Cylindrical secondary battery

Abstract

This battery comprises: an electrode body which is obtained by winding a positive electrode (11) and a negative electrode (12) with a separator being interposed therebetween; an outer package can which houses the electrode body; and a sealing body for sealing an opening part of the outer package can. The sealing body is electrically connected to the positive electrode (11). The end (61) of the negative electrode (12) on the winding start side in the negative electrode longitudinal direction is positioned closer to the winding start side than the end (71) of the positive electrode (11) on the winding start side in the positive electrode longitudinal direction. A part of a first negative electrode portion (12a), which extends in the negative electrode (12) in the negative electrode longitudinal direction from a first edge (62) on the sealing body side in the negative electrode width direction to a negative electrode width directional position (63) that is at 1 / 3 the length in the negative electrode width direction from the first edge (62), protrudes further toward the winding start side in the negative electrode longitudinal direction than a second negative electrode portion (12b), which extends in the negative electrode (12) in the negative electrode longitudinal direction from the negative electrode width directional position (63) to a second edge (64) that is on the opposite side from the first edge (62) in the negative electrode width direction.

Description

Cylindrical secondary battery

[0001] The present disclosure relates to a cylindrical secondary battery.

[0002] A conventional cylindrical secondary battery is described in Patent Document 1. This cylindrical secondary battery includes an electrode assembly in which a long positive electrode and a long negative electrode are wound with a separator interposed therebetween, an outer can housing the electrode assembly, and a sealing body closing an opening on one side in the height direction of the outer can. The positive electrode has a long positive electrode core and a positive electrode mixture layer disposed on the positive electrode core, and the negative electrode has a long negative electrode core and a negative electrode mixture layer disposed on the negative electrode core. In this cylindrical secondary battery, one end of each of multiple positive electrode leads is joined to the positive electrode at intervals in the longitudinal direction of the positive electrode, and the other end of each of the multiple positive electrode leads is joined to the inner surface of the sealing body.

[0003] Japanese Patent Application Laid-Open No. 2003-7346

[0004] The present inventors have discovered the following new problem regarding cylindrical secondary batteries: Specifically, they have found that in cylindrical secondary batteries in which the positive electrode is electrically connected to a sealing member, radial gaps tend to form in the wound electrode assembly on the axial side of the sealing member and on the radially inner side after multiple cycles.

[0005] They also discovered that the occurrence of radial gaps can be suppressed by making the negative electrode protrude a predetermined length or more toward the start of winding beyond the tip of the positive electrode at the start of winding, and using this protruding portion to form a core, thereby increasing the rigidity of the radially inner end of the electrode body.

[0006] However, in this case, it was confirmed that from the center of the electrode body in the height direction to the end opposite the sealing body side in the height direction, the electrodes (positive and negative electrodes) are easily pressed radially inward around the starting end of the positive electrode winding, making the electrodes more likely to deform in that area.

[0007] In other words, there is a trade-off between suppressing the occurrence of radial gaps on the radially inner side of the electrode body and suppressing electrode deformation on the radially inner side of the electrode body. In this context, if the radial gaps or electrode deformation occur, the reliability and battery characteristics of the cylindrical secondary battery will deteriorate. An object of the present disclosure is to provide a cylindrical secondary battery that can easily achieve both suppression of radial gaps and suppression of electrode deformation on the radially inner side of the electrode body.

[0008] In order to solve the above problems, a cylindrical secondary battery according to the present disclosure includes an electrode assembly in which a long positive electrode and a long negative electrode are wound with a separator interposed therebetween, an outer can that houses the electrode assembly, and a sealing body that is fixed to an opening of the outer can by crimping via a gasket, wherein the positive electrode has a long positive electrode core and a positive electrode mixture layer arranged on the positive electrode core, the negative electrode has a long negative electrode core and a negative electrode mixture layer arranged on the negative electrode core, the sealing body is electrically connected to the positive electrode core, and The end of the negative electrode on the winding start side in the longitudinal direction is located closer to the winding start side than the end of the positive electrode on the winding start side in the longitudinal direction of the positive electrode, and a part of a first negative electrode portion of the negative electrode located in a negative electrode longitudinal range from a first end on the sealing body side in the negative electrode width direction to a negative electrode width direction position away by a length that is 1 / 3 of the negative electrode width direction length protrudes closer to the winding start side in the longitudinal direction of the negative electrode than a second negative electrode portion of the negative electrode located in a negative electrode longitudinal range from the negative electrode width direction position to a second end opposite the first end in the negative electrode width direction.

[0009] According to the cylindrical secondary battery according to the present disclosure, it is easy to suppress both the occurrence of radial gaps on the radially inner side of the electrode body and the electrode deformation.

[0010] 1 is a cross-sectional view in the axial direction of a cylindrical secondary battery according to an embodiment of the present disclosure; FIG. 2 is a perspective view showing a portion of an electrode body and a positive electrode lead; FIG. 3 is a plan view showing the inner surface of the wound positive electrode, and FIG. 4 is a plan view illustrating the position and structure of a positive electrode core exposed portion to which the positive electrode lead is joined in the positive electrode; (a) is a plan view of the winding start end of a positive electrode expanded into a long shape as viewed from the positive electrode thickness direction; and (b) is a plan view of the winding start end of a negative electrode expanded into a long shape as viewed from the negative electrode thickness direction. A schematic cross-sectional view in the axial direction of an electrode body illustrating the problems of conventional cylindrical secondary batteries. A schematic cross-sectional view in the radial direction of an electrode body illustrating the problems of conventional cylindrical secondary batteries. (a) is a plan view of the winding start end of a positive electrode expanded into a long shape of a battery of Comparative Example 1 as viewed from the positive electrode thickness direction; and (b) is a plan view of the winding start end of a negative electrode expanded into a long shape of a battery of Comparative Example 1 as viewed from the negative electrode thickness direction. 1A is a plan view of the winding start end of the long-expanded positive electrode of the battery of Comparative Example 4 as viewed from the positive electrode thickness direction, and FIG. 1B is a plan view of the winding start end of the long-expanded negative electrode of the battery of Comparative Example 1 as viewed from the negative electrode thickness direction. FIG. 1A is a plan view of the winding start end of the long-expanded negative electrode 112 of the cylindrical secondary battery of the first modified example as viewed from the negative electrode thickness direction, and FIG. 1B is a plan view of the winding start end of the long-expanded negative electrode of the cylindrical secondary battery of the second modified example as viewed from the negative electrode thickness direction.

[0011] Hereinafter, an embodiment of a cylindrical battery according to the present disclosure will be described with reference to the drawings. Note that the cylindrical secondary battery according to the present disclosure may be a battery using an aqueous electrolyte or a battery using a non-aqueous electrolyte. Hereinafter, a cylindrical lithium-ion secondary battery using a non-aqueous electrolyte will be exemplified as a cylindrical secondary battery 10 according to one embodiment, but the cylindrical secondary battery according to the present disclosure is not limited thereto.

[0012] When multiple embodiments and variations are included below, it is assumed from the beginning that new embodiments can be constructed by appropriately combining their characteristic features. In the following embodiments, the same components are denoted by the same reference numerals in the drawings, and redundant explanations will be omitted. The 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 sealing body 17 side in the axial direction (height direction) of the cylindrical secondary battery 10 is referred to as "upper," and the bottom 68 side of the outer can 16 in the axial direction is referred to as "lower."

[0013] In the following description, when the end of the positive electrode on the winding start side in the longitudinal direction of the positive electrode is referred to, this end refers to the end that exists continuously from one end to the other end in the width direction of the positive electrode on the winding start side in the longitudinal direction of the positive electrode, in a plan view when the winding start side end of the positive electrode, which has been developed into a long shape, is viewed from the thickness direction of the positive electrode; and when the tip of the positive electrode in the longitudinal direction of the positive electrode is referred to, this tip refers to the point on the positive electrode that is located closest to the winding start side in the longitudinal direction of the positive electrode.

[0014] Furthermore, when referring to the end of a negative electrode at the start of winding in the longitudinal direction of the negative electrode, this end refers to the end that exists continuously from one end to the other end in the width direction of the negative electrode on the start of winding in the longitudinal direction of the negative electrode when viewed in a plane when the end portion of the start of winding of the negative electrode, which has been unfolded into a long shape, is viewed from the thickness direction of the negative electrode; and when referring to the tip of a negative electrode in the longitudinal direction of the negative electrode, this tip refers to the point on the negative electrode that is located closest to the start of winding in the longitudinal direction of the negative electrode.

[0015] Among the components described below, those not recited in the independent claims showing the highest concepts are optional components and are not essential components. Furthermore, the present disclosure is not limited to the following embodiments and their modifications, and various improvements and modifications are possible within the scope of the claims of this application and their equivalents.

[0016] Fig. 1 is an axial cross-sectional view of a cylindrical secondary battery 10 according to an embodiment of the present disclosure. As shown in Fig. 1, the cylindrical secondary battery (hereinafter simply referred to as battery) 10 includes a wound electrode assembly 14, a non-aqueous electrolyte (not shown), a cylindrical metal outer can 16 with a bottom that houses the electrode assembly 14 and the non-aqueous electrolyte, and a sealing body 17 that is crimped and fixed to the opening of the outer can 16 via a gasket 28. The outer can may have openings on both upper and lower end portions in the axial direction, and the battery may have a configuration in which the two openings are closed.

[0017] 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

[0018] 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.).

[0019] Fig. 2 is a perspective view showing a portion of the electrode assembly 14 and a positive electrode lead (positive electrode tab) 20. In Fig. 2, the positive electrode mixture layer 32 and the negative electrode mixture layer 42 are indicated by diagonal hatching. As shown in Fig. 2, the electrode assembly 14 has a long positive electrode 11, a long negative electrode 12, and two long separators 13, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound with the 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. 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.

[0020] 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.

[0021] 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. Therefore, the axial lower end of the electrode body 14 is formed by at least a part of the negative electrode substrate exposed portion 41. The negative electrode 12 may form 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.

[0022] 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.

[0023] 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.

[0024] 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, and polyethylene oxide (PEO). To increase capacity, the length of the positive electrode 11 in the longitudinal direction of the positive electrode is preferably 3000 mm or more.

[0025] 3 is a plan view showing the inner winding surface 5 of the positive electrode 11, and is a plan view illustrating the position and structure of the positive electrode substrate exposed portion 35 to which the positive electrode lead 20 is joined in the positive electrode 11. The hatched area in FIG. 3 is the area where the positive electrode mixture layer 32 is disposed. In this embodiment, a case will be described in which the positive electrode lead 20 is joined to the inner winding surface 5 of the positive electrode 11, but the positive electrode lead may also be joined to the outer winding surface of the positive electrode.

[0026] As shown in FIG. 3 , the positive electrode 11 has one or more positive electrode core exposed portions 35 where the positive electrode core 30 is exposed. In this embodiment, the positive electrode 11 has eight positive electrode core exposed portions 35 arranged at intervals in the positive electrode width direction. Positive electrode leads 20 are joined to the positive electrode core exposed portions 35 one by one by ultrasonic welding or the like. The positive electrode mixture layer 32 has a core adjacent portion 32a arranged adjacent to the positive electrode core exposed portion 35 in the positive electrode width direction. Because the positive electrode mixture layer 32 has the core adjacent portion 32a, the arrangement area of ​​the positive electrode mixture layer 32 is increased, resulting in increased capacity. Effectively shortening the positive electrode current path greatly reduces electrical resistance, so it is preferable that the center positions of the eight positive electrode leads 20 in the positive electrode longitudinal direction be arranged at approximately equal intervals in the positive electrode longitudinal direction. The positive electrode substrate exposed portion 35 may be present from one end to the other end of the positive electrode 11 in the positive electrode width direction, and the battery may not have the substrate adjacent portion 32a.

[0027] In order to prevent a short circuit between the positive electrode 11 and the negative electrode 12, it is preferable that at least a portion of the overlapping portion of the positive electrode lead 20 that overlaps the positive electrode core exposed portion 35 in the positive electrode thickness direction be covered with a first insulating tape (not shown), and it is preferable that the insulating tape cover the entire positive electrode core exposed portion 35. Furthermore, in order to prevent a short circuit between the positive electrode 11 and the negative electrode 12, it is preferable that a second insulating tape (headband-shaped insulating tape: not shown) be attached around the entire periphery of the base portion of the extension portion of the positive electrode lead 20 that extends from the positive electrode 11. The first and second insulating tapes are made of an insulating material, and for example, the base material may be made of a polyimide film and the adhesive material may be made of silicone.

[0028] 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.

[0029] 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 silicon (Si) material containing silicon particles, and the mass ratio of Si element in the negative electrode mixture layer 42 is preferably 5% by mass or more. Furthermore, it is preferred that 3.0% by 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.

[0030] 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.

[0031] 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.

[0032] 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 an upper current collector plate 50 and a terminal cap 27. The upper current collector plate 50 is a metal annular plate member and has a through-hole 50a in its radial center.

[0033] The terminal cap 27 is a metal plate-like member without a through hole and is located axially above the sealing body 17. The axially upper end face of the terminal cap 27 is exposed to the outside except for the outer edge, and this exposed portion forms the positive electrode terminal. The sealing body 17 further has a metal plate 51. The metal plate 51 is a metal annular member with a through hole.

[0034] Each positive electrode lead 20 is bent from the positive electrode 11 through the through hole 50a of the upper current collector plate 50 so as to fit along the upper surface of the upper current collector plate 50. The tip of each positive electrode lead 20 is sandwiched between the upper surface of the upper current collector plate 50 and the lower surface of the metal plate 51. Each positive electrode lead 20 is bonded to the upper surface of the upper current collector plate 50. The upper current collector plate 50 and the metal plate 51 are also bonded, and each positive electrode lead 20 and the metal plate 51 are also bonded. These bonds can be achieved, for example, by laser welding the tip of each positive electrode lead 20 sandwiched between the upper current collector plate 50 and the metal plate 51 by irradiating the metal plate 51 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 plate 50 and the metal plate 51, the positive electrode lead 20 can be reliably and easily welded and bonded to the upper current collector plate 50.

[0035] The sealing body 17 has a laminated portion 60 at its outer periphery, in which the terminal cap 27 and the upper current collector plate 50 are laminated. By irradiating the laminated portion 60 with a laser beam from above, the terminal cap 27 and the upper current collector plate 50 are laser-welded and electrically connected. The annular upper surface of the upper current collector plate 50 has an annular recess 53 radially inward from the laminated portion 60. Because the upper surface of the upper current collector plate 50 has the recess 53 recessed downward, a space is provided between the terminal cap 27 and the recess 53 of the upper current collector plate 50. Each positive electrode lead 20 is joined to the upper current collector plate 50 within the recess 53.

[0036] The upper current collector 50 does not have to be joined to the metal plate 51, and the positive electrode lead 20 does not have to be joined to the metal plate 51. Furthermore, the battery does not have to have the metal plate 51. Furthermore, the positive electrode lead 20 may be joined to the lower surface of the upper current collector 50. The current collecting structure electrically connecting the positive electrode 11 to the sealing body 17 has been described as including multiple positive electrode leads 20. However, the current collecting structure electrically connecting the positive electrode to the sealing body may include a structure in which a strip-shaped exposed portion of the positive electrode core that forms the upper end of the electrode body is joined to the current collector plate.

[0037] The battery 10 includes a metal lower current collector plate 52 on the axially lower side of the electrode assembly 14. Referring to FIGS. 1 and 2 , the electrode assembly 14 is pressed against the upper surface of the lower current collector plate 52 so as to tilt the elongated negative electrode substrate exposed portion 41 radially inward. Laser light is irradiated from the lower surface of the lower current collector plate 52, thereby laser-welding and joining the negative electrode substrate exposed portion 41 over a wide area to the upper surface of the lower current collector plate 52. Laser light is also irradiated from the lower side of the outer can 16, thereby laser-welding the bottom 68 of the outer can 16 to the lower current collector plate 52. This electrically connects the negative electrode 12 of the electrode assembly 14 to the outer can 16 via the lower current collector plate 52. By joining the negative electrode substrate exposed portion 41 over a wide area to the upper surface of the lower current collector plate 52, 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.

[0038] The case where the negative electrode substrate exposed portion 41 is electrically connected to the outer can 16 via the lower current collector plate 52 has been described. However, the negative electrode may have a first negative electrode substrate exposed portion where the negative electrode substrate is exposed at the inner end of the winding in the negative electrode longitudinal direction, and a second negative electrode substrate exposed portion where the negative electrode substrate is exposed at the outer end of the winding in the negative electrode longitudinal direction. The second negative electrode substrate exposed portion may have an outermost surface portion included in the outermost surface of the electrode assembly. One end of the negative electrode lead (negative electrode tab) may be joined to the first negative electrode substrate exposed portion, and the other end of the negative electrode lead may be joined to the inner bottom surface of the outer can. The outermost surface portion may also be in contact with the inner circumferential surface of the outer can.

[0039] Alternatively, two negative electrode leads may be joined to the electrode body, with one end of one negative electrode lead electrically connected to the inner end of the negative electrode core in the negative electrode longitudinal direction, and one end of the other negative electrode lead electrically connected to the outer end of the negative electrode core in the negative electrode longitudinal direction. The other end of each negative electrode lead may be electrically connected to the bottom of the outer can. Alternatively, the negative electrode and the outer can may be electrically connected via a single negative electrode lead.

[0040] The outer can 16 has a cylindrical portion 39 and a bottom 68. The cylindrical portion 39 includes an annular grooved portion 22 and an annular shoulder portion 29. The grooved portion 22 is formed by spinning a portion of the cylindrical portion 39 to recess it radially inward around the entire circumferential direction. The sealing body 17 is placed on the grooved portion 22 and is fixed to the opening of the outer can 16 by crimping via a resin gasket 28. The shoulder portion 29 is formed when the upper end of the cylindrical portion 39 is bent radially inward and crimped to the outer edge of the sealing body 17, and extends radially inward at the upper end of the cylindrical portion 39.

[0041] 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 from 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 52 serves as a negative electrode terminal.

[0042] 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.

[0043] 4(a) is a plan view of the winding start side end of the positive electrode 11 developed into a long shape as viewed from the thickness direction of the positive electrode, and FIG. 4(b) is a plan view of the winding start side end of the negative electrode 12 developed into a long shape as viewed from the thickness direction of the negative electrode. In FIG. 4, the positive electrode mixture layer 32 disposed on the positive electrode core 30 and the negative electrode mixture layer 42 disposed on the negative electrode core 40 are indicated by diagonal hatching. As shown in FIG. 4, the winding start side end 61 of the negative electrode 12 in the negative electrode longitudinal direction is located closer to the winding start side than the winding start side end 71 of the positive electrode 11 in the positive electrode longitudinal direction. Furthermore, a portion of the first negative electrode portion 12a of the negative electrode 12 located in the negative electrode longitudinal range from a first end 62 on the sealing body 17 side in the negative electrode width direction to a negative electrode width direction position 63 that is 1 / 3 of the length of the negative electrode width direction, protrudes toward the start of winding in the negative electrode longitudinal direction more than a second negative electrode portion 12b of the negative electrode 12 located in the negative electrode longitudinal range from the negative electrode width direction position 63 to a second end 64 on the opposite side of the first end 62 in the negative electrode width direction.

[0044] Furthermore, in this embodiment, a part of the third negative electrode portion 12c of the negative electrode 12, which is located in the negative electrode longitudinal range from the first end 62 to a second negative electrode widthwise position 65 that is 1 / 5 of the negative electrode widthwise length, also protrudes toward the start of winding in the negative electrode longitudinal direction more than the fourth negative electrode portion 12d of the negative electrode 12, which is located in the negative electrode longitudinal range from the second negative electrode widthwise position 65 to the second end 64.

[0045] Also, the position in the negative electrode width direction of the negative electrode mixture layer 42 closest to the second end 64 in the negative electrode width direction is defined as a negative electrode mixture end position 66 . In this case, when the negative electrode longitudinal length from the first tip 61 a at the start side of winding in the negative electrode longitudinal direction at the first end 62 of the negative electrode 12 to the positive electrode tip 71 a at the closest side of winding in the positive electrode longitudinal direction at the start side of winding in the positive electrode longitudinal direction at the positive electrode 11 is defined as La, the negative electrode longitudinal length from the second tip 61 b ​​at the start side of winding in the negative electrode longitudinal direction of the negative electrode 12 at an intermediate position 67 between the first end 62 and the negative electrode mixture end position 66 in the negative electrode width direction to the positive electrode tip 71 a is defined as Lb, the negative electrode longitudinal length from the third tip 61 c at the start side of winding in the negative electrode longitudinal direction of the negative electrode 12 at the negative electrode mixture end position 66 in the negative electrode width direction to the positive electrode tip 71 a is defined as Lc, and the radial distance from the central axis (central axis of the outer can 16) of the negative electrode inner position that is located closest to the inside in the radial direction on the negative electrode 12 is defined as x (not shown), La > πx, Lb < πx, and Lc < πx hold.

[0046] In this embodiment, La > Lb > Lc. In a plan view of the negative electrode 12 unfolded into a long shape, viewed from the outside in the thickness direction of the negative electrode, the end 61 of the negative electrode 12 at the start of winding in the longitudinal direction of the negative electrode includes an inclined portion 69 that inclines toward the end of winding in the longitudinal direction of the negative electrode from the first end 62 toward the second end 64. In the example shown in FIG. 4( b ), a corner near the first tip 61 a of the negative electrode 12 has a curved portion that is convex toward the start of winding in the longitudinal direction of the negative electrode. The first end 62 is inclined so as to be displaced toward the end of winding in the longitudinal direction of the negative electrode from the lower end of the curved portion to the third tip 61 c toward the lower side in the width direction of the negative electrode.

[0047] Next, the effects of the battery 10 according to the present disclosure will be described. The present inventors have discovered the following problem. Specifically, as shown in FIG. 5 , the inventors have discovered that in a cylindrical secondary battery in which the positive electrode of a wound electrode assembly is electrically connected to a sealing member, after multiple cycles, radial gaps tend to form in the electrode assembly on the sealing member side in the axial direction and on the radially inner side of the electrode assembly. Furthermore, the inventors have discovered that this tendency is more pronounced in batteries in which the exposed portion of the negative electrode substrate is joined to the bottom of the outer can via a current collector plate, and is even more pronounced in batteries in which the positive electrode mixture layer has a substrate adjacent portion that is arranged adjacent in the positive electrode width direction to the exposed portion of the positive electrode substrate to which the positive electrode lead is joined.

[0048] The reason for this is thought to be that when the exposed portion of the negative electrode core is joined to the bottom of the outer can via the current collector plate, the electrode body is more likely to be firmly fixed to the bottom, making it easier for radial gaps to occur on the side opposite the current collector plate in the axial direction, and particularly on the hollow portion side of the electrode body, i.e., the radially inner side.

[0049] Furthermore, when the positive electrode mixture layer has a core adjacent portion, the core adjacent portion is involved in expansion and contraction, while the positive electrode core exposed portion is not involved in expansion and contraction. Therefore, when the electrode body contracts, the location of the positive electrode core exposed portion in the height direction of the electrode body becomes less likely to contract, and it is presumed that this makes it even more likely that radial gaps will occur.

[0050] To address this issue, the inventors discovered that the occurrence of radial gaps can be suppressed by making the negative electrode protrude a predetermined length or more toward the start of winding beyond the tip of the positive electrode at the start of winding, forming a core with this protruding portion, and increasing the rigidity of the radially inner end portion of the electrode body.

[0051] However, in this case, as shown in Figure 6, it was confirmed that the electrodes (positive and negative electrodes) are easily pressed radially inward around the winding start end of the positive electrode from the center of the height direction of the electrode assembly to the end opposite the sealing body side in the height direction, making the electrodes more likely to deform in that area. In other words, it was confirmed that there is a trade-off between suppressing the generation of radial gaps on the radially inner side of the electrode assembly and suppressing electrode deformation on the radially inner side of the electrode assembly. Here, the occurrence of such radial gaps and electrode deformation reduces the reliability and battery characteristics of the cylindrical secondary battery.

[0052] In view of this background, according to the battery 10 of the present disclosure, a portion of the first negative electrode portion 12a protrudes further toward the start of winding in the negative electrode longitudinal direction than the second negative electrode portion 12b, and the length of the negative electrode longitudinal direction protruding from the positive electrode 11 on the axial sealing body 17 side is longer than the length of the negative electrode longitudinal direction protruding from the positive electrode 11 on the opposite axial side.

[0053] Therefore, the protruding portion of the first negative electrode portion 12a, which has a long protruding length from the positive electrode 11, can press the positive electrode 11 radially outward, thereby suppressing the occurrence of radial gaps, and at the same time, the protruding portion of the second negative electrode portion 12b, which has a short protruding length from the positive electrode 11, can reduce the force with which it presses on the electrode portion further inward, thereby suppressing electrode deformation.

[0054] Therefore, according to the battery 10 of the present disclosure, it is possible to achieve the remarkable effect of easily achieving both the suppression of radial gaps on the radially inner side of the electrode body 14 and the suppression of electrode deformation on the radially inner side of the electrode body 14, which are in a trade-off relationship with each other.

[0055] Since this makes it easier to effectively suppress both the occurrence of radial gaps on the radially inner side of the electrode body 14 and the electrode deformation on the radially inner side of the electrode body 14, it is preferable that the end 61 of the negative electrode 12 at the start of winding in the longitudinal direction of the negative electrode includes an inclined portion 69 that inclines toward the end of winding in the longitudinal direction of the negative electrode as it moves from the first end 62 side to the second end 64 side.

[0056] As described above, in the case of a cylindrical secondary battery in which the exposed portion of the negative electrode substrate is joined to the bottom of the outer can via the lower current collector plate, radial gaps are likely to occur unless measures are taken. Therefore, according to battery 10, since negative electrode substrate exposed portion 41 is joined to bottom 68 of outer can 16 via the lower current collector plate 52, the effect of the present disclosure, i.e., the effect of easily realizing both the suppression of radial gaps on the radially inner side of electrode body 14 and the suppression of electrode deformation on the radially inner side of electrode body 14, becomes remarkable.

[0057] It is preferable that La / Lb > 1, La / Lc > 1.5, La > πx, Lb < πx, and Lc < πx be satisfied, as this makes it easier to effectively suppress both the occurrence of radial gaps on the radially inner side of the electrode body and the suppression of electrode deformation on the radially inner side of the electrode body.

[0058] As the weight percentage of silicon in the negative electrode mixture layer 42 increases, the capacity increases. However, the expansion and contraction of the negative electrode mixture layer 42 also increases. Therefore, if no countermeasures are taken, radial gaps tend to occur more significantly, leading to reduced battery reliability. In light of this, the technology disclosed herein can suppress radial gaps and reduce battery reliability. Therefore, even if the weight percentage of silicon in the negative electrode mixture layer 42 is 5% by mass or more, high battery reliability can be maintained, and the capacity of the battery 10 can be significantly increased. From the perspective of increasing capacity, the weight percentage of silicon in the negative electrode mixture layer 42 is preferably 5% by mass or more, more preferably 10% by mass or more, and most preferably 15% by mass or more. On the other hand, the weight percentage of silicon in the negative electrode mixture layer 42 is preferably 50% by mass or less, because this tends to improve the battery reliability of the battery 10.

[0059] The inventors conducted tests to check the presence or absence of radial gaps and the degree of deformation of the electrodes of the electrode assembly for the cylindrical batteries of Comparative Examples 1-4 and Examples 1 and 2. Next, the configurations, test contents, and test results of the cylindrical batteries of Comparative Examples 1-4 and Examples 1 and 2 will be described.

[0060] Comparative Example 1 A battery was fabricated in which the positive electrode and negative electrode structures were different from those of battery 10 described with reference to Figures 1 to 4. Figure 7(a) is a plan view of the winding start end of a positive electrode 311 of the battery of Comparative Example 1, which has been developed into a long shape, as viewed from the positive electrode thickness direction, and Figure 7(b) is a plan view of the winding start end of a negative electrode 312 of the battery of Comparative Example 1, which has been developed into a long shape, as viewed from the negative electrode thickness direction. In Figure 7, the positive electrode mixture layer 332 arranged on the positive electrode core 330 and the negative electrode mixture layer 342 arranged on the negative electrode core 340 are indicated by diagonal hatching.

[0061] 7 , in the battery of Comparative Example 1, the planar shape of the protruding portion 312a of the negative electrode 312 that protrudes from the starting end of the positive electrode 311 toward the winding start side at the end of the electrode assembly toward the winding start side was set to be approximately rectangular. The length L in the negative electrode longitudinal direction from the end 361 of the protruding portion 312a toward the winding start side in the negative electrode longitudinal direction to the tip 371 of the positive electrode 311 toward the winding start side in the positive electrode longitudinal direction was set to 0.5πx.

[0062] Comparative Example 2 A battery was fabricated in comparison with the battery of Comparative Example 1, except that L was πx.

[0063] Comparative Example 3 A battery was fabricated in comparison with the battery of Comparative Example 1, except that L was 2πx.

[0064] Comparative Example 4 A battery was fabricated in which the positive electrode and negative electrode structures were different from those of battery 10 described using FIGS. 1 to 4 and also different from the battery of Comparative Example 1. Fig. 8(a) is a plan view of the winding start end of a positive electrode 411 of the battery of Comparative Example 4, which has been developed into a long shape, as viewed from the thickness direction of the positive electrode, and Fig. 8(b) is a plan view of the winding start end of a negative electrode 412 of the battery of Comparative Example 4, which has been developed into a long shape, as viewed from the thickness direction of the negative electrode. In Fig. 8, a positive electrode mixture layer 432 arranged on a positive electrode core 430 and a negative electrode mixture layer 442 arranged on a negative electrode core 440 are indicated by diagonal hatching.

[0065] 8 , in the battery of Comparative Example 4, the end 461 of the negative electrode 412 on the winding start side in the negative electrode longitudinal direction was inclined so as to displace toward the winding end side in the negative electrode width direction as it moved from a second end 464 on the opposite side from the sealing side in the negative electrode width direction to a first end 462 on the sealing side in the negative electrode width direction. Furthermore, the length La in the negative electrode longitudinal direction from the first end 461a corresponding to the first end 61a of the battery 10 of the embodiment to the positive electrode end 471a on the winding start side in the positive electrode 411 was set to 0.5πx, the length Lb in the negative electrode longitudinal direction from the first end 461b corresponding to the second end 61b of the battery 10 of the embodiment to the positive electrode end 471a was set to 1.0πx, and the length Lc in the negative electrode longitudinal direction from the first end 461c corresponding to the third end 61c of the battery 10 of the embodiment to the positive electrode end 471a was set to 1.5πx.

[0066] Example 1 In the battery 10 including the inclined portion 69 described with reference to FIGS. 1 to 4, La was set to 1.2πx, Lb was set to 0.8πx, and Lc was set to 0.4πx.

[0067] Example 2 In the battery 10 including the inclined portion 69 described with reference to FIGS. 1 to 4, La was set to 1.4πx, Lb was set to 0.8πx, and Lc was set to 0.2πx.

[0068] (Test to confirm the presence or absence of radial gaps) Each of the batteries of Examples 1 and 2 and Comparative Examples 1-4 was subjected to 300 cycles of charge-discharge cycles in a 45°C water-cooled environment, in which after reaching 4.2 V at a constant current of 0.3 C, constant voltage charging was performed at a voltage of 4.2 V until the current value reached 0.02 C, followed by a 20-minute pause, followed by constant current discharging at a constant current of 0.5 C until the battery voltage reached 2.85 V, followed by a 20-minute pause. Thereafter, whether or not radial gaps had occurred was visually determined based on a CT (computed tomography) image of a cross section perpendicular to the height direction of the electrode body at a position vertically downward by 1 / 5 of the height of the electrode body from the top end in the height direction of the electrode body.

[0069] (Electrode Deformation Degree Confirmation Test) For each of the batteries of Examples 1-8 and Comparative Examples 1-4, in a 45°C water-cooled environment, constant voltage charging was performed at a constant current of 0.3 C until the voltage reached 4.2 V, followed by constant voltage charging at a voltage of 4.2 V until the current value reached 0.02 C, and then constant current discharging at a constant current of 0.5 C until the battery voltage reached 2.85 V. This charge-discharge cycle was repeated 300 times. Thereafter, the bending angle of the electrode, which was bent most toward the hollow portion of the electrode body on the inner side of the winding and indicated by θ in FIG. 6, was measured based on a CT image of a cross section perpendicular to the height direction of the electrode body at a position two-thirds of the height of the electrode body downward from the top end of the height direction of the electrode body. A value of θ of 170° or more was rated as good, and a value of θ of less than 170° was rated as bad.

[0070] (Test results)

[0071] The test results are shown in Table 1. As shown in Table 1, in the batteries of Comparative Examples 1 to 3, in which the position of the end of the negative electrode on the winding start side in the negative electrode longitudinal direction does not change in the negative electrode width direction, it was confirmed that in the battery of Comparative Example 1, in which the length in the negative electrode longitudinal direction of the protruding portion of the negative electrode from the tip of the winding start side of the positive electrode in the positive electrode longitudinal direction was short, radial gaps occurred, but the degree of electrode deformation was small. On the other hand, in the batteries of Comparative Examples 2 and 3, in which the length in the negative electrode longitudinal direction of the protruding portion of the negative electrode from the tip of the winding start side of the positive electrode in the positive electrode longitudinal direction was long, no radial gaps occurred, but the degree of electrode deformation was large.

[0072] In addition, in the battery of Comparative Example 4, in which the length of the protruding portion of the negative electrode from the tip of the positive electrode on the winding start side in the positive electrode longitudinal direction increases in a gradient from 0.5πx to 1.5πx as it moves downward in the negative electrode width direction from the first tip to the third tip, radial gaps occurred and the degree of electrode deformation also increased.

[0073] In contrast, in the battery of Example 1, in which the length in the negative electrode longitudinal direction of the protruding portion from the tip of the positive electrode on the winding start side in the positive electrode longitudinal direction of the negative electrode decreases almost monotonically from 1.2πx to 0.4πx as it moves downward in the negative electrode width direction from the first tip to the third tip, no radial gap occurred and the degree of electrode deformation was small.

[0074] Furthermore, the length in the negative electrode longitudinal direction of the protruding portion from the tip of the negative electrode on the winding start side in the positive electrode longitudinal direction decreases almost monotonically from 1.4πx to 0.2πx as it moves downward in the negative electrode width direction from the first tip to the third tip, and even in the battery of Example 2 in which the rate of decrease is large, no radial gaps were generated and the degree of electrode deformation was small.

[0075] The present inventors conducted the above two tests on many prototype batteries in addition to the batteries whose test results are listed in Table 1. They confirmed that, as in the batteries of Examples 1 and 2, if the conditions La / Lb>1, La / Lc>1.5, La>πx, Lb<πx, and Lc<πx are satisfied, the occurrence of radial gaps can be effectively suppressed and the degree of electrode deformation can also be reduced.

[0076] Furthermore, it was confirmed that, by fabricating a cylindrical secondary battery that satisfies the following conditions (1) and (2), radial gaps are less likely to occur and the degree of electrode deformation is easily reduced. (1) The condition that the end of the negative electrode on the winding start side in the negative electrode longitudinal direction is located closer to the winding start side than the end of the positive electrode on the winding start side in the positive electrode longitudinal direction. (2) The condition that a part of a first negative electrode portion located in a range of the negative electrode in the negative electrode longitudinal direction from a first end on the sealing body side in the negative electrode width direction to a position in the negative electrode width direction that is spaced apart by one-third of the length in the negative electrode width direction protrudes toward the winding start side in the negative electrode longitudinal direction more than a second negative electrode portion located in a range of the negative electrode in the negative electrode longitudinal direction from the position in the negative electrode width direction to a second end on the opposite side to the first end in the negative electrode width direction.

[0077] Furthermore, in comparison with the cylindrical secondary battery having the structure described using Figures 1 to 4 and the cylindrical secondary battery having the structure described using Figures 1 to 4, it was confirmed that by manufacturing a cylindrical secondary battery that differs in that the exposed portion of the positive electrode substrate to which the positive electrode lead is joined is present throughout the entire width direction of the positive electrode from one end to the other end in the width direction of the positive electrode, it is possible to effectively suppress both the occurrence of radial gaps and the deformation of the electrode.

[0078] Furthermore, in comparison with cylindrical secondary batteries having the structure described using Figures 1 to 4, it was confirmed that by manufacturing a cylindrical secondary battery in which the current collection structure on the positive electrode side is changed from a multi-lead (multi-tab) current collection structure in which the positive electrode is electrically connected to the sealing body using multiple positive electrode leads to a current collection structure in which the positive electrode is electrically connected to the sealing body using a structure in which the strip-shaped exposed portion of the positive electrode core that constitutes the upper end of the electrode body is joined to the current collecting plate, it is possible to effectively suppress both the occurrence of radial gaps and the deformation of the electrode.

[0079] 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.

[0080] FIG. 9( a) is a plan view of the winding start end of the negative electrode 112 in a cylindrical secondary battery of the first modified example, as viewed from the negative electrode thickness direction. Note that in FIG. 9( a), the negative electrode mixture layer 142 disposed on the negative electrode core 140 is indicated by diagonal hatching. In the cylindrical secondary battery of the first modified example, the winding start end 161 of the negative electrode 112 in the negative electrode longitudinal direction is located closer to the winding start end than the winding start end of the positive electrode (not shown) in the positive electrode longitudinal direction. As shown in FIG. 9( a), the winding start end 161 of the negative electrode 112 in the negative electrode longitudinal direction includes an inclined portion 169 that slopes toward the winding end in the negative electrode longitudinal direction as it moves from the first end 162 on the sealing body side in the negative electrode width direction toward the second end 164. In this modified example, the inclined portion 169 slopes toward the winding end in the negative electrode longitudinal direction as it moves from the vicinity of the first end 162 toward the second end 164. However, the inclined portion may be inclined toward the winding end side in the negative electrode longitudinal direction as it moves from the first end on the sealing body side in the negative electrode width direction to the second end.

[0081] End 161 of negative electrode 112 on the winding start side in the negative electrode longitudinal direction has a straight portion 167 extending in the negative electrode width direction. Straight portion 167 extends from the end of inclined portion 169 on the second end 164 side to the second end 164 in the negative electrode width direction, and in the present modified example, extends from the end of inclined portion 169 on the second end 164 side to second end 164. Note that the straight portion does not need to extend from the end of the inclined portion on the second end side, and may be located closer to the second end in the negative electrode longitudinal direction than the inclined portion.

[0082] 9(b) is a plan view of the winding start end of the negative electrode 212 unfolded into a long shape in the cylindrical secondary battery of the second modified example, as viewed from the negative electrode thickness direction. In FIG. 9(b), the negative electrode mixture layer 242 arranged on the negative electrode core 240 is indicated by diagonal hatching. In the cylindrical secondary battery of the second modified example, the winding start end 261 of the negative electrode 212 in the negative electrode longitudinal direction is also located closer to the winding start side than the winding start end of the positive electrode (not shown) in the positive electrode longitudinal direction.

[0083] As shown in FIG. 9( b ), an end 261 of the negative electrode 212 at the winding start side in the negative electrode longitudinal direction may include a first straight portion 268 extending in the negative electrode width direction, and a second straight portion 269 extending from a first end 262 on the sealing body side in the negative electrode width direction of the negative electrode 212 toward a second end 264 toward the winding end side in the negative electrode longitudinal direction.

[0084] The end 261 of the negative electrode 212 at the winding start side in the negative electrode longitudinal direction may have a stepped shape in a plan view when the winding start side end of the negative electrode 212 is viewed from the negative electrode thickness direction, and the first straight portion 268 and the second straight portion 269 may be alternately repeated two or more times. In the cylindrical secondary battery of the first modification and the cylindrical secondary battery of the second modification, it is easy to suppress the occurrence of radial gaps on the radially inner side of the electrode body, and it is also easy to reduce the degree of electrode deformation.

[0085] The cylindrical secondary battery of the present disclosure may also have the following configurations: Configuration 1: An electrode assembly in which a long positive electrode and a long negative electrode are wound with a separator interposed therebetween, an outer can housing the electrode assembly, and a sealing body that is crimped and fixed to an opening of the outer can via a gasket, wherein the positive electrode has a long positive electrode core and a positive electrode mixture layer disposed on the positive electrode core, the negative electrode has a long negative electrode core and a negative electrode mixture layer disposed on the negative electrode core, and the sealing body is electrically connected to the positive electrode core and is disposed at an end of the negative electrode at a winding start side in the negative electrode longitudinal direction. a portion of a first negative electrode portion of the negative electrode located in a range of the negative electrode longitudinal direction from a first end on the sealing body side in the negative electrode width direction to a negative electrode width direction position spaced a distance of one-third of the negative electrode width direction length in the negative electrode width direction toward the start of winding in the negative electrode longitudinal direction than a second negative electrode portion of the negative electrode located in a range of the negative electrode longitudinal direction from the negative electrode width direction position to a second end on the opposite side in the negative electrode width direction from the first end. Configuration 3: The cylindrical battery according to Configuration 1 or 2, wherein the end of the negative electrode at the start of winding in the longitudinal direction of the negative electrode includes an inclined portion that inclines toward the end of winding in the longitudinal direction of the negative electrode from the first end toward the second end.Configuration 4: The cylindrical battery according to Configuration 3, wherein the end of the negative electrode at the start of winding in the longitudinal direction of the negative electrode has a straight portion extending in the negative electrode width direction, and the straight portion extends from the inclined portion toward the second end in the negative electrode width direction, or the straight portion is located closer to the second end in the negative electrode width direction than the inclined portion.Configuration 5: The cylindrical battery according to any one of Configurations 1 to 3, wherein the end of the negative electrode at the start of winding in the longitudinal direction of the negative electrode includes a first straight portion that extends in the negative electrode width direction and a second straight portion that extends toward the end of winding in the longitudinal direction of the negative electrode from the first end toward the second end.Configuration 6: The cylindrical battery according to Configuration 5, wherein the first straight portion and the second straight portion are alternately repeated two or more times.Configuration 7: The negative electrode has a strip-shaped negative electrode core exposed portion in which the negative electrode core is exposed at an end on the second end side in the negative electrode width direction, and an end of the electrode body opposite to the sealing body side in the axial direction is made up of at least a part of the negative electrode core exposed portion, and includes a current collector plate joined to the negative electrode core exposed portion and the bottom of the outer can, and the position in the negative electrode longitudinal direction of the negative electrode mixture layer closest to the second end in the negative electrode width direction is defined as a negative electrode mixture end position, and La is the length in the negative electrode longitudinal direction from a first tip on the negative electrode longitudinal direction winding start side at the first end of the negative electrode to a positive electrode tip on the positive electrode closest to the positive electrode longitudinal direction winding start side, and the negative electrode width 7. The cylindrical battery according to any one of configurations 1 to 6, wherein Lb is a length in the negative electrode longitudinal direction from a second tip on a winding start side in the negative electrode longitudinal direction of the negative electrode to the tip of the positive electrode at an intermediate position between the first end and the negative electrode mixture end position in the negative electrode width direction, Lc is a length in the negative electrode longitudinal direction from a third tip on a winding start side in the negative electrode longitudinal direction of the negative electrode at the negative electrode mixture end position to the tip of the positive electrode, and x is a radial distance from a central axis of a negative electrode inner position that is located most radially inward on the negative electrode.

[0086] 5 Winding inner surface, 10 Battery, 11 Positive electrode, 12, 112, 212 Negative electrode, 12a First negative electrode portion, 12b Second negative electrode portion, 12c Third negative electrode portion, 12d Fourth negative electrode portion, 13 Separator, 14 Electrode body, 16 Outer can, 17 Sealing body, 18 Insulating plate, 20 Positive electrode lead, 22 Grooved portion, 27 Terminal cap, 28 Gasket, 29 Shoulder portion, 30 Positive electrode core, 32 Positive electrode mixture layer, 32a Core adjacent portion, 35 Positive electrode core exposed portion, 39 Cylindrical portion, 40, 140, 240 Negative electrode core, 41 Negative electrode core exposed portion, 42, 142, 242 Negative electrode mixture layer, 50 Upper current collecting plate, 50a through hole, 51 metal plate, 52 lower current collecting plate, 53 recess, 60 stacked portion, 61, 161, 261 end of negative electrode at winding start side in negative electrode longitudinal direction, 61a first tip, 61b second tip, 61c third tip, 62, 162, 262 first end, 63 position in negative electrode width direction, 64, 164, 264 second end, 65 second position in negative electrode width direction, 66 position of negative electrode mixture end, 67 intermediate position, 68 bottom, 68a easily breakable portion, 69 inclined portion, 71 end of positive electrode at winding start side in positive electrode longitudinal direction, 71a positive electrode tip, 167 straight portion, 169 inclined portion, 268 first straight portion, 269 Second straight section.

Claims

1. An electrode assembly comprising an elongated positive electrode and an elongated negative electrode wound with a separator interposed therebetween; an outer can housing the electrode assembly; and a sealing body fixed to an opening of the outer can by crimping via a gasket, wherein the positive electrode has an elongated positive electrode core and a positive electrode mixture layer arranged on the positive electrode core, the negative electrode has an elongated negative electrode core and a negative electrode mixture layer arranged on the negative electrode core, the sealing body is electrically connected to the positive electrode core, and the end of the negative electrode on the winding start side in the negative electrode longitudinal direction is located closer to the winding start side than the end of the positive electrode on the winding start side in the positive electrode longitudinal direction, a cylindrical battery in which a part of a first negative electrode portion of the negative electrode located in a range in the negative electrode longitudinal direction from a first end of the negative electrode on the sealing body side in the negative electrode width direction to a negative electrode width direction position that is 1 / 3 of the length of the negative electrode width direction away from the first end, protrudes toward the winding start side in the negative electrode longitudinal direction further than a second negative electrode portion of the negative electrode located in a range in the negative electrode longitudinal direction from the negative electrode width direction position to a second end opposite the first end in the negative electrode width direction.

2. A cylindrical battery as described in claim 1, wherein a portion of a third negative electrode portion of the negative electrode located in a negative electrode longitudinal range from the first end to a second negative electrode widthwise position that is 1 / 5 of the negative electrode widthwise length protrudes toward the start of winding in the negative electrode longitudinal direction more than a fourth negative electrode portion of the negative electrode located in a negative electrode longitudinal range from the second negative electrode widthwise position to the second end.

3. A cylindrical battery as described in claim 1, wherein the end of the negative electrode at the start of winding in the longitudinal direction of the negative electrode includes a sloped portion that slopes from the first end side to the end of winding in the longitudinal direction of the negative electrode as it moves from the first end side to the second end side.

4. A cylindrical battery as described in claim 3, wherein the end of the negative electrode at the winding start side in the negative electrode longitudinal direction has a straight portion extending in the negative electrode width direction, and the straight portion extends from the inclined portion toward the second end in the negative electrode width direction, or the straight portion is located closer to the second end in the negative electrode width direction than the inclined portion.

5. A cylindrical battery as described in any one of claims 1 to 3, wherein the end of the negative electrode at the start of winding in the longitudinal direction of the negative electrode includes a first straight section extending in the width direction of the negative electrode, and a second straight section extending from the first end side to the second end side toward the end of winding in the longitudinal direction of the negative electrode.

6. The cylindrical battery according to claim 5, wherein the first straight portion and the second straight portion are alternately repeated two or more times.

7. The negative electrode has a strip-shaped negative electrode core exposed portion where the negative electrode core is exposed at an end on the second end side in the negative electrode width direction, and the end of the electrode body opposite to the sealing body side in the axial direction is made up of at least a part of the negative electrode core exposed portion, and is provided with a current collector plate joined to the negative electrode core exposed portion and the bottom of the exterior can, a negative electrode longitudinal direction length from a first tip on the winding start side in the negative electrode longitudinal direction at the first end of the negative electrode to a positive electrode tip on the winding start side in the positive electrode longitudinal direction at the first end of the negative electrode to a positive electrode tip on the winding start side in the positive electrode longitudinal direction is defined as La; a negative electrode longitudinal direction length from a second tip on the winding start side in the negative electrode longitudinal direction of the negative electrode at an intermediate position between the first end and the negative electrode mixture end position in the negative electrode width direction to the positive electrode tip is defined as Lb; a negative electrode longitudinal direction length from a third tip on the winding start side in the negative electrode longitudinal direction of the negative electrode at the negative electrode mixture end position in the negative electrode width direction to the positive electrode tip is defined as Lc; and a radial distance from a central axis of a negative electrode inner position located most radially inward on the negative electrode, 5. The cylindrical battery according to claim 1, wherein La / Lb>1, La / Lc>1.5, La>πx, Lb<πx, and Lc<πx are satisfied.

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