Cylindrical battery

Abstract

A cylindrical battery (10) comprises: an electrode body (14) in which a positive electrode (11) and a negative electrode (12) are wound with a separator (13) interposed therebetween; an exterior can (16) that accommodates the electrode body (14) and is provided with a shoulder part (29) extending radially inward on one side in the axial direction; and a cap (80) that is provided outside the exterior can (16) and includes an annular shoulder covering part (91) that covers at least a portion of the shoulder part (29). The exterior can (16) and the cap (80) are welded together. The corner of the exterior can (16) is preferably welded to the cap (80).

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 bottomed cylindrical outer can that houses the electrode assembly, a sealing body that closes the opening of the outer can, and a gasket sandwiched between the outer can and the sealing body. The outer can has a cylindrical portion including a groove and a shoulder. The groove is formed by recessing a portion of the cylindrical portion radially inward. The shoulder is formed when the tip of the opening side of the cylindrical portion is bent inward and crimped onto the peripheral edge of the sealing body, and extends radially inward. The sealing body is crimped and fixed to the outer can by being sandwiched between the shoulder and groove via the gasket.

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

[0004] When forming the shoulder of the outer can, the tip of the open end of the cylindrical portion is bent to cause plastic deformation, which generates residual stress in the shoulder due to the bending process, and this residual stress may reduce the durability of the outer can. Therefore, an object of the present disclosure is to provide a cylindrical battery that is likely to have an outer can with good durability and high reliability.

[0005] In order to solve the above problems, the cylindrical battery according to the present disclosure comprises an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, an outer can that houses the electrode assembly and has an annular shoulder portion that extends radially inward on one axial side, and a cap that is disposed on the outside of the outer can and includes an annular shoulder covering portion that covers at least a portion of the shoulder portion, and the outer can and the cap are welded together.

[0006] In the cylindrical battery according to the present disclosure, residual stress in the shoulder of the outer can can be reduced by heat conducted to the shoulder of the outer can through the shoulder covering portion, etc., when the outer can and the cap are welded together, which tends to improve the durability of the outer can and increase its reliability.

[0007] 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 an electrode body and a portion of a positive electrode lead; Fig. 3 is a perspective view of a negative electrode current collector plate as viewed obliquely from below; Fig. 4 is a perspective view of an upper end portion of a cylindrical battery as viewed obliquely from above; Fig. 5 is an enlarged cross-sectional view of the periphery of a shoulder portion in Fig. 1;

[0008] Hereinafter, a cylindrical battery according to the present disclosure will be described in detail with reference to the drawings. Hereinafter, a cylindrical lithium-ion battery including a non-aqueous electrolyte will be described as an example of a cylindrical battery according to the present disclosure. Note that the cylindrical battery according to the present disclosure is not limited to this. The cylindrical battery according to the present disclosure may be a primary battery or a secondary battery. Furthermore, the cylindrical battery according to the present disclosure is not limited to a battery using a non-aqueous electrolyte, and may also be a battery using an aqueous electrolyte.

[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 designated by the same reference numerals in the drawings, and redundant description is 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) 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. 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. 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 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.

[0011] 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

[0012] 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.).

[0013] 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 two separators 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.

[0014] The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to suppress lithium deposition. The negative electrode 12 is formed to be longer in the winding direction and axial direction than the positive electrode 11. The 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.

[0015] The negative electrode 12 has a negative electrode substrate exposed portion 41, where the negative electrode mixture layer 42 is not provided on the negative electrode substrate 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 lower end in the axial direction (height direction) of the electrode body 14 is constituted by the negative electrode substrate 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.

[0016] The positive electrode 11 has a positive electrode core 30 and a positive electrode mixture layer 32 formed on both sides of the positive electrode core 30. The positive electrode core 30 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. The positive electrode mixture layer 32 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. to the positive electrode core 30, drying the coating, and then compressing it to form the positive electrode mixture layer 32 on both sides of the positive electrode core 30.

[0017] 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.

[0018] Examples of the conductive agent contained in the positive electrode mixture layer 32 include carbon black such as acetylene black and ketjen black, and carbon materials such as graphite. Examples of the binder contained in the positive electrode mixture layer 32 include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resin, acrylic resin, and polyolefin resin. These resins may be used in combination with cellulose derivatives such as carboxymethyl cellulose (CMC) or a salt thereof, polyethylene oxide (PEO), and the like.

[0019] The positive electrode 11 has one or more positive electrode core exposed portions (not shown) where the positive electrode core 30 is exposed, and in this embodiment, the positive electrode 11 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. Since the positive electrode current path is effectively shortened, the reduction in electrical resistance is increased, so the center positions of the eight positive electrode leads 20 in the longitudinal direction of the positive electrode are preferably arranged at approximately equal intervals in the longitudinal direction of the positive electrode, and the center-to-center distances in the longitudinal direction of the positive electrode of seven adjacent positive electrode leads 20 are preferably approximately the same.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] As shown in Figure 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 a positive electrode current collector 26 and a terminal cap 27. The positive electrode current collector 26 is a metal annular plate member with a through-hole 26a in its radial center.

[0025] 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.

[0026] Each positive electrode lead 20 is bent from the positive electrode 11 through the through hole 26a of the positive electrode collector plate 26 so as to fit along the upper surface of the positive electrode collector plate 26. The tip of each positive electrode lead 20 is sandwiched between the upper surface of the positive electrode collector plate 26 and the lower surface of the metal plate 25. Each positive electrode lead 20 is bonded to the upper surface of the positive electrode collector plate 26. The positive electrode collector plate 26 and the metal plate 25 are also bonded, and each positive electrode lead 20 and the metal plate 25 are also bonded. These bonds can be achieved, for example, by laser welding the tip of each positive electrode lead 20 sandwiched between the positive electrode collector plate 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 positive electrode collector plate 26 and the metal plate 25, the positive electrode lead 20 can be reliably and easily welded and bonded to the positive electrode collector plate 26.

[0027] The sealing body 17 has a laminated portion 35 on its outer periphery, in which a terminal cap 27 and a positive current collector plate 26 are laminated. By irradiating the laminated portion 35 with a laser beam from above, the terminal cap 27 and the positive current collector plate 26 are laser-welded and electrically connected. The annular upper surface of the positive current collector plate 26 has an annular recess 31 radially inward from the laminated portion 35. Because the upper surface of the positive 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 positive current collector plate 26. Each positive electrode lead 20 is joined to the positive current collector plate 26 within the recess 31. The positive electrode collector plate 26 does not have to be joined to the metal plate 25, and the positive electrode lead 20 does not have to be joined to the metal plate 25. The battery does not have to have a metal plate 25. The positive electrode lead 20 may be joined to the lower surface of the positive current collector plate 26.

[0028] The battery 10 has a metallic negative current collector 19 axially below the electrode body 14. FIG. 3 is a perspective view of the negative current collector 19 as viewed obliquely from below. As shown in FIG. 3, the negative current collector 19 has a flat plate portion 51 in the radial center that is polygonal in plan view. The flat plate portion 51 may have a shape other than a polygon in plan view, such as a circular shape in plan view. The negative current collector 19 has multiple radially extending portions 53 connected to the flat plate portion 51, and in this embodiment, the negative current collector 19 has four radially extending portions 53. The radially extending portions 53 have a columnar shape and extend in the radial direction. It is preferable that the multiple radially extending portions 53 are arranged at equal intervals in the circumferential direction.

[0029] The radially extending portion 53 is connected to the flat portion 51 via a step portion 54, and the bottom surface of the flat portion 51 is located lower than the bottom surface of the radially extending portion 53. This allows the bottom surface of the flat portion 51 to be tightly attached to the inner surface of the bottom portion 68 of the outer can 16 without any gaps when joining the flat portion 51 to the bottom portion 68, making it easier to achieve good joining of the flat 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 upward 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.

[0030] 1 , the negative electrode substrate exposed portion 41 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 range in the radial direction.

[0031] Thereafter, a presser rod (not shown) inserted from above into the hollow portion 14a of the electrode body 14 presses the upper surface of the flat portion 51 against the inner surface of the bottom portion 68 of the outer can 16, and laser light is irradiated from below the outer can 16 to laser-weld the bottom portion 68 to the negative electrode current collector plate 19. As a result, the negative electrode 12 of the electrode body 14 is electrically connected to the outer can 16 via the negative electrode current collector plate 19. By joining the negative electrode core exposed portion 41 over a wide area to the upper surface of the negative electrode current collector plate 19, it is possible to prevent current from flowing a long distance along the longitudinal direction of the elongated negative electrode 12, thereby reducing the electrical resistance of the battery 10.

[0032] 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.

[0033] 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 to maintain airtightness inside the battery and as an insulating material to insulate the outer can 16 and the sealing body 17. A terminal cap 27 electrically connected to the positive electrode lead 20 serves as a positive electrode terminal.

[0034] The battery 10 further includes a metal cap 80, which is an integral annular member, and an annular insulating plate 81 made of an insulating material. The cap 80 is disposed on the exterior of the outer can 16 and includes an annular shoulder covering portion 91 that covers at least a portion of the shoulder portion 29, a tubular portion 92 that extends substantially axially from the outer peripheral end of the shoulder covering portion 91, and a groove placement portion 93 that is disposed within the annular groove 22a defined by the grooved portion 22. In this embodiment, the tubular portion 92 has a cylindrical shape. The shoulder covering portion 91 is bent radially inward from the upper tip of the tubular portion 92 and extends inward. In the example shown in FIG. 1 , the tubular portion 92 extends radially inward and substantially parallel to the radial direction. The tubular portion 92 extends downward from the radially outer end of the shoulder covering portion 91 substantially parallel to the axial direction. The cap 80 extends from the lower end of the tubular portion 92 toward the annular groove 22a. The groove placement portion 93 is disposed within the annular groove 22a. The groove arrangement portion 93 forms the lower tip portion of the cap 80 .

[0035] 4 is a perspective view of the upper end of the battery 10 as viewed obliquely from above. As shown in FIG. 4 , the shoulder covering portion 91 and the cylindrical portion 92 of the cap 80 extend along the outer surface of the outer can 16 from the radially inner tip of the shoulder portion 29 of the outer can 16 to the upper end of the grooved portion 22. The cap 80 is joined to the outer surface of the outer can 16. In this embodiment, as will be described in detail later, the cap 80 is joined to the outer surface of the shoulder portion 29 by laser welding. The cap 80, which is electrically connected to the negative electrode core exposed portion 41 via the negative electrode current collector plate 19 and the outer can 16, serves as the negative electrode terminal.

[0036] When multiple batteries 10 are electrically connected to form a battery module, the tongue (lead) of a first external current collector plate (not shown) is joined to the upper surface of the protrusion 27a of the terminal cap 27, and the tongue (lead) of a second external current collector plate (not shown) is joined to the shoulder covering portion 91 of the cap 80. Because the shoulder covering portion 91 has the shape of an annular plate that expands in the radial direction, the tongue can be easily joined to the shoulder covering portion 91. Note that a battery 10 may be used alone.

[0037] Referring again to FIG. 1 , the insulating plate 81 is interposed between the shoulder covering portion 91 and the sealing body 17 to insulate the cap 80 from the sealing body 17. The gasket 28 may have a protrusion 28a extending radially from between the shoulder portion 29 and the sealing body 17 at its tip end, and the outer peripheral edge 81a on the radially outer side of the insulating plate 81 may be located above the protrusion 28a and in contact with the gasket 28. In this manner, the insulating plate 81 and the gasket 28 can reliably insulate the cap 80 from the sealing body 17. In this embodiment, the insulating plate 81 includes a flange portion 82 and a cylindrical portion 83 that covers the outer peripheral surface of the protrusion 27a of the terminal cap 27. The cylindrical portion 83 is connected to the radially inner end of the flange portion 82.

[0038] 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.

[0039] 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 also 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.

[0040] Furthermore, although the case where the negative electrode substrate exposed portion 41 is electrically connected to the outer can 16 via the negative electrode current collector plate 19 has been described, the battery may not have a negative electrode current collector plate, and the negative electrode may be joined to the bottom of the outer can via one or more negative electrode leads. Furthermore, the case where the positive electrode 11 is electrically connected to the sealing body 17 via one or more positive electrode leads 20 has been described. However, the positive electrode may be electrically connected to the sealing body by joining the positive electrode substrate exposed portion to the positive electrode current collector plate, and the battery may not have a positive electrode lead.

[0041] 5 is an enlarged cross-sectional view of the vicinity of the shoulder portion 29 in FIG. 1 . Note that in FIG. 5 , the black-filled area extending across the cap 80 and the outer can 16 is a weld (melt mark) 70 joining the cap 80 and the outer can 16. Referring to FIG. 5 , when a corner 75 of the outer can 16 is defined as a portion of the outer can 16 located between a first location K1 that axially overlaps with a radial outer peripheral edge 78 of the sealing body 17 on one axial side (axially upper side) and a second location K2 that radially overlaps with a surface (top surface) 71 on one axial side of the peripheral edge of the sealing body 17 on the radially outer side, at least a portion of the corner 75 is welded to the cap 80, and a portion of the weld 70 is provided at the corner 75.

[0042] In other words, the cap 80 and the outer can 16 are joined by an annular weld 70 that is provided to straddle the cap 80 and the corner 75. The cap 80 has an annular recess 88 that is recessed toward the other axial direction in at least a portion of a corner facing portion 87 that axially faces the corner 75. The bottom surface of the recess 88 extends in a direction approximately perpendicular to the axial direction. The annular weld 70 is formed by irradiating the annular recess 88 in the axial direction with a laser beam L1 while scanning it in an annular manner. The irradiation energy of the irradiated laser beam can be, for example, 30 W or more and 80 W or less, and preferably 45 W or more and 70 W or less.

[0043] Next, the effects of the battery 10 of the present disclosure will be described. As described above, in a cylindrical battery, when forming the shoulder of the outer can, the open end of the tubular portion is bent to plastically deform it. This causes residual stress in the shoulder due to the bending process. This residual stress may reduce the durability of the outer can. In contrast, in the battery 10 of the present disclosure, a portion of the weld 70 is provided at the corner 75 of the outer can 16, where strain from plastic deformation is large. Therefore, the residual stress at the corner 75 can be reduced by the heat generated during welding. This makes it easier for the outer can 16 to have good durability and high reliability.

[0044] Furthermore, the cap 80 has a recess 88 recessed axially toward the other side in at least a part of a corner facing portion 87 axially facing the corner 75, and the laser beam L1 is irradiated onto the recess 88, and the laser beam L1 is irradiated onto the thin-walled portion of the cap 80. Therefore, the irradiation energy of the laser beam when forming the welded portion 70 can be reduced, and therefore, even when the laser beam L1 is irradiated, the strength of the outer can 16 is likely to be maintained at a value that allows good sealing performance to be achieved.

[0045] In order to effectively reduce residual stress in the shoulder portion 29 and to improve the durability of the outer can 16, it is preferable that the maximum depth in the thickness direction of the outer can 16 at the welded portion 77 (melting mark on the outer can 16) is equal to or greater than 1 / 10 of the thickness of the outer can 16 at the maximum depth position of the welded portion 77. In addition, in order to easily achieve a melting that easily achieves good sealing of the outer can 16, it is preferable that the maximum depth in the thickness direction of the welded portion 77 of the outer can 16 is equal to or less than 1 / 2 of the thickness of the outer can 16 at the maximum depth position of the welded portion 77. The thickness direction of the outer can 16 can be defined as the extension direction of a straight line that intersects at a tangent line that touches the outer surface of the outer can 16 at a tangent point in an axial cross section of the outer can 16.

[0046] The present disclosure is not limited to the above-described embodiment and its modifications, 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 weld 70 formed by irradiation with laser light L1 is provided so as to straddle the cap 80 and the corner 75. However, the weld between the cap and the outer can may include a first portion located at the corner and a second portion located outside the corner. Alternatively, the weld between the cap and the outer can may not include the portion located at the corner.

[0047] In the above description, the cap 80 includes an annular shoulder covering portion 91, a cylindrical portion 92, and a groove-arranged portion 93. However, the cap may have any shape as long as it has an annular shoulder covering portion that covers at least a portion of the shoulder. For example, the cap may not have a cylindrical portion or a groove-arranged portion. It is sufficient for the cap to have an annular shoulder covering portion that covers at least a portion of the shoulder, and for a portion of the outer can that faces the cap to be welded to the cap. In such a case, heat generated during welding can be conducted to the outer can shoulder via the shoulder covering portion, etc., and the heat can reduce residual stress in the shoulder.

[0048] The above description deals with the case where the laser beam L1 is irradiated in the axial direction toward the recess 88. However, a weld spanning the cap and the corner may also be formed by irradiating the laser beam L2 from a direction tilted radially outward from the axial direction at an inclination angle θ of 35° to 55°, both inclusive, to the entire circumference of the position of the cap facing the corner 75. Alternatively, a weld spanning the cap and the corner may also be formed by irradiating the laser beam L2 from a direction tilted radially outward from the axial direction at an inclination angle θ of 40° to 50°, both inclusive, to the entire circumference of the position of the cap facing the corner 75. Alternatively, a weld spanning the cap and the corner may also be formed by irradiating the laser beam L3 annularly from the radially outward to the cylindrical portion 92 of the cap 80. Note that, regardless of the direction of laser beam irradiation, it is preferable to irradiate the laser beam with the focal point of the laser beam coincident with the outer surface of the outer can. This ensures reliable joining of the cap and the outer can and effectively reduces residual stress in the outer can.

[0049] 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 positive electrode and a negative electrode are wound with a separator interposed therebetween; an outer can that houses the electrode assembly and has an annular shoulder portion extending radially inward on one axial side; and a cap that is disposed on the outside of the outer can and includes an annular shoulder covering portion that covers at least a portion of the shoulder, the outer can and the cap being welded together. Configuration 2: The cylindrical battery according to Configuration 1, in which the shoulder covering portion covers the entire shoulder, the outer can has a tubular portion that includes the shoulder and a grooved portion that is recessed radially inward around the entire circumferential circumference, the cap is an integral annular member that includes a tubular portion that extends from an outer radial end of the shoulder covering portion to approximately the other axial side, and a cap facing portion of the outer can that faces the cap is welded to the cap. Configuration 3: A cylindrical battery according to Configuration 1 or 2, comprising a sealing body that is fixed to the shoulder portion of the outer can by crimping via a gasket, and wherein, when a corner of the outer can is defined as a portion of the outer can located between a first location that axially overlaps on one axial side of the radially outer peripheral edge of the sealing body and a second location that radially overlaps on the radially outer side of one axial side of the axial side of the peripheral edge of the sealing body, at least a portion of the corner is welded to the cap.Configuration 4: A cylindrical battery according to Configuration 3, wherein the cap has a recess that is recessed on the other axial side in the axial direction in at least a portion of a corner-facing portion that axially faces the corner.Configuration 5: A cylindrical battery according to any one of Configurations 1 to 4, wherein the maximum depth in the thickness direction of the outer can at the weld portion of the outer can is 1 / 10 or more of the thickness of the outer can at the position of the maximum depth of the weld portion. Configuration 6: The cylindrical battery according to any one of Configurations 1 to 5, wherein the maximum depth in the thickness direction of the outer can at the welded portion of the outer can is equal to or less than half the thickness of the outer can at the position of the maximum depth of the welded portion.

[0050] 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 Negative electrode current collector, 20 Positive electrode lead, 22 Grooved portion, 22a Annular groove, 25 Metal plate, 26 Positive electrode current collector, 26a Through hole, 27 Terminal cap, 27a Convex portion, 28 Gasket, 28a Protruding portion, 29 Shoulder portion, 30 Positive electrode core, 31 Concave portion, 32 Positive electrode mixture layer, 35 Laminated portion, 39 Cylindrical portion, 40 Negative electrode core, 41 Negative electrode core exposed portion, 42 Negative electrode mixture layer, 51 Flat portion, 53 Radially extending portion, 54 step portion, 56 ridge portion, 57 groove portion, 68 bottom portion, 68a easily breakable portion, 70 welded portion, upper surface of peripheral portion of sealing body, 75 corner portion, 77 welded portion of outer can, 78 outer peripheral edge of sealing body, 80 cap, 81 insulating plate, 81a outer peripheral edge portion, 82 flange portion, 83 tubular portion, 87 portion facing corner portion of cap, 88 recess, 91 shoulder covering portion, 92 tubular portion, 93 groove arrangement portion, K1 first location, K2 second location, L1, L2, L3 laser light, θ tilt angle.

Claims

1. A cylindrical battery comprising: an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; an outer can that houses the electrode assembly and has an annular shoulder portion on one axial side that extends radially inward; and a cap that is disposed on the outside of the outer can and includes an annular shoulder covering portion that covers at least a portion of the shoulder portion, wherein the outer can and the cap are welded together.

2. A cylindrical battery as described in claim 1, wherein the shoulder covering portion covers the entire shoulder portion, the outer can has a cylindrical portion including the shoulder portion and a grooved portion recessed radially inward around the entire circumferential circumference, the cap is a single annular member including a cylindrical portion extending from the radially outer end of the shoulder covering portion to the other side in the approximate axial direction, and a part of the cap facing portion of the outer can that faces the cap is welded to the cap.

3. A cylindrical battery according to claim 1, comprising a sealing body that is fixed to the shoulder of the outer can by crimping via a gasket, and when a corner of the outer can is defined as a portion of the outer can that is located between a first location that overlaps with the outer peripheral edge of the sealing body in the axial direction on one axial side, and a second location that overlaps with one axial side of the peripheral edge of the sealing body in the radial direction on the radially outer side, at least a portion of the corner is welded to the cap.

4. The cylindrical battery according to claim 3, wherein the cap has a recess recessed toward the other side in the axial direction in at least a part of the corner-facing portion axially facing the corner.

5. A cylindrical battery according to any one of claims 1 to 4, wherein the maximum depth in the thickness direction of the outer can at the welded portion of the outer can is at least 1 / 10 of the thickness of the outer can at the maximum depth position of the welded portion.

6. A cylindrical battery according to any one of claims 1 to 4, wherein the maximum depth in the thickness direction of the outer can at the welded portion of the outer can is equal to or less than half the thickness of the outer can at the deepest position of the welded portion.

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