Method for manufacturing sealed battery

Abstract

This manufacturing process of a battery (10) comprises an aging step (S15) in which the battery (10) is stored at an ambient temperature equal to or higher than a room temperature, and a heat treatment step (S18) in which, after the aging step (S15), the battery (10) is stored at an ambient temperature higher than the ambient temperature of the aging step (S15), wherein a state of charge (SOC) of the battery (10) in the heat treatment step (S18) is lower than the SOC of the battery (10) in the aging step (S15).

Description

Sealed battery manufacturing method

[0001] The present disclosure relates to a method for manufacturing a sealed battery.

[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 (see, for example, Patent Document 1). In a manufacturing method for such a cylindrical battery, the sealing body is crimped to the open end of the outer can via the gasket.

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

[0004] However, in the manufacturing process of the cylindrical battery described above, the crimping of the sealing body may cause a localized processing load on the gasket, which may cause localized strain in the gasket, which may cause the gasket to break and reduce the sealing performance of the cylindrical battery.

[0005] Therefore, an object of the present disclosure is to provide a method for manufacturing a sealed battery that can alleviate local strain in the gasket.

[0006] The method for manufacturing a sealed battery according to the present disclosure includes an aging process in which a sealed battery is stored at an environmental temperature equal to or higher than room temperature, and a heat treatment process in which the sealed battery is stored after the aging process at an environmental temperature higher than the environmental temperature of the aging process, and is characterized in that the environmental temperature of the sealed battery in the heat treatment process is higher than the environmental temperature of the sealed battery in the aging process, and the state of charge (SOC) of the sealed battery in the heat treatment process is lower than the SOC of the sealed battery in the aging process.

[0007] According to the manufacturing method of the sealed battery of the present disclosure, local strain in the gasket can be alleviated.

[0008] 1 is a cross-sectional view of a sealed battery according to an embodiment of the present invention, taken along an axial direction thereof;

[0009] 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.

[0010] A method for manufacturing a battery 10 as an example of an embodiment will be described with reference to FIGS. 1 and 2. FIG.

[0011] As shown in FIG. 1 , 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 this embodiment, and may be a primary battery or a battery using an aqueous electrolyte. Battery 10 is also a cylindrical battery. However, the sealed battery of the present disclosure is not limited to the cylindrical battery of this embodiment, and may be a prismatic battery, a button battery, or a coin battery.

[0012] 2, the manufacturing process of battery 10 includes a battery assembly step S11, an initial charge / discharge step S12, a charging step S13, a first voltage measurement step S14, an aging step S15, a second voltage measurement step S16, a discharging step S17, a heat treatment step S18, and a sorting step S19, and the steps proceed in this order. Each step will be described below.

[0013] The battery assembly process S11 is a process for assembling, for example, the battery 10 shown in Fig. 1. In the following, each component may be described using the axial direction, radial direction, and circumferential direction of the battery 10. Also, 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 outer can 20 in the axial direction may be described as "lower."

[0014] First, the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 interposed therebetween to produce an electrode assembly 14. The positive electrode 11 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, 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 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 sides 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 11 can be produced by applying a positive electrode composite slurry containing a positive electrode active material, a conductive material, a binder, etc., onto the positive electrode current collector, drying the coating, and then compressing the coating to form a positive electrode composite layer on both sides of the positive electrode current collector.

[0015] The negative electrode 12 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 12, 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 12 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.

[0016] 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.

[0017] Next, the electrode body 14 together with the lower insulating plate 18 is inserted into a bottomed cylindrical outer can 20 made by drawing a steel plate, and the negative electrode lead 16 is welded to the inner surface of the bottom 20A of the outer can 20. The negative electrode lead 16 is attached to the negative electrode 12 and extends to the bottom 20A side of the outer can 20, passing outside the lower insulating plate 18. The negative electrode lead 16 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.

[0018] Next, the upper insulating plate 17 is inserted into the outer can 20, and a groove is formed in the open end 20B of the outer can 20 to form the grooved portion 20C. The grooved portion 20C is formed by part of the side surface of the outer can 20 protruding inward near the open end 20B, and its upper surface supports the sealing body 21. The grooved portion 20C is preferably formed in an annular shape along the circumferential direction of the outer can 20.

[0019] Next, the gasket 19 is inserted into the open end 20B of the outer can 20 and placed on the upper surface of the grooved portion 20C. An elastic insulating resin can be used for the gasket 19. Examples of such resins include polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), perfluoroalkoxy fluororesin (PFA), nylon, etc.

[0020] Next, the positive electrode lead 15 is welded to an internal terminal plate 22 of the sealing body 21, which will be described later. The positive electrode lead 15 is attached to the positive electrode 11 and extends toward the sealing body 21 through a through hole in the upper insulating plate 17. The positive electrode lead 15 is connected by welding or the like to the underside of the internal terminal plate 22, which is the bottom plate of the sealing body 21, and a cap 26, which is the top plate of the sealing body 21 and is electrically connected to the internal terminal plate 22, serves as a positive electrode external terminal.

[0021] Next, a non-aqueous electrolyte is injected into the outer can 20. The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous solvent may be, for example, an ester, an ether, a nitrile, an amide, or a mixed solvent 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. The electrolyte salt may be, for example, LiPF ６ The type of electrolyte is not particularly limited, and may be an aqueous electrolyte.

[0022] Next, the sealing body 21 is inserted into the gasket 19, and the open end 20B of the outer can 20 is crimped onto the sealing body 21 to secure it in place. The sealing body 21 has a structure in which, in order from the electrode body 14 side, an internal terminal plate 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26 are stacked. The components constituting the sealing body 21 are, for example, disk-shaped or ring-shaped, and all components except for the insulating member 24 are electrically connected to each other. The lower valve body 23 and the upper valve body 25 are connected to each other at their respective centers, and the insulating member 24 is interposed between their respective peripheral edges. When the internal pressure of the battery 10 increases due to abnormal heat generation, the lower valve body 23 deforms and breaks, pushing the upper valve body 25 toward the cap 26, thereby interrupting the current path between the lower valve body 23 and the upper valve body 25. If the internal pressure rises further, the upper valve body 25 breaks, and gas is discharged from the vent hole 26A of the cap 26.

[0023] In the battery assembly step S11, a local processing load acts on the gasket 19 due to the above-described crimping of the sealing body 21, which may cause local strain in the gasket 19. In this case, there is a risk of the gasket 19 breaking. As will be described in detail later, the local strain generated in the gasket 19 can be alleviated in the heat treatment step S18.

[0024] The initial charge / discharge step S12 is a step of initially charging and discharging the battery 10. The initial charge / discharge is the first charge / discharge performed after the battery 10 is assembled.

[0025] In the initial charge / discharge, it is preferable to charge the battery 10 until the state of charge (SOC) reaches 100% and discharge it until the SOC reaches 0%. However, the charge in the initial charge / discharge may be performed until the SOC is less than 100%. Furthermore, the discharge in the initial charge / discharge does not have to be performed until the SOC reaches 0%, but in order to improve the accuracy of subsequent voltage measurements of the battery 10, it is preferable to discharge it until the SOC reaches at least 5% or less, more preferably 1% or less, and even more preferably 0%.

[0026] The charging step S13 is a step of constant voltage charging or constant voltage-constant current charging of the battery 10. In the charging step S13, the battery 10 is charged until the SOC of the battery 10 reaches 40%. However, in the charging step S13, the battery 10 may be charged until the SOC of the battery 10 reaches more than 40%.

[0027] The first voltage measurement step S14 is a step of measuring the voltage V1 of the battery 10 before the aging step S15.

[0028] The aging step S15 is a step of aging the battery 10 by storing it at an ambient temperature equal to or higher than room temperature. The aging step S15 may be performed in a thermostatic bath, for example.

[0029] In the aging step S15, the SOC of the battery 10 (hereinafter referred to as the aging SOC) is the SOC (40%) to which the battery 10 was charged in the charging step S13 described above. However, the aging SOC may be higher than 40% as described above.

[0030] In the aging step S15, the temperature at which the battery 10 is aged (hereinafter referred to as the aging environment temperature) is set to a range of more than 40° C. and less than 60° C. In this embodiment, the aging environment temperature is set to 45±3° C. This makes it possible to stabilize the battery characteristics.

[0031] In the aging step S15, the time for aging the battery 10 (hereinafter referred to as the aging time) is set to 56 hours. However, the aging time may be determined appropriately based on the specifications of the battery 10.

[0032] The second voltage measurement step S16 is a step of measuring the voltage V2 of the battery 10 after the aging step S15.

[0033] The discharging step S17 is a step of discharging the battery 10 until the SOC of the battery 10 reaches a discharged state. Here, the discharged state refers to a state in which the SOC of the battery 10 is 30% or less. The discharged state refers to an SOC lower than the aging SOC. In this embodiment, the discharging step S17 discharges the battery 10 until the SOC of the battery 10 reaches 30%. However, in the discharging step S17, the battery 10 may also be discharged until the SOC of the battery 10 reaches less than 30%. In this embodiment, only the discharging step S17 is performed before the heat treatment step S18 described below, but the discharging step S17 and a charging step may also be performed before the heat treatment step S18.

[0034] The heat treatment step S18 is a step of heat treating the battery 10 by storing it at a temperature higher than the aging temperature. In the heat treatment step S18, the battery 10 is heat treated, thereby alleviating the local distortion of the gasket 19 that occurred in the battery assembly step S11 described above. More specifically, heat treating the gasket 19 promotes viscoelasticity of the crystals due to crystal relaxation of the resin that forms the gasket 19, thereby alleviating the stress in the gasket 19 and thereby alleviating the distortion of the gasket 19. The aging step S15 may be performed, for example, in a constant temperature bath.

[0035] In the heat treatment step S18, the SOC of the battery 10 (hereinafter referred to as the heat treatment SOC) is the SOC (30%) discharged in the above-described discharge step S17. However, as described above, the heat treatment SOC may be less than 30%. Also, the heat treatment SOC may be 5% or less. Also, in the heat treatment step S18, as described above, the heat treatment SOC is set lower than the aging SOC.

[0036] In the heat treatment step S18, the temperature at which the battery 10 is heat treated (hereinafter referred to as the heat treatment ambient temperature) is set higher than the aging ambient temperature. Specifically, in the heat treatment step S18, the heat treatment ambient temperature is set in the range of more than 60°C and less than 100°C, and preferably more than 60°C and less than 80°C. In this embodiment, the heat treatment ambient temperature is set to 65°C. However, the heat treatment ambient temperature may be determined appropriately based on the material of the gasket 19.

[0037] In the heat treatment step S18, the time for which the battery 10 is heat treated (hereinafter referred to as the heat treatment time) is shorter than the aging time. In addition, in the heat treatment step S18, the heat treatment time is set to 24 hours or more. In this embodiment, the heat treatment time is set to 48 hours.

[0038] The sorting step S19 is a step of calculating the voltage difference ΔV between the voltage V1 measured in the first voltage measurement step S14 and the voltage V2 measured in the second voltage measurement step S16, and sorting the batteries 10 based on the voltage difference ΔV. The sorting is performed, for example, by classifying the battery 10 as a non-defective product if the voltage difference ΔV is within a range of the sorting criteria, and classifying the battery 10 as a defective product if the voltage difference ΔV is outside the range of the sorting criteria.

[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] REFERENCE SIGNS LIST 10 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 gasket, 20 outer can, 20B opening end, 20C grooved portion, 21 sealing body, 22 internal terminal plate, 23 lower valve body, 24 insulating member, 25 upper valve body, 26 cap, 26A ventilation hole, S11 battery assembly process, S12 initial charge / discharge process, S13 charging process, S14 first voltage measurement process, S15 aging process, S16 second voltage measurement process, S17 discharging process, S18 heat treatment process, S19 sorting process

Claims

1. An aging process of storing a sealed battery at an environmental temperature equal to or higher than room temperature, and a heat treatment process of storing the sealed battery at an environmental temperature higher than the environmental temperature of the aging process after the aging process, wherein a state of charge (SOC) of the sealed battery in the heat treatment process is lower than the SOC of the sealed battery in the aging process. A method for manufacturing a sealed battery.

2. The method for manufacturing a sealed battery according to claim 1, wherein the sealed battery in the heat treatment process is in a discharged state. A method for manufacturing a sealed battery.

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