Separator and battery including the separator

Abstract

The present invention provides a separator and a battery including the separator. The separator is composed of a substrate, a heat-resistant layer, and an adhesive layer, the heat-resistant layers are provided on both sides of the substrate so as to face each other, the adhesive layer is provided on the heat-resistant layer, the adhesive strength between the adhesive layer and the negative electrode is A, the peel strength between the heat-resistant layer and the substrate is B, and the ratio of A to B (A / B) is greater than 1. In the present invention, the heat-resistant layers of the separator are attached to the surfaces of the positive and negative electrodes, making the positive and negative electrodes less likely to short-circuit even at high temperatures, thereby improving the safety performance of the battery. In addition, in the present invention, ethyl propionate solvent is added to the non-aqueous electrolyte, so that the cell can also have low-temperature performance. Furthermore, in the present invention, due to the cooperation between the separator and the electrolyte, the battery produced effectively improves the safety performance of the cell and also has low-temperature performance of the cell.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This invention claims priority to three Chinese patent applications: a Chinese patent application filed with the Patent Office on October 25, 2021, with application number 202111251994.0 and titled "Battery"; a Chinese patent application filed with the Patent Office on October 25, 2021, with application number 202111241330.6 and titled "Battery"; and a Chinese patent application filed with the Patent Office on October 25, 2021, with application number 202111243132.3 and titled "Separator and battery comprising the separator", the contents of which are all incorporated herein by reference. The present invention belongs to the field of batteries and relates to a separator and a battery including the separator. [Background technology]

[0002] In recent years, lithium-ion batteries have been widely used in fields such as smartphones, tablet computers, smart wearables, power tools, and electric vehicles. As the popularity of lithium-ion batteries increases, consumers have increasingly higher requirements for the operating environment of lithium-ion batteries. To meet these requirements, lithium-ion batteries must have high and low temperature performance and high safety.

[0003] Currently, lithium-ion batteries present safety risks during use. For example, batteries are prone to serious safety incidents, such as fires and explosions, when used under extreme conditions, such as sustained high temperatures. The main causes of these issues are as follows: On the one hand, the structure of the positive electrode material is unstable at high temperatures and voltages. Metal ions are easily leached from the positive electrode, reducing and depositing on the negative electrode surface, destroying the SEI film structure on the negative electrode surface. This causes the negative electrode impedance and battery thickness to continuously increase, and the electrolyte and lithiated graphite react violently, releasing large amounts of heat. This causes the cell temperature to continuously rise, and if the heat continues to accumulate and cannot be released, a safety incident occurs. On the other hand, thermal contraction of the separator at high temperatures can cause a short circuit between the positive and negative electrodes, significantly reducing the battery's safety performance.

[0004] To address the above technical challenges, it is necessary to develop high-voltage lithium-ion batteries with high safety. Currently, battery safety performance is improved mainly by coating a ceramic layer on the surface of a polyolefin substrate or by adding a flame retardant (e.g., trimethyl phosphate) to the electrolyte. However, the use of ceramic separators alone is no longer sufficient to ensure the safety of batteries in high-voltage systems. Furthermore, the addition of the flame retardant additives generally leads to battery performance degradation and severely shortens the cell lifespan. Therefore, how to achieve high battery safety at high voltages without affecting the battery's electrochemical performance has become an urgent technical issue in the field of lithium-ion batteries. Summary of the Invention [Problem to be solved by the invention]

[0005] In order to solve the above technical problems, the present invention provides a separator and a battery including the separator, which has high safety performance and high voltage. [Means for solving the problem]

[0006] To achieve the above objectives, the present invention adopts the following technical solutions.

[0007] A first aspect of the present invention provides a separator, the separator comprising a substrate, a heat-resistant layer, and an adhesive layer, the heat-resistant layers being provided on both sides of the substrate so as to face each other, the adhesive layer being provided on the heat-resistant layer, the adhesive strength between the adhesive layer and the negative electrode being A, the peel strength between the heat-resistant layer and the substrate being B, and the ratio of A to B (A / B) being greater than 1.

[0008] In the separator according to the first embodiment of the present invention, the ratio of A to B is 2.5 to 6.5, and examples thereof include 2.5, 2.7, 3.0, 3.3, 3.5, 4.0, 4.5, 4.8, 5.0, 5.3, 5.5, 6.0, 6.2, 6.4, and 6.5.

[0009] In the separator according to the first aspect of the present invention, the thickness of the heat-resistant layer is 1 μm to 5 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm.

[0010] In the separator according to the first aspect of the present invention, the heat shrinkage of the heat-resistant layer at 150°C for 1 hour is 5% or less, e.g., 5%, 4%, 3%, 2.5%, 2%, 1.5%, 1%, or 0.5%.

[0011] In the separator according to the first aspect of the present invention, the adhesive strength A between the adhesive layer and the negative electrode is 10 N / m or more.

[0012] In the separator according to the first aspect of the present invention, the peel strength B between the heat-resistant layer and the substrate is 5 N / m or less.

[0013] In the separator according to the first aspect of the present invention, after a cell including the separator according to the present invention is subjected to a temperature of 70 to 90°C, a pressure of 0.6 to 3.0 MPa, a current of 0.01 C to 1 C, and a thermocompression bonding time of 30 to 300 minutes, 30% or more of the contact area of the heat-resistant layer with the positive electrode sheet and the negative electrode sheet is adhered to the active material layer of the positive electrode sheet and the negative electrode sheet (the content of the heat-resistant layer in the electrode sheet).

[0014] In the separator according to the first aspect of the present invention, the sum of the thickness of the heat-resistant layer on the positive electrode or negative electrode at the contact portion with the positive electrode sheet or negative electrode sheet and the thickness of the separator in the corresponding region is equal to the thickness at a position of the separator that is not in contact with the positive electrode or negative electrode.

[0015] In the separator according to the first aspect of the present invention, the substrate is selected from one or more of high molecular weight polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyparaphenylene, polynaphthalene, polyimide, polyamide, aramid, and polyparaphenylenebenzbisthiazole.

[0016] In the separator according to the first aspect of the present invention, the heat-resistant layer includes a ceramic, a heat-resistant polymer, and a binder.

[0017] Preferably, the weight percentage of ceramic in the heat-resistant layer is 5 to 20 wt.%, for example 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, or any value within a range formed by two of these numerical values.

[0018] Preferably, in the heat-resistant layer, the weight percentage of the heat-resistant polymer is 60 to 94 wt.%, for example, 60 wt.%, 70 wt.%, 80 wt.%, 90 wt.%, 94 wt.%, or any value within a range formed by two of these numerical values.

[0019] Preferably, in the heat-resistant layer, the weight proportion of the binder is 0.5 to 20 wt.%, for example, 0.5 wt.%, 1 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, or any value within a range formed by two of these numerical values.

[0020] In the separator according to the first aspect of the present invention, the ceramic is selected from one or more of silica, aluminum trioxide, zirconium dioxide, magnesium hydroxide, boehmite, barium sulfate, fluorphlogopite, fluorapatite, mullite, cordierite, aluminum titanate, titania, copper oxide, zinc oxide, boron nitride, aluminum nitride, magnesium nitride, and attapulgite.

[0021] In the separator according to the first aspect of the present invention, the heat-resistant polymer is selected from one or more of polyimide, aramid resin, polyamide, polybenzimidazole, polyphenylene ester, polyborodiphenylsiloxane, polyphenylene sulfide, chlorinated polyether, and polyarylsulfone.

[0022] In the separator according to the first aspect of the present invention, the binder is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, hexafluoropropylene-modified polyvinylidene fluoride, hexafluoropropylene-vinylidene fluoride copolymers (e.g., polyvinylidene fluoride-hexafluoropropylene copolymers), polyimide, polyacrylonitrile, polymethyl methacrylate, cellulose acetate, cellulose butyl acetate, cellulose propyl acetate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, and acrylonitrile-styrene-butadiene copolymer.

[0023] In the separator according to the first aspect of the present invention, the thickness of the adhesive layer is 0.5 μm to 2 μm, for example, 0.5 μm, 1 μm, or 2 μm.

[0024] In the separator according to the first aspect of the present invention, the polymer used in the adhesive layer is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, hexafluoropropylene-modified polyvinylidene fluoride, polyimide, polyacrylonitrile, polymethyl methacrylate, cellulose acetate, cellulose butyl acetate, cellulose propyl acetate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, and acrylonitrile-styrene-butadiene copolymer.

[0025] In the separator according to the first aspect of the present invention, the solvent used for the heat-resistant layer and the adhesive layer is selected from at least one of N,N-dimethylacetamide (DMAC), acetone, tetrahydrofuran, dichloromethane, chloroform, dimethylformamide, N-methyl-2-pyrrolidone, cyclohexane, methanol, ethanol, isopropanol, and water.

[0026] A second aspect of the present invention provides a battery, the battery comprising the separator described above.

[0027] In the battery according to the second aspect of the present invention, the battery further comprises a positive electrode sheet, a negative electrode sheet, and a non-aqueous electrolyte, and the separator described above is provided between the positive electrode sheet and the negative electrode sheet. The battery according to the present invention may be, for example, a lithium ion battery, and Figure 1 is a partial cross-sectional schematic diagram of a lithium ion battery according to the present invention.

[0028] In the battery according to the second aspect of the present invention, the non-aqueous electrolyte solution comprises a non-aqueous organic solvent and an additive, wherein the non-aqueous organic solvent comprises ethyl propionate.

[0029] In the battery according to the second aspect of the present invention, the additive is selected from additives for non-aqueous electrolytes known in the art, which can be prepared by methods known in the art or purchased from commercial sources.

[0030] In the battery according to the second aspect of the present invention, the amount of ethyl propionate added is 10 to 50 wt.%, preferably 20 to 40 wt.%, and examples thereof are 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, 45%, and 50% of the total mass of the non-aqueous electrolyte.

[0031] A third aspect of the present invention provides a battery, the battery comprising a positive electrode sheet, a negative electrode sheet, a separator disposed between the positive electrode sheet and the negative electrode sheet, and a non-aqueous electrolyte.

[0032] The separator is composed of a substrate, a heat-resistant layer, and an adhesive layer, the heat-resistant layers are provided on both sides of the substrate so as to face each other, the adhesive layer is provided on the heat-resistant layer, the adhesive strength between the adhesive layer and the negative electrode is A, the peel strength between the heat-resistant layer and the substrate is B, and the ratio of A to B is greater than 1.

[0033] The non-aqueous electrolyte includes a non-aqueous organic solvent and an additive, wherein the non-aqueous organic solvent includes ethyl propionate, and the additive includes a carbonate-based compound.

[0034] In the battery according to the third aspect of the present invention, the carbonate compound is fluoroethylene carbonate, vinylene carbonate, and and vinyl ethylene carbonate.

[0035] In the battery according to the third aspect of the present invention, the amount of carbonate compound added to the non-aqueous electrolyte solution accounts for 1 to 10 wt.%, preferably 5 to 10 wt.%, of the total mass of the non-aqueous electrolyte solution, and is, for example, 1 wt.%, 2 wt.%, 3 wt.%, 3.5 wt.%, 4 wt.%, 4.5 wt.%, 5 wt.%, 6 wt.%, 6.5 wt.%, 7 wt.%, 7.8 wt.%, 8 wt.%, 9 wt.%, 10 wt.%, or any value within a range formed by two of these numerical values.

[0036] In the battery according to the third aspect of the present invention, the ratio of A to B is 1.5 to 6.0, and is, for example, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, or any value within a range formed by two of these numerical values.

[0037] A fourth aspect of the present invention provides a battery, the battery comprising a positive electrode sheet, a negative electrode sheet, a separator disposed between the positive electrode sheet and the negative electrode sheet, and a non-aqueous electrolyte.

[0038] The separator is composed of a substrate, a heat-resistant layer, and an adhesive layer, the heat-resistant layers are provided on both sides of the substrate so as to face each other, the adhesive layer is provided on the heat-resistant layer, the adhesive strength between the adhesive layer and the negative electrode is A, the peel strength between the heat-resistant layer and the substrate is B, and the ratio of A to B is greater than 1.

[0039] The non-aqueous electrolyte includes a non-aqueous organic solvent and an additive, wherein the non-aqueous organic solvent includes ethyl propionate, and the additive includes a compound containing a nitrile group.

[0040] The above-mentioned compound containing a nitrile group refers to a compound containing a cyano group.

[0041] In the battery according to the fourth aspect of the present invention, the compound containing a nitrile group is succinonitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanooctane, 1,9-dicyanononane, 1,10-dicyanodecane, 1,12-dicyanododecane, tetramethylsuccinonitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 1,4-dicyanopentane, or 2,6-dicyanoheptane. , 2,7-dicyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,5-dioxaheptanedinitrile, 1,4-bis(cyanoethoxy)butane, ethylene glycol bis(2-cyanoethyl) ether, diethylene glycol bis(2-cyanoethyl) ether, trisethylene glycol bis(2-cyanoethyl) ether, tetraethylene glycol bis(2-cyanoethyl) ether, 3,6,9,12,15,18-hexaoxae Eicosanedinitrile, 1,3-di(2-cyanoethoxy)propane, 1,4-di(2-cyanoethoxy)butane, 1,5-di(2-cyanoethoxy)pentane, ethylene glycol bis(4-cyanobutyl) ether, 1,4-dicyano-2-butene, 1,4-dicyano-2-methyl-2-butene, 1,4-dicyano-2-ethyl-2-butene, 1,4-dicyano-2,3-dimethyl-2-butene, 1,4-dicyano-2,3-diethyl-2-butene, 1,6-dicyano-3-hexene, 1,6-dicyano-2-methyl-3-hexene, 1,6-dicyano Ano-2-methyl-5-methyl-3-hexene, 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6-hexanetricarbonitrile, glyceryl trinitrile, 1,2,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1,1-tris(cyanoethoxymethylene)propane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,Selected from at least one of 7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy)hexane, and 1,2,5-tris(cyanoethoxy)pentane.

[0042] In the battery according to the fourth aspect of the present invention, the amount of the compound containing a nitrile group added to the non-aqueous electrolyte solution is 1 to 10 wt.%, preferably 2 to 5 wt.%, of the total mass of the non-aqueous electrolyte solution, and is, for example, 1 wt.%, 2 wt.%, 3 wt.%, 3.5 wt.%, 4 wt.%, 4.5 wt.%, 5 wt.%, 5.5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.%, 10 wt.%, or any value within a range formed by two of these numerical values.

[0043] In the battery according to the fourth aspect of the present invention, the ratio of A to B (A / B) is 1.5 to 4.5, and is, for example, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or any value within a range formed by two of these numerical values.

[0044] In the batteries according to the third and fourth aspects of the present invention, the amount of ethyl propionate added is 10 to 40 wt. % of the total mass of the non-aqueous electrolyte, preferably 20 to 40 wt. %, and is, for example, 10 wt. %, 15 wt. %, 20 wt. %, 25 wt. %, 30 wt. %, 35 wt. %, or 40 wt. %, or any value within a range formed by two of these numerical values.

[0045] In the batteries according to the third and fourth aspects of the present invention, the additive may optionally further include other additives. For example, the other additives may be at least one of tris(trimethylsilane) phosphite, tris(trimethylsilyl) borate, lithium bistrifluoromethanesulfonylimide, lithium bisfluorosulfonylimide, 1,3-propane sultone, 1,3-propene sultone, ethylene sulfite, ethylene sulfate, vinylene carbonate, fluoroethylene carbonate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium difluoro(oxalato)phosphate, and vinylethylene carbonate.

[0046] Preferably, the amount of the other additives added accounts for 0 to 10 wt.% of the total mass of the non-aqueous electrolyte, and is, for example, 0 wt.%, 1 wt.%, 2 wt.%, 5 wt.%, 8 wt.%, 10 wt.%, or any value within a range formed by two of these numerical values.

[0047] In the batteries according to the third and fourth aspects of the present invention, the additives can be prepared by methods well known in the art or can be purchased from commercial sources.

[0048] In the batteries according to the third and fourth aspects of the present invention, the thickness of the heat-resistant layer is 1 to 3 μm, for example, 1 μm, 2 μm, or 3 μm.

[0049] In the batteries according to the third and fourth aspects of the present invention, the heat-resistant layer has a thermal shrinkage of 5% or less at 150°C for 1 hour, e.g., 5%, 4%, 3%, 2%, or 1%.

[0050] In the batteries according to the third and fourth aspects of the present invention, the adhesive strength between the adhesive layer and the negative electrode is 10 N / m or more.

[0051] In the batteries according to the third and fourth aspects of the present invention, the peel strength between the heat-resistant layer and the substrate is 5 N / m or less.

[0052] In the batteries according to the third and fourth aspects of the present invention, after a cell including a separator according to the present invention is subjected to thermocompression bonding at a temperature of 70 to 90°C, a pressure of 0.6 to 3.0 MPa, a current of 0.01 C to 1 C, and a time of 30 to 300 minutes, the paste layer adheres to the active material layers of the positive electrode sheet and the negative electrode sheet in 30% or more of the contact area of the heat-resistant layer with the positive electrode sheet and the negative electrode sheet.

[0053] In the batteries according to the third and fourth aspects of the present invention, the sum of the thickness of the heat-resistant layer on the positive electrode or negative electrode at the contact portion with the positive electrode sheet or negative electrode sheet and the thickness of the separator in the corresponding region is equal to the thickness at a position of the separator that is not in contact with the positive electrode or negative electrode.

[0054] In the batteries according to the third and fourth aspects of the present invention, the substrate is selected from one or more of polyethylene, polypropylene, polyimide, polyamide, and aramid.

[0055] In the batteries according to the third and fourth aspects of the present invention, the heat-resistant layer comprises a ceramic, a heat-resistant polymer, and a binder.

[0056] Preferably, the ratio of ceramic in the heat-resistant layer is 5 to 20 wt.%, for example, 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, or any value within a range formed by two of these numerical values.

[0057] Preferably, the ratio of the heat-resistant polymer in the heat-resistant layer is 60 to 94 wt.%, for example, 60 wt.%, 70 wt.%, 80 wt.%, 90 wt.%, 94 wt.%, or any value within a range formed by two of these numerical values.

[0058] Preferably, the ratio of the binder in the heat-resistant layer is 0.5 to 20 wt.%, for example, 0.5 wt.%, 1 wt.%, 1.5 wt.%, 3 wt.%, 4 wt.%, 5 wt.%, 6 wt.%, 8 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, or any value within a range formed by two of these numerical values.

[0059] In the batteries according to the third and fourth aspects of the present invention, the ceramic is selected from one or more of alumina, boehmite, magnesium oxide, boron nitride, and magnesium hydroxide.

[0060] In the batteries according to the third and fourth aspects of the present invention, the heat-resistant polymer is selected from one or two of polyimide, aramid resin, polyamide, and polybenzimidazole.

[0061] In the batteries according to the third and fourth aspects of the present invention, the binder is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, modified polyvinylidene fluoride-hexafluoropropylene and copolymers thereof, polyimide, polyacrylonitrile, and polymethyl methacrylate.

[0062] In the batteries according to the third and fourth aspects of the present invention, the adhesive layer has a thickness of 0.5 to 2 μm, for example, 0.5 μm, 1 μm, or 2 μm.

[0063] In the batteries according to the third and fourth aspects of the present invention, the polymer used in the adhesive layer is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer and modified copolymers thereof, polyimide, polyacrylonitrile, and polymethyl methacrylate.

[0064] In the batteries according to the third and fourth aspects of the present invention, the solvent used for the heat-resistant layer and the adhesive layer is selected from at least one of acetone, tetrahydrofuran, dichloromethane, chloroform, dimethylformamide, N-methyl-2-pyrrolidone, cyclohexane, methanol, ethanol, isopropanol, and water.

[0065] In the batteries according to the second, third and fourth aspects of the present invention, the nonaqueous organic solvent further comprises at least one of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl propionate (PP) and propyl acetate, and preferably comprises three of ethylene carbonate (EC), propylene carbonate (PC) and propyl propionate (PP).

[0066] In one exemplary embodiment of the battery according to the second and fourth aspects of the present invention, the ethylene carbonate (EC), propylene carbonate (PC), and propyl propionate (PP) are mixed in a weight ratio of 2:1:2. In one exemplary embodiment of the battery according to the third aspect of the present invention, the ethylene carbonate (EC), propylene carbonate (PC), and propyl propionate (PP) are mixed in a weight ratio of 1:1:1.

[0067] In the batteries according to the second, third and fourth aspects of the present invention, the non-aqueous electrolyte solution further contains a lithium salt.

[0068] In the batteries according to the second, third and fourth aspects of the present invention, the lithium salt is selected from at least one of lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate (LiPF), preferably lithium hexafluorophosphate (LiPF).

[0069] In the batteries according to the second, third and fourth aspects of the present invention, the lithium salt accounts for 13 to 20 wt.% of the total mass of the non-aqueous electrolyte, e.g., 13 wt.%, 14 wt.%, 15 wt.%, 16 wt.%, 17 wt.%, 18 wt.%, 19 wt.%, 20 wt.%, or any value within a range formed by two of these numerical values.

[0070] In the batteries according to the second, third and fourth aspects of the present invention, the batteries are, for example, lithium ion batteries.

[0071] In the batteries according to the second, third and fourth aspects of the present invention, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector.

[0072] Preferably, the positive electrode active material layer contains a positive electrode active material, a conductive agent, and a binder.

[0073] In one exemplary embodiment of the battery according to the second aspect of the present invention, the mixed weight ratio of the positive electrode active material, conductive agent, and binder is 97.0:1.0:2.0. In one exemplary embodiment of the battery according to the third aspect of the present invention, the mixed weight ratio of the positive electrode active material, conductive agent, and binder is 97.6:1.1:1.3. In one exemplary embodiment of the battery according to the fourth aspect of the present invention, the mixed weight ratio of the positive electrode active material, conductive agent, and binder is 98.2:1.0:0.8.

[0074] In the batteries according to the second, third and fourth aspects of the present invention, the positive electrode active material is selected from lithium cobalt oxide (LiCoO2) or lithium cobalt oxide (LiCoO2) doped and clad with two or more elements selected from Al, Mg, Mn, Cr, Ti and Zr. The chemical formula of the lithium cobalt oxide (LiCoO2) doped and clad with two or more elements selected from Al, Mg, Mn, Cr, Ti and Zr is LiCoO2. x Co 1-y1-y2-y3-y4 A y1 B y2 C y3 Dy4 O2, where 0.95≦x≦1.05, 0.01≦y1≦0.1, 0.01≦y2≦0.1, 0≦y3≦0.1, 0≦y4≦0.1, and A, B, C, and D are selected from two or more elements of Al, Mg, Mn, Cr, Ti, and Zr.

[0075] In the batteries according to the second, third and fourth aspects of the present invention, the lithium cobalt oxide doped and clad with two or more elements selected from Al, Mg, Mn, Cr, Ti and Zr has a median diameter D50 of 10 to 17 μm and a specific surface area BET of 0.15 to 0.45 m 2 / g.

[0076] In the battery according to the second aspect of the present invention, the conductive agent in the positive electrode active material layer is selected from at least one of acetylene black, carbon nanotubes, Super-P, Ketjen black, and vapor-grown carbon fiber. In the batteries according to the third and fourth aspects of the present invention, the conductive agent in the positive electrode active material layer is selected from acetylene black.

[0077] In the battery according to the second aspect of the present invention, the binder in the positive electrode active material layer is selected from at least one of polyvinylidene fluoride (PVDF) and polyvinylpyrrolidone (PVP).In the batteries according to the third and fourth aspects of the present invention, the binder in the positive electrode active material layer is selected from polyvinylidene fluoride (PVDF).

[0078] In the batteries according to the second, third, and fourth aspects of the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder.

[0079] In the batteries according to the second, third and fourth aspects of the present invention, the negative electrode active material is selected from graphite.

[0080] In the batteries according to the second, third and fourth aspects of the present invention, the negative electrode active material may optionally contain SiOx It further contains / C or Si / C, where 0 < x < 2. For example, the negative electrode active material contains 1 to 12 wt.% of SiO x It further contains / C, and illustratively, it is 1 wt.%, 2 wt.%, 5 wt.%, 8 wt.%, 10 wt.%, 12 wt.%, or any value within the range constituted by numerical values taken two at a time from these.

[0081] In the battery according to the second aspect, the third aspect, and the fourth aspect of the present invention, the charging cut-off voltage of the battery is 4.45 V or more.

Advantages of the Invention

[0082] The beneficial effects of the present invention are as follows. (1) According to the separator of the present invention, in addition to the synergistic effect of the separator and the electrolytic solution, a battery manufactured by using the combination of the positive electrode and negative electrode materials together can effectively improve the safety performance of the cell and also has the low-temperature performance of the cell. (2) In the safety separator according to the present invention, the adhesive force between the adhesive layer and the positive electrode and negative electrode is greater than the peeling force between the heat-resistant layer and the base material, and the heat-resistant layer can withstand a high temperature of 200 °C or higher. Since the separator according to the present invention is adhered to the surfaces of the positive electrode and negative electrode by the heat-resistant layer and the adhesive layer, the positive electrode and negative electrode do not short-circuit even at high temperatures. Therefore, the safety performance of the battery is improved, and thus, the effect of improving the battery safety performance is achieved by avoiding the occurrence of short-circuit and ignition between the positive electrode and negative electrode in the cell. (3) The non-aqueous electrolytic solution employed in the battery according to the three aspects provided by the present invention contains a non-aqueous organic solvent and an additive. At the same time, by adding an appropriate amount of ethyl propionate to the electrolytic solution, the electrolytic solution can swell the heat-resistant layer and the adhesive layer of the separator to a certain extent. Therefore, the positive electrode and negative electrode of the cell have a better boundary, reducing the destruction and recombination of the CEI film and improving the stability of the positive electrode material at high temperatures and high voltages. At the same time, by reducing the viscosity of the solvent, the wettability and ionic conductivity of the electrolytic solution are improved, and thus the low-temperature performance of the cell is improved. (4) The nonaqueous electrolyte employed in the battery according to the third aspect of the present invention includes a nonaqueous organic solvent and an additive. The cooperation of the additive and the nonaqueous organic solvent allows the cell to have both long cycle life and low-temperature performance. In addition to adding an appropriate amount of ethyl propionate to the nonaqueous electrolyte to improve the low-temperature performance of the cell, a carbonate-based compound is also added as an additive. The carbonate-based compound crosslinks on the negative electrode surface to form a thick and stable SEI protective film, thereby preventing the electrolyte from being reduced on the negative electrode surface and reducing heat dissipation due to side reactions. (5) The nonaqueous electrolyte employed in the battery according to the fourth aspect of the present invention includes a nonaqueous organic solvent and an additive. The synergistic effect of the additive and the nonaqueous organic solvent allows the cell to have both high-temperature and low-temperature performance. In addition to adding an appropriate amount of ethyl propionate to the nonaqueous electrolyte to improve the low-temperature performance of the cell, a compound containing a nitrile-based functional group is also added as an additive. The compound containing a nitrile-based functional group can crosslink on the positive electrode surface to form a thick and stable CEI protective film, thereby preventing the electrolyte from being oxidized on the positive electrode surface and reducing heat dissipation due to side reactions. [Brief explanation of the drawings]

[0083]

Figure 1

[0084] The present invention will be described in more detail with reference to specific examples below. However, the following examples are merely for illustrative purposes and are not to be construed as limiting the scope of protection of the present invention. All technologies realized based on the above content of the present invention should fall within the scope of protection of the present invention.

[0085] Unless otherwise specified, all raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0086] Comparative Example 1-2 and Example 1-8 The lithium ion batteries according to Comparative Example 1-2 and Examples 1-8 were manufactured according to the following manufacturing method, the only difference being the selection of separator and electrolyte, as detailed in Table 1. (1) Manufacturing of positive electrode sheets The positive electrode active material LiCoO2, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black are mixed in a weight ratio of 97:1.0:2, N-methylpyrrolidone (NMP) is added, and the mixture is stirred in a vacuum mixer until it becomes a positive electrode slurry with uniform fluidity. The positive electrode slurry is evenly coated onto an 11 μm thick aluminum foil. After coating, the aluminum foil is heated in an oven with five different temperature gradients and then dried in an oven at 120°C for 8 hours. The foil is then rolled and cut to obtain the desired positive electrode sheet. (2) Manufacturing of negative electrode sheets A slurry was produced using a wet process using 97% by weight of artificial graphite as the negative electrode material, 0.2% by weight of single-walled carbon nanotubes (SWCNT) as the conductive agent, 0.9% by weight of conductive carbon black (SP) as the conductive agent, 0.9% by weight of sodium carboxymethyl cellulose (CMC) as the binder, and 1.0% by weight of styrene-butadiene rubber (SBR) as the binder. This slurry was then applied to the surface of a 6 μm thick copper foil negative electrode current collector, dried (temperature: 85°C, time: 5 hours), rolled, and punched out to obtain a negative electrode sheet. (3) Manufacturing of non-aqueous electrolyte In an argon atmosphere glove box (moisture <10 ppm, oxygen <1 ppm), ethylene carbonate (EC), propylene carbonate (PC), and propyl propionate (PP) are mixed uniformly in a weight ratio of 1:1:3. 14 wt.% LiPF6 and 10-40 wt.% ethyl propionate (the detailed amount of ethyl propionate is shown in Table 1) are slowly added to the mixed solution and stirred uniformly to obtain a nonaqueous electrolyte. (4) Separator manufacturing The ceramic and DMAC were stirred at a solid content ratio of 20% at a speed of 1500 rpm for 30 min, and the resulting mixture was designated as solution M. The binder and DMAC were stirred at a rate of 1500 rpm for 60 min at a ratio of 10% solid content, and the resulting mixture was designated as solution N. The heat-resistant polymer and DMAC were stirred at a solid content ratio of 5% at a speed of 1500 rpm for 240 min, and the resulting mixture was designated as solution L. Solutions M, N, and L were mixed with DMAC in a predetermined ratio to obtain a mixed solution with a solid content of 6%. The mixed solution was applied to both sides of a 5 μm thick PE separator substrate using a gravure roll coating device, and after rinsing with water and drying, separator C was obtained with a thickness of 2 μm on each side. A 1 μm thick adhesive layer was applied to each side of separator C. The type of ceramic, type of binder, type of heat-resistant polymer, type of polymer used in the adhesive layer, and the ratio of ceramic, binder, and heat-resistant polymer in the heat-resistant layer are detailed in Table 1. The separator produced has an adhesive strength of A between the adhesive layer and the negative electrode, and a peel strength of B between the heat-resistant layer and the substrate. The ratio of A to B is shown in Table 1. (5) Lithium-ion battery manufacturing The prepared positive electrode sheet, separator, and negative electrode sheet are wound together to obtain a bare cell before liquid is poured in. The bare cell is placed in an outer film, and the electrolyte prepared as described above is poured into the dried bare cell. The desired lithium-ion battery is then obtained through processes such as vacuum packaging, standing, chemical conversion, molding, and classification. JPEG0007720422000001.jpg126170Note: " / " indicates no addition.

[0087] Comparative Examples 3-7 and Examples 9-16 The lithium ion batteries according to Comparative Examples 3-7 and Examples 9-16 were all manufactured according to the following manufacturing method, the only difference being the selection of separator and electrolyte, as detailed in Table 2. (1) Manufacturing of positive electrode sheets The positive electrode active material LiCoO2, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black are mixed in a weight ratio of 97.6:1.1:1.3, N-methylpyrrolidone (NMP) is added, and the mixture is stirred in a vacuum mixer until it becomes a positive electrode slurry with uniform fluidity. The positive electrode slurry is evenly coated onto an 11 μm thick aluminum foil. After coating, the aluminum foil is heated in an oven with five different temperature gradients and then dried in an oven at 120°C for 8 hours. The foil is then rolled and cut to obtain the desired positive electrode sheet. (2) Manufacturing of negative electrode sheets A slurry was produced using a wet process using 97.4 wt% artificial graphite as the negative electrode material, 0.1 wt% single-walled carbon nanotubes (SWCNT) as the conductive agent, 0.6 wt% conductive carbon black (SP) as the conductive agent, 0.9 wt% sodium carboxymethyl cellulose (CMC) as the binder, and 1.0 wt% styrene-butadiene rubber (SBR) as the binder. This slurry was then applied to the surface of a 6 μm thick copper foil negative electrode current collector, dried (temperature: 85°C, time: 5 hours), rolled, and punched to obtain a negative electrode sheet. (3) Manufacturing of non-aqueous electrolyte In an argon atmosphere glove box (moisture content <10 ppm, oxygen content <1 ppm), ethylene carbonate (EC), propylene carbonate (PC), and propyl propionate (PP) are mixed uniformly in a 1:1:1 weight ratio. 14 wt.% LiPF6, 10-40 wt.% ethyl propionate (the amount of ethyl propionate is shown in Table 2) and additives (the amount and type of additives are shown in Table 2) are slowly added to the mixed solution and stirred uniformly to obtain a nonaqueous electrolyte. (4) Separator manufacturing The ceramic and N,N-dimethylacetamide were stirred at a rate of 1500 rpm for 30 min at a solid content ratio of 20%, and the resulting mixture was designated as solution M. The binder and N,N-dimethylacetamide were stirred at a rate of 1500 rpm for 60 min at a ratio of 10% solid content, and the resulting mixture was designated as solution N. The heat-resistant polymer and N,N-dimethylacetamide were stirred at a ratio of 5% solid content at 1500 rpm for 240 min, and the resulting mixture was designated as solution L. Solutions M, N, and L were mixed with N,N-dimethylacetamide in a predetermined ratio to obtain a mixed solution with a 6% solids content. The mixed solution was applied to both sides of a 5 μm-thick polyethylene separator substrate using a gravure roll coating method. After rinsing with water and drying, separator C was obtained, with 2 μm thicknesses on each side. A 1 μm adhesive layer was applied to each side of separator C. Here, the ceramic was alumina, the binder was PVDF-HFP, the heat-resistant polymer was aramid resin, and the polymer used for the adhesive layer was polymethyl methacrylate. The ceramic to heat-resistant polymer ratio in the heat-resistant layer was 1:9, and the binder ratio in the heat-resistant layer is detailed in Table 2. The resulting separator had an adhesive strength between the adhesive layer and the negative electrode of A, and a peel strength between the heat-resistant layer and the substrate of B. The ratio of A to B is shown in Table 2. (5) Lithium-ion battery manufacturing The prepared positive electrode sheet, separator, and negative electrode sheet are wound together to obtain a bare cell before liquid is poured in. The bare cell is placed in an outer film, and the electrolyte prepared as described above is poured into the dried bare cell. The desired lithium-ion battery is then obtained through processes such as vacuum packaging, standing, chemical conversion, molding, and classification. JPEG0007720422000002.jpg117170JPEG0007720422000003.jpg41170Note: " / " indicates no addition.

[0088] Comparative Examples 8-12 and Examples 17-24 The lithium ion batteries according to Comparative Examples 8-12 and Examples 17-24 were all manufactured according to the following manufacturing method, the only difference being the selection of separator and electrolyte, as detailed in Table 3. (1) Manufacturing of positive electrode sheets The positive electrode active material LiCoO2, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black are mixed in a weight ratio of 98.2:1.0:0.8, N-methylpyrrolidone (NMP) is added, and the mixture is stirred in a vacuum mixer until it becomes a positive electrode slurry with uniform fluidity. The positive electrode slurry is evenly coated onto aluminum foil with a thickness of 10 μm. After coating, the aluminum foil is heated in an oven with five different temperature gradients and then dried in an oven at 120°C for 8 hours. The foil is then rolled and cut to obtain the desired positive electrode sheet. (2) Manufacturing of negative electrode sheets A slurry was produced using a wet process using 96.9 wt% artificial graphite as the negative electrode material, 0.1 wt% single-walled carbon nanotubes (SWCNT) as the conductive agent, 1 wt% conductive carbon black (SP) as the conductive agent, 1.0 wt% sodium carboxymethyl cellulose (CMC) as the binder, and 1.0 wt% styrene-butadiene rubber (SBR) as the binder. This slurry was then applied to the surface of a 6 μm thick copper foil negative electrode current collector, dried (temperature: 85°C, time: 5 hours), rolled, and punched to obtain a negative electrode sheet. (3) Manufacturing of non-aqueous electrolyte In an argon atmosphere glove box (water content <10 ppm, oxygen content <1 ppm), ethylene carbonate (EC), propylene carbonate (PC), and propyl propionate (PP) are mixed uniformly in a weight ratio of 2:1:2. 14 wt.% LiPF6, 10-40 wt.% ethyl propionate (the amount of ethyl propionate is shown in Table 3), and additives (the volume and type of additives are shown in Table 3) are slowly added to the mixed solution and stirred uniformly to obtain a nonaqueous electrolyte. (4) Separator manufacturing The ceramic and N,N-dimethylacetamide were stirred at a rate of 1500 rpm for 30 min at a solid content ratio of 20%, and the resulting mixture was designated as solution M. The binder and N,N-dimethylacetamide were stirred at a rate of 1500 rpm for 60 min at a ratio of 10% solid content, and the resulting mixture was designated as solution N. The heat-resistant polymer and N,N-dimethylacetamide were stirred at a ratio of 5% solid content at 1500 rpm for 240 min, and the resulting mixture was designated as solution L. Solutions M, N, and L were mixed with N,N-dimethylacetamide in a predetermined ratio to obtain a mixed solution with a 6% solids content. The mixed solution was applied to both sides of a 5 μm-thick polyethylene separator substrate using a gravure roll coating method. After rinsing with water and drying, separator C was obtained, with 2 μm thicknesses on each side. A 1 μm adhesive layer was applied to each side of separator C. Here, the ceramic was alumina, the binder was PVDF-HFP, the heat-resistant polymer was aramid resin, and the polymer used for the adhesive layer was polymethyl methacrylate. The ceramic to heat-resistant polymer ratio in the heat-resistant layer was 1:9, and the binder ratio in the heat-resistant layer is detailed in Table 3. The resulting separator had an adhesive strength between the adhesive layer and the negative electrode of A, and a peel strength between the heat-resistant layer and the substrate of B. The ratio of A to B is shown in Table 3. (5) Lithium-ion battery manufacturing The prepared positive electrode sheet, separator, and negative electrode sheet are wound together to obtain a bare cell before liquid is poured in. The bare cell is placed in an outer film, and the electrolyte prepared as described above is poured into the dried bare cell. The desired lithium-ion battery is then obtained through processes such as vacuum packaging, standing, chemical conversion, molding, and classification. JPEG0007720422000004.jpg146170Note: " / " indicates no addition.

[0089] The battery is subjected to a heat resistance performance test of the heat-resistant layer, a separator thickness test after disassembly, adhesive strength, peel strength and electrochemical performance test. The relevant explanations are as follows: Heat resistance performance test of heat-resistant layer: The heat-resistant layers of the separators according to Comparative Examples 1-12 and Examples 1-24 were heated in an oven at (150±2)°C for 1 hour. If the dimension of the separator before heating is denoted as L1 and the dimension of the separator after heating is denoted as L2 (the separator dimension refers to the length of the separator in the MD or TD direction), the thermal shrinkage of the separator is (L1-L2) / L1. The test results for Comparative Examples 1-2 and Examples 1-8 are shown in Table 1, the test results for Comparative Examples 3-7 and Examples 9-16 are shown in Table 5, and the test results for Comparative Examples 8-12 and Examples 17-24 are shown in Table 6.

[0090] Separator thickness test after disassembly: The batteries according to Comparative Examples 1-12 and Examples 1-24 were charged at a constant current of 0.7 C, with a cut-off current of 0.05 C. After full charge, the batteries were left to stand for 5 minutes, and then disassembled. A thickness test was performed on the disassembled separator. The thickness of the separator at the contact position with the electrode sheet was T1, the thickness of the separator at the non-contact position with the electrode sheet was T2, and the thickness of the substrate was T. The content of the heat-resistant layer in the electrode sheet (the remaining amount of the heat-resistant layer on the electrode sheet) was (T2 - T1) / (T2 - T). The test results for Comparative Examples 1-2 and Examples 1-8 are shown in Table 1, the test results for Comparative Examples 3-7 and Examples 9-16 are shown in Table 5, and the test results for Comparative Examples 8-12 and Examples 17-24 are shown in Table 6.

[0091] Adhesion performance test: The batteries of Comparative Example 1-12 and Example 1-24 were charged at a constant current of 0.7 C, with a final current of 0.05 C. After full charge, the batteries were left to stand for 5 minutes and then disassembled. A negative electrode sample measuring 40 mm in length and 18 mm in width was selected along the tab direction, and a 15 mm x 100 mm piece of 3M single-sided tape was attached to the negative electrode sample so that the 3M single-sided tape and the negative electrode formed a 180° included angle. The test was performed on a universal tensile tester at a speed of 100 mm / min with a test displacement of 50 mm. The test results were recorded as the adhesive strength A (unit: N / m) between the separator adhesive layer and the negative electrode.

[0092] Peel Force Test: A 40mm x 150mm steel plate was selected, and an 18mm x 100mm piece of 3M double-sided tape was attached to the steel plate. The backside of the test surface of the separators from Comparative Examples 1-12 and 1-24 was then attached to the 3M double-sided tape. A 15mm x 150mm piece of 3M double-sided tape was then attached to the test surface of the separator, forming a 180° angle between the 3M tape and the separator. The test was performed at a speed of 100mm / min with a test displacement of 50mm. The test results were recorded as the peel force B (unit: N / m) between the heat-resistant layer and the base layer of the separator.

[0093] The value of A / B is calculated based on the value of A obtained in the adhesive performance test and the value of B obtained in the peel force test. The test results of Comparative Examples 1-2 and Examples 1-8 are shown in Table 1, the test results of Comparative Examples 3-7 and Examples 9-16 are shown in Table 2, and the test results of Comparative Examples 8-12 and Examples 17-24 are shown in Table 3.

[0094] 25°C cycle test: The batteries of Comparative Examples 1-7 and Examples 1-16 were left to stand for 2-3 hours in an environment at (25±2)°C. After the battery temperature reached (25±2)°C, they were charged at a constant current of 0.7 C, with a cut-off current of 0.05 C. After full charge, the batteries were left to stand for 5 minutes and then discharged at a constant current of 0.5 C until the cut-off voltage reached 3.0 V. The maximum discharge capacity in the first three cycles was recorded as the initial capacity Q. When the number of cycles reached 1000, the final discharge capacity Q1 of the battery was recorded.

[0095] Battery capacity retention rate (%) = Q1 / Q x 100%. The test results for Comparative Examples 1-2 and Examples 1-8 are shown in Table 4, and the test results for Comparative Examples 3-7 and Examples 9-16 are shown in Table 5.

[0096] 55℃ cycle test: The batteries prepared in Comparative Examples 8-12 and Examples 17-24 were left standing for 2-3 hours in an environment at (55±2)°C. When the battery temperature reached (55±2)°C, the batteries were charged at a constant current of 0.7C, with a cut-off current of 0.05C. After full charge, the batteries were left standing for 5 minutes and then discharged at a constant current of 0.5C until the cut-off voltage reached 3.0V. The highest discharge capacity in the first three cycles was recorded as the initial capacity Q. When the number of cycles reached 300, the final discharge capacity Q1 of the batteries was recorded.

[0097] Battery capacity retention rate (%) = Q1 / Q × 100%. The test results are shown in Table 6.

[0098] -20℃ low temperature discharge test: The batteries of Comparative Examples 1-2, 8-12, Examples 1-8, and 17-24 were first discharged at 0.2 C to 3.0 V at an ambient temperature of (25±3)°C, then allowed to stand for 5 minutes, and then charged at 0.7 C. When the cell terminal voltage reached the charging limit voltage, the charger switched to constant voltage charging. Charging was stopped when the charging current was less than or equal to the end current. After allowing the cells to stand for 5 minutes, the batteries were discharged at 0.2 C to 3.0 V, and the discharge capacity was recorded as the room temperature capacity Q2. The cells were then charged at 0.7 C. When the cell terminal voltage reached the charging limit voltage, the charger switched to constant voltage charging. Charging was stopped when the charging current was less than or equal to the end current. The fully charged batteries were then allowed to stand for 4 hours at (-20±2)°C, and then discharged at 0.2 C to an end voltage of 3.0 V, and the discharge capacity Q3 was recorded. The low-temperature discharge capacity retention rate was calculated.

[0099] The low-temperature discharge capacity retention rate (%) of the battery = Q3 / Q2 × 100%. The test results of Comparative Examples 1-2 and Examples 1-8 are shown in Table 4, and the test results of Comparative Examples 8-12 and Examples 17-24 are shown in Table 6.

[0100] -10℃ low temperature discharge test: The batteries obtained in Comparative Examples 3-7 and Examples 9-16 were first discharged at 0.2 C to 3.0 V at an ambient temperature of (25 ± 3) °C, allowed to stand for 5 minutes, and then charged at 0.7 C. When the cell terminal voltage reached the charging limit voltage, the charger switched to constant voltage charging. Charging was stopped when the charging current was less than or equal to the cut-off current. After allowing to stand for 5 minutes, the batteries were discharged at 0.2 C to 3.0 V, and the discharge capacity was recorded as the room temperature capacity Q2. The cells were then charged at 0.7 C. When the cell terminal voltage reached the charging limit voltage, the charger switched to constant voltage charging. Charging was stopped when the charging current was less than or equal to the cut-off current. The fully charged batteries were then allowed to stand for 4 hours at (-10 ± 2) °C, after which they were discharged at 0.2 C to a cut-off voltage of 3.0 V, and the discharge capacity Q3 was recorded. The low-temperature discharge capacity retention rate was calculated.

[0101] The low-temperature discharge capacity retention rate (%) of the battery = Q3 / Q2 × 100%. The test results are shown in Table 5.

[0102] 150℃ thermal shock test: The batteries according to Comparative Examples 1-12 and Examples 1-24 were heated using a convection or heat circulation air box at an initial temperature of 25±3°C, and the temperature was increased to (150±2)°C at a temperature change rate of 5±2°C / min, and maintained at this temperature for 60 minutes before the test was terminated. The test results for Comparative Examples 1-2 and Examples 1-8 are shown in Table 4, the test results for Comparative Examples 3-7 and Examples 9-16 are shown in Table 5, and the test results for Comparative Examples 8-12 and Examples 17-24 are shown in Table 6.

[0103] Overcharge test: The batteries obtained in Comparative Examples 1-12 and Examples 1-24 were charged to 5 V at a constant current of 3 C rate, and the battery state was recorded. The test results for Comparative Examples 1-2 and Examples 1-8 are shown in Table 4, the test results for Comparative Examples 3-7 and Examples 9-16 are shown in Table 5, and the test results for Comparative Examples 8-12 and Examples 17-24 are shown in Table 6.

[0104] Needle stick test: The batteries according to Comparative Example 1-12 and Example 1-24 were placed in a high-temperature resistant steel needle (the cone angle of the needle tip is 45°) with a diameter of 5 to 8 mm. ° -60 ° The needle was inserted into the battery electrode sheet in a direction perpendicular to the electrode sheet at a speed of (25±5) mm / s. Preferably, the needle was inserted close to the geometric center of the surface to be pierced (the steel needle remained in the battery). The test was stopped after 1 hour or when it was observed that the maximum temperature of the battery surface had dropped to a peak temperature of 10°C or less. The test results for Comparative Examples 1-2 and Examples 1-8 are shown in Table 4, the test results for Comparative Examples 3-7 and Examples 9-16 are shown in Table 5, and the test results for Comparative Examples 8-12 and Examples 17-24 are shown in Table 6.

[0105] As can be seen from the results in Table 4, in the present invention, ethyl propionate solvent is added to the electrolyte, and a separator is used in which the adhesive strength between the adhesive layer and the positive and negative electrodes is greater than the peel strength between the heat-resistant layer and the substrate. The combined effect of these factors can significantly improve the safety performance of the lithium-ion battery, and further provide the battery with good high-temperature and low-temperature electrical performance.

[0106] As can be seen from the results in Table 5, in the present invention, a carbonate-based compound is added to the electrolyte, and ethyl propionate solvent is added. In addition, a separator is used in which the adhesive strength between the adhesive layer and the positive and negative electrodes is greater than the peel strength between the heat-resistant layer and the substrate. The combined effect of these factors can significantly improve the safety performance of the lithium-ion battery, and further provide the battery with good long-term cycle and low-temperature electrical performance.

[0107] As can be seen from the results in Table 6, in the present invention, a compound containing a nitrile functional group is added as an additive to the electrolyte, and ethyl propionate solvent is added. In addition, a separator is used in which the adhesive strength between the adhesive layer and the positive and negative electrodes is greater than the peel strength between the heat-resistant layer and the substrate. The cooperation of these factors can significantly improve the safety performance of the lithium-ion battery, and further provide the battery with good high-temperature and low-temperature electrical performance.

[0108] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and all modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should fall within the scope of protection of the present invention. [Explanation of symbols]

[0109] 101 Base material 201 Heat-resistant layer 301 Adhesive layer 401 negative electrode 501 Positive electrode

Claims

1. A battery comprising a negative electrode sheet, a separator, and a non-aqueous electrolyte, the separator is composed of a substrate, a heat-resistant layer, and an adhesive layer, the heat-resistant layers are provided on both sides of the substrate so as to face each other, and the adhesive layer is provided on the heat-resistant layer; the adhesive strength between the adhesive layer and the negative electrode sheet is A, the peel strength between the heat-resistant layer and the substrate is B, and the ratio of A to B (A / B) is greater than 1; the heat-resistant layer comprises a ceramic, a heat-resistant polymer, and a binder; In the heat-resistant layer, the weight percentage of the ceramic is 5 to 20 wt. %, the weight percentage of the heat-resistant polymer is 60 to 94 wt. %, and the weight percentage of the binder is 0.5 to 20 wt. %, The non-aqueous electrolyte solution contains a non-aqueous organic solvent, and the non-aqueous organic solvent contains ethyl propionate. A battery characterized by:

2. The ratio of A to B is 2.5 to 6.

5.

2. The battery according to claim 1 .

3. The thickness of the heat-resistant layer is 1 μm to 5 μm.

2. The battery according to claim 1 .

4. The heat-resistant layer has a thermal shrinkage of 5% or less at 150°C for 1 hour.

2. The battery according to claim 1 .

5. the adhesive strength A between the adhesive layer and the negative electrode sheet is 10 N / m or more; The peel strength B between the heat-resistant layer and the substrate is 5 N / m or less.

2. The battery according to claim 1 .

6. The substrate is selected from one or more of polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyparaphenylene, polynaphthalene, polyimide, polyamide, aramid, and polyparaphenylene benzbisthiazole.

2. The battery according to claim 1 .

7. The ceramic is selected from one or more of silica, alumina, aluminum trioxide, zirconium dioxide, magnesium hydroxide, boehmite, barium sulfate, fluorphlogopite, fluorapatite, mullite, cordierite, aluminum titanate, titania, copper oxide, zinc oxide, boron nitride, aluminum nitride, magnesium nitride, and attapulgite.

2. The battery according to claim 1 .

8. The heat-resistant polymer is selected from one or more of polyimide, aramid resin, polyamide, polybenzimidazole, polyphenylene ester, polyborodiphenylsiloxane, polyphenylene sulfide, chlorinated polyether, and polyarylsulfone.

2. The battery according to claim 1 .

9. The binder is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, hexafluoropropylene-modified polyvinylidene fluoride, polyimide, polyacrylonitrile, polymethyl methacrylate, cellulose acetate, cellulose butyl acetate, cellulose propyl acetate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, and acrylonitrile styrene butadiene copolymer.

2. The battery according to claim 1 .

10. The thickness of the adhesive layer is 0.5 μm to 2 μm.

2. The battery according to claim 1 .

11. The polymer used in the adhesive layer is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, hexafluoropropylene-modified polyvinylidene fluoride, polyimide, polyacrylonitrile, polymethyl methacrylate, cellulose acetate, cellulose butyl acetate, cellulose propyl acetate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, and acrylonitrile styrene butadiene copolymer.

2. The battery according to claim 1 .

12. Further provided with a positive electrode sheet, The separator is provided between the positive electrode sheet and the negative electrode sheet. The battery according to any one of claims 1 to 11.

13. the non-aqueous electrolyte further comprises an additive and a lithium salt; The additive includes a nitrile group-containing compound or a carbonate-based compound.

13. The battery of claim 12.

14. the amount of ethyl propionate added is 10 to 50 wt. % of the total mass of the nonaqueous electrolyte; The lithium salt accounts for 13 to 20 wt. % of the total mass of the non-aqueous electrolyte.

14. The battery of claim 13.

15. A battery, a positive electrode sheet, a negative electrode sheet, a separator disposed between the positive electrode sheet and the negative electrode sheet, and a non-aqueous electrolyte; the separator is composed of a substrate, a heat-resistant layer, and an adhesive layer, the heat-resistant layers are provided on both sides of the substrate so as to face each other, the adhesive layer is provided on the heat-resistant layer, the adhesive strength between the adhesive layer and the negative electrode sheet is A, the peel strength between the heat-resistant layer and the substrate is B, and the value of the ratio of A to B (A / B) is greater than 1, the heat-resistant layer comprises a ceramic, a heat-resistant polymer, and a binder; In the heat-resistant layer, the weight percentage of the ceramic is 5 to 20 wt. %, the weight percentage of the heat-resistant polymer is 60 to 94 wt. %, and the weight percentage of the binder is 0.5 to 20 wt. %, the non-aqueous electrolyte solution includes a non-aqueous organic solvent, an additive, and a lithium salt, the non-aqueous organic solvent includes ethyl propionate; The additive includes a carbonate-based compound or a compound containing a nitrile group. A battery characterized by:

16. The amount of ethyl propionate added is 10 to 40 wt. % of the total mass of the nonaqueous electrolyte.

16. The battery of claim 15.

17. The additive further includes another additive, and the other additive is at least one of tris(trimethylsilane) phosphite, tris(trimethylsilyl) borate, lithium bistrifluoromethanesulfonylimide, lithium bisfluorosulfonylimide, 1,3-propane sultone, 1,3-propene sultone, ethylene sulfite, ethylene sulfate, vinylene carbonate, fluoroethylene carbonate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium difluoro(oxalato)phosphate, and vinylethylene carbonate.

16. The battery of claim 15.

18. The amount of the other additives used is 0 to 10 wt. % of the total mass of the non-aqueous electrolyte.

18. The battery of claim 17.

19. The non-aqueous organic solvent further includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl propionate, and propyl acetate.

16. The battery of claim 15.

20. The lithium salt is selected from at least one of lithium bistrifluoromethylsulfonylimide, lithium bisfluorosulfonylimide, and lithium hexafluorophosphate.

16. The battery of claim 15.

21. The lithium salt accounts for 13 to 20 wt. % of the total mass of the non-aqueous electrolyte.

16. The battery of claim 15.

22. In the separator, the thickness of the heat-resistant layer is 1 to 3 μm.

16. The battery of claim 15.

23. the additive comprises a carbonate-based compound, The carbonate-based compound accounts for 1 to 10 wt. % of the total mass of the non-aqueous electrolyte.

23. The battery of any one of claims 15 to 22.

24. The carbonate compound is selected from at least one of fluoroethylene carbonate, vinylene carbonate, and vinylethylene carbonate.

24. The battery of claim 23.

25. In the separator, the ratio of A to B is 1.5 to 6.

0.

24. The battery of claim 23.

26. the additive comprises a compound containing a nitrile group; In the non-aqueous electrolyte, the amount of the compound containing a nitrile group added accounts for 1 to 10 wt. % of the total mass of the non-aqueous electrolyte.

23. The battery of any one of claims 15 to 22.

27. The compound containing a nitrile group may be succinonitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanooctane, 1,9-dicyanononane, 1,10-dicyanodecane, 1,12-dicyanododecane, tetramethylsuccinonitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 1,4-dicyanopentane, 2,6-dicyanoheptane, 2,7-dicyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,5-dioxaheptanedinitrile, 1,4-bis(cyano) 1,4-Di(2-cyanoethoxy)butane, ethylene glycol bis(2-cyanoethyl)ether, diethylene glycol bis(2-cyanoethyl)ether, trisethylene glycol bis(2-cyanoethyl)ether, tetraethylene glycol bis(2-cyanoethyl)ether, 3,6,9,12,15,18-hexaoxaeicosanedinitrile, 1,3-di(2-cyanoethoxy)propane, 1,4-di(2-cyanoethoxy)butane, 1,5-di(2-cyanoethoxy)pentane, ethylene glycol bis(4-cyanobutyl)ether, 1,4-dicyano-2-butene, 1,4-dicyano-2-methyl-2-butene, 1,4-dicyano-2-ethyl-2-butene, 1,4-dicyano-2,3-dimethyl-2-butene, 1,4-dicyano-2 ,3-diethyl-2-butene, 1,6-dicyano-3-hexene, 1,6-dicyano-2-methyl-3-hexene, 1,6-dicyano-2-methyl-5-methyl-3-hexene, 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6-hexanetricarbonitrile, glyceryl trinitrile, 1,2,6-hexanetricarbonitrile carbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1,1-tris(cyanoethoxymethylene)propane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy)hexane and 1,2,5-tris(cyanoethoxy)pentane, 27. The battery of claim 26.

28. In the separator, the ratio of A to B is 1.5 to 4.

5.

27. The battery of claim 26.

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