WO2021146893A1 - 高镍正极材料、镍钴前驱体材料及制备方法、锂离子电池 - Google Patents

高镍正极材料、镍钴前驱体材料及制备方法、锂离子电池 Download PDF

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WO2021146893A1
WO2021146893A1 PCT/CN2020/073424 CN2020073424W WO2021146893A1 WO 2021146893 A1 WO2021146893 A1 WO 2021146893A1 CN 2020073424 W CN2020073424 W CN 2020073424W WO 2021146893 A1 WO2021146893 A1 WO 2021146893A1
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cathode material
nickel
salt
nickel cathode
high nickel
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French (fr)
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江浩
李春忠
胡彦杰
余海峰
朱华威
黄君涛
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GUANGDONG GUANGHUA SCI-TECH Co Ltd
East China University of Science and Technology
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GUANGDONG GUANGHUA SCI-TECH Co Ltd
East China University of Science and Technology
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G45/00—Compounds of manganese
    • C01G45/12—Complex oxides containing manganese and at least one other metal element
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • 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
    • 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
    • H01M4/485—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
    • H01M4/50—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
    • 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
    • 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 invention relates to a high-nickel cathode material, a nickel-cobalt precursor material and a preparation method, and a lithium ion battery.
  • the cathode material is the key to ensuring the excellent performance of lithium-ion batteries.
  • the currently commonly used cathode materials in power batteries are mainly lithium iron phosphate and ternary cathode materials. Lithium iron phosphate is difficult to meet the requirements of battery energy density due to its low specific capacity, while ternary cathode materials are cycled due to poor stability. There is a lack of life. Therefore, further development of lithium-ion battery cathode materials with high energy density and long cycle life is very important for the development of electric vehicles and the electrochemical energy storage industry.
  • High nickel cathode materials have attracted much attention because of their high nickel ion content and their ability to contribute higher specific capacity under the same potential. However, higher nickel content is accompanied by more ion mixing and more serious structural deterioration, resulting in poor cycle performance.
  • the excessive introduction of inert elements will sacrifice the specific capacitance of the material, and will hinder the transmission of lithium ions to a certain extent, affecting the rate performance.
  • the construction of the surface coating layer can effectively prevent the unfavorable components in the electrolyte from eroding the active material to improve the durability of the material.
  • most of the surface coating is formed by liquid phase mixing or solid phase ball milling, which is difficult Form a high nickel cathode material with a uniform coating on the surface
  • the high nickel cathode material in the prior art is difficult to form a gradient doping of inert elements in the primary particles, or it is difficult to form a material with a uniform and complete coating layer on the surface. Moreover, there is no related report on the high nickel cathode material that can simultaneously form inert element gradient doping and uniform coating layer on the surface of primary particles.
  • Cipheral Patent Document CN104966820A discloses a nickel-cobalt-manganese-coated nickel-cobalt-aluminum composite precursor material. The pH is not controlled during the preparation process, and the coating layer formed on the surface is not uniform, and there is no Form a gradient doping of inert elements.
  • the technical problem to be solved by the present invention is to overcome the excessive introduction of inert elements in the prior art, reduce the specific capacity of the high nickel cathode material, hinder the lithium ion transmission, thereby affecting the rate performance; and it is difficult to prepare a uniform and complete surface.
  • the high nickel positive electrode material of the coating layer leads to the defect of poor durability of the high nickel positive electrode material, and a high nickel positive electrode material, a nickel cobalt precursor material and a preparation method, and a lithium ion battery are provided.
  • the high nickel positive electrode material of the present invention forms a gradient doping of inert elements in the primary particles, and the surface of the high nickel positive electrode material is a uniform and complete coating layer; the H2-H3 phase transition during the electrochemical reaction is effectively suppressed, It alleviates the erosion of the unfavorable components in the electrolyte to the active material, and increases the diffusion rate of lithium ions at the interface; thus, the high nickel cathode material has high specific capacity, good cycle stability, high rate performance, and high rate performance. The current density can still maintain a higher specific capacity.
  • the present invention solves the above technical problems through the following technical solutions.
  • the present invention provides a high nickel cathode material.
  • the chemical formula of the high nickel cathode material is LiNi x Co y M 1-xy O 2 , where 0.6 ⁇ x ⁇ 0.9955, 0 ⁇ y ⁇ 0.3955, 0.0045 ⁇ 1- xy ⁇ 0.06;
  • the high nickel cathode material has a core-shell structure;
  • the core is formed by agglomeration of primary particles doped with M element gradient
  • the M element includes Al element and/or Mn element
  • Each of the primary particles contains a solid sphere and a hollow sphere, the center of the solid sphere or the center of the hollow sphere is the center of the primary particle; the radius of the solid sphere is the radius of the primary particle.
  • the outer spherical surface of the hollow sphere is the spherical surface of the primary particle, and the thickness of the spherical shell of the hollow sphere is 0-1/6 of the radius of the primary particle but not 0;
  • the content of the element M decreases in order;
  • the total molar amount of the element M in all the solid spheres in the high nickel cathode material is equal to that of the high nickel cathode material
  • the ratio of the total molar amount of all the elements in it is 0.075% to 0.75%;
  • the ratio of the molar amount of M element in the solid sphere to the molar amount of M element in the hollow sphere is 1/3 to 1/2;
  • the shell of the high nickel cathode material is LiAlO 2 and/or LiMn 2 O 4 ; the mass of the shell of the high nickel cathode material accounts for 0.2% to 5% of the total mass of the high nickel cathode material.
  • the value of x is preferably 0.6 ⁇ x ⁇ 0.95, more preferably 0.85 to 0.94, such as 0.659, 0.816, 0.824, 0.962 or 0.936.
  • the value of y is preferably 0.04-0.3, more preferably 0.04-0.1, such as 0.049, 0.096, 0.144, 0.145 or 0.283.
  • the value of 1-xy is preferably 0.015 to 0.06, more preferably 0.015 to 0.042, such as 0.015, 0.031, 0.04, 0.042 or 0.058.
  • the chemical formula of the high nickel cathode material is LiNi 0.862 Co 0.096 Al 0.042 O 2 , LiNi 0.824 Co 0.145 Al 0.031 O 2 , LiNi 0.659 Co 0.283 Al 0.058 O 2 , LiN 0.936 Co 0.049 Al 0.015 O 2 , LiNi 0.816 Co 0.144 Al 0.04 O 2 or LiNi 0.824 Co 0.145 Mn 0.031 O 2 .
  • the chemical formula of the high nickel cathode material is LiNi x Co y Al 1-xy O 2 , wherein the chemical formula of the shell of the high nickel cathode material is LiAlO 2 .
  • the chemical formula of the high nickel cathode material is LiNi x Co y Mn 1-x- y O 2 , wherein the chemical formula of the shell of the high nickel cathode material is LiMn 2 O 4 .
  • the morphology of the high nickel cathode material may be conventional in the art, for example, including rod shape, sheet shape or spherical shape, preferably spherical shape.
  • the core is a microsphere formed by agglomeration of primary particles.
  • the particle size of the high nickel cathode material may be 6-20 ⁇ m.
  • the space group of the core may be the R-3m space group.
  • the morphology of the primary particles may be spherical or ellipsoidal. If the morphology of the primary particles is not spherical or ellipsoidal, such as rod-shaped, it is difficult to form gradient doping of inert elements, and the high nickel cathode material of the present invention cannot be obtained. It should be noted that the shape of the primary particles in this field is usually consistent with the shape of nickel and cobalt hydroxide.
  • the particle size of the primary particles may be 200-900nm, preferably 300nm, 400nm, 500nm, 600nm or 800nm.
  • the type of the M element is preferably Al element and/or Mn element.
  • the radius of the solid sphere is preferably 1/20 to 1/5 of the radius of the primary particle, more preferably 1/15 to 1/6, such as 1/6, 1/7, 1 /8, 1/9, 1/10, 1/12, 1/14, or 1/15.
  • the thickness of the spherical shell of the hollow sphere is preferably 1/20 to 1/6 of the radius of the primary particle, such as 1/7, 1/8, 1/9, 1/10, 1/ 12, 1/14, 1/15, 1/16, or 1/18. It should be noted that the hollow sphere in the present invention is a hollow sphere surrounded by the spherical shell.
  • the inventors have found through many experiments that, in the primary particles, the content of the M element in the solid sphere or the hollow sphere, if it is too large, will reduce the specific capacity of the high nickel cathode material, and if it is too small, Unable to stabilize the crystal structure. For example, if the ratio of the total molar amount of the M element in all the solid spheres in the high nickel cathode material to the total molar amount of all elements in the high nickel cathode material is greater than 0.75%, the high nickel If the specific capacitance of the positive electrode material is less than 0.075%, the crystal structure cannot be stabilized.
  • the ratio of the total molar amount of the M element in all the solid spheres in the high nickel cathode material to the total molar amount of all elements in the high nickel cathode material is preferably 0.15% to 0.6%, such as 0.15%, 0.375%, 0.53 or 0.6%.
  • the molar amount of the M element in the solid sphere and the molar amount of the M element in the hollow sphere are preferably 0.35-0.5, such as 0.353, 0.4, 0.407, 0.455 or 0.5.
  • the ratio of the total molar amount of the M element in all the hollow spheres in the high nickel cathode material to the total molar amount of all elements in the high nickel cathode material is preferably 0.15% to 2%, more preferably 0.4 % ⁇ 1.5%, such as 0.425%, 0.825%, 1.05%, 1.25% or 1.475%.
  • the space group of the shell of the high nickel cathode material may be P4212; when the shell of the high nickel cathode material is LiMn2O4, the high nickel cathode The space group of the shell of the material can be Fd-3m.
  • the inventor also found through many experiments that the mass ratio of the shell mass of the high nickel cathode material to the total mass of the high nickel cathode material, if too large (for example, greater than 5%), will increase the interface impedance, thereby reducing The rate performance of the high nickel cathode material reduces the specific capacity; if it is too small (for example, less than 0.2%), it cannot protect the material from corrosion.
  • the mass of the shell of the high nickel cathode material preferably accounts for 0.2%, 0.5%, 1.4%, 1.7%, 2.3% or 5% of the total mass of the high nickel cathode material, preferably It is 0.2% to 3%.
  • the thickness of the shell of the high nickel cathode material may be 1-10 nm, for example, 3 nm.
  • the value of I 003 /I 104 in the XRD pattern test result of the high nickel cathode material may be greater than 1.4.
  • I 003 is the peak 003 in the XRD pattern
  • I 104 is the peak 104 in the XRD pattern.
  • the present invention also provides a method for preparing a nickel-cobalt precursor material, which includes the following steps:
  • the chemical formula of the nickel-cobalt-aluminum precursor material is Ni n Co z M 1-nz (OH) 2 , where 0.6 ⁇ n ⁇ 0.9955, 0 ⁇ z ⁇ 0.3955, 0.0045 ⁇ 1-nz ⁇ 0.06;
  • the M salt is a metal salt
  • the types of the metal salt include Al salt and/or Mn salt
  • the complexing agent is a bidentate ligand
  • the pH value during the mixing reaction is 8-10.
  • the preparation method of the "mixed solution of M salt and complexing agent" can be conventional in the art, and can be prepared according to the following steps: Mix the M salt solution with the complexing agent.
  • the solvent in the "mixed solution of M salt and complexing agent" may be a conventional solvent in the art, usually deionized water.
  • the molar ratio of the M salt and the complexing agent can be conventional in the art, preferably (1-5):1, for example, 1. :1, 2:1, 3:1 or 5:1.
  • the type of the bidentate ligand may be a conventional type in the art.
  • it may include one or more of oxalate-containing compounds, ethylenediamine, and 2,2'-bipyridine.
  • the type of the oxalate-containing compound may be a conventional type in the art, and preferably includes ammonium oxalate and/or sodium oxalate.
  • the molar ratio of the oxalate-containing compound to the M salt may be (1-5):1, such as 1:1, 2:1 or 5:1.
  • the molar ratio content of the ethylenediamine to the M salt may be (1-5):1, for example, 3:1.
  • the concentration of the M salt solution can be conventional in the art, preferably 1 to 5 mol/L, for example, 2 mol/L or 4 mol/L.
  • the type of M salt is preferably Al salt and/or Mn salt.
  • the type of the aluminum salt may be the type of aluminum salt conventional in the art, preferably including one or more of aluminum sulfate, aluminum chloride and aluminum nitrate, such as aluminum sulfate, Aluminum chloride or aluminum nitrate.
  • the type of the manganese salt may be conventional in the art, and usually includes one or more of manganese sulfate, manganese hydrochloride, manganese nitrate, and manganese acetate, such as manganese sulfate.
  • the operation of stirring the "mixed solution of M salt and complexing agent" is further included before the mixing reaction.
  • the agitation is to prevent the complexing agent and the metal salt from forming a chelate compound, agglomeration and precipitation, and it is difficult to obtain the high nickel positive electrode material of the present invention.
  • the stirring is generally so that the "mixed solution of M salt and complexing agent" does not form a precipitate.
  • the rotation speed of the stirring can be conventional in the art, for example, 10 to 1000 r/min.
  • Ni x Co y (OH) 2 dispersion is added to the "mixed solution of M salt and complexing agent"
  • the present invention will not be obtained in the end.
  • the high nickel cathode material That is, it is impossible to form a uniform and complete coating layer with a specific content on the surface, and gradient doping of a specific content of inert elements in the primary particles.
  • the rate at which the "mixed solution of M salt and complexing agent" is added to the Ni n Co z (OH) 2 dispersion has a greater impact on the integrity or uniformity of the coating layer. If the adding speed of the "mixed solution of M salt and complexing agent" is too slow, it is not conducive to forming a complete coating layer, and if it is too fast, the concentration of the mixed reaction system is too high, and it is difficult to control the coating uniformity.
  • the adding rate is 1-20 mL/min, more preferably 1-10 mL/min, such as 1 mL/min, 2 mL/min, 5 mL/min, or 10 mL/min.
  • the method of adding the "mixed solution of M salt and complexing agent" to the Ni n Co z (OH) 2 dispersion can be conventional in the art, as long as the addition of 1-20 mL/min can be maintained
  • the rate may be sufficient, for example, it may be a dripping method.
  • n in Ni n Co z M 1-nz (OH) 2 corresponds to the value of x in the high nickel cathode material LiNi x Co y M 1-xy O 2 .
  • the value of x should be equal to the value of n.
  • the value of x will be less than the value of n due to the inevitable trace loss during the preparation process.
  • the value of y will be smaller than the value of z due to the inevitable trace loss during the preparation process.
  • n in the Ni n Co z (OH) 2 , the value of n can be reasonably selected according to the required high nickel cathode material, preferably 0.7 to 0.95, such as 0.7, 0.85, 0.9 or 0.95.
  • the value of z can be reasonably selected according to the required high nickel cathode material, preferably 0.05 to 03, such as 0.05, 0.1, 0.15 or 0.3.
  • the Ni n Co z (OH) 2 is Ni 0.9 Co 0.1 (OH) 2 , Ni 0.85 Co 0.15 (OH) 2 , Ni 0.7 Co 0.3 (OH) 2 or Ni 0.95 Co 0.05 (OH) 2 .
  • the preparation method of the Ni n Co z (OH) 2 dispersion can be conventional in the art, and usually includes the following steps: disperse the Ni n Co z (OH) 2 in a solvent, adjust the pH value, and stir That's it.
  • the solvent in the Ni n Co z (OH) 2 dispersion may be conventional in the art, and is usually deionized water.
  • the concentration of the Ni n Co z (OH) 2 dispersion can be a conventional concentration in the field, preferably 1-20 wt%, for example, 1.96 wt%, 4.76 wt%, 5 wt%, 9.1 wt% , 14wt% or 19.61wt%.
  • the pH value of the Ni n Co z (OH) 2 dispersion is preferably 8-10, more preferably 8-9.8, such as 9 or 9.5.
  • the process of the mixing reaction generally also includes the process of adding the "mixed solution of M salt and complexing agent" to the Ni n Co z (OH) 2 dispersion. .
  • the inventors have found through many experiments that only by controlling the pH value of the mixing reaction process within the range of 8-10, together with other necessary technical conditions in the present invention, can the surface of the nickel cobalt hydroxide be made uniform. Cover 3 layers of Al(OH). If the pH value is too low (for example, lower than 8), the coating is insufficient, and the pH value is too high (for example, above 10) and the coating is not uniform.
  • the pH value is preferably 8 to 9.8, such as 9 or 9.5.
  • the type of the pH adjusting agent can be a base that is conventional in the art and does not react with aluminum ions.
  • the pH adjuster is usually a basic compound capable of ionizing hydroxide ions in water, such as one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide and ammonia, preferably It is ammonia water.
  • the pH adjusting agent is generally added in the form of a solution.
  • the concentration of the ammonia water may be a conventional concentration in the art, preferably 0.3 to 3 mol/L.
  • the way to control the pH value is preferably to maintain the flow rate of the pH regulator during the addition and mixing reaction, and the flow rate is preferably 1 ⁇ 20mL/min.
  • the operation and conditions of the mixing reaction may be conventional operations and conditions in the art, and usually stirring.
  • the stirring speed can be a conventional stirring speed in the art, preferably 200-800 r/min.
  • the mixing reaction time can be conventional in the art, preferably 2-10h, for example 4h, 5h or 6h.
  • the nickel-cobalt precursor material is a nickel-cobalt-aluminum precursor material.
  • the mass of aluminum hydroxide in the nickel-cobalt-aluminum precursor material accounts for 0.2%-10% of the total mass of the nickel-cobalt-aluminum precursor material.
  • the nickel-cobalt precursor material is a nickel-cobalt-manganese precursor material.
  • the mass of manganese hydroxide in the nickel-cobalt-manganese precursor material accounts for 0.2%-10% of the total mass of the nickel-cobalt-manganese precursor material.
  • the present invention provides a nickel-cobalt precursor material, which is prepared by the above-mentioned preparation method.
  • the present invention provides a method for preparing the above-mentioned high nickel cathode material, which comprises the following steps: sintering the above-mentioned mixture of the nickel-cobalt precursor material and the lithium salt.
  • the molar ratio of the nickel-cobalt precursor material to the lithium salt can be conventional in the art, and is preferably 1:(1 to 1.2), for example, 1:1.08, 1:1.05 or 1:1.1.
  • the type of the lithium salt can be conventional in the art, and is usually lithium hydroxide.
  • the sintering operation and conditions can be conventional operations and conditions in the art.
  • the sintering temperature may be 700-900°C, for example 800°C.
  • the heating rate during the sintering process may be 4-6°C/min, for example 5°C/min.
  • the sintering time may be 10-18h, for example 12h or 15h.
  • the sintering equipment is usually a tube furnace.
  • the present invention provides a lithium ion battery, the precursor of the positive electrode material is the aforementioned nickel-cobalt precursor material; or, the positive electrode material is the aforementioned high-nickel positive electrode material.
  • the "high nickel” in the high nickel cathode material refers to the chemical formula of the high nickel cathode material LiNi x Co y Al 1-xy O 2 where x is greater than 0.6.
  • the reagents and raw materials used in the present invention are all commercially available.
  • the present invention combines the specific complexing agent, the feeding sequence, and the specific pH value in the reaction system and other processes, and finally obtains the core-shell structure high nickel cathode material of the present invention.
  • the high nickel cathode material a specific content of aluminum and/or manganese is gradually doped in the primary particles, and the specific content of the coating layer forms a uniform and complete shell.
  • the core of the high nickel cathode material can still be the R-3m space group, without destroying the crystal structure of the high nickel cathode material; the shell can be the P4212 space group or the Fd-3m space group.
  • the value of I 003 /I 104 in the XRD pattern test result can be greater than 1.4.
  • the high-nickel positive electrode material of the present invention reduces the loss of specific capacity of the high-nickel positive electrode material caused by the introduction of inert elements, and also improves the migration rate of the material bulk. At the same time, it can alleviate the erosion of the unfavorable components in the electrolyte to the active material, significantly reduce the interface impedance, and increase the transmission rate of lithium ions at the interface. And it can effectively inhibit the H2-H3 phase transition in the electrochemical reaction process.
  • the high-nickel cathode material of the present invention has higher specific capacity, good cycle stability, better rate performance, and can still maintain a higher specific capacity at a current density of a large rate.
  • the present invention adopts the method of combining liquid phase coating and high temperature calcination to realize the preparation of kilogram-level materials.
  • the preparation method has the advantages of simple process, low energy consumption, short cycle, and suitability for industrial production.
  • FIG. 1 is a SEM morphology diagram of the nickel-cobalt-aluminum precursor material obtained in Example 1.
  • FIG. 1 is a SEM morphology diagram of the nickel-cobalt-aluminum precursor material obtained in Example 1.
  • FIG. 3 is a SEM morphology diagram of the nickel-cobalt-aluminum precursor material obtained in Comparative Example 3.
  • FIG. 3 is a SEM morphology diagram of the nickel-cobalt-aluminum precursor material obtained in Comparative Example 3.
  • FIG. 5 is an X-ray diffraction pattern of the high nickel cathode material of Example 1.
  • Fig. 6 is a simulated distribution diagram of solid spheres and hollow spheres of primary particles in Examples 1 to 6.
  • FIG. 7 is a slice EDS line scan diagram and element distribution diagram of the high nickel cathode material of Example 1.
  • FIG. Fig. 7a is a sliced EDS line scan diagram of the high nickel cathode material
  • Fig. 7b is the element distribution diagram of the high nickel cathode material.
  • FIG. 8 is a scanning electron microscope and a transmission electron microscope image of the high nickel cathode material of Example 1.
  • FIG. 8a is a scanning electron microscope image of the surface of the high nickel cathode material of Example 1
  • FIG. 8b is a transmission electron microscope image of the surface of the high nickel cathode material of Example 1.
  • Example 9 is a test result of the rate and cycle performance of the high nickel cathode material obtained in Example 1 used as the cathode material of a lithium ion battery.
  • Fig. 10 is a comparison diagram of the charge-discharge curve and the first-round charge-discharge curve of Example 1 and Comparative Example 1.
  • R1 is the radius of the solid sphere
  • 2 is the hollow sphere
  • R2 is the thickness of the spherical shell of the hollow sphere
  • 3 is the primary particle
  • R is the radius of the primary particle.
  • a 1 mol/L aluminum sulfate aqueous solution is prepared, and ethylene diamine is added to mix well.
  • the molar ratio of ethylene diamine to aluminum sulfate is 3:1 to obtain a mixed solution of aluminum sulfate and ethylene diamine.
  • Stir the mixed solution before adding it so that it will not form a precipitate, and the rotating speed of stirring is 10-1000 r/min.
  • Ni 0.824 Co 0.145 Al 0.031 O 2 The chemical formula of the material is LiNi 0.824 Co 0.145 Al 0.031 O 2 .
  • the molar ratio of sodium oxalate to aluminum sulfate is 5:1 to obtain a mixed solution of aluminum sulfate and ammonium oxalate.
  • Stir the mixed solution before adding is 10-1000r/min.
  • the chemical formula of the material is LiNi 0.659 Co 0.283 Al 0.058 O 2 .
  • the molar ratio of 2,2'-bipyridine to aluminum nitrate is 1:1 to obtain aluminum nitrate and 2,2'-bipyridine.
  • the mixed solution of pyridine is stirred before adding the mixed solution so that no precipitation is formed, and the stirring speed is 10 to 1000 r/min.
  • the "mixed solution of ammonium oxalate and aluminum chloride" was added to the nickel-cobalt-aluminum hydroxide dispersion at a rate of 20mL/min, during which the flow rate of ammonia was controlled to be 1-20mL/min and the concentration of ammonia to be 0.3-3mol/ L thus controls the pH of the entire reaction system to 9.0.
  • stirring is continued at a speed of 200-800 r/min for 10 hours, and the precursor material is obtained by filtration and drying, in which aluminum hydroxide accounts for 5% of the total mass of the precursor material.
  • the chemical formula of the high nickel cathode material It is LiNi 0.816 Co 0.144 Al 0.04 O 2 .
  • the high nickel cathode materials obtained in Examples 1 to 5 are all core-shell structures.
  • the core is a microsphere formed by agglomeration of primary particles. Within the primary particles, the content of aluminum element decreases successively and presents a gradient distribution from the outside to the inside; the shell is a LiAlO 2 coating layer with a chemical formula.
  • the molar ratio of ethylenediamine to manganese sulfate is 3:1 to obtain a mixed solution of manganese sulfate and ethylenediamine.
  • Before adding the mixed solution Stir it so that it will not form a precipitate, and the speed of stirring is 10-1000r/min.
  • the chemical formula of the material is LiNi 0.824 Co 0.145 Mn 0.031 O 2 .
  • the high nickel cathode material of this embodiment has a core-shell structure.
  • the core is a microsphere formed by agglomeration of primary particles.
  • the content of manganese element decreases sequentially from outside to inside, and the shell is a coating layer with a chemical formula of LiMn 2 O 4.
  • Ni 0.65 Co 0.35 (OH) 2 Disperse 5 g of Ni 0.65 Co 0.35 (OH) 2 in 50 mL of deionized water to obtain a Ni 0.65 Co 0.35 (OH) 2 dispersion.
  • the preparation concentration is 2mol/L aluminum sulfate aqueous solution.
  • the aluminum sulfate aqueous solution was added to the Ni 0.65 Co 0.35 (OH) 2 dispersion at a rate of 1 mL/min. After the feeding is completed, stirring is continued for 4 hours, and the precursor material is obtained by filtration and drying, in which aluminum hydroxide accounts for 7% of the total mass of the precursor.
  • the precursor and LiOH were ground and mixed, and then calcined at 800°C for 12 hours in an oxygen atmosphere to obtain a high nickel cathode material.
  • the high nickel cathode material does not form a core-shell structure, and does not form a gradient doping of aluminum element inside the primary particles.
  • Example 1 The pH values in Example 1 were all set to 12, and the other parameters were the same as in Example 1.
  • the high nickel cathode material of this comparative example does not form a gradient doping of aluminum element in the primary particles, and does not form a coating layer on the surface of the microspheres formed by agglomeration of the primary particles.
  • the inventors found through many experiments that if the pH value is not between 8-10, it is impossible to uniformly coat a layer of lithium metaaluminate on the surface of the material. If the pH is too low, a complete coating layer cannot be formed, and if the pH is too high, the coating will be uneven, which will have a significant impact on the electrochemical performance of the final high nickel cathode material.
  • Example 1 On the basis of Example 1, the complexing agent was replaced with the tetradentate ligand EDTA, and the remaining parameters were the same as in Example 1. In this comparative example, no surface coating was obtained at this pH using EDTA. No core-shell structure is formed, and no gradient doping of aluminum is formed inside the primary particles.
  • Example 1 On the basis of Example 1, the complexing agent was replaced with the monodentate ligand sodium thiocyanate, and the remaining parameters were the same as in Example 1. No coating layer was formed on the surface of the high nickel cathode material of this comparative example.
  • Example 1 Perform SEM inspection on the nickel-cobalt-aluminum precursor material in Examples 1 to 5 and the nickel-cobalt-manganese precursor material in Example 6. It can be obtained that the surface of the nickel-cobalt-aluminum precursor material in Examples 1 to 5 is a uniform and complete Al(OH) 3 layer, and the surface of the nickel-cobalt-manganese precursor material in Example 6 is uniform and complete Mn(OH) 2 Floor.
  • the SEM image of the nickel-cobalt-aluminum precursor material of Example 1 is shown in FIG. 1.
  • the SEM image of the nickel-cobalt-aluminum precursor material in Comparative Example 2 is shown in FIG. 2.
  • No Al(OH) 3 layer is formed on the surface, and no lithium metaaluminate layer is formed after sintering.
  • the SEM image of the nickel-cobalt-aluminum precursor material in Comparative Example 3 is shown in FIG. 3, and no Al(OH) 3 layer is formed on the surface.
  • the SEM image of the nickel-cobalt-aluminum precursor material in Comparative Example 4 is shown in FIG. 4, and no Al(OH) 3 layer is formed on the surface.
  • the space group of the core of the high nickel cathode material of Examples 2 to 4 is also the R-3m space group, and the space group of the shell is also P4212, and the ratio of peak 003 to peak 104 is greater than 1.4.
  • the crystal structure of the high nickel cathode material is not Change.
  • the space group of the core of the high nickel cathode material of Example 6 is R-3m, and the ratio of the peak 003 to the peak 104 is greater than 1.4, the space group of the shell is the Fd-3m space group, and the crystal structure of the high nickel cathode material remains unchanged.
  • the ICP test was performed on the high nickel cathode materials of Examples 1 to 6. The test results are shown in Table 1 below. Table 1 shows that, for example, the ICP test results are similar to the high nickel cathode material LiNi 0.862 in Example 1 of the present invention. The composition of Co 0.096 Al 0.042 O 2 is consistent. Among them, the ICP model is ICP-AES and Agilent 725.
  • the shape of the primary particles in Examples 1 to 6 is spherical or ellipsoidal. Taking a sphere as an example, as shown in Figure 6, the solid sphere 1 and the hollow sphere 2 are both spheres concentric with the primary particle 3.
  • the radius of 1 is R1
  • the spherical surface of the hollow sphere 2 is the spherical surface of the primary particle 3
  • the thickness of the spherical shell of the hollow sphere 2 is R2
  • the radius of the primary particle 3 is R.
  • the EDS energy spectrum test was performed on the high nickel cathode materials of Examples 1 to 6, and the distribution diagrams of the elements in the primary particles of each example were obtained.
  • the SEM test was performed on the high nickel cathode materials of Examples 1 to 6, and the particle size of the primary particles was measured. The test results are shown in Table 2 below.
  • the sliced EDS line scan of the high nickel cathode material of Example 1 is shown in Figure 7a.
  • the arrow in Figure 7a is the line scan path of the primary particles.
  • the distribution of aluminum in the primary particles is as follows Shown in Figure 7b.
  • the ratio of the total molar amount of aluminum in all hollow spheres in the high nickel cathode material of Example 1 to the molar amount of all elements in the high nickel cathode material is 1.25%; the high nickel cathode of Example 1
  • the ratio of the total moles of aluminum in all solid spheres to the total moles of all elements in the high nickel cathode material is 0.5%; in the primary particles, the aluminum element gradually decreases from the outside to the inside, showing a gradient distribution.
  • the molar ratio of aluminum in the solid sphere to the hollow sphere is 0.4.
  • FIG. 8 is a scanning electron microscope and a transmission electron microscope image of the surface of the high nickel cathode material of Example 1
  • FIG. 8a is a scanning electron microscope image of the surface of the high nickel cathode material of Example 1
  • FIG. 8b is a surface of the high nickel cathode material of Example 1.
  • the surface of the high nickel cathode material has a uniform lithium metaaluminate coating layer.
  • the thickness of the lithium metaaluminate coating layer observed in the figure is 3nm, which is a uniform and complete coating
  • the lattice spacing of the coating layer is 0.217 nm, which corresponds to the (211) crystal plane of lithium metaaluminate.
  • the surface of the high nickel cathode material in Examples 1 to 6 was subjected to X-ray photoelectron spectroscopy analysis test, and the mass ratio of the shell of the high nickel cathode material and the total mass of the high nickel cathode material in each example was measured as shown in Table 2 below.
  • the particle size of the high nickel cathode material of Examples 1 to 6 was tested by a laser particle size analyzer.
  • the test results of the particle size of the high nickel cathode material of each example are shown in Table 2 below.
  • the molar ratio of aluminum or manganese in the solid sphere to the high nickel cathode material refers to the total molar amount of aluminum or manganese in all solid spheres in the high nickel cathode material. The ratio of the total moles of all elements.
  • the molar ratio of aluminum or manganese in the hollow sphere to the high nickel cathode material refers to the total molar amount of aluminum or manganese in all hollow spheres in the high nickel cathode material and the total molar amount of all elements in the high nickel cathode material Ratio.
  • Electrochemical performance test conditions CR2016 button cell assembly and test:
  • the high nickel cathode material, carbon black, and PVDF (polyvinylidene fluoride) obtained in the above Examples 1 to 6 and Comparative Examples 1 to 4 are in accordance with 8:1 :1 mass ratio is made into a slurry and coated on the aluminum foil, the dried aluminum foil loaded with the slurry is cut into a small disc with a diameter of about 1.2cm using a cutting machine to be used as a positive electrode, and a metal lithium plate is used as a negative electrode , Celgard 2400 is a diaphragm, 1M mixed organic solution is electrolyte (wherein, the solvent is a mixture solution of ethylene carbonate and ethylene dimethyl carbonate with a volume ratio of 3:7, and the solute is LiPF 6 ), in an argon glove box Assemble into CR2016 button battery.
  • the obtained battery was tested for rate performance and cycle performance in electrochemical performance at a temperature of 2.7-4.3V and
  • FIG. 9 is the test result of the rate and cycle performance of the high nickel cathode material in Example 1
  • FIG. 9a is the test result of the rate performance
  • FIG. 9b is the test result of the cycle performance. From Figure 9a, it can be concluded that at 0.2C, the reversible capacity of the battery is as high as 201mAh/g, and at 20C, the reversible capacity is 120mAh/g.
  • Figure 9b 100 cycles at 1C, the reversible capacity retention rate is as high as 95%, and the reversible capacity is 176mAh/g.
  • Figure 10 is a comparison diagram of the charge-discharge curve and the first-circle charge-discharge curve of the high nickel cathode material of Example 1 and Comparative Example 1.
  • the black circle shows the H2-H3 phase transition characteristic platform, and the H2-H3 phase transition platform in Example 1
  • the weakening indicates that the phase transition is reduced, the structure of the high nickel cathode material is more stable, and the cycle stability is better

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Abstract

本发明公开了高镍正极材料、镍钴前驱体材料及制备方法、锂离子电池。该高镍正极材料为核壳结构；核为梯度掺杂M元素的一次颗粒团聚而成；M包括Al和/或Mn；一次颗粒内含有实心球体和空心球体，实心球体或空心球体的球心为一次颗粒的球心；实心球体的半径为一次颗粒的0～1/5但不为0；空心球体的外球面为一次颗粒的球面，空心球体的球壳的厚度为一次颗粒半径的0～1/6但不为0；一次颗粒内，从外到内，M的含量依次减少；实心球体中M元素与高镍正极材料内所有元素的摩尔比为0.075％～0.75％；实心球体与空心球体中M元素的摩尔比为1/3～1/2；本发明中的高镍正极材料比容量较高、循环稳定性好、倍率性能较佳。

Description

高镍正极材料、镍钴前驱体材料及制备方法、锂离子电池 技术领域
本发明涉及高镍正极材料、镍钴前驱体材料及制备方法、锂离子电池。
背景技术
伴随着电动汽车的日益普及，消费者对其续航里程以及使用寿命的要求越来越高。作为电动汽车的主要动力源，动力锂离子电池的能量密度和循环性能对电动汽车续航和寿命的影响最为直接。其中，正极材料是保证锂离子电池展现优异性能的关键。然而，目前动力电池中常用的正极材料主要是磷酸铁锂和三元正极材料，磷酸铁锂由于较低的比容量难以满足电池能量密度的需求，而三元正极材料由于稳定性较差在循环寿命上有所欠缺。因此，进一步开发兼具高能量密度和长循环寿命的锂离子电池正极材料对电动汽车以及电化学储能行业的发展至关重要。
高镍正极材料因具有高的镍离子含量，在同样的电势下能够贡献更高的比容量而备受关注。但是，更高的镍含量伴随着更多的离子混排以及更严重的结构恶化，从而导致较差的循环性能。研究表明，高镍正极材料在大的放电深度下(>4.15V)，伴随着更多锂离子的脱出，材料的结构会发生H2-H3相变，从而引起一次颗粒各向异性体积膨胀，导致二次颗粒内一次颗粒间的间隙增加。在反复的充放电过程中，随着间隙的增加，更多的活性材料与电解液直接接触，副反应不断增加，引起更严重的结构恶化。
因此，在充放电过程中抑制H2-H3相变发生，并构建保护层阻碍电解液对活性材料的侵蚀是提高高镍正极材料电化学性能的关键。研究表明，在高镍层状正极材料的晶体结构中引入惰性元素，能够有效稳定材料的晶体结构，抑制H2-H3相变的发生，提高材料的循环性能(F.Wu et.al,Improving the reversibility of the H2-H3 phase transitions for layered Ni-rich oxide cathode towards retarded structural transition and enhanced cycle stability,Nano Energy,59,2019,50-57)。但是，惰性元素的过多引入会牺牲材料的比电容量，并会在一定程度上阻碍锂离子的传输，影响倍率性能。除此之外，构建表面包覆层能够有效阻碍电解液中的不利组分对活性材料的侵蚀从而提高材料的耐久性，但是，大部分表面包覆通过液相混合或者固相球磨形成，难以形成表面为均匀包覆层的高镍正极材料
现有技术中的高镍正极材料，难以在一次颗粒内形成惰性元素的梯度掺杂，或者难以形成表面为均匀且完整的包覆层的材料。而且，目前还没有同时可在一次颗粒内形成惰性元素的梯度掺杂以及表面为均匀包覆层的高镍正极材料的相关报道。这主要是由于 Al(OH) 3的溶解度Ksp为10 -33，远远小于Ni(OH) 2(Ksp＝10 -14.7)和Co(OH) 2(Ksp＝10 -14.8)，这导致Al、Ni、Co离子在反应过程中难以做到共同沉淀，因此难以做到Al元素在材料内部有序的分布。例如，中国专利文献CN108428888A公开了一种镍钴铝三元正极材料、以及CN109860542A公开的正极材料。这两篇专利文献均没有在内部形成有序的梯度分布、且在表面没有形成包覆层，在实际使用过程中，无法有效保护材料免受侵蚀。另外，中国专利文献CN104966820A公开了一种镍钴锰包覆型镍钴铝复合前驱体材料，其在制备的过程中没有控制pH，表面形成的包覆层不均匀，且在一次颗粒内也没有形成惰性元素的梯度掺杂。现有技术中存在的这些问题还有待解决。
发明内容
本发明所要解决的技术问题在于克服了现有技术中惰性元素的过多引入降低了高镍正极材料的比容量、阻碍了锂离子传输从而影响了倍率性能；以及难以制备出表面为均匀且完整的包覆层的高镍正极材料，导致高镍正极材料耐久性较差的缺陷，而提供了一种高镍正极材料、镍钴前驱体材料及制备方法、锂离子电池。本发明的高镍正极材料在一次颗粒内形成惰性元素的梯度掺杂，同时高镍正极材料的表面为一均匀且完整的包覆层；有效抑制了电化学反应过程中H2-H3相变，缓解了电解液中的不利组分对活性材料的侵蚀，并增加锂离子在界面处的扩散速率；从而使得高镍正极材料的比容量高、循环稳定性好、倍率性能高，以及在大倍率的电流密度下仍然能保持较高的比容量。
本发明通过以下技术方案解决上述技术问题。
本发明提供了一种高镍正极材料，所述高镍正极材料的化学式为LiNi xCo yM 1-x-yO 2，式中，0.6<x≤0.9955，0≤y≤0.3955，0.0045<1-x-y<0.06；所述高镍正极材料为核壳结构；
其中，所述核为梯度掺杂M元素的一次颗粒团聚而成；
所述M元素包括Al元素和/或Mn元素；
每一所述一次颗粒内含有实心球体和空心球体，所述实心球体的球心或所述空心球体的球心为所述一次颗粒的球心；所述实心球体的半径为所述一次颗粒半径的0～1/5但不为0；所述空心球体的外球面为一次颗粒的球面，所述空心球体的球壳的厚度为所述一次颗粒半径的0～1/6但不为0；
在每一所述一次颗粒内，从外到内，所述M元素的含量依次减少；所述高镍正极材料中所有所述的实心球体中M元素的总摩尔量与所述高镍正极材料内所有元素的总摩尔量的比为0.075％～0.75％；所述实心球体中M元素的摩尔量与所述空心球体中M元素的摩尔量的比为1/3～1/2；
其中，所述高镍正极材料的壳为LiAlO 2和/或LiMn 2O 4；所述高镍正极材料的壳的质量占所述高镍正极材料总质量的0.2％～5％。
在所述LiNi xCo yM 1-x-yO 2中，所述x的值较佳地为0.6<x≤0.95，更佳地为0.85～0.94，例如0.659、0.816、0.824、0.962或0.936。
在所述LiNi xCo yM 1-x-yO 2中，所述y的值较佳地为0.04～0.3，更佳地为0.04～0.1，例如0.049、0.096、0.144、0.145或0.283。
在所述LiNi xCo yM 1-x-yO 2中，所述1-x-y的值较佳地为0.015～0.06，更佳地为0.015～0.042，例如0.015、0.031、0.04、0.042或0.058。
在本发明某较佳地实施方式中，所述高镍正极材料的化学式为LiNi 0.862Co 0.096Al 0.042O 2、LiNi 0.824Co 0.145Al 0.031O 2、LiNi 0.659Co 0.283Al 0.058O 2、LiN 0.936Co 0.049Al 0.015O 2、LiNi 0.816Co 0.144Al 0.04O 2或LiNi 0.824Co 0.145Mn 0.031O 2。
本发明中，当M元素为Al元素时，所述高镍正极材料的化学式为LiNi xCo yAl 1-x-yO 2，其中，所述高镍正极材料的壳的化学式为LiAlO 2。
本发明中，当M元素为Mn元素时，所述高镍正极材料的化学式为LiNi xCo yMn 1-x- yO 2，其中，所述高镍正极材料的壳的化学式为LiMn 2O 4。
本发明中，所述高镍正极材料的形态可为本领域常规，例如包括棒状、片状或球形，较佳地为球形。
当所述的高镍正极材料为球形时，所述核为一次颗粒团聚而成的微球。所述高镍正极材料的粒径可为6～20μm。
本发明中，所述核的空间群可为R-3m空间群。
本发明中，所述一次颗粒的形貌可为球形或椭球形。若一次颗粒的形貌不是球形或椭球形，例如是棒状时则难以形成惰性元素的梯度掺杂，无法得到本发明的高镍正极材料。需要说明的是在本领域内一次颗粒的形状通常是由镍钴氢氧化物的形状是一致的。
本发明中，所述一次颗粒的粒径可为200～900nm，较佳地为300nm、400nm、500nm、600nm或800nm。
本发明中，所述M元素的种类较佳地为Al元素和/或Mn元素。
本发明中，所述实心球体的半径较佳地为所述一次颗粒半径的1/20～1/5，更佳地为1/15～1/6，例如1/6、1/7、1/8、1/9、1/10、1/12、1/14或1/15。
本发明中，所述空心球体的球壳的厚度较佳地为所述一次颗粒半径的1/20～1/6，例如1/7、1/8、1/9、1/10、1/12、1/14、1/15、1/16或1/18。需要说明的是，本发明中所述空心球体是由所述球壳围合成的空心球体。
发明人通过多次实验发现，在所述一次颗粒内，所述M元素在所述实心球体或在所述空心球体的含量，若过大则会降低高镍正极材料的比容量，过小则无法稳定晶体的结构。例如，所述高镍正极材料中所有所述实心球体中M元素的总摩尔量与所述高镍正极材料内所有元素的总摩尔量的比，若大于0.75％，则会降低所述高镍正极材料的比电容，若小于0.075％则无法稳定晶体的结构。
其中，所述高镍正极材料中所有所述实心球体中M元素的总摩尔量与所述高镍正极材料中所有元素的总摩尔量的比较佳地为0.15％～0.6％，例如0.15％、0.375％、0.53或0.6％。
其中，在每一所述一次颗粒内，所述实心球体中M元素的摩尔量与所述空心球体中M元素的摩尔量的比较佳地为0.35～0.5，例如0.353、0.4、0.407、0.455或0.5。
其中，所述高镍正极材料中所有所述空心球体中M元素的总摩尔量与所述高镍正极材料内所有元素总摩尔量的比较佳地为0.15％～2％，更佳地为0.4％～1.5％，例如0.425％、0.825％、1.05％、1.25％或1.475％。
本发明中，当所述高镍正极材料的壳为LiAlO2时，所述高镍正极材料的壳的空间群可为P4212；当所述高镍正极材料的壳为LiMn2O4时，所述高镍正极材料的壳的空间群可为Fd-3m。
发明人通过多次实验还发现，所述高镍正极材料的壳的质量与所述高镍正极材料总质量的质量比，若过大(例如大于5％)则会增加界面阻抗，进而减小高镍正极材料的倍率性能并降低比容量；若过小(例如小于0.2％)，则无法起到保护材料免受侵蚀的作用。
本发明中，所述高镍正极材料的壳的质量较佳地占所述高镍正极材料总质量的比为0.2％、0.5％、1.4％、1.7％、2.3％或5％，较佳地为0.2％～3％。
本发明中，所述高镍正极材料的壳的厚度可为1～10nm，例如3nm。
本发明中，所述高镍正极材料的XRD图谱测试结果中I 003/I 104的值可大于1.4。其中，I 003为XRD图谱中的003峰，I 104为XRD图谱中的104峰。
本发明还提供了一种镍钴前驱体材料的制备方法：其包括以下步骤：
将“M盐和络合剂的混合溶液”加入到Ni nCo z(OH) 2分散液中混合反应，即得；
所述镍钴铝前驱体材料的化学式为Ni nCo zM 1-n-z(OH) 2，式中，0.6<n≤0.9955，0≤z≤0.3955，0.0045<1-n-z<0.06；
其中，所述M盐为金属盐，所述金属盐的种类包括Al盐和/或Mn盐；所述络合剂为双齿配体；
所述混合反应过程中的pH值为8～10。
本发明中，所述“M盐和络合剂的混合溶液”的制备方法可为本领域常规，可按以下步骤制得：将M盐溶液与所述的络合剂混合即可。
其中，所述“M盐和络合剂的混合溶液”中的溶剂可为本领域常规的溶剂，通常为去离子水。
其中，所述“M盐和络合剂的混合溶液”中，所述M盐和所述络合剂的摩尔比可为本领域常规，较佳地为(1～5)：1，例如1:1、2:1、3:1或5:1。
其中，所述双齿配体的种类可为本领域常规的种类。例如可包括含草酸根的化合物、乙二胺和2,2'-联吡啶中的一种或多种。所述含草酸根的化合物的种类可为本领域常规的种类，较佳地包括草酸铵和/或草酸钠。
当所述的双齿配体为含草酸根的化合物时，所述含草酸根的化合物与所述M盐的摩尔比可为(1～5)：1，例如1:1、2:1或5:1。
当所述的双齿配体为乙二胺时，所述乙二胺与所述M盐的摩尔比含量可为(1～5)：1，例如3:1。
其中，所述M盐溶液的浓度可为本领域常规，较佳地为1～5mol/L，例如2mol/L或4mol/L。
其中，所述M盐的种类较佳地为Al盐和/或Mn盐。当M盐为Al盐时，所述铝盐的种类可为本领域常规的铝盐的种类，较佳地包括硫酸铝、氯化铝和硝酸铝中的一种或多种，例如硫酸铝、氯化铝或硝酸铝。当M盐为Mn盐时，所述锰盐的种类可为本领域常规，通常包括硫酸锰、盐酸锰、硝酸锰和醋酸锰中的一种或多种，例如硫酸锰。
本发明中，较佳地，在所述混合反应之前还包括对所述“M盐和络合剂的混合溶液”进行搅拌的操作。所述的搅拌是为了避免所述的络合剂与金属盐形成螯合物后，团聚并沉淀，难以得到本发明的高镍正极材料。
其中，所述的搅拌一般是使得所述“M盐和络合剂的混合溶液”不形成沉淀即可。所述搅拌的转速可为本领域常规，例如10～1000r/min。
本发明中，需要采用如上所述的特定加料顺序，若将Ni xCo y(OH) 2分散液加入到所述“M盐和络合剂的混合溶液”中，最终将得不到本发明的高镍正极材料。即无法形成表面为特定含量的均匀且完整的包覆层，以及特定含量的惰性元素在一次颗粒内的梯度掺杂。
本发明中，所述“M盐和络合剂的混合溶液”加入到所述Ni nCo z(OH) 2分散液中的速率，对包覆层的完整性或均匀性有较大影响。若所述“M盐和络合剂的混合溶液”加入的速度过慢，则不利于形成完整的包覆层，过快，则混合反应体系的浓度过高，难以控制 包覆均匀性。较佳地，所述加入的速率为1～20mL/min，更佳地为1～10mL/min，例如1mL/min、2mL/min、5mL/min、或10mL/min。
其中，所述“M盐和络合剂的混合溶液”加入到所述Ni nCo z(OH) 2分散液中的加入方式，可为本领域常规，只要能够维持1～20mL/min的加入速率即可，例如可为滴加的方式。
需要说明的是，本领域技术人员知晓，Ni nCo zM 1-n-z(OH) 2中的n值与高镍正极材料LiNi xCo yM 1-x-yO 2中的x值相应。在Ni nCo zM 1-n-z(OH) 2镍钴前驱体材料制备高镍正极材料的过程中，镍和钴元素会有微量的损失。理论上x值应当与n值是相等的。但实际操作中，x的值由于制备过程中的不可避免的微量损失会小于n值。同理，y的值由于制备过程中不可避免的微量损失会小于z的值。
本发明中，所述Ni nCo z(OH) 2中，n的值根据所需的高镍正极材料合理的选择即可，较佳地为0.7～0.95，例如0.7、0.85、0.9或0.95。
本发明中，所述Ni nCo z(OH) 2中，z的值根据所需的高镍正极材料合理的选择即可，较佳地为0.05～03，例如0.05、0.1、0.15或0.3。
在本发明的某些较佳地实施方式中，所述的Ni nCo z(OH) 2为Ni 0.9Co 0.1(OH) 2、Ni 0.85Co 0.15(OH) 2、Ni 0.7Co 0.3(OH) 2或Ni 0.95Co 0.05(OH) 2。
本发明中，所述Ni nCo z(OH) 2分散液的制备方法可为本领域常规，通常包括以下步骤：将Ni nCo z(OH) 2分散于溶剂中，调节pH值后，搅拌即可。
本发明中，所述Ni nCo z(OH) 2分散液中的溶剂可为本领域常规，通常为去离子水。
本发明中，所述Ni nCo z(OH) 2分散液的浓度可为本领域常规的浓度，较佳地为1～20wt％，例如1.96wt％、4.76wt％、5wt％、9.1wt％、14wt％或19.61wt％。
本发明中，所述Ni nCo z(OH) 2分散液的pH值较佳地为8～10，更佳地为8～9.8，例如9或9.5。
本发明中，本领域技术人员知晓，所述的混合反应的过程一般还包括在所述“M盐和络合剂的混合溶液”开始加入到Ni nCo z(OH) 2分散液中的过程。
发明人通过多次实验发现，只有将混合反应过程的pH值控制在8～10的范围内，再配合本发明中的其他必要技术条件，才可使得镍钴氢氧化物的表面为均匀的包覆Al(OH) 3层。pH值太低(例如低于8)包覆不充分，pH值过高(例如在10以上)包覆不均匀。所述的pH值较佳地为8～9.8，例如9或9.5。
其中，本领域技术人员知晓，所述pH值通过pH值调节剂调节。
所述pH值调节剂的种类可为本领域常规、且不与铝离子发生反应的碱。所述pH值 调节剂通常为能够在水中电离处氢氧根离子的碱性化合物，例如碳酸钠、碳酸氢钠、氢氧化钠、氢氧化钾和氨水中的一种或多种，较佳地为氨水。其中，所述pH值调节剂一般以溶液的形式添加。
当所述pH值的调节剂为氨水时，所述氨水的浓度可为本领域常规的浓度，较佳地为0.3～3mol/L。
其中，本领域技术人员知晓，控制所述pH值的方式较佳地为保持在加入和混合反应的过程中通入所述pH值的调节剂的流速即可，所述流速较佳地为1～20mL/min。
本发明中，所述混合反应的操作和条件可为本领域常规的操作和条件，通常为搅拌。所述搅拌的转速可为本领域常规的搅拌转速，较佳地为200～800r/min。
本发明中，所述混合反应的时间可为本领域常规，较佳地为2～10h，例如4h、5h或6h。
本发明中，本领域技术人员知晓，所述混合之后通常需要将得到的混合液过滤、干燥。
本发明中，当所述M盐为Al盐时，所述的镍钴前驱体材料为镍钴铝前驱体材料。较佳地，所述镍钴铝前驱体材料中的氢氧化铝的质量占所述镍钴铝前驱体材料总质量的0.2％～10％。
本发明中，当所述M盐为Mn盐时，所述的镍钴前驱体材料为镍钴锰前驱体材料。较佳地，镍钴锰前驱体材料中的氢氧化锰的质量占所述镍钴锰前驱体材料总质量的0.2％～10％。
本发明提供了一种镍钴前驱体材料，其采用上述的制备方法制得。
本发明提供了一种上述高镍正极材料的制备方法，其包括以下步骤：将上述的镍钴前驱体材料与锂盐的混合物，烧结即可。
本发明中，所述镍钴前驱体材料与所述锂盐摩尔比可为本领域常规，较佳地为1：(1～1.2)，例如1：1.08、1：1.05或1：1.1。
本发明中，所述锂盐的种类可为本领域常规，通常为氢氧化锂。
本发明中，所述烧结的操作和条件可为本领域常规的操作和条件。
本发明中，所述烧结的温度可为700～900℃，例如800℃。
本发明中，所述烧结过程中的升温速率可为4～6℃/min，例如5℃/min。
本发明中，所述烧结的时间可为10～18h，例如12h或15h。
本发明中，本领域技术人员知晓，所述烧结的设备通常为管式炉。
本发明提供了一种锂离子电池，其正极材料中的前驱体为上述的镍钴前驱体材料； 或者，其正极材料为上述的高镍正极材料。
本发明中，本领域技术人员均知，所述的高镍正极材料中的“高镍”指的是高镍正极材料LiNi xCo yAl 1-x-yO 2的化学式中的x在0.6以上。
在符合本领域常识的基础上，上述各优选条件，可任意组合，即得本发明各较佳实例。
本发明所用试剂和原料均市售可得。
本发明的积极进步效果在于：
(1)本发明结合特定的络合剂、加料顺序、以及反应体系中特定的pH值等工艺，最终得到了本发明中核壳结构的高镍正极材料。该高镍正极材料中，特定含量的铝元素和/或锰元素在一次颗粒内梯度掺杂，特定含量的包覆层形成了均匀且完整的壳。本发明中高镍正极材料的核仍然可为R-3m空间群，并没有破坏高镍正极材料的晶体结构；壳可为P4212空间群或Fd-3m空间群。且XRD图谱测试结果中I 003/I 104的值可大于1.4。
本发明的高镍正极材料减少了惰性元素的引入带来的高镍正极材料的比容量的损失，也提升材料体相的迁移速率。同时可缓解电解液中的不利组分对活性材料的侵蚀，显著减少了界面阻抗，增加锂离子在界面处的传输速率。且可有效的抑制电化学反应过程H2-H3相变。
(2)本发明中的高镍正极材料的比容量较高、循环稳定性好、倍率性能较佳，在大倍率的电流密度下仍然能保持较高的比容量。
(3)本发明采用液相包覆与高温煅烧相结合的方法，可实现公斤级材料的制备，制备方法具有工艺简单、能耗低、周期短、及适合工业化生产等优点。
附图说明
图1为实施例1得到的镍钴铝前驱体材料的SEM形貌图。
图2为对比例2得到的镍钴铝前驱体材料的SEM形貌图。
图3为对比例3得到的镍钴铝前驱体材料的SEM形貌图。
图4为对比例4得到的镍钴铝前驱体材料的SEM形貌图。
图5是实施例1高镍正极材料的X射线衍射图谱。
图6为实施例1～6中的一次颗粒的实心球体和空心球体的模拟分布图。
图7是实施例1高镍正极材料的切片EDS线扫图以及元素分布图。其中图7a为高镍正极材料的切片EDS线扫图，图7b为高镍正极材料的元素分布图。
图8是实施例1高镍正极材料的扫描电子显微镜和透射电镜图。其中，图8a为实施 例1的高镍正极材料表面的扫描电镜图，图8b为实施例1高镍正极材料表面的透射电镜图
图9是实施例1所得到的高镍正极材料用作锂离子电池正极材料的倍率和循环性能测试结果。
图10为实施例1和对比例1的充放电曲线和首圈充放电曲线的对比图。
图6的附图标记说明：
1为实心球体，R1为实心球体的半径，2为空心球体，R2为空心球体的球壳的厚度，3为一次颗粒，R为一次颗粒的半径。
具体实施方式
实施例1
将5g Ni 0.9Co 0.1(OH) 2分散于去离子水50mL中，用氨水调节pH至9.0，得镍钴铝氢氧化物分散液。配制浓度为2mol/L硫酸铝水溶液，加入草酸铵混匀，草酸铵与硫酸铝的摩尔比为2：1，得硫酸铝和草酸铵的混合溶液。在将该混合溶液在加入之前进行搅拌使其不会形成沉淀，搅拌的转速为10～1000r/min。将“硫酸铝和草酸铵的混合溶液”以1mL/min的速率加入到镍钴铝氢氧化物分散液中，期间控制氨水的流速为1～20mL/min以及氨水的浓度为0.3～3mol/L从而控制整个反应体系的pH为9.0。进料完成后，以200～800r/min的转速持续搅拌4h，过滤干燥得到镍钴铝前驱体材料，其中，氢氧化铝占镍钴铝前驱体材料总质量的7％。将镍钴铝前驱体材料与LiOH的摩尔比为1:1.1的比例研磨混合，在氧气气氛中以5℃/min升温速率升温至800℃煅烧12h，即得高镍正极材料，其化学式为LiNi 0.862Co 0.096Al 0.042O 2。
实施例2
将5g Ni 0.85Co 0.15(OH) 2分散于30mL去离子水中，用氨水调节pH至8.5，得镍钴铝氢氧化物分散液。配制浓度为1mol/L硫酸铝水溶液，加入乙二胺混匀，乙二胺与硫酸铝的摩尔比为3：1，得硫酸铝和乙二胺的混合溶液。在将该混合溶液在加入之前进行搅拌使其不会形成沉淀，搅拌的转速为10～1000r/min。将“硫酸铝和乙二胺的混合溶液”以2mL/min的速率加入到镍钴铝氢氧化物分散液中，期间控制氨水的流速为1～20mL/min以及氨水的浓度为0.3～3mol/L从而控制整个反应体系的pH为8.5。进料完成后，以200～800r/min的转速持续搅拌6h，过滤干燥得到镍钴铝前驱体材料，其中，氢氧化铝占镍钴铝前驱体材料总质量的5％。将镍钴铝前驱体材料与LiOH的摩尔比为1:1.08的比例研磨混合，在氧气气氛中以5℃/min升温速率升温至900℃煅烧15h，即得高镍正极材料，该 高镍正极材料的化学式为LiNi 0.824Co 0.145Al 0.031O 2。
实施例3
将10g Ni 0.7Co 0.3(OH) 2分散于500mL去离子水中，用氨水调节pH至9.5，得镍钴铝氢氧化物分散液。配制浓度为4mol/L硫酸铝水溶液，接着加入草酸钠混匀，草酸钠与硫酸铝的摩尔比为5：1，得硫酸铝和草酸铵的混合溶液，在将该混合溶液在加入之前进行搅拌使其不会形成沉淀，搅拌的转速为10～1000r/min。将“硫酸铝和草酸铵的混合溶液”以5mL/min的速率加入到镍钴铝氢氧化物分散液中，期间控制氨水的流速为1～20mL/min以及氨水的浓度为0.3～3mol/L从而控制整个反应体系的pH为9.5。进料完成后，以200～800r/min的转速持续搅拌5h，过滤干燥得到前驱体材料，其中，氢氧化铝占镍钴铝前驱体材料总质量的10％。按照镍钴铝前驱体材料与LiOH的摩尔比为1:1.1的比例研磨混合，在氧气气氛中以5℃/min升温速率升温至800℃煅烧18h，即得高镍正极材料，该高镍正极材料的化学式为LiNi 0.659Co 0.283Al 0.058O 2。
实施例4
将20g Ni 0.95Co 0.05(OH) 2分散于200mL去离子水中，用氨水调节pH至8，得镍钴铝氢氧化物分散液。配制浓度为1mol/L硝酸铝水溶液，接着加入2,2'-联吡啶混匀，2,2'-联吡啶与硝酸铝的摩尔比为1：1，得硝酸铝和2,2'-联吡啶的混合溶液，在将该混合溶液在加入之前进行搅拌使其不会形成沉淀，搅拌的转速为10～1000r/min。将“硝酸铝和2,2'-联吡啶的混合溶液”以10mL/min的速率加入到镍钴铝氢氧化物分散液中，期间控制氨水的流速为1～20mL/min以及氨水的浓度为0.3～3mol/L从而控制整个反应体系的pH为8。进料完成后，以200～800r/min的转速持续搅拌10h，过滤干燥得到前驱体材料，其中，氢氧化铝占前驱体材料总质量的3％。按照前驱体材料与LiOH的摩尔比为1:1.05的比例研磨混合，在氧气气氛中以5℃/min升温速率升温至700℃煅烧15h，即得高镍正极材料，该高镍正极材料的化学式为LiN 0.936Co 0.049Al 0.015O 2。
实施例5
将100g Ni 0.85Co 0.15(OH) 2分散于2000mL去离子水中，用氨水调节pH至9.0，得镍钴铝氢氧化物分散液。配制浓度为5mol/L氯化铝水溶液，加入草酸铵混匀，草酸铵与氯化铝的摩尔比为2：1，得草酸铵与氯化铝的混合溶液，在将该混合溶液在加入之前进行搅拌使其不会形成沉淀，搅拌的转速为10～1000r/min。将“草酸铵与氯化铝的混合溶液”以20mL/min的速率加入到镍钴铝氢氧化物分散液中，期间控制氨水的流速为1～20mL/min以及氨水的浓度为0.3～3mol/L从而控制整个反应体系的pH为9.0。进料完成后，以200～800r/min的转速持续搅拌10h，过滤干燥得到前驱体材料，其中，氢氧化 铝占前驱体材料总质量的5％。按照前驱体材料与LiOH的摩尔比为1:1.08的比例研磨混合，在氧气气氛中以5℃/min升温速率升温至900℃煅烧12h，即得高镍正极材料，该高镍正极材料的化学式为LiNi 0.816Co 0.144Al 0.04O 2。
实施例1～5中得到的高镍正极材料均为核壳结构。其中，核为由一次颗粒团聚而成的微球，在一次颗粒内，从外到内，铝元素的含量依次减少、呈梯度分布；壳为化学式为LiAlO 2包覆层。
实施例6
对将5g Ni 0.85Co 0.15(OH) 2分散于100mL去离子水中，用氨水调节pH至8.5，得镍钴铝氢氧化物分散液。配制浓度为2mol/L硫酸锰水溶液，加入乙二胺混匀，乙二胺与硫酸锰的摩尔比为3：1，得硫酸锰和乙二胺的混合溶液，在将该混合溶液在加入之前进行搅拌使其不会形成沉淀，搅拌的转速为10～1000r/min。将“硫酸锰和乙二胺的混合溶液”以2mLmin的速率加入到镍钴氢氧化物分散液中，期间控制氨水的流速为1～20mL/min以及氨水的浓度为0.3～3mol/L从而控制整个反应体系的pH为9。进料完成后，以200～800r/min的转速持续搅拌6h，过滤干燥得到镍钴锰前驱体材料，其中，氢氧化铝占镍钴铝前驱体材料总质量的5％。将镍钴锰前驱体材料与LiOH的摩尔比为1:1.08的比例研磨混合，在氧气气氛中以5℃/min升温速率升温至900℃煅烧15h，即得高镍正极材料，该高镍正极材料的化学式为LiNi 0.824Co 0.145Mn 0.031O 2。
本实施例的高镍正极材料为核壳结构。其中，核为由一次颗粒团聚而成的微球，在一次颗粒内，从外到内，锰元素的含量依次减少，壳为化学式为LiMn 2O 4的包覆层。
对比例1
将5g Ni 0.65Co 0.35(OH) 2分散于50mL去离子水中，得Ni 0.65Co 0.35(OH) 2分散液。配制浓度为2mol/L硫酸铝水溶液。将该硫酸铝水溶液以1mL/min的速率加入Ni 0.65Co 0.35(OH) 2分散液中。进料完成后，持续搅拌4h，过滤干燥得到前驱体材料，其中，氢氧化铝占前驱体总质量的7％。按照前驱体与锂盐的摩尔比为1:1.1的比例，将前驱体与LiOH研磨混合，在氧气气氛中800℃煅烧12h，得高镍正极材料。该高镍正极材料，没有形成核壳结构，且一次颗粒的内部未形成铝元素的梯度掺杂。
对比例2
将实施例1中pH值均设置为12，其余参数与实施例1相同。本对比例的高镍正极材料在一次颗粒内没有形成铝元素的梯度掺杂，在一次颗粒团聚而成的微球的表面没有形成包覆层。
本发明中发明人通过多次实验发现，若pH值不在8～10之间，无法在材料的表面均 匀的包覆一层偏铝酸锂层。pH过低则无法形成完整的包覆层，pH过高则包覆的不均匀，对最终得到的高镍正极材料的电化学性能会产生显著的影响。
对比例3
在实施例1基础上将络合剂替换为四齿配体EDTA，其余参数同实施例1。此对比例使用EDTA在该pH下未得到表面包覆层。没有形成核壳结构，且一次颗粒的内部未形成铝元素的梯度掺杂。
对比例4
在实施例1基础上将络合剂替换为单齿配体硫氰酸钠，其余参数同实施例1。该对比例的高镍正极材料的表面未形成包覆层。
效果实施例1
实施例1～6中的高镍正极材料的成分及结构表征。
1、对实施例1～5中镍钴铝前驱体材料和实施例6中的镍钴锰前驱体材料进行SEM检测。可得实施例1～5中镍钴铝前驱体材料的表面为均匀且完整的Al(OH) 3层，实施例6中的镍钴锰前驱体材料的表面为均匀且完整Mn(OH) 2层。例如实施例1的镍钴铝前驱体材料的SEM图如图1所示。而对比例2中的镍钴铝前驱体材料的SEM图如图2所示，其表面没有形成Al(OH) 3层，进而经过烧结之后也不会形成偏铝酸锂层。而对比例3中的镍钴铝前驱体材料的SEM图如图3所示，其表面没有形成Al(OH) 3层。而对比例4中的镍钴铝前驱体材料的SEM图如图4所示，其表面没有形成Al(OH) 3层。
2、对实施例1～6的高镍正极材料进行X射线衍射测试。如图5所示，为实施例1的高镍正极材料的X射线衍射测试。从图5中可看出，高镍正极材料的核的空间群为R-3m空间群，对应的是PDF卡片为09-0063，且峰003与峰104的比值大于1.4，壳的空间群为P4212，对应的PDF卡片为38-1464，可知，高镍正极材料的晶体结构未变。实施例2～4的高镍正极材料的核的空间群也为R-3m空间群，壳的空间群也为P4212，且峰003与峰104的比值大于1.4，高镍正极材料的晶体结构未变。
实施例6的高镍正极材料的核的空间群为R-3m，且峰003与峰104的比值大于1.4，壳的空间群为Fd-3m空间群，高镍正极材料的晶体结构未变。
3、对实施例1～6的高镍正极材料进行ICP测试，其测试结果如下表1所示，由表1可知，例如，ICP测试结果与本发明实施例1中的高镍正极材料LiNi 0.862Co 0.096Al 0.042O 2的组成相吻合。其中，ICP型号为ICP-AES，Agilent 725。
表1
Figure PCTCN2020073424-appb-000001
Figure PCTCN2020073424-appb-000002
同理，对比例1～4的高镍正极材料的化学式与ICP测试结果均相吻合。
4、实施例1～6中一次颗粒的形状为球形或椭球形，以球形为例，如图6所示，实心球体1和空心球体2均是与一次颗粒3同球心的球形，实心球体1的半径为R1，空心球体2的球面为一次颗粒3的球面，空心球体2的球壳的厚度为R2，一次颗粒3的半径为R。
对实施例1～6的高镍正极材料进行EDS能谱测试，得各实施例一次颗粒中各元素的分布图。对实施例1～6的高镍正极材料进行SEM测试，测得一次颗粒的粒径。测试结果如下表2所示，其中实施例1的高镍正极材料的切片EDS线扫图如图7a所示，图7a中的箭头为一次颗粒的线扫路径，一次颗粒内铝元素的分布如图7b所示。从图中可得出，实施例1的高镍正极材料中所有空心球体中铝元素的总摩尔量与高镍正极材料内所有元素的摩尔量的比为1.25％；实施例1的高镍正极材料中所有实心球体中铝元素的总摩尔量与高镍正极材料内所有元素的总摩尔量的比为0.5％；在一次颗粒内，铝元素从外到内逐渐减少，呈梯度分布。实心球体与空心球体中铝元素的摩尔比为0.4。
5、对实施例1～6的高镍正极材料的表面进行扫描电镜和透射电镜的测试分析。各实施例中高镍正极材料的壳的厚度如下表2所示。其中实施例1～6的高镍正极材料的表面为一均匀且完整的包覆层。例如，图8为实施例1的高镍正极材料表面的扫描电镜和透射电镜图，图8a为实施例1的高镍正极材料表面的扫描电镜图，图8b为实施例1高镍正极材料表面的透射电镜图，从图中可得出高镍正极材料表面有均匀的偏铝酸锂包覆层，图中观察到的偏铝酸锂包覆层的厚度为3nm，是均匀完整的包覆层，包覆层的晶格间距为0.217nm与偏铝酸锂的(211)晶面相对应。
对实施例1～6中高镍正极材料的表面进行X射线光电子能谱分析测试，测得各实施例中高镍正极材料的壳的质量与高镍正极材料的总质量比如下表2所示。
对实施例1～6的高镍正极材料的粒径通过激光粒度仪测试，各实施例的高镍正极材料的粒径的测试结果如下表2所示。
表2
Figure PCTCN2020073424-appb-000003
注：表2中，实心球体与高镍正极材料中铝或锰元素的摩尔比：指的是高镍正极材料中，所有实心球体中铝元素或锰元素的总摩尔量与高镍正极材料中所有元素的总摩尔量的比。
空心球体与高镍正极材料中铝或锰元素的摩尔比：指的是高镍正极材料中，所有空心球体中铝元素或锰元素的总摩尔量与高镍正极材料中所有元素的总摩尔量的比。
效果实施例2
电化学性能的测试条件：CR2016钮扣电池的组装及测试：将上述实施例1～6和对比例1～4得到的高镍正极材料、炭黑、PVDF(聚偏氟乙烯)按照8:1:1的质量比制成浆料并涂覆在铝箔上，用裁片机将烘干的负载浆料的铝箔裁成直径约为1.2cm的小圆片用作正极，以金属锂片作为负极、Celgard2400为隔膜、1M的混合有机溶液为电解液(其中，溶剂是体积比为3:7的碳酸乙烯酯和乙烯碳酸二甲酯的混合溶液，溶质为LiPF 6)，在氩气手套箱内组装成CR2016纽扣电池。将得到的电池在2.7～4.3V，测试温度在25℃条件下的进行电化学性能中的倍率性能和循环性能的测试，测试结果如下表3所示。
表3
Figure PCTCN2020073424-appb-000004
Figure PCTCN2020073424-appb-000005
图9为实施例1中的高镍正极材料的倍率和循环性能测试结果，图9a为倍率性能的测试结果，图9b为循环性能的测试结果。从图9a中可得出0.2C时，电池的可逆容量高达201mAh/g，20C时可逆容量为120mAh/g。图9b中，1C下循环100圈，可逆容量保持率高达95％，可逆容量为176mAh/g。图10为实施例1和对比例1高镍正极材料的充放电曲线和首圈充放电曲线的对比图，黑色圈内为H2-H3相变特征平台，实施例1中H2-H3相变平台变弱，说明相变减少，高镍正极材料的结构更加稳定，循环稳定性佳。
虽然以上描述了本发明的具体实施方式，但是本领域的技术人员应当理解，这些仅是举例说明，在不背离本发明的原理和实质的前提下，可以对这些实施方式做出多种变更或修改。因此，本发明的保护范围由所附权利要求书限定。

Claims (15)

  1. 一种高镍正极材料，其特征在于，所述高镍正极材料的化学式为LiNi xCo yM 1-x-yO 2，式中，0.6<x≤0.9955，0≤y≤0.3955，0.0045<1-x-y<0.06；所述高镍正极材料为核壳结构；
    其中，所述核为梯度掺杂M元素的一次颗粒团聚而成；
    所述M元素包括Al元素和/或Mn元素；
    每一所述一次颗粒内含有实心球体和空心球体，所述实心球体的球心或所述空心球体的球心为所述一次颗粒的球心；所述实心球体的半径为所述一次颗粒半径的0～1/5但不为0；所述空心球体的外球面为一次颗粒的球面，所述空心球体的球壳的厚度为所述一次颗粒半径的0～1/6但不为0；
    在每一所述一次颗粒内，从外到内，所述M元素的含量依次减少；所述高镍正极材料中所有所述的实心球体中M元素的总摩尔量与所述高镍正极材料内所有元素的总摩尔量的比为0.075％～0.75％；所述实心球体中M元素的摩尔量与所述空心球体中M元素的摩尔量的比为1/3～1/2；
    其中，所述高镍正极材料的壳为LiAlO 2和/或LiMn 2O 4；所述高镍正极材料的壳的质量占所述高镍正极材料总质量的0.2％～5％。
  2. 如权利要求1所述的高镍正极材料，其特征在于，所述LiNi xCo yM 1-x-yO 2中，所述x的值为0.6<x≤0.95；
    或，所述LiNi xCo yM 1-x-yO 2中，所述y的值为0.04～0.3；
    或，所述LiNi xCo yM 1-x-yO 2中，所述1-x-y的值为0.015～0.06；
    和/或，所述高镍正极材料的形态包括棒状、片状或球形；
    和/或，所述一次颗粒的粒径为200～900nm；
    和/或，所述实心球体的半径为所述一次颗粒半径的1/20～1/5；
    和/或，所述空心球体的球壳的厚度为所述一次颗粒半径的1/20～1/6；
    和/或，所述高镍正极材料中所有所述实心球体中M元素的总摩尔量与所述高镍正极材料内所有元素的总摩尔量的比为0.15％～0.6％，较佳地为0.15％、0.375％、0.53或0.6％；
    和/或，每一所述一次颗粒内，所述实心球体中M元素的摩尔量与所述空心球体中M元素的摩尔量的比为0.35～0.5，较佳地为0.353、0.4、0.407、0.455或0.5；
    和/或，所述高镍正极材料中所有所述空心球体中M元素的总摩尔量与所述高镍正极材料内所有元素的总摩尔量的比为0.15％～2％，较佳地为0.425％、0.825％、1.05％、1.25％或1.475％；
    和/或，所述高镍正极材料的壳的质量占所述高镍正极材料总质量的比为0.2％～3％；
    和/或，所述高镍正极材料的壳的厚度为1～10nm。
  3. 如权利要求1或2中至少一项所述的高镍正极材料，其特征在于，所述LiNi xCo yM 1- x-yO 2中，所述x的值为0.659、0.816、0.824、0.962或0.936；
    或，所述LiNi xCo yM 1-x-yO 2中，所述y的值为0.049、0.096、0.144、0.145或0.283；
    或，所述LiNi xCo yM 1-x-yO 2中，所述1-x-y的值为0.015、0.031、0.04、0.042或0.058；
    和/或，所述高镍正极材料的形态为球形。
  4. 如权利要求1～3中至少一项所述的高镍正极材料，其特征在于，所述LiNi xCo yM 1- x-yO 2中，所述x的值为0.85～0.94；
    或，所述LiNi xCo yM 1-x-yO 2中，所述y的值为0.04～0.1；
    或，所述LiNi xCo yM 1-x-yO 2中，所述1-x-y的值为0.015～0.042。
  5. 如权利要求1～4中至少一项所述的高镍正极材料，其特征在于，所述高镍正极材料中所有所述空心球体中M元素的总摩尔量与所述高镍正极材料内所有元素总摩尔量的比为0.4％～1.5％。
  6. 如权利要求1～5中至少一项所述的高镍正极材料，其特征在于，当所述高镍正极材料的形态为球形时，所述高镍正极材料的粒径为6～20μm。
  7. 一种镍钴前驱体材料的制备方法，其特征在于，其包括以下步骤：将“M盐和络合剂的混合溶液”加入到Ni nCo z(OH) 2分散液中混合反应，即得；
    所述镍钴前驱体材料的化学式为Ni nCo zM 1-n-z(OH) 2，式中，0.6<n≤0.9955，0≤z≤0.3955，0.0045<1-n-z<0.06；
    其中，所述M盐为金属盐，所述金属盐的种类包括Al盐和/或Mn盐；所述络合剂为双齿配体；所述混合反应过程中的pH值为8～10。
  8. 如权利要求7所述的镍钴前驱体材料的制备方法，其特征在于，所述“M盐和络合剂的混合溶液”的制备方法包括以下步骤：将M盐溶液与所述的络合剂混合即可；
    和/或，所述“M盐和络合剂的混合溶液”中，所述M盐和所述络合剂的摩尔比为(1～5)：1；
    和/或，所述双齿配体的种类包括含草酸根的化合物、乙二胺和2,2'-联吡啶中的一种或多种；
    当所述的M盐为Al盐时，所述Al盐的种类包括硫酸铝、氯化铝和硝酸铝中的一种或多种；
    当所述的M盐为Mn盐时，所述Mn盐的种类包括硫酸锰、盐酸锰、硝酸锰和醋酸锰中的一种或多种；
    和/或，所述的混合反应之前还包括对所述“M盐和络合剂的混合溶液”进行搅拌的操作；
    和/或，所述“M盐和络合剂的混合溶液”加入到所述Ni nCo z(OH) 2分散液中的速率为1～20mL/min；
    和/或，所述“M盐和络合剂的混合溶液”加入到所述Ni nCo z(OH) 2分散液中，加入的方式为滴加；
    和/或，所述Ni nCo z(OH) 2中，n的值为0.7～0.95；
    或，所述Ni nCo z(OH) 2中，z的值为0.05～03；
    和/或，所述Ni nCo z(OH) 2分散液的浓度为1～20wt％；
    和/或，所述Ni nCo z(OH) 2分散液的pH值为8～10；
    和/或，所述pH值通过pH值调节剂调节；所述pH值调节剂的种类包括碳酸钠、碳酸氢钠、氢氧化钠、氢氧化钾和氨水中的一种或多种；当所述pH值调节剂为氨水时，所述氨水的浓度为0.3～3mol/L；
    和/或，所述混合反应的操作为搅拌；
    和/或，所述混合反应的时间为2～10h。
  9. 如权利要求8所述的镍钴前驱体材料的制备方法，其特征在于，所述混合反应之前的所述搅拌的转速为10～1000r/min。
  10. 如权利要求7-9中至少一项所述的镍钴前驱体材料的制备方法，其特征在于，所述Ni nCo z(OH) 2分散液的pH值为8～9.8。
  11. 如权利要求8～10中至少一项所述的镍钴前驱体材料的制备方法，其特征在于，控制所述pH值的方式为保持在所述加入和所述混合反应的过程中通入所述pH值调节剂的流速，所述流速为1～20mL/min；
    和/或，所述M盐溶液的浓度为1～5mol/L；
    和/或，所述含草酸根的化合物的种类包括草酸铵和/或草酸钠；
    和/或，所述“M盐和络合剂的混合溶液”加入到所述Ni nCo z(OH) 2分散液中的速率为1～10mL/min；
    和/或，所述Ni nCo z(OH) 2分散液的pH值为9或9.5；
    和/或，所述混合反应中所述搅拌的转速为200～800r/min；
    当所述M盐为Al盐时，所述的镍钴前驱体材料为镍钴铝前驱体材料；所述镍钴铝前驱体材料中的氢氧化铝的质量占所述镍钴铝前驱体材料总质量的0.2％～10％；
    当所述M盐为Mn盐时，所述的镍钴前驱体材料为镍钴锰前驱体材料；所述镍钴锰 前驱体材料中的氢氧化锰的质量占所述镍钴锰前驱体材料总质量的0.2％～10％。
  12. 一种镍钴前驱体材料，其特征在于，其采用如权利要求7～11中至少一项所述的镍钴前驱体材料的制备方法制得。
  13. 一种如权利要求1～6中至少一项所述的高镍正极材料的制备方法，其特征在于，其包括以下步骤：将如权利要求12所述的镍钴前驱体材料与锂盐的混合物，烧结即可。
  14. 如权利要求13所述的高镍正极材料的制备方法，其特征在于，所述镍钴前驱体材料与所述锂盐的摩尔比为1：(1～1.2)；
    和/或，所述锂盐为氢氧化锂；
    和/或，所述烧结的温度为700～900℃；
    和/或，所述烧结过程中的升温速率为4～6℃/min；
    和/或，所述烧结的时间为10～18h。
  15. 一种锂离子电池，其特征在于，所述锂离子电池的正极材料中的前驱体为如权利要求12所述的镍钴前驱体材料；或者，所述锂离子电池的正极材料为如权利要求1～6中至少一项所述的高镍正极材料。
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CN114122552A (zh) * 2021-11-23 2022-03-01 合肥综合性国家科学中心能源研究院(安徽省能源实验室) 一种回收退役锂离子电池制备LiAlO2包覆单晶正极材料的方法
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CN114534542A (zh) * 2022-02-28 2022-05-27 华东理工大学 一种搅拌桨、搅拌系统、正极材料及其前驱体、制备方法
CN114534542B (zh) * 2022-02-28 2024-01-26 华东理工大学 一种搅拌桨、搅拌系统、正极材料及其前驱体、制备方法
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WO2025118695A1 (zh) * 2023-12-05 2025-06-12 宁德时代新能源科技股份有限公司 三元前驱体及其制备方法、二次电池和用电装置
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