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 via a separator (13); a bottomed cylindrical outer can (16) that accommodates the electrode body (14); a lower insulating plate (19) that is arranged between the electrode body (14) and the bottom portion (35) of the outer can (16) and has a through-hole (41); and a negative electrode lead (21) that has one end joined to the negative electrode (12) and the other end joined to the bottom portion (35). An opposing portion (61) of the negative electrode lead (21) that faces the bottom portion (35) is accommodated in the through-hole (41) when viewed from the axial direction.

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 in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, a bottomed, cylindrical outer can housing the electrode assembly, a sealing member that closes the opening of the outer can, and an insulating plate with a through hole disposed between the bottom of the outer can and the electrode assembly. The positive electrode of the electrode assembly is electrically connected to the bottom surface of the sealing member via a positive electrode lead, and the negative electrode of the electrode assembly is electrically connected to the bottom of the outer can via a negative electrode lead. The negative electrode lead extends from the inner periphery of the electrode body through the through hole in the insulating plate to the bottom of the outer can, then bends to follow the bottom and continues to extend along the bottom. The tip of the negative electrode lead is located between the insulating plate and the bottom, and the portion of the negative electrode lead facing the bottom of the outer can is joined to the bottom.

[0003] JP 2015-156307 A

[0004] In the cylindrical battery, a portion of the opposing portion of the negative electrode lead is interposed between the insulating plate and the bottom of the outer can, which limits the height of the electrode assembly housed in the outer can and hinders efforts to increase capacity. Therefore, an object of the present disclosure is to provide a high-capacity cylindrical battery.

[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, a bottomed cylindrical outer can that houses the electrode assembly, an insulating plate having a through hole that is arranged between the bottom of the outer can and the electrode assembly, and a negative electrode lead having one end joined to the negative electrode and the other end joined to the bottom, wherein the portion of the negative electrode lead that faces the bottom is contained within the through hole when viewed in the axial direction.

[0006] According to the present disclosure, a high-capacity cylindrical battery can be realized.

[0007] 1 is a cross-sectional view in the axial direction of a cylindrical battery according to an embodiment of the present disclosure; FIG. 2 is a perspective view of an electrode body of the cylindrical battery; FIG. 3 is a plan view of a lower insulating plate in the cylindrical battery as viewed from the axial direction; and FIG. 4 is a cross-sectional view in the axial direction of the lower part of a cylindrical battery of a reference example.

[0008] Hereinafter, with reference to the drawings, an embodiment of a cylindrical battery according to the present disclosure will be described in detail. It is anticipated from the beginning that new embodiments can be constructed by appropriately combining the features of the embodiments and variations described below. In the following embodiments, the same components are designated by the same reference numerals in the drawings, and redundant explanations will be omitted. The drawings are 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 of the cylindrical battery 10 is referred to as "top," and the side of the bottom 35 of the outer can 16 in the axial direction is referred to as "bottom."

[0009] In the following description, the technical concept of the present disclosure will be explained using an example in which the cylindrical battery is a lithium-ion secondary battery containing a non-aqueous electrolyte. However, the cylindrical battery of the present disclosure may also be a battery containing an aqueous electrolyte. Furthermore, the cylindrical battery of the present disclosure may be a primary battery or a secondary battery other than a lithium-ion secondary battery. Furthermore, among the components described below, components not recited in the independent claims representing the superordinate concept 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, and Fig. 2 is a perspective view of an electrode assembly 14 of the cylindrical battery 10. As shown in Fig. 1, the cylindrical battery (hereinafter simply referred to as battery) 10 includes an 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 closes the opening of the outer can 16. As shown in Fig. 2, the electrode assembly 14 has a wound structure in which an elongated positive electrode 11 and an elongated negative electrode 12 are wound with two elongated separators 13 interposed therebetween.

[0011] The negative electrode 12 is formed to have dimensions slightly larger than the positive electrode 11 in order to prevent lithium precipitation. That is, the negative electrode 12 is formed to be longer in the longitudinal direction and width direction (short direction) than the positive electrode 11. Furthermore, the two separators 13 are formed to have dimensions at least slightly larger than the positive electrode 11 and are arranged to sandwich the positive electrode 11. The negative electrode 12 may form the winding start end of the electrode assembly 14. However, in general, the separator 13 extends beyond the winding start end of the negative electrode 12, and the winding start end of the separator 13 becomes the winding start end of the electrode assembly 14.

[0012] 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

[0013] 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.).

[0014] The positive electrode 11 has a positive electrode core and positive electrode mixture layers formed on both sides of the positive electrode core. The positive electrode core can be made of a metal foil, such as aluminum or an aluminum alloy, that is stable within the potential range of the positive electrode 11, or a film with such a metal disposed on the surface layer. The positive electrode mixture layer contains a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 can be produced, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, etc., onto the positive electrode core, drying the coating, and then compressing it to form positive electrode mixture layers on both sides of the positive electrode core.

[0015] 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.

[0016] Examples of the conductive agent contained in the positive electrode mixture layer include carbon black such as acetylene black and ketjen black, graphite, carbon nanotubes, and other carbon materials. Examples of the binder contained in the positive electrode mixture layer include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. These resins may be used in combination with cellulose derivatives such as carboxymethyl cellulose (CMC) or its salts, polyethylene oxide (PEO), and the like.

[0017] The negative electrode 12 has a negative electrode core and negative electrode mixture layers formed on both sides of the negative electrode core. The negative electrode core 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 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, drying the coating, and then compressing it to form a negative electrode mixture layer on both sides of the negative electrode core.

[0018] The negative electrode active material generally uses a carbon material that reversibly absorbs and releases lithium ions. Preferred carbon materials are graphites such as natural graphite, such as flake graphite, lump graphite, and amorphous graphite, and artificial graphite, such as lump artificial graphite and graphitized mesophase carbon microbeads. The negative electrode mixture layer may contain a silicon (Si) material as the negative electrode active material. In addition, the negative electrode active material may be a metal other than Si that alloys with lithium, an alloy containing such a metal, or a compound containing such a metal.

[0019] 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, but styrene-butadiene rubber (SBR) or a modified product thereof is preferably used. In addition to SBR or the like, the negative electrode mixture layer may also contain, for example, CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, or the like.

[0020] A porous sheet having ion permeability and insulating properties is used as 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.

[0021] As shown in Figure 1, a positive electrode lead 20 is joined to the positive electrode 11, and a negative electrode lead 21 is joined to the negative electrode 12. The battery 10 has an upper insulating plate 18 above the electrode body 14 and a lower insulating plate 19 below the electrode body 14. The positive electrode lead 20 is led out from the axially upper side of the electrode body 14 and extends toward the sealing body 17 through a through hole in the upper insulating plate 18. The positive electrode lead 20 is connected to the underside of an internal terminal plate 23 of the sealing body 17 by welding or the like. A terminal cap 27 constituting the top plate of the sealing body 17 is electrically connected to the internal terminal plate 23, and the terminal cap 27 serves as a positive electrode terminal.

[0022] The lower insulating plate 19 has a through hole 41 in the center. The negative electrode lead 21 is led out from the radially inner side and axially lower side of the electrode body 14. The negative electrode lead 21 led out from the axially lower side is bent so as to fit along the bottom 35 of the outer can 16, and a facing portion 61 facing the bottom 35 is formed. The facing portion 61 of the negative electrode lead 21 is joined to the bottom 35 by welding or the like, and the outer can 16 serves as a negative electrode terminal.

[0023] As shown in Fig. 2, the positive electrode lead 20 is electrically connected to an intermediate portion, such as the center portion, of the positive electrode core in the winding direction, and the negative electrode lead 21 is electrically connected to the winding start end of the negative electrode core in the winding direction. As shown in Fig. 1, the outermost periphery of the electrode body 14 includes a negative electrode core exposed portion 12a, which contacts the inner circumferential surface of the outer can 16. In this embodiment, both the winding start end and the winding end end of the negative electrode 12 are electrically connected to the outer can 16, thereby shortening the current path of the negative electrode 12 and reducing the internal resistance of the battery 10. The outermost periphery of the electrode body 14 may be formed by a separator 13, and the winding end end of the negative electrode may not contact the outer can.

[0024] The battery 10 further includes a resin gasket 28 disposed between the outer can 16 and the sealing body 17. The sealing body 17 is fixed to the opening of the outer can 16 by crimping via the gasket 28, thereby sealing the internal space of the battery 10. The gasket 28 is sandwiched between the outer can 16 and the sealing body 17 and insulates the sealing body 17 from the outer can 16. The gasket 28 serves as a sealant to maintain airtightness inside the battery and as an insulator to insulate the outer can 16 from the sealing body 17. The outer can 16 has a cylindrical portion 30 and a bottom 35, and the cylindrical portion 30 includes a grooved portion 34 and a shoulder portion 38. The grooved portion 34 can be formed, for example, by spinning a portion of the side surface of the outer can 16 to form an annular recess radially inward. The shoulder portion 38 is formed by bending the upper end of the outer can 16 inward toward the peripheral edge 39 of the sealing body 17 when the sealing body 17 is fixed to the outer can 16 by crimping.

[0025] The sealing body 17 has a structure in which, in order from the electrode body 14 side, an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a terminal cap 27 are stacked. Each member constituting the sealing body 17 has, for example, a disk or ring shape, and each member except for the insulating member 25 is electrically connected to each other. The internal terminal plate 23 has at least one through-hole 23a. The center of the lower valve body 24 is connected to the center of the upper valve body 26. The insulating member 25 is interposed between the peripheral edges of the lower valve body 24 and the upper valve body 26.

[0026] When the battery 10 generates abnormal heat and the internal pressure of the battery 10 rises, the lower valve body 24 deforms and breaks, pushing the upper valve body 26 toward the terminal cap 27, cutting off the current path between the lower valve body 24 and the upper valve body 26. If the internal pressure rises further, the upper valve body 26 breaks and gas is released from the through-hole 27a of the terminal cap 27. This gas release prevents the internal pressure of the battery 10 from rising excessively, which could cause the battery 10 to explode, thereby improving the safety of the battery 10.

[0027] Next, the lower structure of the battery 10 will be described in more detail. Fig. 3 is a plan view of the lower insulating plate 19 in the battery 10 as viewed from the axial direction. The facing portion 61 is a portion of the negative electrode lead 21 that extends along the bottom portion 35. In Fig. 3, the area where the lower insulating plate 19 exists and the area where the facing portion 61 exists are indicated by different diagonal lines, and a cross section of the outer can 16 is also shown.

[0028] 3, the lower insulating plate 19 has a substantially circular outer edge 42. To reliably prevent the positive electrode 11 (see FIGS. 1 and 2) of the electrode body 14 from contacting the bottom 35, it is preferable that the outer diameter of the lower insulating plate 19 be approximately the same as or slightly smaller than the inner diameter of the outer can 16.

[0029] The through hole 41 in the lower insulating plate 19 has an elongated shape with a major axis R1 and a minor axis R2 perpendicular to the major axis R1. The major axis R1 can be defined as the maximum diameter in the direction in which the through hole 41 extends, and the minor axis R2 can be defined as the inner diameter of the through hole 41 along the perpendicular bisector of the major axis R1. The center P of the through hole 41, which is located at the intersection of the major axis R1 and the minor axis R2, substantially coincides with the center of the outer edge 42.

[0030] The facing portion 61 is contained within the through hole 41 when viewed from the axial direction. The facing portion 61 extends along the major axis direction of the through hole 41. In FIG. 3, the innermost peripheral position of the positive electrode 11 (not shown in FIG. 3) in the electrode body 14 is indicated by a solid closed curve C. At least a portion of the edge 41a of the opening of the through hole 41 is located radially inward of the innermost peripheral portion of the positive electrode 11. As shown in FIG. 3, the minor axis R2 of the through hole 41 is smaller than the smallest diameter of the innermost peripheral portion of the positive electrode 11. As shown in FIG. 1, the thickness of the negative electrode lead 21 is smaller than the thickness of the lower insulating plate 19.

[0031] Next, the effects of the battery 10 according to the present disclosure will be described. Fig. 4 is an axial cross-sectional view of the lower part of a cylindrical battery 110 of a reference example. As shown in Fig. 4, in the cylindrical battery 110, the negative electrode 112 of the electrode body 114 is electrically connected to the bottom 35 of the outer can 16 via a negative electrode lead 121. The negative electrode lead 121 extends from the inner periphery of the electrode body 114 through the through-hole 141 in the lower insulating plate 119 to the bottom 35 of the outer can 16, then bends to follow the bottom 35 and continues to extend along the bottom 35.

[0032] The opposing portion 161 of the negative electrode lead 121 that faces the bottom portion 35 is joined to the bottom portion 35. The tip of the opposing portion 161 is located between the lower insulating plate 119 and the bottom portion 35. In the cylindrical battery 110, because the tip of the opposing portion 161 is located between the lower insulating plate 119 and the bottom portion 35, the axial position of the lower surface of the lower insulating plate 119 is limited to above the opposing portion 161, and therefore the height of the space for accommodating the electrode body 14 is reduced.

[0033] In contrast, in the battery 10 of the present disclosure, the facing portion 61 of the negative electrode lead 21 that faces the bottom portion 35 fits within the through-hole 41 when viewed in the axial direction. Therefore, the lower surface of the lower insulating plate 19 can be lowered to a position where it contacts the bottom portion 35, and accordingly, the height of the space accommodating the electrode body 14 can be increased by the thickness of the facing portion 61. This allows the capacity of the battery 10 to be increased.

[0034] Furthermore, at least a portion of the edge 41 a of the opening of the through-hole 41 is located radially inward of the innermost periphery of the positive electrode 11, so that the lower insulating plate 19 suppresses the expansion of the inner periphery of the positive electrode 11 caused by the expansion and contraction of the negative electrode 12 during charging and discharging of the battery 10. This reliably prevents the positive electrode 11 from coming into contact with the negative electrode 12 or the negative electrode lead 21, thereby reliably preventing a short circuit.

[0035] Furthermore, since the through hole 41 has an elongated hole shape, the length of the facing portion 61 can be increased while maintaining the insulating area of ​​the lower insulating plate 19. Therefore, the facing portion 61 can be welded to the bottom portion 35 reliably and easily.

[0036] Because the thickness of the negative electrode lead 21 is smaller than the thickness of the lower insulating plate 19, the facing portion 61 can be disposed between the upper and lower surfaces of the lower insulating plate 19. Therefore, from the viewpoint of increasing the capacity of the battery 10, it is preferable that the thickness of the negative electrode lead 21 is smaller than the thickness of the lower insulating plate 19.

[0037] The present disclosure is not limited to the above-described embodiment and its modifications. Various improvements and modifications are possible within the scope of the claims of the present application and their equivalents. The lower insulating plate 19 has been described as having an elongated through-hole 41 with a center P substantially coinciding with the center of a substantially circular outer edge 42. However, the lower insulating plate may have a through-hole other than an elongated hole, for example, a through-hole having a circular or polygonal cross-sectional shape. Furthermore, the through-hole of the lower insulating plate may have a center spaced apart from the center of the substantially circular outer edge, or may have a shape in which a central axis cannot be defined. Furthermore, the outer edge of the lower insulating plate in a plan view does not have to be substantially circular, and the thickness of the negative electrode lead may be the same as or thicker than the thickness of the insulating plate.

[0038] REFERENCE SIGNS LIST 10 Cylindrical battery, 11 Positive electrode, 12 Negative electrode, 12a Negative electrode core exposed portion, 13 Separator, 14 Electrode body, 16 Outer can, 17 Sealing body, 18 Upper insulating plate, 19 Lower insulating plate, 20 Positive electrode lead, 21 Negative electrode lead, 23 Internal terminal plate, 23a Through hole, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Terminal cap, 27a Through hole, 28 Gasket, 30 Cylindrical portion, 34 Grooved portion, 35 Bottom portion, 38 Shoulder portion, 39 Peripheral edge portion, 41 Through hole in lower insulating plate, 41a Edge of opening, 42 Outer edge of lower insulating plate, 61 Opposing portion, P Center of through hole, R1 R1: Long diameter of through hole, R2: Short diameter of through hole.

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; a cylindrical outer can with a bottom that houses the electrode assembly; an insulating plate having a through hole that is placed between the bottom of the outer can and the electrode assembly; and a negative electrode lead having one end joined to the negative electrode and the other end joined to the bottom, wherein a portion of the negative electrode lead that faces the bottom is contained within the through hole when viewed axially.

2. The cylindrical battery according to claim 1, wherein at least a portion of the edge of the opening of the through-hole is located radially inward of the innermost periphery of the positive electrode.

3. The cylindrical battery according to claim 2, wherein the through-hole has an elongated shape with a major axis and a minor axis substantially perpendicular to the major axis, and the opposing portion extends along the major axis.

4. The cylindrical battery according to any one of claims 1 to 3, wherein the thickness of the negative electrode lead is smaller than the thickness of the insulating plate.

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