Non-aqueous electrolyte secondary battery

Abstract

This non-aqueous electrolyte secondary battery comprises: a bottomed cylindrical outer can (15); a non-aqueous electrolyte and an electrode body housed in the outer can (15); a sealing body (16) for closing an opening (15a) of the outer can (15); a gasket (27) disposed between the outer can (15) and the sealing body (16); and a sealing material (30) disposed between the outer can (15) and the gasket (27), the sealing material (30) having a layered structure in which a first sealing material layer (31) and a second sealing material layer (32) are arranged in said order from the outer can (15) side, the second sealing material layer (32) having oil repellency with respect to the non-aqueous electrolyte more than the first sealing material layer (31), the first sealing material layer (31) and / or the second sealing material layer (32) containing an alkaline compound.

Description

Nonaqueous electrolyte secondary battery

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

[0002] Conventionally, 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 solution, and a sealing body that closes the opening of the outer can. The non-aqueous electrolyte secondary battery seals the interior by crimping the sealing body between an annular groove formed in the side surface of the outer can and the open edge of the outer can.

[0003] During battery manufacturing, the nonaqueous electrolyte injected into the exterior can may remain attached to the opening of the exterior can. If the nonaqueous electrolyte remains in the area of ​​the opening of the exterior can where the sealing body is crimped, the nonaqueous electrolyte may react with moisture that has entered from the outside to generate hydrofluoric acid, which may corrode the exterior can. Patent Document 1 discloses a nonaqueous electrolyte secondary battery in which a sealant containing an alkaline compound added to neutralize the generated hydrofluoric acid is interposed between the exterior can and a gasket in order to suppress corrosion of the exterior can.

[0004] International Publication No. 2022 / 080175

[0005] As a result of investigations by the present inventors, it has become clear that with the technology disclosed in Patent Document 1, non-aqueous electrolyte may remain in the region of the opening of the outer can where the sealing body is crimped and fixed, which may cause corrosion of the outer can.

[0006] A nonaqueous electrolyte secondary battery according to one aspect of the present disclosure is a nonaqueous electrolyte secondary battery including a cylindrical outer can with a bottom, an electrode assembly and a nonaqueous electrolyte solution housed in the outer can, 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 sealing material that is disposed between the outer can and the gasket, wherein the sealing material has a laminated structure in which a first sealing material layer and a second sealing material layer are disposed in this order from the outer can side, the second sealing material layer has higher oil repellency with respect to the nonaqueous electrolyte solution than the first sealing material layer, and at least one of the first sealing material layer and the second sealing material layer contains an alkaline compound.

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

[0008] 1 is an axial cross-sectional view of a non-aqueous electrolyte secondary battery according to an embodiment of the present invention;

[0009] An example of an embodiment of a nonaqueous electrolyte 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 nonaqueous electrolyte secondary battery.

[0010] Fig. 1 is an axial cross-sectional view of a nonaqueous electrolyte secondary battery 10 according to an embodiment. The nonaqueous electrolyte secondary battery 10 shown in Fig. 1 includes an electrode assembly 14, a nonaqueous electrolyte solution (not shown), and an outer can 15 that accommodates the electrode assembly 14 and the nonaqueous electrolyte solution. The nonaqueous electrolyte secondary battery 10 also includes a sealing body 16 that closes an opening 15a of the outer can 15, a gasket 27 that is disposed between the outer can 15 and the sealing body 16, and a sealant 30 that is disposed between the outer can 15 and the gasket 27. For ease of explanation, the sealing body 16 side will be referred to as "top" and the bottom side of the outer can 15 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 its salts, polyacrylic acid or its salts, 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 13 is preferably made of an olefin resin such as polyethylene or polypropylene.

[0016] The nonaqueous solvent (organic solvent) of the nonaqueous electrolyte solution contained in the outer can 15 can be carbonates, lactones, ethers, ketones, esters, etc., 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. The electrolyte salt of the nonaqueous electrolyte solution can be 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 mol / L or more and 2.0 mol / L or less.

[0017] 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. As a result, 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 through a through-hole in the insulating plate 18 to the bottom side of the outer can 15 and is welded to the inner bottom surface of the outer can 15. As a result, 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. 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 formed 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 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 or the like, for example, the lower valve body 23 may rupture, causing the upper valve body 25 to bulge 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 rupture, allowing gas to be released through the opening 26a of the cap 26.

[0020] Next, the sealing state of the opening 15a of the nonaqueous electrolyte secondary battery 10 and the sealing material 30 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. Specifically, 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 outer can 15 bent radially inward, via an annular 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 ensuring the sealing of the interior of the outer can 15 by being compressed in the vertical direction. 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] A sealant 30 is provided between the outer can 15 and the gasket 27. The sealant 30 has the function of improving the airtightness of the interior of the outer can 15. In this embodiment, the sealant 30 is provided in a region between the outer can 15 and the gasket 27, from the opening edge 15b to the grooved portion 21. The arrangement of the sealant 30 is not limited thereto, as long as it is provided between the outer can 15 and the gasket 27. For example, the sealant 30 may be provided only between the outer can 15 and the side surface 27b and the bottom surface 27c of the gasket 27 and the outer can 15, and may not be provided between the top surface 27a of the gasket 27 and the outer can 15.

[0023] 2 , the sealing material 30 has a laminated structure in which a first sealing material layer 31 and a second sealing material layer 32 are arranged in this order from the outer can 15 side. That is, the first sealing material layer 31 abuts against the outer can 15, and the second sealing material layer 32 abuts against the gasket 27.

[0024] The first sealant layer 31 is composed of a rubber-based polymer, pitch, asphalt, or a vinyl-, silicone-, acrylic-, or urethane-based polymer. These may be used alone or in combination. To improve the sealing performance of the interior of the outer can 15, the first sealant layer 31 preferably has a higher elastic modulus than the second sealant layer 32. Examples of rubber-based polymers include butyl rubber, butadiene rubber, urethane rubber, silicone rubber, chloroprene rubber, and isoprene rubber. The first sealant layer 31 is particularly effective in improving the sealing performance of the interior of the outer can 15.

[0025] The second sealant layer 32 has higher oil repellency against the nonaqueous electrolyte than the first sealant layer 31. When the nonaqueous electrolyte is injected during fabrication of the nonaqueous electrolyte secondary battery 10, the second sealant layer 32 is exposed. Therefore, the second sealant layer 32 is a portion that is easily exposed to the nonaqueous electrolyte. Therefore, by making the oil repellency of the second sealant layer 32 against the nonaqueous electrolyte higher than that of the first sealant layer 31, the amount of nonaqueous electrolyte remaining on the surface of the second sealant layer 32 can be reduced. As a result, the amount of hydrofluoric acid generated by the reaction between the remaining nonaqueous electrolyte and moisture that has infiltrated through the opening edge 15b is reduced, thereby suppressing corrosion of the outer can 15. The oil repellency of the first sealant layer 31 and the second sealant layer 32 against the nonaqueous electrolyte can be determined by dropping a drop of nonaqueous electrolyte on the surface of each layer and measuring the contact angle. A larger contact angle indicates higher oil repellency.

[0026] The second sealant layer 32 is preferably made of a fluorine-based resin. Examples of fluorine-based resins include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroalkoxyalkane (PFA), perfluoroethylene propene copolymer (FEP), ethylene tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), and ethylene chlorotrifluoroethylene copolymer (ECTFE). These may be used alone or in combination of two or more. By making the second sealant layer 32 out of a fluorine-based resin, it becomes easier to improve oil repellency against non-aqueous electrolyte solutions.

[0027] The sealing material 30 can be produced by applying a first coating liquid that forms a first sealing material layer 31 to the inner surface of the exterior can 15, and then applying a second coating liquid that forms a second sealing material layer 32. The coating liquid is a mixture of compounds that form each layer in a solvent, and the solvent can be, for example, xylene, ethylbenzene, or toluene. After the first coating liquid or the second coating liquid is applied to the inner surface of the exterior can 15, a heat treatment may be performed to dry the coating liquid.

[0028] At least one of the first sealant layer 31 and the second sealant layer 32 contains an alkaline compound. This allows the alkaline compound to neutralize hydrofluoric acid even when hydrofluoric acid is generated by a reaction between the nonaqueous electrolyte solution that has permeated the sealant 30 and remained there and moisture that has entered through the opening edge 15b. As a result, corrosion of the exterior can 15 by hydrofluoric acid can be suppressed.

[0029] The alkaline compound preferably contains at least one selected from aluminum hydroxide, magnesium hydroxide, aluminum oxide, magnesium oxide, lithium carbonate, and sodium carbonate. The above compounds are unlikely to volatilize even during long-term storage, and therefore can inhibit corrosion of the exterior can 15 for a long period of time. This effect becomes more pronounced when the sealant 30 has the second sealant layer 32 with high oil repellency.

[0030] The content of the alkaline compound contained in the first sealant layer 31 or the second sealant layer 32 can be set appropriately depending on the size, shape, etc. of the opening 15a of the outer can 15. The content of the alkaline compound contained in the first sealant layer 31 or the second sealant layer 32 may be, for example, 3% by mass or more and 50% by mass or less, or 5% by mass or more and 30% by mass or less.

[0031] The content of the alkaline compound contained in the first sealant layer 31 may be greater than the content of the alkaline compound contained in the second sealant layer 32. In this case, it becomes easier to improve the oil repellency of the second sealant layer 32 against the non-aqueous electrolyte solution. The alkaline compound may be contained substantially only in the first sealant layer 31.

[0032] The thicknesses of the first sealant layer 31 and the second sealant layer 32 can be appropriately set depending on the size, shape, etc. of the opening 15a of the outer can 15. Generally, if the thicknesses of the first sealant layer 31 and the second sealant layer 32 are too small, the effect of improving the sealing of the interior of the outer can 15 is reduced. On the other hand, if the thicknesses of the first sealant layer 31 and the second sealant layer 32 are too large, the first sealant layer 31 and the second sealant layer 32 may be extruded to the outside from the sealing location during the crimping process, resulting in poor appearance. The thicknesses of the first sealant layer 31 and the second sealant layer 32 may be, for example, 0.5 μm or more and 50 μm or less, or 1 μm or more and 30 μm or less, respectively.

[0033] Furthermore, the thickness of the first sealant layer 31 may be greater than the thickness of the second sealant layer 32. As described above, the first sealant layer 31 particularly affects the improvement of the airtightness inside the outer can 15. Therefore, by making the thickness of the first sealant layer 31 greater than the thickness of the second sealant layer 32, it becomes easier to improve the airtightness inside the outer can 15.

[0034] The thicknesses of the first sealant layer 31 and the second sealant layer 32 can be adjusted by the application conditions of the coating liquids forming each layer and the amounts of compounds contained in the coating liquids. The mass ratio of the compound (e.g., rubber-based polymer) constituting the first sealant layer 31 to the mass of the first coating liquid forming the first sealant layer 31 is, for example, 0.5% by mass or more and 30% by mass or less, or may be 1.0% by mass or more and 25% by mass or less. The mass ratio of the compound (e.g., fluorine-based resin) constituting the second sealant layer 32 to the mass of the second coating liquid forming the second sealant layer 32 is, for example, 0.3% by mass or more and 20% by mass or less, or may be 0.5% by mass or more and 15% by mass or less.

[0035] Furthermore, on the inner surface of the exterior can 15, the area of ​​the region covered by the first seal material layer 31 may be larger than the area of ​​the region covered by the second seal material layer 32. In other words, a portion of the first seal material layer 31 may not be covered by the second seal material layer 32. In this case, it becomes easier to improve the airtightness of the interior of the exterior can 15.

[0036] Next, an example of a method for manufacturing a nonaqueous electrolyte secondary battery 10 will be described. First, insulating plates 17 and 18 are placed above and below the electrode assembly 14, and the electrode assembly 14 is housed in an outer can 15. Next, a negative electrode lead 20 is welded to the bottom of the outer can 15, and a groove 21 is formed in the opening 15a of the outer can 15 by pressing. A first coating liquid for forming a first sealing material layer 31 and a second coating liquid for forming a second sealing material layer 32 are then applied, in that order, to the region from the top surface of the groove 21 to the inner surface of the opening end 15b. An appropriate amount of nonaqueous electrolyte is then poured into the interior of the outer can 15, and a gasket 27 is placed above the groove 21. Next, a sealing body 16 is welded to the positive electrode lead 19, and the sealing body 16 is crimped and fixed between the opening end 15b and the groove 21 via the gasket 27, thereby completing the production of a nonaqueous electrolyte secondary battery 10.

[0037] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to these examples.

[0038] Examples 1 to 8 [Fabrication of Positive Electrode] LiCoO ２ Lithium cobalt oxide represented by the formula (I) was used. 100 parts by mass of this positive electrode active material was mixed with 1 part by mass of acetylene black (AB) as a conductive agent and 1 part by mass of polyvinylidene fluoride (PVDF) as a binder, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) was added to prepare a positive electrode mixture slurry. Next, this positive electrode mixture slurry was applied to both sides of a positive electrode current collector made of aluminum foil, dried, cut to a predetermined electrode size, and rolled using a roller to obtain a strip-shaped positive electrode. In addition, an exposed portion of the positive electrode current collector where the positive electrode mixture layer was not formed was formed in a portion of the positive electrode lengthwise, and an aluminum positive electrode lead was fixed to the exposed portion of the positive electrode current collector by ultrasonic welding.

[0039] [Preparation of Negative Electrode] Natural graphite was used as the negative electrode active material. 100 parts by mass of this negative electrode active material, 1 part by mass of styrene-butadiene rubber (SBR) as a binder, and 1 part by mass of carboxymethyl cellulose (CMC) as a thickener were mixed, and an appropriate amount of water was added to prepare a negative electrode mixture slurry. Next, this negative electrode mixture slurry was applied to both sides of a negative electrode current collector made of copper foil, dried, cut to a predetermined electrode size, and rolled using a roller to obtain a strip-shaped negative electrode. In addition, an exposed portion of the negative electrode current collector where no negative electrode mixture layer was formed was formed at one end in the longitudinal direction of the negative electrode, and a nickel negative electrode lead was fixed to the exposed portion of the negative electrode current collector by ultrasonic welding.

[0040] [Fabrication of Electrode Assembly] The fabricated positive and negative electrodes were spirally wound with a separator interposed therebetween to fabricate a wound electrode assembly. The separator used was a polyethylene microporous membrane with a heat-resistant layer formed on one side thereof, in which a polyamide and alumina filler was dispersed.

[0041] [Preparation of non-aqueous electrolyte] LiPF 6 was added to a mixed solvent obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of EC:EMC:DMC=3:3:4. ６ was added to give a concentration of 1 mol / L to prepare a non-aqueous electrolyte solution.

[0042] [Preparation of Coating Liquid] A first coating liquid for forming a first sealing material layer was prepared by mixing 5.0 g of butyl rubber and 5.0 g of an alkaline compound shown in Table 1 into a solvent consisting of 90 g of xylene. Further, a second coating liquid for forming a second sealing material layer was prepared by mixing 5.0 g of a fluorine-based resin shown in Table 1 into a solvent consisting of 90 g of xylene.

[0043] [Fabrication of Non-Aqueous Electrolyte Secondary Battery] A cylindrical stainless steel container with a bottom and a diameter of 18 mm and a height of 65 mm was used as the outer can. The electrode assembly was housed in the outer can with insulating plates placed above and below the electrode assembly, and the negative electrode lead was welded to the bottom of the outer can. A groove was formed in the opening of the outer can by pressing, and the first and second coating liquids were applied in this order to the area from the top surface of the groove to the inner surface of the opening edge. This was then held at room temperature for 30 minutes to form a sealant having a laminated structure in which the first and second sealing material layers were arranged in this order from the outer can side. After the non-aqueous electrolyte solution was poured, the opening of the outer can was sealed using a gasket and a sealing member. The non-aqueous electrolyte solution was poured so that it contacted the area above the groove. Five non-aqueous electrolyte secondary batteries were fabricated in this manner.

[0044] Examples 9 to 16 Non-aqueous electrolyte secondary batteries were fabricated in the same manner as in Example 1, except that a first coating solution for forming a first sealing material layer was prepared by mixing 5.0 g of butyl rubber with 90 g of xylene as a solvent, and a second coating solution for forming a second sealing material layer was prepared by mixing 5.0 g of a fluorine-based resin shown in Table 1 and 5.0 g of an alkaline compound shown in Table 1 with 90 g of xylene as a solvent.

[0045] Comparative Example 1 A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that the first coating liquid and the second coating liquid were not applied in the fabrication of the nonaqueous electrolyte secondary battery. In other words, the nonaqueous electrolyte secondary battery of Comparative Example 1 was not provided with a sealing material.

[0046] <Comparative Examples 2 and 3> In preparing the coating liquid, 5.0 g of butyl rubber and 5.0 g of an alkaline compound shown in Table 1 were mixed with a solvent consisting of 90 g of xylene to prepare a first coating liquid for forming a first sealing material layer, and nonaqueous electrolyte secondary batteries were fabricated in the same manner as in Example 1, except that only the first coating liquid was applied in fabricating the nonaqueous electrolyte secondary batteries. In other words, the sealing materials of the nonaqueous electrolyte secondary batteries of Comparative Examples 2 and 3 had a single-layer structure and only had a first sealing material layer.

[0047] [Evaluation of Oil Repellency] The first coating liquid was applied to the surface of a stainless steel plate and held at room temperature for 30 minutes to form a first sealing material layer. A predetermined amount of non-aqueous electrolyte was then dropped onto the surface of the first sealing material layer, and the contact angle was measured within 10 seconds. The contact angle of the second sealing material layer was also measured using the same method. As a result, in all examples, the contact angle of the second sealing material layer was larger than the contact angle of the first sealing material layer. In other words, in all examples, the second sealing material layer had higher oil repellency to the non-aqueous electrolyte than the first sealing material layer.

[0048] [Evaluation of Corrosion Occurrence by Accelerated Testing] The batteries of the Examples and Comparative Examples were charged at a constant current of 0.3 C in a 25°C environment until the battery voltage reached 4.2 V, and then charged at a constant voltage of 4.2 V until the current value reached 0.02 C. The batteries were then held in an environment of 75°C and 90% humidity for 30 days to conduct an accelerated test of exterior can corrosion. After the accelerated test, the batteries were subjected to 360° cross-sectional observation using an X-ray CT (Computed Tomography) device to check for the presence or absence of corrosion on the exterior can from the grooved portion to the open end. Evaluation was based on the number of batteries in which corrosion occurred. The evaluation results for the Examples and Comparative Examples are shown in Table 1.

[0049]

[0050] As shown in Table 1, no corrosion occurred in the exterior can in any of the batteries of Examples 1 to 16. On the other hand, although the rate of corrosion of the exterior can in the batteries of Comparative Examples 2 and 3 was lower than that of the battery of Comparative Example 1, corrosion of the exterior can occurred in several batteries. From this, it can be said that corrosion of the exterior can can be suppressed by providing a sealant consisting of a first sealant layer and a second sealant layer between the exterior can and the gasket, making the oil repellency of the second sealant layer to the non-aqueous electrolyte solution higher than that of the first sealant layer, and containing an alkaline compound in at least one of the first sealant layer and the second sealant layer.

[0051] The present disclosure is further described by the following embodiments. Aspect 1: A nonaqueous electrolyte secondary battery including a cylindrical outer can with a bottom, an electrode assembly and a nonaqueous electrolyte solution housed in the outer can, a sealing body that closes an opening of the outer can, a gasket disposed between the outer can and the sealing body, and a sealing material disposed between the outer can and the gasket, wherein the sealing material has a laminated structure in which a first sealing material layer and a second sealing material layer are disposed in this order from the outer can side, the second sealing material layer having higher oil repellency with respect to the nonaqueous electrolyte solution than the first sealing material layer, and at least one of the first sealing material layer and the second sealing material layer contains an alkaline compound. Aspect 2: The nonaqueous electrolyte secondary battery according to Aspect 1, wherein the first sealing material layer is composed of at least one rubber selected from the group consisting of butyl rubber, butadiene rubber, urethane rubber, silicone rubber, chloroprene rubber, and isoprene rubber. Configuration 3: The nonaqueous electrolyte secondary battery according to Configuration 1 or 2, wherein the second sealant layer is made of a fluorine-based resin.Configuration 4: The nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 3, wherein the alkaline compound includes one selected from aluminum hydroxide, magnesium hydroxide, aluminum oxide, magnesium oxide, lithium carbonate, and sodium carbonate.Configuration 5: The nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 4, wherein the content of the alkaline compound contained in the first sealant layer is greater than the content of the alkaline compound contained in the second sealant layer.Configuration 6: The nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 5, wherein, on the inner surface of the outer can, the area of ​​the region covered by the first sealant layer is greater than the area of ​​the region covered by the second sealant layer.

[0052] REFERENCE SIGNS LIST 10 non-aqueous electrolyte 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, 27a upper surface, 27b side surface, 27c lower surface, 30 sealing material, 31 first sealing material layer, 32 second sealing material layer

Claims

1. A non-aqueous electrolyte secondary battery comprising: a bottomed cylindrical exterior can; an electrode body and a non-aqueous electrolyte accommodated in the exterior can; a sealing body that closes the opening of the exterior can; a gasket disposed between the exterior can and the sealing body; and a sealing material disposed between the exterior can and the gasket, wherein the sealing material has a laminated structure arranged in the order of a first sealing material layer and a second sealing material layer from the exterior can side, the second sealing material layer has higher oil repellency to the non-aqueous electrolyte than the first sealing material layer, and at least one of the first sealing material layer and the second sealing material layer contains an alkaline compound.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the first sealing material layer is composed of at least one selected from butyl rubber, butadiene rubber, urethane rubber, silicone rubber, chloroprene rubber, and isoprene rubber.

3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the second sealing material layer is composed of a fluororesin.

4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the alkaline compound contains one selected from aluminum hydroxide, magnesium hydroxide, aluminum oxide, magnesium oxide, lithium carbonate, and sodium carbonate.

5. The non-aqueous electrolyte secondary battery according to claim 1, wherein the content of the alkaline compound contained in the first sealing material layer is larger than the content of the alkaline compound contained in the second sealing material layer.

6. The non-aqueous electrolyte secondary battery according to claim 1, wherein, on the inner surface of the exterior can, the area of the region covered by the first sealing material layer is larger than the area of the region covered by the second sealing material layer.

Images