Non-aqueous electrolyte secondary battery

Abstract

Provided is a non-aqueous electrolyte secondary battery comprising: a closed-bottom cylindrical outer can (20) that accommodates an electrode body and a non-aqueous electrolyte; a sealing body (30) that closes an opening part (24) of the outer can (20); a gasket (40) that is disposed between the outer can (20) and the sealing body (30); and a protective layer (50) that includes a thermosetting resin. The non-aqueous electrolyte secondary battery is characterized in that: an opening end of the outer can (20) is provided with a crimping part (26) that extends radially inward and crimps and fixes the sealing body (30); the gasket (40) has an extension part (41) that extends radially inward from between the sealing body (30) and an inner end (26A) in the radial direction of the crimping part (26); and the protective layer (50) covers an inner end (40A) in the radial direction of the extension part (41).

Description

Nonaqueous electrolyte secondary battery

[0001] The present disclosure relates to a non-aqueous electrolyte secondary battery.

[0002] Non-aqueous electrolyte secondary batteries have been known that include a cylindrical outer can with a bottom that houses an electrode assembly and a non-aqueous electrolyte, and a sealing member that closes the opening of the outer can. Non-aqueous electrolyte secondary batteries seal the interior by crimping the sealing member between an annular groove formed in the side surface of the outer can and the open edge of the outer can. Patent Document 1 discloses a non-aqueous electrolyte secondary battery in which a ring member made of an elastic material is disposed on the outside of the sealing member to improve the ability to exhaust gas from inside the battery.

[0003] Japanese Patent Application Laid-Open No. 2006-128010

[0004] However, in non-aqueous electrolyte secondary batteries, there is a possibility that the non-aqueous electrolyte inside the outer can may leak out of the battery due to an external impact, etc. If the non-aqueous electrolyte leaks, the non-aqueous electrolyte may straddle the positive electrode and the negative electrode, causing side reactions, which may result in corrosion of the outer can, a short circuit, etc.

[0005] A nonaqueous electrolyte secondary battery according to one aspect of the present disclosure is a nonaqueous electrolyte secondary battery comprising: an electrode assembly having a positive electrode and a negative electrode; a nonaqueous electrolyte; a cylindrical outer can with a bottom that houses the electrode assembly and the nonaqueous electrolyte; a sealing body that closes the opening of the outer can; a gasket that is disposed between the outer can and the sealing body; and a protective layer that contains a thermosetting resin, wherein the open end of the outer can is provided with a crimping portion that extends radially inward and crimps and fixes the sealing body, the gasket has an extending portion that extends radially inward from between the radially inner end of the crimping portion and the sealing body, and the protective layer covers the radially inner end of the extending portion.

[0006] According to the nonaqueous electrolyte secondary battery of one aspect of the present disclosure, it is possible to prevent the nonaqueous electrolyte inside the outer can from leaking out of the battery.

[0007] Fig. 1 is an axial cross-sectional view of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention. Fig. 2 is an enlarged view of the vicinity of a sealing body in Fig. 1. Fig. 3 is a view corresponding to Fig. 2 of a nonaqueous electrolyte secondary battery according to another embodiment of the present invention.

[0008] Hereinafter, an example of an embodiment of a nonaqueous electrolyte secondary battery according to the present disclosure will be described in detail with reference to the drawings. The embodiment described below is merely an example, and the present disclosure is not limited to the following embodiment. Furthermore, the present disclosure also includes embodiments obtained by selectively combining the components of the embodiments described below.

[0009] Fig. 1 is an axial cross-sectional view of a nonaqueous electrolyte secondary battery 10 according to an embodiment. As shown in Fig. 1 , the nonaqueous electrolyte secondary battery 10 includes an electrode assembly 14, a nonaqueous electrolyte (not shown), a cylindrical outer can 20 with a bottom that houses the electrode assembly 14 and the nonaqueous electrolyte, a sealing body 30 that closes an opening 24 of the outer can 20, and a gasket 40 that is disposed between the outer can 20 and the sealing body 30. Hereinafter, the side of the sealing body 30 in the axial direction (height direction) of the nonaqueous electrolyte secondary battery 10 will be referred to as "upper," and the side of the bottom 21 of the outer can 20 in the axial direction will be referred to as "lower."

[0010] The electrode assembly 14 includes a positive electrode 11, a negative electrode 12, and a separator 13, and has a structure in which the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 interposed therebetween. The positive electrode 11, the negative electrode 12, and the separator 13 are all long, strip-like bodies that are spirally wound and alternately stacked in the radial direction of the electrode assembly 14. Generally, the negative electrode 12 is formed to be slightly larger than the positive electrode 11 to prevent lithium deposition. That is, the negative electrode 12 is formed to be longer in the longitudinal direction and width direction (short direction) than the positive electrode 11. The separator 13 is formed to be at least slightly larger than the positive electrode 11, and two separators 13 are arranged to sandwich the positive electrode 11. The nonaqueous electrolyte secondary battery 10 includes insulating plates 16 and 17 arranged above and below the electrode assembly 14, respectively.

[0011] The positive electrode 11 has a positive electrode core and a positive electrode mixture layer formed on the positive electrode core. The positive electrode core can be a foil of a metal, such as aluminum or an aluminum alloy, that is stable within the potential range of the positive electrode 11, or a film with such a metal disposed on the surface. The positive electrode mixture layer contains a positive electrode active material, a conductive agent, and a binder, and is preferably formed on both sides of the positive electrode core except for the exposed portion of the positive electrode core to which the positive electrode lead 18 is welded. 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, a binder, etc. to 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.

[0012] The positive electrode mixture layer contains particulate lithium metal composite oxide as a positive electrode active material. The lithium metal composite oxide is a composite oxide containing metal elements such as Co, Mn, Ni, and Al in addition to Li. The metal element constituting the lithium metal composite oxide is, for example, at least one selected from Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Sn, Sb, W, Pb, and Bi. Among them, it is preferable to contain at least one selected from Co, Ni, and Mn. Examples of suitable composite oxides include lithium metal composite oxides containing Ni, Co, and Mn, and lithium metal composite oxides containing Ni, Co, and Al.

[0013] Examples of conductive agents contained in the positive electrode mixture layer include carbon black such as acetylene black and ketjen black, graphite, carbon nanotubes (CNT), carbon nanofibers, graphene, and other carbon materials. Examples of binders contained in the positive electrode mixture layer include fluorine-containing resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide, acrylic resin, polyolefin, and the like. These resins may also be used in combination with carboxymethyl cellulose (CMC) or a salt thereof, polyethylene oxide (PEO), and the like.

[0014] The negative electrode 12 has a negative electrode core and a negative electrode mixture layer formed on the negative electrode core. The negative electrode core can be a foil of a metal, such as copper or a copper alloy, that is stable within the potential range of the negative electrode 12, or a film with such a metal disposed on the surface. The negative electrode mixture layer contains a negative electrode active material, a binder, and, if necessary, a conductive agent, and is preferably formed on both sides of the negative electrode core except for the exposed portion of the negative electrode core to which the negative electrode lead 19 is welded. The negative electrode 12 can be produced by applying a negative electrode mixture slurry containing a negative electrode active material and a binder to the surface of 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.

[0015] The negative electrode mixture layer generally contains, as the negative electrode active material, a carbon material that reversibly absorbs and releases lithium ions. Suitable examples of the carbon material include natural graphite such as flake graphite, lump graphite, and amorphous graphite, and artificial graphite such as lump artificial graphite (MAG) and graphitized mesophase carbon microbeads (MCMB). Furthermore, as the negative electrode active material, a material containing at least one of an element that alloys with Li, such as Si or Sn, and a material containing such an element may be used. Among these, a composite material containing Si is preferred.

[0016] A suitable example of a composite material containing Si is SiO ２ Examples of such composite materials include a material in which Si fine particles are dispersed in a silicate phase such as lithium silicate, or a material in which Si fine particles are dispersed in an amorphous carbon phase. A conductive layer such as a carbon coating is formed on the particle surfaces of the composite material.

[0017] As in the case of the positive electrode mixture layer, the binder contained in the negative electrode mixture layer can be a fluorine-containing resin, PAN, polyimide, acrylic resin, polyolefin, or the like, but styrene-butadiene rubber (SBR) is preferably used. 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. Among these, it is preferable to use SBR in combination with CMC or a salt thereof, PAA or a salt thereof, or the like. The negative electrode mixture layer may contain a conductive agent such as CNT.

[0018] The separator 13 is a porous sheet having ion permeability and insulating properties. 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. A highly heat-resistant resin layer such as an aramid resin may be formed on the surface of the separator 13. A filler layer containing an inorganic filler may be formed at the interface between the separator 13 and at least one of the positive electrode 11 and the negative electrode 12.

[0019] A positive electrode lead 18 is connected to the positive electrode 11, and a negative electrode lead 19 is connected to the winding end side of the negative electrode 12. The positive electrode lead 18 passes through a through hole in the insulating plate 16 and extends toward the sealing body 30, and the negative electrode lead 19 passes outside the insulating plate 17 and extends toward the bottom 21 of the outer can 20. The positive electrode lead 18 is connected to the underside of the terminal plate 31 of the sealing body 30 by welding or the like, and the sealing body 30 serves as a positive electrode terminal. The negative electrode lead 19 is connected to the inner surface of the bottom 21 of the metal outer can 20 by welding or the like, and the outer can 20 serves as a negative electrode terminal.

[0020] The nonaqueous solvent (organic solvent) for the nonaqueous electrolyte contained in the outer can 20 can be carbonates, lactones, ethers, ketones, esters, etc., and two or more of these solvents can be mixed. When two or more solvents are mixed, 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. The electrolyte salt for the nonaqueous electrolyte can be LiPF ６ , LiBF ４ , LiCF ３ SO ３The amount of electrolyte salt dissolved in the non-aqueous solvent can be, for example, 0.5 mol / L or more and 2.0 mol / L or less.

[0021] As described above, the exterior can 20 is a cylindrical metal container with a bottom that is open on one axial side. The exterior can 20 has a bottom 21 and a side surface 22 that forms the side surface of the nonaqueous electrolyte secondary battery 10. The side surface 22 is the portion of the exterior can 20 excluding the bottom 21, and includes a grooved portion 23 and an opening 24, which will be described later.

[0022] The grooved portion 23 is a portion of the side surface portion 22 recessed radially inward, and is provided in an annular shape along the circumferential direction of the outer can 20. The upper surface of the grooved portion 23 supports the sealing body 30. The grooved portion 23 can be formed, for example, by spinning a portion of the side surface portion 22 radially inward to recess it in an annular shape radially inward.

[0023] The opening 24 is a region of the side surface portion 22 above the grooved portion 23 and forms an opening in the outer can 20. The opening 24 is bent radially inward when the sealing body 30 is crimped to the outer can 20. As a result, the opening 24 is formed with an opening side surface portion 25 that forms a portion of the side surface of the nonaqueous electrolyte secondary battery 10 and covers the outer peripheral surface of the gasket 40, and a crimped portion 26 that forms a portion of the upper surface of the nonaqueous electrolyte secondary battery 10 and extends radially inward. Furthermore, a portion of the gasket 40 is disposed radially inward relative to a radially inner end 26A of the crimped portion 26 (see FIG. 2 ). In other words, a portion of the upper surface of the gasket 40 is not covered by the crimped portion 26. As will be described in detail later, the tip side of the region of the gasket 40 that is not covered by the crimped portion 26 is covered with a protective layer 50 containing a thermosetting resin.

[0024] The opening 24 of the outer can 20 is closed by a sealing body 30. In this embodiment, the sealing body 30 is composed of a terminal plate 31 to which the positive electrode lead 18 is joined, and a sealing plate 32 that covers the terminal plate 31. The sealing body 30 is fixed to the opening 24 of the outer can 20 by crimping via a gasket 40. Note that the configuration of the sealing body 30 is not limited to this, as long as it is capable of closing the opening 24 of the outer can 20.

[0025] Terminal plate 31 is a metal plate-like member having a recessed portion on the lower side. Positive electrode lead 18 is joined to the lower surface of the recessed portion. In the example shown in Fig. 1 , the outer periphery of terminal plate 31 abuts against the outer periphery of sealing plate 32 and is fixed by crimping to opening 24 of outer can 20 via gasket 40. Alternatively, the outer periphery of terminal plate 31 may be joined to sealing plate 32 by laser welding or the like.

[0026] The sealing plate 32 is a metal plate-like member having no through holes. A protrusion 33 that protrudes toward the outside of the battery is provided in the radial center of the sealing plate 32. In other words, the sealing body 30 has the protrusion 33 provided in the radial center. The protrusion 33 has, for example, a substantially circular shape when viewed from above, and has an outer diameter that is 10% to 80% of the outer diameter of the sealing plate 32. The height of the protrusion 33 is, for example, 0.5 mm to 10 mm, and may be 1 mm to 5 mm. Note that the sealing plate 32 does not necessarily have to have the protrusion 33.

[0027] Next, the gasket 40 and the protective layer 50 will be described in detail with reference to Fig. 2. Fig. 2 is an enlarged view of the vicinity of the sealing body 30 in Fig. 1 .

[0028] 2 , the gasket 40 is disposed between the outer can 20 and the sealing body 30. By providing the gasket 40, the gap between the outer can 20 and the sealing body 30 is sealed, improving the airtightness of the interior of the nonaqueous electrolyte secondary battery 10. In other words, the gasket 40 is required to seal the gap between the outer can 20 and the sealing body 30.

[0029] The gasket 40 is made of a resin material. Examples of the resin material that can be used to make the gasket 40 include polyolefin resins such as polypropylene (PP), fluorinated resins such as tetrafluoroethylene-perfluoroalkoxyethylene copolymers (PFA), and polyphenylene sulfide (PPS). Making the gasket 40 out of a resin material makes it easy to ensure insulation between the outer can 20 and the sealing body 30 while sealing the gap between the outer can 20 and the sealing body 30.

[0030] The gasket 40 has an extension portion 41 that extends radially inward from between the radially inner end 26A of the crimped portion 26 and the sealing body 30 (sealing plate 32). In other words, the extension portion 41 is a portion of the gasket 40 that is located radially inward of the radially inner end 26A of the crimped portion 26, and is formed in an annular shape. The length of the extension portion 41 in the radial direction of the outer can 20 can be set appropriately depending on the outer diameter of the nonaqueous electrolyte secondary battery 10, etc., but may be, for example, 0.1 mm or more and 10 mm or less, or 0.5 mm or more and 5 mm or less.

[0031] As shown in FIG. 2 , the radially inner end 40A of the extension portion 41 is covered with a protective layer 50 containing a thermosetting resin. Covering the radially inner end 40A of the extension portion 41 with the protective layer 50 can prevent nonaqueous electrolyte from leaking out of the battery through a gap between the sealing body 30 and the gasket 40. In particular, the thermosetting resin easily penetrates into the gap between the sealing body 30 and the gasket 40, thereby filling the gap and improving the sealing performance of the battery. As a result, nonaqueous electrolyte can be prevented from leaking out of the battery through the gap between the sealing body 30 and the gasket 40. Furthermore, thermosetting resins have high heat resistance and mechanical strength and excellent shape stability. As a result, even when the battery is subjected to an external impact, nonaqueous electrolyte can be prevented from leaking out of the battery through the gap between the sealing body 30 and the gasket 40.

[0032] It is preferable that the protective layer 50 covers the entire circumference of the radially inner end 40A of the extension portion 41. In other words, it is preferable that the protective layer 50 is formed in an annular shape. In this case, the gap between the sealing body 30 and the gasket 40 can be more effectively filled, thereby further preventing the non-aqueous electrolyte from leaking out of the battery through the gap between the sealing body 30 and the gasket 40.

[0033] The thickness of the protective layer 50 is not particularly limited as long as it can cover the radial inner end 40A of the extension portion 41, but may be, for example, 0.3 mm or more and 10 mm or less, or 0.5 mm or more and 5 mm or less.

[0034] The thermosetting resin contained in the protective layer 50 is, for example, at least one selected from the group consisting of epoxy resin, urethane resin, silicone resin, and thermosetting acrylic resin, and among these, epoxy resin is preferable. The protective layer 50 may also contain a curing agent, a filler, or the like.

[0035] The protective layer 50 can be formed, for example, by crimping and fixing the sealing body 30 between the grooved portion 23 and the opening 24 of the outer can 20 via the gasket 40, applying a thermosetting resin to the radially inner end 40A of the extending portion 41 of the gasket 40, and heat-treating the thermosetting resin. The conditions for the heat treatment are not particularly limited as long as they do not melt the gasket 40, and may be adjusted appropriately depending on the properties of the thermosetting resin used. Furthermore, if the protective layer 50 contains a curing agent or depending on the properties of the thermosetting resin, the thermosetting resin may be cured by leaving it at room temperature without heat treatment, thereby forming the protective layer 50.

[0036] Next, a modified example of the nonaqueous electrolyte secondary battery according to one aspect of the present disclosure will be described with reference to Fig. 3 and Fig. 4. Fig. 3 and Fig. 4 are views corresponding to Fig. 2 of a nonaqueous electrolyte secondary battery 10 according to another embodiment.

[0037] 3 , the protective layer 50 may cover a region of the outer surface of the sealing body 30 (sealing plate 32) that is not covered by the gasket 40 and is radially outward of the protrusion 33. In other words, the region of the outer surface of the sealing plate 32 between the protrusion 33 and the gasket 40 may be covered with the protective layer 50. In this case, only the protrusion 33 is exposed on the sealing plate 32, which allows for a longer distance between the crimped portion 26 of the outer can 20, which serves as the negative electrode terminal, and the exposed region of the sealing plate 32, which serves as the positive electrode terminal. As a result, even if the non-aqueous electrolyte leaks and metal precipitates, or if conductive foreign matter or the like adheres, current flow can be suppressed.

[0038] 4 , the protective layer 50 may cover the radially inner end 26A of the crimped portion 26 in addition to the extending portion 41 of the gasket 40. Covering the radially inner end 26A of the crimped portion 26 with the protective layer 50 can prevent the nonaqueous electrolyte from leaking to the outside of the battery through the gap between the outer can 20 and the gasket 40. As a result, a nonaqueous electrolyte secondary battery 10 with higher reliability can be provided.

[0039] The present disclosure is further described by the following embodiments. Aspect 1: A non-aqueous electrolyte secondary battery comprising: an electrode assembly having a positive electrode and a negative electrode, a non-aqueous electrolyte, a cylindrical outer can with a bottom that houses the electrode assembly and the non-aqueous electrolyte, a sealing body that closes an opening of the outer can, a gasket that is disposed between the outer can and the sealing body, and a protective layer that contains a thermosetting resin, wherein a crimped portion that extends radially inward and crimps and fixes the sealing body at an open end of the outer can, the gasket has an extension that extends radially inward from between a radially inner end of the crimped portion and the sealing body, and the protective layer covers the radially inner end of the extension. Aspect 2: The non-aqueous electrolyte secondary battery according to Aspect 1, wherein the sealing body has a protrusion that is provided in a radial center portion, and a region of the outer surface of the sealing body that is not covered by the gasket and is radially outward of the protrusion is covered by the protective layer. Configuration 3: The nonaqueous electrolyte secondary battery according to Configuration 1 or 2, wherein the protective layer covers a radially inner end of the crimped portion. Configuration 4: The nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 3, wherein the thermosetting resin is at least one selected from the group consisting of an epoxy resin, a urethane resin, a silicone resin, and a thermosetting acrylic resin.

[0040] REFERENCE SIGNS LIST 10 non-aqueous electrolyte secondary battery, 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 16, 17 insulating plate, 18 positive electrode lead, 19 negative electrode lead, 20 outer can, 21 bottom, 22 side surface, 23 grooved portion, 24 opening, 25 opening side surface, 26 crimped portion, 26A radial inner end, 30 sealing body, 31 terminal plate, 32 sealing plate, 33 convex portion, 40 gasket, 40A radial inner end, 41 extension portion, 50 protective layer

Claims

1. A non-aqueous electrolyte secondary battery comprising: an electrode assembly having a positive electrode and a negative electrode; a non-aqueous electrolyte; a cylindrical outer can with a bottom that houses the electrode assembly and the non-aqueous electrolyte; a sealing body that closes an opening of the outer can; a gasket that is disposed between the outer can and the sealing body; and a protective layer that contains a thermosetting resin, wherein a crimping portion that extends radially inward at the open end of the outer can and crimps and fixes the sealing body, the gasket has an extending portion that extends radially inward from between the radially inner end of the crimping portion and the sealing body, and the protective layer covers the radially inner end of the extending portion.

2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the sealing body has a protrusion provided in a radial center portion, and an area of ​​the outer surface of the sealing body that is not covered by the gasket and is radially outward of the protrusion is covered by the protective layer.

3. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the protective layer covers the radially inner end of the crimped portion.

4. The nonaqueous electrolyte secondary battery according to claim 1, wherein the thermosetting resin is at least one selected from the group consisting of epoxy resin, urethane resin, silicone resin and thermosetting acrylic resin.

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