Cylindrical battery

Abstract

A battery (10) is provided with a first negative electrode lead (21a) and a second negative electrode lead (21b) joined to a negative electrode (12). A laminated part (50) in which the first negative electrode lead (21a) and the second negative electrode lead (21b) are laminated in the axial direction in a state in which the first negative electrode lead (21a) is positioned on an electrode body (14) side is formed between the electrode body (14) and a bottom part (31) of an outer can (16). The laminated part (50) is welded to the bottom part (31) of the outer can (16). A first thickness (t1) of the first negative electrode lead (21a) in the laminated part (50) is larger than a second thickness (t2) of the second negative electrode lead (21b) in the laminated part (50).

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 that houses the electrode assembly, and a sealing body that is crimped and fixed to the opening of the outer can via a gasket. The positive electrode and the inner surface of the sealing body are electrically connected via a positive electrode lead. One end of an inner circumferential negative electrode lead is connected to the end of the negative electrode at the start of winding, and one end of an outer circumferential negative electrode lead is connected to the end of the negative electrode at the end of winding.

[0003] The inner and outer negative electrode leads each extend axially toward the bottom of the exterior can and are then bent radially inward. The other end of the inner negative electrode lead and the other end of the outer negative electrode lead are stacked along the bottom surface of the exterior can. The stacked portion of the two negative electrode leads is welded to the bottom of the exterior can by resistance welding. In this cylindrical battery, the inner and outer negative electrode leads are each electrically connected to the bottom of the exterior can, thereby shortening the current collection path and reducing electrical resistance.

[0004] JP 2013-016328 A

[0005] In the cylindrical battery, the stacked portion of the two negative electrode leads must be welded to the bottom of the outer can, and the two negative electrode leads in the stacked portion must also be welded to each other. For example, when the stacked portion of the two negative electrode leads is welded to the bottom of the outer can using a resistance welding machine, stricter welding conditions are required, such as passing a larger current between the stacked portion and the bottom of the outer can via two electrodes (welding rods), compared to when one negative electrode lead is welded to the bottom of the outer can.

[0006] However, the present inventors have found that simply increasing the welding conditions makes it difficult for the negative electrode lead to stick to the electrode (welding rod) of a resistance welding machine, making it difficult to properly weld the laminated portion to the bottom of the outer can. Therefore, an object of the present disclosure is to provide a cylindrical battery in which the laminated portion of two negative electrode leads can be properly and easily welded to the bottom of the outer can.

[0007] In order to solve the above problems, the cylindrical battery of the present disclosure 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 that houses the electrode assembly, a sealing body that is fixed to the opening of the outer can by crimping via a gasket, and a first negative electrode lead and a second negative electrode lead that are joined to the negative electrode, and a laminated portion is formed between the electrode assembly and the bottom of the outer can, in which the first negative electrode lead and the second negative electrode lead are laminated in the axial direction with the first negative electrode lead positioned on the electrode assembly side, and the laminated portion is welded to the bottom of the outer can, and a first thickness of the first negative electrode lead in the laminated portion is greater than a second thickness of the second negative electrode lead in the laminated portion.

[0008] In the cylindrical battery according to the present disclosure, the stacked portion of the two negative electrode leads can be appropriately and easily welded to the bottom of the outer can.

[0009] Fig. 2 is an axial cross-sectional view of a cylindrical battery according to an embodiment of the present disclosure;Fig. 3 is an enlarged cross-sectional view of the periphery of a stacked portion in Fig. 1;Fig. 4 is an enlarged axial cross-sectional view of the periphery of a stacked portion in a battery according to a modified example;

[0010] Hereinafter, an embodiment of a cylindrical battery according to the present disclosure will be described in detail with reference to the drawings. The cylindrical battery according to the present disclosure may be a primary battery or a secondary battery. It may also be a battery using an aqueous electrolyte or a battery using a non-aqueous electrolyte. Hereinafter, a non-aqueous electrolyte secondary battery (lithium ion battery) using a non-aqueous electrolyte will be exemplified as a cylindrical battery 10 according to one embodiment, but the cylindrical battery according to the present disclosure is not limited thereto, and the electrolyte may also be an aqueous electrolyte.

[0011] It is anticipated from the beginning that new embodiments will 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. Furthermore, multiple drawings include schematic diagrams, and the dimensional ratios of the length, width, height, etc. of each component between different drawings do not necessarily match. In this specification, the side of the sealing body 17 in the axial direction (height direction) of the cylindrical battery 10 is referred to as "upper," and the side of the bottom 31 of the outer can 16 in the axial direction is referred to as "lower." Furthermore, among the components described below, components not recited in the independent claims representing the highest concepts are optional components and not essential components.

[0012] FIG. 1 is an axial cross-sectional view of a cylindrical battery 10 according to one embodiment of the present disclosure. As shown in FIG. 1 , the cylindrical battery 10 includes an electrode assembly 14, a cylindrical outer can 16 with a bottom that houses the electrode assembly 14, 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 16 houses a nonaqueous electrolyte together with the electrode assembly 14. The outer can 16 has a shoulder 29 at its upper end that is bent radially inward and extends inward. The outer can 16 has a groove 22 formed in its side wall, and the sealing body 17 is supported by the groove 22 via the gasket 28.

[0013] Gasket 28 is a ring-shaped resin member attached to the outer periphery of sealing body 17, and is interposed between outer can 16 and sealing body 17. Gasket 28 seals the inside of the battery by filling the gap between outer can 16 and sealing body 17, and also insulates sealing body 17 from outer can 16. Gasket 28 is made of, for example, polyolefin.

[0014] 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

[0015] 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.).

[0016] The electrode assembly 14 has a positive electrode 11, a negative electrode 12, and a separator 13, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 interposed therebetween. The positive electrode 11, the negative electrode 12, and the separator 13 are all long, strip-shaped bodies that are spirally wound and alternately stacked in the radial direction of the electrode assembly 14. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium deposition. That is, the negative electrode 12 is formed to be longer in the longitudinal direction and width direction than the positive electrode 11. The separator 13 is formed to be at least slightly larger than the positive electrode 11, and for example, two separators 13 are arranged to sandwich the positive electrode 11.

[0017] The positive electrode 11 has a positive electrode core and a positive electrode mixture layer formed on at least one surface of the positive electrode core. The positive electrode core can be a foil of a metal, 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 preferably contains a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride (PVdF), and is formed on both sides of the positive electrode core. For example, a lithium transition metal composite oxide containing Ni, Co, Mn, Al, etc. is used as the positive electrode active material.

[0018] The negative electrode 12 has a negative electrode core and a negative electrode mixture layer formed on at least one surface of the negative electrode core. The negative electrode core can be made of a foil of a metal, 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 such as styrene-butadiene rubber (SBR) or PVdF, and is preferably formed on both surfaces of the negative electrode core. The negative electrode active material can be, for example, graphite or a silicon-containing compound.

[0019] A positive electrode lead 20 and two negative electrode leads 21 a, 21 b are connected to the electrode body 14. The positive electrode lead 20 electrically connects the positive electrode 11 and the sealing body 17. The first negative electrode lead 21 a is joined to the end of the negative electrode 12 at the start of winding, and electrically connects the end of the winding at the start of winding and the bottom 31 of the outer can 16. The second negative electrode lead 21 b is joined to the end of the negative electrode 12 at the end of winding, and electrically connects the end of the winding at the end of winding and the bottom 31 of the outer can 16.

[0020] The positive electrode lead 20 passes through the opening of the upper insulating plate 18 and extends toward the sealing body 17, and is joined to the lower surface of the sealing body 17. The first negative electrode lead 21a passes through a through-hole in the annular lower insulating plate 19 and is bent toward the hollow portion 14a of the electrode body 14. The second negative electrode lead 21b passes outside the lower insulating plate 19 and is bent so as to overlap the first negative electrode lead 21a. A stacked portion 50 is formed between the electrode body 14 and the bottom 31 of the outer can 16, in which the first negative electrode lead 21a and the second negative electrode lead 21b are stacked in the axial direction, with the first negative electrode lead 21a located on the electrode body 14 side in the axial direction.

[0021] The stacked portion 50 is welded to the bottom 31 of the outer can 16 by a resistance welding machine. More specifically, a welding rod constituting the upper electrode of the resistance welding machine is inserted into the hollow portion 14a of the electrode body 14, and the lower end of the welding rod is placed on the first negative electrode lead 21a located on the upper side of the stacked portion 50. The lower electrode of the resistance welding machine is placed at the center of the bottom 31 of the outer can 16. Then, a voltage is applied between the pair of electrodes to pass a current, thereby welding the contact portion between the first negative electrode lead 21a and the second negative electrode lead 21b and also welding the contact portion between the second negative electrode lead 21b and the bottom 31 of the outer can 16. Joining the negative electrode leads 21a and 21b to both longitudinal ends of the negative electrode 12 shortens the current collection path of the negative electrode 12, thereby reducing the internal resistance of the cylindrical battery 10. The first negative electrode lead 21 a may be joined to an intermediate portion, such as the center portion in the longitudinal direction, of the negative electrode 12 instead of to the end portion on the winding start side of the negative electrode 12 .

[0022] The outer can 16 is generally made of a metal primarily composed of iron, such as nickel-plated iron, but may also be made of a metal primarily composed of aluminum or the like. The outer can 16 has a cylindrical portion 39 and a bottom 31. The cylindrical portion 39 includes an annular grooved portion 22 and an annular shoulder portion 29. The grooved portion 22 is formed by recessing a portion of the cylindrical portion 39 radially inward using a spinning process. The shoulder portion 29 is formed when the upper end portion (the end portion on one side in the axial direction) of the cylindrical portion 39 is bent radially inward and crimped to the peripheral edge portion 33 of the sealing body 17, and extends radially inward at the upper end portion of the cylindrical portion 39.

[0023] The sealing body 17 is clamped by crimping between the shoulder portion 29 and the grooved portion 22 via the gasket 28, and is fixed to the outer can 16. The grooved portion 22 is formed at a position a predetermined length away from the upper end of the outer can 16. The predetermined length is, for example, a length equivalent to 1 to 20% of the axial length of the outer can 16.

[0024] The sealing body 17 has a structure in which a terminal plate 23, a lower valve body 24, an insulating plate 25, an upper valve body 26, and a sealing plate 27 are layered in this order from the electrode body 14 side. Each component constituting the sealing body 17 has, for example, a disk or ring shape, and each component except for the insulating plate 25 is electrically connected to one another. The sealing plate 27 has a convex shape with a radially central portion protruding outward. The convex portion 27a of the sealing plate 27 includes an annular side wall portion and a flat top surface portion surrounded by the side wall portion. One or more air vents 27b are formed in the top surface portion.

[0025] The lower valve body 24, insulating plate 25, and upper valve body 26 constitute a current interruption mechanism. The lower valve body 24 and upper valve body 26 are connected at their respective centers, with the insulating plate 25 interposed between their respective peripheral edges. If an abnormality occurs in the cylindrical battery 10 and the internal pressure rises, the lower valve body 24 deforms and pushes the upper valve body 26 toward the sealing plate 27, causing it to break, thereby interrupting 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, allowing gas to be released through the vent hole 27b in the sealing plate 27.

[0026] In the above description, the sealing body 17 has a laminated structure including two rupture plates (lower valve body 24 and upper valve body 26) and a convex sealing plate 27 that covers the rupture plate. However, the sealing body may be composed of only a rupture plate, or may have a structure in which an internal terminal plate, an insulating plate, and a rupture plate are laminated in this order from the electrode body side. Alternatively, the sealing body may not have a rupture plate, and the bottom of the outer can may have a thin, easily breakable portion that breaks when the battery generates abnormal heat.

[0027] The positive electrode lead 20 is made of a conductive material, such as aluminum. The positive electrode lead 20 is connected to the positive electrode 11, and is preferably joined directly to the positive electrode core by ultrasonic welding or the like, and the joint with the positive electrode core is preferably covered with insulating tape. The positive electrode lead 20 is connected to the underside of the terminal plate 23 by welding, ultrasonic welding or the like, and the sealing plate 27, which is the top plate of the sealing body 17 electrically connected to the terminal plate 23, serves as the positive electrode terminal.

[0028] Each of the negative electrode leads 21 a, 21 b is made of a conductive material, such as nickel, copper, or a clad material formed by bonding a nickel plate and a copper plate. The negative electrode leads 21 a, 21 b are preferably directly joined to the negative electrode core by ultrasonic welding or the like, and the joint with the negative electrode core is preferably covered with insulating tape. The outer can 16 to which the negative electrode leads 21 a, 21 b are joined serves as a negative electrode terminal.

[0029] 2 is an enlarged cross-sectional view of the periphery of the laminated portion 50 in FIG. 1 . As shown in FIG. 2 , the first thickness t1 of the first negative electrode lead 21a in the laminated portion 50 is greater than the second thickness t2 of the second negative electrode lead 21b in the laminated portion 50. When welding the laminated portion 50 of the two negative electrode leads 21a, 21b to the bottom 31 of the outer can 16, stricter welding conditions are required, such as passing a larger current between the laminated portion and the bottom of the outer can via two electrodes (welding rods), compared to when welding a single negative electrode lead to the bottom of the outer can. However, the present inventors have found that simply making the welding conditions stricter makes it difficult to properly weld the laminated portion and the bottom of the outer can, as the negative electrode lead is likely to stick to the electrode (welding rod) of the resistance welding machine.

[0030] In light of this background, as will be described later, the inventors of the present application have found that when the first thickness t1 is greater than the second thickness t2, sticking of the first negative electrode lead 21a to the welding rod is suppressed, thereby increasing the degree of freedom in the welding conditions for welding the stacked portion 50 and the bottom portion 31. For this reason, according to the present embodiment, it is possible to provide a battery 10 in which the stacked portion 50 of the two negative electrode leads 21a, 21b can be appropriately and easily welded to the bottom portion 31 of the outer can 16.

[0031] In order to effectively prevent the negative electrode lead 21a from sticking to the welding rod and to effectively realize appropriate welding between the laminated portion 50 and the bottom portion 31, it is preferable that the first thickness t1 be 0.10 mm or more and 0.20 mm or less, and the second thickness t2 be 0.08 mm or more and 0.15 mm or less. In order to effectively realize appropriate welding between the laminated portion 50 and the bottom portion 31 and to effectively prevent the negative electrode lead 21a from sticking to the welding rod, it is preferable that the first thickness t1 be 1.1 times or more and 1.9 times or less the second thickness t2.

[0032] Example A battery was fabricated in which the thickness of the first negative electrode lead 21a in the laminated portion 30 of the battery 10 of the embodiment was set to 0.10 mm and the thickness of the second negative electrode lead 21b was set to 0.08 mm.

[0033] Comparative Example A battery was fabricated that was different from the battery of the Example only in that the thickness of the first negative electrode lead in the laminated portion and the thickness of the second negative electrode lead in the laminated portion were both 0.10 mm.

[0034] (Welding strength) Ten samples were prepared for each of the examples and comparative examples. After the welded laminated portion and the bottom of the outer can were peeled off from each sample, it was checked whether components of the second negative electrode lead were attached to the bottom. Samples in which components of the second negative electrode lead were attached to the bottom were determined to have sufficient welding strength, and the number of such samples was counted.

[0035] (Stickness to welding rod) When the current value of resistance welding was changed, the presence or absence of sticking of the first negative electrode lead of the laminated portion to the welding rod was investigated at each current value. Each current value is shown in Table 1 as a relative value of 1, 1.15, or 1.25, with the smallest current value being 1. For each current value, 10 samples were prepared for both the example and the comparative example, and the number of samples that did not stick to the welding rod was counted.

[0036]

[0037] As shown in Table 1, when the current value was 1, no sticking to the welding rod occurred in either the Example or the Comparative Example, but it was confirmed that the welding defects reached as high as 40% in the Comparative Example, in which the thicknesses of the two negative electrode leads in the laminated portion were the same. From this, it was confirmed that the Example, in comparison with the Comparative Example, facilitates appropriate welding of the laminated portion of the negative electrode lead to the bottom of the outer can, even when the current value of resistance welding is small.

[0038] When the current value was increased to 1.15, sticking to the welding rod occurred in the comparative example. In contrast, even though the thickness of the laminated portion of the example was thinner than that of the comparative example, sticking to the welding rod did not occur in the example. Furthermore, even when the current value was significantly increased to 1.25, sticking to the welding rod did not occur in the example.

[0039] That is, it was confirmed that, compared with the comparative example, the examples were able to appropriately weld the laminated portion of the negative electrode lead to the bottom of the outer can under a wider range of welding conditions and also suppress sticking of the negative electrode lead to the welding rod. Thus, it was confirmed that, when the first thickness of the first negative electrode lead in the laminated portion was made larger than the second thickness of the second negative electrode lead in the laminated portion, the laminated portion could be appropriately and easily welded to the bottom of the outer can.

[0040] It has been confirmed that when the first thickness of the first negative electrode lead in the laminated portion is 0.10 mm or more and 0.20 mm or less and the second thickness of the second negative electrode lead in the laminated portion is 0.08 mm or more and 0.15 mm or less, appropriate welding can be effectively achieved and sticking to the welding rod can be effectively suppressed. It has also been confirmed that when the first thickness is 1.1 times or more and 1.9 times or less the second thickness, appropriate welding can be effectively achieved and sticking to the welding rod can be effectively suppressed.

[0041] [Modifications] 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. Figure 3 is an enlarged axial cross-sectional view of the periphery of the laminated portion 150 in a battery 110 of a modification. As shown in Figure 3, in the battery 110 of the modification, the first negative electrode lead 121a located on the upper side of the laminated portion 150 is joined to the end of the negative electrode 12 on the winding start side, and the second negative electrode lead 21b located on the lower side of the laminated portion 150 is joined to the end of the negative electrode 12 on the winding start side.

[0042] The thickness t3 of the facing portion 135 of the first negative electrode lead 121a that faces the negative electrode 12 is smaller than the first thickness t1 of the first negative electrode lead 121a in the laminated portion 150. According to the battery 110, the thickness t3 of the facing portion 135 of the first negative electrode lead 121a that is joined to the end portion on the winding start side of the negative electrode 12, which has a large curvature of the electrode body 14, is smaller than the first thickness t1, and therefore the circularity of the electrode body 14 is improved, resulting in good battery characteristics such as capacity retention rate.

[0043] In the above embodiment, the case where the laminated portion 50 is welded to the bottom portion 31 by resistance welding has been described. However, the laminated portion may also be welded to the bottom portion of the outer can by laser welding. Even when laser welding is used in which a laser beam is irradiated axially upward from the can bottom side, if the thickness of the first negative electrode lead on the upper side of the laminated portion is greater than the thickness of the second negative electrode lead on the lower side of the laminated portion, the laminated portion and the bottom portion of the outer can are appropriately welded while suppressing holes in the first negative electrode lead in the laminated portion and spattering above the laminated portion.

[0044] The cylindrical battery of the present disclosure may also have the following configurations. Configuration 1: A cylindrical battery including: an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; a bottomed, tubular outer can that houses the electrode assembly; a sealing body that is crimped and fixed to an opening of the outer can via a gasket; and a first negative electrode lead and a second negative electrode lead that are joined to the negative electrode, wherein a stacked portion is formed between the electrode assembly and a bottom of the outer can, in which the first negative electrode lead and the second negative electrode lead are stacked in the axial direction with the first negative electrode lead positioned on the electrode assembly side, the stacked portion is welded to the bottom of the outer can, and a first thickness of the first negative electrode lead in the stacked portion is greater than a second thickness of the second negative electrode lead in the stacked portion. Configuration 2: The cylindrical battery according to Configuration 1, in which the first thickness is 0.10 mm or more and 0.20 mm or less, and the second thickness is 0.08 mm or more and 0.15 mm or less. Configuration 3: The cylindrical battery according to Configuration 1 or 2, wherein the first thickness is 1.1 to 1.9 times the second thickness. Configuration 4: The cylindrical battery according to any one of Configurations 1 to 3, wherein the first negative electrode lead is joined to an end of the negative electrode at a winding start side, and the second negative electrode lead is joined to an end of the negative electrode at a winding end side. Configuration 5: The cylindrical battery according to Configuration 4, wherein the thickness of a portion of the first negative electrode lead facing the negative electrode is smaller than the first thickness.

[0045] REFERENCE SIGNS LIST 10, 110 battery, 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 14a hollow portion, 16 outer can, 17 sealing body, 18 upper insulating plate, 19 lower insulating plate, 20 positive electrode lead, 21a, 121a first negative electrode lead, 21b second negative electrode lead, 22 grooved portion, 23 terminal plate, 24 lower valve body, 25 insulating plate, 26 upper valve body, 27 sealing plate, 27a convex portion, 27b ventilation hole, 28 gasket, 29 shoulder portion, 30 stacked portion, 31 bottom portion, 33 peripheral portion, 39 cylindrical portion, 50, 150 stacked portion, 135 opposing portion, t1 first thickness, t2 Second thickness, t3: thickness of the opposing portion.

Claims

1. A cylindrical battery comprising: an electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; a bottomed, cylindrical outer can containing the electrode body; a sealing body that is crimped and fixed to the opening of the outer can via a gasket; and a first negative electrode lead and a second negative electrode lead joined to the negative electrode, wherein a laminate portion is formed between the electrode body and a bottom of the outer can, in which the first negative electrode lead and the second negative electrode lead are laminated in the axial direction with the first negative electrode lead positioned on the electrode body side, the laminate portion is welded to the bottom of the outer can, and a first thickness of the first negative electrode lead in the laminate portion is greater than a second thickness of the second negative electrode lead in the laminate portion.

2. The cylindrical battery according to claim 1, wherein the first thickness is 0.10 mm or more and 0.20 mm or less, and the second thickness is 0.08 mm or more and 0.15 mm or less.

3. The cylindrical battery according to claim 1 or 2, wherein the first thickness is 1.1 to 1.9 times the second thickness.

4. A cylindrical battery as described in claim 1 or 2, wherein the first negative electrode lead is joined to the end of the negative electrode at the start of winding, and the second negative electrode lead is joined to the end of the negative electrode at the end of winding.

5. The cylindrical battery according to claim 4, wherein the thickness of the portion of the first negative electrode lead that faces the negative electrode is smaller than the first thickness.

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