Sealed battery

Abstract

Provided is a battery (10) comprising an electrode body (14) in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, an electrolyte, a bottomed cylindrical outer can (20) that accommodates the electrode body (14) and the electrolyte, a sealing body (21) that closes the open end (20B) of the outer can (20), and an annular gasket (19) that is interposed between the outer can (20) and the sealing body (21), wherein grooves (19C) that connect the radially inner side and the radially outer side are formed on the bottom surface of the gasket (19).

Description

sealed battery

[0001] The present disclosure relates to sealed batteries.

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

[0003] In the manufacturing process for a cylindrical battery, the electrode body is inserted into an outer can, an upper insulating plate is placed above the electrode body, a groove is formed on the upper side of the upper insulating plate at the open end of the outer can to form a grooved portion, a gasket is inserted into the grooved portion, an electrolyte is injected into the outer can, and the sealing body is crimped and fixed to the open end of the outer can via the gasket.

[0004] Japanese Patent Application Laid-Open No. 2000-306557

[0005] In the manufacturing process for the cylindrical battery described above, when forming the grooves in the open end of the outer can, the outer can is rotated at high speed and a jig is pressed against the open end to form the grooves. During this process, the jig presses the radially outer side of the upper insulating plate downward, deforming the upper insulating plate so that the radially inner side of the upper insulating plate protrudes upward. When the gasket is inserted, the gasket and the upper insulating plate may come into close contact with each other. Injecting an electrolyte in this state may prevent the electrolyte from flowing between the upper insulating plate and the gasket, reducing the fluidity of the electrolyte toward the radially outer side of the outer can.

[0006] If the fluidity of the electrolyte solution toward the radially outward direction of the outer can decreases, the electrolyte level may exceed the gasket on the radially inner side of the outer can, causing the electrolyte solution to creep up from the gasket and become trapped between components, such as between the positive electrode cap and the positive electrode current collector plate, or between the positive electrode current collector plate and the positive electrode tab, etc. In this case, there is a risk of a decrease in the quality of the weld when the positive electrode cap and the positive electrode current collector plate are welded together.

[0007] Therefore, an object of the present disclosure is to provide a sealed battery that can improve the fluidity of the electrolyte solution radially outward from the outer can during the manufacturing process.

[0008] The sealed battery according to the present disclosure is a sealed battery comprising 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 a groove portion that connects the radial inside and the radial outside is formed in the bottom surface of the gasket.

[0009] According to the sealed battery of the present disclosure, the fluidity of the electrolyte solution radially outward from the outer can during the manufacturing process can be improved.

[0010] 3 is a cross-sectional view of a sealed battery according to an embodiment of the present invention; FIG. 4 is a perspective view of a gasket according to an embodiment of the present invention, seen from the bottom side; FIG. 5 is a flowchart of a manufacturing process of a sealed battery according to an embodiment of the present invention; FIG. 6 is a schematic diagram showing a groove forming step of FIG. 3; and FIG. 7 is a schematic diagram showing a liquid injection step of FIG.

[0011] 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.

[0012] [Sealed Battery] A battery 10 as an example of an embodiment will be described with reference to FIG.

[0013] 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.

[0014] 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."

[0015] The battery 10 includes an electrode assembly 14, an electrolyte (not shown), and an outer can 20 that accommodates the electrode assembly 14 and the electrolyte. The electrode assembly 14 includes a positive electrode, a negative electrode, and a separator, and has a wound structure in which the positive electrode and the negative electrode are spirally wound with the separator interposed therebetween. The outer can 20 has a cylindrical shape with a bottom and an open top, and the opening of the outer can 20 is closed by a sealing body 21.

[0016] The positive electrode includes a positive electrode current collector and a positive electrode composite layer formed on at least one surface of the current collector. The positive electrode current collector can be a foil of a metal stable within the potential range of the positive electrode, such as aluminum or an aluminum alloy, or a film with such a metal disposed on the surface. The positive electrode composite layer preferably contains a positive electrode active material, a conductive material such as acetylene black, and a binder such as polyvinylidene fluoride, and is formed on both surfaces of the positive electrode current collector. For example, a lithium-containing transition metal composite oxide is used as the positive electrode active material. The positive electrode can be manufactured by applying a positive electrode composite slurry containing a positive electrode active material, a conductive material, and a binder to the positive electrode current collector, drying the coating, and then compressing the coating to form a positive electrode composite layer on both surfaces of the positive electrode current collector.

[0017] The negative electrode includes a negative electrode current collector and a negative electrode composite layer formed on at least one surface of the current collector. The negative electrode current collector 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, or a film with such a metal disposed on the surface. The negative electrode composite layer contains a negative electrode active material and a binder, such as styrene-butadiene rubber (SBR), and is preferably formed on both surfaces of the negative electrode current collector. Examples of the negative electrode active material include graphite and silicon-containing compounds. The negative electrode can be manufactured by applying a negative electrode composite slurry containing a negative electrode active material and a binder to the negative electrode current collector, drying the coating, and then rolling the coating to form a negative electrode composite layer on both surfaces of the current collector.

[0018] For example, a porous sheet having ion permeability and insulating properties is used as the separator. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. Suitable materials for the separator include olefin-based resins such as polyethylene and polypropylene, and cellulose. The separator may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin-based resin. Alternatively, the separator may be a multilayer separator including a polyethylene layer and a polypropylene layer, and the surface of the separator may be coated with a material such as an aramid-based resin or ceramic.

[0019] For example, a non-aqueous electrolyte is used as the electrolyte. The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. For example, esters, ethers, nitriles, amides, and mixed solvents of two or more of these may be used as the non-aqueous solvent. 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. Note that the non-aqueous electrolyte is not limited to a liquid electrolyte, and may also be a solid electrolyte. For example, the electrolyte salt may be LiPF ６ The type of electrolyte is not particularly limited, and may be a water-based electrolyte.

[0020] The battery 10 includes an upper insulating plate 17 and a lower insulating plate 18, which are respectively 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 passes through a through-hole in the upper insulating plate 17 and extends toward the sealing body 21, and a negative electrode lead attached to the negative electrode 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 to a positive electrode current collector 22, which is the bottom plate of the sealing body 21, by welding or the like, and a cap 26, which is the top plate of the sealing body 21 and is electrically connected to the positive electrode current collector 22, serves as a positive electrode external terminal. The negative electrode lead is connected to the inner surface of the bottom 20A of the outer can 20 by welding or the like, and the bottom 20A of the outer can 20 serves as a negative electrode external terminal.

[0021] The outer can 20 is a cylindrical metal container with a bottom. A gasket 19 is provided between the outer can 20 and the sealing body 21 to ensure the sealing of the interior of the battery 10. The gasket 19 will be described in detail below. A grooved portion 20C is formed near the open end 20B of the outer can 20, with part of the side surface protruding inward to support the sealing body 21. The grooved portion 20C is preferably formed in an annular shape along the circumferential direction of the outer can 20, and supports the sealing body 21 on its upper surface. The sealing body 21, supported by the grooved portion 20C, is fixed to the outer can 20 by the open end 20B of the outer can 20, which is crimped to the sealing body 21.

[0022] A thin, easily breakable portion 20D is formed in the bottom 20A of the exterior can 20. The easily breakable portion 20D is formed, for example, by stamping a circle or a C-shape on the underside of the bottom 20A. If the bottom 20A is provided with the easily breakable portion 20D, when the battery 10 generates abnormal heat, the easily breakable portion 20D breaks, allowing high-temperature gas inside the battery 10 to be discharged to the outside, thereby improving the safety of the battery 10.

[0023] The sealing body 21 has a structure in which a positive electrode current collector plate 22 and a cap 26 are stacked in this order from the electrode body 14 side. The components constituting the sealing body 21 are, for example, disk-shaped or ring-shaped and are electrically connected to each other.

[0024] [Gasket] The gasket 19 will be described with reference to FIG.

[0025] As described above, the gasket 19 is a member interposed between the exterior can 20 and the sealing body 21. The gasket 19 can ensure the airtightness of the interior of the battery 10. The gasket 19 can also ensure insulation between the exterior can 20 and the sealing body 21. Furthermore, the groove 19C of the gasket 19, which will be described in detail later, can improve the fluidity of the electrolyte solution radially outward from the exterior can 20 during the manufacturing process of the battery 10.

[0026] An elastic insulating resin is used for the gasket 19. Examples of the elastic insulating resin that may be used include polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), perfluoroalkoxy fluororesin (PFA), and nylon.

[0027] The gasket 19 is formed in an annular shape and includes a ring-shaped main body 19A, a wall portion 19B formed to protrude upward from the outer periphery (the outer end in the radial direction) of the main body 19A, and a groove portion 19C formed in the bottom surface of the main body 19A, each of which will be described in detail later.

[0028] The main body 19A is interposed between the positive electrode current collector plate 22 and the upper insulating plate 17. An opening for pouring an electrolyte solution is formed in the center of the main body 19A. The wall portion 19B is interposed between the outer can 20 and the sealing body 21. After the sealing body 21 is fixed to the open end 20B of the outer can 20 by crimping, the wall portion 19B is formed into a C-shape in cross section as viewed from the circumferential direction.

[0029] As described above, the groove 19C is formed on the bottom surface of the main body 19A. The groove 19C is formed so as to communicate between the radially inner side and the radially outer side. A plurality of grooves 19C are formed, and the plurality of grooves 19C are each formed radially at equal intervals in the circumferential direction. The cross-sectional shape of the groove 19C as viewed from the radial direction may be rectangular, square, trapezoidal, U-shaped, V-shaped, or the like. Furthermore, the cross-sectional shape of the groove 19C as viewed from the radial direction may be formed so as to increase radially outward. This can further improve the fluidity of the electrolyte, which will be described in detail later.

[0030] As will be described in detail later, groove portion 19C makes it easier for the electrolyte to flow radially outward of exterior can 20 when the electrolyte is injected during the manufacturing process of battery 10. This improves the fluidity of the electrolyte to the radially outward of exterior can 20 during the manufacturing process of battery 10. As a result, the reliability of battery 10 can be improved.

[0031] [Manufacturing Process of Sealed Battery] The manufacturing process of the battery 10 will be described with reference to Figures 3 to 5. In the following, Figures 1 and 2 may be referred to as appropriate.

[0032] 3 , in step S11, the positive electrode and negative electrode are spirally wound with a separator interposed therebetween to produce an electrode assembly 14. In step S12, the electrode assembly 14 together with a 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 is welded to the negative electrode lead.

[0033] 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 positive electrode current collector plate 22 and the positive electrode lead 15 are welded together. In step S18, an electrolyte is injected into the outer can 20.

[0034] 4, in step S15 described above, the outer can 20 is rotated at high speed and a jig J is pressed against the open end 20B to form the grooved portion 20C. At this time, the radially outer side of the upper insulating plate 17 is pressed downward by the jig J, and the upper insulating plate 17 may be deformed so that the radially inner side of the upper insulating plate 17 protrudes upward.

[0035] In this case, when the gasket 19 is inserted into the grooved portion 20C in step S16, the upper insulating plate 17 and the gasket 19 come into close contact with each other (see FIG. 5 ). In this state, if an electrolyte is injected into the outer can 20 in step S18, the electrolyte may not flow between the upper insulating plate 17 and the gasket 19, and the fluidity of the electrolyte toward the radially outward direction of the outer can 20 may decrease.

[0036] If the fluidity of the electrolyte solution toward the radially outward direction of the outer can 20 decreases, the level of the electrolyte solution exceeds the gasket 19 on the radially inner side of the outer can 20, and the electrolyte solution creeps up from the gasket 19 and becomes interposed between the positive current collector 22 and the positive electrode lead 15. In this case, there is a risk of deterioration in welding quality when the positive current collector 22 and the positive electrode lead 15 are welded together in step S17, for example.

[0037] Therefore, as described above, by forming groove 19C in the bottom surface of gasket 19 that connects the radially inner side to the radially outer side as shown in Fig. 5, even if electrolyte is injected into outer can 20 with upper insulating plate 17 and gasket 19 in close contact, the electrolyte solution is more likely to flow radially outward of outer can 20 (arrows in Fig. 5). This makes it possible to improve the fluidity of the electrolyte solution radially outward of outer can 20 during the manufacturing process of battery 10. As a result, the reliability of battery 10 can be improved.

[0038] 3, in step S19, sealing body 21 is inserted into opening edge 20B of outer can 20. In step S20, sealing body 21 is fixed to opening edge 20B of outer can 20 by crimping with gasket 19 interposed therebetween.

[0039] 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.

[0040] 10 Battery (sealed battery), 14 Electrode body, 15 Positive electrode lead, 16 Negative electrode lead, 17 Upper insulating plate, 18 Lower insulating plate, 19 Gasket, 19A Body, 19B Wall portion, 19C Groove portion, 20 Outer can, 20A Bottom portion, 20B Cylindrical portion, 20C Grooved portion, 20D Easy-to-break portion, 21 Sealing body, 22 Positive electrode current collector plate, 26 Cap

Claims

1. A sealed battery comprising: 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, wherein a groove that connects the radially inner side and the radially outer side is formed in the bottom surface of the gasket.

2. A sealed battery according to claim 1, wherein a plurality of said grooves are formed, and each of said plurality of grooves is formed radially.

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