Sealed battery and method for manufacturing sealed battery

Abstract

A battery (10) is provided with: an electrode body (14) in which a positive electrode (11) and a negative electrode (12) are wound via a separator (13); an electrolyte; a bottomed cylindrical outer can (20) that accommodates the electrode body and the electrolyte; a sealing body (21) that closes an opening end (20B) of the outer can (20); and an annular gasket (19) that is located between the outer can (20) and the sealing body (21). The sealing body (21) is crimped and fixed to the opening end (20B) of the outer can (20) via the gasket (19). A laser irradiation unit (22) is formed in a shoulder (20D) that is formed by crimping the opening end (20B) of the outer can (20) so as to bent inward in the radial direction.

Description

Sealed battery and method for manufacturing the same

[0001] The present disclosure relates to sealed batteries and methods for manufacturing sealed batteries.

[0002] A cylindrical battery is known as a sealed battery. The cylindrical battery includes, for example, an electrode assembly, a cylindrical outer can with a bottom that houses the electrode assembly, a sealing body that closes the open end of the outer can, and a gasket that is provided between the outer can and the sealing body. In such a cylindrical battery, the sealing body is crimped to the open end of the outer can via the gasket (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2000-306557

[0004] In the above-described crimping fixation, the open end of the outer can is crimped to form a shoulder bent radially inward. Tensile stress during crimping acts on the inner portion of the shoulder in its thickness, and this tensile stress may remain. In this case, the reliability of the sealed battery may be reduced.

[0005] Therefore, an object of the present disclosure is to provide a sealed battery that can relieve the residual tensile stress in the shoulder portion of the outer can, and a method for manufacturing the sealed battery.

[0006] The sealed battery according to the present disclosure comprises an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, an electrolyte, a cylindrical outer can with a bottom that houses the electrode assembly and the electrolyte, a sealing body that closes the open end of the outer can, and an annular gasket that is interposed between the outer can and the sealing body, and is a sealed battery in which the sealing body is crimped and fixed to the open end of the outer can via the gasket, and is characterized in that a laser irradiation portion is formed on a shoulder portion that is bent radially inward by crimping the open end of the outer can.

[0007] The method for manufacturing a sealed battery according to the present disclosure is a manufacturing process for a sealed battery including an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, an electrolyte, a cylindrical outer can with a bottom that contains the electrode assembly and the electrolyte, a sealing body that closes the open end of the outer can, and an annular gasket that is interposed between the outer can and the sealing body, and is characterized in that the sealing body is crimped and fixed to the open end of the outer can via the gasket, and a laser is irradiated onto a shoulder portion that is bent radially inward by crimping the open end of the outer can.

[0008] According to the sealed battery and the method for manufacturing the sealed battery of the present disclosure, the residual tensile stress in the shoulder portion of the outer can can be alleviated.

[0009] Fig. 3 is an axial cross-sectional view showing a sealed battery according to an embodiment. Fig. 4 is an axial cross-sectional view showing a shoulder portion of the outer can of Fig. 1. Fig. 5 is a flowchart showing a method for manufacturing a sealed battery according to an embodiment. Fig. 6 is a schematic diagram showing a sealing (crimping) step of Fig. 3. Fig. 7 is a schematic diagram showing a laser irradiation step of Fig. 3.

[0010] An example of an embodiment of the present disclosure will be described in detail below. In the following description, specific shapes, materials, directions, numerical values, etc. are examples for facilitating understanding of the present disclosure, and can be appropriately changed according to the application, purpose, specifications, etc.

[0011] [Sealed Battery] A battery 10 as an example of an embodiment will be described with reference to FIG.

[0012] The battery 10 as a sealed battery is a nonaqueous electrolyte secondary battery (lithium ion battery) using a nonaqueous electrolyte. However, the sealed battery of the present disclosure is not limited to the nonaqueous electrolyte secondary battery of the present embodiment, and may be a primary battery or a battery using an aqueous electrolyte. The battery 10 is also a cylindrical battery. However, the sealed battery of the present disclosure is not limited to the cylindrical battery of the present embodiment, and may be a prismatic battery, a button battery, or a coin battery.

[0013] In the following, each component may be described using the axial, radial, and circumferential directions of the battery 10. In addition, the sealing body 21 side in the axial direction (height direction) of the battery 10 may be described as "upper," and the bottom 20A side of the exterior can 20 in the axial direction may be described as "lower."

[0014] 1 , the battery 10 includes an electrode assembly 14, a non-aqueous electrolyte, a bottomed cylindrical outer can 20 that accommodates the electrode assembly 14 and the electrolyte, and a sealing body 21 that closes the opening of the outer can 20. The electrode assembly 14 includes a positive electrode 11, a negative electrode 12, and a separator 13 interposed between the positive electrode 11 and the negative electrode 12, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound with the separator 13 interposed therebetween. The outer can 20 is a bottomed cylindrical container that has a bottom 20A and an open end 20B.

[0015] The electrode assembly 14 includes a long positive electrode 11, a long negative electrode 12, and two long separators 13. The electrode assembly 14 also includes electrode leads, namely, a positive electrode lead 15 joined to the positive electrode 11 and a negative electrode lead 16 joined to the negative electrode 12. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to suppress lithium deposition. Therefore, the lower end of the negative electrode 12 is disposed closer to the bottom 20A of the outer can 20 than the lower end of the positive electrode 11. The two separators 13 are formed to be at least slightly larger than the positive electrode 11 and are disposed to sandwich the positive electrode 11, for example.

[0016] The positive electrode 11 has a positive electrode core and a positive electrode mixture layer provided on both sides 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 contains a positive electrode active material, a conductive agent, such as acetylene black, and a binder, such as polyvinylidene fluoride (PVdF). The positive electrode 11 can be produced 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 a positive electrode mixture layer on both sides of the positive electrode core.

[0017] For example, a lithium transition metal composite oxide is used as the positive electrode active material. Examples of metal elements contained in the lithium transition 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 suitable lithium transition metal composite oxide is a lithium metal composite oxide containing at least one of Ni, Co, and Mn. Specific examples include a composite oxide containing Ni, Co, and Mn, and a composite oxide containing Ni, Co, and Al.

[0018] The negative electrode 12 has a negative electrode core and a negative electrode mixture layer provided on both sides of the negative electrode core. The negative electrode core can be 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). The negative electrode 12 can be produced by applying a negative electrode mixture slurry containing a negative electrode active material, a binder, etc., onto 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.

[0019] The negative electrode active material may be, for example, natural graphite such as flake graphite, lump graphite, or amorphous graphite, or artificial graphite such as lump artificial graphite or graphitized mesophase carbon microbeads. The negative electrode active material may be a metal that alloys with lithium, such as Si or Sn, an alloy containing such a metal, or a compound containing such a metal, which may be used in combination with graphite. A suitable example of such an active material is SiO ２ The Si-containing material is a silicate phase such as lithium silicate, or an amorphous carbon phase in which fine Si particles are dispersed.

[0020] The separator 13 may be, for example, a porous sheet having ion permeability and insulating properties. Specific examples of porous sheets include a microporous thin film, a woven fabric, and a nonwoven fabric. Suitable materials for the separator 13 include olefin-based resins such as polyethylene and polypropylene, and cellulose. The separator 13 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin-based resin. Alternatively, the separator 13 may be a multilayer separator including a polyethylene layer and a polypropylene layer, and the surface of the separator 13 may be coated with a material such as an aramid-based resin or ceramic.

[0021] The non-aqueous electrolyte includes, for example, 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. The non-aqueous solvent may contain a halogen-substituted compound in which at least a portion of the hydrogen atoms in 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 may be LiPF ６ Lithium salts such as

[0022] An upper insulating plate 17 and a lower insulating plate 18 are disposed above and below the electrode body 14. In the example shown in Fig. 1 , a positive electrode lead 15 attached to the positive electrode 11 passes through an opening in the upper insulating plate 17 and extends toward the sealing body 21, and a negative electrode lead 16 attached to the negative electrode 12 passes outside the lower insulating plate 18 and extends toward the bottom 20A of the outer can 20. The positive electrode lead 15 is connected by welding or the like to the inner surface of the valve portion 21A of the sealing body 21 facing inward of the outer can 20, and the sealing body 21 serves as a positive electrode terminal. The negative electrode lead 16 is connected by welding or the like to the inner surface of the bottom 20A of the outer can 20, and the outer can 20 serves as a negative electrode terminal.

[0023] A gasket 19 is provided between the outer can 20 and the sealing body 21 to ensure sealing of the battery interior and insulation between the outer can 20 and the sealing body 21. The outer can 20 includes an opening end 20B, a circumferentially annular groove 20C, and an annular shoulder 20D. The groove 20C is formed by spinning the opening end 20B to recess it radially inward. The shoulder 20D is formed when the opening end 20B is bent radially inward and crimped to the peripheral edge of the sealing body 21. The crimping causes the sealing body 21 to be sandwiched between the shoulder 20D and the groove 20C via the gasket 19, and the sealing body 21 is fixed to the outer can 20.

[0024] The sealing body 21 is a disc-shaped member equipped with an exhaust valve. The sealing body 21 has a valve portion 21A that ruptures when the internal battery pressure exceeds a predetermined threshold. The valve portion 21A includes a downward convex portion that protrudes toward the inside of the battery and is located in the radial center, and a thin-walled portion formed around the downward convex portion. The thickness of the thin-walled portion decreases radially outward. When the internal pressure rises due to an abnormality in the battery 10, the thin-walled portion ruptures, forming a gas exhaust port.

[0025] [Shoulder of External Can] The shoulder 20D of the external can 20 will be described with reference to FIG.

[0026] 2, the outer can 20 has a shoulder 20D formed by crimping the opening end 20B and bending it radially inward. In other words, the shoulder 20D is a bent portion formed by crimping the opening end 20B. The shoulder 20D is formed around the entire circumferential direction at the upper end in the axial direction and the outer end in the radial direction of the outer can 20. A laser irradiation portion 22, which will be described in detail later, is formed on the shoulder 20D.

[0027] The laser irradiated portion 22 is a portion of the shoulder portion 20D that is irradiated with a laser from the outside (the exterior side of the outer can 20). The laser irradiated portion 22, as will be described in detail later, can relieve residual tensile stress in the shoulder portion 20D of the outer can 20. The laser irradiated portion 22 is formed over the entire circumferential direction at the upper end portion in the axial direction and the outer end portion in the radial direction of the outer can 20. In other words, the laser irradiated portion 22 is formed over the entire shoulder portion 20D.

[0028] The laser irradiation portions 22 may be formed in the form of spots at equal intervals along the shoulder portion 20D. In this case, it is preferable that the area in the shoulder portion 20D in which the laser irradiation portions 22 are formed along the circumferential direction is larger than the area in which the laser irradiation portions 22 are not formed.

[0029] The laser irradiated portion 22 is formed in a range from the outer surface of the shoulder portion 20D (the surface facing the outside of the outer can 20) to half the thickness of the shoulder portion 20D. As a result, the inner surface of the shoulder portion 20D (the surface facing the inside of the outer can 20) that is in contact with the gasket 19 is less affected by the heat caused by the laser irradiation, and damage to the gasket 19 due to the laser irradiation can be avoided.

[0030] As described above, sealing body 21 is sandwiched between shoulder portion 20D and groove portion 20C via gasket 19 and is crimped to outer can 20. At this time, tensile stress from crimping acts on the inner portion of shoulder portion 20D in the thickness direction (hereinafter, "inner portion of shoulder portion 20D"), and this tensile stress may remain. In this case, the reliability of battery 10 may be reduced.

[0031] Therefore, by forming the laser irradiated portion 22 on the shoulder portion 20D, tensile stress acts on the outer portion of the thickness of the shoulder portion 20D (hereinafter referred to as the outer portion of the shoulder portion 20D) during laser irradiation. On the other hand, compressive stress acts on the inner portion of the shoulder portion 20D during laser irradiation, which can relieve the residual tensile stress caused by crimping. This improves the reliability of the battery 10.

[0032] [Manufacturing Process of Sealed Battery] The manufacturing process of the battery 10 will be described with reference to Figures 3 to 5. Note that Figure 1 may also be referred to below as appropriate.

[0033] In step S11, the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 interposed therebetween to produce an electrode assembly 14. In step S12, the electrode assembly 14 together with the lower insulating plate 18 is inserted into a cylindrical outer can 20 with a bottom made by drawing a steel plate. In step S13, the inner surface of the bottom 20A of the outer can 20 and the negative electrode lead 16 are welded.

[0034] In step S14, the upper insulating plate 17 is inserted into the outer can 20. In step S15, a groove is formed on the upper side of the upper insulating plate 17 at the open end 20B of the outer can 20 to form a grooved portion 20C. In step S16, a gasket 19 is inserted into the grooved portion 20C. In step S17, the sealing body 21 and the positive electrode lead 15 are welded together. In step S18, an electrolyte is injected into the outer can 20. In step S19, the sealing body 21 is inserted into the open end 20B of the outer can 20.

[0035] In step S20, the sealing body 21 is crimped to the open end 20B of the outer can 20 via the gasket 19. As shown in FIG. 4 , the crimping bends the open end 20B radially inward to form a shoulder 20D. At this time, tensile stress acts on the inner portion of the shoulder 20D (solid arrow in FIG. 4 ). If tensile stress remains in the inner portion of the shoulder 20D, it may reduce the reliability of the battery 10.

[0036] In step S21, a laser is applied from the outside of shoulder portion 20D to form laser irradiated portion 22. At this time, it is preferable to apply the laser so that the temperature of the outer surface of shoulder portion 20D is in the range of 50°C to 200°C. It is also preferable that laser irradiated portion 22 is formed in a range from the outer surface of shoulder portion 20D to half the thickness of shoulder portion 20D. This reduces the thermal effect of laser irradiation on the inner surface of shoulder portion 20D that is in contact with gasket 19, making it possible to avoid damage to gasket 19 due to laser irradiation.

[0037] In step S21, as shown in Fig. 5, laser irradiation applies tensile stress (solid arrows in Fig. 5) to the outer portion of shoulder 20D and compressive stress (dashed arrows in Fig. 5) to the inner portion of shoulder 20D. This reduces the residual tensile stress in the inner portion of shoulder 20D that was generated in step S20. As a result, the reliability of battery 10 can be improved.

[0038] It should be noted that the present disclosure is not limited to the above-described embodiments and their variations, and it goes without saying that various modifications and improvements are possible within the scope of the matters described in the claims of the present application.

[0039] REFERENCE SIGNS LIST 10 Battery (sealed battery), 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15 Positive electrode lead, 16 Negative electrode lead, 17 Upper insulating plate, 18 Lower insulating plate, 19 Sealing body, 20 Outer can, 20A Bottom, 20B Opening edge, 20C Grooved portion, 20D Shoulder portion, 21 Gasket, 22 Laser irradiation portion

Claims

1. A sealed battery comprising: an electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; an electrolytic solution; a bottomed cylindrical exterior can that houses the electrode body and the electrolytic solution; a sealing body that closes an opening end of the exterior can; and an annular gasket interposed between the exterior can and the sealing body, wherein the sealing body is caulked and fixed to the opening end of the exterior can via the gasket, and a laser irradiation portion is formed on a shoulder portion that is bent radially inward by caulking the opening end of the exterior can. Sealed battery.

2. The sealed battery according to claim 1, wherein the laser irradiation portion is formed in a range from an outer surface of the shoulder portion to half of the thickness of the shoulder portion. Sealed battery.

3. A method for manufacturing a sealed battery, comprising: an electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; an electrolytic solution; a bottomed cylindrical exterior can that houses the electrode body and the electrolytic solution; a sealing body that closes an opening end of the exterior can; and an annular gasket interposed between the exterior can and the sealing body, the method comprising caulking and fixing the sealing body to the opening end of the exterior can via the gasket, and laser-irradiating a shoulder portion that is bent radially inward by caulking the opening end of the exterior can. Method for manufacturing a sealed battery.

4. The method for manufacturing a sealed battery according to claim 3, wherein laser irradiation is performed such that the temperature of the outer surface of the shoulder portion is in the range of 50°C to 200°C. Method for manufacturing a sealed battery.

Images