WO2023133811A1 - 一种单晶低钴三元材料及其制备方法、二次电池、电池包、用电装置 - Google Patents

一种单晶低钴三元材料及其制备方法、二次电池、电池包、用电装置 Download PDF

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WO2023133811A1
WO2023133811A1 PCT/CN2022/072067 CN2022072067W WO2023133811A1 WO 2023133811 A1 WO2023133811 A1 WO 2023133811A1 CN 2022072067 W CN2022072067 W CN 2022072067W WO 2023133811 A1 WO2023133811 A1 WO 2023133811A1
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positive electrode
cobalt
low
active material
oxide
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PCT/CN2022/072067
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English (en)
French (fr)
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倪欢
别常峰
尹翔
欧阳少聪
董苗苗
柳娜
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宁德时代新能源科技股份有限公司
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Priority to EP22919465.9A priority Critical patent/EP4273956A1/en
Priority to CN202280021332.0A priority patent/CN117043982A/zh
Priority to PCT/CN2022/072067 priority patent/WO2023133811A1/zh
Priority to US18/324,592 priority patent/US20230327100A1/en
Publication of WO2023133811A1 publication Critical patent/WO2023133811A1/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
    • H01M4/36—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
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • C—CHEMISTRY; METALLURGY
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    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
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    • C—CHEMISTRY; METALLURGY
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    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Nickelates
    • C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
    • C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/50—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese of the type [MnO2]n-, e.g. Li(NixMn1-x)O2, Li(MyNixMn1-x-y)O2
    • H—ELECTRICITY
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    • 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
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    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
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    • 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
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • 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
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • C—CHEMISTRY; METALLURGY
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    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
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    • C01P2002/52—Solid solutions containing elements as dopants
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
    • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
    • C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
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    • C01P2006/40—Electric properties
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • 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

  • the present application relates to the technical field of lithium-ion batteries, in particular to a single-crystal low-cobalt ternary material.
  • the present application also relates to a secondary battery comprising the single crystal low-cobalt ternary material, a battery pack comprising the secondary battery, a battery module and an electrical device.
  • lithium-ion batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, Military equipment, aerospace and other fields.
  • energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, Military equipment, aerospace and other fields.
  • their acceleration performance and cruising range at low temperatures need to be improved to meet greater market demand.
  • lithium-ion batteries it is more effective to use lithium iron phosphate and nickel-cobalt-lithium manganese oxide ternary materials as positive electrode active materials.
  • nickel-cobalt lithium manganese oxide is the best choice.
  • the cost of this material is high due to the high cobalt content, and the cycle performance of lithium-ion batteries will be reduced under low-temperature and high-voltage conditions. Reduced, shortened lifespan and other issues. Therefore, there is an urgent need for a positive electrode active material, which can enable lithium-ion batteries to have improved electrochemical performance at low temperature and high voltage, and reduce manufacturing costs.
  • the present application is made in view of the above problems, and its purpose is to provide a low-cobalt ternary positive electrode active material, so that the secondary battery has improved power and cycle performance and lower cost under low temperature and high voltage.
  • the present application provides a low-cobalt ternary positive electrode material with a single crystal structure, which is characterized in that,
  • the ratio between the average Co content per unit area of the outer layer and the average Co content per unit area of the inner core In the range of 1.2-5.0:1, optionally in the range of 1.4-2.0:1, wherein the outer layer is the region from the surface of the particle to a depth of 200 nm towards the geometric center of the particle, the The inner core is a spherical region with a diameter of 200 nm centered on the geometric center of the particle. Further, the material particles have a radius of at least 300 nm, optionally 400 to 4000 nm.
  • the present application effectively improves the structural stability and dynamic properties of the positive electrode material at low temperature and high voltage by obtaining a single crystal low-cobalt ternary material that satisfies the above relational formula and has a higher content of Co in the outer layer than in the inner core.
  • the cycle performance and power of the secondary battery at low temperature and high voltage are improved.
  • the particles of the low-cobalt ternary positive electrode material also have a coating layer, and the coating layer is an oxide containing Q, wherein Q is selected from Zr, Sr, B, Ti, Mg , one or more of Sn and Al. This is beneficial to reduce the side reaction between the surface of the positive electrode active material and the electrolyte, thereby improving the stability and safety performance of the battery.
  • the low-cobalt ternary cathode material in the chemical formula of the low-cobalt ternary cathode material, 0.5 ⁇ a ⁇ 0.7. This is beneficial for the low-cobalt ternary cathode material to have a higher specific capacity under high voltage and maintain better chemical stability.
  • the median particle diameter Dv 50 of the low-cobalt ternary cathode material is in the range of 1.6 ⁇ m-3.6 ⁇ m, optionally in the range of 1.8 ⁇ m-3.5 ⁇ m. This can improve the lithium ion deintercalation ability and improve the electrochemical performance of the battery.
  • the low-cobalt ternary positive electrode material is characterized in that the content of Q is 500-5000ppm, based on the Q element in the Q-containing oxide relative to the low-cobalt ternary positive electrode with a coating layer Material meter. It is beneficial to improve the structural stability of the positive electrode active material and reduce gas and heat production.
  • the second aspect of the present application provides a method for preparing a low-cobalt ternary positive electrode material, which is characterized in that it includes:
  • Step S2 mixing and sintering the active material particle precursor 1 and a Co-containing compound to obtain an active material particle precursor 2 with a Co-rich surface layer; tempering treatment to obtain a low-cobalt ternary positive electrode material;
  • the ratio between the average Co content per unit area of the outer layer and the average Co content per unit area of the inner core In the range of 1.2-5.0:1, optionally in the range of 1.4-2.0:1, wherein the outer layer is the region from the surface of the particle to a depth of 200 nm towards the geometric center of the particle, the The inner core is a spherical region with a diameter of 200 nm centered on the geometric center of the particle. Further, the material particles have a radius of at least 300 nm, optionally 400 to 4000 nm.
  • the method for preparing the low-cobalt ternary positive electrode active material of the present invention has a simple preparation process, is easy to realize, and has low cost, and can be applied in industrial production on a large scale.
  • the M-containing compound described in step S1 is one or more selected from magnesium oxide, strontium oxide, titanium oxide, tin oxide, zirconium oxide, aluminum oxide, and boron oxide. Zirconia, strontium oxide or magnesium oxide are selected.
  • the sintering temperature is in the range of 800°C-960°C
  • the sintering time is 5-15h
  • the sintering atmosphere is air or O 2 . This is conducive to the fusion between particles and increases the particle size.
  • the step S2 further includes a step S2a: coating the Co-rich active material particle precursor 2 with an oxide containing Q.
  • the oxide containing Q in step S2a is one or more selected from aluminum oxide, tin oxide, zirconium oxide, boron oxide, and titanium oxide, and titanium oxide is optional.
  • the Co-containing compound in step S2 is one or more selected from cobalt hydroxide, cobalt oxyhydroxide, cobalt oxide, cobalt acetate or cobalt oxalate.
  • the addition amount of the compound containing Co makes the molar amount of Co added therein equal to the total molar amount of metal elements Ni, Co, Mn in the positive active material precursor obtained in step S1 The ratio is 0.005-0.05:1, optionally 0.01-0.03:1.
  • the sintering temperature in step S2 is in the range of 650-750°C, optionally in the range of 700-720°C, the sintering time is 2-8h, optionally 4-5h, and the sintering atmosphere is Air or O 2 .
  • a positive electrode active material having a non-uniformly distributed Co element is thus obtained.
  • the third aspect of the present application provides a secondary battery, comprising the single crystal low-cobalt positive electrode active material of the first aspect of the present application or the single crystal low-cobalt positive electrode active material prepared according to the method of the second aspect of the present application.
  • a fourth aspect of the present application provides a battery module including the secondary battery of the third aspect of the present application.
  • a fifth aspect of the present application provides a battery pack, including the battery module of the fourth aspect of the present application.
  • the sixth aspect of the present application provides an electric device, including at least one selected from the secondary battery of the third aspect of the present application, the battery module of the fourth aspect of the present application, or the battery pack of the fifth aspect of the present application. kind.
  • the secondary battery made of the single crystal low cobalt positive electrode active material of the present invention is It has improved cycle performance and power performance at low temperature and high voltage, and has a long battery life.
  • the battery pack, battery module and electrical device provided by the present application also have good cycle capability and long-term endurance capability at low temperature and high voltage.
  • FIG. 1 shows a SEM image of the low-cobalt positive electrode active material of Example 1 of the present application.
  • Fig. 2 shows the Co element line scan diagram (Fig. 2A) of the low-cobalt cathode active material of the present application, and the radial distribution of Co element content (mass fraction) (Fig. 2B).
  • Fig. 3 shows a volume average particle size distribution diagram of an embodiment of the present application.
  • FIG. 4 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 7 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 8 is an exploded view of the battery pack according to one embodiment of the present application shown in FIG. 7 .
  • FIG. 9 is a schematic diagram of an electrical device according to an embodiment of the present application.
  • ranges disclosed herein are defined in terms of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined arbitrarily, ie any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-6.
  • the numerical range "a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence.
  • steps (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b) and so on.
  • the “comprising” and “comprising” mentioned in this application mean open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).
  • nickel-cobalt-lithium-manganese oxide ternary materials with a secondary ball structure have better low-temperature performance due to their smaller primary particles; however, under high voltage ( ⁇ 4.3V), the secondary ball particles are prone to cracking, resulting in rapid capacity. decline.
  • the nickel-cobalt-lithium manganese oxide ternary material with a single crystal structure is not easy to crack and is more suitable for high-voltage applications, but its primary particles are larger, and its low-temperature performance is often worse than that of the ternary secondary ball.
  • the cobalt content in the commercially available nickel-cobalt lithium manganese oxide ternary material is relatively high, because it is beneficial to reduce the Li/Ni mixing ratio of the surface layer of the positive electrode active material, and accelerate the lithium ion deintercalation rate, thereby further improving the single Kinetic properties of crystalline low-cobalt ternary cathode materials. But the cost is too high due to the high price of Co.
  • the inventors developed a low-cost single crystal structure nickel-cobalt-lithium manganese oxide ternary material that can improve the cycle performance and power of the battery at low temperature and high voltage. Crystalline low-cobalt ternary cathode material.
  • the first aspect of the present application provides a low-cobalt ternary positive electrode material with a single crystal structure, characterized in that,
  • the ratio between the average Co content per unit area of the outer layer and the average Co content per unit area of the inner core In the range of 1.2-5.0:1, optionally in the range of 1.4-2.0:1, wherein the outer layer is the region from the surface of the particle to a depth of 200 nm towards the geometric center of the particle, the The inner core is a spherical region with a diameter of 200 nm centered on the geometric center of the particle. Further, the material particles have a radius of at least 300 nm, optionally 400 to 4000 nm.
  • the low-cobalt ternary positive electrode material has a single crystal structure.
  • single crystal refers to a morphology of particles, which is usually in the form of dispersed single particles (micron-sized) , with fewer grain boundaries; and secondary spherical particles are usually agglomerated by many particles (100-500 nanometers) to form a spherical shape, with a lot of grain boundaries.
  • the single crystal ternary positive electrode material is a powder mainly composed of monodisperse primary particles, which means that these primary particles are separated and independent from each other. More importantly, this single-crystal structure ternary cathode material is suitable for high voltage ( ⁇ 4.3V), has the advantages of high energy density, and is not easy to crack, which is not available in polycrystalline secondary ball ternary materials.
  • unit area refers to an area of the same size in the outer layer and the inner core, usually 1 square nanometer, which can also be selected according to actual test conditions.
  • the Co content means that in a single particle of a single crystal low-cobalt ternary material, on a cross-section passing through the geometric center of the single particle, the mass of the Co element contained in a unit area accounts for 1% of the unit area. The percentage of the total mass of crystal low cobalt ternary material.
  • the ratio of the mole fraction of Li element to the total mole fraction of Ni, Co and Mn is in the range of (1.67-1):1, optionally in (1.10-1.01) : In the range of 1, this is because when the sintering temperature is high, it is necessary to increase the excess lithium to compensate; and, the molar ratio is in this range, which is beneficial to obtain a single crystal material with higher specific energy.
  • the mole fraction of Co is 0.05 ⁇ b ⁇ 0.14, which is lower than the Co content (at least 0.15) of commercially available common ternary material products (such as NCM333 or NCM523). Therefore, the single-crystal low-cobalt ternary material of the present invention reduces the consumption of cobalt, thereby reducing product cost.
  • the mole fractions of Ni, Co and Mn should satisfy the following relationship: 3.5 ⁇ a/b ⁇ 15, 0.02 ⁇ b ⁇ c/a 2 ⁇ 0.21, which is conducive to obtaining a low-cobalt ternary single crystal material with stable crystal structure.
  • the mole fraction of the M element is not greater than 0.1, optionally, in the range of 0.001 to 0.005, which is conducive to more effectively stabilizing the positive electrode active material
  • the structure improves the transport performance of lithium ions in the positive electrode active material particles, thereby improving the cycle performance of the battery;
  • the molar fraction of element A is not greater than 0.2, and the positive electrode active material can be further improved by adding A element with stronger electronegativity in the positive electrode active material.
  • the structural stability is conducive to improving the cycle performance of the battery.
  • the inventors have found that the single crystal low-cobalt ternary material satisfying the above relational formula, if the Co element is unevenly distributed, especially the Co content ratio per unit area in the outer layer and the inner core is 1.2-5.0: In the range of 1, optionally in the range of 1.4-2.0:1, a structurally stable low-cobalt ternary cathode material at low temperature and high voltage can be obtained, thereby improving the cycle performance and power of the secondary battery at low temperature and high voltage .
  • the coating layer is an oxide containing Q, wherein Q is selected from Zr, Sr, B, Ti, One or more of Mg, Sn and Al. Further, the thickness of the covering layer is 3-100 nm, optionally 10-180 nm.
  • the single-crystal low-cobalt ternary positive electrode active material of the present invention can be active material particles, and can also be particles composed of the active material particles and the coating layer coated thereon.
  • the coating layer is selected from Q A coating of elemental oxides.
  • the surface of the active material particles By coating the surface of the active material particles with a coating layer containing an oxide of Q element, it is beneficial to reduce the oxidation activity of the electrolyte on the surface of the positive electrode active material, reduce the side reaction of the electrolyte on the surface of the positive electrode active material, and suppress gas production , Reduce heat generation, thereby improving the stability and safety performance of the battery.
  • the surface refers to the interface where the body (such as the active material particles) contacts with the outside world (such as air, water or electrolyte).
  • the low-cobalt ternary cathode material is a particle with a median particle diameter Dv 50 in the range of 1.6 ⁇ m-3.6 ⁇ m, optionally in the range of 1.8 ⁇ m-3.5 ⁇ m.
  • Dv 10 is in the range of 0.9 ⁇ m-1.1 ⁇ m, such as 1.0 ⁇ m;
  • Dv 30 is in the range of 1.4 ⁇ m-1.6 ⁇ m, such as 1.5 ⁇ m;
  • Dv 60 is in the range of 2.4 ⁇ m-2.6 ⁇ m, such as 2.5 ⁇ m.
  • the lithium ion deintercalation ability can be improved, the lithium ion deintercalation rate can be accelerated, and the electrochemical performance of the battery at low temperature can be improved.
  • the content of Q in the coating layer of the low-cobalt ternary positive electrode material is 500-5000ppm, based on the Q element in the Q-containing oxide relative to the single crystal low-cobalt three Yuan cathode material meter.
  • the second aspect of the present application provides a method for preparing a low-cobalt ternary positive electrode material, characterized in that it includes:
  • Step S2 mixing and sintering the active material particle precursor 1 and a Co-containing compound to obtain an active material particle precursor 2 with a Co-rich surface layer; tempering treatment to obtain a low-cobalt ternary positive electrode material;
  • the low-cobalt ternary cathode material is a single crystal structure
  • the ratio between the average Co content per unit area of the outer layer and the average Co content per unit area of the inner core In the range of 1.2-5.0:1, optionally in the range of 1.4-2.0:1, wherein the outer layer is the region from the surface of the particle to a depth of 200 nm towards the geometric center of the particle, the The inner core is a spherical region with a diameter of 200 nm centered on the geometric center of the particle. Further, the material particles have a radius of at least 300 nm, optionally 400 to 4000 nm.
  • the positive electrode active material provided by the embodiment of the present invention has a simple preparation process, is easy to implement, and has low cost, and can be applied in industrial production on a large scale.
  • the positive electrode active material precursor can be prepared by co-precipitation method, gel method or solid phase method.
  • the preparation method of the positive electrode active material precursor includes the following steps:
  • the Ni source is a soluble nickel salt.
  • the nickel salt is selected from nickel sulfate, nickel nitrate, nickel chloride, nickel oxalate or nickel acetate, and any mixture thereof, optionally selected from nickel sulfate and/or nickel nitrate, and further optionally nickel sulfate.
  • the Co source is a soluble cobalt salt.
  • the cobalt salt is selected from cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt oxalate or cobalt acetate, and any mixture thereof, optionally selected from cobalt sulfate and/or cobalt nitrate, and further optionally cobalt sulfate.
  • the Mn source is a soluble manganese salt.
  • the specific type of manganese salt is not particularly limited, and can be selected according to actual needs.
  • the manganese salt is selected from manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate or manganese acetate, and any mixture thereof, optionally selected from manganese sulfate and/or manganese nitrate, further optionally manganese sulfate.
  • the molar ratio of Ni source, Co source and Mn source is 1:(0.04-0.4):(0.2-0.7), optionally 1:(0.05-0.3):(0.25-0.65).
  • the above-mentioned solvent is not particularly limited as long as it can dissolve the Ni source, the Co source and the Mn source.
  • the solvent is selected from water, methanol, ethanol, acetone, isopropanol or n-hexanol, and any mixed solvent thereof, wherein the water can be one or more of deionized water, distilled water, mineral water and tap water, An example is deionized water.
  • the mixed solution is an aqueous solution containing nickel, cobalt, and manganese ions, and generally can be an aqueous solution of nickel sulfate, manganese sulfate, and cobalt sulfate.
  • the concentration of the mixed solution is 1.5 mol/L ⁇ 3.5 mol/L, such as 2.0 mol/L ⁇ 2.9 mol/L.
  • the concentration of the Co source in the mixed solution is 0.05 to 1.0 mol/L, optionally 0.06 to 0.6 mol/L.
  • a reaction system can be formed by adding a precipitating agent and a complexing agent to the mixed solution, adjusting the concentration of the complexing agent and the concentration of the precipitating agent in the reaction system, and adjusting the pH of the reaction system to be 10-12, A co-precipitation reaction is performed to obtain a positive electrode active material precursor, such as [ Nia Co b Mn c ](OH) 2 .
  • the precipitation agent may be one or more of LiOH, NaOH and KOH, such as NaOH.
  • the precipitation agent is in the form of a solution, wherein the solvent can be one or more of water, methanol, ethanol, acetone, isopropanol and n-hexanol, and the aforementioned water can be deionized water, distilled water, mineral water and tap water One or more of them, such as deionized water.
  • the concentration of the precipitant solution is not particularly limited, and can be selected according to actual needs.
  • the concentration of NaOH is 0.5-5 mol/L, such as 1 mol/L.
  • the complexing agent may be one or more of ammonia water, ammonium sulfate, ammonium nitrate, ammonium chloride, ammonium citrate and disodium ethylenediaminetetraacetic acid (EDTA).
  • the complexing agent is in the form of a solution, wherein the solvent can be one or more of water, methanol, ethanol, acetone, isopropanol and n-hexanol, and the aforementioned water can be deionized water, distilled water, mineral water and One or more of tap water, such as deionized water.
  • the complexing agent is ammonia water, and there is no special limitation on the concentration of ammonia water, which can be selected according to actual needs.
  • the concentration of ammonia water is 0.1 mol/L-2 mol/L, further 0.2 mol/L-1.5 mol/L, further 0.3 mol/L-1 mol/L, for example 0.4 mol/L.
  • reaction temperature is 40°C-70°C, further 45°C-65°C, and further 50°C-60°C.
  • step S120 the reaction is carried out under an inert gas protective atmosphere and continuous stirring.
  • the inert gas is, for example, one or more selected from nitrogen, argon, and helium.
  • the stirring method is not particularly limited, as long as it can make The reaction system can be stirred evenly. For example, choose mechanical agitation.
  • the stirring rotation speed is, for example, 100 rpm to 800 rpm.
  • the above "rpm" is revolution per minute, which represents the number of rotations of the stirring device per minute.
  • the selected detergent which can be selected according to actual needs, such as washing with deionized water, wherein, the number of times of washing is not particularly limited, as long as the surface of the reaction product can be cleaned.
  • the residual ions can be removed by washing.
  • drying temperature is 100°C to 150°C.
  • the lithium salt is selected from lithium oxide (Li 2 O), lithium phosphate (Li 3 PO 4 ), lithium dihydrogen phosphate (LiH 2 PO 4 ), lithium acetate (CH 3 COOLi), lithium hydroxide (LiOH ), lithium carbonate (Li 2 CO 3 ) or lithium nitrate (LiNO 3 ), and any mixture thereof.
  • the lithium salt is selected from lithium carbonate, lithium hydroxide or lithium nitrate, and any mixture thereof. Further optionally, the lithium salt is lithium carbonate.
  • the compound containing M may be selected from one or more of oxides, nitric acid compounds, carbonic acid compounds, hydroxide compounds and acetic acid compounds containing M elements.
  • the compound containing M is an oxide containing M element, selected from one or more of magnesium oxide, strontium oxide, titanium oxide, tin oxide, zirconium oxide, aluminum oxide and boron oxide; One or more of magnesium, strontium oxide, titanium oxide, zirconium oxide, aluminum oxide and boron oxide; further optionally, one or more selected from strontium oxide, titanium oxide, zirconium oxide, aluminum oxide and boron oxide species; and further optionally, one or more selected from zirconia, strontium oxide and boron oxide.
  • the addition of the positive electrode active material precursor and the M-containing compound is such that the total molar weight of metal elements (Ni, Co, Mn) in the positive electrode active material precursor is equal to
  • Me is the positive electrode active material precursor
  • step S1 the positive electrode active material precursor and the lithium salt are mixed and sintered to obtain active material particles that do not contain the doping element M.
  • the positive electrode active material precursor and lithium salt are mixed with the M-containing compound and sintered to obtain active material particles modified by M at the transition metal site.
  • the positive electrode active material precursor and lithium salt are mixed with M-containing compounds and A-containing compounds and sintered to obtain active material particles modified by M at the transition metal site and doped with A element at the oxygen site .
  • the compound containing A can be selected according to actual needs, such as ammonium fluoride, lithium fluoride, hydrogen fluoride, ammonium chloride, lithium chloride, hydrogen chloride, ammonium bromide, lithium bromide, hydrogen bromide, ammonium iodide, iodide
  • step S1 the sintering is performed in oxygen or air; the sintering temperature is in the range of 800°C to 960°C. There is no special limitation on the sintering time, which can be adjusted according to the actual situation, for example, 5h-15h. The higher sintering temperature is conducive to the fusion between particles and increases the particle size.
  • step S1 there is no particular limitation on the crushing method, which can be selected according to actual needs, for example, jet mill or mechanical mill is used.
  • a jet mill such as a Shenfei jet mill (with a volume of 40m 3 )
  • set the crushing air pressure to 0.2-0.35MPa
  • feed the feed rate to 280-320Kg/h
  • control the feed particle size within 2mm. It is beneficial to further decompose the particles, so as to control the particle size within the desired range.
  • the median diameter of the obtained active material particle precursor 1 is 1.4 ⁇ m-3.4 ⁇ m, optionally 1.6 ⁇ m-3.5 ⁇ m.
  • the step S2 further includes a step S2a: coating the Co-rich active material particle precursor 2 with an oxide containing Q.
  • the positive electrode active material obtained by the method including step S2a includes active material particles and an M element-containing coating layer coated on the surface of the active material particles. Through this covering, in the secondary battery, the contact between the active material particles and the electrolyte can be avoided, so as to ensure the stability of the structure of the positive electrode active material.
  • the oxide containing Q in step S2a is one or more selected from aluminum oxide, tin oxide, zirconium oxide, boron oxide, and titanium oxide, and titanium oxide is optional.
  • the coating treatment can be performed using methods and equipment known in the art, such as dry coating, liquid phase coating, vapor phase deposition coating and the like.
  • a single-crystal low-cobalt positive electrode active material with a covering layer can be obtained, which can avoid contact with electrolyte solution in a secondary battery and stabilize the structure of the single-crystal low-cobalt positive electrode active material.
  • the Co-containing compound in step S2 is one or more selected from cobalt hydroxide, cobalt oxyhydroxide, cobalt oxide, cobalt acetate or cobalt oxalate.
  • step S2 the addition amount of the compound containing Co makes the molar amount of Co added therein equal to the total molar amount of metal elements Ni, Co, Mn in the positive active material precursor obtained in step S1
  • the ratio is 0.005-0.05:1, optionally 0.01-0.03:1.
  • the sintering temperature in step S2 is in the range of 650-750°C, optionally in the range of 700-720°C, the sintering time is 2-8h, optionally 4-5h, and the sintering atmosphere is Air or O 2 .
  • the ratio between the average Co content of the area is in the range of 1.2-5.0:1, optionally in the range of 1.4-2.0:1.
  • the tempering temperature is 400°C-700°C, optionally 450°C-600°C.
  • a secondary battery which includes a positive electrode sheet using the single crystal low-cobalt positive electrode active material of the present application.
  • a secondary battery typically includes a positive pole piece, a negative pole piece, an electrolyte, and a separator.
  • active ions are intercalated and extracted back and forth between the positive electrode and the negative electrode.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows ions to pass through.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode collector, and the positive electrode film layer includes the positive electrode active material according to the first aspect of the present application.
  • the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposing surfaces of the positive electrode current collector.
  • the positive electrode current collector can be a metal foil or a composite current collector.
  • aluminum foil can be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene glycol ester
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode film layer may further optionally include a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode film layer may also optionally include a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the positive electrode sheet, such as positive electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposing surfaces of the negative electrode current collector.
  • the negative electrode current collector can use a metal foil or a composite current collector.
  • copper foil can be used as the metal foil.
  • the composite current collector may include a base layer of polymer material and a metal layer formed on at least one surface of the base material of polymer material.
  • Composite current collectors can be formed by metal materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • the negative electrode active material can be a negative electrode active material known in the art for batteries.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of simple tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials of batteries can also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode film layer may further optionally include a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer may also optionally include a conductive agent.
  • the conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer may optionally include other additives, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • CMC-Na sodium carboxymethylcellulose
  • the negative electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • electrolytes can be liquid, gel or all solid.
  • the electrolyte is an electrolytic solution.
  • the electrolytic solution includes an electrolytic salt and a solvent.
  • the electrolyte salt may be selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorooxalate borate, lithium difluorodifluorooxalatephosphate and lithium tetrafluorooxalatephosphate.
  • the solvent may be selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may optionally include additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of the battery, such as additives that improve battery overcharge performance, additives that improve high-temperature or low-temperature performance of batteries, and the like.
  • a separator is further included in the secondary battery.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the separator can be a single-layer film or a multi-layer composite film, without any particular limitation. When the separator is a multilayer composite film, the materials of each layer may be the same or different, and there is no particular limitation.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer package.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft case may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 4 shows a secondary battery 5 having a square structure as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to close the accommodating cavity.
  • the positive pole piece, the negative pole piece and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the accommodating chamber. Electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG. 6 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may also include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source of the electric device, and can also be used as an energy storage unit of the electric device.
  • the electric devices may include mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, etc.) , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but not limited thereto.
  • a secondary battery, a battery module or a battery pack can be selected according to its use requirements.
  • FIG. 9 is an example of an electrical device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • a device may be a cell phone, tablet, laptop, or the like.
  • the device is generally required to be light and thin, and a secondary battery can be used as a power source.
  • Lithium carbonate Li 2 CO 3 , positive electrode active material precursor Ni 0.556 Co 0.11 Mn 0.334 (OH) 2 and zirconia ZrO 2 are mixed, and then mechanically mixed.
  • the amount of lithium carbonate added is such that the molar amount of lithium element and Me
  • the mixed material was put into a tube furnace, and the temperature was programmed to rise to 940°C at 5°C/min for sintering in an air atmosphere for 13 hours, and then cooled to room temperature with the furnace, and then in a jet mill (Shen Fei (40m 3 )) to The crushing air pressure is 0.35MPa, the feeding speed is 300Kg/h, and the 2mm particles are crushed to obtain the active material particle precursor 1 .
  • the amount of cobalt hydroxide added is such that the molar ratio of the molar amount of cobalt element to Me is 1.14 ⁇ 10 -2 :1.
  • the temperature is programmed to rise to 700°C at 5°C/min for sintering for 5 hours in an air atmosphere, and then After cooling down to room temperature with the furnace, the active material particle precursor 2 was obtained.
  • the amount of titanium added was such that the molar ratio of the molar amount of titanium element to Me was 2.031 ⁇ 10 ⁇ 3 :1.
  • the active material particle precursor 2 with a titanium oxide coating layer was obtained.
  • the obtained active material particle precursor with a titanium oxide coating is tempered, the temperature of the tempering treatment is 500° C., and the time is 5 hours to obtain the positive electrode active material CA1, wherein the molecular formula of the active material particle is Li 1.03 (Ni 0.55 Co 0.12 Mn 0.33 ) 0.996 Zr 0.002 Ti 0.002 O 2 .
  • step 4 is not included in the preparation process
  • step 2) the mixed material was put into a tube furnace, and the temperature was programmed to rise to 960° C. at 5° C./min for sintering for 13 hours in an air atmosphere.
  • the active material particle precursor 1 obtained above is mixed with cobalt hydroxide, and the sintering treatment temperature is 710° C., and the time is 5 hours;
  • the unmentioned reaction conditions and reaction steps are the same as in Example 1, and the molecular formula of the active material particles obtained as the positive electrode active material is Li 1.03 ( Ni 0.6 Co 0.1 Mn 0.3 ) 0.997 Sr 0.001 Ti 0.002 O 2 .
  • the amount of cobalt hydroxide added is such that the molar amount of cobalt element and the molar amount of Me
  • the amount ratio is 2.36 ⁇ 10 -2 : 1, the sintering temperature is 720°C, and the time is 5h;
  • the addition amount of titanium oxide is such that the titanium element
  • the molar ratio of the molar amount of Me to Me is 2.06 ⁇ 10 -3 :1;
  • the unmentioned reaction conditions and reaction steps are the same as in Example 1, and the molecular formula of the active material particles obtained as the positive electrode active material is Li 1.03 (Ni 0.65 Co 0.1 Mn 0.25 ) 0.996 Mg 0.002 Ti 0.002 O 2 .
  • the unmentioned reaction conditions and reaction steps are the same as in Example 1, and the molecular formula of the active material particles obtained as the positive electrode active material is Li 1.03 (Ni 0.70 Co 0.10 Mn 0.2 ) 0.996 Mg 0.002 Ti 0.002 O 2 .
  • the positive electrode active material precursor is Ni 0.707 Co 0.04 Mn 0.253 (OH) 2 ; the pH of the reaction system is adjusted to 11.8;
  • the temperature of the sintering treatment is 910°C, and the time is 14h;
  • the amount of cobalt oxide added is such that the molar ratio of the molar amount of cobalt element to Me is 1.05 ⁇ 10 -2 :1, the sintering treatment temperature is 700°C, and the time is 4h;
  • the unmentioned reaction conditions and reaction steps are the same as in Example 1, and the molecular formula of the active material particles obtained as the positive electrode active material is Li 1.03 (Ni 0.7 Co 0.05 Mn 0.25 ) 0.996 Zr 0.002 Ti 0.002 O 2 .
  • the mixture was put into a tube furnace, and sintered in an air atmosphere at a temperature programmed at 5°C/min to 960°C for 13 hours; then cooled to the greenhouse with the furnace and crushed.
  • step 2) No compound containing M element is added in step 2) and step 3) is not included.
  • the unmentioned reaction conditions and reaction steps are the same as in Example 1, and the molecular formula of the active material particles obtained as the positive electrode active material is Li(Ni 0.55 Co 0.12 Mn 0.33 ) 0.998 Ti 0.002 O 2 .
  • the temperature of the sintering treatment in 2) is 950°C, the time is 13h, and step 3) is not included;
  • the unmentioned reaction conditions and reaction steps are the same as in Example 1, and the molecular formula of the active material particles obtained as the positive electrode active material is Li 1.03 (Ni 0.55 Co 0.10 Mn 0.33 ) 0.996 Zr 0.002 Ti 0.002 O 2 .
  • the mixture was put into a tube furnace, and sintered in an air atmosphere at a temperature programmed at 5°C/min to 960°C for 13 hours; then cooled to the greenhouse with the furnace and crushed.
  • step 2) No compound containing M element is added in step 2) and step 3) is not included.
  • the unmentioned reaction conditions and reaction steps are the same as in Example 1, and the molecular formula of the active material particles obtained as the positive electrode active material is Li(Ni 0.55 Co 0.15 Mn 0.30 ) 0.998 Ti 0.002 O 2 .
  • Preparation of positive electrode sheet disperse the positive electrode active material, conductive carbon black SP and binder polyvinylidene fluoride (PVDF) prepared in each embodiment and comparative example into the solvent N-methyl Pyrrolidone (NMP), mixed uniformly to obtain a positive electrode slurry; the positive electrode slurry was evenly coated on an aluminum foil of a positive electrode current collector, and after drying and cold pressing, a positive electrode sheet was obtained.
  • PVDF polyvinylidene fluoride
  • Negative pole piece metal lithium piece with a diameter of 18mm and a thickness of 0.5mm (Tianjin Zhongneng).
  • buttons Preparation of the button battery: Stack the positive pole piece, polypropylene/polyethylene/polypropylene (PP/PE/PP) composite separator and the negative pole piece in order, and add the above electrolyte to complete the button battery preparation.
  • PP/PE/PP polypropylene/polyethylene/polypropylene
  • a field emission scanning electron microscope (Zeiss sigma 300) was used, and the specific settings were as follows: the resolution was 20nm, the accelerating voltage was 0.1-30KV, the magnification was 30-50000 times, and the mode was In-lens.
  • the detailed test process is carried out in accordance with the reference standard JY/T010-1996.
  • FIG. 1 A scanning electron microscope (SEM) of the cathode active material of Example 1 is shown in FIG. 1 .
  • Determination of the content of metal elements and S elements according to inductively coupled plasma atomic emission spectrometry, using plasma atomic emission (ICP-OES, instrument model: Thermo ICAP7400) for determination. Firstly, 0.4 g of low-cobalt positive electrode active material was weighed, and 10 ml (50% concentration) of aqua regia was added thereto. Then place it on a plate at 180°C for 30min). After digestion on the plate, set the volume to 100mL, quantitative method: standard curve method, with reference to EPA 6010D-2014.
  • the oxygen element content is calculated by the difference between the total amount of the low-cobalt positive electrode active material (that is, 1) and the sum of the above-mentioned detectable element contents.
  • Argon ion cross-section polisher (model JEOL IB-19530CP) and scanning electron microscope (model Zeiss sigma 300) (configured with X-ray energy spectrometer (EDS, model Oxford energy spectrometer OXFord X-Max-50mm 2 )) were used for determination.
  • the low-cobalt active material, PVDF, and NMP are made into a slurry at a weight ratio of 5:2:23, evenly coated on the copper foil, and dried at 60°C.
  • a scanning electron microscope was used to scan the cross section of the single crystal particle for Co element, and the curve reflected the content change of Co element, as shown in FIG. 2 .
  • Sample preparation Add an appropriate amount of low-cobalt cathode material to water, with a total volume of about 110ml, and ultrasonicate at 53KHz and 120W for 5min.
  • the particle size volume distribution diagram according to the test data (such as accompanying drawing 3 is the particle size volume distribution diagram of the low-cobalt material of Example 1). Obtained from the distribution diagram: the particle diameter accounting for 50% of the total volume is greater than a certain Dv50 value, and the particle diameter accounting for 50% of the total volume is smaller than this Dv50 value, then the Dv50 value is the volume average particle diameter of the particle.
  • the button battery At 25°C, charge the button battery with a constant current rate of 0.1C to 4.35V, then charge it with a constant voltage until the current is less than or equal to 0.05C, then leave it for 5 minutes, and then discharge it with a constant current rate of 0.1C to 2.8V.
  • the discharge capacity is normal temperature gram capacity. Put the button battery at a low temperature of -10°C, and obtain the low-temperature gram capacity according to the above test. The percentage of the ratio of the low temperature gram capacity to the normal temperature gram capacity is the capacity retention rate.
  • the button battery At a low temperature of -10°C, charge the button battery with a constant current of 0.1C to 4.35V, then charge it at a constant voltage until the current is less than or equal to 0.05C, and then adjust the button battery to a state of charge (SOC) of 20%. Then discharge at 5C for 10s, record the voltage drop before and after discharge, the ratio of the voltage drop before and after discharge to the discharge current is the DC resistance DCR of the battery.
  • SOC state of charge
  • Examples 1-7 of the present invention show that the single-crystal low-cobalt ternary material of the present invention has a smaller median particle size and non-uniformly distributed Co elements; thereby obtaining Under high voltage, it is a secondary battery with small current resistance and high capacity retention. It can be seen that the secondary battery comprising the single crystal low-cobalt ternary material of the present invention has improved power and cycle performance at low temperature and high voltage.
  • the cobalt content in the positive electrode active material is relatively low, thereby reducing the cost; at the same time, if the mole fraction of each element in the chemical formula satisfies a certain proportional relationship and is within a certain range, the positive electrode activity is guaranteed
  • the material has high structural stability; the particle size of the positive electrode active material is in the range of 1.8 ⁇ m-3.5 ⁇ m, which makes the migration path of lithium ions in the positive electrode active material shorter, and the single particle of the positive electrode active material is inside and outside
  • the Co content per unit area of the layer is higher than that in the inner core, so that the surface layer structure has less Li/Ni mixing, and its rate of deintercalation of lithium ions is faster, and it has better kinetic performance at low temperature.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same function and effect are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

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Abstract

本申请涉及一种单晶结构的低钴三元正极材料，其化学式为Li 1+x(Ni aCo bMn c) 1-dM dO 2-yA y，其中，Co元素的摩尔分数较低，0.05≤b≤0.14；并且在单个颗粒中，在通过颗粒的几何中心的横截面上，外层的每单位面积的平均Co含量与内核的每单位面积的平均Co含量之间的比例在1.2-5.0:1范围内，可选地在1.4-2.0:1范围内。该材料在低温高电压下具有更好的结构稳定性和动力学性质，改善了二次电池在低温高电压下的循环性能和功率性能。本申请还提供所述低钴三元正极材料的制备方法，包含该材料的二次电池、电池模块、电池包和用电装置。

Description

一种单晶低钴三元材料及其制备方法、二次电池、电池包、用电装置 技术领域
本申请涉及锂离子电池技术领域，尤其涉及一种单晶低钴三元材料。此外，本申请还涉及包含所述单晶低钴三元材料的二次电池、包括所述二次电池的电池包、电池模块和用电装置。
背景技术
近年来，随着锂离子电池的应用范围越来越广泛，锂离子电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。随着锂离子电池的应用范围日益扩大，其在低温下的加速性能和续航里程也亟需提高以满足更大的市场需求。
目前，在锂离子电池中，采用磷酸铁锂和镍钴锰酸锂三元材料作为正极活性材料是比较有效的手段。相较于磷酸铁锂，镍钴锰酸锂是最佳选择，然而该材料因为高的含钴量而成本较高，并且在低温高电压的工况下锂离子电池会发生循环性能降低，功率减小，寿命缩短等问题。因此，亟需一种正极活性材料，其能够使锂离子电池在低温高电压下具有改善的电化学性能，并且降低制造成本。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种低钴三元正极活性材料，使二次电池在低温高电压下，具有改善的功率和循环性能，以及较低的成本。
为了实现上述目的，本申请提供了一种单晶结构的低钴三元正极材料，其特征在于，
所述单晶低钴三元正极材料的化学式为Li 1+x(Ni aCo bMn c) 1-dM dO 2-yA y，其中，M为选自Zr、Sr、B、Ti、Mg、Sn及Al中的一种或多种，A为选自S、N、F、Cl、Br及I中的一种 或多种，0≤x≤0.5，0.05≤b≤0.14，3.5≤a/b≤15，0.02≤b×c/a 2≤0.21，a+b+c＝1，0≤d≤0.1，0≤y<0.2；并且
所述单晶低钴三元正极材料的单个颗粒中，在通过颗粒的几何中心的横截面上，外层的每单位面积的平均Co含量与内核的每单位面积的平均Co含量之间的比例在1.2-5.0:1范围内，可选地在1.4-2.0:1范围内，其中，所述外层是自所述颗粒的表面至朝向颗粒几何中心方向上200nm深度之间的区域，所述内核是以所述颗粒的几何中心为圆心的直径200nm的球面区域。进一步地，该材料颗粒的半径至少为300nm，可选400至4000nm。由此，本申请通过获得满足上述关系式且Co元素含量在外层较内核中更高的单晶低钴三元材料，有效改善了正极材料在低温高电压下的结构稳定性和动力学性质，从而提高二次电池在低温高电压下的循环性能和功率。
在一些实施方式中，所述低钴三元正极材料的颗粒上还具有包覆层，所述包覆层为含Q的氧化物，其中，Q为选自Zr、Sr、B、Ti、Mg、Sn及Al中的一种或多种。这有利于减少正极活性材料表面与电解液的副反应，从而改善电池的稳定性和安全性能。
在一些实施方式中，所述低钴三元正极材料的化学式中，0.5≤a≤0.7。这有利于低钴三元正极材料在高电压下具有较高的比容量，并且维持较好的化学稳定性。
在一些实施方式中，所述低钴三元正极材料的中值粒径Dv 50在1.6μm-3.6μm范围内、可选地在1.8μm-3.5μm范围内。由此能够改善锂离子的脱嵌能力，提高电池的电化学性能。
在一些实施方式中，所述低钴三元正极材料，其特征在于，所述Q的含量为500-5000ppm，基于含Q的氧化物中Q元素相对于具有包覆层的低钴三元正极材料计。有利于提高正极活性材料的结构稳定性，减少产气和产热量。
本申请的第二方面提供制备低钴三元正极材料的方法，其特征在于，包括：
步骤S1：将正极活性材料前驱体、锂盐及含M的化合物混合并烧结，经过破碎得到活性物质颗粒前体1，其中所述正极活性材料前 驱体的化学式为(Ni aCo bMn c(OH) 2)，其中3.5≤a/b≤15，0.02≤b×c/a 2≤0.21，a+b+c＝1；0.5≤a≤0.7
步骤S2：将所述活性物质颗粒前体1与含Co的化合物混合并烧结，得到表层富含Co的活性物质颗粒前体2；回火处理，得到低钴三元正极材料；
其中，所述低钴三元正极材料为单晶结构，其化学式为Li 1+x(Ni aCo bMn c) 1-dM dO 2-yA y，其中，M为选自Zr、Sr、B、Ti、Mg、Sn及Al中的一种或多种，A为选自S、N、F、Cl、Br及I中的一种或多种，0≤x≤0.5，0.05≤b≤0.14，3.5≤a/b≤15，0.02≤b×c/a 2≤0.21，a+b+c＝1，0≤d≤0.1，0≤y<0.2；并且
所述单晶低钴三元正极材料的单个颗粒中，在通过颗粒的几何中心的横截面上，外层的每单位面积的平均Co含量与内核的每单位面积的平均Co含量之间的比例在1.2-5.0:1范围内，可选地在1.4-2.0:1范围内，其中，所述外层是自所述颗粒的表面至朝向颗粒几何中心方向上200nm深度之间的区域，所述内核是以所述颗粒的几何中心为圆心的直径200nm的球面区域。进一步地，该材料颗粒的半径至少为300nm，可选400至4000nm。
本发明的制备低钴三元正极活性材料的方法，其制备工艺简单，易于实现，且成本低，可大规模的应用于工业生产中。
二次电池在一些实施方式中，步骤S1中所述含M的化合物为选自氧化镁、氧化锶、氧化钛、氧化锡、氧化锆、氧化铝及氧化硼中的一种或多种，可选为氧化锆、氧化锶或氧化镁。
在所述步骤S1中，烧结温度在800℃～960℃范围内，烧结时间为5-15h，烧结气氛为空气或者O 2。这有利于颗粒之间的融合，提升颗粒粒径。
在一些实施方式中，在所述步骤S2中，还包括步骤S2a：将表层富含Co的活性物质颗粒前体2用含Q的氧化物进行包覆。在一些实施方式中，步骤S2a中含Q的氧化物为选自氧化铝、氧化锡、氧化锆、氧化硼及氧化钛中的一种或多种，可选为氧化钛。由此得到具 有覆盖层的单晶低钴正极活性材料，可以避免在二次电池中与电解液的接触，稳定单晶低钴正极活性材料的结构。
在一些实施方式中，步骤S2中所述含Co的化合物为选自氢氧化钴、羟基氧化钴、氧化钴、醋酸钴或草酸钴中的一种或多种。在一些实施方式中，步骤S2中，所述含Co的化合物的加入量，使得其中加入Co的摩尔量与步骤S1获得的正极活性材料前驱体中金属元素Ni、Co、Mn的总摩尔量的比例为0.005-0.05：1，可选地为0.01-0.03：1。
在一些实施方式中，步骤S2中，步骤S2中烧结温度在650-750℃范围，可选地在700-720℃范围内，烧结时间为2-8h，可选为4-5h，烧结气氛为空气或者O 2。由此获得具有不均匀分布的Co元素的正极活性材料。
本申请的第三方面提供一种二次电池，包括本申请第一方面的单晶低钴正极活性材料或根据本申请第二方面的方法制备的单晶低钴正极活性材料。
本申请的第四方面提供一种电池模块，包括本申请的第三方面的二次电池。
本申请的第五方面提供一种电池包，包括本申请的第四方面的电池模块。
本申请的第六方面提供一种用电装置，包括选自本申请的第三方面的二次电池、本申请的第四方面的电池模块或本申请的第五方面的电池包中的至少一种。
由于本发明提供的活性正极材料兼具单晶形貌，整体低钴外层富钴，粒径较小的特点，因此使用本发明的单晶低钴正极活性材料而制成的二次电池在低温高电压下具有改善的循环性能和功率性能，续航时间长。相应地，本申请提供的电池包、电池模块和用电装置在低温高电压下也具有好的循环能力和长时间的续航能力。
附图说明
图1示出本申请实施例1的低钴正极活性材料的SEM图。
图2示出本申请的低钴正极活性材料的Co元素线扫描图(图2A)，以及Co元素含量(质量分数)的径向分布(图2B)。
图3示出本申请一实施方式的体积平均粒径分布图。
图4是本申请一实施方式的二次电池的示意图。
图5是图4所示的本申请一实施方式的二次电池的分解图。
图6是本申请一实施方式的电池模块的示意图。
图7是本申请一实施方式的电池包的示意图。
图8是图7所示的本申请一实施方式的电池包的分解图。
图9是本申请一实施方式的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的负极极片及其制造方法、正极极片、二次电池、电池模块、电池包和电学装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-6。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩 略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
目前，二次球结构的镍钴锰酸锂三元材料由于其一次颗粒较小，具有更好的低温性能；但是在高电压(≥4.3V)下，二次球颗粒容易开裂，导致容量迅速下降。相比之下，单晶结构的镍钴锰酸锂三元材料具有不容易开裂的特性，更适合高电压应用，但其一次颗粒较大，低温性能往往差于三元二次球。而且，在市售的镍钴锰酸锂三元材料中的钴含量较高，因为这有利于减少正极活性材料的表层的Li/Ni混 排比，加快锂离子的脱嵌速率，从而进一步提升单晶低钴三元正极材料的动力学性能。但是由于Co的价格昂贵而造成成本过高。
为了解决上述技术问题，发明人通过对单晶结构的镍钴锰酸锂三元材料进行改性，开发出一种低成本，并且能够在改善电池在低温高电压下的循环性能和功率的单晶低钴三元正极材料。
低钴三元正极材料
本申请的第一方面提供了一种单晶结构的低钴三元正极材料，其特征在于，
所述低钴三元正极材料的化学式为Li 1+x(Ni aCo bMn c) 1-dM dO 2-yA y，其中，M为选自Zr、Sr、B、Ti、Mg、Sn及Al中的一种或多种，A为选自S、N、F、Cl、Br及I中的一种或多种，0≤x≤0.5，0.05≤b≤0.14，3.5≤a/b≤15，0.02≤b×c/a 2≤0.21，a+b+c＝1，0≤d≤0.1，0≤y<0.2；
并且
所述单晶低钴三元正极材料的单个颗粒中，在通过颗粒的几何中心的横截面上，外层的每单位面积的平均Co含量与内核的每单位面积的平均Co含量之间的比例在1.2-5.0:1范围内，可选地在1.4-2.0:1范围内，其中，所述外层是自所述颗粒的表面至朝向颗粒几何中心方向上200nm深度之间的区域，所述内核是以所述颗粒的几何中心为圆心的直径200nm的球面区域。进一步地，该材料颗粒的半径至少为300nm，可选400至4000nm。
在本发明中，所述低钴三元正极材料为单晶结构，在锂离子电池领域中，单晶指的是颗粒的一种形貌，其通常是单颗粒(微米级大小)分散的形式，具有较少的晶界；而二次球颗粒通常是以许多个颗粒(100～500纳米)团聚形成球形，具有非常多的晶界。单晶三元正极材料是以单分散一次颗粒为主体的粉料，所述单分散一次颗粒表示这些一次颗粒是彼此分离、相互独立的。更为关键的是，此单晶结构的三元正极材料适用于高电压(≥4.3V)，具有能量密度高，不易开裂的优势，是多晶二次球三元材料所不具备的。
在本发明中，“单位面积”指的是在外层和内核中，为相同大小的面积，通常为1平方纳米，也可以根据实际测试情况进行选择。
在本发明中，所述Co含量是指单晶低钴三元材料的单个颗粒中，在经过该单个颗粒的几何中心的横截面上，单位面积中所包含的Co元素的质量占所述单晶低钴三元材料的总质量的百分比例。
在所述低钴三元正极材料化学式中，Li元素的摩尔分数与Ni、Co和Mn的总摩尔分数之比为在(1.67-1)：1范围内，可选地在(1.10-1.01):1范围内，这是由于烧结温度较高时，需要提高过量锂来补偿；而且，摩尔比在该范围内，有利于获得较高比能量的单晶材料。
Co的摩尔分数为0.05≤b≤0.14，相对于市售的常用三元材料产品(例如NCM333或NCM523)的Co含量(至少为0.15)更低。因此，本发明的单晶低钴三元材料降低了钴的用量，从而减少产品成本。
Ni、Co和Mn的摩尔分数应该满足以下关系：3.5≤a/b≤15，0.02≤b×c/a 2≤0.21，有利于获得晶体结构稳定的低钴三元单晶材料。
任选地，当M元素存在于本发明的单晶低钴正极材料中，M元素的摩尔分数不大于0.1，可选地，在0.001至0.005范围内，这有利于更有效地稳定正极活性材料的结构，提高锂离子在正极活性材料颗粒中的传输性能，从而提高电池的循环性能；
任选地，当A元素存在于本发明的单晶低钴正极材料中，A元素的摩尔分数不大于0.2，通过在正极活性材料中加入电负性较强的A元素，进一步提高正极活性材料的结构稳定性，有利于提高电池的循环性能。
令人惊讶地是，本发明人发现，满足上述关系式的单晶低钴三元材料，如果Co元素不均匀地分布，尤其是在外层与内核中单位面积的Co含量比例在1.2-5.0:1范围内，可选地在1.4-2.0:1范围内，则可以获得在低温高电压下的结构稳定的低钴三元正极材料，从而改善二次电池在低温高电压下的循环性能和功率。
在一些实施方式中，在所述低钴三元正极材料的颗粒上还具有包覆层，所述包覆层为含Q的氧化物，其中，Q为选自Zr、Sr、B、Ti、 Mg、Sn及Al中的一种或多种。进一步地，覆盖层的厚度为3-100nm，可选10-180nm。
本发明的单晶低钴三元正极活性材料可以是活性物质颗粒，也可以是由所述活性物质颗粒及包覆在其上的包覆层一起构成的颗粒，该包覆层为选自Q元素氧化物的包覆层。
通过在活性物质颗粒的表面上包覆含Q元素氧化物的包覆层，有利于降低在正极活性材料表面上的电解液氧化活性，减少电解液在正极活性材料表面的副反应，抑制产气，减少产热量，从而改善电池的稳定性和安全性能。
在本发明中，所述表面是指本体(例如所述活性物质颗粒)与外界(例如空气、水或电解液)接触的界面。
在一些实施方式中，在所述低钴三元正极材料的化学式中，0.5≤a≤0.7。
这有利于低钴三元正极材料在高电压下具有较高的比容量，并且维持较好的化学稳定性。
在一些实施方式中，所述低钴三元正极材料为中值粒径Dv 50在1.6μm-3.6μm范围内、可选地在1.8μm-3.5μm范围内的颗粒。进一步可选地，Dv 10在0.9μm-1.1μm范围内，例如1.0μm；Dv 30在1.4μm-1.6μm范围内，例如1.5μm；Dv 60在2.4μm-2.6μm范围内，例如2.5μm。
由此，能够改善锂离子的脱嵌能力，加快锂离子的脱嵌速率，有利于改善电池在低温下的电化学性能。
在一些实施方式中，所述低钴三元正极材料的包覆层中所述Q的含量为500-5000ppm，基于含Q的氧化物中Q元素相对于具有包覆层的单晶低钴三元正极材料计。
这不仅有利于提高正极活性材料的结构稳定性，减少产气和产热量，而且有利于正极活性材料具有较高的倍率性能、功率性能及容量性能。
本申请的第二方面提供了一种制备低钴三元正极材料的方法，其特征在于，包括：
步骤S1：将正极活性材料前驱体、锂盐及含M的化合物混合并烧结，经过破碎得到活性物质颗粒前体1，其中所述正极活性材料前驱体的化学式为(Ni aCo bMn c(OH) 2)，其中0.05≤b≤0.14，3.5≤a/b≤15，0.02≤b×c/a 2≤0.21，a+b+c＝1，0.5≤a≤0.7，
步骤S2：将所述活性物质颗粒前体1与含Co的化合物混合并烧结，得到表层富含Co的活性物质颗粒前体2；回火处理，得到低钴三元正极材料；
其中，低钴三元正极材料为单晶结构，
所述低钴三元正极材料的化学式为Li 1+x(Ni aCo bMn c) 1-dM dO 2-yA y，其中，M为选自Zr、Sr、B、Ti、Mg、Sn及Al中的一种或多种，A为选自S、N、F、Cl、Br及I中的一种或多种，0≤x≤0.5，0.05≤b≤0.14，3.5≤a/b≤15，0.02≤b×c/a 2≤0.21，a+b+c＝1，0≤d≤0.1，0≤y<0.2；并且
所述单晶低钴三元正极材料的单个颗粒中，在通过颗粒的几何中心的横截面上，外层的每单位面积的平均Co含量与内核的每单位面积的平均Co含量之间的比例在1.2-5.0:1范围内，可选地在1.4-2.0:1范围内，其中，所述外层是自所述颗粒的表面至朝向颗粒几何中心方向上200nm深度之间的区域，所述内核是以所述颗粒的几何中心为圆心的直径200nm的球面区域。进一步地，该材料颗粒的半径至少为300nm，可选400至4000nm。
本发明实施例提供的正极活性材料，其制备工艺简单，易于实现，且成本低，可大规模的应用于工业生产中。
步骤S1
在步骤S1中，正极活性材料前驱体可以通过共沉淀法、凝胶法或固相法制备获得。作为示例，正极活性材料前驱体的制备方法包括以下步骤：
S110、按照化学计量比将Ni源、Co源及Mn源分散在溶剂中得到混合溶液。
S120、调节混合溶液的pH，在预设温度及搅拌下进行反应，反应过程中可以通入惰性气体进行保护，反应完成后，经分离、洗涤、干燥，得到正极活性材料前驱体，其化学式为[Ni aCo bMn c](OH) 2。
在步骤S110中，Ni源为可溶性的镍盐。对镍盐的具体种类并没有特别的限制，可根据实际需求进行选择。作为示例，镍盐选自硫酸镍、硝酸镍、氯化镍、草酸镍或醋酸镍，及其任意的混合物，可选地选自硫酸镍和/或硝酸镍，进一步可选为硫酸镍。
在步骤S110中，Co源为可溶性的钴盐。对钴盐的具体种类并没有特别的限制，可根据实际需求进行选择。作为示例，钴盐选自硫酸钴、硝酸钴、氯化钴、草酸钴或醋酸钴，及其任意的混合物，可选地选自硫酸钴和/或硝酸钴，进一步可选为硫酸钴。
在步骤S110中，Mn源为可溶性的锰盐。对锰盐的具体种类并没有特别的限制，可根据实际需求进行选择。作为示例，锰盐选自硫酸锰、硝酸锰、氯化锰、草酸锰或醋酸锰，及其任意的混合物，可选地选自硫酸锰和/或硝酸锰，进一步可选为硫酸锰。
在步骤S110中，加入Ni源、Co源及Mn源的物质的摩尔比为1：(0.04-0.4)：(0.2-0.7)，可选1：(0.05-0.3)：(0.25-0.65)。对上述溶剂并没有特别的限制，只要能够将Ni源、Co源及Mn源溶解即可。作为示例，溶剂选自水、甲醇、乙醇、丙酮、异丙醇或正己醇，及其任意的混合溶剂，其中水可以为去离子水、蒸馏水、矿泉水及自来水中的一种或多种，例如为去离子水。
在步骤S110中，对混合溶液的浓度没有特别的限制，可根据实际需求进行调节。所述混合溶液为包含镍、钴、锰离子的水溶液，一般可选为硫酸镍，硫酸锰，硫酸钴的水溶液。作为示例，混合溶液的浓度为1.5mol/L～3.5mol/L，例如为2.0mol/L～2.9mol/L。混合溶液中的Co源的浓度为0.05至1.0mol/L，可选为0.06至0.6mol/L。
在步骤S120中，可以通过向混合溶液中加入沉淀剂和络合剂来形成反应体系，调节反应体系中络合剂的浓度和沉淀剂的浓度，并调控使反应体系的pH为10～12，进行共沉淀反应，以得到正极活性材料前驱体，如[Ni aCo bMn c](OH) 2。
在步骤S120中，沉淀剂可以为LiOH、NaOH及KOH中的一种或多种，例如为NaOH。进一步地，沉淀剂是溶液的形式，其中溶剂可以为水、甲醇、乙醇、丙酮、异丙醇及正己醇中的一种或多种，前述水可以为去离子水、蒸馏水、矿泉水及自来水中的一种或多种，例如为去离子水。其中对沉淀剂溶液的浓度并没有特别的限制，可根据实际需求进行选择。可选地，NaOH的浓度为0.5-5mol/L，例如1mol/L。
在步骤S120中，络合剂可以为氨水、硫酸铵、硝酸铵、氯化铵、柠檬酸铵及乙二胺四乙酸二钠(EDTA)中的一种或多种。进一步地，络合剂是溶液的形式，其中溶剂可以为水、甲醇、乙醇、丙酮、异丙醇及正己醇中的一种或多种，前述水可以为去离子水、蒸馏水、矿泉水及自来水中的一种或多种，例如为去离子水。
可选地，络合剂为氨水，对氨水的浓度并没有特别的限制，可根据实际需求进行选择。可选地，氨水的浓度为0.1mol/L～2mol/L，进一步地为0.2mol/L～1.5mol/L，更进一步地为0.3mol/L～1mol/L，例如0.4mol/L。
进一步地，反应的温度为40℃～70℃，再进一步地为45℃～65℃，更进一步地为50℃～60℃。
在步骤S120中，反应在惰性气体保护气氛、持续搅拌下进行，惰性气体例如选自氮气、氩气、氦气中的一种或多种，对搅拌的方式并没有特别的限制，只要能够使得反应体系搅拌均匀即可。例如，选择机械搅拌。搅拌转速例如为100rpm～800rpm。上述“rpm”即转每分，表征搅拌设备每分钟的旋转次数。
共沉淀反应产物洗涤时，对所选用的洗涤剂并没有特别的限制，根据实际需求进行选择，例如用去离子水进行洗涤，其中，洗涤的次数并没有特别的限制，只要能将反应产物表面的残余离子洗涤除去即可。
共沉淀反应产物洗涤之后干燥时，对干燥的温度和方式并没有特别的限制，可根据实际需求进行选择。例如，干燥的温度为100℃～150℃。
在步骤S1中，锂盐选自氧化锂(Li 2O)、磷酸锂(Li 3PO 4)、磷酸二氢锂(LiH 2PO 4)、醋酸锂(CH 3COOLi)、氢氧化锂(LiOH)、碳酸锂(Li 2CO 3)或硝酸锂(LiNO 3)，及其任意的混合物。可选地，锂盐选自碳酸锂、氢氧化锂或硝酸锂，及其任意的混合物。进一步可选地，锂盐为碳酸锂。
在步骤S1中，含M的化合物可以选自含有M元素的氧化物、硝酸化合物、碳酸化合物、氢氧化合物及醋酸化合物中的一种或多种。例如含M的化合物为含有M元素的氧化物，选自氧化镁、氧化锶、氧化钛、氧化锡、氧化锆、氧化铝及氧化硼中的一种或多种；可选地，选自氧化镁、氧化锶、氧化钛、氧化锆、氧化铝及氧化硼的一种或多种；进一步可选地，选自氧化锶、氧化钛、氧化锆、氧化铝及氧化硼中的一种或多种；又进一步可选地，选自氧化锆、氧化锶和氧化硼中的一种或多种。
其中，可选地，制备不含掺杂元素M或者含掺杂元素M的活性物质颗粒时，正极活性材料前驱体和锂盐的添加量为使得正极活性材料前驱体中金属元素(Ni、Co、Mn)的总摩尔量与锂盐中Li元素的摩尔量之比为Me:Li＝1:(0.99～1.2)，可选地，Me:Li＝1:(1～1.2)，进一步可选地，Me:Li＝1:(1.02～1.10)，其中Me为正极活性材料前驱体中的金属元素的摩尔量的总和，即Me＝Ni+Co+Mn。
可选地，制备含掺杂元素M的活性物质颗粒时，正极活性材料前驱体和含M化合物的添加量为使得正极活性材料前驱体中金属元素(Ni、Co、Mn)的总摩尔量与含M化合物中M元素的摩尔量之比为Me:M＝1:(0.001-0.005)，可选地，Me:M＝1:(0.0015-0.003)，其中Me为正极活性材料前驱体中的金属元素的摩尔量的总和，即Me＝Ni+Co+Mn。
在步骤S1中，将正极活性材料前驱体和锂盐混合并进行烧结处理，可以得到不含掺杂元素M的活性物质颗粒。或者，将正极活性材料前驱体及锂盐与含M的化合物混合并且进行烧结处理，可以得到在过渡金属位经过M改性的活性物质颗粒。或者，将正极活性材料前驱体及锂盐与含M的化合物和含A的化合物混合并且进行烧结 处理，可以得到在过渡金属位经过M改性且在氧位经过A元素掺杂的活性物质颗粒。
含A的化合物可以根据实际需求进行选择，例如选自氟化铵、氟化锂、氟化氢、氯化铵、氯化锂、氯化氢、溴化铵、溴化锂、溴化氢、碘化铵、碘化锂、碘化氢、硫化氢、硫化锂及硫化铵中的一种或多种。
进一步地，在步骤S1中，烧结在氧气或空气中进行；烧结的温度在800℃～960℃范围内。对烧结的时间并没有特别的限制，可根据实际情况进行调节，例如为5h～15h。该烧结温度较高，有利于颗粒之间的融合，提升颗粒粒径。
在步骤S1中，对破碎的方式并没有特别的限制，可根据实际需求进行选择，例如使用气流磨或机械磨。可选地，使用气流磨，例如沈飞气流粉碎机(容积为40m 3)，设定粉碎气压为0.2-0.35MPa，投料速度为280-320Kg/h，投料颗粒度控制在2mm以内，破碎操作有利于进一步分解颗粒，从而控制粒径在所期望的范围内。
通过步骤S1中的烧结和破碎，得到的活性物质颗粒前体1的中值粒径为1.4μm-3.4μm，可选地在1.6μm-3.5μm。
步骤S2
在一些实施方式中，在所述步骤S2中，还包括步骤S2a：将表层富含Co的活性物质颗粒前体2用含Q的氧化物进行包覆。
由包括步骤S2a的方法得到的正极活性材料，包括活性物质颗粒以及包覆在所述活性物质颗粒表面的含M元素包覆层。通过该覆盖成，可以避免在二次电池中，活性物质颗粒与电解液的接触，以保证正极活性材料的结构稳定。
在一些实施方式中，在步骤S2a中含Q的氧化物为选自氧化铝、氧化锡、氧化锆、氧化硼及氧化钛中的一种或多种，可选为氧化钛。
包覆处理可以采用本领域已知的方法和设备来进行，例如干法包覆、液相包覆法、气相沉积包覆法等。
由此得到具有覆盖层的单晶低钴正极活性材料，可以避免在二次电池中与电解液的接触，稳定单晶低钴正极活性材料的结构。
在一些实施方式中，步骤S2中所述含Co的化合物为选自氢氧化钴、羟基氧化钴、氧化钴、醋酸钴或草酸钴中的一种或多种。
在一些实施方式中，步骤S2中，所述含Co的化合物的加入量，使得其中加入Co的摩尔量与步骤S1获得的正极活性材料前驱体中金属元素Ni、Co、Mn的总摩尔量的比例为0.005-0.05：1，可选地为0.01-0.03：1。
在一些实施方式中，步骤S2中，步骤S2中烧结温度在650-750℃范围，可选地在700-720℃范围内，烧结时间为2-8h，可选为4-5h，烧结气氛为空气或者O 2。
这有利于表面的Co元素向颗粒内扩散，从而实现在所述低钴三元正极材料的单个颗粒中，Co元素的不均匀分布，尤其是在外层的单位面积的平均Co含量与内核的单位面积的平均Co含量之间的比例在1.2-5.0:1范围内，可选地在1.4-2.0:1范围内。
进一步地，在步骤S2中，回火处理的温度为400℃～700℃，可选地为450℃～600℃。
二次电池
另外，以下适当参照附图对本申请的二次电池、电池模块、电池包和用电装置进行说明。
本申请的一个实施方式中，提供一种二次电池，其中，包括使用本申请的单晶低钴正极活性材料的正极极片。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括本申请第一方面的正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子 材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。 软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图4是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图5，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图6是作为一个示例的电池模块4。参照图6，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图7和图8是作为一个示例的电池包1。参照图7和图8，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图9是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
一、制备实施例
[正极活性材料的制备]
实施例1
1)正极活性材料前驱体的制备
将硫酸镍、硫酸锰和硫酸钴加入去离子水中，配制成混合溶液，其中镍元素、钴元素、锰元素的摩尔比为Ni:Co:Mn＝55.6:11:33.4；向混合溶液中加入0.4mol/L氨水和1mol/L氢氧化钠水溶液，调节反应体系的pH为11.3，在40℃、600rpm搅拌的条件下进行反应，反应过程中通入惰性气体氮气进行保护，反应完成后，将固相产物用去 离子水洗涤，洗涤完成后在100℃下干燥，得到正极活性材料前驱体Ni 0.556Co 0.11Mn 0.334(OH) 2。
2)活性物质颗粒前体1的制备
将碳酸锂Li 2CO 3、正极活性材料前驱体Ni 0.556Co 0.11Mn 0.334(OH) 2及氧化锆ZrO 2混合，然后进行机械混料。其中，基于正极活性材料前驱体的金属元素总摩尔量(镍元素、钴元素及锰元素，即Me＝Ni+Co+Mn)计，碳酸锂的添加量为使得锂元素的摩尔量与Me的摩尔之比为Li:Me＝1.06:1；氧化锆的添加量为使得锆元素的摩尔量与Me的摩尔量比为Zr:Me＝2.031×10 -3:1。
将混合物料放入管式炉中，在空气气氛下以5℃/min程序升温至940℃进行烧结13h，之后随炉冷却至室温，然后在气流粉碎机(沈飞(40m 3))，以粉碎气压为0.35MPa，投料速度为300Kg/h，将2mm的颗粒进行破碎，得到活性物质颗粒前体1。
3)活性物质颗粒前体2的制备
向上述获得的活性物质颗粒的前体1中加入氢氧化钴，基于正极活性材料前驱体的金属元素总摩尔量(镍元素、钴元素及锰元素，即Me＝Ni+Co+Mn)计，氢氧化钴的添加量为使得钴元素的摩尔量与Me的摩尔比为1.14×10 -2:1，充分混合后，在空气气氛下以5℃/min程序升温至700℃进行烧结5h，之后随炉冷却至室温，获得活性物质颗粒前体2。
4)具有包覆层的活性物质颗粒前体的制备
将氧化钛TiO 2加入到活性物质颗粒的前体2中，基于正极活性材料前驱体的金属元素总摩尔量(镍元素、钴元素及锰元素，即Me＝Ni+Co+Mn)计，氧化钛的添加量为使得钛元素的摩尔量与Me的摩尔比为2.031×10 -3:1，在充分混合后，得到具有氧化钛包覆层的活性物质颗粒前体2。
5)低钴正极活性材料的制备
对于获得的具有氧化钛包覆层的活性物质颗粒前体进行回火处理，回火处理的温度为500℃,时间5h，获得正极活性材料CA1，其中活性物质颗粒的分子式为Li 1.03(Ni 0.55Co 0.12Mn 0.33) 0.996Zr 0.002Ti 0.002O 2。
实施例2
与实施例1类似，不同之处在于，在该制备过程中不包括步骤4)
实施例3
与实施例1类似，不同之处在于步骤2)中在将混合物料放入管式炉中，在空气气氛下以5℃/min程序升温至960℃进行烧结13h。
实施例4
与实施例1类似，不同之处在于下述的制备过程：
1)正极活性材料前驱体的制备
镍元素、钴元素、锰元素的摩尔比为Ni:Co:Mn＝60.7:9:30.4，正极活性材料前驱体为Ni 0.607Co 0.09Mn 0.304(OH) 2；
2)活性物质颗粒前体1的制备
将碳酸锂Li 2CO 3、正极活性材料前驱体Ni 0.607Co 0.09Mn 0.304(OH) 2及氧化锶SrO混合，然后进行机械混料；基于正极活性材料前驱体的金属元素总摩尔量(镍元素、钴元素及锰元素，即Me＝Ni+Co+Mn)计，氧化锶的添加量为使得锶元素的摩尔量与Me的摩尔之比为Sr:Me＝1.011×10 -3:1，；烧结处理的温度为930℃，时间为12h；
3)活性物质颗粒前体2的制备
将上述获得的活性物质颗粒前体1与氢氧化钴混合，烧结处理温度为710℃，时间为5h；
其中，未提及的反应条件和反应步骤与实施例1相同，获得正极活性材料的活性物质颗粒的分子式为Li 1.03(Ni 0.6Co 0.1Mn 0.3) 0.997Sr 0.001Ti 0.002O 2。
实施例5
与实施例1类似，不同之处在于下述的制备过程：
1)正极活性材料前驱体的制备
镍元素、钴元素、锰元素的摩尔比为Ni:Co:Mn＝67.6:8:25.6，正极活性材料前驱体为Ni 0.676Co 0.08Mn 0.256(OH) 2；调节反应体系的pH为11.7；
2)活性物质颗粒前体1的制备
将碳酸锂Li 2CO 3、正极活性材料前驱体Ni 0.607Co 0.09Mn 0.304(OH) 2及氧化镁MgO混合，然后进行机械混料；基于正极活性材料前驱体的金属元素总摩尔量(镍元素、钴元素及锰元素，即Me＝Ni+Co+Mn)计，氧化镁的添加量为使得镁元素的摩尔量与Me的摩尔之比为Mg:Me＝2.06×10 -3:1，；烧结处理的温度为920℃，时间为12h；
3)活性物质颗粒前体2的制备
基于正极活性材料前驱体的金属元素总摩尔量(镍元素、钴元素及锰元素，即Me＝Ni+Co+Mn)计，氢氧化钴的添加量为使得钴元素的摩尔量与Me的摩尔量之比为2.36×10 -2:1的量混合，烧结处理温度为720℃，时间为5h；
4)具有包覆层的活性物质颗粒前体的制备
采用氧化钛TiO 2包覆，基于正极活性材料前驱体的金属元素总摩尔量(镍元素、钴元素及锰元素，即Me＝Ni+Co+Mn)计，氧化钛的添加量为使得钛元素的摩尔量与Me的摩尔比为2.06×10 -3:1；
其中，未提及的反应条件和反应步骤与实施例1相同，获得正极活性材料的活性物质颗粒的分子式为Li 1.03(Ni 0.65Co 0.1Mn 0.25) 0.996Mg 0.002Ti 0.002O 2。
实施例6
与实施例1类似，不同之处在于下述的制备过程：
1)正极活性材料前驱体的制备
镍元素、钴元素、锰元素的摩尔比为Ni:Co:Mn＝70.8:9:20.2，正极活性材料前驱体为Ni 0.708Co 0.09Mn 0.202(OH) 2；
2)活性物质颗粒前体1的制备
将碳酸锂Li 2CO 3、正极活性材料前驱体Ni 0.708Co 0.09Mn 0.202(OH) 2及氧化镁MgO混合，然后进行机械混料；基于正极活性材料前驱体的金属元素总摩尔量(镍元素、钴元素及锰元素，即Me＝Ni+Co+Mn)计，氧化镁的添加量为使得镁元素的摩尔量与Me的摩尔之比Mg:Me＝2.031×10 -3:1；烧结处理的温度为920℃，时间为11h；
其中，未提及的反应条件和反应步骤与实施例1相同，获得正极活性材料的活性物质颗粒的分子式为Li 1.03(Ni 0.70Co 0.10Mn 0.2) 0.996Mg 0.002Ti 0.002O 2。
实施例7
与实施例1类似，不同之处在于下述的制备过程：
1)正极活性材料前驱体的制备
镍元素、钴元素、锰元素的摩尔比为Ni:Co:Mn＝70.7:4:25.3。正极活性材料前驱体为Ni 0.707Co 0.04Mn 0.253(OH) 2；调节反应体系的pH为11.8；
2)活性物质颗粒前体1的制备
烧结处理的温度为910℃，时间为14h；
3)活性物质颗粒前体2的制备
将上述获得的活性物质颗粒前体1与氢氧化钴混合，基于正极活性材料前驱体的金属元素总摩尔量(镍元素、钴元素及锰元素，即Me＝Ni+Co+Mn)计，氢氧化钴的添加量为使得钴元素的摩尔量与Me的摩尔比为1.05×10 -2:1，烧结处理温度为700℃，时间为4h；
其中，未提及的反应条件和反应步骤与实施例1相同，获得正极活性材料的活性物质颗粒的分子式为Li 1.03(Ni 0.7Co 0.05Mn 0.25) 0.996Zr 0.002Ti 0.002O 2。
对比例C1
与实施例1类似，不同之处在于：
1)正极活性材料前驱体的制备
镍元素、锰元素及钴元素的摩尔比为Ni:Co:Mn＝55:12:33，正极活性材料前驱体为Ni 0.55Co 0.12Mn 0.33(OH) 2；其中调节反应体系的pH为11.2；
2)活性物质颗粒前体1的制备
将碳酸锂Li 2CO 3与正极活性材料前驱体Ni 0.55Co 0.12Mn 0.33(OH) 2混合，然后进行机械混料；基于正极活性材料前驱体的金属元素总摩 尔量(镍元素、钴元素及锰元素，即Me＝Ni+Co+Mn)计，碳酸锂的添加量为使得锂元素的摩尔量与Me的摩尔之比为Li:Me＝1.02:1；
将混合物放入管式炉总，在空气气氛下以5℃/min程序升温至960℃下进行烧结，时间为13h；之后随炉冷却至温室，破碎。
步骤2)中不加入包含M元素的化合物并且不包括步骤3)。
其中，未提及的反应条件和反应步骤与实施例1相同，获得正极活性材料的活性物质颗粒的分子式为Li(Ni 0.55Co 0.12Mn 0.33) 0.998Ti 0.002O 2。
对比例C2
与实施例1类似，不同之处在于，在步骤
2)中的烧结处理的温度为950℃，时间为13h，并且不包括步骤3)；
其中，未提及的反应条件和反应步骤与实施例1相同，获得正极活性材料的活性物质颗粒的分子式为Li 1.03(Ni 0.55Co 0.10Mn 0.33) 0.996Zr 0.002Ti 0.002O 2。
对比例C3
与实施例1类似，不同之处在于：
1)正极活性材料前驱体的制备
镍元素、锰元素及钴元素的摩尔比为Ni:Co:Mn＝55:15:30，正极活性材料前驱体为Ni 0.55Co 0.15Mn 0.30(OH) 2；其中调节反应体系的pH为11.2；
2)活性物质颗粒前体1的制备
将碳酸锂Li 2CO 3与正极活性材料前驱体Ni 0.55Co 0.12Mn 0.33(OH) 2混合，然后进行机械混料；基于正极活性材料前驱体的金属元素总摩尔量(镍元素、钴元素及锰元素，即Me＝Ni+Co+Mn)计，碳酸锂的添加量为使得锂元素的摩尔量与Me的摩尔之比为Li:Me＝1.02:1；
将混合物放入管式炉总，在空气气氛下以5℃/min程序升温至960℃下进行烧结，时间为13h；之后随炉冷却至温室，破碎。
步骤2)中不加入包含M元素的化合物并且不包括步骤3)。
其中，未提及的反应条件和反应步骤与实施例1相同，获得正极活性材料的活性物质颗粒的分子式为Li(Ni 0.55Co 0.15Mn 0.30) 0.998Ti 0.002O 2。
上述各实施例和对比例的正极活性材料的主要制备参数参见表1。各实施例和对比例的正极活性材料的产品参数参见表2。
二、应用实施例
[二次电池的制备]
1.正极极片制备：将各实施例和对比例制备的正极活性材料、导电炭黑SP及粘结剂聚偏氟乙烯(PVDF)按照重量比18:1:1分散至溶剂N-甲基吡咯烷酮(NMP)中，混合均匀，得到正极浆料；将正极浆料均匀涂布于正极集流体铝箔上，经烘干、冷压后，得到正极极片。
2.负极极片：直径为18mm，厚度为0.5mm的金属锂片(天津中能)。
3.电解液的制备：将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)及碳酸二乙酯(DEC)按照质量比30:30:40混合均匀，得到有机溶剂。将LiPF 6溶解于上述溶剂中，混合均匀，得到电解液。电解液中LiPF 6的浓度为1mol/L。
4.扣式电池的制备：将正极极片、聚丙烯/聚乙烯/聚丙烯(PP/PE/PP)复合隔离膜及负极极片按顺序堆叠好，加入上述电解液，完成扣式电池的制备。
对所述二次电池进行性能测试，测试结果汇总于表2。
三.测定方法
[低钴正极活性材料的测试]
1.低钴正极活性材料的扫描电镜图像
采用场发射扫描电镜(蔡司sigma 300)，具体设置如下：分辨率为20nm，加速电压为0.1-30KV，放大倍数为30-50000倍，模式为In-lens。详细测试过程按照参考标准JY/T010-1996进行。
实施例1的正极活性材料的扫描电子显微镜(SEM)如图1所示。
2.低钴正极活性材料中各元素含量测定
金属元素和S元素含量的测定：按照电感耦合等离子体原子发射光谱法，采用等离子体原子发射(ICP-OES，仪器型号:Thermo ICAP7400)进行测定。首先称取0.4g低钴正极活性材料，向其中加入10ml(50％浓度)王水。然后放置在180℃平板上30min)。在所述平板上消解后，定容至体积100mL，定量方法：标准曲线法，参考EPA 6010D-2014。
元素N、F、Cl、Br和I含量测定：使用离子色谱(IC)测试，参考EN 14582:2016。
氧元素含量通过低钴正极活性材料的总量(即为1)与上述可探测元素含量的总和的差值计算得到。
3.低钴活性材料的内核与外层中的Co元素含量的测定
采用氩离子截面抛光仪(型号JEOL IB-19530CP)和扫描电子显微镜(型号蔡司sigma 300)(配置X射线能谱仪(EDS，型号牛津能谱仪OXFord X-Max-50mm 2))进行测定。将低钴活性材料与PVDF、NMP以重量比5：2：23制作成浆料，均匀涂敷于铜箔，60℃烘干。在离子抛光后，使用扫描电子显微镜对于单晶颗粒的截面进行Co元素的线扫描，其曲线反映了Co元素的含量变化，如图2所示。
4.粒径分布测定
采用仪器：Malvern,Master Size 3000进行测定。测定条件：颗粒折射率：1.69，颗粒吸收率：1，溶剂折射率：1.330；。测试循环：3times，样品和背景测试时间：6s，样品和背景测试数：6,000，搅拌器/泵的转数：3000rpm，设置遮光度：8～12％。
样品的配制：在水中加入适量的低钴正极材料，总体积约110ml，在53KHz、120W下超声5min。
详细测试过程按照参考标准：GB/T19077-2016/ISO13320:2009进行。
根据测试数据绘制粒径体积分布图(如附图3为实施例1的低钴性材料的粒径体积分布图)。从该分布图中得到：占总体积50％的颗 粒直径大于某Dv50值，另有占总体积50％的颗粒直径小于此Dv50值，则此Dv50值为颗粒的体积平均粒径。
[电池性能测试]
1.正极活性材料的容量性能测定
在25℃下，将扣式电池以0.1C倍率恒流充电至4.35V，再恒压充电至电流小于等于0.05C，之后搁置5分钟，再以0.1C倍率恒流放电至2.8V，此时的放电容量为常温克容量。将扣式电池置于低温-10℃下，按照上述测试得到低温克容量。低温克容量和常温克容量的比值的百分数即为容量保持率。
2.二次电池的直流阻抗DCR测定
在低温-10℃下，将扣式电池以0.1C倍率恒流充电至4.35V，再恒压充电至电流小于等于0.05C，之后将扣式电池调节到20％的荷电状态(SOC)，然后以5C放电10s，记录放电前后的电压降，放电前后的电压降与放电电流的比值即为电池的直流阻抗DCR。
Figure PCTCN2022072067-appb-000001
Figure PCTCN2022072067-appb-000002
与对比例1-3相比，本发明的实施例1-7示出，本发明的单晶低钴三元材料具有较小的中值粒径，不均匀分布的Co元素；从而得到在低温高电压下，具有较小电流阻抗和较高的容量保持率的二次电池。可见，包括本发明的单晶低钴三元材料的二次电池在低温高电压下具有改善的功率和循环性能。
对比例1-3中制备的正极活性材料，其中Co元素均匀分布；即便是对于钴含量相对较高的材料，例如对比例3，其制成的二次电池在低温高电压下的功率和循环性能也较差。
本发明的实施例1-7中正极活性材料中的钴含量相对较低，从而降低了成本；同时，化学式中各元素的摩尔分数满足一定的比例关系且在一定的范围内，则保证正极活性材料兼具较高的结构稳定性；该正极活性材料的粒径大小在1.8μm-3.5μm范围内，使得正极活性材料中锂离子的迁移路径更短，而且，该正极活性材料的单个颗粒中外层的每单位面积的Co含量比内核中的更高，使得表层结构具有较少的Li/Ni混排，其脱嵌锂离子的速率更快，具有在低温下更好的动力学性能。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (16)

  1. 一种单晶结构的低钴三元正极材料，其特征在于，
    所述低钴三元正极材料的化学式为Li 1+x(Ni aCo bMn c) 1-dM dO 2-yA y，其中，M为选自Zr、Sr、B、Ti、Mg、Sn及Al中的一种或多种，A为选自S、N、F、Cl、Br及I中的一种或多种，0≤x≤0.5，0.05≤b≤0.14，3.5≤a/b≤15，0.02≤b×c/a 2≤0.21，a+b+c＝1，0≤d≤0.1，0≤y<0.2；并且
    所述单晶低钴三元正极材料的单个颗粒中，在通过颗粒的几何中心的横截面上，外层的每单位面积的平均Co含量与内核的每单位面积的平均Co含量之间的比例在1.2-5.0:1范围内，可选地在1.4-2.0:1范围内，其中，所述外层是自所述颗粒的表面至朝向颗粒几何中心方向上200nm深度之间的区域，所述内核是以所述颗粒的几何中心为圆心的直径200nm的球面区域。
  2. 根据权利要求1所述的低钴三元正极材料，其特征在于，在所述低钴三元正极材料的颗粒上还具有包覆层，所述包覆层为含Q的氧化物，其中，Q为选自Zr、Sr、B、Ti、Mg、Sn及Al中的一种或多种。
  3. 根据权利要求1或2所述的低钴三元正极材料，其特征在于，所述化学式中，0.5≤a≤0.7。
  4. 根据权利要求1至3中任一项所述的低钴三元正极材料为中值粒径Dv 50在1.6μm-3.6μm范围内、可选地在1.8μm-3.5μm范围内的颗粒。
  5. 根据权利要求1至4中任一项的低钴三元正极材料，其特征在于，所述Q的含量为500-5000ppm，基于含Q的氧化物中Q元素相对于具有包覆层的低钴三元正极材料计。
  6. 一种制备低钴三元正极材料的方法，其特征在于，包括：
    步骤S1：将正极活性材料前驱体、锂盐及含M的化合物混合并烧结，经过破碎得到活性物质颗粒前体1，其中所述正极活性材料前驱体的化学式为(Ni aCo bMn c(OH) 2)，其中3.5≤a/b≤15，0.02≤b×c/a 2≤0.21，a+b+c＝1；0.5≤a≤0.7
    步骤S2：将所述活性物质颗粒前体1与含Co的化合物混合并烧结，得到表层富含Co的活性物质颗粒前体2；回火处理，得到低钴三元正极材料；
    其中，所述低钴三元正极材料为单晶结构，其化学式为Li 1+x(Ni aCo bMn c) 1-dM dO 2-yA y，其中，M为选自Zr、Sr、B、Ti、Mg、Sn及Al中的一种或多种，A为选自S、N、F、Cl、Br及I中的一种或多种，0≤x≤0.5，0.05≤b≤0.14，3.5≤a/b≤15，0.02≤b×c/a 2≤0.21，a+b+c＝1，0≤d≤0.1，0≤y<0.2；并且
    所述单晶低钴三元正极材料的单个颗粒中，在通过颗粒的几何中心的横截面上，外层的每单位面积的平均Co含量与内核的每单位面积的平均Co含量之间的比例在1.2-5.0:1范围内，可选地在1.4-2.0:1范围内，其中，所述外层是自所述颗粒的表面至朝向颗粒几何中心方向上200nm深度之间的区域，所述内核是以所述颗粒的几何中心为圆心的直径200nm的球面区域。
  7. 根据权利要求6所述的方法，其特征在于，步骤S1中所述含M的化合物为选自氧化镁、氧化锶、氧化钛、氧化锡、氧化锆、氧化铝及氧化硼中的一种或多种，可选为氧化锆、氧化锶或氧化镁。
  8. 根据权利要求6或7所述的制备方法，其特征在于，在所述步骤S2中，还包括步骤S2a：将表层富含Co的活性物质颗粒前体2用含Q的氧化物进行包覆。
  9. 根据权利要求8所述的方法，其特征在于，步骤S2a中含Q的氧化物为选自氧化铝、氧化锡、氧化锆、氧化硼及氧化钛中的一种或多种，可选为氧化钛。
  10. 根据权利要求6至9中任一项所述的方法，其特征在于，步骤S2中所述含Co的化合物为选自氢氧化钴、羟基氧化钴、氧化钴、醋酸钴或草酸钴中的一种或多种。
  11. 根据权利要求6至10的制备方法，其特征在于，步骤S2中，所述含Co的化合物的加入量，使得其中加入Co元素的摩尔量与步骤S1获得的正极活性材料前驱体中金属元素Ni、Co、Mn的总摩尔量的比例为0.005-0.05：1，可选地为0.01-0.03：1。
  12. 根据权利要求6至11中任一项所述的方法，其特征在于，步骤S2中烧结温度在650-750℃范围，可选地在700-720℃范围内，烧结时间为2-8h，可选为4-5h。
  13. 一种二次电池，其特征在于，
    包括权利要求1～5中任一项所述的低钴三元正极材料或通过权利要求6～12中任一项所述的方法制备的低钴三元正极材料。
  14. 一种电池模块，其特征在于，包括权利要求13所述的二次电池。
  15. 一种电池包，其特征在于，包括权利要求14所述的电池模块。
  16. 一种用电装置，其特征在于，包括选自权利要求13所述的二次电池、权利要求14所述的电池模块或权利要求15所述的电池包中的至少一种。
PCT/CN2022/072067 2022-01-14 2022-01-14 一种单晶低钴三元材料及其制备方法、二次电池、电池包、用电装置 WO2023133811A1 (zh)

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