Cylindrical battery and method for manufacturing cylindrical battery

Abstract

To provide a cylindrical battery whose resistance is easily reduced and whose mass productivity is easily enhanced.SOLUTION: A cylindrical battery 10 includes: an electrode body 14 in which a positive electrode 11 and a negative electrode 12 are wound with a separator 13 interposed therebetween; a cylindrical outer can 16 with a bottom that houses the electrode body 14; and a current collector plate 60 electrically connected to the negative electrode 12. A cylindrical portion 30 of the outer can 16 has an inner protruding portion 50 that protrudes radially inward toward a bottom plate 68 of the outer can 16 in the axial direction. An outer peripheral surface 60c of the current collecting plate 60 is brought into contact with an inner peripheral surface 50a of the inner protruding portion 50.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to cylindrical batteries and methods for manufacturing cylindrical batteries. [Background technology]

[0002] A conventional cylindrical battery is shown in Figure 4 of Patent Document 1. This cylindrical battery has a plain area on one axial side of the negative electrode of the electrode assembly, where no negative electrode mixture layer is provided. The plain area is then welded to a disk-shaped current collector, and the current collector is welded to the inside bottom of the outer can. In this way, the negative electrode is electrically connected to the outer can, and the outer can serves as the negative electrode terminal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-161837 Summary of the Invention [Problem to be solved by the invention]

[0004] In the cylindrical battery, the uncoated portion of the negative electrode is electrically connected to the outer can via a current collector, resulting in excellent current collection and high discharge capacity. However, the current collector is welded to the outer can to ensure reliable electrical connection, which increases the resistance of the weld. Furthermore, spatter generated when welding the current collector to the outer can can degrade the cylindrical battery, potentially reducing mass productivity.

[0005] Therefore, an object of the present disclosure is to provide a cylindrical battery that can easily reduce resistance and can easily be mass-produced. [Means for solving the problem]

[0006] In order to solve the above problems, the cylindrical battery of the present disclosure comprises an electrode assembly in which a first electrode and a second electrode are wound with a separator interposed therebetween, a bottomed cylindrical outer can that houses the electrode assembly, and a current collector plate electrically connected to the first electrode, wherein the cylindrical portion of the outer can has an inner protrusion that protrudes radially inward on the bottom plate side of the outer can in the axial direction, and the side of the current collector plate contacts the inner protrusion.

[0007] In addition, a manufacturing method for a cylindrical battery according to the present disclosure includes preparing a bottomed cylindrical outer can including a cylindrical portion and a bottom plate, the end of the cylindrical portion facing the bottom plate having an outer protrusion that protrudes radially outward and is thick-walled, joining the first electrode of an electrode body in which a first electrode and a second electrode are wound with a separator interposed therebetween to a current collector plate, placing the current collector plate to which the electrode body is joined at the bottom side of the outer can, and plastically deforming the outer protrusion radially inward to form an inner protrusion that protrudes radially inward at the end of the cylindrical portion facing the bottom plate, and using the inner protrusion to press against the side of the current collector plate, thereby restraining the current collector plate at the bottom side of the outer can. [Effects of the Invention]

[0008] The cylindrical battery according to the present disclosure facilitates reducing resistance and increasing mass productivity. Furthermore, the cylindrical battery manufacturing method according to the present disclosure enables the manufacturing of cylindrical batteries with low internal resistance and high mass productivity. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an axial cross-sectional view of a cylindrical battery according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a perspective view of an electrode body of the cylindrical battery. [Figure 3] FIG. 2 is a plan view of a long negative electrode before being wound, as viewed from one side in the thickness direction. [Figure 4] FIG. 1 is an axial cross-sectional view of a cylindrical battery in the process of being manufactured. [Figure 5] 10 is an enlarged axial cross-sectional view of the periphery of an outer protruding portion of a cylindrical outer can with a bottom in the middle of manufacture. FIG. [Figure 6] FIG. 4 is an axial cross-sectional view of a cylindrical battery according to a second embodiment of the present disclosure. [Figure 7] 6A to 6C are diagrams illustrating a method for manufacturing a cylindrical battery according to a second embodiment. [Figure 8] 6A to 6C are diagrams illustrating a method for manufacturing a cylindrical battery according to a second embodiment. [Figure 9] FIG. 2 is a plan view of the negative electrode of the cylindrical battery of Comparative Example 1. [Figure 10] 1 is a cross-sectional view of a cylindrical battery of Comparative Example 1 taken along its axial direction. [Figure 11] FIG. 10 is a cross-sectional view of a cylindrical battery of Comparative Example 2 taken along the axial direction. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, with reference to the drawings, an embodiment of a cylindrical battery according to the present disclosure will be described in detail. 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. In the following, a non-aqueous electrolyte secondary battery (lithium ion battery) using a non-aqueous electrolyte will be exemplified as the cylindrical batteries 10 and 110 of the embodiment, but the cylindrical battery according to the present disclosure is not limited thereto.

[0011] It is anticipated from the beginning that new embodiments will be constructed by appropriately combining the features of the first and second embodiments and their variations described below. 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, and other dimensions of each component do not necessarily match between different drawings. In this specification, the side of the sealing body 17 in the axial direction (height direction) of the cylindrical battery 10 is referred to as "upper," and the side of the bottom plate 68 of the outer casing 16 in the axial direction is referred to as "lower." Among the components described below, components not recited in the independent claims representing the superordinate concepts are optional and not essential.

[0012] (First embodiment) FIG. 1 is an axial cross-sectional view of a cylindrical battery 10 according to a first embodiment of the present disclosure, and FIG. 2 is a perspective view of an electrode assembly 14 of the cylindrical battery 10. FIG. 3 is a plan view of a long negative electrode 12 before winding, as viewed from one side in the thickness direction. As shown in FIG. 1, the cylindrical 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 closes the opening of the outer can 16. As shown in FIG. 2, the electrode assembly 14 has a wound structure in which a long positive electrode 11 and a long negative electrode 12 are wound with two long separators 13 interposed therebetween.

[0013] The negative electrode 12 constitutes a first electrode, and the positive electrode 11 constitutes a second electrode. 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 than the positive electrode 11 in the longitudinal direction and width direction (short direction). In addition, the two separators 13 are formed to be slightly larger than the positive electrode 11 and are arranged to sandwich the positive electrode 11, for example. 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.

[0014] 2 and 3, the negative electrode 12 has a negative electrode current collector exposed portion 41, where the negative electrode mixture layer 42 is not provided on the negative electrode current collector 40, at the axial lower end from the winding start end to the winding end end of the long negative electrode 12. Therefore, as shown in FIG. 2, the axial lower end of the electrode assembly 14 is formed by the negative electrode current collector exposed portion 41. The negative electrode 12 may form the winding start end of the electrode assembly 14. However, typically, 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.

[0015] The non-aqueous electrolyte 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 mixtures of two or more of these. The non-aqueous solvent may contain a halogen-substituted compound in which at least a portion of the hydrogen atoms of these solvents are substituted with halogen atoms such as fluorine. The non-aqueous electrolyte is not limited to a liquid electrolyte, but may also be a solid electrolyte using a gel polymer or the like. The electrolyte salt is a lithium salt such as LiPF6.

[0016] The positive electrode 11 has a positive electrode current collector and a positive electrode mixture layer formed on both sides of the positive electrode current collector. The positive electrode current collector can be 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 current collector, drying the coating, and then compressing it to form a positive electrode mixture layer on both sides of the positive electrode current collector.

[0017] The positive electrode active material is mainly composed of a lithium-containing metal composite oxide. Examples of metal elements contained in the lithium-containing metal composite oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, and W. An example of a preferred lithium-containing metal composite oxide is a composite oxide containing at least one of Ni, Co, Mn, and Al.

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

[0019] As shown in FIG. 3 , the negative electrode 12 has a negative electrode current collector 40 and a negative electrode mixture layer 42 formed on both sides of the negative electrode current collector 40. The negative electrode current collector 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 its surface. 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 the negative electrode active material and the binder onto the negative electrode current collector 40, drying the coating, and then compressing it to form the negative electrode mixture layer 42 on both sides of the negative electrode current collector 40.

[0020] 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. The negative electrode mixture layer 42 may contain a silicon (Si) material as the negative electrode active material. Furthermore, 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.

[0021] The binder contained in the negative electrode mixture layer 42 may be a fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, or the like, as in the case of the positive electrode 11. Preferably, styrene-butadiene rubber (SBR) or a modified product thereof is used. The negative electrode mixture layer 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.

[0022] 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.

[0023] As shown in FIG. 1 , a positive electrode lead 20 is joined to the positive electrode 11. The cylindrical battery 10 has an insulating plate 18 above the electrode body 14. The positive electrode lead 20 passes through a through-hole in the insulating plate 18 and extends toward the sealing body 17. The positive electrode lead 20 is connected to the underside of the bottom plate 23 of the sealing body 17 by welding or the like. A terminal cap 27 that forms the top plate of the sealing body 17 is electrically connected to the bottom plate 23, and the terminal cap 27 serves as a positive electrode terminal.

[0024] In the example shown in FIG. 1 , the positive electrode lead 20 is electrically connected to an intermediate portion, such as the center portion, of the positive electrode current collector in the winding direction. In the example shown in FIG. 1 , the positive electrode 11 is electrically connected to the terminal cap 27 using only one positive electrode lead 20. However, the positive electrode may be electrically connected to the terminal cap in any configuration. For example, the positive electrode may be electrically connected to the terminal cap using a multi-lead structure. Specifically, one end of each of multiple positive electrode leads may be joined by welding or the like to the exposed positive electrode current collector portion of the positive electrode at intervals along the longitudinal direction of the positive electrode, and the other end of each of the multiple positive electrode leads may be joined to the terminal cap directly or indirectly via a conductive portion. Alternatively, the exposed positive electrode current collector portion may be joined by welding or the like to a conductive current collector plate, and the current collector may be joined to the terminal cap directly or indirectly via a conductive portion. When this configuration is adopted, the current collector plate may be made of a metal such as aluminum or an aluminum alloy.

[0025] The cylindrical battery 10 includes a metal current collector 60 made of nickel, nickel alloy, or the like, axially below the electrode body 14. The current collector 60 has a disk shape, and the negative electrode current collector exposed portion 41 of the electrode body 14 is joined to the upper surface 60a of the current collector 60. Before inserting the electrode body 14 into the outer can 16, the upper surface 60a of the current collector 60 is pressed against the negative electrode current collector exposed portion 41, which constitutes the lower axial end of the electrode body 14, and the lower surface 60b of the current collector 60 is irradiated with laser light.

[0026] In this manner, by pressing the negative electrode current collector exposed portion 41 against the current collector plate 60, the portion 41a of the negative electrode current collector exposed portion 41 that is bent and extends along the upper surface 60a of the current collector plate 60 is laser-welded to the upper surface 60a of the current collector plate 60, thereby joining the negative electrode current collector exposed portion 41 to the current collector plate 60. Note that ultrasonic welding or resistance welding may also be used to join the negative electrode current collector exposed portion 41 to the current collector plate 60.

[0027] The cylindrical portion 30 of the outer can 16 has an inner protrusion 50 that protrudes radially inward on the axial side of the bottom plate 68 of the outer can 16. The inner protrusion 50 is an annular protrusion that protrudes radially inward around the entire circumferential circumference. The outer peripheral surface 60c of the current collector 60 contacts the inner peripheral surface 50a of the inner protrusion 50, and a force is applied radially inward from the inner peripheral surface 50a. The current collector 60 is stationary relative to the inner protrusion 50 due to static friction, and its axial position is determined. The outer can 16 to which the negative electrode current collector exposed portion 41 is electrically connected via the current collector 60 constitutes a negative electrode terminal.

[0028] It is preferable that the outer peripheral surface 60c of the current collector 60 be in contact with the inner peripheral surface 50a of the inward protruding portion 50 over the entire circumference, since this allows the current collector 60 to be securely restrained by the inward protruding portion 50. However, due to tolerances of the current collector 60 and the outer casing 16, or manufacturing errors, the outer peripheral surface 60c of the current collector 60 may not be in contact with the inner peripheral surface 50a of the inward protruding portion 50 over part of the circumferential direction. What is important is that the current collector 60 remains stationary relative to the inward protruding portion 50 due to static friction, and the axial position of the current collector 60 is determined.

[0029] The cylindrical battery 10 further includes a resin gasket 28 disposed between the exterior can 16 and the sealing body 17. The sealing body 17 is fixed to the opening of the exterior can 16 by crimping via the gasket 28. This seals the internal space of the cylindrical battery 10. The gasket 28 is sandwiched between the exterior can 16 and the sealing body 17, and insulates the sealing body 17 from the exterior can 16. The gasket 28 serves as a sealant to maintain airtightness inside the battery and as an insulator to insulate the exterior can 16 and the sealing body 17.

[0030] The outer can 16 houses the electrode assembly 14 and the non-aqueous electrolyte, and has a shoulder 38, a grooved portion 34, a cylindrical portion 30, and a bottom plate 68. The grooved portion 34 can be formed, for example, by spinning a portion of the side surface of the outer can 16 radially inward to form an annular recess radially inward. The shoulder 38 is formed by bending the upper end of the outer can 16 inward toward the peripheral edge 45 of the sealing body 17 when the sealing body 17 is crimped to the outer can 16.

[0031] The sealing body 17 has a structure in which, in order from the electrode body 14 side, a bottom 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 one another. The bottom plate 23 has at least one through-hole 23a. The lower valve body 24 and the upper valve body 26 are connected at their respective centers, with the insulating member 25 interposed between their respective peripheral edges.

[0032] If the cylindrical battery 10 generates abnormal heat and the internal pressure of the cylindrical battery 10 rises, the lower valve body 24 will deform and push the upper valve body 26 toward the terminal cap 27, causing it to break, 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 will break, causing gas to be released from the through-hole 27a in the terminal cap 27. This gas release prevents the cylindrical battery 10 from exploding due to an excessive increase in internal pressure, thereby improving the safety of the cylindrical battery 10.

[0033] Next, a method for manufacturing the cylindrical battery 10 will be described. First, referring to FIG. 7, a bottomed, cylindrical outer can 16' is prepared. The outer can 16' includes a cylindrical portion 30' and a bottom plate 68'. The end of the cylindrical portion 30' on the bottom plate 68' side has an outer protrusion 70 that protrudes radially outward, making the outer can 16' thicker. In this embodiment, the outer protrusion 70 protrudes radially outward along the entire circumferential direction, forming an annular structure. This outer can 16' is before the spinning or crimping process described above is performed, and does not have a shoulder portion 38 or a grooved portion 34.

[0034] Next, referring to FIG. 1, the negative electrode 12 of the electrode assembly 14, in which the positive electrode 11 and the negative electrode 12 are wound with the separator 13 interposed therebetween, is joined to the current collector plate 60 by the method described above. Next, the current collector plate 60 to which the electrode assembly 14 is joined is placed on the bottom side of an outer can 16′. After that, the spinning and crimping described above are performed to produce a battery 10′ equipped with an outer can 16″, which differs from the battery 10 (see FIG. 1) in that it has an outer protrusion 70 instead of the inner protrusion 50 (see FIG. 1), as shown in FIG.

[0035] Thereafter, drawing is performed so that the outer diameter of the outer protrusion 70 becomes substantially the same as the outer diameter of the cylindrical portion 30''a of the tubular portion 30'' that does not have the outer protrusion 70. This drawing is performed by moving a drawing unit 81 of a drawing device 80 relative to the tubular portion 30 in the axial direction indicated by arrow A. The drawing unit 81 is an annular member and has a cylindrical inner circumferential surface 81a. The inner diameter of the cylindrical inner circumferential surface 81a is substantially the same as the outer diameter of the cylindrical portion 30''a. For this reason, by performing the drawing process, the outer protrusion 70 is plastically deformed radially inward, thereby eliminating the outer protrusion 70 and forming an inner protrusion 50 that protrudes radially inward at the end of the tubular portion 30 (see FIG. 1) on the bottom plate 68 (see FIG. 1) side.

[0036] Furthermore, referring to FIG. 5 , which is an enlarged axial cross-sectional view of the area around the outward protruding portion 70 in the bottomed cylindrical outer can 16″, the inner circumferential surface of the outward protruding portion 70 and the inner circumferential surface of the cylindrical portion 30″a are included in the same cylindrical inner circumferential surface 85. In addition, 2×(t2−t1), which is twice the value obtained by subtracting the radial thickness t1 of the cylindrical portion 30″a from the radial thickness t2 of the outward protruding portion 70, is larger than the value obtained by subtracting the outer diameter of the current collector plate 60 before bonding the negative electrode current collector exposed portion 41 from the inner diameter of the cylindrical inner circumferential surface 85. Therefore, the inward protruding portion 50 can reliably press the outer circumferential surface 60c of the current collector plate 60 (this outer circumferential surface 60c is an example of a side surface of the current collector plate), reliably confining the current collector plate 60 to the bottom side inside the outer can 16, and the battery 10 shown in FIG. 1 can be manufactured. The current collector plate 60 is not joined to the outer can 16 by welding or the like, and is not integral with the outer can 16. The current collector plate 60 is restrained by static friction force to the outer can 16.

[0037] As described above, the cylindrical battery 10 includes an electrode assembly 14 in which the positive electrode 11 and negative electrode 12 are wound with the separator 13 interposed therebetween, a bottomed cylindrical outer can 16 that houses the electrode assembly 14, and a current collector plate 60 electrically connected to the negative electrode 12. The cylindrical portion 30 of the outer can 16 has an inward protruding portion 50 that protrudes radially inward on the axial side of the bottom plate 68 of the outer can 16, and the outer peripheral surface 60c of the current collector plate 60 contacts the inner peripheral surface 50a of the inward protruding portion 50.

[0038] According to the present disclosure, the current collector 60 can be fixed to the outer can 16 by static friction, so there is no need to weld the current collector 60 to the outer can 16. This eliminates the need for a welded joint, which would otherwise be created when welding the current collector to the outer can and would have high resistance, and as a result, the internal resistance of the battery 10 can be reduced.

[0039] Furthermore, no spatter is generated when the current collector plate 60 is fixed to the outer can 16, and the spatter does not deteriorate the battery 10. This allows the quality of the battery 10 to be improved, the yield rate of the battery 10 to be increased, and the mass productivity of the battery 10 to be improved.

[0040] Furthermore, the current collector plate 60 can be fixed to the outer can 16 simply by plastically deforming the outer can 16'' without using any large-scale welding equipment.

[0041] Furthermore, the inner protrusion 50 may be an annular protrusion that protrudes radially inward over the entire circumferential circumference.

[0042] According to this configuration, the inner peripheral surface of the inward protruding portion 50 can restrain a wide area in the circumferential direction on the side surface of the current collector plate 60, and the current collector plate 60 can be fixed to the outer casing 16 more reliably.

[0043] (Second embodiment) 6 is an axial cross-sectional view of a cylindrical battery 110 according to a second embodiment of the present disclosure. The battery 110 of the second embodiment differs from the cylindrical battery 10 of the first embodiment only in that the disk-shaped current collector plate 160 has a bent portion 161. In the second embodiment, the same components as in the first embodiment are assigned the same reference numerals as in the first embodiment, and descriptions thereof will be omitted. Furthermore, descriptions of the same effects and modifications as in the first embodiment will be omitted in the second embodiment.

[0044] 6, a first portion 165 located radially outward of the bent portion 161 of the current collector plate 160 is shown with hatching that is different from that of a second portion 166 other than the bent portion 161 of the current collector plate 160. The first portion 165 coincides with the annular outer edge of the current collector plate 160.

[0045] The battery 110 can be fabricated, for example, by the following method. Specifically, as shown in Fig. 7, a current collector plate 160' before being joined to the negative electrode current collector exposed portion 41 has a bent portion 170 in which at least a part of the outer edge is bent toward a first side in the thickness direction. The current collector plate 160' has an outer diameter smaller than the inner diameter of the inner peripheral surface of the cylindrical outer can 16' with a bottom.

[0046] After joining the negative current collector exposed portion 41 of the electrode assembly 14 to the current collector 160' in the same manner as in the first embodiment, the current collector 160' and the electrode assembly 14 are housed in the outer can 16' so that the tip of the bent portion 170 of the current collector 160' contacts the inner surface of the bottom plate 68' of the outer can 16'. In this state, the bent portion 170 extends from the radially outer end of the central portion 175 of the current collector 160' excluding the bent portion 170, radially outward from the outer can 16' and toward the bottom plate 68' in the axial direction.

[0047] Thereafter, a force F is applied to the electrode body 14 from the upper axial side to the lower axial side. As shown in FIG. 7 , the positive electrode lead 20 may be joined to the positive electrode 11 before the current collector plate 160′ is housed in the outer can 16′, and an insulating plate 18 may be placed on the side of the electrode body 14 opposite the current collector plate 160′ in the axial direction, before the electrode body 14 is housed in the outer can 16′. Then, a downward axial force F may be applied to the upper surface 18a of the insulating plate 18. In this way, a downward axial force may be indirectly applied to the electrode body 14 via the insulating plate 18.

[0048] By applying an axial downward force to the electrode body 14, an axial force is applied to the center portion 175 of the current collector plate 160′ toward the bottom plate 68′, and as shown in FIG. 8, the bent portion 170 is plastically deformed so that the bent portion 170 extends in a substantially radial direction, thereby producing the current collector plate 160 described above. This plastic deformation creates a bent portion 161 in the current collector plate 160. The bent portion 161 is easily identified because it is slightly deformed compared to the other portions. Thereafter, the outer protrusion 70 is plastically deformed into the inner protrusion 50 using the same method as in the first embodiment, thereby producing the battery 110 shown in FIG. 6.

[0049] According to the second embodiment, the current collector 160' can be accommodated in the outer can 16' while the outer diameter of the current collector 160' is small, so the current collector 160' can be accommodated in the outer can 16' smoothly and easily. Furthermore, by plastically deforming the current collector 160' after accommodating the current collector 160' in the outer can 16', the outer diameter of the current collector 160 after plastic deformation can be made closer to the inner diameter of the inner circumferential surface of the outer can 16', and the radial gap between the inner circumferential surface of the outer can 16' and the outer circumferential surface of the current collector 160 can be reduced. Therefore, the inward protrusions 50 formed by plastically deforming the outer protrusions 70 can apply a large radially inward force to the current collector 160, so that the current collector 160 can be reliably fixed to the inward protrusions 50.

[0050] (Internal resistance confirmation test) The inventors of the present application fabricated cylindrical batteries of Comparative Examples 1 and 2 and cylindrical batteries of Examples 1 and 2, and measured the 0.2 C discharge capacity of each cylindrical battery at 25°C and the alternating current (AC) internal resistance (1 kHz) immediately after fabrication, as well as the AC internal resistance (1 kHz) after a storage test at 4.2 V, 60°C, and 20 days.

[0051] <Battery of Comparative Example 1> A negative electrode 212 shown in a plan view in FIG. 9 was used. Specifically, a negative electrode current collector exposed portion 241, where a negative electrode mixture layer 242 was not provided, was formed at the end of the winding end of the negative electrode current collector 240 of the negative electrode 212 in the longitudinal direction. A negative electrode lead 221 was then joined to this negative electrode current collector exposed portion 241. The negative electrode 212 was wound together with a positive electrode 11 and two separators 13 to produce an electrode assembly 214. The electrode assembly 14 was inserted into a bottomed cylindrical outer can 216, and the negative electrode lead 221 was welded to the can bottom, and the positive electrode lead 20 was welded to the sealing body 17. After the electrolyte was poured, the can opening was crimped via a gasket 28 to produce a cylindrical battery 210 having an outer diameter of 18 mm, a height of 65 mm, and a capacity of 2000 mAh, the axial cross section of which is shown in FIG. 10. Battery 210 differs from battery 10 shown in FIG. 1 in that it uses a negative electrode lead 221, that separator 13 forms the lower end of electrode body 214, that it uses a cylindrical outer can 216 with a bottom that has a cylindrical portion 230 that does not have an inward protrusion, and that an insulating plate 19 is disposed between electrode body 214 and bottom plate 268 of outer can 216; otherwise, battery 210 is identical in configuration to battery 10 shown in FIG. 1.

[0052] <Battery of Comparative Example 2> A cylindrical battery 310, the axial cross section of which is shown in Fig. 11, was used as the cylindrical battery of Comparative Example 2. Specifically, in comparison with battery 10 shown in Fig. 1, cylindrical battery 310 differs from battery 10 shown in Fig. 1 only in that a bottomed cylindrical outer can 216 in which the cylindrical portion 230 does not have an inward protrusion was used instead of bottomed cylindrical outer can 16, but other configurations were the same as battery 10 shown in Fig. 1. Cylindrical battery 310 had an outer diameter of 18 mm, a height of 65 mm, and a capacity of 2000 mAh.

[0053] <Battery of Example 1> The cylindrical battery 10 of Example 1 was the cylindrical battery 10 of the first embodiment. Briefly, the structure was as follows: a current collector 60 was welded to the exposed portion 41 of the negative electrode current collector. A bottomed, cylindrical outer can 16′ with a large outer diameter at the bottom and a constant inner diameter was prepared, and the electrode assembly 14 was inserted so that the current collector 60 contacted the can bottom. The positive electrode lead 20 was connected to the sealing body 17. After the electrolyte was poured, the sealing body 17 was crimped to the can opening via a gasket 28. The outer can 16′ was then drawn to form an inner protrusion 50 at the bottom of the outer can 16, thereby reducing the inner diameter of the bottom, thereby allowing the current collector 60 to contact the outer can 16 from both the bottom and the side. In this manner, a cylindrical battery 10 with an outer diameter of 18 mm, a height of 65 mm, and a capacity of 2000 mA was fabricated.

[0054] <Battery of Example 2> The cylindrical battery 110 of Example 2 was used as the cylindrical battery 110 of Example 2. Briefly describing the configuration again, a bottomed, cylindrical outer can 16' with an enlarged outer diameter at the bottom and a constant inner diameter, and a Ni current collector 160' with a curved edge were prepared. The current collector 160' was welded to the negative current collector exposed portion 41 so that the curved side faced away from the electrode assembly 14. The electrode assembly 14 was then inserted into the outer can 16'. The electrode assembly 14 was pressed from above to deform the current collector 160' into a flat current collector 160. The positive electrode lead 20 was connected to the sealing member 17. After the electrolyte was poured into the can opening, the sealing member 17 was crimped via a gasket 28. Thereafter, the outer can 16' was subjected to drawing, and an inner protrusion 50 was formed on the bottom side of the outer can 16 to reduce the inner diameter of the bottom side, thereby bringing the current collector plate 160 into contact with the outer can 16 from not only the bottom but also the side. In this way, a cylindrical battery 110 with an outer diameter of 18 mm, a height of 65 mm, and a capacity of 2000 mA was produced.

[0055] [Test Results] The test results are shown in Table 1 below. [Table 1]

[0056] According to the test results, the batteries of Comparative Examples 1 and 2 and Examples 1 and 2 all achieved approximately the same discharge capacity. Furthermore, with regard to the initial AC internal resistance, the initial AC internal resistance of the battery of Comparative Example 2 was 7.5 mΩ lower than that of the battery of Comparative Example 1, and the initial AC internal resistance of the batteries of Examples 1 and 2 was 8 mΩ lower than that of the battery of Comparative Example 1. The battery of Comparative Example 1 collects current via the negative electrode lead 221 joined to the end of the winding end of the negative electrode 212. Therefore, it is believed that the resistance of the battery of Comparative Example 1 is high due to, for example, the longer current collection path for the charge passing through the winding start side of the negative electrode 212.

[0057] After the storage test, the resistance of the battery of Comparative Example 1 increased by only 2 mΩ compared to the initial value, whereas the resistance of the battery of Comparative Example 2 increased by 5 mΩ compared to the initial value. This is thought to be because gas was generated inside the cell during the storage test, increasing the internal pressure and causing the bottom of the can to swell, thereby reducing the contact area between the can bottom and the current collector plate.

[0058] On the other hand, in the battery of Example 1, the resistance increased by only 3 mΩ compared to the initial value, and the increase in resistance was suppressed compared to Comparative Example 2. Furthermore, in the battery of Example 2, the resistance increased by only 2 mΩ compared to the initial value, and the same results as those of the battery of Comparative Example 1 in which the negative electrode lead 221 was welded to the bottom of the can were obtained.

[0059] The reason for the reduced increase in internal resistance of the batteries in Examples 1 and 2 after the storage test compared to the increase in internal resistance of the battery in Comparative Example 2 is believed to be that the contact area between the current collectors 60 and 160 and the outer can 16 increased by the amount of contact area between their side surfaces. Furthermore, while the battery in Comparative Example 2 had reduced contact with the can bottom due to can bottom bulging, the batteries in Examples 1 and 2 maintained stable contact between the side surfaces of the current collectors and the outer can, thereby maintaining good electrical conductivity. Furthermore, in the battery in Example 2, the outer edge of the current collector 160' was curved before insertion into the outer can 16' and then processed to become flat after insertion into the outer can 16'. This facilitated insertion of the current collector 160' into the outer can 16', improved handling of the current collector 160', and ensured stable contact with the side surfaces of the outer can 16 after drawing the current collector 160.

[0060] (Variation) 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 and their equivalents. For example, in the above-described embodiment, a disk-shaped current collector plate 60, 160 is used, and the outer can 16 has an annular inner protrusion 50. However, the current collector does not have to be disk-shaped. For example, the current collector may have a plate-shaped portion located only in the radial center of the battery and multiple radially extending portions extending radially from the outer edge of the plate-shaped portion and spaced apart circumferentially. The side surface of the current collector may be formed by the leading ends of multiple radially extending portions. Even in this case, the current collector can be fixed to the outer can by contacting the leading ends of each radially extending portion with the radially inner leading ends of the inner protrusions.

[0061] Furthermore, the inner protrusion does not have to be annular, and may be, for example, composed of a plurality of radially extending protrusions that are spaced apart in the circumferential direction and extend radially inward from the cylindrical portion of the outer can. Even in this case, the current collector plate can be fixed to the outer can by bringing the radially inward tip surface of each radially extending protrusion into contact with the side surface of the current collector plate.

[0062] In addition, the case has been described in which the first electrode is the negative electrode 12 and the second electrode is the positive electrode 11, the terminal cap 27 constitutes the positive electrode terminal, and the outer can 16 constitutes the negative electrode terminal. However, the first electrode may be the positive electrode and the second electrode may be the negative electrode, the terminal cap 27 may constitute the negative electrode terminal, and the outer can may constitute the positive electrode terminal. [Explanation of symbols]

[0063] 10,110 cylindrical battery, 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 16 outer can, 17 sealing body, 18 insulating plate, 18a upper surface of insulating plate, 20 positive electrode lead, 23 bottom 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, 30a cylindrical portion, 34 grooved portion, 38 shoulder portion, 40 negative electrode current collector, 41 negative electrode current collector exposed portion, 42 negative electrode mixture layer, 45 peripheral portion, 50 inner protruding portion, 50a inner peripheral surface of inner protruding portion, 60,160 current collector plate, 60a Upper surface of current collecting plate, 60b Lower surface of current collecting plate, 60c Outer peripheral surface of current collecting plate, 68 Bottom plate of outer can, 70 Outer protrusion, 80 Drawing device, 81 Drawing portion, 81a Cylindrical inner peripheral surface of drawing portion, 85 Cylindrical inner peripheral surface, 161 Bent portion, 165 First portion, 166 Second portion, 170 Bent portion, 175 Central portion.

Claims

1. a cylindrical outer can having a bottom, the cylindrical outer can including a cylindrical portion and a bottom plate, the end of the cylindrical portion on the bottom plate side having an outer protruding portion that protrudes radially outward and is thick-walled; a first electrode and a second electrode wound together with a separator interposed therebetween, the first electrode being joined to a current collector plate; The current collector plate to which the electrode body is joined is disposed on the bottom side inside the outer can; a cylindrical battery manufacturing method in which the outer protrusion is plastically deformed radially inward to form an inner protrusion that protrudes radially inward at the end of the cylindrical portion on the bottom plate side, and the inner protrusion presses against the side of the current collector plate, thereby constraining the current collector plate to the bottom side inside the outer can.

2. before the current collector plate is housed in the exterior can, at least a part of an outer edge of the current collector plate has a bent portion bent toward a first side in a thickness direction; the electrode body is joined to a second side in the thickness direction of the electrode body, the current collector plate to which the electrode body is joined is disposed in the outer can such that the first side is located on the bottom plate side; 2. The method for manufacturing a cylindrical battery as described in claim 1, wherein, before plastically deforming the outer protrusion, a force is applied to the electrode body from the side opposite the bottom plate side in the axial direction of the electrode body, thereby applying a force to the second side in the thickness direction of the bent portion and plastically deforming the bent portion.

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