Secondary battery and electronic device

Abstract

The present application relates to a secondary battery and an electronic device. Specifically, the present application provides a secondary battery, comprising: a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode comprises a positive electrode current collector, and an insulating layer and a positive electrode material layer which are provided on the positive electrode current collector; the insulating layer comprises boehmite, the positive electrode material layer comprises a lithium cobalt oxide, the lithium cobalt oxide comprises element tungsten and element tin, and the electrolyte comprises vinylene carbonate. The present application can not only improve the short-circuit safety of batteries, but also enhance high-rate discharge characteristics.

Description

Secondary battery and electronic device TECHNICAL FIELD

[0001] The present application relates to the field of energy storage, in particular to a secondary battery and an electronic device. BACKGROUND

[0002] Secondary batteries have been widely used in portable electronic devices, electric vehicles and other fields due to their high energy density, repeated charging and discharging and other advantages, and are increasingly attracting attention. With the development of technology and the improvement of living standards, the use of secondary batteries in daily life is more diverse, and research on materials such as positive electrodes, negative electrodes, separators and electrolytes has been ongoing. There is an increasing demand for safety and rate performance. SUMMARY

[0003] The embodiments of the present application adjust the composition of the positive electrode and the electrolyte in the secondary battery to further improve the safety and rate performance. The present inventors have found that the positive electrode includes a positive electrode current collector and an insulating layer and a positive electrode material layer disposed on the positive electrode current collector; the insulating layer includes boehmite, and the positive electrode material layer includes lithium cobalt oxide, the lithium cobalt oxide includes tungsten element and tin element, and the electrolyte includes vinylene carbonate, which not only improves the safety of the battery short circuit, but also improves the high-rate discharge characteristics, thereby completing the present application.

[0004] In some embodiments, the mass content ratio of the tungsten element and the tin element is 1: (0.5-0.9).

[0005] In some embodiments, the electrolyte includes 1,3,6-hexanetricarbonitrile, and the 1,3,6-hexanetricarbonitrile is 0.1-1 parts by mass relative to 100 parts by mass of the electrolyte.

[0006] In some embodiments, the electrolyte includes 1,2,3-tris (2-cyanoethoxy) propane, and the 1,2,3-tris (2-cyanoethoxy) propane is 0.01-1.5 parts by mass relative to 100 parts by mass of the electrolyte.

[0007] In some embodiments, the electrolyte further includes a substance A, and the substance A includes at least one of succinonitrile, adiponitrile, ethylene glycol bis (propionitrile) ether, lithium monofluorophosphate, 1,2-bis (difluorophosphoryl) ethane, 1,2-bis (difluorophosphoryl) propane, 1,2-bis (difluorophosphoryl) butane, lithium fluorosulfonate, 1,3-propane sulfonic acid lactone or ethylene sulfate.

[0008] In some embodiments, the insulating layer includes polyvinylidene fluoride and N-methyl pyrrolidone.

[0009] In some embodiments, the electrolyte includes 4-bromophenyl isocyanate, and the 4-bromophenyl isocyanate is 0.03 to 0.7 parts by mass with respect to 100 parts by mass of the electrolyte.

[0010] In some embodiments, the electrolyte includes diethoxy isocyanophosphine, and the diethoxy isocyanophosphine is 0.01 to 3 parts by mass with respect to 100 parts by mass of the electrolyte.

[0011] In some embodiments, the electrolyte includes 4-bromophenyl isocyanate and diethoxy isocyanophosphine, and the 4-bromophenyl isocyanate is a parts by mass and the diethoxy isocyanophosphine is b parts by mass with respect to 100 parts by mass of the electrolyte, and 0.01≤a / b≤0.95.

[0012] In another aspect of the present application, the present application provides an electronic device including the secondary battery described in the present application.

[0013] The present application can not only improve the short circuit safety of the battery, but also improve the high-rate discharge characteristics by using the combination of the specific positive electrode and the electrolyte.

[0014] Additional aspects and advantages of the embodiments of the present application will be described in part below with reference to the accompanying drawings. Embodiments of the present application

[0015] Embodiments of the present application will be described in detail below. The embodiments of the present application should not be interpreted as limiting the present application.

[0016] The following terms used in the present application have the meanings indicated below, unless explicitly stated otherwise.

[0017] The present application can not only improve the short circuit safety of the battery, but also improve the high-rate discharge characteristics by using the combination of the specific positive electrode and the electrolyte.

[0018] In one embodiment, the present application provides a secondary battery including a positive electrode, a negative electrode, and an electrolyte as described below.

[0019] I. Positive electrode

[0020] The present application relates to a secondary battery and an electronic device. Specifically, the present application provides a secondary battery including a positive electrode, a negative electrode, and an electrolyte, the positive electrode including a positive electrode current collector, and an insulating layer and a positive electrode material layer disposed on the positive electrode current collector, the insulating layer including boehmite, the positive electrode material layer including lithium cobalt oxide including a tungsten element and a tin element, and the electrolyte including vinylene carbonate. The present application can not only improve the short circuit safety of the battery, but also improve the high-rate discharge characteristics.

[0021] The positive electrode material layer contains lithium cobalt oxide including tungsten and tin elements. The positive electrode material layer can be one layer or multiple layers.

[0022] The present inventors have unexpectedly found that, in the case where the positive electrode current collector has the positive electrode material layer containing the above-described lithium cobalt oxide, if the insulating layer containing boehmite is present at the same time, and the electrolyte system containing vinylene carbonate is used, the battery short circuit safety and high-rate discharge characteristics can be improved, and it is presumed that the reason is that the vinylene carbonate is closely combined with the positive electrode system in the presence of the specific intercellular edge angle in the orthorhombic system of the boehmite and the crystal structure of the lithium cobalt oxide, and not only the battery short circuit safety but also the high-rate discharge characteristics can be improved.

[0023] Specifically, from the viewpoint of improving the battery short circuit safety and high-rate discharge characteristics, the lithium cobalt oxide includes tungsten and tin elements. Among them, from the viewpoint of improving the battery short circuit safety, the mass content ratio of the tungsten and tin elements is 1: (0.5 to 0.9), preferably 1: (0.6 to 0.8), for example, 1:0.7, and when the mass content ratio of the tungsten and tin elements falls within the above range, the battery short circuit safety and high-rate discharge characteristics can be further improved.

[0024] Specifically, from the viewpoint of improving the battery short circuit safety and high-rate discharge characteristics, in some embodiments, the mass content of the tungsten element is 500 ppm to 2000 ppm, for example, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm, or a value within a range consisting of any two of them, based on the mass of the positive electrode material layer. In some embodiments, from the viewpoint of improving the battery short circuit safety and high-rate discharge characteristics, the mass content of the tin element is 100 ppm to 1000 ppm, for example, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, or a value within a range consisting of any two of them, based on the mass of the positive electrode material layer.

[0025] As the voltage at the time of charging, from the viewpoint of high-voltage, the positive electrode potential is preferably 4.4 V (vs. Li / Li + ) or more, more preferably 4.5 V (vs. Li / Li + ) or more, and particularly preferably 4.6 V (vs. Li / Li + ) or more.

[0026] The kind of the positive electrode conductive material is not limited, and any known conductive material can be used. Examples of the positive electrode conductive material can include, but are not limited to, carbon black such as acetylene black; amorphous carbon such as needle coke; and the like. Carbon nanotubes; graphene; and the like. The above-mentioned positive electrode conductive material can be used alone or in any combination.

[0027] The kind of the solvent used for forming the positive electrode slurry is not limited, as long as it is a solvent capable of dissolving or dispersing the positive electrode material, the conductive material, and the positive electrode binder. Examples of the solvent used for forming the positive electrode slurry can include any one of an aqueous solvent and an organic solvent. Examples of the aqueous medium can include, but are not limited to, water and a mixed medium composed of alcohol and water; and the like. Examples of the organic medium can include, but are not limited to, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide, and tetrahydrofuran; amides such as N-methylpyrrolidone, dimethylformamide, and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphoramide and dimethyl sulfoxide; and the like.

[0028] The density of the active material layer other than the current collector of the positive electrode is generally 3.5 g / cm3or more, and preferably 4.0 g / cm3or more. 3 In order to further increase the capacity of the battery, it is preferable that the density of the active material layer other than the current collector of the positive electrode be 4.0 g / cm3or more. 3 In order to further increase the capacity of the battery, it is preferable that the density of the active material layer other than the current collector of the positive electrode be 4.0 g / cm3or more. 3 In order to further increase the capacity of the battery, it is preferable that the density of the active material layer other than the current collector of the positive electrode be 4.0 g / cm3or more.

[0029] The kind of the positive electrode current collector is not particularly limited, and it can be any known material suitable for use as a positive electrode current collector. Examples of the positive electrode current collector can include, but are not limited to, metal materials such as aluminum, stainless steel, a nickel plating layer, titanium, and tantalum; and carbon materials such as carbon cloth and carbon paper. In some embodiments, the positive electrode current collector is a metal material. In some embodiments, the positive electrode current collector is aluminum.

[0030] In order to reduce the electronic contact resistance of the positive electrode current collector and the positive electrode material layer, the surface of the positive electrode current collector can include a conductive aid or a conductive coating. Examples of the conductive aid can include, but are not limited to, carbon and noble metals such as gold, platinum, and silver. Examples of the conductive coating can include a mixture layer containing inorganic oxides, a conductive agent, and a binder.

[0031] From the viewpoint of improving the safety against short circuit and high-rate discharge characteristics of the battery, boehmite is contained in the insulating layer.

[0032] Specifically, from the viewpoint of improving the safety against short circuit and high-rate discharge characteristics of the battery, the insulating layer includes polyvinylidene fluoride and N-methylpyrrolidone.

[0033] The positive electrode is produced by the following method:

[0034] Boehmite, polyvinylidene fluoride, and N-methylpyrrolidone are mixed, deionized water is added thereto, and mixed to produce slurry 1.

[0035] The above positive electrode material, a conductive agent such as acetylene black or carbon black, and a binder such as polyvinylidene fluoride or polyacrylonitrile are mixed, a high-boiling solvent such as N-methylpyrrolidone is added thereto, and kneaded to produce slurry 2.

[0036] Slurry 1 and slurry 2 are applied in parallel to an aluminum foil or the like serving as a current collector, and then dried and pressed to produce a positive electrode.

[0037] II. Electrolyte

[0038] The electrolyte used in the secondary battery of the present application includes an electrolyte and a solvent in which the electrolyte is dissolved. In some embodiments, the electrolyte of the present application includes vinylene carbonate.

[0039] When vinylene carbonate is used in the secondary battery of the present application, the inventors found that it not only improves the battery short-circuit safety but also improves the high-rate discharge characteristics in the addition of lithium cobalt oxide and boehmite of the positive electrode.

[0040] Specifically, from the viewpoint of improving the battery short-circuit safety and the high-rate discharge characteristics of the secondary battery, the vinylene carbonate is 0.01 parts by mass or more, preferably 0.07 parts by mass or more, and more preferably 0.15 parts by mass or more, relative to 100 parts by mass of the electrolyte. In addition, from the viewpoint of improving the battery short-circuit safety and the high-rate discharge characteristics of the secondary battery, the vinylene carbonate is 2 parts by mass or less, preferably 1.4 parts by mass or less, more preferably 0.8 parts by mass or less, further preferably 0.6 parts by mass or less, and particularly preferably 0.5 parts by mass or less.

[0041] Specifically, from the viewpoint of improving the battery short-circuit safety and the high-rate discharge characteristics of the secondary battery, the electrolyte includes 1,3,6-hexanetrione, wherein the 1,3,6-hexanetrione is 0.1 parts by mass or more, preferably 0.15 parts by mass or more, and more preferably 0.18 parts by mass or more, relative to 100 parts by mass of the electrolyte. In addition, as the upper limit of the content of 1,3,6-hexanetrione, from the viewpoint of improving the battery short-circuit safety and the high-rate discharge characteristics of the secondary battery, the 1,3,6-hexanetrione is 1 part by mass or less, preferably 0.8 parts by mass or less, more preferably 0.7 parts by mass or less, further preferably 0.6 parts by mass or less, and particularly preferably 0.5 parts by mass or less. When within the above range, it is helpful to further improve the battery short-circuit safety and the high-rate discharge characteristics of the secondary battery.

[0042] Specifically, from the viewpoint of improving the battery short circuit safety and high rate discharge characteristics of the secondary battery, the electrolyte includes 1,2,3-tris(2-cyanoethoxy)propane, wherein the 1,2,3-tris(2-cyanoethoxy)propane is 0.01 parts by mass or more, preferably 0.07 parts by mass or more, more preferably 0.15 parts by mass or more, with respect to 100 parts by mass of the electrolyte. In addition, as an upper limit of the content of the 1,2,3-tris(2-cyanoethoxy)propane, from the viewpoint of improving the battery short circuit safety and high rate discharge characteristics of the secondary battery, the 1,2,3-tris(2-cyanoethoxy)propane is 1.5 parts by mass or less, preferably 1.2 parts by mass or less, more preferably 1.1 parts by mass or less, further preferably 0.9 parts by mass or less, particularly preferably 0.8 parts by mass or less. When within the above range, it is helpful to further improve the battery short circuit safety and high rate discharge characteristics of the secondary battery.

[0043] Specifically, in some embodiments, the electrolyte further includes a substance A, the substance A includes at least one of succinonitrile, adiponitrile, ethyleneglycol bis(propionitrile) ether, lithium monofluorophosphate, 1,2-bis(difluorophosphoryl)ethane, 1,2-bis(difluorophosphoryl)propane, 1,2-bis(difluorophosphoryl)butane, lithium fluorosulfonate (LiSO3F), 1,3-propane sultone, or ethylene sulfate. Wherein, the substance A is 0.01 parts by mass or more, preferably 0.07 parts by mass or more, more preferably 0.15 parts by mass or more, with respect to 100 parts by mass of the electrolyte. In addition, from the viewpoint of improving the battery short circuit safety and high rate discharge characteristics of the secondary battery, the substance A is 1 part by mass or less, preferably 0.8 parts by mass or less, more preferably 0.7 parts by mass or less, further preferably 0.6 parts by mass or less, particularly preferably 0.5 parts by mass or less.

[0044] Specifically, from the viewpoint of improving the battery short circuit safety and high rate discharge characteristics of the secondary battery, the electrolyte includes 4-bromophenyl isocyanate. In some embodiments, the 4-bromophenyl isocyanate is a parts by mass with respect to 100 parts by mass of the electrolyte, a is in the range of 0.03 to 0.7, for example a is 0.03, 0.05, 0.08, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or a value within a range consisting of any two of them. When the mass fraction of the 4-bromophenyl isocyanate in the electrolyte is regulated to satisfy the above range, the battery short circuit safety and high rate discharge characteristics of the secondary battery can be further improved.

[0045] Specifically, from the viewpoint of improving the battery short-circuit safety and high-rate discharge characteristics of the secondary battery, the electrolyte includes diethoxyisocyanate phosphine. In some embodiments, the diethoxyisocyanate phosphine is b mass parts with respect to 100 mass parts of the electrolyte, and b is in the range of 0.01 to 3, for example, b is 0.01, 0.1, 0.2, 0.3, 0.7, 0.8, 1.1, 1.3, 1.6, 1.7, 2.0, 2.1, 2.4, 2.6, 3.0, or a value in a range defined by any two of them. When the mass fraction of diethoxyisocyanate phosphine in the electrolyte is regulated to satisfy the above range, the battery short-circuit safety and high-rate discharge characteristics of the secondary battery can be further improved.

[0046] Specifically, from the viewpoint of improving the battery short-circuit safety and high-rate discharge characteristics of the secondary battery, the electrolyte includes 4-bromophenyl isocyanate and diethoxyisocyanate phosphine. In some embodiments, 0.01≤a / b≤0.95, for example, the value of a / b is 0.01, 0.06, 0.13, 0.19, 0.27, 0.37, 0.42, 0.46, 0.52, 0.63, 0.67, 0.75, 0.87, 0.88, 0.95, or a value in a range defined by any two of them. When the mass fraction of 4-bromophenyl isocyanate and diethoxyisocyanate phosphine in the electrolyte satisfies the above relationship, the interaction and close cooperation of the two can be promoted, thereby better improving the battery short-circuit safety and high-rate discharge characteristics of the secondary battery.

[0047] In some embodiments, the additive in the electrolyte solution comprises one or more of ethylene glycol sulfate, 1,2-propanediol sulfate, 1,3-propanediol sulfate, 1,2-butanediol sulfate, 1,3-butanediol sulfate, 1,4-butanediol sulfate, 1,2-pentanediol sulfate, 1,3-pentanediol sulfate, 1,4-pentanediol sulfate, 1,5-pentanediol sulfate, dimethyl sulfate, methyl ethyl sulfate, diethyl sulfate, methyl fluorosulfonate, ethyl trifluoromethanesulfonate, methyl methanesulfonate, ethyl methanesulfonate, butyl dimethylsulfonate, methyl 2-(methylsulfonyloxy)propionate, ethyl 2-(methylsulfonyloxy)propionate, 1-fluoro-1,3-propanesultone, 2-fluoro-1,3-propanesultone, 3-fluoro-1,3-propanesultone, 1-methyl-1,3-propanesultone, 2-methyl-1,3-propanesultone, 3-methyl-1,3-propanesultone, 1-propenyl-1,3-propanesultone, 2-propenyl-1,3-propanesultone, 1-fluoro-1-propenyl-1,3-propanesultone, 2-fluoro-1-propenyl-1,3-propanesultone, 3-fluoro-1-propenyl-1,3-propanesultone, 1-fluoro-2-propenyl-1,3-propanesultone, 2-fluoro-2-propenyl-1,3-propanesultone, 3-fluoro-2-propenyl-1,3-propanesultone, 1-methyl-1-propenyl-1,3-propanesultone, 2-methyl-1-propenyl-1,3-propanesultone, 3-methyl-1-propenyl-1,3-propanesultone, 1-methyl-2-propenyl-1,3-propanesultone, 2-methyl-2-propenyl-1,3-propanesultone, 3-methyl-2-propenyl-1,3-propanesultone, 1,4-butanesultone, 1,5-pentanesultone, methanedisulfonate methylene, methanedisulfonate ethylene, dimethyl sulfite, methyl ethyl sulfite, diethyl sulfite, 1,2-ethanediol sulfite, 1,2-propanediol sulfite, 1,3-propanediol sulfite, 1,2-butanediol sulfite, 1,3-butanediol sulfite, 1,4-butanediol sulfite, 1,2-pentanediol sulfite, 1,3-pentanediol sulfite, 1,4-pentanediol sulfite, 1,5-pentanediol sulfite, and the like. In some embodiments, the electrolyte solution further includes an ionizable lithium salt, the ionizable lithium salt including at least one of LiPF6, LiSbF6, LiAsF6, LiClO4, LiN(C2F5SO2)2, CF3SO3Li, LiC(CF3SO2)3, or LiC4BO8.

[0048] The amount is 9 to 15 mass%, preferably 9 to 13 mass%, and more preferably 9 to 12 mass%. By setting the content range as described above, the effects of improving the short circuit safety of the battery and the high-rate discharge characteristics can be exerted more balancedly.

[0049] In some embodiments, the electrolyte further includes at least one of lithium difluorophosphate (LiPO2F2), lithium difluoro oxalate borate (LiDFOB), lithium bisoxalate borate (LiBOB), lithium tetrafluoroborate (LiBF4), lithium bis-trifluoromethanesulfonimide (LiTFSI), lithium bisfluorosulfonimide (LiFSI).

[0050] In some embodiments, the additive in the electrolyte further includes at least one of fluoroether compound, fluoro-carbonate compound, ether nitrile compound, such as hydrofluoroether (HFE-458), fluoroethylene carbonate (FEC), ethylene glycol bis (propionitrile) ether (DENE), and the like.

[0051] In some embodiments, the electrolyte can further include a non-aqueous solvent. The non-aqueous solvent can be selected from carbonate compound, carboxylate compound, ether compound, phosphate compound, other organic solvent, or a combination thereof.

[0052] Alternatively, the carbonate compound can be a chain carbonate compound, a cyclic carbonate compound, or a combination thereof. In another aspect, the carbonate compound can also be a fluoro-carbonate compound, a non-fluoro-carbonate compound, or a combination thereof.

[0053] Specifically, examples of the chain carbonate compound are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and a combination thereof. Examples of the cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), or a combination thereof. Examples of the fluoro-carbonate compound are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methyl ethylene carbonate, 1-fluoro-1-methyl ethylene carbonate, 1,2-difluoro-1-methyl ethylene carbonate, 1,1,2-trifluoro-2-methyl ethylene carbonate, trifluoromethyl ethylene carbonate, or a combination thereof.

[0054] Specifically, examples of the carboxylate compound are methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decalactone, valerolactone, methylvaleronolactone, hexalactone, methyl formate, or a combination thereof.

[0055] Specifically, examples of the ether compound are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, or a combination thereof.

[0056] Specifically, examples of the phosphate compound are trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or a combination thereof.

[0057] Specifically, examples of the other organic solvent are dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methylpyrrolidone, formamide, dimethylformamide, acetonitrile, or a combination thereof.

[0058] III, negative electrode

[0059] The negative electrode includes a negative electrode current collector and a negative electrode material layer disposed on a surface of the negative electrode current collector, the negative electrode material layer including a negative electrode material. In some embodiments, the chargeable capacity of the negative electrode material is greater than the discharge capacity of the positive electrode material to prevent lithium metal from inadvertently depositing on the negative electrode during charging.

[0060] Further, as the negative electrode material, there is no particular limitation, and carbon-based negative electrode materials, metal-based negative electrode materials, silicon-based negative electrode materials, and negative electrode materials combining them, and the like can be cited.

[0061] Carbon-based negative electrode material

[0062] Here, the carbon-based negative electrode material refers to an active material that can intercalate lithium with a carbon-based skeleton, and as the carbon-based negative electrode material, for example, carbonaceous materials and graphitic materials can be cited.

[0063] As the carbonaceous material, for example, easy graphitizable carbon, difficult graphitizable carbon having a structure similar to an amorphous structure represented by glassy carbon, and the like can be cited. Here, as the easy graphitizable carbon, for example, carbon materials obtained from tar pitch as a raw material from petroleum or coal can be cited. When a specific example is cited, for example, coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fibers, and pyrolytic vapor grown carbon fibers, and the like can be cited. Further, as the difficult graphitizable carbon, for example, phenol resin sintered bodies, polyacrylonitrile-based carbon fibers, quasi-isotropic carbon, furfuryl alcohol resin sintered bodies (PFA), hard carbon, and the like can be cited.

[0064] Further, as the graphitic material, for example, natural graphite, artificial graphite, and the like can be cited. Among them, as the artificial graphite, for example, artificial graphite obtained by heat-treating carbon containing easy graphitizable carbon at 2800°C or higher, graphitic MCMB obtained by heat-treating MCMB at 2000°C or higher, graphitic mesophase pitch-based carbon fibers obtained by heat-treating mesophase pitch-based carbon fibers at 2000°C or higher, and the like can be cited. In addition, in the present application, as the carbon-based negative electrode material, natural graphite in which at least a part of the surface thereof is covered with amorphous carbon (amorphous-coated natural graphite) can be used.

[0065] Further, the metal-based negative electrode material is an active material including a metal, and generally refers to an active material including an element capable of intercalating lithium or alloying with lithium in the structure, in which case the theoretical current capacity per unit mass is 500 mAh / g or more. As the metal-based negative electrode material, for example, lithium metal, elemental metals that can form lithium alloys (for example, Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, Zn, Ti, and the like), alloys thereof, and oxides, sulfides, nitrides, silicides, carbides, phosphides, and the like thereof can be used. Among them, as the metal-based negative electrode material, an active material including silicon (silicon-based negative electrode material) is preferable. This is because, by using a silicon-based negative electrode material, it is possible to increase the capacity of the secondary battery.

[0066] As the silicon-based negative electrode material, for example, silicon (Si), an alloy including silicon, SiO, SiO2, a composite of a silicon-containing material and a conductive carbon in which the silicon-containing material is coated or compounded with the conductive carbon (silicon-carbon material) can be given.

[0067] From the viewpoint of increasing the capacity of the battery, a silicon-carbon material, for example, a composite of porous carbon supporting silicon, is preferable.

[0068] In addition, the negative electrode material can be used alone or two or more kinds can be used in combination at an arbitrary ratio.

[0069] Here, the volume average particle diameter of the negative electrode material is preferably 1 μm or more, more preferably 5 μm or more, and is preferably 30 μm or less, more preferably 20 μm or less. If the volume average particle diameter of the negative electrode material is equal to or greater than the lower limit value described above, it is possible to effectively suppress the heat generation at the time of internal short circuit. In addition, if the volume average particle diameter of the negative electrode material is equal to or less than the upper limit value described above, it is possible to effectively suppress the increase in the initial resistance of the obtained battery.

[0070] The negative electrode material layer can further include a negative electrode binder. The negative electrode binder can improve the binding between the negative electrode material particles and the binding between the negative electrode material and the current collector. The kind of the negative electrode binder is not particularly limited, and can be a material stable to the electrolyte or the solvent used at the time of manufacturing the electrode. In some embodiments, the negative electrode binder includes a resin binder. Examples of the resin binder include, but are not limited to, a fluorine resin, a polyacrylonitrile (PAN), a polyimide resin, an acrylic resin, a polyolefin resin, and the like. When the negative electrode binder is prepared using an aqueous solvent, the negative electrode binder includes, but is not limited to, carboxymethyl cellulose (CMC) or a salt thereof, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, and the like.

[0071] As the current collector that holds the negative electrode material, a publicly known current collector can be arbitrarily used. Examples of the negative electrode current collector include, but are not limited to, metal materials such as copper, nickel, stainless steel, and nickel-plated steel. In some embodiments, the negative electrode current collector is copper.

[0072] The negative electrode can be produced by coating a negative electrode mixture slurry containing a negative electrode material, a resin binder, and the like on a negative electrode current collector, drying, and then calendering to form a negative electrode material layer on both sides of the negative electrode current collector, whereby a negative electrode can be obtained.

[0073] IV. Separator

[0074] In order to prevent short-circuiting, a separator is generally provided between the positive electrode and the negative electrode. In this case, the electrolyte of the present application is generally used by permeating into the separator.

[0075] The material and shape of the separator are not particularly limited as long as the effects of the present application are not significantly impaired. The separator can be a resin, a glass fiber, an inorganic substance, or the like formed of a material stable to the electrolyte of the present application. In some embodiments, the separator includes a porous sheet or a nonwoven fabric-like substance having excellent liquid retention, or the like. Examples of the material of the resin or glass fiber separator can include, but are not limited to, polyolefin, aramid, polytetrafluoroethylene, polyethersulfone, and the like. In some embodiments, the polyolefin is polyethylene or polypropylene. In some embodiments, the polyolefin is polypropylene. The above-mentioned materials of the separator can be used alone or in any combination.

[0076] The separator can also be a material in which the above-mentioned materials are layered, examples of which include, but are not limited to, a three-layer separator in which polypropylene, polyethylene, and polypropylene are layered in this order, and the like.

[0077] Examples of the material of the inorganic substance can include, but are not limited to, oxides such as alumina and silica, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate. The form of the inorganic substance can include, but is not limited to, a granular or fibrous form.

[0078] The separator can be in a film form, examples of which include, but are not limited to, a nonwoven fabric, a woven fabric, and a microporous film. In the film form, the separator has a pore diameter of 0.01 μm to 1 μm and a thickness of 5 μm to 50 μm. In addition to the above-mentioned independent film-like separator, a separator in which a composite porous layer containing the above-mentioned inorganic substance particles is formed on the surface of the positive electrode and / or the negative electrode by using a resin-based adhesive can be used, for example, a separator in which 90% of alumina particles having a particle size of less than 1 μm are formed into a porous layer on both sides of the positive electrode using a fluororesin as an adhesive.

[0079] The thickness of the separator film is arbitrary. In some embodiments, the thickness of the separator film is greater than 1 μm, greater than 5 μm, or greater than 8 μm. In some embodiments, the thickness of the separator film is less than 50 μm, less than 40 μm, or less than 30 μm. When the thickness of the separator film is within the above range, the insulation and mechanical strength can be ensured, and the direct current resistance characteristics and the energy density of the secondary battery can be ensured.

[0080] The present application also provides an electronic device comprising the secondary battery according to the present application.

[0081] The use of the secondary battery of the present application is not particularly limited, and it can be used in any electronic device known in the art. In some embodiments, the secondary battery of the present application can be used in, but not limited to, notebook computers, pen input computers, mobile computers, electronic book players, portable telephones, portable facsimile machines, portable copying machines, portable printers, head-mounted stereo headphones, video recorders, liquid crystal televisions, portable cleaners, portable CD players, mini-discs, transceivers, electronic organizers, calculators, memory cards, portable audio recorders, radios, backup power supplies, motors, automobiles, motorcycles, power-assisted bicycles, bicycles, lighting appliances, toys, game machines, timepieces, power tools, flashlights, cameras, home-use large storage batteries, and lithium ion capacitors, etc.

[0082] Embodiments

[0083] Hereinafter, embodiments of the secondary battery of the present application are shown, but the present application is not limited to these embodiments.

[0084] Preparation of the secondary battery

[0085] Preparation of the positive electrode:

[0086] Boehmite 80 wt%, polyvinylidene fluoride 20 wt% were mixed, dissolved in N-methyl pyrrolidone, deionized water was added thereto and mixed uniformly to prepare a positive electrode slurry 1.

[0087] The positive electrode material (97 wt%) in Table 1, conductive carbon black (1.5 wt%), and a solution of polyvinylidene fluoride (1.5 wt%) dissolved in N-methyl pyrrolidone were mixed and prepared into a positive electrode slurry 2. Among them, the slurry 1 was coated on the side of the tab, and the slurry 1 and the slurry 2 were coated in parallel on the aluminum foil. The coated aluminum foil was dried, pressure-treated, and cut into a predetermined size to prepare the positive electrode.

[0088] Preparation of the separator film: A 12 μm thick polyethylene (PE) microporous film was selected as the separator film.

[0089] Preparation of the negative electrode:

[0090] A negative electrode slurry was prepared by mixing artificial graphite and SiO2 (mass ratio 90:10) 96 wt%, styrene-butadiene rubber 2 wt%, adding to a solution in which carboxymethyl cellulose lithium 2 wt% was previously dissolved in deionized water and mixing. The negative electrode slurry was coated on one side of a copper foil, dried, pressure treated, and cut to a specified size to make a negative electrode.

[0091] Preparation of electrolyte: In an argon glove box with a water content of less than 10 ppm, methyl ethyl carbonate, ethyl acetate, and ethylene carbonate were mixed in a mass ratio of 1:1:1 to obtain a base solvent, and then LiPF6 and the additives shown in Table 1 were added to the base solvent. The electrolyte was obtained after mixing uniformly, wherein the mass content of LiPF6 was 12% based on the mass of the electrolyte.

[0092] Battery preparation:

[0093] The positive electrode sheet, the separator, and the negative electrode sheet were sequentially stacked in order, with the separator between the positive electrode sheet and the negative electrode sheet to serve as a barrier, and the electrode assembly was obtained by winding. After welding the tabs, the electrode assembly was placed in an outer packaging aluminum plastic film, and after removing the water at 80°C, the above electrolyte was injected. After vacuum packaging, standing, formation, shaping, capacity testing, and other processes, a secondary battery was obtained. The secondary battery was a bag-shaped battery with a width of 30 mm, a height of 45 mm, and a thickness of 5 mm.

[0094] Table 1

[0095]

[0096]

[0097]

[0098] Test method

[0099] Battery short circuit safety

[0100] The test method is as follows:

[0101] The prepared secondary battery was charged according to the following conditions:

[0102] (1) Constant current charging: the charging current was 1400 mA (the charging termination voltage was 4.6 V);

[0103] (2) Constant voltage charging: the charging voltage was 4.6 V (the charging termination current was 100 mA).

[0104] At 25°C, a round iron nail with a diameter of 2.5 mm was used to puncture the charged battery from one side at a speed of 5 mm / sec. Then, the temperature T at the position of the short circuit (punctured by the nail) was measured after 1 hour of the puncture.

[0105] The evaluation was performed by the following criteria. The smaller the value of the temperature T, the more the insulating layer in the present application and the electrolyte system can slow down the temperature fluctuation under extreme conditions (such as simulated short circuit), cooperatively control the temperature rise of the secondary battery, and help to reduce the thermal decomposition of the lithium cobalt oxide in the present application, thereby improving the safety.

[0106] A: The value of the temperature T is less than 80°C.

[0107] B: The value of the temperature T is 80°C or more and less than 100°C.

[0108] C: The value of the temperature T is 100°C or more and less than 130°C.

[0109] D: The value of the temperature T is 130°C or more.

[0110] High-rate discharge characteristics

[0111] In a constant temperature bath set at 25°C, the prepared battery was subjected to charge / discharge by the following steps:

[0112] (1) Constant current charging: charging current 0.2C (1C is 1 hour rate current), end-of-charge voltage 4.6V;

[0113] (2) Constant voltage charging: charging voltage 4.6V, end-of-charge current 0.01C;

[0114] (3) Constant current discharging: discharging current 0.2C, end-of-discharge voltage 3V.

[0115] Subsequently, the prepared battery was subjected to charge / discharge by the following steps.

[0116] (4) Constant current charging: charging current 1C, end-of-charge voltage 4.6V;

[0117] (5) Constant voltage charging: charging voltage 4.6V, end-of-charge current 0.05C;

[0118] (6) Constant current discharging: discharging current 1C, end-of-discharge voltage 3V.

[0119] Subsequently, the prepared battery was further subjected to charge / discharge by the following steps.

[0120] (7) Constant current charging: charging current 1C, end-of-charge voltage 4.6V;

[0121] (8) Constant voltage charging: charging voltage 4.6V, end of charge current 0.05C;

[0122] (9) Constant current discharging: discharging current 2.5C, end of discharge voltage 3V.

[0123] The ratio of the discharge capacity at a discharge current of 1C to the discharge capacity at a discharge current of 2.5C is determined as a percentage, and is expressed as a high-rate discharge characteristic (%).

[0124] The calculated high-rate discharge characteristic is evaluated using the following criteria. The higher the value, the better the high-rate discharge characteristic.

[0125] A: The high-rate discharge characteristic (%) is 90 or more.

[0126] B: The high-rate discharge characteristic (%) is 80 or more and less than 90.

[0127] C: The high-rate discharge characteristic (%) is 70 or more and less than 80.

[0128] D: The high-rate discharge characteristic (%) is less than 70.

[0129] Test results

[0130] In Table 1, " / " indicates that the substance is not added;

[0131] As can be seen from Table 1, the positive electrode of the application includes a positive electrode current collector and an insulating layer and a positive electrode material layer disposed on the positive electrode current collector; the insulating layer includes boehmite, and the positive electrode material layer includes lithium cobalt oxide, the lithium cobalt oxide being doped with tungsten and tin elements, and the electrolyte includes vinylene carbonate, which not only improves the short circuit safety of the battery, but also improves the high-rate discharge characteristic.

[0132] In particular, the mass content ratio of tungsten and tin elements is 1: (0.5-0.9), which can further improve the short circuit safety and high-rate discharge characteristic of the battery.

[0133] In particular, the electrolyte includes 1,3,6-hexanetricarbonitrile, which can further improve the short circuit safety and high-rate discharge characteristic of the battery.

[0134] In particular, the electrolyte includes 1,2,3-tris(2-cyanoethoxy)propane, which can further improve the short circuit safety and high-rate discharge characteristic of the battery.

[0135] In particular, the electrolyte includes substance A, which can further improve the short circuit safety and high-rate discharge characteristic of the battery.

[0136] In particular, the insulating layer includes polyvinylidene fluoride and N-methylpyrrolidone, which can further improve the short circuit safety and high-rate discharge characteristic of the battery.

[0137] In particular, the electrolyte includes 4-bromophenyl isocyanate, and 0.03 parts by mass to 0.7 parts by mass of the 4-bromophenyl isocyanate with respect to 100 parts by mass of the electrolyte can further improve the battery short-circuit safety and high-rate discharge characteristics.

[0138] In particular, the electrolyte includes diethoxy isocyanophosphonate, and 0.01 parts by mass to 3 parts by mass of the diethoxy isocyanophosphonate with respect to 100 parts by mass of the electrolyte can further improve the battery short-circuit safety and high-rate discharge characteristics.

[0139] In particular, the electrolyte includes 4-bromophenyl isocyanate and diethoxy isocyanophosphonate, and 0.01 ≤ a / b ≤ 0.95 with respect to 100 parts by mass of the electrolyte, 0.03 parts by mass to 0.7 parts by mass of the 4-bromophenyl isocyanate, and 0.01 parts by mass to 3 parts by mass of the diethoxy isocyanophosphonate can further improve the battery short-circuit safety and high-rate discharge characteristics.

[0140] The use of "example," "particular example," "one example," "another example," "some examples," "one particular example," "certain examples," or "some aspects" in the specification, throughout the claims, and in the description of the application, does not necessarily refer to the same example or aspect, but rather, could refer to a different example or aspect. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more examples or aspects.

[0141] While the illustrative embodiments have been demonstrated and described, it will be understood by those skilled in the art that the above-described embodiments are not to be construed as limiting and that changes, alternatives, and modifications can be suggested to one skilled in the art without departing from the spirit, principles, and scope of the application.

Claims

1. A secondary battery comprising: The positive electrode, the negative electrode and the electrolyte are characterized in that the positive electrode comprises a positive electrode current collector and an insulating layer and a positive electrode material layer arranged on the positive electrode current collector; the insulating layer comprises boehmite, the positive electrode material layer comprises lithium cobalt oxide, and the electrolyte comprises vinylene carbonate. The lithium cobalt oxide comprises tungsten elements and tin elements.

2. The secondary battery according to claim 1, characterized by The mass content ratio of the tungsten elements and the tin elements is 1: (0.5-0.9).

3. The secondary battery according to claim 1 or 2, characterized by The electrolyte comprises 1,3,6-hexanetricarbonitrile, and the 1,3,6-hexanetricarbonitrile is 0.1-1 parts by mass relative to 100 parts by mass of the electrolyte.

4. The secondary battery according to claim 1 or 2, characterized by The electrolyte comprises 1,2,3-tris (2-cyanoethoxy) propane, and the 1,2,3-tris (2-cyanoethoxy) propane is 0.01-1.5 parts by mass relative to 100 parts by mass of the electrolyte.

5. The secondary battery according to claim 1 or 2, characterized by The electrolyte further comprises a substance A, and the substance A comprises at least one of succinonitrile, adiponitrile, ethylene glycol bis (propionitrile) ether, lithium monofluorophosphate, 1,2-bis (difluorophosphoryl oxygen) ethane, 1,2-bis (difluorophosphoryl oxygen) propane, 1,2-bis (difluorophosphoryl oxygen) butane, lithium fluorosulfonate, 1,3-propane sultone or ethylene sulfate.

6. The secondary battery according to claim 1 or 2, characterized by The insulating layer comprises polyvinylidene fluoride and N-methylpyrrolidone.

7. The secondary battery according to claim 1 or 2, characterized by The electrolyte comprises 4-bromophenyl isocyanate, and the 4-bromophenyl isocyanate is 0.03-0.7 parts by mass relative to 100 parts by mass of the electrolyte.

8. The secondary battery according to claim 1 or 2, characterized by The electrolyte comprises diethoxy isocyanate phosphonate, and the diethoxy isocyanate phosphonate is 0.01-3 parts by mass relative to 100 parts by mass of the electrolyte.

9. The secondary battery according to claim 1 or 2, characterized by The electrolyte comprises 4-bromophenyl isocyanate and diethoxy isocyanate phosphonate, and the 4-bromophenyl isocyanate is a parts by mass and the diethoxy isocyanate phosphonate is b parts by mass relative to 100 parts by mass of the electrolyte, and 0.01≤a / b≤0.

95.

10. An electronic device, comprising: The secondary battery comprises the secondary battery according to any one of claims 1-9.

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