the negative electrode current collector plate against the can bottom when welding the negative electrode current collector plate to the can bottom is likely to interfere with the inner periphery side of the negative electrode substrate exposed portion that protrudes radially into the hollow portion, making it difficult to stably weld the negative electrode current collector plate to the can bottom.

[0007] Therefore, an object of the present disclosure is to provide a method for manufacturing a cylindrical battery that can easily achieve good welding between the electrode core exposed portion and the current collector plate and can suppress interference between the electrode core exposed portion and the presser rod when welding the current collector plate to the can bottom. Another object of the present disclosure is to provide a highly reliable cylindrical battery in which a wide longitudinal area of ​​the electrode core exposed portion is reliably and stably joined to the current collector plate.

[0008] In order to solve the above problems, the manufacturing method of a cylindrical battery according to the present disclosure is a manufacturing method of a cylindrical battery that includes a welding step of welding an exposed portion of an electrode core that constitutes the end portion of an electrode body in the height direction to a current collector plate, and before the welding step, a first bending step of bending the exposed portion of the electrode core radially inward, and a second bending step of bending the exposed portion of the core that protrudes into the hollow portion of the electrode body by the first bending step toward the center of the electrode body in the height direction.

[0009] The cylindrical battery disclosed herein also includes an electrode body in which a long first electrode and a long second electrode are wound with a separator interposed therebetween, with one axial end portion being formed by a first electrode core exposed portion of the first electrode, an outer can housing the electrode body, and a current collector plate having a first surface to which the first electrode core exposed portion is joined and a second surface to which the bottom of the outer can is joined, and the innermost core portion of the first electrode core exposed portion that is located at the innermost periphery of the first electrode is bent toward the center of the axial direction of the electrode body.

[0010] The cylindrical battery manufacturing method according to the present disclosure facilitates good welding of the electrode substrate exposed portion and the current collector plate, and also suppresses interference between the electrode substrate exposed portion and the presser rod when welding the current collector plate to the can bottom. Furthermore, the cylindrical battery according to the present disclosure ensures that a wide longitudinal area of ​​the electrode substrate exposed portion is reliably and stably joined to the current collector plate, resulting in high reliability.

[0011] FIG. 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 perspective view of a lower current collector plate. FIG. 4 is a plan view of the lower current collector plate as viewed from below. FIG. 5 is a plan view illustrating a first bending step, and is a plan view of the electrode body as viewed from below in the height direction (below in the axial direction) during the first bending step. FIG. 6 is a plan view showing the state of the end face of the electrode body on the negative electrode substrate exposed portion side after the first bending step is completed. FIG. 7 is a schematic view illustrating a second bending step, and is a schematic view including a schematic half axial cross-sectional view of the lower side of the electrode body. FIG. 8 is a schematic view illustrating a problem discovered by the present inventors. FIG. 9 is a schematic view illustrating a problem discovered by the present inventors. FIG. 10 is a schematic cross-sectional view of the lower side of the electrode body in the axial direction of the cylindrical battery of the embodiment.

[0012] Hereinafter, with reference to the drawings, embodiments of a cylindrical battery according to the present disclosure and a method for manufacturing a cylindrical battery according to the present disclosure will be described in detail. Note that, although a cylindrical lithium-ion battery including a non-aqueous electrolyte is exemplified below as a cylindrical battery embodiment, the cylindrical battery according to the present disclosure is not limited thereto. The cylindrical battery according to the present disclosure may be a primary battery or a secondary battery. The cylindrical battery according to the present disclosure may be a battery using an aqueous electrolyte or a battery using a non-aqueous electrolyte.

[0013] 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 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 do not necessarily match between different drawings. In this specification, the side of the sealing body 17 in the axial direction (height direction) is referred to as the upper side, and the side of the bottom 68 of the outer can 16 in the axial direction is referred to as the lower side. Furthermore, in the following description, the radial direction refers to the radial direction of the outer can 16, which coincides with the radial direction of the cylindrical battery 10. Furthermore, the circumferential direction refers to the circumferential direction of the outer can 16, which coincides with the circumferential direction of the cylindrical battery 10. Furthermore, among the components described below, components not recited in the independent claims representing the highest concepts are optional components and not required 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 outer can 16 with a bottom that houses the electrode assembly 14 and the non-aqueous electrolyte, and a sealing body 17 that seals the outer can 16 via a gasket 28.

[0015] The electrode assembly 14 includes a long positive electrode 11, a long 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. In this embodiment, the negative electrode 12 constitutes a first electrode, and the positive electrode 11 constitutes a second electrode.

[0016] 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

[0017] 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.).

[0018] Fig. 2 is a perspective view showing a portion of the electrode body 14 and the positive electrode lead 20. As shown in Fig. 2, the electrode body 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. One or more positive electrode leads 20 are joined to the positive electrode 11, and preferably six or more positive electrode leads 20 are joined, and in this embodiment, eight positive electrode leads 20 are joined to the positive electrode 11 at intervals from one another in the longitudinal direction of the positive electrode.

[0019] The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium precipitation. The negative electrode 12 is formed to be longer than the positive electrode 11 in the winding direction and axial direction. Two separators 13 are formed to be 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.

[0020] 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 inner winding end to the outer winding end in the negative electrode longitudinal direction of the negative electrode 12. The negative electrode core exposed portion 41 constitutes a first electrode core exposed portion. The lower end of the electrode body 14 in the axial direction (height direction) is constituted by the negative electrode core exposed portion 41. The negative electrode 12 may constitute the inner winding end of the electrode body 14. However, typically, the separator 13 extends beyond the inner winding end of the negative electrode 12, and the inner winding end of the separator 13 becomes the inner winding end of the electrode body 14.

[0021] 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.

[0022] 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.

[0023] Examples of conductive agents contained in the positive electrode mixture layer include carbon black such as acetylene black and ketjen black, and carbon materials such as graphite. Examples of binders 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.

[0024] The positive electrode 11 has one or more positive electrode core exposed portions where the positive electrode core is exposed, and in this embodiment, has eight positive electrode core exposed portions arranged at intervals in the longitudinal direction of the positive electrode. Positive electrode leads 20 are joined to the positive electrode core exposed portions one by one by ultrasonic welding or the like. Effectively shortening the positive electrode side current path increases the reduction in electrical resistance, so it is preferable that the center positions of the eight positive electrode leads 20 in the longitudinal direction of the positive electrode be arranged at approximately equal intervals in the longitudinal direction of the positive electrode.

[0025] As shown in FIG. 2 , 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. The negative electrode core 40 can be made of 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 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 to 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.

[0026] 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. To facilitate increased capacity, the negative electrode active material of the negative electrode mixture layer 42 preferably contains a Si material containing silicon (Si) particles, and the mass ratio of Si element in the negative electrode mixture layer 42 is preferably 5.0 mass% or more. Furthermore, it is preferable that 3.0 mass% or more of the negative electrode mixture layer be composed of silicon oxide. The negative electrode active material may also include a metal other than Si that alloys with lithium, an alloy containing such a metal, or a compound containing such a metal.

[0027] 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. The negative electrode mixture layer 42 may contain, in addition to SBR or the like, CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, or the like.

[0028] 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.

[0029] As shown in Figure 1, the battery 10 includes an annular insulating plate 18 on the upper side of the electrode assembly 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 (positive electrode current collector plate) 26 and a terminal cap 27. The upper current collector plate 26 is a metal annular plate member and has a through-hole 26a in its radial center.

[0030] Terminal cap 27 is a metal plate-like member without a through hole and is located axially above sealing body 17. The axially upper end face of terminal cap 27 is exposed to the outside except for the outer edge, and this exposed portion forms the positive electrode terminal. Sealing body 17 further has a metal plate 25. Metal plate 25 is a metal annular member with a through hole.

[0031] Each positive electrode lead 20 is bent from the positive electrode 11 through the through hole 26a of the upper current collector 26 so as to fit along the upper surface of the upper current collector 26. The tip of each positive electrode lead 20 is sandwiched between the upper surface of the upper current collector 26 and the lower surface of the metal plate 25. Each positive electrode lead 20 is joined to the upper surface of the upper current collector 26. The upper current collector 26 and the metal plate 25 are also joined, and each positive electrode lead 20 and the metal plate 25 are also joined. These joinings can be achieved, for example, by laser welding the tip of each positive electrode lead 20 sandwiched between the upper current collector 26 and the metal plate 25 by irradiating the metal plate 25 with a laser beam in the axial direction from above. By laser welding the tip of the positive electrode lead 20 sandwiched between the upper current collector 26 and the metal plate 25, the positive electrode lead 20 can be reliably and easily welded and joined to the upper current collector 26.

[0032] The sealing body 17 has a laminated portion 30 on its outer periphery, in which a terminal cap 27 and an upper current collector plate 26 are laminated. By irradiating the laminated portion 30 with a laser beam from above, the terminal cap 27 and the upper current collector plate 26 are laser-welded and electrically connected. The annular upper surface of the upper current collector plate 26 has an annular recess 31 radially inward from the laminated portion 30. Because the upper surface of the upper current collector plate 26 has the recess 31 recessed downward, a space is provided between the terminal cap 27 and the recess 31 of the upper current collector plate 26. Each positive electrode lead 20 is joined to the upper current collector plate 26 within the recess 31. The upper current collector plate 26 does not need to be joined to the metal plate 25, and the positive electrode lead 20 does not need to be joined to the metal plate 25. The battery does not need to have a metal plate 25. The positive electrode lead 20 may also be joined to the lower surface of the upper current collector plate 26.

[0033] The battery 10 has a metal lower current collector plate (negative electrode current collector plate) 19 axially below the electrode body 14. FIG. 3 is a perspective view of the lower current collector plate 19, and FIG. 4 is a plan view of the lower current collector plate 19 as viewed from below. As shown in FIGS. 3 and 4 , the lower current collector plate 19 has a flat plate portion 51 that is approximately circular in plan view in the radial center. The flat plate portion 51 may have any flat plate shape other than a circular shape, such as a rectangular shape. The lower current collector plate 19 also has multiple radially extending portions 53 connected to the flat plate portion 51. In this embodiment, the lower current collector plate 19 has four radially extending portions 53. The radially extending portions 53 have a columnar shape and extend radially. Preferably, the multiple radially extending portions 53 are arranged at equal intervals in the circumferential direction.

[0034] As shown in FIG. 1 , the radially extending portion 53 is connected to the flat plate portion 51 via a step portion 54, and the bottom surface of the flat plate portion 51 is located below the bottom surface of the radially extending portion 53. This allows the bottom surface of the flat plate portion 51 to be tightly attached to the inner surface of the bottom 68 of the outer can 16 without any gaps during bonding of the flat plate portion 51, as described below, making it easier to achieve good bonding of the flat plate portion 51. As shown in FIG. 3 , the radially extending portion 53 has a protrusion 56 on its upper side. The protrusion 56 is provided at the widthwise center of the radially extending portion 53 and protrudes in the thickness direction. The protrusion 56 extends radially. A groove 57 extending radially is provided on the lower surface of the radially extending portion 53 at a location overlapping the protrusion 56 in the thickness direction. The widthwise center of the lower surface of the radially extending portion 53 is pressed upward in the thickness direction by a predetermined radial distance. By this press working, the protrusions 56 and the grooves 57 are formed.

[0035] The negative electrode substrate exposed portion 41 (see FIG. 2 ) is joined to the protrusion portion 56. More specifically, with the negative electrode substrate exposed portion 41 constituting the lower end of the electrode body 14 pressed against the protrusion portion 56, a laser beam is irradiated from below toward the bottom of the groove portion 57. This laser beam irradiation joins the negative electrode substrate exposed portion 41 of the electrode body 14 to the protrusion portion 56 by laser welding over a wide radial range.

[0036] Thereafter, a presser bar 35 (see FIG. 7( c) ) inserted from above into the hollow portion 14 a of the electrode body 14 (see FIG. 1 ) presses the upper surface of the flat portion 51 against the inner surface of the bottom portion 68 of the outer can 16. In this state, laser light is irradiated from below the outer can 16 to join the bottom portion 68 to the lower current collector plate 19 by laser welding. As a result, the negative electrode 12 of the electrode body 14 is electrically connected to the outer can 16 via the lower current collector plate 19. As shown in FIG. 1 , the negative electrode core exposed portion 41 has a core innermost periphery 41 a positioned at the innermost periphery of the negative electrode 12, which is bent toward the center in the axial direction of the electrode body 14 and is spaced apart from the lower current collector plate 19. By joining the negative electrode core exposed portion 41 over a wide area to the upper surface of the lower current collector plate 19, it is possible to prevent current from flowing long distances along the longitudinal direction of the elongated negative electrode 12, thereby reducing the electrical resistance of the battery 10.

[0037] As shown in FIG. 1 , the outer can 16 has a cylindrical portion 39 and a bottom portion 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 outer edge of the sealing body 17, and extends radially inward at the upper end of the cylindrical portion 39.

[0038] The space 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 sealing material for maintaining airtightness inside the battery and as an insulating material for insulating the outer can 16 and the sealing body 17. 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 19 serves as a negative electrode terminal.

[0039] 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 increasing the safety of the battery 10. The thin, easily breakable portion may also be provided on the terminal cap.

[0040] In the above description, the sealing body 17 does not have a rupture plate, and an easily breakable portion 68a is provided on the bottom 68 of the outer can. However, the bottom of the outer can does not have to have an easily breakable portion. The sealing body may have two rupture plates (a lower valve body and an upper valve body) and a convex terminal cap that covers the rupture plate. Alternatively, the sealing body may be composed of only a rupture plate, or may have a structure in which an internal terminal plate, an insulating plate, and a rupture plate are stacked in this order from the electrode body side.

[0041] Next, a detailed description will be given of a method for joining the electrode body 14 and the lower current collector plate 19 in the battery 10, and a method for joining the lower current collector plate 19 and the bottom 68 of the outer can 16. First, a first bending step is performed in which the negative electrode substrate exposed portion 41 constituting the lower end of the electrode body 14 is bent radially inward. Figure 5 is a plan view illustrating the first bending step, showing the electrode body 14 as viewed from below in the height direction (below in the axial direction) during the first bending step.

[0042] Referring to FIG. 5 , the bending of the negative electrode substrate exposed portion 41 radially inward in the first bending step is performed as follows. First, the electrode assembly 14 is fixed at a predetermined position in three-dimensional space by a chuck device (not shown). Examples of the chuck device that can be used include a mechanical chuck and a scroll chuck. Next, a plurality of flat bending plates 80, 81 (not shown) are moved from the radially outer side to the radially inner side of the electrode assembly 14 on a plane substantially perpendicular to the height direction of the electrode assembly by using a plurality of linear actuators (not shown). At this time, the bending plates 80, 81 are moved at a height position where they contact the negative electrode substrate exposed portion 41. In this way, the negative electrode substrate exposed portion 41 is tilted radially inward, bent radially inward, and formed radially inward.

[0043] In this embodiment, the negative electrode substrate exposed portion 41 is bent radially inward using four first bending plates 80 and four second bending plates 81. The four first bending plates 80 include a main body 80a having an elongated rectangular planar shape and a tapered tip portion 80b having an isosceles trapezoidal planar shape. The four first bending plates 80 are arranged at equal intervals in the circumferential direction and move from the radially outer side to the radially inner side of the electrode body 14 with their central axes 80c in FIG. 5 substantially aligned with the radial direction of the electrode body 14.

[0044] Because the tip portions 80b of the first folded plates 80 are tapered, interference between adjacent first folded plates 80 in the circumferential direction can be prevented even when the first folded plates 80 are moved to a position where they overlap in the height direction with the hollow portion 14a of the electrode body 14. For this reason, the core innermost peripheral portion 41a (see FIG. 1) located at the innermost periphery of the negative electrode core exposed portion 41 is also bent radially inward and formed radially inward.

[0045] On the other hand, the tip portion 81a of the second folded plate 81 has the shape of a right-angled isosceles triangle with an apex angle of 90 degrees. In Fig. 5, the second folded plate 81 moves from the radially outer side to the radially inner side of the electrode body 14 in a state where the extension line of the bisector 81b of the right-angled isosceles triangle forms an angle of approximately 45 degrees with the central axis 80c of the first folded plate 80. Due to the movement of the tip portion 81a of the second folded plate 81, a part of the negative electrode core exposed portion 41 in a circumferential region sandwiched between the movement regions of the circumferentially adjacent first folded plates 80 is tilted and bent radially inward, and is formed radially inward.

[0046] The eight folded plates 80, 81 may simultaneously move from the radially outer side to the radially inner side, or the four first folded plates 80 may move from the radially outer side to the radially inner side after the four second folded plates 81 move from the radially outer side to the radially inner side, or the four second folded plates 81 may move from the radially outer side to the radially inner side after the four first folded plates 80 move from the radially outer side to the radially inner side.

[0047] Fig. 6 is a plan view showing the state of the end surface 85 on the negative electrode core exposed portion 41 side of the electrode body 14 after the first bending step is completed. In Fig. 6, the light gray region 46 indicates the region where the negative electrode core exposed portion 41 bent radially inward is present, and the dark gray region 47 indicates the region where the negative electrode core exposed portion 41 is present, protruding downward in the height direction from the light gray region 46. As shown in Fig. 6, in this embodiment, four substantially V-shaped protruding portions of the negative electrode core exposed portion 41 (the dark gray regions 47) are present on the end surface 85 of the electrode body 14 after the first bending step is completed.

[0048] After the first bending step is completed, the second bending step is performed. Fig. 7 is a schematic diagram illustrating the second bending step, including a schematic half-sectional view of the lower side of the electrode body 14 in the axial direction. Fig. 7 is a schematic half-sectional view passing through the negative electrode core exposed portion 41 corresponding to the central axis 80c of the first bending plate 80. In Fig. 7 and the following Figs. 8 to 10, only the negative electrode 12 of the electrode body 14 is illustrated, and in these figures, the region indicated by diagonal hatching is the region where the negative electrode mixture layer is disposed on the negative electrode core.

[0049] 7( a) shows the state of the lower side of the negative electrode after the first bending step. As shown in FIG. 7( a), the negative electrode substrate exposed portion 41 is bent radially inward and formed radially inward. In the second bending step, as shown in FIG. 7( b), the substrate innermost periphery 41a that protruded toward the radial center of the electrode body 14 in the first bending step is bent toward the center in the height direction of the electrode body 14 (upward in the axial direction).

[0050] The bending of the core innermost periphery 41a upward is performed using a core bending device 75 having a chuck device (not shown), a rotary stage 71, and a linear actuator 72 installed on the installation surface 71a of the rotary stage 71. Specifically, the electrode body 14 is fixed in a predetermined three-dimensional position using the chuck device. Next, with the installation surface 71a of the rotary stage 71 extending on a plane approximately perpendicular to the height direction of the electrode body 14, the rod 72a, which has a substantially circular cross section, of the linear actuator 72 is extended and inserted into the hollow portion 14a from the side of the electrode body 14 where the negative electrode core exposed portion is formed, and the core innermost periphery 41a is bent upward. The rod 72a forms a cylindrical jig.

[0051] The outer circumferential surface of the tip 72b on the insertion side of the rod 72a is tapered so that the innermost circumferential portion 41a of the core body is gradually bent upward. This prevents excessive force from being applied instantaneously to the innermost circumferential portion 41a of the core body, thereby preventing damage to the innermost circumferential portion 41a due to bending upward. The outer circumferential surface of the tip on the insertion side of the rod may be a cylindrical outer circumferential surface, or the outer circumferential surface of the tip on the insertion side of the rod may not be tapered.

[0052] The rotary stage 71 can be rotated by a motor with the central axis of the rod 72a aligned with the rotation axis. The rotary stage 71 rotates with at least the tip of the rod 72a inserted into the hollow portion 14a, causing the rod 72a to rotate. By rotating the rotary stage 71, the core innermost circumferential portion 41a can be reliably bent upward in the axial direction. The linear actuator 72 may be installed on a flat plate instead of the rotary stage 71, or the rod 72a may not rotate.

[0053] Next, the negative electrode substrate exposed portion 41 is laser-welded to the lower current collecting plate 19 shown in Figures 3 and 4 by the method described above. This laser welding is performed by irradiating laser light onto the groove portion 57 from below while the negative electrode substrate exposed portion 41, which has been bent radially inward by the movement of the first bending plate 80, is pressed against the upper surface of the protrusion portion 56 (see Figure 3). By pressing the negative electrode substrate exposed portion 41 against the upper surface of the protrusion portion 56, it is possible to prevent the region (protrusion portion) 47 shown in dark gray in Figure 6 from interfering with this laser welding.

[0054] Finally, the lower current collector plate 19, to which the electrode body 14 has been welded, is laser-welded to the bottom 68 of the outer casing 16. This laser welding is performed by inserting the presser bar 35 into the hollow portion 14a from above in the direction indicated by arrow A in Figure 7(c) and pressing the upper surface of the flat portion 51 of the lower current collector plate 19 downward until it is in contact with the bottom 68 of the outer casing 16 (not shown in Figure 7), and then irradiating the bottom 68 with laser light from outside in the axial direction.

[0055] Next, the problem found by the present inventors and the effects of the technique of the present disclosure will be described with reference to Figures 8 and 9. When welding the exposed portion of the negative electrode substrate to the lower current collector plate, if the exposed portion of the negative electrode substrate of the electrode body is bent so as to bend radially inward, the abutment between the bent portion and the negative electrode current collector plate can be improved, and welding can be performed reliably and easily.

[0056] 8( a), if the negative electrode substrate exposed portion 141a on the inner periphery of the electrode body 114 is intentionally not bent, it becomes easy to determine whether the negative electrode substrate exposed portion 141b on the outer periphery of the electrode body 114 has been reliably welded by checking a scanning ion microscope image, etc., using the unbent portion as a reference. However, in this case, as shown in FIG. 8( b), it is difficult to achieve good contact of the negative electrode substrate exposed portion 141a on the inner periphery with the lower current collector plate 19, making it difficult to stably weld the negative electrode substrate exposed portion 141a on the inner periphery.

[0057] On the other hand, as shown in FIG. 9( a), if the negative electrode core exposed portion 241 is bent to the inner periphery of the negative electrode core exposed portion 241 and then welded to the lower current collector plate 19, good welding can be achieved between the negative electrode core exposed portion 241 and the lower current collector plate 19. However, in this case, as shown in FIG. 9( b), a presser rod 35 inserted into the hollow portion 14 a (see FIG. 1 ) to press the lower current collector plate 19 against the bottom 68 of the outer can 16 (see FIG. 1 ) during laser welding between the lower current collector plate 19 and the bottom 68 is likely to interfere with the inner periphery side negative electrode core exposed portion 241 a protruding into the hollow portion 14 a, making it difficult to stably weld the lower current collector plate 19 and the bottom 68. Furthermore, there is a risk that the inner periphery side negative electrode core exposed portion 241 a will come into contact with the presser rod 35, which could reduce the reliability of the battery 210.

[0058] In contrast, in the technology disclosed herein, in the first bending step, the negative electrode core exposed portion 41 is bent up to the core innermost portion 41a located at the innermost periphery of the negative electrode core exposed portion 41, and then a second bending step is performed in which the core innermost portion 41a that protrudes into the hollow portion 14a of the electrode body 14 in the first bending step is bent toward the center of the electrode body 14 in the height direction.

[0059] Therefore, in the first bending step, the negative electrode substrate exposed portion 41 is bent to the innermost circumference, so that the negative electrode substrate exposed portion 41 can be stably pressed radially inward against the protrusion portion 56, and laser welding can be performed stably and reliably over a wide radial range. Therefore, the negative electrode substrate exposed portion 41 can be electrically connected to the lower current collector plate 19 stably and reliably over a wide radial range, so that the current path on the negative electrode side can be effectively shortened and the electrical resistance of the battery 10 can be effectively reduced.

[0060] Furthermore, in the second bending step, the core innermost periphery 41a that protruded into the hollow portion 14a of the electrode body 14 in the first bending step is bent axially upward, which prevents the core innermost periphery 41a from interfering with the presser bar 35, thereby enabling stable and reliable laser welding of the lower current collecting plate 19 to the bottom 68 of the outer can 16. Furthermore, because the core innermost periphery 41a can be prevented from interfering with the presser bar 35, the reliability of the battery 10 is improved.

[0061] 10 , since interference between the negative electrode core exposed portion 41 and the presser rod 35 can be effectively prevented during laser welding of the lower current collector plate 19 and the bottom 68, it is preferable that the radial distance L1 between the radial center 90 of the mix placement portion 45 where the negative electrode mix layer 42 is placed in the negative electrode innermost periphery portion 88 located at the innermost periphery of the negative electrode 12 and the tip 41 b of the core innermost periphery portion 41 a be 2 / 3 or less of the shortest radial distance L2 between the center 90 and the central axis 95 of the outer can 16. Furthermore, since interference between the negative electrode core exposed portion 41 and the presser rod 35 can be almost reliably prevented during laser welding of the lower current collector plate 19 and the bottom 68, it is even more preferable that the radial distance L1 between the center 90 and the tip 41 b of the core innermost periphery portion 41 a be 2 / 5 or less of the shortest radial distance L2 between the center 90 and the central axis 95.

[0062] 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, the first electrode is the negative electrode 12, the outer can 16 serves as the negative electrode terminal, and the second electrode is the positive electrode 11, and the top surface of the sealing body 17 serves as the positive electrode terminal. However, the first electrode may be the positive electrode, the outer can serves as the positive electrode terminal, and the second electrode may be the negative electrode, and the top surface of the sealing body serves as the negative electrode terminal.

[0063] The manufacturing method of the cylindrical battery according to the present disclosure may also be configured as follows. Configuration 1: A manufacturing method of a cylindrical battery including a welding step of welding an electrode core exposed portion constituting an end portion of an electrode body in the height direction to a current collector plate, wherein a first bending step of bending the electrode core exposed portion radially inward and a second bending step of bending the exposed portion of the electrode core that protrudes into the hollow portion of the electrode body in the first bending step toward the center of the electrode body in the height direction are performed before the welding step. Configuration 2: A manufacturing method of a cylindrical battery according to Configuration 1, wherein in the first bending step, the electrode core exposed portion is bent up to the innermost core portion located at the innermost periphery of the electrode core exposed portion. Configuration 3: A manufacturing method of a cylindrical battery according to Configuration 1 or 2, wherein the second bending step is performed by inserting a cylindrical jig having an outer diameter smaller than the outer diameter of a winding core used to wind the electrode body into the hollow portion from the end side in the height direction. Configuration 4: The method for manufacturing a cylindrical battery according to Configuration 3, wherein the outer peripheral surface of the tip of the insertion side of the jig is tapered. Configuration 5: The method for manufacturing a cylindrical battery according to Configuration 3 or 4, wherein the jig is rotated with at least the tip side of the jig inserted in the hollow portion.

[0064] REFERENCE SIGNS LIST 10 Battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 14a Hollow portion, 16 Outer can, 17 Sealing body, 18 Insulating plate, 19 Lower current collector plate, 20 Positive electrode lead, 22 Grooved portion, 25 Metal plate, 26 Upper current collector plate, 26a Through hole, 27 Terminal cap, 28 Gasket, 29 Shoulder portion, 30 Laminated portion, 31 Recessed portion, 35 Presser rod, 39 Cylindrical portion, 40 Negative electrode core, 41 Negative electrode core exposed portion, 41a Core innermost periphery, 41b Tip of core innermost periphery, 42 Negative electrode mixture layer, 45 Mixture placement portion, 51 Flat portion, 53 Radially extending portion, 54 step portion, 56 ridge portion, 57 groove portion, 68 bottom portion, 68a easily breakable portion, 71 rotation stage, 71a installation surface, 72 linear actuator, 72a rod, 72b tip portion of rod, 75 core bending device, 80 first bending plate, 80a main body of first bending plate, 80b tip portion of first bending plate, 80c central axis, 81 second bending plate, 81a tip portion of second bending plate, 81b bisector, 85 end face, 88 innermost peripheral portion of negative electrode, 90 radial center of mixture arrangement portion, 95 central axis of outer can.

Claims

1. A method for manufacturing a cylindrical battery, which includes a welding step of welding the exposed electrode core portion that constitutes the end portion of the electrode body in the height direction to a current collector plate, and which performs a first bending step of bending the exposed electrode core portion radially inward and a second bending step of bending the exposed core portion that protrudes into the hollow portion of the electrode body in the first bending step toward the center of the electrode body in the height direction before the welding step.

2. The method for manufacturing a cylindrical battery according to claim 1, wherein in the first bending step, the electrode substrate exposed portion is bent up to the innermost peripheral portion of the electrode substrate exposed portion that is located at the innermost periphery.

3. A method for manufacturing a cylindrical battery as described in claim 1 or 2, wherein the second bending step is performed by inserting a cylindrical jig having an outer diameter smaller than the outer diameter of the winding core used to wind the electrode body into the hollow portion from the end side in the height direction.

4. The method for manufacturing a cylindrical battery according to claim 3, wherein the outer peripheral surface of the tip of the insertion side of the jig is tapered.

5. The method for manufacturing a cylindrical battery according to claim 3, wherein the jig is rotated with at least the tip end of the jig inserted into the hollow portion.

6. A cylindrical battery comprising: an electrode assembly in which a long first electrode and a long second electrode are wound with a separator interposed therebetween, one axial end portion of which is constituted by a first electrode core exposed portion of the first electrode; an outer can housing the electrode assembly; and a current collector plate having a first surface to which the first electrode core exposed portion is joined and a second surface to which the bottom of the outer can is joined, wherein the innermost core portion of the first electrode core exposed portion that is located at the innermost periphery of the first electrode is bent toward the center in the axial direction of the electrode assembly.

7. A cylindrical battery as described in claim 6, wherein the radial distance between the radial center of the mixture arrangement portion, in which the electrode mixture layer is arranged, of the innermost electrode portion located at the innermost periphery of the first electrode, and the tip of the innermost peripheral portion of the core is 2 / 3 or less of the shortest radial distance between the center and the central axis of the outer can.

8. The cylindrical battery according to claim 7, wherein the radial distance between the center and the tip of the innermost peripheral portion of the core is 2 / 5 or less of the shortest radial distance between the center and the central axis.

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