Cylindrical nonaqueous electrolyte secondary battery

Abstract

Provided is a secondary battery in which corrosion of an opening end of an outer package can is suppressed. A nonaqueous electrolyte secondary battery according to one aspect of the present disclosure includes: an outer package can which has a bottomed cylindrical shape and is provided with a groove part at an opening part; an electrode body and a nonaqueous electrolyte solution, which are housed in the outer package can; and a sealing body which is fixed by swaging between the groove part and an opening end of the outer package can by the intermediary of a gasket. The inner surface of the opening part has a first compression region in which the gasket is compressed from the opening end side and a second compression region in which the gasket is compressed from the groove part side, and an absorbent for absorbing the nonaqueous electrolyte solution is disposed on a portion of the inner surface of the opening part excluding the first compression region and the second compression region.

Description

Cylindrical non-aqueous electrolyte secondary battery

[0001] The present disclosure relates to a cylindrical non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery in which corrosion of an outer can is suppressed.

[0002] In a cylindrical non-aqueous electrolyte secondary battery, an electrode assembly and a non-aqueous electrolyte are housed in a cylindrical outer can with a bottom, and a sealing member is crimped and fixed between a grooved portion and an open end of the outer can via a gasket, thereby sealing the interior. Patent Document 1 discloses a technique in which methoxyoligoethyleneoxypolyphosphazene, which absorbs and captures the non-aqueous electrolyte, is disposed on the surface of the gasket to suppress moisture penetration of the non-aqueous electrolyte to the outside of the battery.

[0003] Japanese Patent Application Laid-Open No. 2001-332231

[0004] During battery manufacturing, the non-aqueous electrolyte injected into the outer can may remain attached to the opening of the outer can. If the non-aqueous electrolyte remains at the open edge of the outer can, which is the tip of the opening, the non-aqueous electrolyte may react with moisture in the air to generate hydrofluoric acid, which may corrode the open edge. The thoxyoligoethyleneoxypolyphosphazene described in Patent Document 1 is arranged up to the open edge that comes into contact with the outside air, and there is a risk that the open edge will corrode due to the non-aqueous electrolyte absorbed by the thoxyoligoethyleneoxypolyphosphazene. Therefore, the technology disclosed in Patent Document 1 still needs further study.

[0005] Therefore, an object of the present disclosure is to provide a secondary battery in which corrosion of the open end of the outer can is suppressed.

[0006] A nonaqueous electrolyte secondary battery according to one aspect of the present disclosure includes a cylindrical, bottomed outer can having a grooved opening, an electrode assembly and a nonaqueous electrolyte solution housed in the outer can, and a sealing body that is crimped and fixed between the grooved opening and the open edge of the outer can via a gasket, wherein the inner surface of the opening has a first compression region that compresses the gasket from the open edge side and a second compression region that compresses the gasket from the grooved opening side, and an absorbent that absorbs the nonaqueous electrolyte solution is disposed in the area of ​​the inner surface of the opening excluding the first compression region and the second compression region.

[0007] According to the nonaqueous electrolyte secondary battery according to the present disclosure, corrosion of the open end of the outer can can be suppressed.

[0008] 1 is a longitudinal cross-sectional view of a cylindrical nonaqueous electrolyte secondary battery according to an embodiment of the present invention;

[0009] An example of an embodiment of a cylindrical secondary battery according to the present disclosure will be described in detail below with reference to the drawings. In the following description, specific shapes, materials, numerical values, directions, etc. are examples for facilitating understanding of the present invention and can be appropriately changed according to the specifications of the cylindrical secondary battery. Furthermore, when multiple embodiments and variations are included in the following description, it is assumed from the outset that the characteristic features of these embodiments and variations can be appropriately combined and used.

[0010] Fig. 1 is a longitudinal cross-sectional view of a secondary battery 10 according to an embodiment. In the secondary battery 10 shown in Fig. 1, an electrode assembly 14 and a nonaqueous electrolyte (not shown) are housed in an outer can 15. For ease of explanation, the following description will be given with the sealing body 16 side referred to as "top" and the bottom side of the outer can 15 referred to as "bottom."

[0011] The electrode assembly 14 has a wound structure in which a positive electrode 11 and a negative electrode 12 are wound with a separator 13 interposed therebetween. The positive electrode 11 has a strip-shaped positive electrode current collector and positive electrode mixture layers formed on both sides of the positive electrode current collector. The positive electrode current collector may be, for example, a foil of a metal such as aluminum, or a film with the metal disposed on its surface.

[0012] The positive electrode mixture layer is produced by applying a positive electrode mixture slurry containing, for example, a positive electrode active material, a conductive agent, a binder, and a solvent such as N-methyl-2-pyrrolidone (NMP) to both sides of a positive electrode current collector, followed by drying and compression. Examples of the positive electrode active material include lithium transition metal composite oxides containing transition metal elements such as Co, Mn, and Ni. Examples of the conductive agent include carbon materials such as carbon black (CB), acetylene black (AB), ketjen black, and graphite. Examples of the binder include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide (PI), acrylic resins, and polyolefin resins.

[0013] The negative electrode 12 includes a strip-shaped negative electrode current collector and a negative electrode mixture layer formed on both sides of the negative electrode current collector. Examples of the negative electrode current collector include a foil of a metal such as copper, and a film having such a metal disposed on its surface.

[0014] The negative electrode mixture layer is produced, for example, by applying a negative electrode mixture slurry containing a negative electrode active material, a binder, water, etc. to both sides of a negative electrode current collector, followed by drying and compression. Examples of the negative electrode active material include carbon materials such as natural graphite and artificial graphite, metals that alloy with lithium such as Si and Sn, or alloys and oxides containing these. Examples of the binder include styrene-butadiene rubber (SBR), CMC or a salt thereof, polyacrylic acid or a salt thereof, polyvinyl alcohol, etc.

[0015] A porous sheet having ion permeability and insulating properties is used as the separator 13. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. The separator is preferably made of an olefin resin such as polyethylene or polypropylene.

[0016] As the nonaqueous solvent (organic solvent) of the nonaqueous electrolyte solution contained in the outer can 15, carbonates, lactones, ethers, ketones, esters, etc. can be used, and two or more of these solvents can be mixed and used. When two or more solvents are mixed and used, it is preferable to use a mixed solvent containing a cyclic carbonate and a chain carbonate. For example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. can be used as the cyclic carbonate, and dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), etc. can be used as the chain carbonate. As the electrolyte salt of the nonaqueous electrolyte solution, LiPF ６ , LiBF ４ , LiCF ３ SO ３ The amount of electrolyte salt dissolved in the non-aqueous solvent can be, for example, 0.5 to 2.0 mol / L.

[0017] The opening of the outer can 15 is closed with the sealing body 16, thereby sealing the interior of the secondary battery 10. Insulating plates 17, 18 are provided above and below the electrode body 14. The positive electrode lead 19 extends upward through a through hole in the insulating plate 17 and is welded to the underside of a filter 22, which is the bottom plate of the sealing body 16. In the secondary battery 10, a cap 26, which is the top plate of the sealing body 16 and is electrically connected to the filter 22, serves as the positive electrode terminal. On the other hand, the negative electrode lead 20 extends toward the bottom of the outer can 15 through a through hole in the insulating plate 18 and is welded to the inner bottom surface of the outer can 15. In the secondary battery 10, the outer can 15 serves as the negative electrode terminal.

[0018] The exterior can 15 is made of metal and has a cylindrical shape with a bottom, and has a grooved portion 21 at the opening 15a. As will be described later, the grooved portion 21 supports the sealing body 16 on its upper surface. The portion of the exterior can 15 below the grooved portion 21 contains the electrode assembly 14 and non-aqueous electrolyte. The grooved portion 21 is preferably present in an annular shape along the circumferential direction of the exterior can 15. The grooved portion 21 can be formed, for example, by pressing the side portion of the exterior can 15 from the outside.

[0019] The sealing body 16 includes a filter 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26, which are stacked in this order from the electrode body 14 side. Each component of the sealing body 16 has, for example, a disk or ring shape, 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, with the insulating member 24 interposed between their respective peripheral edges. If the internal pressure of the battery increases due to abnormal heat generation, for example, the lower valve body 23 may break, causing the upper valve body 25 to swell toward the cap 26 and separate from the lower valve body 23, thereby cutting off the electrical connection between them. If the internal pressure continues to increase, the upper valve body 25 may break, allowing gas to be released through the opening 26a in the cap 26.

[0020] Next, the sealed state of the opening 15a of the secondary battery 10 and the absorbent 40 will be described with reference to Fig. 2. Fig. 2 is an enlarged view of the vicinity of the opening 15a of the outer can 15.

[0021] The sealing body 16 is fixed by crimping between the grooved portion 21 and the open edge 15b at the opening 15a of the outer can 15. That is, the sealing body 16 is compressed and fixed between the grooved portion 21 and the open edge 15b, which is the upper end of the inwardly bent outer can 15, via a gasket 27. The gasket 27 is a flexible insulating member that electrically isolates the sealing body 16, which serves as the positive terminal, from the outer can 15, which serves as the negative terminal, while being compressed in the vertical direction to ensure the internal sealing of the secondary battery 10. The material of the gasket 27 is not particularly limited as long as it is a compressible insulating material, and examples of suitable materials that can be used include polypropylene (PP), polyphenylene sulfide (PPS), polyethylene (PE), polybutylene terephthalate (PBT), perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE), and polyamide (PA).

[0022] The sealing body 16 is crimped from above and below between the grooved portion 21 and the opening edge 15b. Therefore, as shown in FIG. 2 , the inner surface of the opening 15a has a first compression region 30 compressing the gasket 27 from the opening edge 15b side and a second compression region 32 compressing the gasket 27 from the grooved portion 21 side. In the example shown in FIG. 2 , the upper surface of the grooved portion 21 and the periphery of the opening edge 15b are substantially parallel to the main surface of the sealing body 16, and the first compression region 30 and the second compression region 32 are formed in a portion of the inner surface of the outer can 15 that is substantially parallel to the main surface of the sealing body 16. Note that the configuration of the first compression region 30 and the second compression region 32 is not limited to the example shown in FIG. 2 . For example, if the opening edge 15b is compressed so that it sinks, the first compression region 30 will be formed only near the opening edge 15b, which is narrower than the example shown in FIG. 2 .

[0023] An absorbent 40 that absorbs the nonaqueous electrolyte is disposed on the inner surface of the opening 15a excluding the first compression region 30 and the second compression region 32. The absorbent 40 absorbs the nonaqueous electrolyte remaining in the opening 15a of the outer can 15 during injection, thereby suppressing corrosion of the open edge 15b of the outer can 15. Furthermore, by not disposing the absorbent 40 in the first compression region 30 and the second compression region 32, the airtightness of the battery can be ensured.

[0024] As shown in Fig. 2, the absorbent 40 is preferably disposed closer to the electrode body 14 than the second compression region 32. This allows a sufficient amount of absorbent to be disposed on the inner surface of the outer can 15 to absorb the remaining non-aqueous electrolyte. The position at which the absorbent 40 is disposed is not limited to the example shown in Fig. 2. For example, the absorbent 40 may be disposed between the first compression region 30 and the second compression region 32.

[0025] 2, the end 40a of the absorbent 40 on the open end 15b side is disposed spaced apart from the end a of the second compression region 32 on the electrode body 14 side, but this is not limiting. For example, the end 40a of the absorbent 40 may be in contact with the end a of the second compression region 32.

[0026] An end 40a of the absorbent 40 on the open end 15b side is preferably positioned closer to the open end 15b than the tip 21T of the grooved portion 21 so as to easily absorb the remaining non-aqueous electrolyte.

[0027] The end 40b of the absorbent 40 on the electrode body 14 side is preferably arranged closer to the opening end 15b than the electrode body 14, and more preferably closer to the opening end 15b than the insulating plate 17. In other words, the end 40b of the absorbent 40 is preferably arranged above the nonaqueous electrolyte filled in the lower part of the outer can 15.

[0028] In the longitudinal cross section of the nonaqueous electrolyte secondary battery, the length L of the absorbent 40 is, for example, 30% or more of the depth D of the grooved portion 21 from the outermost periphery of the opening 15a. This allows a sufficient amount of absorbent to be disposed on the inner surface of the outer can 15 to absorb the remaining nonaqueous electrolyte. The length L of the absorbent 40 is, for example, 300% or less of the depth D of the grooved portion 21.

[0029] The absorbent 40 is preferably disposed continuously in the circumferential direction of the outer can 15. This allows the absorbent 40 to absorb the remaining nonaqueous electrolyte no matter where the nonaqueous electrolyte remains in the circumferential direction of the outer can 15.

[0030] The material of the absorbent 40 is not particularly limited as long as it absorbs the non-aqueous electrolyte. The absorbent 40, for example, absorbs the non-aqueous electrolyte and swells. The material of the absorbent 40 is, for example, one or more resins selected from the group consisting of polyurethane resin, polystyrene resin, fluororesin, and polyether resin. An example of the fluororesin is PVDF, and an example of the polyether resin is hydroxyoligoethyleneoxypolyphosphazene.

[0031] In the nonaqueous electrolyte secondary battery 10, the method for disposing the absorbent 40 on the inner surface of the exterior can 15 as described above is not particularly limited, and for example, the absorbent 40 in film form is disposed at a predetermined position by applying the absorbent 40 to the inner surface of the exterior can 15. During the manufacture of the nonaqueous electrolyte secondary battery 10, the absorbent 40 is disposed at a predetermined position, for example, before the opening 15a of the exterior can 15 is pressed to form the grooved portion 21. This makes it possible to easily dispose the absorbent 40 closer to the electrode body 14 than the tip T of the grooved portion 21.

[0032] The opening 15a of the outer can 15 may be provided with components other than the sealing body 16, the gasket 27, and the absorbent 40. For example, a sealant may be provided between the outer can 15 and the gasket 27. As the sealant, conventionally used rubber polymers such as 1,2-polybutadiene, pitch, asphalt, etc. may be used.

[0033] As described above, in the nonaqueous electrolyte secondary battery of the present disclosure, the absorbent absorbs the electrolyte remaining in the opening of the outer can, thereby making it possible to suppress corrosion due to the generation of hydrofluoric acid at the open end of the outer can.

[0034] The present disclosure is further described by the following embodiments. Aspect 1: A cylindrical nonaqueous electrolyte secondary battery comprising: a cylindrical outer can with a bottom and a grooved opening; an electrode assembly and a nonaqueous electrolyte solution housed in the outer can; and a sealing body crimped and fixed between the grooved opening and an open end of the outer can via a gasket, wherein the inner surface of the open end has a first compressed region compressing the gasket from the open end side and a second compressed region compressing the gasket from the grooved opening side; and an absorbent material for absorbing the nonaqueous electrolyte solution disposed on the inner surface of the open end excluding the first compressed region and the second compressed region. Aspect 2: The cylindrical nonaqueous electrolyte secondary battery according to Aspect 1, wherein the absorbent material is disposed closer to the electrode assembly than the second compressed region. Aspect 3: The cylindrical nonaqueous electrolyte secondary battery according to Aspect 1 or Aspect 2, wherein, in a longitudinal cross section, the length L of the absorbent material is 30% or more of the depth D of the grooved portion from the outermost periphery of the open end. Configuration 4: The cylindrical nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 3, wherein the absorbent is disposed continuously in the circumferential direction of the outer can. Configuration 5: The cylindrical nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 4, wherein the absorbent is one or more resins selected from the group consisting of polyurethane resin, polystyrene resin, fluororesin, and polyether resin.

[0035] REFERENCE SIGNS LIST 10 secondary battery, 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 15 outer can, 15a opening, 15b opening edge, 16 sealing body, 17, 18 insulating plate, 19 positive electrode lead, 20 negative electrode lead, 21 grooved portion, 22 filter, 23 lower valve body, 24 insulating member, 25 upper valve body, 26 cap, 26a opening hole, 27 gasket, 30 first compression region, 32 second compression region, 40 absorbent

Claims

1. A cylindrical nonaqueous electrolyte secondary battery comprising: a cylindrical exterior can with a bottom and a grooved portion at an opening; an electrode assembly and nonaqueous electrolyte housed in the exterior can; and a sealing body that is crimped and fixed between the grooved portion and an open end of the exterior can via a gasket, wherein on the inner surface of the opening, there is a first compressed region that compresses the gasket from the open end side and a second compressed region that compresses the gasket from the grooved portion side, and an absorbent that absorbs the nonaqueous electrolyte is disposed on the inner surface of the opening excluding the first compressed region and the second compressed region.

2. The cylindrical nonaqueous electrolyte secondary battery according to claim 1, wherein the absorbent is disposed on the electrode body side relative to the second compression region.

3. The cylindrical nonaqueous electrolyte secondary battery according to claim 1, wherein in a longitudinal cross section, the length L of said absorbent is 30% or more of the depth D of said grooved portion from the outermost periphery of said opening.

4. The cylindrical nonaqueous electrolyte secondary battery according to claim 1, wherein the absorbent is disposed continuously in the circumferential direction of the outer can.

5. The cylindrical nonaqueous electrolyte secondary battery according to claim 1, wherein the absorbent is one or more resins selected from the group consisting of polyurethane resins, polystyrene resins, fluororesins, and polyether resins.

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