Manufacturing method of secondary battery and secondary battery

Abstract

To provide a manufacturing method of a secondary battery in which an electrolyte does not adhere to an inner side of an opening end part of an outer can.SOLUTION: In a manufacturing method of a secondary battery 10, an electrode body 14 in which a positive electrode 11 and a negative electrode 12 are wound with a separator 13 interposed therebetween is inserted into a bottomed cylindrical outer can 16, a grooved part 22 is formed in an opening end part 16A of an outer can 16, a gasket 28 is inserted into the grooved part 22 of the outer can 16, an electrolytic solution is injected into the outer can 16, a sealing body 17 is inserted from above the gasket 28, and the opening end part 16A of the outer can 16 is caulked and fixed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a secondary battery and a secondary battery. [Background technology]

[0002] The secondary battery includes 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 (for example, Patent Document 1).

[0003] In the manufacturing process of the secondary battery described above, a groove is formed in the open end of the outer can, an electrolyte is poured into the outer can, and a gasket is inserted into the groove of the outer can. When the gasket is inserted into the groove of the outer can, the electrolyte adhering to the inside of the outer can is scraped off by the gasket. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2022 / 196172 Summary of the Invention [Problem to be solved by the invention]

[0005] However, due to dimensional variations in the gasket and the outer can, the gasket may not be able to adequately scrape off the electrolyte adhering to the inside of the outer can. If the electrolyte remains above the groove in the outer can, the electrolyte may leak or corrode the sealing cap or the outer can.

[0006] Therefore, an object of the present disclosure is to provide a method for manufacturing a secondary battery in which the electrolyte does not adhere to the inside of the open end of the outer can. [Means for solving the problem]

[0007] The method for manufacturing a secondary battery according to the present disclosure is characterized by inserting an electrode assembly, in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, into a cylindrical outer can with a bottom, forming a groove in the open end of the outer can, inserting a gasket into the groove in the outer can, injecting an electrolyte into the outer can, and inserting a sealing body from above the gasket to crimp and fix the open end of the outer can. [Effects of the Invention]

[0008] According to the method for manufacturing a secondary battery of the present disclosure, the electrolyte is injected into the outer can after the gasket is inserted into the grooved portion of the outer can, so that the electrolyte does not adhere to the inside of the open end of the outer can. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a side cross-sectional view showing a secondary battery as an example of an embodiment. [Figure 2] 1 is a side cross-sectional view showing a gasket according to an embodiment of the present invention; [Figure 3] FIG. 2 is a flow chart showing a method for manufacturing a secondary battery according to an embodiment. [Figure 4] FIG. 10 is a schematic diagram showing a step of inserting a gasket. [Figure 5] FIG. 4 is a schematic diagram for explaining the state of the gasket after sealing. DETAILED DESCRIPTION OF THE INVENTION

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

[0012] The secondary battery 10 includes a wound electrode assembly 14, a non-aqueous electrolyte, and an outer can 16 that accommodates the electrode assembly 14 and the non-aqueous electrolyte. The secondary battery 10 is, for example, a lithium-ion secondary battery. The electrode assembly 14 has a positive electrode 11, a negative electrode 12, and a separator 13, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 interposed therebetween. The outer can 16 is a cylindrical metal container with a bottom and an open axial end, and the opening of the outer can 16 is closed by a sealing member 17. For ease of explanation, the sealing member 17 side of the battery will be referred to as the top, and the bottom side of the outer can 16 will be referred to as the bottom.

[0013] The positive electrode 11, negative electrode 12, and separator 13 that make up the electrode assembly 14 are all long, strip-like bodies that are spirally wound and alternately stacked in the radial direction of the electrode assembly 14. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium deposition. That is, the negative electrode 12 is formed to be longer than the positive electrode 11 in the length direction (longitudinal direction) and width direction (transverse direction). The separator 13 is formed to be at least slightly larger than the positive electrode 11, and for example, two separators 13 are arranged to sandwich the positive electrode 11. The electrode assembly 14 has a positive electrode lead 20 connected to the positive electrode 11 by welding or the like, and a negative electrode lead 21 connected to the negative electrode 12 by welding or the like.

[0014] The positive electrode 11 has a positive electrode core and a positive electrode mixture layer disposed on the positive electrode core. The positive electrode core can be made of a foil of a metal that is stable within the potential range of the positive electrode 11, such as aluminum, an aluminum alloy, stainless steel, or titanium, 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, and a binder, and is preferably provided on both sides of the positive electrode core. 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, and a binder 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.

[0015] Examples of conductive agents contained in the positive electrode mixture layer include carbon black such as acetylene black and ketjen black, graphite, carbon nanotubes (CNTs), carbon nanofibers, graphene, metal fibers, metal powder, and conductive whiskers. One type of conductive agent may be used alone, or multiple types may be used in combination. The content of the conductive agent is not particularly limited, but is, for example, 0.1% by mass or more and 5% by mass or less relative to the mass of the positive electrode mixture layer.

[0016] Examples of binders contained in the positive electrode mixture layer include fluorine-containing resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), olefin resins such as polyethylene, polypropylene, ethylene-propylene-isoprene copolymer, and ethylene-propylene-butadiene copolymer, and acrylic resins such as polyacrylonitrile (PAN), polyimide, polyamide, and ethylene-acrylic acid copolymer. These resins may also be used in combination with carboxymethyl cellulose (CMC) or a salt thereof, polyethylene oxide (PEO), or the like. One type of binder may be used alone, or multiple types may be used in combination. The content of the binder is not particularly limited, but is, for example, 0.1% by mass or more and 5% by mass or less relative to the mass of the positive electrode mixture layer.

[0017] The negative electrode 12 has a negative electrode core and a negative electrode mixture layer disposed on the negative electrode core. The negative electrode core can be made of a foil of a metal stable within the potential range of the negative electrode 12, such as copper, copper alloy, stainless steel, nickel, or nickel alloy, or a film with such a metal disposed on its surface. The negative electrode mixture layer contains a negative electrode active material and a binder and is preferably provided on both sides of the negative electrode core. The negative electrode 12 can be fabricated, for example, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder to 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. Metallic lithium foil can also be used as the negative electrode 12. Alternatively, the negative electrode 12 may be composed only of a negative electrode core, with metallic lithium being deposited on the core surface during battery charging.

[0018] The negative electrode active material is not particularly limited as long as it reversibly absorbs and releases lithium ions, and typically, carbon materials such as graphite are used. Elements that alloy with Li, such as Si and Sn, or materials containing such elements may also be used as the negative electrode active material. Among these, silicon-containing materials containing Si are preferred. Lithium titanate, which has a higher charge / discharge potential relative to metallic lithium than carbon materials, may also be used as the negative electrode active material. One type of negative electrode active material may be used alone, or multiple types may be used in combination.

[0019] The carbon material functioning as the negative electrode active material is, for example, at least one selected from the group consisting of natural graphite, artificial graphite, soft carbon, and hard carbon. Among these, artificial graphite such as massive artificial graphite (MAG) and graphitized mesophase carbon microbeads (MCMB), natural graphite such as flake graphite, massive graphite, and amorphous graphite, or a mixture thereof is preferred. Examples of silicon-containing materials functioning as the negative electrode active material include silicon alloys, silicon compounds, and composite materials containing Si. A suitable silicon-containing material is a composite particle containing an ion-conducting phase and a Si phase dispersed in the ion-conducting phase.

[0020] The binder contained in the negative electrode mixture layer can be, as in the case of the positive electrode 11, a fluororesin, an olefin resin, PAN, polyimide, polyamide, an acrylic resin, or the like. However, polyvinyl acetate, styrene-butadiene rubber (SBR), or the like may also be used. Among these, SBR is preferably used. One type of binder may be used alone, or multiple types may be used in combination. Furthermore, the negative electrode mixture layer preferably contains CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol (PVA), or the like. These function as thickeners in the negative electrode mixture slurry. The content of the binder is not particularly limited, but is, for example, 0.1% by mass or more and 5% by mass or less with respect to the mass of the negative electrode mixture layer. The negative electrode mixture layer may also contain a conductive agent such as CNT.

[0021] [Separator] 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. Suitable materials for the separator 13 include polyolefins such as polyethylene and polypropylene, and cellulose. The separator 13 may have a single-layer structure or a multi-layer structure. Furthermore, a highly heat-resistant resin layer such as an aramid resin may be formed on the surface of the separator 13.

[0022] A filler layer containing an inorganic filler may be formed at the interface between separator 13 and at least one of positive electrode 11 and negative electrode 12. Examples of inorganic fillers include oxides and phosphate compounds containing metal elements such as Ti, Al, Si, and Mg. The filler layer can be formed by applying a slurry containing the filler to the surface of positive electrode 11, negative electrode 12, or separator 13.

[0023] The non-aqueous electrolyte has ion conductivity (for example, lithium ion conductivity). The non-aqueous electrolyte may be a liquid electrolyte (electrolytic solution) or a solid electrolyte.

[0024] The electrolytic solution contains, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent that can be used include esters, ethers, nitriles such as acetonitrile, amides such as dimethylformamide, 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. Examples of the halogen-substituted compound include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated chain carbonates, and fluorinated chain carboxylic acid esters such as methyl fluoropropionate (FMP).

[0025] An upper insulating plate 18 and a lower insulating plate 19 are disposed above and below the electrode body 14. In the example shown in FIG. 1 , the positive electrode lead 20 passes through a through-hole in the upper insulating plate 18 and extends toward the sealing body 17, and the negative electrode lead 21 passes outside the lower insulating plate 19 and extends toward the bottom side of the outer can 16. The positive electrode lead 20 is connected to the underside of an internal terminal plate 23 of the sealing body 17 by welding or the like, and a cap 27, which is the top plate of the sealing body 17 and is electrically connected to the internal terminal plate 23, serves as the positive electrode terminal. The negative electrode lead 21 is connected to the inner bottom surface of the outer can 16 by welding or the like, and the outer can 16 serves as the negative electrode terminal.

[0026] A gasket 28 is provided between the outer can 16 and the sealing body 17 to ensure airtightness inside the battery. The gasket 28 will be described in detail later. The outer can 16 has a grooved portion 22 formed on its side surface that protrudes inward and supports the sealing body 17. The grooved portion 22 is preferably formed in an annular shape along the circumferential direction of the outer can 16, and supports the sealing body 17 on its top surface. The sealing body 17 is fixed to the top of the outer can 16 by the grooved portion 22 and the open end 16A of the outer can 16, which is crimped to the sealing body 17.

[0027] The sealing body 17 has a structure in which, in order from the electrode body 14 side, an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are layered. 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 lower valve body 24 and the upper valve body 26 are connected at their respective centers, and the insulating member 25 is interposed between their respective peripheral edges. When the internal pressure of the battery increases due to abnormal heat generation, the lower valve body 24 deforms and ruptures, pushing the upper valve body 26 toward the cap 27, thereby interrupting the current path between the lower valve body 24 and the upper valve body 26. When the internal pressure further increases, the upper valve body 26 ruptures, and gas is discharged from the opening of the cap 27.

[0028] [gasket] A gasket 28 as an example of an embodiment will be described with reference to Fig. 2. Fig. 2 shows the gasket 28 before it is inserted into the outer can 16.

[0029] As described above, gasket 28 is interposed between outer can 16 and sealing body 17. Gasket 28 can ensure the airtightness of the interior of secondary battery 10. Furthermore, as will be described in detail later, gasket 28 can be temporarily fixed to grooved portion 22 of outer can 16 during the manufacturing process of secondary battery 10. Furthermore, as will be described in detail later, gasket 28 can prevent electrolyte from splashing up and adhering to the inside of opening end 16A above grooved portion 22 of outer can 16 when electrolyte is injected during the manufacturing process of secondary battery 10.

[0030] An elastic insulating resin is used for the gasket 28. 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.

[0031] The gasket 28 is formed in an annular shape. The gasket 28 has a ring-shaped main body 29 and a protrusion 30 that protrudes downward from the main body 29, as will be described in detail later.

[0032] Main body 29 is interposed between sealing body 17 and upper insulating plate 18. An opening 29A for pouring an electrolyte solution is formed in the center of main body 29. After sealing body 17 is fixed to open end 16A of outer can 16 by crimping, main body 29 is formed into a C-shape in a side cross-sectional view.

[0033] As described above, the protrusion 30 protrudes downward from the main body 29 in a side cross-sectional view. The protrusion 30 is provided on the edge of the bottom surface of the main body 29. The protrusion 30 is formed around the entire circumference along the annular shape in a plan view. The protrusion of the present disclosure may be formed only partially around the annular shape in a plan view. The protrusion 30 allows the gasket 28 to be temporarily fixed to the grooved portion 22 of the outer can 16 during the manufacturing process of the secondary battery 10, as will be described in detail later. Furthermore, the protrusion 30 prevents the electrolyte from splashing up and adhering to the inside of the opening end 16A above the grooved portion 22 of the outer can 16 when the electrolyte is poured during the manufacturing process of the secondary battery 10, as will be described in detail later.

[0034] An engagement portion 30A is formed at the tip of the protrusion 30. The engagement portion 30A is formed in a flange shape that protrudes outward. As will be described in detail below, the engagement portion 30A engages with the grooved portion 22 of the outer can 16 when the gasket 28 is inserted into the grooved portion 22 in the outer can 16 during the manufacturing process of the secondary battery 10. This allows the gasket 28 to be temporarily fixed to the grooved portion 22 of the outer can 16 during the manufacturing process of the secondary battery 10.

[0035] [Secondary battery manufacturing process] A manufacturing process of the secondary battery 10 as an example of the embodiment will be described with reference to FIG.

[0036] 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 a lower insulating plate 19 is inserted into a cylindrical outer can 16 with a bottom made by drawing a steel plate. In step S13, the inner surface of the bottom of the outer can 16 and the negative electrode lead 21 are welded.

[0037] In step S14, the upper insulating plate 18 is inserted into the outer can 16. In step S15, a groove is machined on the upper side of the upper insulating plate 18 at the open end 16A of the outer can 16 to form a grooved portion 22. In step S16 (insertion step S16, described in detail below), a gasket 28 is inserted into the grooved portion 22. In step S17, the sealing body 17 and the positive electrode lead 20 are welded together. In step S18 (hereinafter referred to as the injection step S18), an electrolyte is injected into the outer can 16 from an opening 29A in the center of the gasket 28. In step S19, the sealing body 17 is inserted into the open end 16A of the outer can 16. In step S20 (crimping step S20, described in detail below), the sealing body 17 is crimped and fixed to the open end 16A of the outer can 16 with the gasket 28 interposed therebetween.

[0038] In the conventional manufacturing process for secondary batteries, electrolyte is poured into an outer can, a gasket is inserted into the groove of the outer can, and a sealing body is inserted from above the gasket and crimped to secure the open edge of the outer can. When the gasket is inserted into the groove of the outer can, the gasket scrapes out any electrolyte adhering to the inside of the open edge of the outer can (above the groove). However, due to dimensional variations in the gasket and outer can, there are cases where the gasket is unable to sufficiently scrape out the electrolyte adhering to the inside of the outer can.

[0039] In the manufacturing process for the secondary battery 10 of this embodiment, the gasket 28 is inserted into the grooved portion 22 of the outer can 16, the electrolyte is poured into the outer can 16, and the sealing body 17 is inserted from above the gasket 28 and the open end 16A of the outer can 16 is crimped and fixed. In other words, the electrolyte is poured after the gasket 28 is inserted inside the open end 16A of the outer can 16 (above the grooved portion 22). This prevents the electrolyte from adhering to the inside of the open end 16A above the grooved portion 22 of the outer can 16.

[0040] [Gasket insertion process] Referring to FIG. 4, the step S16 of inserting the gasket 28, which is an example of the embodiment, will be described.

[0041] In the insertion step S16, as described above, the gasket 28 is inserted into the grooved portion 22 of the outer can 16. When the gasket 28 has been inserted up to the grooved portion 22 of the outer can 16, the engaging portion 30A of the protrusion 30 engages with the grooved portion 22 inside the outer can 16. This allows the gasket 28 to be temporarily fixed in the grooved portion 22 of the outer can 16. As a result, the gasket 28 does not flap in the injection step S18 that follows the insertion step S16.

[0042] Furthermore, in the insertion step S16, when the engaging portion 30A of the protrusion 30 engages with the grooved portion 22, the engaging portion 30A is in close contact with the lower surface of the grooved portion 22 inside the outer can 16. At this time, if the inward-most protruding point on the inner surface of the grooved portion 22 is defined as P1 and the inward-most protruding point of the engaging portion 30A is defined as P2, then P2 is located outside P1 and P2 is located below P1. This prevents the electrolyte from splashing up and adhering to the inside of the opening end 16A of the outer can 16 above the grooved portion 22 when the electrolyte is injected in the injection step S18 that follows the insertion step S16.

[0043] [Sealing body crimping process] In the crimping step S20, as described above, the sealing body 17 is crimped and fixed to the opening edge 16A of the outer can 16 via the gasket 28 (see FIGS. 1 and 5). Specifically, a jig is inserted into the grooved portion 22 of the outer can 16, and the opening edge 16A is bent inward and pressed from above, causing the lower portion of the grooved portion 22 to deform from a state in which it faces diagonally upward toward the inside to a horizontal state. At this time, as shown in FIG. 5, the engaging portion 30A moves away from the bottom surface of the grooved portion 22. In other words, the engaging portion 30A is in close contact with the bottom surface of the grooved portion 22 only during the injection step S18, when there is a possibility that the electrolyte will splash up and adhere to the inside of the opening edge 16A above the grooved portion 22 of the outer can 16.

[0044] [summary] The present disclosure is further illustrated by the following embodiments. Configuration 1: An electrode assembly in which the positive electrode and the negative electrode are wound with a separator interposed therebetween is inserted into a cylindrical outer can with a bottom, forming a grooved portion at an open end of the outer can; a gasket is inserted into the groove of the outer can; Injecting an electrolyte into the outer can; a sealing body is inserted from above the gasket and the open end of the outer can is crimped and fixed; A method for manufacturing a secondary battery. Configuration 2: A method for producing the secondary battery according to configuration 1, After inserting the gasket into the groove of the outer can, a protrusion protruding downward from the gasket is engaged with the groove inside the outer can. A method for manufacturing a secondary battery. Configuration 3: A method for producing the secondary battery according to configuration 2, comprising: after inserting the gasket into the grooved portion of the outer can, the protrusion is brought into contact with a lower surface of the grooved portion inside the outer can. A method for manufacturing a secondary battery. Configuration 4: A method for producing a secondary battery according to configuration 3, comprising: After the opening end of the outer can is fixed by crimping, the protrusion is separated from the lower surface of the grooved portion inside the outer can. A method for manufacturing a secondary battery. Configuration 5: A secondary 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 an open end of the outer can; and an annular gasket that is interposed between the outer can and the sealing body, a grooved portion for supporting the sealing body and the gasket is formed at the open end of the outer can; The gasket has a protrusion that protrudes downward, The protrusion engages with the groove. Secondary battery.

[0045] 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. [Explanation of symbols]

[0046] 10 secondary battery, 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 16 outer can, 16A opening end, 16B inner portion, 16C grooved upper portion, 17 sealing body, 18 upper insulating plate, 19 lower insulating plate, 20 positive electrode lead, 21 negative electrode lead, 22 grooved portion, 23 internal terminal plate, 24 lower valve body, 25 insulating member, 26 upper valve body, 27 cap, 28 gasket, 29 main body, 29A opening, 30 protrusion, 30A engagement portion, S15 insertion process, S16 liquid injection process, S20 crimping process

Claims

1. An electrode assembly in which the positive electrode and the negative electrode are wound with a separator interposed therebetween is inserted into a cylindrical outer can with a bottom, forming a grooved portion at an open end of the outer can; a gasket is inserted into the groove of the outer can; Injecting an electrolyte into the outer can; a sealing body is inserted from above the gasket and the open end of the outer can is crimped and fixed; A method for manufacturing a secondary battery.

2. A method for manufacturing a secondary battery according to claim 1, After inserting the gasket into the groove of the outer can, a protrusion protruding downward from the gasket is engaged with the groove inside the outer can. A method for manufacturing a secondary battery.

3. 3. A method for manufacturing a secondary battery according to claim 2, comprising: When a protrusion protruding downward from the gasket is engaged with the groove, the protrusion is brought into contact with a lower surface of the groove inside the outer can. A method for manufacturing a secondary battery.

4. The method for manufacturing a secondary battery according to claim 3, After the opening end of the outer can is fixed by crimping, the protrusion is separated from the lower surface of the grooved portion inside the outer can. A method for manufacturing a secondary battery.

5. A secondary 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 an open end of the outer can; and an annular gasket that is interposed between the outer can and the sealing body, a grooved portion for supporting the sealing body and the gasket is formed at the open end of the outer can; The gasket has a protrusion that protrudes downward, The protrusion engages with the groove. Secondary battery.

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