WO2023174185A1 - 正极片及锂离子电池 - Google Patents

正极片及锂离子电池 Download PDF

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WO2023174185A1
WO2023174185A1 PCT/CN2023/080937 CN2023080937W WO2023174185A1 WO 2023174185 A1 WO2023174185 A1 WO 2023174185A1 CN 2023080937 W CN2023080937 W CN 2023080937W WO 2023174185 A1 WO2023174185 A1 WO 2023174185A1
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positive electrode
phosphate
ether
formula
carbon atoms
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PCT/CN2023/080937
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English (en)
French (fr)
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钱韫娴
胡时光
邓永红
李红梅
向晓霞
王勇
张曌华
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深圳新宙邦科技股份有限公司
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Priority claimed from CN202210266013.8A external-priority patent/CN114883519B/zh
Application filed by 深圳新宙邦科技股份有限公司 filed Critical 深圳新宙邦科技股份有限公司
Priority to EP23723399.4A priority Critical patent/EP4270526A1/en
Publication of WO2023174185A1 publication Critical patent/WO2023174185A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This application belongs to the technical field of energy storage electronic components, and specifically relates to a positive electrode sheet and a lithium-ion battery.
  • Lithium-ion batteries have rapidly occupied the consumer electronics market and are rapidly expanding in the field of power energy storage due to their advantages such as high operating voltage, small self-discharge, long cycle life, no memory effect, environmental friendliness, and good safety performance. With the application of lithium-ion batteries in electric vehicles, large-scale energy storage stations, and mobile energy storage equipment, it is urgent to further improve the energy density and safety performance of lithium-ion batteries.
  • High-nickel cathode materials have become a hot spot in research and application due to their higher theoretical specific capacity compared to other cathode active materials.
  • the catalysis and surface effects of transition metal ions at the interface of high-nickel cathode materials cause significant oxidation and decomposition reactions in conventional electrolytes, resulting in deterioration of the electrochemical performance of the battery; in addition, the amount of delithiation of high-nickel cathode materials is greater, This will lead to poor structural stability, lead to the dissolution of transition metals during reduction reactions, and cause interfacial side reactions, thereby increasing the risk of lithium-ion batteries.
  • film-forming additives are often introduced into the electrolyte to passivate the surface of high-nickel cathode materials, thereby reducing side reactions while improving cycle performance; functional additives such as anti-overcharge and flame retardant are introduced to improve safety. performance.
  • functional additives such as anti-overcharge and flame retardant are introduced to improve safety. performance.
  • it is difficult to make lithium-ion batteries take into account the comprehensive performance of impedance, cycle and safety by introducing film-forming additives and functional additives such as anti-overcharging and flame retardant into the electrolyte.
  • this application provides a positive electrode sheet and lithium-ion battery.
  • the present application provides a cathode sheet, including a cathode current collector and a cathode material layer formed on the cathode current collector, wherein the cathode material layer includes a high-nickel cathode material represented by Formula I and a cathode material represented by Formula II.
  • the cathode material layer includes a high-nickel cathode material represented by Formula I and a cathode material represented by Formula II.
  • M is selected from one or both of Mn and Al;
  • R 1 , R 2 and R 3 are each independently selected from an alkyl group of 1-5 carbon atoms, a fluoroalkyl group of 1-5 carbon atoms, Ether group of carbon atoms, fluorinated ether group of 1-5 carbon atoms, unsaturated hydrocarbon group of 2-5 carbon atoms, and at least one of R 1 , R 2 and R 3 is 2-5 carbon atoms.
  • the positive electrode sheet meets the following conditions: 0.05 ⁇ (b/10)*(h/x) ⁇ 15;
  • b is the mass percentage of the compound represented by Formula II in the positive electrode material layer, in %;
  • x is the molar ratio of Ni element in high-nickel cathode material: (Ni element + Co element + M element);
  • h is the thickness of the cathode material layer on one side of the cathode current collector, in ⁇ m;
  • the solution obtained after ultrasonic vibration of the positive electrode piece in the solvent was analyzed by liquid chromatography-mass spectrometry (LC-MS), and characteristic peaks appeared in the region with a retention time of 6.5 min to 7.5 min.
  • LC-MS liquid chromatography-mass spectrometry
  • the positive electrode sheet meets the following conditions: 0.08 ⁇ (b/10)*(h/x) ⁇ 8.
  • the mass percentage b of the compound represented by formula II in the positive electrode material layer is 0.05% to 0.5%.
  • the molar ratio x of the Ni element in the high-nickel cathode material: (Ni element + Co element + M element) is 0.8-0.9.
  • the thickness h of the positive electrode material layer on one side of the positive electrode current collector is 100-140 ⁇ m.
  • the high-nickel cathode material represented by Formula I is selected from the group consisting of LiNi 0.8 Co 0.1 Mn 0.1 O 2 , LiNi 0.8 Co 0.1 Al 0.1 O 2 , LiNi 0.81 Co 0.16 Mn 0.03 O 2 , and LiNi 0.81 Co 0.16 Al 0.03 O 2 , LiNi 0.8 Co 0.05 Mn 0.15 O 2 , LiNi 0.8 Co 0.05 Al 0.15 O 2 , LiNi 0.7 Co 0.1 Mn 0.2 O 2 , LiNi 0.9 Co 0.05 Mn 0.05 O 2 , LiNiO 2 , LiNi 0.75 Mn 0.25 O 2 Or LiNi At least one of 0.85 Co 0.05 Mn 0.1 O 2 .
  • the mass percentage b of the high-nickel cathode material represented by formula I in the cathode material layer is 90.0% to 99.2%.
  • the alkyl group with 1 to 5 carbon atoms is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, iso- Pentyl, sec-pentyl or neopentyl;
  • the fluoroalkyl group of 1-5 carbon atoms is selected from a group in which one or more hydrogen elements in the alkyl group of 1-5 carbon atoms are replaced by fluorine elements. ;
  • the unsaturated hydrocarbon group with 2-5 carbon atoms is selected from vinyl, propenyl, allyl, butenyl, pentenyl, methylvinyl, methallyl, ethynyl, propynyl, and propargyl base, butynyl or pentynyl;
  • the ether group of 1-5 carbon atoms is selected from methyl ether, diethyl ether, methyl ethyl ether, propyl ether, methyl propyl ether or ethyl propyl ether;
  • the fluoroether group with 1 to 5 carbon atoms is selected from fluoromethyl ether, fluoroethyl ether, fluoromethylethyl ether, fluoropropyl ether, fluoromethylpropyl ether or fluoroethylpropyl ether.
  • the compound represented by formula II is selected from the group consisting of tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl fluoromethyl phosphate, and dipropargyl methoxymethyl phosphate.
  • the present application provides a lithium ion battery, including a negative electrode sheet, a non-aqueous electrolyte, and a positive electrode sheet as described above.
  • the compound represented by formula II is added to the cathode material layer.
  • the compound represented by formula II can form an effective interface film in situ on the surface of the high-nickel cathode material, so that the battery can achieve both low impedance and cycle performance. and safety performance.
  • the thickness h of the cathode material layer on one side of the current collector is such that when it meets the condition 0.05 ⁇ (b/10)*(h/x) ⁇ 15, the compound represented by Formula II and the high-nickel cathode material and cathode material can be fully utilized
  • Figure 1 is a liquid chromatography mass spectrometer (LC-MS) spectrum of the positive electrode sheet provided in this application.
  • One embodiment of the present application provides a cathode sheet, including a cathode current collector and a cathode material layer formed on the cathode current collector, wherein the cathode material layer includes a high-nickel cathode material represented by Formula I and a cathode material represented by Formula II.
  • the cathode material layer includes a high-nickel cathode material represented by Formula I and a cathode material represented by Formula II.
  • M is selected from one or both of Mn and Al;
  • R 1 , R 2 and R 3 are each independently selected from an alkyl group of 1-5 carbon atoms, a fluoroalkyl group of 1-5 carbon atoms, an ether group of 1-5 carbon atoms, A fluorinated ether group of 2 to 5 carbon atoms, an unsaturated hydrocarbon group of 2 to 5 carbon atoms, and at least one of R 1 , R 2 , and R 3 is an unsaturated hydrocarbon group of 2 to 5 carbon atoms;
  • the positive electrode sheet meets the following conditions: 0.05 ⁇ (b/10)*(h/x) ⁇ 15;
  • b is the mass percentage of the compound represented by Formula II in the positive electrode material layer, in %;
  • x is the molar ratio of Ni element in high-nickel cathode material: (Ni element + Co element + M element);
  • h is the thickness of the cathode material layer on one side of the cathode current collector, in ⁇ m;
  • the solution obtained after ultrasonic vibration of the positive electrode piece in the solvent was analyzed by liquid chromatography-mass spectrometry (LC-MS), and characteristic peaks appeared in the region with a retention time of 6.5 min to 7.5 min.
  • LC-MS liquid chromatography-mass spectrometry
  • the method for performing liquid chromatography-mass spectrometry chromatographic analysis of the positive electrode sheet is as follows: disassemble the battery in a glove box and take out the positive electrode sheet, and then immerse the cut positive electrode sheet in a suitable solvent (such as DMC, acetonitrile) , use ultrasonic vibration for an appropriate time to dissolve the substances in the positive electrode material layer of the positive electrode sheet into the solvent. Then, the solution is detected by liquid chromatography-mass spectrometry (LC-MS), and the retention time is 6.5 min. There are characteristic peaks in the ⁇ 7.5min area, as shown in Figure 1.
  • the model of the liquid chromatography-mass spectrometer is Waters ACQUITY UPLC/Xevo G2-XS Qtof MS.
  • the chromatographic conditions are: using Waters T3 type chromatographic column. The temperature is 35-40°C, the mobile phase is a mixture of 40% water and 60% acetonitrile, and the mobile phase flow rate is 0.2-0.3ml/
  • the duration of ultrasonic vibration of the positive electrode sheet in the solvent is 2 hours or more.
  • the alkyl group of 1 to 5 carbon atoms may be selected from, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl base, isopentyl, sec-pentyl or neopentyl;
  • the fluoroalkyl group of 1-5 carbon atoms is selected from the alkyl group of 1-5 carbon atoms in which one or more hydrogen elements are replaced by fluorine elements. group.
  • the unsaturated hydrocarbon group of 2 to 5 carbon atoms may be selected from, for example, vinyl, propenyl, allyl, butenyl, pentenyl, methylvinyl, methallyl, ethynyl, propynyl, Propargyl, butynyl, pentynyl.
  • the ether group of 1 to 5 carbon atoms may be selected from, for example, methyl ether, diethyl ether, methyl ethyl ether, propyl ether, methyl propyl ether, ethyl propyl ether.
  • the fluoroether group of 1 to 5 carbon atoms may be selected from, for example, fluoromethyl ether, fluoroethyl ether, fluoromethylethyl ether, fluoropropyl ether, fluoromethylpropyl ether, and fluoroethylpropyl ether.
  • Adding the compound represented by formula II to the cathode material layer can form an effective interface film in situ on the surface of the high-nickel cathode material, so that the battery can achieve both low impedance, cycle and safety properties.
  • the inventor found through extensive research that by rationally designing the mass percentage b of the compound represented by formula II in the cathode material layer, the molar ratio x of the Ni element in the high-nickel cathode material: (Ni element + Co element + M element) and the cathode
  • the thickness h of the cathode material layer on one side of the current collector is such that when it meets the condition 0.05 ⁇ (b/10)*(h/x) ⁇ 15, the compound represented by Formula II and the high-nickel cathode material and cathode material can be fully utilized.
  • the synergistic effect between layer thicknesses gives high-nickel cathode materials high structural stability and oxidation resistance, and can unexpectedly and significantly inhibit the decomposition reaction of the electrolyte after
  • the positive electrode sheet meets the following conditions: 0.08 ⁇ (b/10)*(h/x) ⁇ 8.
  • the mass percentage b of the compound represented by formula II in the positive electrode material layer the molar ratio x of the Ni element in the high-nickel positive electrode material: (Ni element + Co element + M element) and the positive electrode material layer on one side of the positive electrode current collector.
  • the mass percentage b of the compound represented by formula II in the cathode material layer is 0.005% to 1%.
  • the mass percentage b of the compound represented by Formula II in the cathode material layer can be 0.005%, 0.008%, 0.01%, 0.02%, 0.04%, 0.08%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95% or 1% .
  • the mass percentage b of the compound represented by formula II in the cathode material layer is 0.05% to 0.5%.
  • the compound represented by Formula II When the compound represented by Formula II is used as an electrolyte additive, it will form films on the surfaces of the positive and negative electrodes at the same time, resulting in an increase in the internal resistance of the battery.
  • this application adds the compound represented by Formula II to the cathode material layer.
  • the interface film formed by the compound represented by Formula II on the surface of the high-nickel cathode material can effectively inhibit the interaction between the electrolyte and the high-nickel cathode material.
  • the electrochemical oxidation reaction greatly reduces the oxygen release of high-nickel cathode materials and improves the oxidation resistance and structural stability of active materials.
  • the cathode material layer if the content of the compound represented by formula II is too small, its passivation effect on the cathode material will be limited, and thus the improvement effect on battery performance will not be obvious; if the content of the compound represented by formula II is too much, , the film will form too thick on the surface of the positive active material, which will increase the internal resistance of the battery.
  • the molar ratio x of Ni element: (Ni element + Co element + M element) in the high-nickel cathode material is 0.7-1.
  • the molar ratio x of the Ni element (Ni element + Co element + M element) in the high-nickel cathode material can be 0.7, 0.72, 0.75, 0.78, 0.8, 0.82, 0.85, 0.88, 0.9 , 0.92, 0.95, 0.98 or 1.
  • the molar ratio x of Ni element: (Ni element + Co element + M element) in the high-nickel cathode material is 0.8-0.9.
  • the proportion of Ni element in the high-nickel cathode material is an important factor affecting the theoretical specific capacity of the cathode active material.
  • the theoretical specific capacity is also higher, but its interaction with the electrolyte is The stronger the oxidation reaction, the present application can effectively reduce the negative impact of nickel in the cathode on the cathode active material and non-aqueous material by controlling the content of the compound represented by formula II in the cathode material layer and the thickness of the cathode material layer on one side of the cathode current collector.
  • the thickness h of the cathode material layer on one side of the cathode current collector is 80 to 140 ⁇ m.
  • the thickness h of the positive electrode material layer on one side of the positive electrode current collector can be 80 ⁇ m, 83 ⁇ m, 86 ⁇ m, 90 ⁇ m, 93 ⁇ m, 96 ⁇ m, 100 ⁇ m, 103 ⁇ m, 106 ⁇ m, 110 ⁇ m, 113 ⁇ m, 116 ⁇ m, 120 ⁇ m, 123 ⁇ m ,126 ⁇ m, 130 ⁇ m, 133 ⁇ m, 136 ⁇ m or 140 ⁇ m.
  • the thickness h of the positive electrode material layer on one side of the positive electrode current collector is 100-140 ⁇ m.
  • the thickness of the cathode material layer is also a key technical parameter in the design and production of lithium-ion batteries. Under the same size of the electrode piece, the greater the thickness of the positive electrode material layer, although the energy density of the battery increases, the internal resistance will also increase; while the thickness of the positive electrode material layer decreases, the energy density of the battery decreases, which is not conducive to commercialization. application.
  • the high-nickel cathode material represented by Formula I is selected from the group consisting of LiNi 0.8 Co 0.1 Mn 0.1 O 2 , LiNi 0.8 Co 0.1 Al 0.1 O 2 , LiNi 0.81 Co 0.16 Mn 0.03 O 2 , and LiNi 0.81 Co 0.16 Al 0.03 O 2 , LiNi 0.8 Co 0.05 Mn 0.15 O 2 , LiNi 0.8 Co 0.05 Al 0.15 O 2 , LiNi 0.7 Co 0.1 Mn 0.2 O 2 , LiNi 0.9 Co 0.05 Mn 0.05 O 2 , LiNiO 2 , LiNi 0.75 Mn 0 .25 O 2 Or at least one of LiNi 0.85 Co 0.05 Mn 0.1 O 2 .
  • the mass percentage b of the high-nickel cathode material represented by Formula I in the cathode material layer is 90.0% to 99.2%.
  • the compound represented by formula II is selected from the group consisting of tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl fluoromethyl phosphate, and dipropargyl methoxymethyl phosphate.
  • the compound represented by formula II is selected from one or more of the following compounds:
  • the cathode material layer further includes a cathode binder and a cathode conductive agent, the cathode active material, the compound represented by Formula II, the cathode binder and the cathode conductive agent
  • the positive electrode material layer is obtained by blending.
  • the mass percentage of the cathode binder is 1-2%, and the mass percentage of the cathode conductive agent is 0.5-2%.
  • the positive electrode binder includes polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, and vinylidene fluoride-hexafluoropropylene. Copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, ethylene-tetrafluoroethylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, ylidene fluoride Copolymer of vinyl fluoride-trifluoroethylene, copolymer of vinylidene fluoride-trichloroethylene, copolymer of vinylidene fluoride-vinyl fluoride, copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyamide Thermoplastic resins such as im
  • the positive conductive agent includes one or more of conductive carbon black, conductive carbon balls, conductive graphite, conductive carbon fiber, carbon nanotubes, graphene or reduced graphene oxide.
  • the compound represented by Formula II is formed on the surface of the cathode material layer, or the compound represented by Formula II is mixed inside the cathode material layer.
  • a coating containing the compound represented by Formula II is formed on the surface of the cathode material layer by surface coating.
  • the cathode active material, cathode conductive agent and cathode binder can be dispersed in an organic solvent first, Prepare the positive electrode slurry, apply the positive electrode slurry and dry it to form the positive electrode material layer, then disperse the compound represented by formula II in an organic solvent, and spray the obtained compound solution represented by formula II on the positive electrode material layer The surface is dried and the solvent is removed to obtain a cathode material layer including a compound represented by formula II.
  • the cathode slurry used to prepare the cathode material layer contains the compound represented by formula II.
  • the compound represented by formula II, cathode active material, cathode conductive agent and cathode binder can be dispersed in an organic solvent. , prepare a positive electrode slurry, and then apply the positive electrode slurry and dry it to form a positive electrode material layer;
  • the cathode sheet further includes a cathode current collector, and the cathode material layer is formed on the surface of the cathode current collector.
  • the positive electrode current collector is selected from metal materials that can conduct electrons.
  • the positive electrode current collector includes one or more of Al, Ni, tin, copper, and stainless steel.
  • the positive electrode current collector is selected from aluminum foil.
  • a lithium ion battery including a negative electrode sheet, a non-aqueous electrolyte, and a positive electrode sheet as described above.
  • the non-aqueous electrolyte includes a non-aqueous organic solvent
  • the non-aqueous organic solvent includes one or more of ether solvents, nitrile solvents, carbonate solvents and carboxylate solvents.
  • ether solvents include cyclic ethers or chain ethers, preferably chain ethers and carbon atoms with 3 to 10 carbon atoms. Cyclic ethers with sub-numbers of 3 to 6.
  • the cyclic ethers can be, but are not limited to, 1,3-dioxopentane (DOL), 1,4-dioxane (DX), crown ethers, and tetrahydrofuran (THF).
  • the chain ether can be, but is not limited to, two Methoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether. Since chain ethers have high solvating power with lithium ions and can improve ion dissociation, dimethoxymethane, diethoxymethane, and ethoxymethoxy are particularly preferred because they have low viscosity and can impart high ionic conductivity.
  • Methane One type of ether compound may be used alone, or two or more types of ether compounds may be used in any combination and ratio. There is no special limit to the amount of ether compound added, and it is arbitrary within the range that does not significantly damage the effect of the high-pressure lithium ion battery of the present application.
  • the volume ratio of the non-aqueous solvent is 100%, the volume ratio is usually 1% or more, and the volume ratio is preferably The volume ratio is 2% or more, and more preferably, the volume ratio is 3% or more.
  • the volume ratio is usually 30% or less, preferably 25% or less, and more preferably 20% or less.
  • the total amount of the ether compounds may satisfy the above range.
  • the amount of the ether compound added is within the above-mentioned preferred range, it is easy to ensure the improvement effect of the ion conductivity by increasing the degree of lithium ion dissociation and reducing the viscosity of the chain ether.
  • the negative electrode active material is a carbon material, the phenomenon of co-intercalation of chain ether and lithium ions can be suppressed, so that the input-output characteristics and charge-discharge rate characteristics can be achieved within an appropriate range.
  • the nitrile solvent may be, but is not limited to, one or more of acetonitrile, glutaronitrile, and malononitrile.
  • the carbonate solvent includes cyclic carbonate or chain carbonate.
  • the cyclic carbonate can be, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), and ⁇ -butyrolactone.
  • EC ethylene carbonate
  • PC propylene carbonate
  • ⁇ -butyrolactone One or more of (GBL), butylene carbonate (BC);
  • the chain carbonate can be, but is not limited to, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) ), one or more of dipropyl carbonate (DPC).
  • DMC dimethyl carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • DPC dipropyl carbonate
  • the lower limit of its content is relative to the total amount of solvent in the non-aqueous electrolyte.
  • the volume ratio is 3% or more, and preferably the volume ratio is 5% or more.
  • the upper limit of the volume ratio is usually 90% or less, preferably 85% or less, and more preferably 80% or less.
  • the content of the chain carbonate is not particularly limited, but is usually 15% or more by volume, preferably 20% or more, and more preferably 25% or more by volume relative to the total amount of solvent in the non-aqueous electrolyte solution.
  • the volume ratio is usually 90% or less, preferably 85% or less, and more preferably 80% or less.
  • the viscosity of the non-aqueous electrolyte solution can be easily brought into an appropriate range, thereby suppressing a decrease in ion conductivity, thereby contributing to bringing the output characteristics of the non-aqueous electrolyte battery into a favorable range.
  • the total amount of the linear carbonates may satisfy the above range.
  • chain carbonates having fluorine atoms may also be preferably used.
  • the number of fluorine atoms contained in the fluorinated linear carbonate is not particularly limited as long as it is 1 or more, but it is usually 6 or less, preferably 4 or less.
  • these fluorine atoms may be bonded to the same carbon or to different carbons.
  • the fluorinated chain carbonate include fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, and fluorinated diethyl carbonate derivatives.
  • Carboxylic acid ester solvents include cyclic carboxylic acid esters and/or chain carbonic acid esters.
  • cyclic carboxylic acid esters include one or more of ⁇ -butyrolactone, ⁇ -valerolactone, and ⁇ -valerolactone.
  • chain carbonates include methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), and butyl propionate. of one or more.
  • the sulfone solvent includes cyclic sulfone and chain sulfone.
  • cyclic sulfone it usually has 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms.
  • chain sulfone In the case of sulfone, it is usually a compound having 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms.
  • sulfone solvent There is no special limit to the amount of sulfone solvent added, and it is arbitrary within the range that does not significantly damage the effect of the lithium-ion battery of the present application.
  • the volume ratio relative to the total amount of solvent in the non-aqueous electrolyte is usually 0.3% or more, and the preferred volume ratio is 0.5% or more, more preferably 1% or more by volume, and usually the volume ratio is 40% or less, preferably 35% or less, more preferably 30% or less.
  • the total amount of the sulfone solvents may satisfy the above range.
  • the added amount of the sulfone solvent is within the above range, an electrolyte solution excellent in high-temperature storage stability tends to be obtained.
  • the solvent is a mixture of cyclic carbonate and chain carbonate.
  • the non-aqueous electrolyte further includes a lithium salt, including LiPF 6 , LiBOB, LiDFOB, LiPO 2 F 2 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiN(SO 2 CF 3 ) 2. LiN(SO 2 C 2 F 5 ) 2 , LiC(SO 2 CF 3 ) 3 , LiN(SO 2 F) 2 , LiClO 4 , LiAlCl 4 , LiCF 3 SO 3 , Li 2 B 10 Cl 10 , low-grade fat One or more of the lithium carboxylic acid salts of the family.
  • a lithium salt including LiPF 6 , LiBOB, LiDFOB, LiPO 2 F 2 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiN(SO 2 CF 3 ) 2. LiN(SO 2 C 2 F 5 ) 2 , LiC(SO 2 CF 3 ) 3 , LiN(SO 2 F) 2 , LiClO 4
  • the lithium salt includes LiPF 6 and an auxiliary lithium salt
  • the auxiliary lithium salt includes LiBOB, LiDFOB, LiPO 2 F 2 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 , LiC(SO 2 CF 3 ) 3 , LiN(SO 2 F) 2 , LiClO 4 , LiAlCl 4 , LiCF 3 SO 3 , Li 2 B 10 Cl 10 , lower aliphatic One or more lithium carboxylate salts.
  • adding LiPF 6 as the main lithium salt and the above-mentioned auxiliary lithium salt in the non-aqueous electrolyte can further improve the thermal shock resistance of the battery. It is speculated that this is due to the formula II contained in the positive electrode.
  • the compound is dissolved in a small amount in the non-aqueous electrolyte, and in combination with the above-mentioned lithium salt, it has the effect of improving the stability of the non-aqueous electrolyte and preventing the decomposition of the non-aqueous electrolyte to produce gas.
  • the concentration of the lithium salt in the non-aqueous electrolyte is 0.1 mol/L-8 mol/L. In a preferred embodiment, the concentration of the electrolyte salt in the non-aqueous electrolyte is 0.5 mol/L-4 mol/L. Specifically, the concentration of the lithium salt can be 0.5 mol/L, 1 mol/L, 1.5 mol/L, 2 mol/L, 2.5 mol/L, 3 mol/L, 3.5 mol/L or 4 mol/L.
  • the mass percentage of LiPF 6 is 5% to 20%, and the mass percentage of the auxiliary lithium salt is 0.05% to 5%.
  • the non-aqueous electrolyte further includes additives, including cyclic sulfate ester compounds, sultone compounds, cyclic carbonate compounds, unsaturated phosphate ester compounds and nitriles. at least one of the compounds.
  • the cyclic sulfate ester compound is selected from at least one of vinyl sulfate, propylene sulfate or vinyl methyl sulfate;
  • the sultone compound is selected from at least one of 1,3-propane sultone, 1,4-butane sultone or 1,3-propene sultone;
  • the cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene ethylene carbonate, fluoroethylene carbonate or the compound represented by formula III,
  • R 21 , R 22 , R 23 , R 24 , R 25 , and R 26 are each independently selected from one of hydrogen atoms, halogen atoms, and C1-C5 groups;
  • the unsaturated phosphate ester compound is selected from at least one compound represented by formula IV:
  • R 31 , R 32 , and R 33 are each independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si(C m H 2m+1 ) 3 , m is 1 to is a natural number of 3, and at least one of R 31 , R 32 , and R 33 is an unsaturated hydrocarbon group;
  • the unsaturated phosphate compound may be tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, or dipropargyl propyl phosphate.
  • the nitrile compounds include succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, octane One or more of dinitrile, azelonitrile, and sebaconitrile.
  • the additives may also include other additives that can improve battery performance: for example, additives that improve battery safety performance, specifically flame retardant additives such as fluorinated phosphates, cyclophosphazene, or tert-amylbenzene. , tert-butylbenzene and other anti-overcharge additives.
  • the amount of any optional substance in the additives added to the non-aqueous electrolyte is less than 10%.
  • the addition of the additives in the non-aqueous electrolyte The amount is in the range of 0.05-10%.
  • the addition amount is 0.1-5%, and more preferably, the addition amount is 0.1%-2%.
  • the amount of any optional substance in the additives can be 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2% , 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5 %, 9%, 9.5%, 10%.
  • the added amount of the fluorinated ethylene carbonate is 0.05% to 30% based on the total mass of the non-aqueous electrolyte being 100%.
  • the negative electrode sheet includes a negative electrode material layer, and the negative electrode material layer includes a negative electrode active material.
  • the negative electrode active material is selected from at least one of silicon-based negative electrodes, carbon-based negative electrodes, lithium-based negative electrodes, and tin-based negative electrodes. A sort of.
  • the silicon-based negative electrode includes one or more of silicon materials, silicon oxides, silicon-carbon composite materials and silicon alloy materials;
  • the carbon-based negative electrode includes graphite, hard carbon, soft carbon, graphene, intermediate One or more of the phase carbon microspheres; one or more of the lithium-based negative electrode metal lithium or lithium alloy.
  • the lithium alloy may specifically be at least one of lithium silicon alloy, lithium sodium alloy, lithium potassium alloy, lithium aluminum alloy, lithium tin alloy and lithium indium alloy.
  • the tin-based negative electrode includes one or more of tin, tin carbon, tin oxide, and tin metal compounds.
  • the negative electrode material layer further includes a negative electrode binder and a negative electrode conductive agent, and the negative electrode active material, the negative electrode binder and the negative electrode conductive agent are blended to obtain the negative electrode material layer.
  • the selectable ranges of the negative electrode binder and the negative electrode conductive agent are the same as those of the positive electrode binder and the positive electrode conductive agent respectively, and will not be described again here.
  • the negative electrode sheet further includes a negative electrode current collector, and the negative electrode material layer is formed on the surface of the negative electrode current collector.
  • the negative electrode current collector is selected from metal materials that can conduct electrons.
  • the negative electrode current collector includes one or more of Al, Ni, tin, copper, and stainless steel.
  • the negative electrode current collector is selected from copper foil.
  • the lithium ion battery further includes a separator, and the separator is located between the positive electrode sheet and the negative electrode sheet.
  • the separator can be an existing conventional separator, and can be a polymer separator, non-woven fabric, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP/PE, double-layer PP /PP and three-layer PP/PE/PP and other separators.
  • This example is used to illustrate the lithium-ion battery disclosed in this application and its preparation method, which includes the following steps:
  • Step 1 In the NMP solvent, add PVDF as a binder and the compound represented by Formula II shown in Table 2, stir thoroughly to obtain a PVDF glue with the compound represented by Formula II added.
  • Step 2 Add conductive agent (super P+CNT) to the PVDF glue solution and mix thoroughly.
  • Step 3 Continue to add the cathode active materials shown in Table 2, stir thoroughly, and finally obtain the required cathode slurry.
  • Step 4 Evenly coat the prepared positive electrode slurry on the positive electrode current collector (such as aluminum foil), and obtain the positive electrode sheet through drying, rolling, die-cutting or slitting.
  • the positive electrode material layer formed on one side of the positive electrode current collector is The thickness is shown in Table 2.
  • Step 2 Add CMC to pure water at a solid content of 1.5%, stir thoroughly (for example, stirring time 120 minutes), and prepare a transparent CMC glue.
  • Step 3 Add conductive carbon (super P) to the CMC glue solution and stir thoroughly (for example, stirring time 90 minutes) to prepare conductive glue.
  • Step 4 Continue to add graphite, stir thoroughly, and finally obtain the required negative electrode slurry.
  • Step 5 Evenly apply the prepared negative electrode slurry on the copper foil, and obtain negative electrode sheets through drying, rolling, die-cutting or slitting.
  • LiPF 6 lithium hexafluorophosphate
  • EMC ethyl methyl carbonate
  • the electrolyte prepared above was injected into the battery core, sealed in a vacuum, and left to rest for 24 hours. Then follow the following steps to perform the conventional formation of the first charge: 0.05C constant current charging for 180 minutes, 0.2C constant current charging to 3.95V, secondary vacuum sealing, and then further 0.2C constant current charging to 4.2V, and then left at room temperature for 24 hours. , discharge to 3.0V with a constant current of 0.2C.
  • Examples 2 to 23 are used to illustrate the lithium-ion battery disclosed in this application and its preparation method, including most of the operating steps in Example 1, and the differences are:
  • Comparative Examples 1 to 25 are used to comparatively illustrate the lithium-ion battery and its preparation method disclosed in the present application, including most of the operating steps in Example 1, and the differences are:
  • the prepared lithium-ion battery was placed in an oven with a constant temperature of 45°C, charged with a constant current of 1C to 4.2V, then charged with a constant current and a constant voltage until the current dropped to 0.05C, and then discharged with a constant current of 1C to 3.0V. , cycle like this, record the initial discharge capacity and internal resistance in the first week, when the discharge capacity of the battery drops to 80% of the initial discharge capacity, record the number of cycles of the battery.
  • the compound shown in formula II and the high-nickel cathode material have a good synergistic effect under the conditions.
  • a relatively stable interface film is formed, which improves the structural stability and oxidation resistance of the high-nickel cathode material. It also effectively isolates the non-aqueous electrolyte and the high-nickel cathode material, reducing the continued decomposition of the non-aqueous electrolyte. , thereby ensuring the consistency of the interface film thickness of the high-nickel cathode material.
  • the interface film at this thickness has lower impedance and better high-temperature stability, thus improving the high-temperature cycle life of the lithium-ion battery.

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Abstract

一种正极片包括正极集流体和形成于正极集流体上的正极材料层。正极材料层包括式I所示的高镍正极材料和式II所示的化合物： LiaNiqCoyMzO2式I 其中，0.9≤a≤1.2，0.7≤q≤1，y≥0，z≥0，且q+y+z＝1，M选自Mn及Al中的一种或两种；其中，R1、R2、R3各自独立地选自1-5个碳原子的烷基、1-5个碳原子的氟代烷基、1-5个碳原子的醚基、1-5个碳原子的氟代醚基、2-5个碳原子的不饱和烃基，且R1、R2、R3中的至少一个为2-5个碳原子的不饱和烃基；所述正极片满足以下条件： 0.05≤(b/10)*(h/x)≤15；且0.005≤b≤1，0.7≤x≤1，80≤h≤140，其中，b为正极材料层中式II所示的化合物的质量百分含量；x为高镍正极材料中Ni元素：(Ni元素+Co元素+M元素)的摩尔比值；h为正极集流体单面的正极材料层的厚度。

Description

正极片及锂离子电池 技术领域
本申请属于储能电子件技术领域，具体涉及一种正极片及锂离子电池。
背景技术
锂离子电池因其具有工作电压高、自放电小、循环寿命长、无记忆效应、环境友好且安全性能好等优点，已经迅速占领了消费类电子市场并在动力储能领域应用急剧扩张。随着锂离子电池在电动汽车、大型储能站以及移动储能设备等领域的应用，进一步提高锂离子电池的能量密度和安全性能迫在眉睫。
高镍正极材料由于其理论比容量相比于其他正极活性材料高的特点成为了研究和应用的热点。然而在使用过程中高镍正极材料界面过渡金属离子的催化和表面效应使得常规电解液会发生显著的氧化分解反应，从而引起电池电化学性能的劣化；另外高镍正极材料的脱锂量更大，因此会导致结构稳定性差，导致过渡金属发生还原反应溶出而引起界面副反应，从而增加锂离子电池的风险。
针对高镍上述问题，目前常采用在电解液中引入成膜添加剂来钝化高镍正极材料的表面，渐少副反应的同时提高循环性能；引入防过充、阻燃等功能添加剂来提高安全性能。但通过电解液中引入成膜添加剂和防过充、阻燃等功能添加剂难以使锂离子电池兼顾阻抗、循环和安全等综合性能。
发明内容
针对现有高镍锂离子电池存在的阻抗高和高温循环寿命不足问题，本申请提供了一种正极片及锂离子电池。
本申请解决上述技术问题所采用的技术方案如下：
一方面，本申请提供了一种正极片，包括正极集流体和形成于所述正极集流体上的正极材料层，其中所述正极材料层包括式I所示的高镍正极材料和式II所示的化合物：
LiaNiqCoyMzO2  式I
其中，0.9≤a≤1.2，0.7≤q≤1，y≥0，z≥0，且q+y+z＝1，M选自Mn及Al中的一种或两种；
其中，R1、R2、R3各自独立地选自1-5个碳原子的烷基、1-5个碳原子的氟代烷基、1-5个 碳原子的醚基、1-5个碳原子的氟代醚基、2-5个碳原子的不饱和烃基，且R1、R2、R3中的至少一个为2-5个碳原子的不饱和烃基；
所述正极片满足以下条件：
0.05≤(b/10)*(h/x)≤15；
且0.005≤b≤1，0.7≤x≤1，80≤h≤140；
其中，b为正极材料层中式II所示的化合物的质量百分含量，单位为％；
x为高镍正极材料中Ni元素：(Ni元素+Co元素+M元素)的摩尔比值；
h为正极集流体单面的正极材料层的厚度，单位为μm；
所述正极片在溶剂中超声震荡后所得的溶液进行液相色谱-质谱联用仪(LC-MS)分析，在保留时间为6.5min～7.5min的区域出现特征峰。
可选的，所述正极片满足以下条件：
0.08≤(b/10)*(h/x)≤8。
可选的，所述正极材料层中式II所示的化合物的质量百分含量b为0.05％～0.5％。
可选的，所述高镍正极材料中Ni元素：(Ni元素+Co元素+M元素)的摩尔比值x为0.8-0.9。
可选的，所述正极集流体单面的正极材料层的厚度h为100～140μm。
可选的，所述式I所示的高镍正极材料选自LiNi0.8Co0.1Mn0.1O2、LiNi0.8Co0.1Al0.1O2、LiNi0.81Co0.16Mn0.03O2、LiNi0.81Co0.16Al0.03O2、LiNi0.8Co0.05Mn0.15O2、LiNi0.8Co0.05Al0.15O2、LiNi0.7Co0.1Mn0.2O2、LiNi0.9Co0.05Mn0.05O2、LiNiO2、LiNi0.75Mn0.25O2或LiNi0.85Co0.05Mn0.1O2中的至少一种。
可选的，所述正极材料层中式I所示的高镍正极材料的质量百分含量b为90.0％～99.2％。
可选的，1-5个碳原子的烷基选自甲基、乙基、正丙基、异丙基、正丁基、异丁基、仲丁基、叔丁基、正戊基、异戊基、仲戊基或新戊基；1-5个碳原子的氟代烷基选自该1-5个碳原子的烷基中的一个或多个氢元素被氟元素取代所得的基团；
2-5个碳原子的不饱和烃基选自乙烯基、丙烯基、烯丙基、丁烯基、戊烯基、甲基乙烯基、甲基烯丙基、乙炔基、丙炔基、炔丙基、丁炔基或戊炔基；
1-5个碳原子的醚基选自甲醚、***、甲***、丙醚、甲丙醚或乙丙醚；
1-5个碳原子的氟代醚基选自氟代甲醚、氟代***、氟代甲***、氟代丙醚、氟代甲丙醚或氟代乙丙醚。
可选的，所述式II所示的化合物选自磷酸三炔丙酯、二炔丙基甲基磷酸酯、二炔丙基氟代甲基磷酸酯、二炔丙基甲氧基甲基磷酸酯、二炔丙基乙基磷酸酯、二炔丙基丙基磷酸酯、三氟甲基二炔丙基磷酸酯、二炔丙基2,2,2-三氟乙基磷酸酯、二炔丙基3,3,3-三氟丙基磷酸酯、六氟异丙基二炔丙基磷酸酯、磷酸三烯丙酯、二烯丙基甲基磷酸酯、二烯丙基乙基磷酸酯、二烯丙 基丙基磷酸酯、三氟甲基二烯丙基磷酸酯、二炔丙基甲醚磷酸酯、二炔丙基氟代甲醚磷酸酯、2,2,2-三氟乙基二烯丙基磷酸酯、二烯丙基3,3,3-三氟丙基磷酸酯或二烯丙基六氟异丙基磷酸酯中的至少一种。
另一方面，本申请提供了一种锂离子电池，包括负极片、非水电解液以及如上所述的正极片。
根据本申请提供的正极片，在正极材料层中加入式II所示的化合物，式II所示的化合物能够在高镍正极材料的表面原位形成有效的界面膜，使电池兼顾低阻抗、循环和安全等性能。发明人通过大量研究发现，通过合理设计正极材料层中式II所示的化合物的质量百分含量b、高镍正极材料中Ni元素：(Ni元素+Co元素+M元素)的摩尔比值x和正极集流体单面的正极材料层的厚度h，使其满足条件0.05≤(b/10)*(h/x)≤15时，能够充分发挥式II所示的化合物与高镍正极材料和正极材料层厚度之间的协同效应，使高镍正极材料具有较高的结构稳定性和耐氧化性，能够出人意料且显著地抑制高温充电后电解液的分解反应，从而改善电池的循环和阻抗性能。
附图说明
图1是本申请提供的正极片的液相色谱质谱联用仪(LC-MS)图谱。
具体实施方式
为了使本申请所解决的技术问题、技术方案及有益效果更加清楚明白，以下结合附图及实施例，对本申请进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本申请，并不用于限定本申请。
本申请一实施例提供了一种正极片，包括正极集流体和形成于所述正极集流体上的正极材料层，其中所述正极材料层包括式I所示的高镍正极材料和式II所示的化合物：
LiaNiqCoyMzO2  式I
其中，0.9≤a≤1.2，0.7≤q≤1，y≥0，z≥0，且q+y+z＝1，M选自Mn及Al中的一种或两种；
其中，R1、R2、R3各自独立地选自1-5个碳原子的烷基、1-5个碳原子的氟代烷基、1-5个碳原子的醚基、1-5个碳原子的氟代醚基、2-5个碳原子的不饱和烃基，且R1、R2、R3中的至少一个为2-5个碳原子的不饱和烃基；
所述正极片满足以下条件：
0.05≤(b/10)*(h/x)≤15；
且0.005≤b≤1，0.7≤x≤1，80≤h≤140；
其中，b为正极材料层中式II所示的化合物的质量百分含量，单位为％；
x为高镍正极材料中Ni元素：(Ni元素+Co元素+M元素)的摩尔比值；
h为正极集流体单面的正极材料层的厚度，单位为μm；
所述正极片在溶剂中超声震荡后所得的溶液进行液相色谱-质谱联用仪(LC-MS)分析，在保留时间为6.5min～7.5min的区域出现特征峰。
所述正极片进行液相色谱-质谱联用仪色谱分析的方法为：在手套箱中将电池拆解取出正极片，再将裁切好的正极片浸入合适的溶剂(例如DMC、乙腈)中，通过超声震荡适宜的时间，以将正极片的正极材料层中的物质溶解到溶剂中，然后，此溶液通过液相色谱-质谱联用仪(LC-MS)检测，在保留时间为6.5min～7.5min的区域具有特征峰，如图1所示，其中液相色谱-质谱联用仪的型号为Waters ACQUITY UPLC/Xevo G2-XS Qtof MS，色谱条件为：采用Waters T3型色谱柱，柱温35-40℃，流动相为40％水与60％乙腈的混合物，流动相流速为0.2-0.3ml/min。
在一些实施例中，正极片在溶剂中超声震荡的时长为2小时及以上。
在本申请中，1-5个碳原子的烷基可选自例如甲基、乙基、正丙基、异丙基、正丁基、异丁基、仲丁基、叔丁基、正戊基、异戊基、仲戊基或新戊基；1-5个碳原子的氟代烷基选自该1-5个碳原子的烷基中的一个或多个氢元素被氟元素取代所得的基团。
2-5个碳原子的不饱和烃基可选自例如乙烯基、丙烯基、烯丙基、丁烯基、戊烯基、甲基乙烯基、甲基烯丙基、乙炔基、丙炔基、炔丙基、丁炔基、戊炔基。
1-5个碳原子的醚基可选自例如甲醚、***、甲***、丙醚、甲丙醚、乙丙醚。
1-5个碳原子的氟代醚基可选自例如氟代甲醚、氟代***、氟代甲***、氟代丙醚、氟代甲丙醚、氟代乙丙醚。
在正极材料层中加入式II所示的化合物，式II所示的化合物能够在高镍正极材料的表面原位形成有效的界面膜，使电池兼顾的低阻抗、循环和安全等性能。发明人通过大量研究发现，通过合理设计正极材料层中式II所示的化合物的质量百分含量b、高镍正极材料中Ni元素：(Ni元素+Co元素+M元素)的摩尔比值x和正极集流体单面的正极材料层的厚度h，使其满足条件0.05≤(b/10)*(h/x)≤15时，能够充分发挥式II所示的化合物与高镍正极材料和正极材料层厚度之间的协同效应，使高镍正极材料具有较高的结构稳定性和耐氧化性，能够出人意料且显著地抑制高温充电后电解液的分解反应，从而改善电池的循环和阻抗性能。
在优选的实施例中，所述正极片满足以下条件：
0.08≤(b/10)*(h/x)≤8。
当正极材料层中式II所示的化合物的质量百分含量b、高镍正极材料中Ni元素：(Ni元素+Co元素+M元素)的摩尔比值x和正极集流体单面的正极材料层的厚度h满足上述条件时， 能够进一步提高电池的循环性能和降低电池阻抗。
根据本申请的实施例，所述正极材料层中式II所示的化合物的质量百分含量b为0.005％～1％。在具体的实施例中，所述正极材料层中式II所示的化合物的质量百分含量b可以为0.005％、0.008％、0.01％、0.02％、0.04％、0.08％、0.1％、0.15％、0.2％、0.25％、0.3％、0.35％、0.4％、0.45％、0.5％、0.55％、0.6％、0.65％、0.7％、0.75％、0.8％、0.85％、0.9％、0.95％或1％。
在优选的实施例中，所述正极材料层中式II所示的化合物的质量百分含量b为0.05％～0.5％。
式II所示的化合物作为电解液添加剂时，会在正极和负极表面同时成膜，导致电池内阻的增加。为解决该问题，本申请将式II所示的化合物添加至正极材料层中，式II所示的化合物在高镍正极材料表面形成的界面膜可以有效地抑制电解液与高镍正极材料之间的电化学氧化反应，大大降低高镍正极材料的释氧，提高活性材料的耐氧化性和结构稳定性，同时由于自身具有含磷官能团，在高镍正极材料表面成膜会提高安全性能。因此，将式I所示的化合物作为正极浆料添加剂一方面可以保留其对高镍正极材料的钝化作用，提高正极的耐氧化性和结构稳定性，进而提高锂离子电池的电化学性能和安全性能，另一方面还可以克服现有技术将其作为电解液添加剂时在正负极同时发生成膜反应而导致电池内阻的增加的问题。
在正极材料层中，若式II所示的化合物的含量过小，则其对正极材料的钝化作用有限，从而对电池性能的改善效果不明显；若式II所示的化合物的含量过多，则会在正极活性材料表面成膜过厚，会增大电池的内阻。
根据本申请的实施例，所述高镍正极材料中Ni元素：(Ni元素+Co元素+M元素)的摩尔比值x为0.7-1。在具体的实施例中，所述高镍正极材料中Ni元素：(Ni元素+Co元素+M元素)的摩尔比值x可以为0.7、0.72、0.75、0.78、0.8、0.82、0.85、0.88、0.9、0.92、0.95、0.98或1。
在优选的实施例中，所述高镍正极材料中Ni元素：(Ni元素+Co元素+M元素)的摩尔比值x为0.8-0.9。
所述高镍正极材料中Ni元素占比是影响正极活性材料的理论比容量的重要因素，当高镍正极材料中Ni元素含量越高时其理论比容量也越高，但其与电解液的氧化反应作用也越强，本申请通过式II所示的化合物在正极材料层中的含量和正极集流体单面的正极材料层的厚度控制能够有效降低正极中镍元素对于正极活性材料和非水电解液稳定性的不利影响；当高镍正极材料中Ni元素占比较低时，所述正极材料层的理论比容量较低，不利于电池能量密度的提升；当高镍正极材料中Ni元素占比过高时，则对于正极和非水电解液的稳定性不利，导致电池的高温循环性能下降，安全性能降低。
根据本申请的实施例，所述正极集流体单面的正极材料层的厚度h为80～140μm。在具体的实施例中，所述正极集流体单面的正极材料层的厚度h可以为80μm、83μm、86μm、90μm、93μm、96μm、100μm、103μm、106μm、110μm、113μm、116μm、120μm、123μm、126μm、 130μm、133μm、136μm或140μm。
在优选的实施例中，所述正极集流体单面的正极材料层的厚度h为100～140μm。
正极材料层的厚度也是锂离子电池设计及制作中的关键技术参数。在相同极片大小下，正极材料层的厚度越大，虽然电池的能量密度增大，但内阻也会增大；而正极材料层的厚度降低，则电池的能量密度降低，不利于商用化应用。
在一些实施例中，所述式I所示的高镍正极材料选自LiNi0.8Co0.1Mn0.1O2、LiNi0.8Co0.1Al0.1O2、LiNi0.81Co0.16Mn0.03O2、LiNi0.81Co0.16Al0.03O2、LiNi0.8Co0.05Mn0.15O2、LiNi0.8Co0.05Al0.15O2、LiNi0.7Co0.1Mn0.2O2、LiNi0.9Co0.05Mn0.05O2、LiNiO2、LiNi0.75Mn0.25O2或LiNi0.85Co0.05Mn0.1O2中的至少一种。
在一些实施例中，所述正极材料层中式I所示的高镍正极材料的质量百分含量b为90.0％～99.2％。
在一些实施例中，所述式II所示的化合物选自磷酸三炔丙酯、二炔丙基甲基磷酸酯、二炔丙基氟代甲基磷酸酯、二炔丙基甲氧基甲基磷酸酯、二炔丙基乙基磷酸酯、二炔丙基丙基磷酸酯、三氟甲基二炔丙基磷酸酯、二炔丙基2,2,2-三氟乙基磷酸酯、二炔丙基3,3,3-三氟丙基磷酸酯、六氟异丙基二炔丙基磷酸酯、磷酸三烯丙酯、二烯丙基甲基磷酸酯、二烯丙基乙基磷酸酯、二烯丙基丙基磷酸酯、三氟甲基二烯丙基磷酸酯、二炔丙基甲醚磷酸酯、二炔丙基氟代甲醚磷酸酯、2,2,2-三氟乙基二烯丙基磷酸酯、二烯丙基3,3,3-三氟丙基磷酸酯或二烯丙基六氟异丙基磷酸酯中的至少一种。
在优选的实施例中，所述式II所示的化合物选自以下化合物中的一种或多种：
在一些实施例中，所述正极材料层还包括有正极粘结剂和正极导电剂，所述正极活性材料、所述式II所示的化合物、所述正极粘结剂和所述正极导电剂共混得到所述正极材料层。
以所述正极材料层的总质量为100％计，所述正极粘结剂的质量百分含量为1-2％，所述正极导电剂的质量百分含量为0.5-2％。
所述正极粘结剂包括聚偏氟乙烯、偏氟乙烯的共聚物、聚四氟乙烯、偏氟乙烯-六氟丙烯的 共聚物、四氟乙烯-六氟丙烯的共聚物、四氟乙烯-全氟烷基乙烯基醚的共聚物、乙烯-四氟乙烯的共聚物、偏氟乙烯-四氟乙烯的共聚物、偏氟乙烯-三氟乙烯的共聚物、偏氟乙烯-三氯乙烯的共聚物、偏氟乙烯-氟代乙烯的共聚物、偏氟乙烯-六氟丙烯-四氟乙烯的共聚物、热塑性聚酰亚胺、聚乙烯及聚丙烯等热塑性树脂；丙烯酸类树脂；羟甲基纤维素钠；聚乙烯醇缩丁醛；乙烯-醋酸乙烯酯共聚物；聚乙烯醇；以及苯乙烯丁二烯橡胶中的一种或多种。
所述正极导电剂包括导电炭黑、导电碳球、导电石墨、导电碳纤维、碳纳米管、石墨烯或还原氧化石墨烯中的一种或多种。
在一些实施例中，所述式II所示的化合物形成于所述正极材料层的表面，或所述式II所示的化合物掺混于所述正极材料层的内部。
当所述式II所示的化合物形成于所述正极材料层的表面时，其制备方式可以参照如下方式：
通过表面涂覆的方式在所述正极材料层的表面形成含有式II所示的化合物的涂层，具体的，可先将正极活性材料、正极导电剂和正极粘结剂分散于有机溶剂中，制备得到正极浆料，将正极浆料涂布、干燥形成正极材料层后，再将式II所示的化合物分散于有机溶剂中，将得到的式II所示的化合物溶液喷涂于正极材料层的表面，干燥去除溶剂后得到包括式II所示化合物的正极材料层。
当所述式II所示的化合物掺混于所述正极材料层的内部时，其制备方式可以参照如下方式：
1、制备所述正极材料层的正极浆料中含有式II所示的化合物，具体的，可将式II所示的化合物、正极活性材料、正极导电剂和正极粘结剂分散于有机溶剂中，制备得到正极浆料，再将正极浆料涂布、干燥形成正极材料层；
2、制备正极材料层后将正极材料层浸润于含有式II所示的化合物的溶液中，使式II所示的化合物渗透至所述正极材料层的内部，干燥去除溶剂后得到包含式II所示化合物的正极材料层。
在一些实施例中，所述正极片还包括正极集流体，所述正极材料层形成于所述正极集流体的表面。
所述正极集流体选自可传导电子的金属材料，优选的，所述正极集流体包括Al、Ni、锡、铜、不锈钢的一种或多种，在更优选的实施例中，所述正极集流体选自铝箔。
本申请的另一实施例提供了一种锂离子电池，包括负极片、非水电解液以及如上所述的正极片。
在一些实施例中，所述非水电解液包括非水有机溶剂，所述非水有机溶剂包括醚类溶剂、腈类溶剂、碳酸酯类溶剂和羧酸酯类溶剂中的一种或多种。
在一些实施例中，醚类溶剂包括环状醚或链状醚，优选为碳原子数3～10的链状醚及碳原 子数3～6的环状醚，环状醚具体可以但不限于是1,3-二氧戊烷(DOL)、1,4-二氧惡烷(DX)、冠醚、四氢呋喃(THF)、2-甲基四氢呋喃(2-CH3-THF)，2-三氟甲基四氢呋喃(2-CF3-THF)中的一种或多种；所述链状醚具体可以但不限于是二甲氧基甲烷、二乙氧基甲烷、乙氧基甲氧基甲烷、乙二醇二正丙基醚、乙二醇二正丁基醚、二乙二醇二甲基醚。由于链状醚与锂离子的溶剂化能力高、可提高离子解离性，因此特别优选粘性低、可赋予高离子电导率的二甲氧基甲烷、二乙氧基甲烷、乙氧基甲氧基甲烷。醚类化合物可以单独使用一种，也可以以任意的组合及比率组合使用两种以上。醚类化合物的添加量没有特殊限制，在不显著破坏本申请高压实锂离子电池效果的范围内是任意的，在非水溶剂体积比为100％中通常体积比为1％以上、优选体积比为2％以上、更优选体积比为3％以上，另外，通常体积比为30％以下、优选体积比为25％以下、更优选体积比为20％以下。在将两种以上醚类化合物组合使用的情况下，使醚类化合物的总量满足上述范围即可。醚类化合物的添加量在上述的优选范围内时，易于确保由链状醚的锂离子离解度的提高和粘度降低所带来的离子电导率的改善效果。另外，负极活性材料为碳素材料的情况下，可抑制因链状醚与锂离子共同发生共嵌入的现象，因此能够使输入输出特性、充放电速率特性达到适当的范围。
在一些实施例中，腈类溶剂具体可以但不限于是乙腈、戊二腈、丙二腈中的一种或多种。
在一些实施例中，碳酸酯类溶剂包括环状碳酸酯或链状碳酸酯，环状碳酸酯具体可以但不限于是碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、γ-丁内酯(GBL)、碳酸亚丁酯(BC)中的一种或多种；链状碳酸酯具体可以但不限于是碳酸二甲酯(DMC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二丙酯(DPC)中的一种或多种。环状碳酸酯的含量没有特殊限制，在不显著破坏本申请锂离子电池效果的范围内是任意的，但在单独使用一种的情况下其含量的下限相对于非水电解液的溶剂总量来说，通常体积比为3％以上、优选体积比为5％以上。通过设定该范围，可避免由于非水电解液的介电常数降低而导致电导率降低，易于使非水电解质电池的大电流放电特性、相对于负极的稳定性、循环特性达到良好的范围。另外，上限通常体积比为90％以下、优选体积比为85％以下、更优选体积比为80％以下。通过设定该范围，可提高非水电解液的氧化/还原耐性，从而有助于提高高温保存时的稳定性。链状碳酸酯的含量没有特殊限定，相对于非水电解液的溶剂总量，通常为体积比为15％以上、优选体积比为20％以上、更优选体积比为25％以上。另外，通常体积比为90％以下、优选体积比为85％以下、更优选体积比为80％以下。通过使链状碳酸酯的含量在上述范围，容易使非水电解液的粘度达到适当范围，抑制离子电导率的降低，进而有助于使非水电解质电池的输出特性达到良好的范围。在组合使用两种以上链状碳酸酯的情况下，使链状碳酸酯的总量满足上述范围即可。
在一些实施例中，还可优选使用具有氟原子的链状碳酸酯类(以下简称为“氟化链状碳酸酯”)。氟化链状碳酸酯所具有的氟原子的个数只要为1以上则没有特殊限制，但通常为6以下、优选4以下。氟化链状碳酸酯具有多个氟原子的情况下，这些氟原子相互可以键合于同一个碳上，也可以键合于不同的碳上。作为氟化链状碳酸酯，可列举，氟化碳酸二甲酯衍生物、氟化碳酸甲乙酯衍生物、氟化碳酸二乙酯衍生物等。
羧酸酯类溶剂包括环状羧酸酯和/或链状碳酸酯。作为环状羧酸酯的例子，可以列举如：γ-丁内酯、γ-戊内酯、δ-戊内酯中的一种或多种。作为链状碳酸酯的例子，可以列举如：乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(EP)、乙酸丁酯、丙酸丙酯(PP)、丙酸丁酯中的一种或多种。
在一些实施例中，砜类溶剂包括环状砜和链状砜，优选地，在为环状砜的情况下，通常为碳原子数3～6、优选碳原子数3～5，在为链状砜的情况下，通常为碳原子数2～6、优选碳原子数2～5的化合物。砜类溶剂的添加量没有特殊限制，在不显著破坏本申请锂离子电池效果的范围内是任意的，相对于非水电解液的溶剂总量，通常体积比为0.3％以上、优选体积比为0.5％以上、更优选体积比为1％以上，另外，通常体积比为40％以下、优选体积比为35％以下、更优选体积比为30％以下。在组合使用两种以上砜类溶剂的情况下，使砜类溶剂的总量满足上述范围即可。砜类溶剂的添加量在上述范围内时，倾向于获得高温保存稳定性优异的电解液。
在优选的实施例中，所述溶剂为环状碳酸酯和链状碳酸酯的混合物。
在一些实施例中，所述非水电解液还包括锂盐，所述锂盐包括LiPF6、LiBOB、LiDFOB、LiPO2F2、LiBF4、LiSbF6、LiAsF6、LiN(SO2CF3)2、LiN(SO2C2F5)2、LiC(SO2CF3)3、LiN(SO2F)2、LiClO4、LiAlCl4、LiCF3SO3、Li2B10Cl10、低级脂肪族羧酸锂盐中的一种或多种。
在优选实施例中，所述锂盐包括LiPF6和辅助锂盐，所述辅助锂盐包括LiBOB、LiDFOB、LiPO2F2、LiBF4、LiSbF6、LiAsF6、LiN(SO2CF3)2、LiN(SO2C2F5)2、LiC(SO2CF3)3、LiN(SO2F)2、LiClO4、LiAlCl4、LiCF3SO3、Li2B10Cl10、低级脂肪族羧酸锂盐中的一种或多种。
在满足上述条件下，在非水电解液中加入LiPF6作为主锂盐，以及上述辅助锂盐的配合，能够进一步提高电池的抗热冲击性能，推测是由于正极中含有的式II所示的化合物少量溶解于非水电解液中，与上述锂盐组合配合具有提高非水电解液稳定性的作用，避免非水电解液的分解产气。
在一些实施例中，所述非水电解液中，所述锂盐的浓度为0.1mol/L-8mol/L。在优选的实施例中，所述非水电解液中，所述电解质盐的浓度为0.5mol/L-4mol/L。具体的，所述锂盐的浓度可以为0.5mol/L、1mol/L、1.5mol/L、2mol/L、2.5mol/L、3mol/L、3.5mol/L或4mol/L。
在一些实施例中，所述非水电解液中，所述LiPF6的质量百分含量为5％～20％，所述辅助锂盐的质量百分含量为0.05％～5％。
在一些实施例中，所述非水电解液还包括添加剂，所述添加剂包括环状硫酸酯类化合物、磺酸内酯类化合物、环状碳酸酯类化合物、不饱和磷酸酯类化合物和腈类化合物中的至少一种。
优选的，所述环状硫酸酯类化合物选自硫酸乙烯酯、硫酸丙烯酯或甲基硫酸乙烯酯中的至少一种；
所述磺酸内酯类化合物选自1,3-丙烷磺酸内酯、1,4-丁烷磺酸内酯或1,3-丙烯磺酸内酯中的至少一种；
所述环状碳酸酯类化合物选自碳酸亚乙烯酯、碳酸乙烯亚乙酯、氟代碳酸乙烯酯或式Ⅲ所示化合物中的至少一种，
所述式Ⅲ中，R21、R22、R23、R24、R25、R26各自独立地选自氢原子、卤素原子、C1-C5基团中的一种；
所述不饱和磷酸酯类化合物选自式Ⅳ所示化合物中的至少一种：
所述式Ⅳ中，R31、R32、R33各自独立的选自C1-C5的饱和烃基、不饱和烃基、卤代烃基、-Si(CmH2m+1)3，m为1～3的自然数，且R31、R32、R33中至少有一个为不饱和烃基；
在优选的实施例中，所述不饱和磷酸酯类化合物可为磷酸三炔丙酯、二炔丙基甲基磷酸酯、二炔丙基乙基磷酸酯、二炔丙基丙基磷酸酯、二炔丙基三氟甲基磷酸酯、二炔丙基-2,2,2-三氟乙基磷酸酯、二炔丙基-3,3,3-三氟丙基磷酸酯、二炔丙基六氟异丙基磷酸酯、磷酸三烯丙酯、二烯丙基甲基磷酸酯、二烯丙基乙基磷酸酯、二烯丙基丙基磷酸酯、二烯丙基三氟甲基磷酸酯、二烯丙基-2,2,2-三氟乙基磷酸酯、二烯丙基-3,3,3-三氟丙基磷酸酯、二烯丙基六氟异丙基磷酸酯中的至少一种。
所述腈类化合物包括丁二腈、戊二腈、乙二醇双(丙腈)醚、己烷三腈、己二腈、庚二腈、辛 二腈、壬二腈、癸二腈中的一种或多种。
在另一些实施例中，所述添加剂还可包括其它能改善电池性能的添加剂：例如，提升电池安全性能的添加剂，具体如氟代磷酸酯、环磷腈等阻燃添加剂，或叔戊基苯、叔丁基苯等防过充添加剂。
需要说明的是，除非特殊说明，一般情况下，所述添加剂中任意一种可选物质在非水电解液中的添加量为10％以下，例如，所述添加剂在非水电解液中的添加量为0.05-10％的范围内。优选的，添加量为0.1-5％，更优选的，添加量为0.1％～2％。具体的，所述添加剂中任意一种可选物质的添加量可以为0.05％、0.08％、0.1％、0.5％、0.8％、1％、1.2％、1.5％、1.8％、2％、2.2％、2.5％、2.8％、3％、3.2％、3.5％、3.8％、4％、4.5％、5％、5.5％、6％、6.5％、7％、7.5％、7.8％、8％、8.5％、9％、9.5％、10％。
在一些实施例中，当添加剂选自氟代碳酸乙烯酯时，以所述非水电解液的总质量为100％计，所述氟代碳酸乙烯酯的添加量为0.05％～30％。
在一些实施例中，所述负极片包括负极材料层，所述负极材料层包括负极活性材料，所述负极活性材料选自硅基负极、碳基负极、锂基负极和锡基负极中的至少一种。
其中，所述硅基负极包括硅材料、硅的氧化物、硅碳复合材料以及硅合金材料中的一种或多种；所述碳基负极包括石墨、硬碳、软碳、石墨烯、中间相碳微球中的一种或多种；所述锂基负极金属锂或锂合金中的一种或多种。所述锂合金具体可以是锂硅合金、锂钠合金、锂钾合金、锂铝合金、锂锡合金和锂铟合金中的至少一种。所述锡基负极包括锡、锡碳、锡氧、锡金属化合物中的一种或多种。
在一些实施例中，所述负极材料层还包括有负极粘结剂和负极导电剂，所述负极活性材料、所述负极粘结剂和所述负极导电剂共混得到所述负极材料层。
所述负极粘接剂和负极导电剂的可选择范围分别与所述正极粘结剂和正极导电剂相同，在此不再赘述。
在一些实施例中，所述负极片还包括负极集流体，所述负极材料层形成于所述负极集流体的表面。
所述负极集流体选自可传导电子的金属材料，优选的，所述负极集流体包括Al、Ni、锡、铜、不锈钢的一种或多种，在更优选的实施例中，所述负极集流体选自铜箔。
在一些实施例中，所述锂离子电池中还包括有隔膜，所述隔膜位于所述正极片和所述负极片之间。
所述隔膜可为现有常规隔膜，可以是聚合物隔膜、无纺布等，包括但不限于单层PP(聚丙烯)、单层PE(聚乙烯)、双层PP/PE、双层PP/PP和三层PP/PE/PP等隔膜。
以下通过实施例对本申请进行进一步的说明。
以下实施例和对比例涉及的化合物如下表1所示：
表1
表2实施例和对比例各参数设计

实施例1
本实施例用于说明本申请公开的锂离子电池及其制备方法，包括以下操作步骤：
1)正极片的制备
第1步：在NMP溶剂中，加入作为粘结剂的PVDF及表2所示的式II所示的化合物，充分搅拌均匀，获得添加有式II所示的化合物的PVDF胶液。
第2步：在PVDF胶液中，加入作为导电剂(super P+CNT)，充分搅拌均匀。
第3步：继续加入表2所示的正极活性材料，充分搅拌均匀，最终获得所需要的正极浆料。
第4步：将制备的正极浆料均匀地涂布在正极集流体(例如铝箔)上，经干燥、辊压、模切或分条获得正极片，正极集流体单面形成的正极材料层的厚度如表2所示。
2)负极片的制备
第1步：按石墨(上海杉杉，FSN-1):导电碳(super P):羧甲基纤维素钠(CMC):丁苯橡胶(SBR) ＝96.3:1.0:1.2:1.5(质量比)的配比称取各物质。
第2步：将CMC按照1.5％的固含量加入到纯水中，充分搅拌均匀(例如搅拌时间120min)，制备出透明的CMC胶液。
第3步：在CMC胶液中，加入导电碳(super P)，充分搅拌均匀(例如搅拌时间90min)，制备导电胶。
第4步：继续加入石墨，充分搅拌均匀，最终获得所需要的负极浆料。
第5步：将制备的负极浆料均匀地涂布在铜箔上，经干燥、辊压、模切或分条获得负极片。
3)非水电解液的制备
将碳酸乙烯酯(EC)、碳酸二乙酯(DEC)和碳酸甲乙酯(EMC)按质量比为EC:DEC:EMC＝1:1:1进行混合，然后加入六氟磷酸锂(LiPF6)和二氟磷酸锂(LiPO2F2)，LiPF6的摩尔浓度为1mol/L，LiPO2F2的含量为1％。
4)锂离子电芯制备
将上述制备好的正极片与上述负极片组装成叠片式的软包电芯。
5)电芯的注液和化成
在露点控制在-40℃以下的手套箱中，将上述制备的电解液注入电芯中，经真空封装，静止24h。然后按以下步骤进行首次充电的常规化成：0.05C恒流充电180min,0.2C恒流充电至3.95V，二次真空封口，然后进一步以0.2C的电流恒流充电至4.2V，常温搁置24h后，以0.2C的电流恒流放电至3.0V。
实施例2～23
实施例2～23用于说明本申请公开的锂离子电池及其制备方法，包括实施例1中大部分操作步骤，其不同之处在于：
采用表2所示的正极片组分和电解液添加组分。
对比例1～25
对比例1～25用于对比说明本申请公开的锂离子电池及其制备方法，包括实施例1中大部分操作步骤，其不同之处在于：
采用表2所示的正极片组分和电解液添加组分。
性能测试
对上述制备得到的锂离子电池进行如下性能测试：
将制备的锂离子电池置于恒温45℃的烘箱中，以1C的电流恒流充电至4.2V，再恒流恒压充电至电流下降至0.05C，然后以1C的电流恒流放电至3.0V，如此循环，记录第1周的初始放电容量和内阻，当电池的放电容量下降至初始放电容量的80％时，记录电池的循环圈数。
(1)实施例1～8和对比例1～21得到的测试结果填入表3。
表3
由实施例1～8和对比例1～21的测试结果可知，锂离子电池在正极活性材料类型相同的情况下，正极材料层中式II所示的化合物的质量百分含量b、高镍正极材料中Ni元素：(Ni元素+Co元素+M元素)的摩尔比值x和正极集流体单面的正极材料层的厚度h满足预设关系0.05≤(b/10)*(h/x)≤15时，锂离子电池同时具有优异的阻抗、高温循环性能和初始容量发挥，推测是由于式II所示的化合物与高镍正极材料在条件下具有较好的协同效应，在高镍正极材料的表面形成了性质较为稳定的界面膜，提高了高镍正极材料的结构稳定性和耐氧化性，同时也对非水电解液与高镍正极材料之间形成有效隔离，降低非水电解液的持续分解，进而保证高镍正极材料的界面膜厚度的一致性，该厚度下的界面膜具有较低的阻抗和较好的高温稳定性，从而提高了锂离子电池的高温循环寿命。
由实施例1～8的测试结果可知，随着(b/10)*(h/x)值的增大，锂离子二次电池的初始容量、高温循环性能和阻抗性能先提升后降低，说明正极材料层中式II所示的化合物的质量百分含量b、高镍正极材料中Ni元素：(Ni元素+Co元素+M元素)的摩尔比值x和正极集流体单面的正极材料层的厚度h与锂离子电池的电化学性能相关，尤其是，当0.08≤(b/10)*(h/x)≤8时，锂离子二次电池具有最佳的初始容量、高温循环性能和耐热冲击性能。
由对比例1-8，10和12的测试结果可知，当正极片中不加入结构式1所示的化合物，锂离子二次电池中正极片Ni的摩尔含量较高，在相同正极活性层厚度下，电池的能量密度较高，但内阻和循环性能更差；其次，在正极片Ni元素的摩尔含量相同下，正极活性层厚度与能量密度呈正相关，与阻抗呈负相关，表明正极活性层厚度会直接影响电池内阻和循环性能。由对比例9、11和14～17的测试结果可知，在极片加入结构式1所示的化合物，即使正极材料层中式II所示的化合物的质量百分含量b、高镍正极材料中Ni元素：(Ni元素+Co元素+M元素)的摩尔比值x和正极集流体单面的正极材料层的厚度h之间的关系满足条件0.05≤(b/10)*(h/x)≤15；但b值、x值、x值和h值不满足其范围限定时，锂离子电池仍然不具有较好的电化学性能。
由对比例13和实施例1的测试结果可知，当式II所示的化合物添加至非水电解液中，对于电池的性能提升幅度远不如在将式II所示的化合物添加至正极材料层中时对电池的性能提升幅度，这可能是因为式II所示的化合物的粘度较大，电导率较低，加入到电解液中会影响电池的容量、内阻和循环等性能。
(2)实施例9～15得到的测试结果填入表4。
表4
由实施例9-15的测试结果可知，采用其他高镍材料(X＝0.7，0.75，0.85，0.9，1)作为正极活性材料，当正极材料层中式II所示的化合物的质量百分含量b、高镍正极材料中Ni元素：(Ni元素+Co元素+M元素)的摩尔比值x和正极集流体单面的正极材料层的厚度h满足预设关系0.05≤(b/10)*(h/x)≤15时，电池同样具有较好的高温循环性能和初始容量，说明本申请提供的关系式对于采用不同的高镍正极材料的锂离子电池高温性能均具有普适性的提高。
(3)实施例16～19和对比例22～25得到的测试结果填入表5。
表5
由实施例16～19和对比例22～25的测试结果可知看出，在含有本申请提供的正极的电池中，在非水电解液中加入上述的添加剂DTD(硫酸乙烯酯)、VC(碳酸乙烯酯)或PS(1,3-丙烷磺内酯)对于能够进一步提高电池的高温循环性能，以及降低热冲击测试中电池的最高表面温度，推测是由于正极中的结构式1所示的化合物与上述的添加剂共同参与了电极表面钝化膜的成型，得到一种热稳定性能优异的钝化膜，进而有效降低了电极表面电解液的反应，提高了电池的电化学性能。
(4)实施例20～23得到的测试结果填入表6。
表6
由实施例20～23的测试结果可知看出，对于不同的结构式1所示的化合物，正极材料层中式II所示的化合物的质量百分含量b、高镍正极材料中Ni元素：(Ni元素+Co元素+M元素)的摩尔比值x和正极集流体单面的正极材料层的厚度h满足预设关系0.05≤(b/10)*(h/x)≤15时，其起到的作用相似，均对于锂离子电池的电池容量和循环性能具有一定的改善作用，说明本申请提供的关系式适用于不同的结构式1所示的化合物。
以上所述仅为本申请的较佳实施例而已，并不用以限制本申请，凡在本申请的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本申请的保护范围之内。

Claims (13)

  1. 一种正极片，包括正极集流体和形成于所述正极集流体上的正极材料层，其中所述正极材料层包括式I所示的高镍正极材料和式II所示的化合物：
    LiaNiqCoyMzO2  式I
    其中，0.9≤a≤1.2，0.7≤q≤1，y≥0，z≥0，且q+y+z＝1，M选自Mn及Al中的一种或两种；
    其中，R1、R2、R3各自独立地选自1-5个碳原子的烷基、1-5个碳原子的氟代烷基、1-5个碳原子的醚基、1-5个碳原子的氟代醚基、2-5个碳原子的不饱和烃基，且R1、R2、R3中的至少一个为2-5个碳原子的不饱和烃基；
    所述正极片满足以下条件：
    0.05≤(b/10)*(h/x)≤15；
    且0.005≤b≤1，0.7≤x≤1，80≤h≤140；
    其中，b为正极材料层中式II所示的化合物的质量百分含量，单位为％；
    x为高镍正极材料中Ni元素：(Ni元素+Co元素+M元素)的摩尔比值；
    h为正极集流体单面的正极材料层的厚度，单位为μm；
    所述正极片在溶剂中超声震荡后所得的溶液进行液相色谱-质谱联用仪(LC-MS)分析，在保留时间为6.5min～7.5min的区域出现特征峰。
  2. 根据权利要求1所述的正极片，其中所述正极片满足以下条件：
    0.08≤(b/10)*(h/x)≤8。
  3. 根据权利要求1或2所述的正极片，其中所述正极材料层中式II所示的化合物的质量百分含量b为0.05％～0.5％。
  4. 根据权利要求1至3中任一项所述的正极片，其中所述高镍正极材料中Ni元素：(Ni元素+Co元素+M元素)的摩尔比值x为0.8-0.9。
  5. 根据权利要求1至4中任一项所述的正极片，其中所述正极集流体单面的正极材料层的厚度h为100～140μm。
  6. 根据权利要求1至5中任一项所述的正极片，其中所述式I所示的高镍正极材料选自LiNi0.8Co0.1Mn0.1O2、LiNi0.8Co0.1Al0.1O2、LiNi0.81Co0.16Mn0.03O2、LiNi0.81Co0.16Al0.03O2、LiNi0.8Co0.05Mn0.15O2、LiNi0.8Co0.05Al0.15O2、LiNi0.7Co0.1Mn0.2O2、LiNi0.9Co0.05Mn0.05O2、LiNiO2、LiNi0.75Mn0.25O2或LiNi0.85Co0.05Mn0.1O2中的至少一种。
  7. 根据权利要求1至6中任一项所述的正极片，其中所述正极材料层中式I所示的高镍正极材料的质量百分含量b为90.0％～99.2％。
  8. 根据权利要求1至7中任一项所述的正极片，其中1-5个碳原子的烷基选自甲基、乙基、正丙基、异丙基、正丁基、异丁基、仲丁基、叔丁基、正戊基、异戊基、仲戊基或新戊基；1-5个碳原子的氟代烷基选自该1-5个碳原子的烷基中的一个或多个氢元素被氟元素取代所得的基团；
    2-5个碳原子的不饱和烃基选自乙烯基、丙烯基、烯丙基、丁烯基、戊烯基、甲基乙烯基、甲基烯丙基、乙炔基、丙炔基、炔丙基、丁炔基或戊炔基；
    1-5个碳原子的醚基选自甲醚、***、甲***、丙醚、甲丙醚或乙丙醚；
    1-5个碳原子的氟代醚基选自氟代甲醚、氟代***、氟代甲***、氟代丙醚、氟代甲丙醚或氟代乙丙醚。
  9. 根据权利要求1至8中任一项所述的正极片，其中所述式II所示的化合物选自磷酸三炔丙酯、二炔丙基甲基磷酸酯、二炔丙基氟代甲基磷酸酯、二炔丙基甲氧基甲基磷酸酯、二炔丙基乙基磷酸酯、二炔丙基丙基磷酸酯、三氟甲基二炔丙基磷酸酯、二炔丙基2,2,2-三氟乙基磷酸酯、二炔丙基3,3,3-三氟丙基磷酸酯、六氟异丙基二炔丙基磷酸酯、磷酸三烯丙酯、二烯丙基甲基磷酸酯、二烯丙基乙基磷酸酯、二烯丙基丙基磷酸酯、三氟甲基二烯丙基磷酸酯、二炔丙基甲醚磷酸酯、二炔丙基氟代甲醚磷酸酯、2,2,2-三氟乙基二烯丙基磷酸酯、二烯丙基3,3,3-三氟丙基磷酸酯或二烯丙基六氟异丙基磷酸酯中的至少一种。
  10. 一种锂离子电池，包括负极片、非水电解液以及如权利要求1至9中任一项所述的正极片。
  11. 根据权利要求10所述的锂离子电池，其中所述非水电解液包括添加剂，所述添加剂包括环状硫酸酯类化合物、磺酸内酯类化合物、环状碳酸酯类化合物、不饱和磷酸酯类化合物和腈类化合物中的至少一种。
  12. 根据权利要求11所述的锂离子电池，其中所述环状硫酸酯类化合物选自硫酸乙烯酯、硫酸丙烯酯或甲基硫酸乙烯酯中的至少一种；
    所述磺酸内酯类化合物选自1,3-丙烷磺酸内酯、1,4-丁烷磺酸内酯或1,3-丙烯磺酸内酯中的至少一种；
    所述环状碳酸酯类化合物选自碳酸亚乙烯酯、碳酸乙烯亚乙酯、氟代碳酸乙烯酯或式III所示化合物中的至少一种，
    所述式III中，R21、R22、R23、R24、R25、R26各自独立地选自氢原子、卤素原子、C1-C5基团中的一种；
    所述不饱和磷酸酯类化合物选自式IV所示化合物中的至少一种：
    所述式IV中，R31、R32、R33各自独立的选自C1-C5的饱和烃基、不饱和烃基、卤代烃基、-Si(CmH2m+1)3，m为1～3的自然数，且R31、R32、R33中至少有一个为不饱和烃基；
    所述腈类化合物包括丁二腈、戊二腈、乙二醇双(丙腈)醚、己烷三腈、己二腈、庚二腈、辛二腈、壬二腈、癸二腈中的一种或多种。
  13. 根据权利要求11或12所述的锂离子电池，其中所述添加剂在所述非水电解液中的添加量在0.05-10％的范围内。
PCT/CN2023/080937 2022-03-17 2023-03-10 正极片及锂离子电池 WO2023174185A1 (zh)

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