WO2023103700A1 - 一种高镍正极材料及其制备方法、锂离子电池 - Google Patents

一种高镍正极材料及其制备方法、锂离子电池 Download PDF

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WO2023103700A1
WO2023103700A1 PCT/CN2022/130946 CN2022130946W WO2023103700A1 WO 2023103700 A1 WO2023103700 A1 WO 2023103700A1 CN 2022130946 W CN2022130946 W CN 2022130946W WO 2023103700 A1 WO2023103700 A1 WO 2023103700A1
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positive electrode
electrode material
nickel
cladding layer
lithium
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PCT/CN2022/130946
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English (en)
French (fr)
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温伟城
郑玉
杨顺毅
黄友元
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深圳市贝特瑞纳米科技有限公司
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Priority to JP2023565288A priority Critical patent/JP2024515954A/ja
Priority to EP22903123.2A priority patent/EP4280304A1/en
Publication of WO2023103700A1 publication Critical patent/WO2023103700A1/zh

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    • H—ELECTRICITY
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    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
    • H01M10/0563—Liquid materials, e.g. for Li-SOCl2 cells
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    • 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
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
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    • H01M4/362—Composites
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    • 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
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    • 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
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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    • 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
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    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M2010/4292—Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode
    • H—ELECTRICITY
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    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/002—Inorganic electrolyte
    • 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 disclosure belongs to the technical field of positive electrode materials, and in particular relates to a high-nickel positive electrode material, a preparation method thereof, and a lithium ion battery.
  • Lithium-ion batteries have high energy density, good safety performance, long cycle life and environmental friendliness and are widely used in notebook computers, mobile phones, digital products and other fields; at the same time, with the enhancement of people's awareness of environmental protection, lithium-ion batteries are gradually being used as power Batteries are used in the field of transportation, such as electric vehicles, electric buses, etc.
  • the market has also put forward higher and higher requirements for the specific capacity, energy density, power density, and service life of lithium-ion batteries, especially the specific capacity.
  • the most widely used positive electrode materials in lithium-ion batteries are LiFePO 4 with olivine structure, LiCoO 2 with layered structure and lithium nickel oxide materials with layered structure; LiFePO 4 with olivine structure has reached the capacity limit, and subsequent It is mainly used in the field of energy storage and low battery life electric vehicles; layered structure LiCoO 2 is mainly used in the field of consumer batteries; lithium nickel oxide materials are widely used in the field of electric vehicles; in lithium nickel oxide materials, nickel is the main Increasing the nickel content can effectively increase the specific capacity of such materials, so the development of high-nickel materials has become a market trend.
  • the intrinsic structure will gradually undergo irreversible structural changes with the progress of charging and discharging, and the higher the nickel content, the greater the structural changes; during the charging and discharging process of high-nickel materials, the valence of nickel will change accordingly, corresponding to lithium
  • the electrolyte will enter the interior of the material through cracks and undergo redox reactions with highly active Ni 4+ , resulting in changes in the material structure;
  • the high-nickel ternary material is delithiated , the Ni 3+ on the surface of the material will be converted into Ni 4+ with strong oxidative properties, and Ni 4+ will easily undergo redox reactions with the organic electrolyte, thereby causing the loss of positive electrode active materials
  • the present disclosure provides a high-nickel positive electrode material, the general chemical formula of the high-nickel positive electrode material is shown in formula (1):
  • the high-nickel positive electrode material is measured by powder XPS using AlK ⁇ rays. After the Ni2P 3/2 peak that appears in the range of binding energy in the range of 850eV to 870eV is divided and fitted, the peak area of Ni 2+ is set as S1 , the peak area of Ni 3+ is set as S2, the peak half width of Ni 2+ is set as ⁇ , and the peak half width of Ni 3+ is set as ⁇ , S1, S2, ⁇ and ⁇ satisfy the following relationship :
  • the positive electrode material includes secondary particles and/or primary particles, at least part of the surface of the primary particles is covered with a coating layer, and the secondary particles include a plurality of primary particles with coating layers.
  • the coating layer includes a first coating layer and a second coating layer, the first coating layer is formed on the surface of the primary particle, and the second coating layer is formed on the first coating layer A coated surface.
  • the coating layer includes a first coating layer formed on the surface of the primary particle.
  • the coating layer includes a second coating layer formed on the surface of the primary particle.
  • the coating layer includes a first coating layer and a second coating layer, and the first coating layer includes elements with a valence greater than or equal to positive 3 in the high-nickel positive electrode material.
  • the cladding layer includes a first cladding layer and a second cladding layer
  • the first cladding layer includes Al, Ti, P, Si, Nb, Y, W, Cr, Zr and La. at least one of .
  • the cladding layer includes a first cladding layer and a second cladding layer
  • the first cladding layer includes Al, Ti, P, Si, Nb, Y, W, Cr, Zr and La at least one of the compounds.
  • the cladding layer includes a first cladding layer and a second cladding layer
  • the first cladding layer includes Al, Ti, P, Si, Nb, Y, W, Cr, Zr and La
  • a compound of at least one of the compounds, the compound is at least one of oxides, hydroxides and salts.
  • the cladding layer includes a first cladding layer and a second cladding layer
  • the second cladding layer includes a compound containing at least one of B, La and Al.
  • the cladding layer includes a first cladding layer and a second cladding layer
  • the second cladding layer includes a compound containing at least one of B, La and Al, and the compound is an oxide , at least one of acid and lithium-containing salt.
  • the cladding layer includes a first cladding layer and a second cladding layer, the second cladding layer including a boron-containing compound.
  • the cladding layer includes a first cladding layer and a second cladding layer
  • the second cladding layer includes a boron-containing compound
  • the boron-containing compound includes a boron-containing oxide, a boron-containing acid, and a boron-containing compound. At least one of salts of boron and lithium.
  • the cladding layer includes a first cladding layer and a second cladding layer
  • the second cladding layer includes a boron-containing compound
  • the boron-containing compound includes B 2 O 3 , H 3 BO 3 , Li 2 At least one of OB 2 O 3 , Li 3 BO 3 , Li 2 B 4 O 7 , Li 2 B 2 O 7 and Li 2 B 8 O 13 .
  • said M1 includes Mn and/or Al.
  • the M2 includes elements with a valence greater than or equal to positive 4 in the high-nickel positive electrode material.
  • the M3 includes elements with a valence equal to positive 2 in the high-nickel positive electrode material.
  • both M2 and M3 include at least one of Zr, Ti, Nb, Ce, Hf, W, Mo, Ta, Ge, Sn, Sr, Mg and Ba, and M2 and M3 are different.
  • the M4 includes elements with a valence greater than or equal to positive trivalence in the high-nickel positive electrode material.
  • the M4 includes at least one of Al, Ti, P, Si, Nb, Y, W, Cr, Zr and La.
  • the M5 includes at least one of B, La and A.
  • said M5 includes B.
  • the high-nickel positive electrode material is determined by powder XPS using AlK ⁇ rays: after splitting and fitting the Ni2P 3/2 peaks that appear in the range of binding energy in the range of 850eV to 870eV, Ni 2+ /Ni 3+ The area ratio is greater than 1.
  • the high-nickel positive electrode material is measured by powder XPS using AlK ⁇ rays: when the O1S peak that appears in the range of 526eV to 540eV is divided and fitted, the area of O1S lattice oxygen /O1S impurity oxygen The ratio is greater than 1/2.
  • the mass content of LiOH in the high-nickel positive electrode material is less than 0.3wt%.
  • the mass content of Li 2 CO 3 in the high-nickel positive electrode material is less than 0.3 wt%.
  • the crystal structure of the nickel-rich positive electrode material belongs to hexagonal crystal structure or monoclinic crystal structure.
  • the morphology of the crystal particles of the high-nickel positive electrode material includes at least one of approximately spherical, approximately cubic and approximately cuboid shapes.
  • the pH of the high-nickel positive electrode material is: 10 ⁇ pH ⁇ 12.
  • the pH of the nickel-rich cathode material is: 10.5 ⁇ pH ⁇ 11.7.
  • the powder conductivity of the high-nickel cathode material is greater than 0.02 S/cm.
  • the specific surface area of the high-nickel positive electrode material is 0.3m 2 /g ⁇ 0.8m 2 /g.
  • the average particle diameter of the high-nickel positive electrode material is 2.5 ⁇ m ⁇ 4.5 ⁇ m.
  • the disclosure also discloses a method for preparing a high-nickel positive electrode material, which includes the following steps:
  • the matrix material is obtained by mixing the metal composite hydroxide precursor, the lithium-containing compound and the dopant and performing a heat treatment;
  • the dopant includes a compound containing M2 elements and a compound containing M3 elements, the compound containing M2 elements is at least one of oxides, hydroxides, and lithium metal oxides containing only M2, and the The valence of M2 in the compound is greater than or equal to positive 4, the compound containing M3 element is at least one of oxides and hydroxides containing only M3, and the valence of M3 in the compound is positive 2 price;
  • the base material is coated to obtain a high-nickel positive electrode material.
  • the mass ratio of the metal composite hydroxide precursor, the lithium-containing compound and the dopant is 1:(0.46-0.49):(0.001-0.005).
  • the mass ratio of the metal composite hydroxide precursor, the lithium-containing compound and the dopant is 1:(0.46-0.48):(0.001-0.003).
  • the atomic ratio of the total amount of metal Me in the metal composite hydroxide precursor to Li in the lithium-containing compound is 1.0 ⁇ Li/Me ⁇ 1.2.
  • the lithium-containing compound includes a lithium-containing salt, a lithium-containing hydroxide.
  • the lithium-containing compound includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate and lithium acetate.
  • the M2 element and the M3 element are at least one selected from Zr, Ti, Nb, Ce, Hf, W, Mo, Ta, Ge, Sn, Sr, Mg and Ba, and M2 and M3 Are not the same.
  • the molar ratio n M2 : n M3 of M2 and M3 is greater than or equal to 2:1.
  • the average particle size of the dopant is 10nm-50nm.
  • the temperature of the primary heat treatment is 680°C-900°C.
  • the time for the primary heat treatment is 5h-20h.
  • the heating rate of the primary heat treatment is 50°C/h-550°C/h.
  • the oxygen content of the matrix material is greater than or equal to 85%.
  • the method includes the step of mixing the matrix material with the first coating agent and then performing a second heat treatment to obtain a result of the first coating.
  • the method includes: the mass ratio of the matrix material to the first coating agent is 1000:(0.5-3).
  • the method includes: the first coating agent includes a metal element or a non-metal element with a valence greater than or equal to positive 3.
  • the method includes: the first coating agent includes at least one of oxides, salts or hydroxides of metal elements or non-metal elements with a valence greater than or equal to positive 3.
  • the method includes: the first coating agent includes a metal element or a non-metal element having a valence greater than or equal to positive 3, and the metal element or non-metal element includes Al, Ti, P, Si, Nb, At least one of Y, W, Cr, Zr or La.
  • the method includes: the first coating agent includes at least one of lithium aluminate, lithium titanate, lithium lanthanum titanate, yttrium oxide, aluminum oxide and titanium oxide.
  • the method includes: the average particle diameter of the first coating agent is 10nm-50nm.
  • the method includes: the temperature of the secondary heat treatment is 600°C-800°C.
  • the method includes: the time of the second heat treatment is 1 h to 20 h.
  • the method includes: the heating rate of the secondary heat treatment is 50°C/h-550°C/h.
  • the method includes: after the second heat treatment, washing under constant temperature conditions, and drying under vacuum conditions after washing, where the temperature under constant temperature conditions is 10°C to 25°C.
  • the method includes: after the secondary heat treatment, washing under constant temperature conditions, and drying under vacuum conditions after washing, the temperature of the drying treatment is 100°C-200°C.
  • the method includes: the oxygen content in the primary coating result is greater than or equal to 85%.
  • the method further includes the step of performing three heat treatments after mixing the primary coating resultant with the second coating agent.
  • the method includes: the second coating agent includes a compound containing at least one of B, La and Al.
  • the method includes: the second coating agent includes a compound containing at least one of B, La and Al, and the compound is an oxide, an acid, or a lithium-containing salt.
  • the method includes: the second capping agent includes a boron-containing compound.
  • the method includes: the second coating agent includes a boron-containing compound, the boron-containing compound includes a boron-containing oxide, a boron-containing acid, or a boron- and lithium-containing salt.
  • the method includes: the second coating agent includes a boron-containing compound, and the boron-containing compound includes B 2 O 3 , H 3 BO 3 , Li 2 OB 2 O 3 , Li 3 BO 3 , Li At least one of 2 B 4 O 7 , Li 2 B 2 O 7 and Li 2 B 8 O 13 .
  • the method includes: the mass ratio of the first coating product to the second coating agent is 1: (0.0005-0.005).
  • the method includes: the temperature of the three heat treatments is 200°C-600°C.
  • the method includes: the time of the three heat treatments is 1 h to 20 h.
  • the method includes: the heating rate of the three heat treatments is 50°C/h-550°C/h.
  • the metal composite hydroxide precursor is obtained by mixing a metal salt solution, a complexing agent, and a pH regulator.
  • the method includes: the mass ratio of the metal salt solution to the complexing agent and the pH regulator is 1:(0.01-0.10):(0.1-0.8).
  • the method includes: the metal salt solution includes at least one of a nickel salt solution, a cobalt salt solution, a manganese salt solution, and an aluminum salt solution.
  • the method includes: the complexing agent includes ammonia, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracil diacetic acid and at least one of glycine.
  • the complexing agent includes ammonia, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracil diacetic acid and at least one of glycine.
  • the method includes: the pH regulator includes at least one of sodium hydroxide and potassium hydroxide.
  • the method includes: the pH of the mixing treatment is 9-13.
  • the method includes: the temperature of the mixing treatment is 10°C-80°C.
  • the method includes: the time of the mixing treatment is 10h to 200h.
  • the method includes: the mixing treatment is performed under a stirring state, and the stirring rate is 800rpm-1200rpm.
  • the method includes: after the mixing treatment, the steps of solid-liquid separation, washing and drying are also included.
  • the method includes: the average particle diameter of the metal composite hydroxide precursor is 3 ⁇ m ⁇ 10 ⁇ m.
  • the present disclosure also discloses a lithium-ion battery, which includes the above-mentioned high-nickel positive electrode material or the high-nickel positive-electrode material prepared by the above-mentioned method.
  • Fig. 1 is the preparation flowchart of the high-nickel positive electrode material of some embodiments of the present disclosure
  • Example 3 is a peak splitting and curve fitting diagram of the Ni2P 3/2 peak Ni2P 3/2 of the Ni bonding part at the position of the binding energy of the high-nickel positive electrode material in Example 1 of the present disclosure;
  • Example 4 is a peak splitting and curve fitting diagram of the Ni2P 3/2 peak Ni2P 3/2 of the Ni bonding part at the position where the binding energy is 850eV-870eV of the high-nickel positive electrode material of Example 8 of the present disclosure;
  • Fig. 5 is a peak splitting and curve fitting diagram of the Ni2P 3/2 peak Ni2P3/2 of the Ni bonding part at the position where the binding energy of the high-nickel positive electrode material of Comparative Example 1 is 850eV to 870eV;
  • Fig. 6 is a peak splitting and curve fitting diagram of the Ni2P 3/2 peak Ni2P3/2 of the Ni bonding part at the position where the binding energy of the high-nickel positive electrode material of Comparative Example 2 is 850eV to 870eV;
  • Example 7 is a peak splitting and curve fitting diagram of the peak O1S of the O-bonding part of the high-nickel positive electrode material in Example 1 of the present disclosure at the position where the binding energy is 526eV-540eV;
  • Example 8 is a peak splitting and curve fitting diagram of the peak O1S of the O-bonding part at the position of the binding energy of 526eV-540eV in the high-nickel positive electrode material of Example 8 of the present disclosure;
  • Fig. 9 is a peak splitting and curve fitting diagram of the peak O1S of the O-bonded part of the high-nickel positive electrode material of Comparative Example 1 at the position where the binding energy is 526eV-540eV;
  • Fig. 10 is a peak splitting and curve fitting diagram of the peak O1S of the O-bonded part of the high-nickel positive electrode material of Comparative Example 2 at the position of the binding energy of 526eV to 540eV;
  • Example 11 is a capacity differential curve of the high-nickel positive electrode material in Example 1 of the present disclosure.
  • Example 12 is a capacity differential curve of the high-nickel positive electrode material of Example 8 of the present disclosure.
  • Fig. 13 is the capacity differential curve of the high-nickel positive electrode material of comparative example 1;
  • Fig. 14 is the capacity differential curve of the high-nickel positive electrode material of comparative example 2.
  • Fig. 15 is an SEM image of argon ion section analysis of the high-nickel positive electrode material in Example 1 of the present disclosure after 300 cycles;
  • Fig. 16 is an SEM image of the argon ion section analysis of the high-nickel positive electrode material of Example 8 of the present disclosure after 300 cycles;
  • Figure 17 is the SEM image of the argon ion section analysis of the high-nickel positive electrode material of Comparative Example 1 cycled for 300 cycles;
  • Figure 18 is the SEM image of the argon ion section analysis of the high-nickel positive electrode material of Comparative Example 2 after 300 cycles;
  • Fig. 19 is an SEM image of the argon ion section analysis of the high-nickel positive electrode material of Example 25 of the present disclosure after 300 cycles;
  • Fig. 20 is an SEM image of the argon ion section analysis of the high-nickel positive electrode material of Example 26 of the present disclosure after 300 cycles;
  • Fig. 21 is an SEM image of the argon ion section analysis of the high-nickel positive electrode material of Comparative Example 6 of the present disclosure after 300 cycles;
  • FIG. 22 is a schematic structural view of a partial section of a high-nickel positive electrode material provided by some embodiments of the present disclosure.
  • FIG. 23 is a schematic structural view of a partial section of a high-nickel positive electrode material provided by some embodiments of the present disclosure.
  • Fig. 24 is a schematic structural view of a partial section of a high-nickel positive electrode material provided by some embodiments of the present disclosure.
  • Fig. 25 is a schematic structural view of a partial section of a high-nickel positive electrode material provided by some embodiments of the present disclosure.
  • 26 is a schematic structural view of a partial section of a high-nickel positive electrode material provided by some embodiments of the present disclosure.
  • Figs. 22-26 are only illustrative cutaway views of a part of the nickel-rich positive electrode material (a certain random field of view).
  • first and second are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as “first” and “second” may explicitly or implicitly include one or more of these features.
  • matrix refers to a lithium-based composite oxide synthesized through a high-temperature solid-state reaction after a precursor is mixed with a lithium salt, and includes lithium and metal elements.
  • primary particle refers to particles that exist alone without forming aggregates.
  • secondary particle refers to a particle in which the above-mentioned primary particles are aggregated.
  • NCM ternary cathode material can be understood as a solid solution of LiCoO 2 , LiNi 0.5 Mn 0.5 O 2 and LiNiO 2 , which corresponds to the general formula Li 1+a [N z (Ni 1/2 Mn 1/2 ) y CO x ] 1 -a O 2 , where Z represents the Ni 3+ ratio; for example, LiNi 0.6 Co 0.2 Mn 0.2 O 2 can be understood as 0.2LiCoO 2 +0.4LiNi 0.5 Mn 0.5 O 2 +0.4LiNiO 2 , so the Ni 3+ ratio is 0.4, Other high-nickel materials such as LiNi 0.885 Co 0.09 Mn 0.025 O 2 have a Ni 3+ ratio of 0.86, and LiNi 0.8 Co 0.15 Al 0.05 O 2 has a Ni 3+ ratio of 0.8.
  • the oxygen content required in the synthesis process is also high, because only in this way can the Ni 2+ in the precursor be oxidized to Ni 3+ , such as LiNi 0.885 Co 0.09 Mn 0.025 O 2 and LiNi 0.8 Co 0.15 Al 0.05 O 2 must be synthesized in a high-concentration oxygen atmosphere, while the Ni 3+ ratio of LiNi 0.4 Co 0.2 Mn 0.4 O 2 is 0, so it can be synthesized in an air atmosphere, and the surface of the material Alkaline impurities are rare.
  • the synthesized high-nickel material is very sensitive to moisture in the air.
  • Ni 3+ in the high-nickel material is relatively high, which leads to the proton exchange reaction between lithium in the high-nickel material and water in the air to form LiOH, while Ni Medium-low nickel materials with a low 3+ ratio are more difficult to undergo proton exchange reactions, so the production and storage of high-nickel materials must be in a low-humidity environment.
  • the battery is made of high-nickel material. After the battery is charged, the Ni 3+ in the material will be converted into Ni 4+ . The strong oxidation of Ni 4+ will cause a redox reaction with the electrolyte in direct contact.
  • high-nickel materials must contain a high proportion of Ni 3+ , and Ni 3+ in the surface layer (5nm-10nm) of high-nickel materials is in direct contact with the electrolyte or air, so how to control the Ni 3+ in the surface layer of high-nickel materials
  • the + ratio is of great significance for improving the high-temperature cycle performance of high-nickel materials, reducing material gas production, reducing basic impurities on the surface of materials, and reducing the growth of DC internal resistance.
  • the present disclosure provides a high-nickel positive electrode material and a preparation method thereof, and a lithium-ion battery.
  • the high-nickel positive electrode material of the present disclosure has a small amount of Ni 3+ and a large amount of Ni 2+ on the surface, which can avoid the high-nickel positive electrode material
  • the surface is oxidized during delithiation, which can improve the high-temperature cycle performance and structural stability of high-nickel cathode materials.
  • One embodiment of the present disclosure provides a high-nickel positive electrode material, the general chemical formula of which is shown in formula (1):
  • the high-nickel cathode material is determined by powder XPS using AlK ⁇ rays. After splitting and fitting the Ni2P 3/2 peak that appears in the range of 850eV to 870eV, the peak area of Ni 2+ is set as S1, Ni The peak area of 3+ is set as S2, the peak half-width of Ni 2+ is set as ⁇ (or expressed by a, which is different from a in the above chemical general formula), and the peak half-width of Ni 3+ is set as Defined as ⁇ (or represented by b, which is different from b in the above-mentioned general chemical formula), S1, S2, ⁇ (a) and ⁇ (b) satisfy the following relationship:
  • the high-nickel positive electrode material of the present disclosure satisfies the following relationship through XPS measurement: S1/(S1+S2)>0.5 and 0.9 ⁇ / ⁇ 1.5, indicating that the Ni 3 on the surface of the high-nickel positive electrode material of the present disclosure
  • the amount of + is small, and the amount of Ni 2+ on the surface is large, which can prevent the surface of the high-nickel cathode material from being oxidized during delithiation, and is conducive to maintaining the stability of the structure of the cathode material, thereby avoiding the positive electrode active material and electrolyte during the charging and discharging process.
  • the capacity of the cathode material is further increased, and the high-temperature cycle performance of the high-nickel cathode material is significantly improved.
  • the amount of Ni 3+ on the surface of the material is small and the amount of Ni 2+ on the surface is large, it can reduce the internal cracks of the material during charging and discharging, making the internal structure of the material stable, so that the positive electrode material of the present disclosure can be used in batteries During long-term cycling, the DC internal resistance growth of the battery is significantly suppressed.
  • the positive electrode material 100 includes: particles 120 ; a coating layer 140 ; the coating layer 140 is formed on the surface of the particles 120 .
  • the particle 120 includes a secondary particle 124 and/or a primary particle 122, at least part of the surface of the primary particle 122 is covered with a coating layer 140, and the secondary particle 124 includes a plurality of primary particles with a coating layer 140. Particle 122.
  • the positive electrode material 100 includes secondary particles 124 and/or primary particles 122, at least part of the surface of the primary particles 122 is covered with a coating layer 140, and the secondary particles 124 include a plurality of particles with a coating layer 140.
  • Primary particle 122 It can be understood that the secondary particles 124 are aggregates of a plurality of primary particles 122, and the positive electrode material 100 of the present disclosure may only include the primary particles 122, or only include the secondary particles 124, or may be composed of the primary particles 122 and the secondary particles. 124 mixture.
  • the coating layer 140 includes a first coating layer 142 and a second coating layer 144, the first coating layer 142 is formed on the surface of the primary particle 122, and the second coating layer 144 formed on the surface of the first cladding layer 142 .
  • the first coating layer 142 is formed on the surface of the primary particle 122 .
  • the second coating layer 144 is formed on the surface of the primary particle 122 .
  • the first cladding layer 142 can improve the stability of the surface structure of the material, and the second cladding layer 144 can effectively improve the processability and electrical conductivity of the material.
  • anode material 100 comprises: primary particle 122; Secondary particle 124; Coating layer 140, this coating layer comprises first coating layer 142 and second coating layer 144; A coating layer 142 is formed on the surface of the primary particle 122 , and a second coating layer 144 is formed on the surface of the first coating layer 142 ; the secondary particle includes a plurality of primary particles 122 with the coating layer 140 .
  • the positive electrode material 100 includes: secondary particles 124 including a plurality of primary particles 122 ; surfaces of the primary particles 122 are coated with a coating layer 140 .
  • positive electrode material 100 comprises: secondary particle 124, and this secondary particle 124 comprises a plurality of primary particle 122; The surface of this primary particle 122 is coated with coating layer 140; Coating layer 140 includes a first coating layer 142 and a second coating layer 144 ; the first coating layer 142 is formed on the surface of the primary particle 122 , and the second coating layer 144 is formed on the surface of the first coating layer 142 .
  • the first cladding layer 142 includes elements with a valence greater than or equal to positive 3 in the high-nickel positive electrode material 100 .
  • the first cladding layer 142 includes at least one of Al, Ti, P, Si, Nb, Y, W, Cr, Zr, and La.
  • the valence of the above elements in the high-nickel positive electrode material 100 is greater than or equal to positive trivalence, so that the amount of Ni 2+ in the surface layer of the high-nickel positive electrode material 100 remains unchanged or further increases, improving the stability of the structure of the positive electrode material 100, and also reducing For the generation of alkaline impurities on the surface of the material, it can be understood that the surface of the above-mentioned high-nickel positive electrode material 100 refers to the thickness of the surface of the primary particle 122 of 5nm-10nm.
  • the cladding layer includes a first cladding layer and a second cladding layer
  • the first cladding layer includes Al, Ti, P, Si, Nb, Y, W, Cr, Zr and at least one compound of La.
  • the cladding layer includes a first cladding layer and a second cladding layer
  • the first cladding layer includes Al, Ti, P, Si, Nb, Y, W, Cr, Zr and a compound of at least one of La, said compound being at least one of an oxide, a hydroxide or a salt.
  • the second cladding layer 144 includes at least one compound of B, La, and Al.
  • the second cladding layer 144 includes at least one compound among B, La and Al, and the compound is at least one of oxide, acid and lithium-containing salt.
  • the second cladding layer 144 includes a boron-containing compound including at least one of a boron-containing oxide, a boron-containing acid, and a boron- and lithium-containing salt.
  • boron-containing oxides include, but are not limited to, B 2 O 3 , B 2 O, and the like.
  • boron-containing acids include, but are not limited to, H 3 BO 3 .
  • boron and lithium containing salts include, but are not limited to, Li i B j O k , where 2 ⁇ i ⁇ 3, 1 ⁇ j ⁇ 8, 3 ⁇ k ⁇ 13.
  • salts containing boron and lithium include, but are not limited to, B 2 O 3 , H 3 BO 3 , Li 2 OB 2 O 3 , Li 3 BO 3 , Li 2 B 4 O 7 , Li 2 B 2 O 7 and At least one of Li 2 B 8 O 13 .
  • the second cladding layer 144 includes an aluminum-containing compound, including an aluminum-containing oxide, or a boron and lithium-containing salt.
  • aluminum-containing oxides include, but are not limited to, Al 2 O 3 .
  • boron and lithium containing salts include, but are not limited to, Li 3 BO 3 .
  • the second cladding layer 144 includes a boron-containing compound including B 2 O 3 , H 3 BO 3 , Li 2 OB 2 O 3 , Li 3 BO 3 , Li 2 B 4 O 7 , At least one of Li 2 B 2 O 7 and Li 2 B 8 O 13 .
  • the above-mentioned boron-containing compound can not only chemically react with the alkaline impurities on the surface of the high-nickel positive electrode material 100, but also avoid the decomposition of Li2CO3 in the alkaline impurities on the surface of the material or the side reaction of the alkaline impurities with the electrolyte to generate gas, Moreover, the boron-containing compound covers the surface of the high-nickel positive electrode material 100 to form a stable coating layer, which can improve the stability of the high-nickel positive electrode material 100 .
  • M1 includes Mn and/or Al. In some embodiments, M1 may be Mn, Al, or a mixture of Mn and Al.
  • M2 includes elements with a valence greater than or equal to positive 4 in the high-nickel positive electrode material.
  • M3 includes elements whose valence is equal to positive 2 in the high-nickel positive electrode material.
  • M2 and M3 each include at least one of Zr, Ti, Nb, Ce, Hf, W, Mo, Ta, Ge, Sn, Sr, Mg, and Ba, and M2 and M3 are different.
  • M4 includes elements with a valence greater than or equal to positive trivalence in the high-nickel positive electrode material.
  • M4 includes at least one of Al, Ti, P, Si, Nb, Y, W, Cr, Zr, and La.
  • M5 includes at least one of B, La, and A.
  • M5 includes B.
  • the high-nickel cathode material 100 is measured by powder XPS using AlK ⁇ rays: when the Ni2P 3/2 peak that appears in the range of 850eV to 870eV is split and fitted, and the standard deviation of the fit is ⁇ x 2 ⁇ 10%, the peak area ratio of Ni 2+ /Ni 3+ >1.
  • the peak area ratio of Ni 2+ /Ni 3+ can be 2, 3, 4 and 5, etc., indicating that the Ni 2+ in the surface layer of the high-nickel material of the present disclosure is more, which can avoid the high-nickel positive electrode material 100 surface It is oxidized during delithiation, which is beneficial to maintaining the stability of the structure of the positive electrode material 100 .
  • the high-nickel positive electrode material 100 is measured by powder XPS using AlK ⁇ rays.
  • O1S peak that appears in the range of 526eV to 540eV is divided and fitted, and the standard deviation of the fit is ⁇ x 2 ⁇ 10%, the area ratio of O1S lattice oxygen /O1S impurity oxygen >1/2.
  • Impurity oxygen refers to oxygen in compounds such as LiOH, Li 2 CO 3 and Li 2 SO 4.
  • the area of O1S lattice oxygen /O1S impurity oxygen can be 0.532, 0.525 and 0.573, 0.58, 0.59, etc., will
  • the area ratio of O1S lattice oxygen /O1S impurity oxygen is controlled in the above-mentioned range, helps to reduce the alkaline impurity (Li 2 CO 3 and LiOH etc.) on the surface of high-nickel positive electrode material 100, reduces the battery life of high-nickel positive electrode material 100 preparations Gas production.
  • the basic impurities on the surface of the high-nickel positive electrode material 100 mainly refer to Li 2 CO 3 and LiOH, and the mass content of Li 2 CO 3 in the high-nickel positive electrode material 100 is less than 0.3 wt%.
  • the mass content of Li 2 CO 3 in the high-nickel positive electrode material 100 can be 0.05wt%, 0.1wt%, 0.12wt% and 0.2wt%, etc., of course, it can also be other values within the above range, which is not limited here .
  • the mass content of Li 2 CO 3 in the high-nickel cathode material 100 is less than 0.13 wt%.
  • the mass content of LiOH in the high-nickel cathode material 100 is less than 0.3 wt%.
  • the mass content of LiOH in the high-nickel cathode material 100 can be 0.05wt%, 0.08wt%, 0.1wt% and 0.2wt%, and of course it can be other values within the above range, which is not limited here.
  • the mass content of LiOH in the high-nickel cathode material 100 is less than 0.1 wt%.
  • Controlling the mass content of Li 2 CO 3 and LiOH in the high-nickel positive electrode material 100 within the above-mentioned range is beneficial to improve the processing performance of the high-nickel positive electrode material 100 and reduce the gas production of batteries prepared from the high-nickel positive electrode material 100 .
  • the crystal structure of the nickel-rich cathode material 100 belongs to the hexagonal crystal structure or the monoclinic crystal structure.
  • the crystal structure of the hexagonal crystal form belongs to the group consisting of P3, P31, P32, R3, P-3, R-3, P312, P321, P3112, P3121, P3212, P3221, R32, P3m1, P31m, P3c1, P31c, R3m, R3c , P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P61, P65, P62, P64, P63, P-6, P6/m, P63/m, P622 , P6122, P6522, P6222, P6422, P6322, P6mm, P6cc, P63cm, P63mc, P-6m2, P-6c2, P-62m, P-62c, P6/mmm, P6/mcc, P63/mcm, and P63/mmc Any space group in the group formed.
  • the crystal structure of the monoclinic form belongs to the group selected from the group consisting of P2, P21, C2, Pm, Pc, Cm, Cc, P2/m, P21/m, C2/m, P2/c, P21/c and C2/c any space group in .
  • the crystal structure of the high-nickel positive electrode material 100 belongs to the hexagonal crystal structure of the space group R-3m or the monoclinic crystal structure of C2/m structure.
  • the morphology of the crystal particles of the high-nickel positive electrode material 100 includes at least one of approximately spherical, approximately cubic, and approximately rectangular parallelepiped.
  • the pH of the high-nickel cathode material 100 is: 10 ⁇ pH ⁇ 12. In some embodiments, the pH of the high-nickel cathode material 100 is: 10.5 ⁇ pH ⁇ 11.7. In some embodiments, the pH of the high-nickel cathode material 100 can be, for example, 11.1 ⁇ pH ⁇ 11.9, 10.5 ⁇ pH ⁇ 11.0 or 11.0 ⁇ pH ⁇ 11.7, such as 10.6, 10.8, 11.0, 11.2, 11.3 and 11.5, etc., of course It can be other values within the above range, which is not limited here.
  • Controlling the pH of the high-nickel positive electrode material 100 within the above-mentioned range is conducive to further improving the processing performance of the high-nickel positive electrode material 100, such as improving the stability of the positive electrode material in the process of preparing batteries, and it is not easy to produce sedimentation or drop powder.
  • the pH of the high-nickel cathode material 100 is: 11.0 ⁇ pH ⁇ 11.5. In some other typical embodiments, the pH of the high-nickel cathode material 100 is 11.2 ⁇ pH ⁇ 11.3.
  • the powder conductivity of the high-nickel cathode material 100 is greater than 0.02 S/cm.
  • the powder conductivity of the high-nickel cathode material 100 can be, for example, 0.03S/cm-0.08S/cm, 0.05S/cm-0.08S/cm or 0.03S/cm-0.05S/cm, Such as 0.03S/cm, 0.04S/cm, 0.05S/cm, 0.06S/cm, and 0.07S/cm, etc., of course, can also be other values within the above range, which are not limited here.
  • the specific surface area of the high-nickel cathode material 100 is 0.3m 2 /g ⁇ 0.8m 2 /g. In some embodiments, the specific surface area of the high-nickel cathode material 100 can be, for example, 0.3m 2 /g ⁇ 0.5m 2 /g, 0.5m 2 /g ⁇ 0.8m 2 /g or 0.4m 2 /g ⁇ 0.7m 2 /g. 2 /g, such as 0.3m 2 /, 0.4m 2 /, 0.5m 2 / , 0.6m 2 /, 0.7m 2 /, and 0.8m 2 /, etc. Of course, it can also be other values within the above range. Do limited.
  • the specific surface area of the positive electrode material 100 of the present disclosure is within the above range, which can further improve the stability and electrochemical performance of the material, and avoid problems such as powder dropping or gas production during the preparation process due to an excessively large specific surface area.
  • the specific surface area is too small to cause problems such as a decrease in the capacity and rate of the battery.
  • the median particle diameter of the high-nickel cathode material 100 is 2.5 ⁇ m ⁇ 4.5 ⁇ m. In some embodiments, the median particle size of the high-nickel cathode material 100 may be, for example, 3.0 ⁇ m ⁇ 4.5 ⁇ m, 2.5 ⁇ m ⁇ 4.0 ⁇ m, or 3.0 ⁇ m ⁇ 4.0 ⁇ m, such as 2.5 ⁇ m, 3 ⁇ m, 3.5 ⁇ m, 4 ⁇ m, and 4.5 ⁇ m etc. Controlling the average particle size of the high-nickel positive electrode material 100 within the above range is beneficial to improve the compaction density, powder conductivity and cycle life of the high-nickel positive electrode material 100 as a positive electrode sheet.
  • An embodiment of the present disclosure also provides a method for preparing a high-nickel positive electrode material, including the following steps:
  • Step S100 mixing the metal composite hydroxide precursor, the lithium-containing compound and the dopant, and then performing a heat treatment to obtain the matrix material;
  • the above-mentioned dopant includes M2 element and M3 element, and the compound corresponding to the M2 element is an oxide containing only M2 At least one of compound, hydroxide and lithium metal oxide, and the valence of M2 in the compound is greater than or equal to positive 4, and the compound corresponding to the M3 element is at least one of the oxide and hydroxide containing only M3 species, and the valence of M3 in the compound is positive 2;
  • Step S200 coating the base material obtained in step S100 to obtain a high-nickel positive electrode material.
  • the element migration ability of M2 is relatively poor, and the ion migration ability of M3 is strong.
  • the present disclosure combines the dopant containing M2 element and M3 element with After the metal composite hydroxide precursor and the lithium-containing compound undergo a heat treatment, the M2 element is doped on the surface of the material.
  • the M2 element is mainly enriched at the grain boundary of the material, and the M3 element is doped inside the crystal of the material. Due to the valence The M2 element with a valence greater than or equal to positive 4 exists on the surface of the material.
  • the amount of Ni 3+ on the surface of the material is reduced, and the amount of Ni 2+ on the surface is increased at the same time, which prevents the surface of the positive electrode material from being oxidized during delithiation, which is conducive to maintaining the positive electrode.
  • M3 can replace a part of Li + in the internal lattice of the material position, but does not affect the layered structure of the material.
  • the stability of the high-nickel positive electrode material can be improved, and the capacity performance of the high-nickel positive electrode material can be further improved.
  • the preparation method of the present disclosure is specifically introduced below in conjunction with embodiments and examples:
  • preparing the metal composite hydroxide precursor includes: using a co-precipitation method, mixing the metal salt solution, a complexing agent, and a pH regulator to obtain a metal composite hydroxide precursor.
  • the mass ratio of the metal salt solution, complexing agent and pH regulator is 1:(0.01-0.10):(0.1-0.8).
  • the mass ratio of metal salt solution, complexing agent and pH regulator can be, for example, 1:(0.05 ⁇ 0.10):(0.1 ⁇ 0.8), 1:(0.01 ⁇ 0.10):(0.4 ⁇ 0.8 ), 1:(0.05 ⁇ 0.10):(0.1 ⁇ 0.5), such as 1:0.01:0.1, 1:0.05:0.3, 1:0.1:1.5 and 1:0.08:0.8, etc.
  • the mass ratio of the metal salt solution, complexing agent and pH regulator of the present disclosure is within the above range, which can promote the ordered growth of primary particles (that is, the radial growth of crystals), and is beneficial to limit the size of material particles to a certain range It is beneficial to improve the tap density and particle size distribution of the material, and ensure that the particles do not break.
  • the metal salt solution includes at least one of a nickel salt solution, a cobalt salt solution, a manganese salt solution, and an aluminum salt solution.
  • the nickel salt solution includes at least one of nickel sulfate, nickel chloride, nickel sulfamate, nickel bromide, nickel hydroxide, and nickel carbonyl.
  • the cobalt salt solution includes at least one of cobalt sulfate, cobalt chloride, and cobalt nitrate.
  • the manganese salt solution includes at least one of manganese sulfate, manganese nitrate, and manganese chloride.
  • the aluminum salt solution includes at least one of sodium metaaluminate, aluminum sulfate, aluminum chloride, and potassium metaaluminate.
  • the complexing agent can form a complex with nickel, cobalt, manganese or aluminum ions in aqueous solution.
  • the complexing agent includes at least one of ammonium ion donors, hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracil diacetic acid, and glycine, and the ammonium ion donors include ammonia water, ammonium sulfate , ammonium chloride, ammonium carbonate and ammonium fluoride at least one.
  • the temperature of the mixing treatment is 10°C to 80°C.
  • the temperature of the mixing treatment is, for example, 10°C to 50°C, 40°C to 80°C or 20°C to 60°C, such as 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C °C, 80°C, etc., of course, can also be other values within the above range, which are not limited here.
  • the temperature of the mixing treatment is 20°C to 70°C. Controlling the reaction temperature of the co-precipitation method within the above-mentioned range is beneficial to the growth of precursor grains.
  • the pH adjusting agent includes an alkali metal hydroxide.
  • the alkali metal oxide includes at least one of sodium hydroxide and potassium hydroxide.
  • the pH of the mixing treatment is 9-13.
  • the pH of the mixing treatment is, for example, 9 to 12, 10 to 13 or 10 to 12, such as 9, 10, 11, 12 and 13, etc., of course, it can also be other values within the above range, which is not mentioned here. Do limited.
  • the pH of the mixing treatment is 11-13.
  • the mixing treatment time is 10h-200h.
  • the specific time of mixing treatment can be, for example, 50h ⁇ 200h, 10h ⁇ 150h or 50h ⁇ 150h, such as 10h, 20h, 30h, 40h, 50h, 60h, 70h, 80h, 90h, 100h, 110h, 120h , 130h, 140h, 150h, 160h, 180h, 180h, 190h, and 200h, etc., of course, can also be other values within the above range, which are not limited here.
  • the mixing process is carried out under stirring, and the stirring rate is 800 rpm to 1200 rpm.
  • the stirring rate can be, for example, 1000rpm to 1200rpm, 800rpm to 1000rpm or 900rpm to 1100rpm, such as 800rpm, 900rpm, 1000rpm, 1100rpm and 1200rpm, etc.
  • it can also be other values within the above range, and it is not mentioned here Do limited.
  • the mixing treatment is carried out in a reaction tank, and the reaction tank is at least one of a continuous type in which the formed metal composite hydroxide is separated and overflowed, and a batch type in which the reaction is not discharged to the outside of the system until the end of the reaction. kind.
  • the metal composite hydroxide precursor prepared by the mixing treatment is a slurry-like suspension, and the metal composite hydroxide precursor is obtained through solid-liquid separation, washing, and drying.
  • the method of solid-liquid separation includes any one of centrifugation and filtration, and the purpose of solid-liquid separation is to separate the metal composite hydroxide from the solvent.
  • the washing is performed multiple times with deionized water to remove impurities.
  • the drying temperature is from 100°C to 130°C.
  • the drying temperature can be, for example, 100°C to 120°C, 110°C to 130°C or 110°C to 120°C, such as 100°C, 110°C, 120°C and 130°C, etc., of course, it can also be within the above range Other values within are not limited here.
  • the drying time is 12h-24h.
  • the drying time can be, for example, 15h ⁇ 24h, 12h ⁇ 20h or 15h ⁇ 20h, such as 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h and 24h, etc. are other values within the above range, and are not limited here.
  • the average particle size of the metal composite hydroxide precursor is 3 ⁇ m ⁇ 10 ⁇ m.
  • the median particle size of the metal composite hydroxide precursor may be, for example, 5 ⁇ m to 10 ⁇ m, 3 ⁇ m to 8 ⁇ m, or 5 ⁇ m to 9 ⁇ m, such as 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, and 10 ⁇ m, etc. , of course, can also be other values within the above range, which is not limited here.
  • Step S100 mixing the metal composite hydroxide precursor, the lithium-containing compound and the dopant and performing a heat treatment to obtain a matrix material.
  • the dopant includes a compound containing M2 and M3 elements, and the compound corresponding to the M2 element is only M2 At least one of the oxides, hydroxides and lithium metal oxides, and the valence of the M2 element in the compound is greater than or equal to positive 4, and the compound corresponding to the M3 element is the oxide and hydroxide containing only M3 At least one of, and the valency of the M3 element in the compound is positive 2.
  • a dopant is added to perform a heat treatment, so that the M2 element with a valence greater than or equal to positive 4 is mainly doped on the surface of the material, and the M3 element with a valence of positive 2 mainly enters the interior of the material. Understandably, through a After heat treatment, the M3 element can directly enter the crystal interior to replace part of the Li site, the M2 element is mainly enriched at the grain boundary of the material, and a small part of the M2 element enters the crystal interior under the induction of the M3 element, and a small amount replaces the element inside the crystal location.
  • the mass ratio of the metal composite hydroxide precursor, the lithium-containing compound and the dopant is 1:(0.46 ⁇ 0.49):(0.001 ⁇ 0.005).
  • the mass ratio of metal composite hydroxide precursor, lithium-containing compound and dopant can be, for example, 1:(0.46 ⁇ 0.48):(0.001 ⁇ 0.003), 1:(0.46 ⁇ 0.47):( 0.001 ⁇ 0.002) or 1:(0.45 ⁇ 0.47):(0.002 ⁇ 0.003), such as 1:0.46:0.002, 1:0.47:0.003, 1:0.48:0.001, 1:0.047:0.002 and 1:0.048:0.01, etc. , of course, can also be other values within the above range, which is not limited here.
  • the mass ratio of the metal composite hydroxide precursor, lithium-containing compound and dopant of the present disclosure is within the above range, which can further improve the discharge capacity and rate capacity of the material, so that the material maintains a high capacity retention rate and a low DCR growth rate; a low mass ratio of the metal composite hydroxide precursor to the lithium-containing compound will affect the discharge capacity of the material, rate capacity, and a high mass ratio of the metal composite hydroxide precursor to the lithium-containing compound will cause the material
  • the surface residual alkali is high, the capacity is reduced, and the cost is increased.
  • the atomic ratio of metal Me in the metal composite hydroxide precursor to Li in the lithium-containing compound is 1.0 ⁇ Li/Me ⁇ 1.2.
  • Li/Me can be 1.01, 1.05, 1.1, 1.15, and 1.19, etc.
  • Me represents the sum of the atomic numbers of all metals in the metal composite hydroxide precursor, and the metal in the metal composite hydroxide precursor
  • the atomic ratio of Me to Li in the lithium-containing compound is controlled within the above range, which is beneficial to the formation of matrix material grains and the improvement of the electrochemical performance of the material.
  • lithium-containing compounds include lithium-containing salts, lithium-containing hydroxides.
  • the lithium-containing compound includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate.
  • M2 and M3 elements each include at least one of Zr, Ti, Nb, Ce, Hf, W, Mo, Ta, Ge, Sn, Sr, Mg and Ba, and M2 and M3 are different .
  • the dopant includes at least one of lithium zirconate, lithium titanate, niobium oxide, lithium tungstate, barium oxide, and magnesium hydroxide.
  • the molar ratio n M2 : n M3 of the M2 element and the M3 element is greater than or equal to 2:1.
  • nM2 : nM3 can be, for example, (2-6):1, (2-5):1 or (3-5):1, such as 2:1, 3:1, 4:1 , 5:1 and 6:1, etc., within the above-mentioned limited range, high-valent elements (M2 elements with a valence greater than or equal to positive 4) can be effectively doped on the surface layer of the material, while low-valent elements (M3 with a valence of positive 2) Elements) can enter the interior of the material with only a small amount of addition, and too much addition of low-priced elements will inhibit the electrochemical performance of the material.
  • the molar ratio of the M2 element to the M3 element in the dopant is 3:1 ⁇ nM2: nM3 ⁇ 5 :1.
  • the dopant has an average particle size of 10 nm to 50 nm.
  • the average particle size of the dopant can be, for example, 10nm to 40nm, 20nm to 50nm or 20nm to 40nm, such as 10nm, 20nm, 30nm, 40nm and 50nm, etc. Of course, it can also be other particles within the above range. value, which is not limited here.
  • the temperature of the primary heat treatment is 680°C-900°C.
  • the temperature of one heat treatment is, for example, 700°C-900°C, 680°C-800°C or 700°C-800°C, such as 680°C, 700°C, 720°C, 750°C, 780°C, 800°C, 820°C °C, 850°C, and 900°C, etc., of course, can also be other values within the above range, which are not limited here.
  • the temperature of the primary heat treatment is 780°C-870°C. Controlling the temperature of the primary heat treatment within the above range is beneficial to the grain growth of the high-nickel positive electrode material.
  • the time for one heat treatment is 5h-20h.
  • the time of one heat treatment is, for example, 5h-15h, 10h-20h or 10h-18h, such as 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 18h , 18h, 19h, and 20h, etc., of course, can also be other values within the above range, which are not limited here.
  • the time for one heat treatment is 8h-15h.
  • the heating rate of one heat treatment is 50°C/h-550°C/h. In some embodiments, the heating rate of one heat treatment is, for example, 100°C/h to 550°C/h, 150°C/h to 500°C/h or 200°C/h to 300°C/h, such as 50°C/h, 100°C/h °C/h, 140°C/h, 200°C/h, 250°C/h, 300°C/h, 380°C/h, 400°C/h, 450°C/h, 500°C/h and 550°C/h, etc., Of course, other values within the above range may also be used, which are not limited here. In some typical embodiments, the heating rate of one heat treatment is 100°C/h-400°C/h. In some other typical embodiments, the heating rate of the primary heat treatment is 140°C/h-380°C/h.
  • the oxygen content of the matrix material is greater than or equal to 85%.
  • the oxygen content in the matrix material may be, for example, 85%-98%, 85%-95%, or 89%-97%, such as 85%, 86%, 87%, 88%, 89%, 90% %, 91%, 92%, 93%, 94%, 95%, 96%, 97%, etc., of course, can also be other values within the above range, which are not limited here.
  • the oxygen content of the matrix material is greater than or equal to 95%.
  • the primary heat treatment equipment includes a static box furnace or a roller kiln continuous furnace.
  • Step S200 coating the base material obtained in step S100 to obtain a high-nickel positive electrode material.
  • Step 201 mixing the matrix material with the first coating agent and performing a second heat treatment to obtain a primary coating result.
  • the mass ratio of the matrix material to the first coating agent is 1000:(0.5-3).
  • the mass of the matrix material and the first coating agent can be, for example, 1000: (1-3), 1000: (1.5-3) or 1000: (2.5-3), such as 1000: 0.5, 1000 : 1, 1000: 1.5, 1000: 2, 1000: 2.5, 1000: 3, etc.
  • other values within the above range can also be used, which are not limited here.
  • the first coating agent includes a metal element or a non-metal element with a valence greater than or equal to positive 3.
  • the present disclosure adds a metal element or a non-metal element with a valence greater than or equal to positive 3, and the high-nickel positive electrode is made by valence balance.
  • the amount of Ni 2+ on the surface of the material remains unchanged or further increases, which improves the stability of the material structure, avoids the contact between the material and the moisture in the air to generate alkaline impurities, and reduces the gas production of the material.
  • the first coating agent includes at least one of oxides, salts or hydroxides of metal elements or non-metal elements with a valence greater than or equal to positive 3.
  • the metal element or non-metal element includes at least one of Al, Ti, P, Si, Nb, Y, W, Cr, Zr or La.
  • the first coating agent may be at least one of lithium aluminate, lithium titanate, lithium lanthanum titanate, yttrium oxide, aluminum oxide and titanium oxide.
  • the temperature of the secondary heat treatment is 600°C-800°C. In some embodiments, the temperature of the secondary heat treatment is, for example, 650°C-800°C, 600°C-750°C or 700°C-800°C, such as 600°C, 650°C, 680°C, 700°C, 720°C, 750°C, 780° C. and 800° C., etc., of course, may also be other values within the above range, which are not limited here. In some typical embodiments, the temperature of the secondary heat treatment is 650°C-750°C.
  • the time for the secondary heat treatment is 1 h to 20 h.
  • the time of the secondary heat treatment is, for example, 5h-20h, 10h-20h or 5h-10h, such as 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 18h, 18h, 19h, and 20h, etc., of course, may also be other values within the above range, which are not limited here.
  • the time for the secondary heat treatment is 3 hours to 10 hours.
  • the heating rate of the secondary heat treatment is 50°C/h-550°C/h. In some embodiments, the heating rate of the secondary heat treatment is, for example, 100°C/h to 550°C/h, 50°C/h to 500°C/h, or 150°C/h to 450°C/h, such as 50°C/h, 100°C/h, 140°C/h, 200°C/h, 250°C/h, 300°C/h, 380°C/h, 400°C/h, 450°C/h, 500°C/h and 550°C/h etc. , of course, can also be other values within the above range, which is not limited here. In some typical embodiments, the heating rate of the secondary heat treatment is 100°C/h-400°C/h. In some other typical embodiments, the temperature increase rate of the secondary heat treatment is 140° C./h to 380° C./h.
  • the oxygen content in the primary coating resultant is greater than or equal to 85%.
  • the oxygen content in the primary coating result can be, for example, 85%-95%, 90%-97%, or 89%-97%, such as 85%, 86%, 87%, 88%, 89% %, 90%, 91%, 92%, 93%, 94%, 95%, 96% and 97%, etc., of course, can also be other values within the above range, which are not limited here.
  • the oxygen content in the primary coating product is greater than or equal to 95%.
  • the equipment for the secondary heat treatment includes a static box furnace or a roller kiln continuous furnace.
  • the base material is mixed with the first coating agent, then subjected to a second heat treatment, then washed under constant temperature conditions, and then dried under vacuum conditions after washing to obtain a primary coating.
  • the temperature of the constant temperature condition is 10°C to 25°C.
  • the temperature of the constant temperature condition can be, for example, 15°C-25°C, 10°C-20°C or 15°C-20°C, such as 10°C, 11°C, 12°C, 13°C, 14°C, 15°C, 16° C., 17° C., 18° C., 19° C., 20° C., 21° C., 22° C., 23° C., 24° C., and 25° C., etc., of course, can also be other values within the above range, which are not limited here.
  • the drying temperature is 100°C to 200°C.
  • the drying temperature can be 120°C-200°C, 150°C-200°C or 100°C-150°C, such as 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C °C, 170°C, 180°C, 190°C, and 200°C, etc., of course, may also be other values within the above range, which are not limited here.
  • Step S202 mixing the resultant of the first coating with the second coating agent and performing three heat treatments to obtain a high-nickel positive electrode material.
  • the second cladding layer 144 includes a compound including at least one of B, La, and Al.
  • the second cladding layer 144 includes a compound containing at least one of B, La, and Al, which is an oxide, an acid, or a lithium-containing salt.
  • the second cladding layer 144 includes a boron-containing compound including a boron-containing oxide, a boron-containing acid, or a boron- and lithium-containing salt.
  • the second cladding layer 144 includes boron-containing compounds including boron-containing oxides, boron-containing acids, boron-containing and lithium-containing salts.
  • the boron-containing oxide includes but not limited to B 2 O 3 or B 2 O and the like.
  • boron-containing acids include, but are not limited to, H 3 BO 3 .
  • boron and lithium containing salts include, but are not limited to, Li i B j O k , where 2 ⁇ i ⁇ 3, 1 ⁇ j ⁇ 8, 3 ⁇ k ⁇ 13.
  • salts containing boron and lithium include, but are not limited to, B 2 O 3 , H 3 BO 3 , Li 2 OB 2 O 3 , Li 3 BO 3 , Li 2 B 4 O 7 , Li 2 B 2 O 7 and At least one of Li 2 B 8 O 13 .
  • the second coating agent is a boron-containing compound
  • the boron-containing compound includes B 2 O 3 , H 3 BO 3 , Li 2 OB 2 O 3 , Li 3 BO 3 , Li 2 B 4 O 7 , Li At least one of 2 B 2 O 7 and Li 2 B 8 O 13
  • the above-mentioned boron-containing compound can not only chemically react with the basic impurities on the surface of the material but also can Cover the surface of the material to form a stable coating layer, which not only reduces the alkaline impurities on the surface of the material but also protects the surface of the material, reduces the decomposition of Li 2 CO 3 in the alkaline impurities on the surface of the material to produce gas, and reduces the side reaction between the alkaline impurities on the surface of the material and the electrolyte Gas production.
  • the mass ratio of the primary coating product to the second coating agent is 1:(0.0005-0.005).
  • the mass ratio of the primary coating resultant to the second coating agent can be, for example, 1:(0.0008-0.003), 1:(0.001-0.0025) or 1:(0.0015-0.002), such as 1: 0.0005, 1: 0.0007, 1: 0.0009, 1: 0.001 and 1: 0.0015, 1: 0.002, 1: 0.0025, 1: 0.003, etc.
  • other values within the above range can also be used, which are not limited here.
  • the temperature of the three heat treatments ranges from 200°C to 400°C.
  • the temperature of the three heat treatments is, for example, 200°C to 300°C, 300°C to 400°C or 250°C to 350°C, such as 200°C, 250°C, 280°C, 300°C, 320°C, 360°C, 380°C °C, 400°C, etc., of course, can also be other values within the above range, which are not limited here.
  • the temperature of the three heat treatments is 250°C-360°C.
  • the time for the three heat treatments is 1 h to 20 h.
  • the time of three heat treatments is, for example, 5h-20h, 1h-15h or 4h-16h, such as 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h , 14h, 15h, 16h, 18h, 18h, 19h, and 20h, etc., of course, can also be other values within the above range, which are not limited here.
  • the time for the three heat treatments is 5h-10h.
  • the heating rate of the three heat treatments is 50°C/h-550°C/h. In some embodiments, the heating rate of the three heat treatments is, for example, 200°C/h to 550°C/h, 50°C/h to 350°C/h, or 200°C/h to 300°C/h, such as 50°C/h, 100°C/h °C/h, 140°C/h, 200°C/h, 250°C/h, 300°C/h, 380°C/h, 400°C/h, 450°C/h, 500°C/h and 550°C/h, etc., Of course, other values within the above range may also be used, which are not limited here. In a typical implementation, the heating rate of the three heat treatments is 100°C/h-400°C/h. In some other typical embodiments, the heating rate of the three heat treatments is 140°C/h-380°C/h.
  • the oxygen content of the high-nickel positive electrode material is greater than or equal to 85%.
  • the oxygen content of the high-nickel positive electrode material can be, for example, 85% to 98%, 85% to 95%, or 89% to 97%. %, such as 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96% and 97%, etc., of course, can also be within the above range Other values are not limited here.
  • the oxygen content of the high-nickel cathode material is greater than or equal to 95%.
  • the equipment for the tertiary heat treatment includes a static box furnace or a roller kiln continuous furnace.
  • the three heat treatments also include the steps of sieving and demagnetization.
  • the purpose of sieving is 200 mesh to 400 mesh.
  • the mesh size of the sieve can be, for example, 300 mesh to 400 mesh, 200 mesh to 300 mesh or 240 mesh to 360 mesh, such as 200 mesh, 210 mesh, 250 mesh, 280 mesh, 300 mesh, 350 mesh , 380 mesh, and 400 mesh, etc., of course, can also be other values within the above range, which are not limited here.
  • An embodiment of the present disclosure also provides a lithium-ion secondary battery, including a positive pole piece, a negative pole piece, a separator, a non-aqueous electrolyte, and a casing.
  • the positive electrode sheet includes a current collector and the above-mentioned high-nickel positive electrode material or the positive-electrode material prepared by the above-mentioned high-nickel positive electrode material coating method on the current collector.
  • the high-nickel positive electrode material of the present disclosure uses AlK ⁇ rays for powder XPS measurement, when the Ni2P 3/2 peak that appears in the range of 850eV to 870eV with binding energy is divided into peaks and After fitting, the peak area S1 of Ni 2+ , the peak area S2 of Ni 3+ , the half-peak width ⁇ of Ni 2+ and the peak half-width ⁇ of Ni 3+ satisfy: S1/(S1+S2)>0.5 And 0.9 ⁇ / ⁇ 1.5, indicating that the amount of Ni 3+ on the surface of the high-nickel positive electrode material of the present disclosure is small, and the amount of Ni 2+ is large, and it can also prevent the surface of the high-nickel positive electrode material from being oxidized during delithiation, which is beneficial Maintain the stability of the structure of the positive electrode material, thereby avoiding the loss of the positive electrode active material and electrolyte during the charging and discharging process, further increasing the capacity of the
  • the positive electrode material of the present disclosure can be used in batteries During long-term cycling, the DC internal resistance growth of the battery is significantly suppressed.
  • the M2 element is doped on the surface of the material and the M3 element is doped inside the material by heat-treating the dopant containing the M2 element with a valence greater than or equal to positive 4 and the M3 element with a valence equal to positive 2.
  • the M2 element with a valence greater than or equal to positive 4 exists on the surface of the material, the amount of Ni 3+ on the surface of the material is reduced through the balance of the valence, and the amount of Ni 2+ on the surface is increased at the same time, so as to prevent the surface of the positive electrode material from being oxidized during delithiation.
  • the M3 element with a valence equal to positive 2 enters the material, which can inhibit the phase transition of H2 ⁇ H3 during the charging and discharging process of the material, and improve the structural stability.
  • M3 can replace a part of the internal lattice of the material
  • the present disclosure can improve the stability of the high-nickel positive electrode material and further improve the capacity performance of the high-nickel positive electrode material by doping the elements containing M2 and M3 to form a matrix material .
  • Ni 0.885 Co 0.09 Mn 0.025 (OH) 2 precursor was prepared by the co-precipitation method.
  • step (2) Mix the matrix material prepared in step (1) and nanometer Al 2 O 3 uniformly according to the mass ratio of 1:0.002, and then perform a second heat treatment at 700°C. °C while washing with water, and after the dehydration step, the mixture was dried in a vacuum atmosphere at 150 °C to obtain a primary coating product.
  • the schematic diagram of the structure of the positive electrode material 100 in this embodiment is shown in 19, the first coating layer 142 is formed on the surface of the primary particle 122 (the primary particle 122 is the matrix material prepared in step (1)), that is, obtained by the step (2) The prepared primary coating product), the second coating layer 144 is formed on the surface of the first coating layer 142, and the overall distribution of the positive electrode material 100 presents a single crystal particle structure, that is, the primary particle 122 (that is, formed by Step (3) preparation obtains).
  • FIG. 2 it is the SEM image of the high-nickel cathode material of this embodiment, and the morphology of the crystal particles includes approximately spherical, approximately cubic and approximately rectangular parallelepiped.
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a single crystal particle structure, that is, primary particles.
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a single crystal particle structure, that is, primary particles.
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a single crystal particle structure, that is, primary particles.
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a single crystal particle structure, that is, primary particles.
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a single crystal particle structure, that is, primary particles.
  • the structure of the high-nickel positive electrode material in this embodiment is similar to that of Example 1, and the overall distribution of the positive electrode material presents a single crystal particle structure, that is, primary particles
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a single crystal particle structure, that is, primary particles.
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a single crystal particle structure, that is, primary particles.
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a single crystal particle structure, that is, primary particles.
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a single crystal particle structure, that is, primary particles.
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a single crystal particle structure, that is, primary particles.
  • Example 1 The difference from Example 1 is that the primary heat treatment temperature in step (1) is 650°C.
  • the schematic diagram of the structure of the positive electrode material 100 in this embodiment is shown in 20.
  • the structure of the high-nickel positive electrode material in this embodiment is similar to that of Embodiment 1, the difference is that some primary particles 122 gather to form secondary particles 124, and the positive electrode
  • the overall distribution of the material presents a polycrystalline particle structure, that is, secondary particles.
  • Example 1 The difference from Example 1 is that the primary heat treatment temperature in step (1) is 680°C.
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a polycrystalline particle structure, ie, secondary particles.
  • Example 1 The difference from Example 1 is that the primary heat treatment temperature in step (1) is 700°C.
  • the structure of the high-nickel anode material in this embodiment is similar to that in Embodiment 13, and the overall distribution of the anode material presents a polycrystalline particle structure, that is, secondary particles.
  • Example 1 The difference from Example 1 is that the primary heat treatment temperature in step (1) is 850°C.
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a single crystal particle structure, that is, primary particles.
  • Example 1 The difference from Example 1 is that the primary heat treatment temperature in step (1) is 900°C.
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a single crystal particle structure, that is, primary particles.
  • Example 1 The difference from Example 1 is that the primary heat treatment temperature in step (1) is 910°C.
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a single crystal particle structure, that is, primary particles.
  • step (2) Al 2 O 3 is replaced by lithium aluminate.
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a single crystal particle structure, that is, primary particles.
  • step (2) Al 2 O 3 is replaced by titanium oxide.
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a single crystal particle structure, that is, primary particles.
  • step (3) H 3 BO 3 is replaced by Li 3 BO 3 .
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a single crystal particle structure, that is, primary particles.
  • step (3) H 3 BO 3 is replaced by B 2 O 3 .
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the overall distribution of the cathode material presents a single crystal particle structure, that is, primary particles.
  • step (3) is not carried out.
  • FIG. 25 for a schematic structural view of the high-nickel positive electrode material in this embodiment, only the first coating layer is formed on the surface of the primary particles, and the overall distribution of the positive electrode material presents a single crystal particle structure.
  • step (2) is not performed.
  • FIG. 26 for a schematic structural view of the high-nickel positive electrode material in this embodiment, only the second coating layer is formed on the surface of the primary particles, and the overall distribution of the positive electrode material presents a single crystal particle structure.
  • Example 1 The difference from Example 1 is that the precursor is Ni 0.83 Co 0.12 Mn 0.06 (OH) 2 precursor.
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the entire cathode material is distributed with single crystal particles, that is, primary particles.
  • Example 2 The difference from Example 1 is that the precursor is Ni 0.9 Co 0.05 Mn 0.05 (OH) 2 precursor.
  • the structure of the high-nickel cathode material in this embodiment is similar to that in Embodiment 1, and the entire cathode material is distributed with single crystal particles, that is, primary particles.
  • Example 1 The difference from Example 1 is that the dopant in step (1) is replaced by MgO and Al 2 O 3 .
  • Example 1 The difference from Example 1 is that the dopant in step (1) is replaced by SrO and MgO.
  • Example 1 The difference from Example 1 is that the dopant in step (1) is replaced by Al 2 O 3 , Y 2 O 3 .
  • Example 1 The difference from Example 1 is that the dopant in step (1) is replaced by Y 2 O 3 and MgO.
  • Example 1 The difference from Example 1 is that the dopant in step (1) is replaced by La 2 O 3 , Al 2 O 3 .
  • Example 1 The difference from Example 1 is that the dopant in step (1) is replaced by ZrO 2 and TiO 2 .
  • the content of basic impurities on the surface of high nickel materials is a characteristic of the surface of the material, which can be quantitatively measured by analyzing the reaction products between the surface and water. If the high nickel material powder is immersed in water, a surface reaction occurs. During the reaction, the pH of the water increases (as basic impurities dissolve) and the base content is quantified by pH titration. The result of the titration is the basic impurity content.
  • the content of basic impurities can be measured as follows: 5.0 g of high nickel material powder is immersed in 100 ml of deionized water and stirred for 10 minutes in a sealed glass flask. After stirring to dissolve the base, the suspension of powder in water was filtered to obtain a clear solution.
  • the point of inflection y1 between the first and second plateau and the point of inflection y2 after the second plateau are obtained from the respective minima of the derivative dpH/dVol of the pH curve.
  • the second inflection point is generally near pH 4.7. Then the results are expressed in LiOH and Li 2 CO 3 weight percent as shown in the following formulas (3) and (4):
  • X-ray photoelectron spectroscopy can analyze the depth range from the material surface to about 5nm to 10nm (generally about 5nm), so it can quantitatively analyze the concentration of each element in about half of the surface layer. In addition, by performing narrow scan analysis, the bonding state of elements can be analyzed.
  • X-ray photoelectron spectroscopy can be performed, for example, using ULVAC-PHI, X-ray photoelectron spectroscopy (Quantera II).
  • X-ray source Al monochrome 100 ⁇ m, 25W, 15kV; no etching on the surface; photoelectron extraction angle: 45°; bonding energy correction: set the CC peak of the C1s spectrum to 284.6eV;
  • the peak Ni2P 3/2 of the Ni bonding part that appears at the position of the binding energy of 850eV to 870eV is divided into peaks and curve fitting, and the Ni 2+ peak area and Ni 3+ peak area are obtained
  • the peak O1S of the O-bonded part that appears at the position of the binding energy of 526eV-540eV is divided into peaks and curve fitting, and the area of the O1S lattice oxygen peak and the O1S impurity oxygen peak area are obtained.
  • DCIR amplifier (V1-V2)/1.5C0*1000 (unit: m ⁇ ) (5)
  • Thickness expansion rate (thickness after storage - thickness before storage) / (thickness before storage) (7)
  • a Hitachi E-3500 ion mill was used to cut the high-nickel material after 500 cycles of high-temperature cycling, and its cross-sectional morphology was observed on a Hitachi S4800 cold field emission scanning electron microscope.
  • Test method GB/T 19587-2017 "Determination of specific surface area of solid matter by gas adsorption BET method"
  • Ni2P3 /2 and O1S split peaks and the area ratio after fitting of the high-nickel positive electrode material XPS prepared by each embodiment and comparative example are shown in Table 1 below, wherein embodiment 1, embodiment 8, and comparative example 1 , the Ni2P 3/2 of comparative example 2 peaks and fittings are shown in Fig. 3, Fig. 4, Fig. 5 and Fig. 6 successively, the O1S of embodiment 1, embodiment 8, comparative example 1, comparative example 2 The peaks and fits are shown in Figure 7, Figure 8, Figure 9 and Figure 10.
  • the high-nickel cathode material prepared in the present disclosure satisfies S1/(S1+S2)>0.5 and 0.9 ⁇ / ⁇ 1.5 after testing, indicating high-nickel
  • the amount of Ni 3+ on the surface of the material matrix is small, and the amount of Ni 2+ is large, which prevents the surface of the positive electrode material from being oxidized during delithiation, which is conducive to maintaining the stability of the structure of the positive electrode material, thereby avoiding the loss of the positive electrode active material and electrolyte , to further increase the capacity of the positive electrode material, so that the high-temperature cycle performance of the high-nickel positive electrode material is significantly improved.
  • the positive electrode material of the present disclosure can be used in batteries During long-term cycling, the DC internal resistance growth of the battery is significantly suppressed.
  • Embodiment 1, embodiment 8, comparative example 1, the Ni2P 3/2 of comparative example 2 peak splitting and fitting are shown in Figure 3, Figure 4, Figure 5 and Figure 6 successively, embodiment 1, embodiment 8, The peak division and fitting of O1S in Comparative Example 1 and Comparative Example 2 are shown in Figure 7, Figure 8, Figure 9 and Figure 10.
  • the S1/(S1+S2) area ratio of the high-nickel cathode material prepared in the present disclosure and the material prepared in the comparative example have changed significantly, and the S1/(S1+S2) area ratio of the samples in the examples of the present disclosure>1, indicating that the surface
  • the amount of Ni 2+ is obviously more than that of Ni 3+
  • the area ratio of S1/(S1+S2) in the comparative example is ⁇ 1;
  • the area ratio of O1S lattice oxygen /O1S impurity oxygen is basically>0.5, which shows that the The alkaline impurities on the surface of the material are relatively low.
  • the high-nickel positive electrode material of the disclosed embodiment has a lower sum of the surface basic impurities, and the surface basic impurities LiOH and Li 2 CO 3 of the samples tested in the comparative example are higher.
  • the high-nickel positive electrode materials prepared according to Examples 1-26 and Comparative Examples 1-6 of the present disclosure have a high-temperature 45°C full battery 1C/1C cycle capacity retention rate of 300 cycles at different voltages. After high-temperature performance tests, it can be known that: the examples of the present disclosure Compared with the positive electrode material of the comparative example, the high-temperature cycle performance has changed significantly. Under the condition of 2.5V to 4.2V, the capacity retention rate of the positive electrode material of some embodiments of the present disclosure is about 95%, while the capacity retention rate of the positive electrode material of the comparative example is 93%. % or less, tested under the condition of 2.5V-4.25V, because there is a phase transition, the high-temperature cycle performance of the samples of the experimental example and the comparative example are all reduced, but some examples are still significantly better than the comparative example.
  • the high-nickel positive electrode materials prepared according to the examples and comparative examples of the present disclosure tested the DC internal resistance growth of the full battery 1C/1C at a high temperature of 45°C under the condition of 2.5V-4.2V and 100 cycles per cycle, Example 1, Example 8, and Comparative Example
  • the comparative analysis of the capacity differential curves of 1 and Comparative Example 2 is shown in Figure 11, Figure 12, Figure 13, and Figure 14. Combining Table 1 and the accompanying drawings, it can be seen that the DC internal resistance of the positive electrode materials in the embodiment of the present disclosure and the comparative example increased significantly. Change, the DC internal resistance growth of the embodiment is obviously lower than that of the comparative example.
  • the high-nickel positive electrode materials prepared according to the examples and comparative examples of the present disclosure are made into full batteries, and then the gas production is tested at a high temperature of 60°C.
  • the thickness of the battery is measured every 20 days, and the thickness expansion rate is calculated. It can be seen from Table 1: Example Compared with the comparative example, the battery thickness growth has changed obviously, but the thickness expansion growth of the embodiment is obviously lower than that of the comparative example.
  • the primary synthesis temperature of the material is controlled within the scope of the present disclosure, the positive electrode material has excellent electrochemical performance, and the temperature of the primary heat treatment is lower than the range defined in the present disclosure (Example 12) or the temperature of the primary heat treatment. If the temperature is higher than the range defined in the present disclosure (Example 18), there will be disadvantages such as poor cycle performance and high expansion rate.
  • the embodiment of the present disclosure performs a second layer of coating on the basis of the first layer of coating of the material, which not only reduces the alkaline impurities on the surface of the material but also protects the surface of the material, reducing The Li 2 CO 3 in the alkaline impurities on the surface of the material decomposes to produce gas, which reduces the side reaction of alkaline impurities on the surface of the material and the electrolyte to produce gas, thereby further improving the cycle performance of the material.
  • the positive electrode material obtained by coating the base material only once has the disadvantage of poor cycle performance.
  • the embodiment of the present disclosure performs primary coating on the inner layer while the material is coated twice, and the Ni 2+ on the surface of the high-nickel positive electrode material is made by valence balance.
  • the quantity remains the same or further increases, which improves the stability of the material structure, avoids the contact between the material and the moisture in the air to generate alkaline impurities, reduces the gas production of the material, and thus improves the circulation of the material and reduces the expansion rate of the material .
  • the positive electrode material obtained only by coating the base material twice has the disadvantages of poor cycle performance and high expansion rate.
  • Example 1, 8, 25, 26 and Comparative Examples 1, 2, 6 the high-nickel materials were circulated for 300 cycles for argon ion section analysis, and the section analysis results of Examples 1, 8, 25, and 26 are shown in Figures 15 and 16. , 19 and 20, see accompanying drawing 17,18 and 21 for the result of cross-section analysis of comparative example 1,2,6, by comparing the result of cross-section analysis of embodiment and comparative example, it can be seen that the material interior of embodiment 1,8,25,26 No cracks occurred, but cracks appeared inside the materials of Comparative Examples 1, 2, and 6. This step shows that the present disclosure is conducive to the stability of the material structure by doping with high valence and low valence at the same time, thereby helping to further improve the cycle performance of the material. .
  • the disclosure provides a high-nickel positive electrode material and a preparation method thereof, and a lithium-ion battery.
  • the high-nickel positive electrode material of the present disclosure has a small amount of Ni 3+ and a large amount of Ni 2+ on the surface of the high-nickel positive electrode material, which can prevent the surface of the high-nickel positive electrode material from detaching When lithium is oxidized, it can improve the high-temperature cycle performance and structural stability of high-nickel cathode materials, avoid the loss of positive-electrode active materials and electrolytes, and further increase the capacity of positive-electrode materials, making the high-temperature cycle performance of high-nickel cathode materials significantly improved. Improved, with excellent practical performance.

Abstract

本公开涉及一种高镍正极材料及其制备方法、锂离子电池，所述高镍正极材料的化学通式为式(1)所示：Li xNi 1-(a+b+c+d+e+f)Co aM1 bM2 cM3 dM4 eM5 fO 2(1)，其中，0.95≤x≤1.2，0≤a≤0.15，0≤b≤0.10，0≤c≤0.05，0≤d≤0.05，0≤e≤0.05，0≤f≤0.05，0＜a+b+c+d+e+f≤0.2；本公开的高镍材料表面的Ni 3+数量较少、Ni 2+数量较多，能够避免正极材料表面在脱锂时被氧化，有利于维持正极材料结构的稳定性，从而避免了正极活性材料和电解液的损失，进一步提高正极材料的容量，使得高镍正极材料的高温循环性能得到明显改善。

Description

一种高镍正极材料及其制备方法、锂离子电池
相关申请的交叉引用
本公开要求于2021年12月08日提交中国专利局的申请号为“CN202111491138.2”名称为“一种高镍正极材料及其制备方法、锂离子电池”的中国专利申请的优先权，其全部内容通过引用结合在本公开中。
技术领域
本公开属于正极材料技术领域，尤其涉及一种高镍正极材料及其制备方法、锂离子电池。
背景技术
锂离子电池具有能量密度高、安全性能好、循环寿命长并且环境友好而被广泛应用于笔记本电脑、手机、数码产品等领域；同时，随着人们环保意识的增强，锂离子电池正逐步作为动力电池应用于交通工具领域，如电动汽车，电动大巴等，市场对锂离子电池的比容量、能量密度、功率密度、使用寿命等也提出了越来越高的要求，尤其是比容量。锂离子电池中用的最多的正极材料主要是橄榄石结构的LiFePO 4、层状结构LiCoO 2和层状结构的锂镍类氧化物材料；橄榄石结构的LiFePO 4已经达到了容量极限，后续的主要应用在储能和低续航电动车领域；层状结构LiCoO 2主要用于消费电池领域；锂镍类氧化物材料则在电动汽车领域应用广泛；在锂镍类氧化物材料中，镍是主要的氧化还原反应元素，提高镍含量则可以有效提升这类材料的比容量，因此发展高镍材料成为市场趋势。
目前制约高镍三元材料在动力电池中广泛运用的主要因素是高温性能差、直流内阻增长快和产气；而引起这些不利因素的原因主要有三方面，一方面是高镍三元材料的本征结构随着充放电的进行会逐渐发生不可逆的结构改变，且镍含量越高发生的结构改变越大；高镍材料在进行充放电过程中，镍的化合价会发生相应变化，对应着锂离子的脱出和嵌入，在相同电压下，镍含量越高脱出的锂离子越多，材料发生的体积变化越大，而体积的变化会伴随材料内部应力的释放，从而导致高镍材料出现裂纹；特别是对于充电状态下的高镍材料，电解液会通过裂纹进入到材料内部，与高活性的Ni 4+发生氧化还原反应，从而导致材料结构改变；其次是当高镍三元材料脱锂时，材料表面的Ni 3+会转化成强氧化性的Ni 4+，Ni 4+容易与有机电解液发生氧化还原反应，从而使正极活性物质和电解液损失，导致容量衰减、直流内阻增长和气体产生；最后，高镍三元材料在合成过程中容易产生碱性杂质(包括材料表面残余的Li 2CO 3和LiOH等)，这些碱性杂质无导电性且易与电解液发生反应，造成电池产气和电池极化。
因此，为了提高高镍三元材料在动力电池中广泛运用，现在急需一种能够解决高温性能差、直流内阻增长快和产气的高镍正极材料。
发明内容
本公开提供一种高镍正极材料，所述高镍正极材料的化学通式为式(1)所示：
Li xNi 1-(a+b+c+d+e+f)Co aM1 bM2 cM3 dM4 eM5 fO 2   (1)
其中，0.95≤x≤1.2，0≤a≤0.15，0≤b≤0.10，0≤c≤0.05，0≤d≤0.05，0≤e≤0.05，0≤f≤0.05，0＜a+b+c+d+e+f≤0.2；
所述高镍正极材料使用AlKα射线进行粉末XPS测定，当将结合能在850eV～870eV范围内出现的Ni2P 3/2峰进行分峰和拟合后，将Ni 2+的峰值面积设定为S1，Ni 3+的峰值面积设定为S2，将Ni 2+的峰半峰宽设定为α，将Ni 3+的峰半峰宽设定为β，S1、S2、α和β满足以下关系：
S1/(S1+S2)＞0.5且0.9＜α/β＜1.5(2)。
任选地，所述正极材料包括二次粒子和/或一次粒子，所述一次粒子的至少部分表面包覆有包覆层，所述二次粒子包括多个带有包覆层的一次粒子。
任选地，所述包覆层包括第一包覆层和第二包覆层，所述第一包覆层形成于所述一次粒子的表面，所述第二包覆层形成于所述第一包覆层的表面。
任选地，所述包覆层包括第一包覆层，所述第一包覆层形成于所述一次粒子的表面。
任选地，所述包覆层包括第二包覆层，所述第二包覆层形成于所述一次粒子的表面。
任选地，所述包覆层包括第一包覆层和第二包覆层，所述第一包覆层包括在所述高镍正极材料中化合价大于等于正3价的元素。
任选地，所述包覆层包括第一包覆层和第二包覆层，所述第一包覆层包括Al、Ti、P、Si、Nb、Y、W、Cr、Zr和La中的至少一种。
任选地，所述包覆层包括第一包覆层和第二包覆层，所述第一包覆层包括含有Al、Ti、P、Si、Nb、Y、W、Cr、Zr和La中的至少一种的化合物。
任选地，所述包覆层包括第一包覆层和第二包覆层，所述第一包覆层包括含有Al、Ti、P、Si、Nb、Y、W、Cr、Zr和La中的至少一种的化合物，所述化合物为氧化物、氢氧化物及盐中的至少一种。
任选地，所述包覆层包括第一包覆层和第二包覆层，所述第二包覆层包括含有B、La和Al中的至少一种的化合物。
任选地，所述包覆层包括第一包覆层和第二包覆层，所述第二包覆层包括含有B、La和Al中的至少一种的化合物，所述化合物为氧化物、酸及含锂的盐中的至少一种。
任选地，所述包覆层包括第一包覆层和第二包覆层，第二包覆层包括含硼化合物。
任选地，所述包覆层包括第一包覆层和第二包覆层，第二包覆层包括含硼化合物，所述含硼化合物包括含硼的氧化物、含硼的酸及含硼和锂的盐中的至少一种。
任选地，所述包覆层包括第一包覆层和第二包覆层，第二包覆层包括含硼化合物，所述含硼化合物包括B 2O 3、H 3BO 3、Li 2O-B 2O 3、Li 3BO 3、Li 2B 4O 7、Li 2B 2O 7和Li 2B 8O 13中的至少一种。
任选地，所述M1包括Mn和/或Al。
任选地，所述M2包括在所述高镍正极材料中化合价大于等于正4价的元素。
任选地，所述M3包括在所述高镍正极材料中化合价等于正2价的元素。
任选地，所述M2和M3均包括Zr、Ti、Nb、Ce、Hf、W、Mo、Ta、Ge、Sn、Sr、Mg和Ba中的至少一种，且M2和M3不相同。
任选地，所述M4包括在所述高镍正极材料中化合价大于等于正3价的元素。
任选地，所述M4包括Al、Ti、P、Si、Nb、Y、W、Cr、Zr和La中的至少一种。
任选地，所述M5包括B、La和A中的至少一种。
任选地，所述M5包括B。
任选地，所述高镍正极材料使用AlKα射线进行粉末XPS测定：当将结合能在850eV～870eV范围内出现的Ni2P 3/2峰进行分峰和拟合后，Ni 2+/Ni 3+的面积比大于1。
任选地，所述高镍正极材料使用AlKα射线进行粉末XPS测定：当将结合能在526eV～540eV范围内出现的O1S峰进行分峰和拟合时，O1S 晶格氧/O1S 杂质氧的面积比大于1/2。
任选地，所述高镍正极材料中LiOH的质量含量小于0.3wt％。
任选地，所述高镍正极材料中Li 2CO 3的质量含量小于0.3wt％。
任选地，所述高镍正极材料的晶体结构属于六方晶型晶体结构或单斜晶型晶体结构。
任选地，所述高镍正极材料晶体颗粒形貌包括近似球形、近似立方体形和近似长方体形中的至少一种。
任选地，所述高镍正极材料的pH为：10＜pH＜12。
任选地，所述高镍正极材料的pH为：10.5＜pH＜11.7。
任选地，所述高镍正极材料的粉体电导率大于0.02S/cm。
任选地，所述高镍正极材料的比表面积为0.3m 2/g～0.8m 2/g。
任选地，所述高镍正极材料的平均粒径为2.5μm～4.5μm。
本公开还公开了一种高镍正极材料的制备方法，包括以下步骤：
将金属复合氢氧化物前驱体、含锂化合物和掺杂剂混合后进行一次热处理得到基体材料；
所述掺杂剂包括含M2元素的化合物和含M3元素的化合物，所述含M2元素的化合物为只含M2的氧化物、氢氧化物、锂金属氧化物中的至少一种，且所述M2在该化合物中的化合价大于等于正4价，所述含M3元素的化合物为只含M3的氧化物、氢氧化物中的至少一种，且所述M3在该化合物中的化合价为正2价；
将所述基体材料进行包覆得到高镍正极材料。
任选地，所述金属复合氢氧化物前驱体、含锂化合物和掺杂剂的质量比为1：(0.46～0.49)：(0.001～0.005)。
任选地，所述金属复合氢氧化物前驱体、含锂化合物和掺杂剂的质量比为1：(0.46～0.48)：(0.001～0.003)。
任选地，所述金属复合氢氧化物前驱体中金属总量Me与含锂化合物中Li的原子比为1.0＜Li/Me＜1.2。
任选地，所述含锂化合物包括含锂的盐、含锂的氢氧化物。
任选地，所述含锂化合物包括碳酸锂、氢氧化锂、硝酸锂和乙酸锂中的至少一种。
任选地，所述M2元素和M3元素均为选自Zr、Ti、Nb、Ce、Hf、W、Mo、Ta、Ge、Sn、Sr、Mg和Ba中的至少一种，且M2和M3不相同。
任选地，所述M2和M3的摩尔比n M2:n M3大于等于2：1。
任选地，所述掺杂剂的平均粒径为10nm～50nm。
任选地，所述一次热处理的温度为680℃～900℃。
任选地，所述一次热处理的时间为5h～20h。
任选地，所述一次热处理的升温速率为50℃/h～550℃/h。
任选地，所述基体材料的氧含量大于等于85％。
任选地，所述方法包括将所述基体材料与第一包覆剂混合后进行二次热处理得到一次包覆所得物的步骤。
任选地，所述方法包括：所述基体材料与第一包覆剂的质量比为1000：(0.5～3)。
任选地，所述方法包括：所述第一包覆剂包括化合价大于等于正3价的金属元素或非金属元素。
任选地，所述方法包括：第一包覆剂包括化合价大于等于正3价的金属元素或非金属元素的氧化物、盐或者氢氧化物中的至少一种。
任选地，所述方法包括：所述第一包覆剂包括化合价大于等于正3价的金属元素或非金属元素，所述金属元素或非金属元素包括Al、Ti、P、Si、Nb、Y、W、Cr、Zr或La中的至少一种。
任选地，所述方法包括：所述第一包覆剂包括是铝酸锂、钛酸锂、钛酸镧锂、氧化钇、氧化铝和氧化钛中的至少一种。
任选地，所述方法包括：所述第一包覆剂的平均粒径为10nm～50nm。
任选地，所述方法包括：所述二次热处理的温度为600℃～800℃。
任选地，所述方法包括：所述二次热处理的时间为1h～20h。
任选地，所述方法包括：所述二次热处理的升温速率为50℃/h～550℃/h。
任选地，所述方法包括：所述二次热处理后还包括在恒温条件下进行洗涤、洗涤后在真空条件下进行干燥处理的步骤，所述恒温条件的温度为10℃～25℃。
任选地，所述方法包括：所述二次热处理后还包括在恒温条件下进行洗涤、洗涤后在真空条件下进行干燥处理的步骤，所述干燥处理的温度为100℃～200℃。
任选地，所述方法包括：所述一次包覆所得物中的氧含量大于等于85％。
任选地，所述方法还包括将所述一次包覆所得物与第二包覆剂混合后进行三次热处理的步骤。
任选地，所述方法包括：所述第二包覆剂包括含有B、La和Al中的至少一种的化合物。任选地，所述方法包括：所述第二包覆剂包括含有B、La和Al中的至少一种的化合物，所述化合物为氧化物、酸，或者含锂的盐。
任选地，所述方法包括：所述第二包覆剂包括含硼化合物。
任选地，所述方法包括：所述第二包覆剂包括含硼化合物，所述含硼化合物包括含硼的氧化物、含硼的酸、或者含硼和锂的盐。
任选地，所述方法包括：所述第二包覆剂包括含硼化合物，所述含硼化合物包括B 2O 3、H 3BO 3、Li 2O-B 2O 3、Li 3BO 3、Li 2B 4O 7、Li 2B 2O 7和Li 2B 8O 13中的至少一种。
任选地，所述方法包括：所述一次包覆所得物与第二包覆剂的质量比为1：(0.0005-0.005)。
任选地，所述方法包括：所述三次热处理的温度为200℃～600℃。
任选地，所述方法包括：所述三次热处理的时间为1h～20h。
任选地，所述方法包括：所述三次热处理的升温速率为50℃/h～550℃/h。
任选地，所述金属复合氢氧化物前驱体通过将金属盐溶液和络合剂和pH调节剂混合处理得到。
任选地，所述方法包括：所述金属盐溶液和络合剂和pH调节剂的质量比为1：(0.01～0.10)：(0.1～0.8)。
任选地，所述方法包括：所述金属盐溶液包括镍的盐溶液、钴的盐溶液、锰的盐溶液和铝的盐溶液中的至少一种。
任选地，所述方法包括：所述络合剂包括氨水、硫酸铵、氯化铵、碳酸铵、氟化铵、肼、乙二胺四乙酸、次氮基三乙酸、尿嘧啶二乙酸和甘氨酸中的至少一种。
任选地，所述方法包括：所述pH调节剂包括氢氧化钠和氢氧化钾中的至少一种。
任选地，所述方法包括：所述混合处理的pH为9～13。
任选地，所述方法包括：所述混合处理的温度为10℃～80℃。
任选地，所述方法包括：所述混合处理的时间为10h～200h。
任选地，所述方法包括：所述混合处理在搅拌状态下进行，所述搅拌速率为800rpm～1200rpm。
任选地，所述方法包括：所述混合处理后还包括固液分离、洗涤和干燥的步骤。
任选地，所述方法包括：所述金属复合氢氧化物前驱体的平均粒径为3μm～10μm。
本公开还公开了一种锂离子电池，所述锂离子电池包括上述高镍正极材料或由上述方法制备的高镍正极材料。
附图说明
为了更清楚的说明本公开实施例或现有技术的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单的介绍，显而易见地，下面描述中的附图仅仅是本公开的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。同时，以下附图仅示例地表征本公开的实施方式，图中尺寸比例与实施方式的真实比例并不能直接对应，同时以下附图仅示出了本公开的某些实施方式，因此不应被看作是对范围的限定。
图1为本公开一些实施方式的高镍正极材料的制备流程图；
图2为本公开一些实施方式的高镍正极材料的SEM图；
图3为本公开实施例1的高镍正极材料在结合能为850eV～870eV的位置的Ni键合部分的峰Ni2P 3/2进行分峰和曲线拟合图；
图4为本公开实施例8的高镍正极材料在结合能为850eV～870eV的位置的Ni键合部分的峰Ni2P 3/2进行分峰和曲线拟合图；
图5为对比例1高镍正极材料在结合能为850eV～870eV的位置的Ni键合部分的峰Ni2P 3/2进行分峰和曲线拟合图；
图6为对比例2高镍正极材料在结合能为850eV～870eV的位置的Ni键合部分的峰Ni2P 3/2进行分峰和曲线拟合图；
图7为本公开实施例1的高镍正极材料在结合能为526eV～540eV的位置的O键合部分的峰O1S进行分峰和曲线拟合图；
图8为本公开实施例8的高镍正极材料在结合能为526eV～540eV的位置的O键合部分的峰O1S进行分峰和曲线拟合图；
图9为对比例1高镍正极材料在结合能为526eV～540eV的位置的O键合部分的峰O1S进行分峰和曲线拟合图；
图10为对比例2高镍正极材料在结合能为526eV～540eV的位置的O键合部分的峰O1S进行分峰和曲线拟合图；
图11为本公开实施例1的高镍正极材料的容量微分曲线图；
图12为本公开实施例8的高镍正极材料的容量微分曲线图；
图13为对比例1的高镍正极材料的容量微分曲线图；
图14为对比例2的高镍正极材料的容量微分曲线图；
图15为本公开实施例1的高镍正极材料循环300周进行氩离子切面分析SEM图；
图16为本公开实施例8的高镍正极材料循环300周进行氩离子切面分析SEM图；
图17为对比例1的高镍正极材料循环300周进行氩离子切面分析SEM图；
图18为对比例2的高镍正极材料循环300周进行氩离子切面分析SEM图；
图19为本公开实施例25的高镍正极材料循环300周进行氩离子切面分析SEM图；
图20为本公开实施例26的高镍正极材料循环300周进行氩离子切面分析SEM图；
图21为本公开对比例6的高镍正极材料循环300周进行氩离子切面分析SEM图；
图22为本公开一些实施方式提供的高镍正极材料局部的切面的结构示意图；
图23为本公开一些实施方式提供的高镍正极材料局部的切面的结构示意图；
图24为本公开一些实施方式提供的高镍正极材料局部的切面的结构示意图；
图25为本公开一些实施方式提供的高镍正极材料局部的切面的结构示意图；
图26为本公开一些实施方式提供的高镍正极材料局部的切面的结构示意图；
附图标记：100-正极材料，120-粒子，122-一次粒子，124-二次粒子，140包覆层，142-第一包覆层，144-第二包覆层；
需要说明的是，图22-26中的矩形边界线仅为示例性的说明为该高镍正极材料的局部(随机的某个视野)的切面图。
具体实施方式
为了更好的理解本公开的技术方案，下面结合附图对本公开实施方式和实施例进行详细描述。
应当明确，所描述的实施方式和实施例仅仅是本公开一部分实施方式和实施例，而不是全部的实施方式和实施例。基于本公开中的实施方式和实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其它实施方式和实施例，都属于本公开保护的范围。
此外，术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括一个或者更多个该特征。
为了容易理解本公开，特定术语在本公开中被恰当地定义。除非本文中另外定义，本公开中使用的科学术语和技术术语具有本公开所属领域中的技术人员通常理解的含义。
如本文所用的术语“基体”是指前驱体与锂盐混合后经过高温固相反应合成的锂类复合氧化物，并且包括锂和金属元素。
如本文所用，术语“一次粒子”是指单独存在而不形成凝聚体的粒子。
如本文所用，术语“二次粒子”是指上述一次粒子凝聚而成的粒子。
NCM三元正极材料可理解为LiCoO 2、LiNi 0.5Mn 0.5O 2和LiNiO 2的固溶体，其对应于通式Li 1+a[Ni z(Ni 1/2Mn 1/2) yCO x] 1-aO 2，其中Z代表Ni 3+比例；例如，LiNi 0.6Co 0.2Mn 0.2O 2可理解为0.2LiCoO 2+0.4LiNi 0.5Mn 0.5O 2+0.4LiNiO 2，因此Ni 3+比例为0.4，其他高镍材料如LiNi 0.885Co 0.09Mn 0.025O 2中的Ni 3+比例为0.86，LiNi 0.8Co 0.15Al 0.05O 2中的Ni 3+比例为0.8。对于高镍材料的合成，由于含Ni 3+比例高其合成过程需要的氧含量也高，因为只有这样才能把前驱体中的Ni 2+氧化为Ni 3+，例如LiNi 0.885Co 0.09Mn 0.025O 2和LiNi 0.8Co 0.15Al 0.05O 2必须在高浓度氧气氛围下才可以合成，而LiNi 0.4Co 0.2Mn 0.4O 2的Ni 3+比例为0，因此在空气氛围下就可以合成，并且材料表面碱性杂质很少。合成的高镍材料对空气中的水分非常敏感，这主要是因为高镍材料中Ni 3+比例较高，导致高镍材料中的锂易与空气中的水发生质子交换反应生成LiOH，而Ni 3+比例低的中低镍材料则较难发生质子交换反应，因此高镍材料的生产和保存必须在低湿度环境中。用高镍材料做成电池，电池在充电后，材料中的Ni 3+会转化成Ni 4+，Ni 4+具有的强氧化性会与直接接触的电解液发生氧化还原反应，Ni 4++电解质→Ni 2++{H 2O,CO 2}，产生气体引起电池鼓包，同时正极活性物质的损失又会引起电池容量跳水。因为高镍材料必然含有高比例的Ni 3+，而高镍材料表面层(5nm～10nm)的Ni 3+是直接与电解液或者空气接触的，所以如何控制好高镍材料表面层的Ni 3+比例，对于提升高镍材料的高温循环性能、降低材料产气、降低材料表面碱性杂质、降低直流内阻增长等具有重要意义。
因此，本公开提供了一种高镍正极材料及其制备方法、锂离子电池，本公开的高镍正极材料表面的Ni 3+数量较少、Ni 2+数量较多，能够避免高镍正极材料表面在脱锂时被氧化，从而能够提升高镍正极材料的高温循环性能和结构稳定性。
I.正极材料
本公开一实施方式提供一种高镍正极材料，该正极材料的化学通式为式(1)所示：
Li xNi 1-(a+b+c+d+e+f)Co aM1 bM2 cM3 dM4 eM5 fO 2(1)
其中，0.95≤x≤1.2，0≤a≤0.15，0≤b≤0.10，0≤c≤0.05，0≤d≤0.05，0≤e≤0.05，0≤f≤0.05，0＜a+b+c+d+e+f≤0.2。
高镍正极材料使用AlKα射线进行粉末XPS测定,当将结合能在850eV～870eV范围内出现的Ni2P 3/2峰进行分峰和拟合后，将Ni 2+的峰值面积设定为S1，Ni 3+的峰值面积设定为S2，将Ni 2+的峰半峰宽设定为α(或者用a表示，不同于上述化学通式中的a)，将Ni 3+的峰半峰宽设定为β(或者用b表示，不同于上述化学通式中的b)，S1、S2、α(a)和β(b)满足以下关系：
S1/(S1+S2)＞0.5且0.9＜α/β＜1.5(即也可表示为S1/(S1+S2)＞0.5且0.9＜a/b＜1.5)(2)。
在上述技术方案中，本公开的高镍正极材料经XPS测定满足以下关系：S1/(S1+S2)＞0.5且0.9＜α/β＜1.5，表明本公开的高镍正极材料表面的Ni 3+数量较少，表面Ni 2+数量较多，能够避免高镍正极材料表面在脱锂时被氧化，有利于维持正极材料结构的稳定性，从而避免了正极活性材料和电解液在充放电过程中的损失，进一步提高正极材料的容量，使得高镍正极材料的高温循环性能得到明显改善。此外，由于材料表面的Ni 3+数量较少，表面Ni 2+数量较多，能够减小材料在充放电过程中发生内部裂纹，使得材料内部结构稳定，使得本公开的正极材料应用于电池中进行长期循环时，电池的直流内阻增长得到明显的抑制。
(1)正极材料的结构
在一些实施方式中，正极材料100包括：粒子120；包覆层140；该包覆层140形成于粒子120的表面。
在一些实施方式中，粒子120包括二次粒子124和/或一次粒子122，一次粒子122的至少部分表面包覆有包覆层140，二次粒子124包括多个带有包覆层140的一次粒子122。
在一些实施方式中，正极材料100包括二次粒子124和/或一次粒子122，一次粒子122的至少部分表面包覆有包覆层140，二次粒子124包括多个带有包覆层140的一次粒子122。可以理解的是，二次粒子124为多个一次粒子122的凝聚体，本公开的正极材料100可以仅包括一次粒子122，或仅包括二次粒子124，还可以是一次粒子122和二次粒子124的混合物。
在一些实施方式中，参照附图22，包覆层140包括第一包覆层142和第二包覆层144，第一包覆层142形成于一次粒子122的表面，第二包覆层144形成于第一包覆层142的表面。在一些实施方式中，参照附图25，仅第一包覆层142形成于一次粒子122的表面。在一些实施方式中，参照附图26，仅第二包覆层144形成于一次粒子122的表面。第一包覆层142可以提高材料表面结构的稳定性，第二包覆层144可以有效改善材料的加工性能和导电性能。
参照附图23，在一些实施方式中，正极材料100包括：一次粒子122；二次粒子124；包覆层140，该包覆层包括第一包覆层142和第二包覆层144；第一包覆层142形成于一次粒子122的表面，第二包覆层144形成于第一包覆层142的表面；二次颗粒包括多个带有包覆层140的一次粒子122。
在一些实施方式中，正极材料100包括：二次粒子124，该二次粒子124包括多个一次粒子122；一次粒子122的表面包覆有包覆层140。
参照附图24，在一些实施方式中，正极材料100包括：二次粒子124，该二次粒子124包括多个一次粒子122；该一次粒子122的表面包覆有包覆层140；包覆层140包括第一包覆层142和第二包覆层144；第一包覆层142形成于一次粒子122的表面，第二包覆层144形成于第一包覆层142的表面。
(2)正极材料中的组分
在一些实施方式中，第一包覆层142包括在高镍正极材料100中化合价大于等于正3价的元素。
在一些实施方式中，第一包覆层142包括Al、Ti、P、Si、Nb、Y、W、Cr、Zr和La中的至少一种。上述元素在高镍正极材料100中的化合价大于等于正3价，使得高镍正极材料100表面层的Ni 2+数量不变或者进一步增加，提高正极材料100结构的稳定性，同时也减小了材料表面的碱性杂质的生成，可以理解的，上述高镍正极材料100表面指的是一次粒子122表面5nm～10nm的厚度。
在一些实施方式中，所述包覆层包括第一包覆层和第二包覆层，所述第一包覆层包括含有Al、Ti、P、Si、Nb、Y、W、Cr、Zr和La中的至少一种的化合物。
在一些实施方式中，所述包覆层包括第一包覆层和第二包覆层，所述第一包覆层包括含有Al、Ti、P、Si、Nb、Y、W、Cr、Zr和La中的至少一种的化合物，所述化合物为氧化物、氢氧化物或盐中的至少一种。
在一些实施方式中，第二包覆层144包括含有B、La和Al中的至少一种化合物。
在一些实施方式中，第二包覆层144包括含有B、La和Al中的至少一种化合物，该化合物为氧化物、酸及含锂的盐中的至少一种。
在一些实施方式中，第二包覆层144包括含硼化合物，含硼化合物包括含硼的氧化物、含硼的酸及含硼和锂的盐中的至少一种。
可选地，含硼的氧化物包括但不限于B 2O 3、B 2O等。
可选地，含硼的酸包括但不限于H 3BO 3。
可选地，含硼和锂的盐包括但不限于Li iB jO k，其中2≤i≤3，1≤j≤8，3≤k≤13。可选地，含硼和锂的盐包括但不限于B 2O 3、H 3BO 3、Li 2O-B 2O 3、Li 3BO 3、Li 2B 4O 7、Li 2B 2O 7和Li 2B 8O 13中的至少一种。
在一些实施方式中，第二包覆层144包括含铝化合物，含铝化合物包括含铝的氧化物、或者含硼和锂的盐。可选地，含铝的氧化物包括但不限于Al 2O 3。可选地，含硼和锂的盐包括但不限于Li 3BO 3。
在一些实施方式中，第二包覆层144包括含硼化合物，含硼化合物包括B 2O 3、H 3BO 3、Li 2O-B 2O 3、Li 3BO 3、Li 2B 4O 7、Li 2B 2O 7和Li 2B 8O 13中的至少一种。上述含硼化合物可以不但可以和高镍正极材料100表面的碱性杂质发生化学反应，避免了材料表面的碱性杂质中的Li 2CO 3分解或碱性杂质与电解液发生副反应产生气体，而且，含硼化合物覆盖在高镍正极材料100表面形成稳定的包覆层，能够提高高镍正极材料100的稳定性。
在一些实施方式中，M1包括Mn和/或Al。在一些实施方式中，M1可以是Mn，还可以Al，还可以是Mn和Al的混合。
在一些实施方式中，M2包括在所述高镍正极材料中化合价大于等于正4价的元素。
在一些实施方式中，M3包括在所述高镍正极材料中化合价等于正2价的元素。
在一些实施方式中，M2和M3各自包括Zr、Ti、Nb、Ce、Hf、W、Mo、Ta、Ge、Sn、Sr、Mg和Ba中的至少一种，且M2和M3不相同。
在一些实施方式中，M4包括在所述高镍正极材料中化合价大于等于正3价的元素。
在一些实施方式中，M4包括Al、Ti、P、Si、Nb、Y、W、Cr、Zr和La中的至少一种。
在一些实施方式中，M5包括B、La和A中的至少一种。
在一些实施方式中，M5包括B。
(3)正极材料的特征和特性
在一些实施方式中，高镍正极材料100使用AlKα射线进行粉末XPS测定：当将结合能在850eV～870eV范围内出现的Ni2P 3/2峰进行分峰和拟合后，且拟合的标准差∑x 2＜10％，Ni 2+/Ni 3+的峰面积比＞1。可选地，Ni 2+/Ni 3+的峰面积比可以为2、3、4和5等，表明本公开的高镍材料表面层的Ni 2+较多，能够避免高镍正极材料100表面在脱锂时被氧化，有利于维持正极材料100结构的稳定性。
在一些实施方式中，高镍正极材料100使用AlKα射线进行粉末XPS测定，当将结合能在526eV～540eV范围内出现的O1S峰进行分峰和拟合时，且拟合的标准差∑x 2＜10％，O1S 晶格氧/O1S 杂质氧的面积比＞1/2。杂质氧指的是LiOH、Li 2CO 3和Li 2SO 4等化合物中的氧，可选地，O1S 晶格氧/O1S 杂质氧的面积可以是0.532、0.525和0.573、0.58、0.59等，将O1S 晶格氧/O1S 杂质氧的面积比控制在上述范围内，有利于降低高镍正极材料100表面的碱性杂质(Li 2CO 3和LiOH等)，降低高镍正极材料100制备的电池的产气量。
在一些实施方式中，高镍正极材料100的表面碱性杂质主要指Li 2CO 3和LiOH，高镍正极材料100中Li 2CO 3的质量含量小于0.3wt％。例如，高镍正极材料100中Li 2CO 3的质量含量可以为0.05wt％、0.1wt％、0.12wt％和0.2wt％等，当然也可以是上述范围内的其他值，在此不做限定。在一些典型的实施方式中，高镍正极材料100中Li 2CO 3的质量含量小于0.13wt％。
在一些实施方式中，高镍正极材料100中LiOH的质量含量小于0.3wt％。例如，高镍正极材料100中LiOH的质量含量可以为0.05wt％、0.08wt％、0.1wt％和0.2wt％等，当然也可以是上述范围内的其他值，在此不做限定。在一些典型的实施方式中，高镍正极材料100中LiOH的质量含量小于0.1wt％。
将Li 2CO 3和LiOH在高镍正极材料100中的质量含量控制在上述范围内，有利于提高高镍正极材料100的加工性能和减少高镍正极材料100制备的电池的产气。
在一些实施方式中，高镍正极材料100的晶体结构属于六方晶型晶体结构或单斜晶型晶体结构。
六方晶型的晶体结构属于选自由P3、P31、P32、R3、P-3、R-3、P312、P321、P3112、P3121、P3212、P3221、R32、P3m1、P31m、P3c1、P31c、R3m、R3c、P-31m、P-31c、P-3m1、P-3c1、R-3m、R-3c、P6、P61、P65、P62、P64、P63、P-6、P6/m、P63/m、P622、P6122、P6522、P6222、P6422、P6322、P6mm、P6cc、P63cm、P63mc、P-6m2、P-6c2、P-62m、P-62c、P6/mmm、P6/mcc、P63/mcm和P63/mmc构成的组中的任一空间群。
单斜晶型的晶体结构属于选自由P2、P21、C2、Pm、Pc、Cm、Cc、P2/m、P21/m、C2/m、P2/c、P21/c和C2/c构成的组中的任一空间群。
在一些典型的实施方式中，为了获得放电容量较高的二次电池，高镍正极材料100的晶体结构属于空间群R-3m的六方晶型晶体结构或者属于C2/m的单斜晶型晶体结构。
在一些实施方式中，高镍正极材料100晶体颗粒形貌包括近似球形、近似立方体形和近似长方体形中的至少一种。
在一些实施方式中，高镍正极材料100的pH为：10＜pH＜12。在一些实施方式中，高镍正极材料100的pH为：10.5＜pH＜11.7。在一些实施方式中，高镍正极材料100的pH可以是例如11.1＜pH＜11.9、10.5＜pH＜11.0或11.0＜pH＜11.7，诸如10.6、10.8、11.0、11.2、11.3和11.5等，当然也可以是上述范围内的其他值，在此不做限定。将高镍正极材料100的pH控制在上述范围内，有利于进一步提升高镍正极材料100的加工性能，诸如提升正极材料在制备电池过程中的稳定性，在和黏结剂混合是不易产生沉降或者掉粉。在一些典型的实施方式中，高镍正极材料100的pH为：11.0＜pH＜11.5。在又一些典型的实施方式中，高镍正极材料100的pH为11.2＜pH＜11.3。
在一些实施方式中，高镍正极材料100的粉体电导率大于0.02S/cm。在一些实施方式中，高镍正极材料100的粉体电导率具体可以是例如0.03S/cm-0.08S/cm、0.05S/cm-0.08S/cm或0.03S/cm-0.05S/cm，诸如0.03S/cm、0.04S/cm、0.05S/cm、0.06S/cm和0.07S/cm等，当然也可以是上述范围内的其他值，在此不做限定。
在一些实施方式中，高镍正极材料100的比表面积为0.3m 2/g～0.8m 2/g。在一些实施方式中，高镍正极材料100的比表面积具体可以是例如0.3m 2/g～0.5m 2/g、0.5m 2/g～0.8m 2/g或0.4m 2/g～0.7m 2/g，诸如0.3m 2/、0.4m 2/、0.5m 2/、0.6m 2/、0.7m 2/和0.8m 2/等，当然也可以是上述范围内的其他值，在此不做限定。本公开的正极材料100的比表面积在上述范围内，可以进一步提升材料的稳定性和电化学性能，避免因比表面积过大而在制备过程中产生掉粉、或者产气等问题，同时避免因比表面积过小而导致电池的容量和倍率下降等问题。
在一些实施方式中，高镍正极材料100的中值粒径为2.5μm～4.5μm。在一些实施方式中，高镍正极材料100的中值粒径可以是例如3.0μm～4.5μm、2.5μm～4.0μm或3.0μm～4.0μm，诸如2.5μm、3μm、3.5μm、4μm和4.5μm等，将高镍正极材料100的平均粒径控制在上述范围内，有利于高镍正极材料100作为正极极片的压实密度、粉体电导率和循环寿命的提升。
II.正极材料的制备
本公开一实施方式还提供一种高镍正极材料的制备方法，包括以下步骤：
步骤S100、将金属复合氢氧化物前驱体、含锂化合物和掺杂剂混合后进行一次热处理得到基体材料；上述掺杂剂包括M2元素和M3元素，M2元素对应的化合物为只含M2的氧化物、氢氧化物和锂金属氧化物中的至少一种，且M2在该化合物中的化合价大于等于正4价，M3元素对应的化合物为只含M3的氧化物和氢氧化物中的至少一种，且M3在该化合物中的化合价为正2价；
步骤S200、将步骤S100得到的基体材料进行包覆得到高镍正极材料。
在上述技术方案中，本公开含有M2元素和M3元素的掺杂剂中，M2的元素迁移能力较差，M3的离子迁移能力较强，本公开将含有M2元素和M3元素的掺杂剂与金属复合氢氧化物前驱体、含锂化合物经过一次热处理后，使得M2元素掺杂在材料的表面，M2元素主要富集在材料的晶界处，M3元素掺杂在材料的晶体内部，由于化合价大于等于正4价的M2元素存在于材料的表面，通过化合价平衡使得材料表面的Ni 3+数量减少，同时表面Ni 2+数量增加，避免正极材料表面在脱锂时被氧化，有利于维持正极材料结构的稳定性；化合价等于正2价的M3元素进入材料内部，可以抑制材料充放电过程中H2→H3的相转变，提高结构稳定性，同时M3可以取代材料内部晶格中一部分的Li +的位置，但是不影响材料的层状结构，本公开通过将含有M2元素和M3元素掺杂形成基体材料，可以提升高镍正极材料的稳定性，进一步提升高镍正极材料的容量性能。以下结合实施方式和实施例具体介绍本公开的制备方法：
在步骤S100之前，制备金属复合氢氧化物前驱体，包括：采用共沉淀法，将金属盐溶液和络合剂和pH调节剂混合处理得到金属复合氢氧化物前驱体。
在一些实施方式中，金属盐溶液、络合剂和pH调节剂的质量比为1：(0.01～0.10)：(0.1～0.8)。在一些实施方式中，金属盐溶液、络合剂和pH调节剂的质量比具体可以是例如1：(0.05～0.10)：(0.1～0.8)、1：(0.01～0.10)：(0.4～0.8)、1：(0.05～0.10)：(0.1～0.5)，诸如1：0.01：0.1、1：0.05：0.3、1：0.1：1.5和1：0.08：0.8等。本公开的金属盐溶液、络合剂和pH调节剂的质量比在上述范围内，可以促进一次颗粒的有序生长(即晶体的径向生长)，有利于将材料颗粒的大小限定在一定范围内，有利于提高材料的振实密度、粒度分布，保证颗粒不破裂。
在一些实施方式中，金属盐溶液包括镍的盐溶液、钴的盐溶液、锰的盐溶液和铝的盐溶液中的至少一种。
在一些实施方式中，镍的盐溶液包括硫酸镍、氯化镍、氨基磺酸镍、溴化镍、氢氧化亚镍和羰基镍中的至少一种。
在一些实施方式中，钴的盐溶液包括硫酸钴、氯化钴和硝酸钴中的至少一种。
在一些实施方式中，锰的盐溶液包括硫酸锰、硝酸锰和氯化锰中的至少一种。
在一些实施方式中，铝的盐溶液包括偏铝酸钠、硫酸铝、氯化铝和偏铝酸钾中的至少一种。
在一些实施方式中，络合剂选择能够在水溶液中与镍、钴、锰或铝的离子形成络合物即可。在一些实施方式中，络合剂包括铵离子供给体、肼、乙二胺四乙酸、次氮基三乙酸、尿嘧啶二乙酸和甘氨酸中的至少一种，铵离子供给体包括氨水、硫酸铵、氯化铵、碳酸铵和氟化铵中的至少一种。
在一些实施方式中，混合处理的温度为10℃～80℃。在一些实施方式中，混合处理的温度为例如10℃～50℃、40℃～80℃或20℃～60℃，诸如10℃、20℃、30℃、40℃、50℃、60℃、70℃和80℃等，当然也可以是上述范围内的其他值，在此不做限定。在一些典型的实施方式中，混合处理的温度为20℃～70℃。将共沉淀法反应的温度控制在上述范围内，有利于前驱体晶粒的生长。
在一些实施方式中，pH调节剂包括碱金属氢氧化物。
在一些实施方式中，碱金属氧化物包括氢氧化钠和氢氧化钾中的至少一种。
在一些实施方式中，混合处理的pH为9～13。在一些实施方式中，混合处理的pH为例如9～12、10～13或10～12，诸如9、10、11、12和13等，当然也可以是上述范围内的其他值，在此不做限定。在一些典型的实施方式中，混合处理的pH为11～13。
在一些实施方式中，混合处理的时间为10h～200h。在一些实施方式中，混合处理的具体时间可以是例如50h～200h、 10h～150h或50h～150h，诸如10h、20h、30h、40h、50h、60h、70h、80h、90h、100h、110h、120h、130h、140h、150h、160h、180h、180h、190h和200h等，当然也可以是上述范围内的其他值，在此不做限定。
在一些实施方式中，混合处理在搅拌状态下进行，搅拌速率为800rpm～1200rpm。在一些实施方式中，搅拌速率具体可以是例如1000rpm～1200rpm、800rpm～1000rpm或900rpm～1100rpm，诸如800rpm、900rpm、1000rpm、1100rpm和1200rpm等，当然也可以是上述范围内的其他值，在此不做限定。
在一些实施方式中，混合处理在反应槽中进行，反应槽为使形成的金属复合氢氧化物分离而使之溢流的连续式、直至反应结束为止不向系统外排出的间歇式中至少一种。
在一些实施方式中，混合处理制备的金属复合氢氧化物前驱体为浆料状的悬浊物，经固液分离、洗涤、干燥得到金属复合氢氧化物前驱体。
在一些实施方式中，固液分离的方式包括离心和过滤中的任意一种，固液分离的目的是将金属复合氢氧化物从溶剂中分离出来。
在一些实施方式中，洗涤采用去离子水多次洗涤去除杂质。
在一些实施方式中，干燥的温度为100℃～130℃。在一些实施方式中，干燥的温度可以是例如100℃～120℃、110℃～130℃或110℃～120℃，诸如100℃、110℃、120℃和130℃等，当然也可以是上述范围内的其他值，在此不做限定。
在一些实施方式中，干燥的时间为12h～24h。干燥的时间具体可以是例如15h～24h、12h～20h或15h～20h，诸如12h、13h、14h、15h、16h、17h、18h、19h、20h、21h、22h、23h和24h等，当然也可以是上述范围内的其他值，在此不做限定。
在一些实施方式中，金属复合氢氧化物前驱体的平均粒径为3μm～10μm。在一些实施方式中，金属复合氢氧化物前驱体的中值粒径可以是例如5μm～10μm、3μm～8μm或5μm～9μm，诸如3μm、4μm、5μm、6μm、7μm、8μm、9μm和10μm等，当然也可以是上述范围内的其他值，在此不做限定。
步骤S100、将金属复合氢氧化物前驱体、含锂化合物和掺杂剂混合后进行一次热处理得到基体材料，掺杂剂包括含有M2元素和M3元素的化合物，M2元素对应的化合物为只含M2的氧化物、氢氧化物和锂金属氧化物中的至少一种，且M2元素在该化合物中的化合价大于等于正4价，M3元素对应的化合物为只含M3的氧化物和氢氧化物中的至少一种，且M3元素在该化合物中的化合价为正2价。
在上述步骤中，将掺杂剂加入进行一次热处理，使得化合价大于等于正4价的M2元素主要掺杂在材料表面、化合价为正2价的M3元素主要进入材料内部，可以理解的，通过一次热处理后，M3元素可以直接进入晶体内部取代部分Li的位点，M2元素主要富集在材料的晶界处，少部分的M2元素在M3元素的诱导下进入晶体内部，少量取代晶体内部的元素位点。
在一些实施方式中，金属复合氢氧化物前驱体、含锂化合物和掺杂剂的质量比为1：(0.46～0.49)：(0.001～0.005)。在一些实施方式中，金属复合氢氧化物前驱体、含锂化合物和掺杂剂的质量比可以是例如1：(0.46～0.48)：(0.001～0.003)、1：(0.46～0.47)：(0.001～0.002)或1：(0.45～0.47)：(0.002～0.003)，诸如1：0.46：0.002、1：0.47：0.003、1：0.48：0.001、1：0.047：0.002和1：0.048：0.01等，当然也可以是上述范围内的其他值，在此不做限定。本公开的金属复合氢氧化物前驱体、含锂化合物和掺杂剂的质量比在上述范围内，可以进一步提高材料的放电容量和倍率容量，使得材料保持较高的容量保持率和较低的DCR增长率；金属复合氢氧化物前驱体和含锂化合物的质量比偏低则会影响材料放电容量，倍率容量，金属复合氢氧化物前驱体和含锂化合物的质量比偏高，会导致材料表面残碱偏高，容量降低，成本升高。
在一些实施方式中，金属复合氢氧化物前驱体中金属Me与含锂化合物中Li的原子比为1.0＜Li/Me＜1.2。在一些实施方式中，Li/Me可以是1.01、1.05、1.1、1.15和1.19等，Me表示金属复合氢氧化物前驱体中所有金属的原子数量之和，将金属复合氢氧化物前驱体中金属Me与含锂化合物中Li的原子比控制在上述范围内，有利于基体材料晶粒的形成和材料电化学性能的提升。
在一些实施方式中，含锂化合物包括含锂的盐、含锂的氢氧化物。在一些实施方式中，含锂化合物包括碳酸锂、氢氧化锂、硝酸锂和乙酸锂中的至少一种。
在一些实施方式中，M2和M3元素各自均包括Zr、Ti、Nb、Ce、Hf、W、Mo、Ta、Ge、Sn、Sr、Mg和Ba中的至少一种，且M2和M3不相同。在一些实施方式中，掺杂剂包括锆酸锂、钛酸锂、氧化铌、钨酸锂、氧化钡和氢氧化镁中的至少一种。
在一些实施方式中，M2元素和M3元素的摩尔比n M2:n M3大于等于2：1。在一些实施方式中，n M2:n M3可以是例如(2-6)：1、(2-5)：1或(3-5)：1，诸如2：1、3：1、4：1、5：1和6：1等，在上述限定范围内高价元素(化合价大于等于正4价的M2元素)可以有效的掺杂在材料表面层，而低价元素(化合价为正2价的M3元素)只需少量加入量就可以进入材料内部，添加低价元素过多会抑制材料的电化学性能。在一些实施方式中，掺杂剂中M2元素和M3元素的摩尔比3：1≤n M2:n M3≤5：1。
在一些实施方式中，掺杂剂的平均粒径为10nm～50nm。在一些实施方式中，掺杂剂的平均粒径具体可以是例如10nm～40nm、20nm～50nm或20nm～40nm，诸如10nm、20nm、30nm、40nm和50nm等，当然也可以是上述范围内的其他值，在此不做限定。
在一些实施方式中，一次热处理的温度为680℃～900℃。在一些实施方式中，一次热处理的温度为例如700℃～900℃、680℃～800℃或700℃～800℃，诸如680℃、700℃、720℃、750℃、780℃、800℃、820℃、850℃和900℃等，当然也可以是上述范围内的其他值，在此不做限定。在一些典型的实施方式中，一次热处理的温度为780℃～870℃。将一次热处理的温度控制在上述范围内，有利于高镍正极材料的晶粒生长。
在一些实施方式中，一次热处理的时间为5h～20h。在一些实施方式中，一次热处理的时间为例如5h～15h、10h～20h或10h～18h，诸如5h、6h、7h、8h、9h、10h、11h、12h、13h、14h、15h、16h、18h、18h、19h和20h等，当然也可以是上述范围内的其他值，在此不做限定。在一些典型的实施方式中，一次热处理的时间为8h～15h。
在一些实施方式中，一次热处理的升温速率为50℃/h～550℃/h。在一些实施方式中，一次热处理的升温速率为例如100℃/h～550℃/h、150℃/h～500℃/h或200℃/h～300℃/h，诸如50℃/h、100℃/h、140℃/h、200℃/h、250℃/h、300℃/h、 380℃/h、400℃/h、450℃/h、500℃/h和550℃/h等，当然也可以是上述范围内的其他值，在此不做限定。在一些典型的实施方式中，一次热处理的升温速率为100℃/h～400℃/h。在又一些典型的实施方式中，一次热处理的升温速率为140℃/h～380℃/h。
在一些实施方式中，基体材料的氧含量大于等于85％。在一些实施方式中，基体材料中的氧含量可以是例如85％～98％、85％～95％或89％～97％，诸如85％、86％、87％、88％、89％、90％、91％、92％、93％、94％、95％、96％、97％等，当然也可以是上述范围内的其他值，在此不做限定。在一些典型的实施方式中，基体材料的氧含量大于等于95％。
在一些实施方式中，一次热处理的设备包括静置式的箱式炉或辊道窑式连续炉。
步骤S200、将步骤S100得到的基体材料进行包覆得到高镍正极材料。
步骤201、将基体材料与第一包覆剂混合后进行二次热处理得到一次包覆所得物。
在一些实施方式中，基体材料与第一包覆剂的质量比为1000：(0.5～3)。在一些实施方式中，基体材料与第一包覆剂的质量具体可以是例如1000：(1～3)、1000：(1.5～3)或1000：(2.5～3)，诸如1000：0.5、1000：1、1000：1.5、1000：2、1000：2.5和1000：3等，当然也可以是上述范围内的其他值，在此不做限定。
在一些实施方式中，第一包覆剂包括化合价大于等于正3价的金属元素或非金属元素，本公开加入化合价大于等于正3价的金属元素或非金属元素，通过化合价平衡使得高镍正极材料表面的Ni 2+数量不变或者进一步增加，提高了材料结构的稳定性，避免了材料与空气中的水分接触生成碱性杂质，减少了材料的产气。
在一些实施方式中，第一包覆剂包括化合价大于等于正3价的金属元素或非金属元素的氧化物、盐或者氢氧化物中的至少一种。
在一些实施方式中，金属元素或非金属元素包括Al、Ti、P、Si、Nb、Y、W、Cr、Zr或La中的至少一种。
在一些实施方式中，第一包覆剂可以是铝酸锂、钛酸锂、钛酸镧锂、氧化钇、氧化铝和氧化钛中的至少一种。
在一些实施方式中，二次热处理的温度为600℃～800℃。在一些实施方式中，二次热处理的温度为例如650℃～800℃、600℃～750℃或700℃～800℃，诸如600℃、650℃、680℃、700℃、720℃、750℃、780℃和800℃等，当然也可以是上述范围内的其他值，在此不做限定。在一些典型的实施方式中，二次热处理的温度为650℃～750℃。
在一些实施方式中，二次热处理的时间为1h～20h。在一些实施方式中，二次热处理的时间为例如5h～20h、10h～20h或5h～10h，诸如1h、2h、3h、4h、5h、6h、7h、8h、9h、10h、11h、12h、13h、14h、15h、16h、18h、18h、19h和20h等，当然也可以是上述范围内的其他值，在此不做限定。在一些典型的实施方式中，二次热处理的时间为3h～10h。
在一些实施方式中，二次热处理的升温速率为50℃/h～550℃/h。在一些实施方式中，二次热处理的升温速率为例如100℃/h～550℃/h、50℃/h～500℃/h或150℃/h～450℃/h，诸如50℃/h、100℃/h、140℃/h、200℃/h、250℃/h、300℃/h、380℃/h、400℃/h、450℃/h、500℃/h和550℃/h等，当然也可以是上述范围内的其他值，在此不做限定。在一些典型的实施方式中，二次热处理的升温速率为100℃/h～400℃/h。在又一些典型的实施方式中，二次热处理的升温速率为140℃/h～380℃/h。
在一些实施方式中，一次包覆所得物中的氧含量大于等于85％。在一些实施方式中，一次包覆所得物中的氧含量可以是例如85％～95％、90％～97％或89％～97％，诸如85％、86％、87％、88％、89％、90％、91％、92％、93％、94％、95％、96％和97％等，当然也可以是上述范围内的其他值，在此不做限定。在一些典型的实施方式中，一次包覆所得物中的氧含量大于等于95％。
在一些实施方式中，二次热处理的设备包括静置式的箱式炉或辊道窑式连续炉。
在一些实施方式中，将基体材料与第一包覆剂混合后进行二次热处理后在恒温条件下进行洗涤，洗涤后在真空条件下进行干燥处理，即得一次包覆物。
在一些实施方式中，恒温条件的温度为10℃～25℃。在一些实施方式中，恒温条件的温度可以是例如15℃～25℃、10℃～20℃或15℃～20℃，诸如10℃、11℃、12℃、13℃、14℃、15℃、16℃、17℃、18℃、19℃、20℃、21℃、22℃、23℃、24℃和25℃等，当然也可以是上述范围内的其他值，在此不做限定。
在一些实施方式中，干燥的温度为100℃～200℃。在一些实施方式中，干燥的温度具体可以是120℃～200℃、150℃～200℃或100℃～150℃，诸如100℃、110℃、120℃、130℃、140℃、150℃、160℃、170℃、180℃、190℃和200℃等，当然也可以是上述范围内的其他值，在此不做限定。
步骤S202、将一次包覆所得物与第二包覆剂混合后进行三次热处理得到高镍正极材料。
在一些实施方式中，第二包覆层144包括含有B、La和Al中的至少一种的化合物。
在一些实施方式中，第二包覆层144包括含有B、La和Al中的至少一种的化合物，该化合物为氧化物、酸，或者含锂的盐。
在一些实施方式中，第二包覆层144包括含硼化合物，含硼化合物包括含硼的氧化物、含硼的酸、或者含硼和锂的盐。
在一些实施方式中，第二包覆层144包括含硼化合物，含硼化合物包括含硼的氧化物、含硼的酸、含硼和锂的盐。
可选地，含硼的氧化物包括但不限于B 2O 3或B 2O等。
可选地，含硼的酸包括但不限于H 3BO 3。
可选地，含硼和锂的盐包括但不限于Li iB jO k，其中2≤i≤3，1≤j≤8，3≤k≤13。可选地，含硼和锂的盐包括但不限于B 2O 3、H 3BO 3、Li 2O-B 2O 3、Li 3BO 3、Li 2B 4O 7、Li 2B 2O 7和Li 2B 8O 13中的至少一种。
在一些实施方式中，第二包覆剂为含硼化合物，含硼化合物包括B 2O 3、H 3BO 3、Li 2O-B 2O 3、Li 3BO 3、Li 2B 4O 7、Li 2B 2O 7和Li 2B 8O 13中的至少一种，通过在一次包覆所得物中加入含硼化合物，上述含硼化合物可以不但可以和材料表面的碱性杂质发生化学反应而且可以覆盖在材料表面形成稳定包覆层，不但减少材料表面碱性杂质而且保护材料表面，减少材料表面碱性杂质中的Li 2CO 3分解产气，减少材料表面碱性杂质与电解液发生副反应产气。
在一些实施方式中，一次包覆所得物与第二包覆剂的质量比为1：(0.0005-0.005)。在一些实施方式中，一次包覆所得物与第二包覆剂的质量比可以是例如1:(0.0008-0.003)、1:(0.001-0.0025)或1:(0.0015-0.002)，诸如1：0.0005、1：0.0007、1：0.0009、1：0.001和1：0.0015、1：0.002、1：0.0025、1：0.003等，当然也可以是上述范围内的其他值，在 此不做限定。
在一些实施方式中，三次热处理的温度为200℃～400℃。在一些实施方式中，三次热处理的温度为例如200℃～300℃、300℃～400℃或250℃～350℃，诸如200℃、250℃、280℃、300℃、320℃、360℃、380℃和400℃等，当然也可以是上述范围内的其他值，在此不做限定。在典型的实施方式中，三次热处理的温度为250℃～360℃。
在一些实施方式中，三次热处理的时间为1h～20h。在一些实施方式中，三次热处理的时间为例如5h～20h、1h～15h或4h～16h，诸如1h、2h、3h、4h、5h、6h、7h、8h、9h、10h、11h、12h、13h、14h、15h、16h、18h、18h、19h和20h等，当然也可以是上述范围内的其他值，在此不做限定。在一些典型的实施方式中，三次热处理的时间为5h～10h。
在一些实施方式中，三次热处理的升温速率为50℃/h～550℃/h。在一些实施方式中，三次热处理的升温速率为例如200℃/h～550℃/h、50℃/h～350℃/h或200℃/h～300℃/h，诸如50℃/h、100℃/h、140℃/h、200℃/h、250℃/h、300℃/h、380℃/h、400℃/h、450℃/h、500℃/h和550℃/h等，当然也可以是上述范围内的其他值，在此不做限定。在典型的实施方式中，三次热处理的升温速率为100℃/h～400℃/h。在又一些典型的实施方式中，三次热处理的升温速率为140℃/h～380℃/h。
在一些实施方式中，高镍正极材料的氧含量大于等于85％，在一些实施方式中，高镍正极材料的氧含量可以是例如85％～98％、85％～95％或89％～97％，诸如85％、86％、87％、88％、89％、90％、91％、92％、93％、94％、95％、96％和97％等，当然也可以是上述范围内的其他值，在此不做限定。在一些典型的实施方式中，高镍正极材料的氧含量大于等于95％。
在一些实施方式中，三次热处理的设备包括静置式的箱式炉或辊道窑式连续炉。
在一些实施方式中，三次热处理还包括筛分和除磁的步骤。
在一些实施方式中，筛分的目的为200目～400目。在一些实施方式中，筛分的目数可以是例如300目～400目、200目～300目或240目～360目，诸如200目、210目、250目、280目、300目、350目、380目和400目等，当然也可以是上述范围内的其他值，在此不做限定。
III.电池
本公开一实施方式还提供一种锂离子二次电池，包括正极极片、负极极片、隔膜、非水电解液和外壳。在一些实施方式中，所述正极极片包括集流体和涂覆在所述集流体上的如上述高镍正极材料或如上述高镍正极材料的制备方法制备的正极材料。
本公开与现有技术相比，具备如下有益效果：本公开的高镍正极材料使用AlKα射线进行粉末XPS测定,当将结合能在850eV～870eV范围内出现的Ni2P 3/2峰进行分峰和拟合后，Ni 2+的峰值面积S1、Ni 3+的峰值面积S2、Ni 2+的峰半峰宽α及Ni 3+的峰半峰宽β满足：S1/(S1+S2)＞0.5且0.9＜α/β＜1.5，表明本公开的高镍正极材料表面的Ni 3+数量较少、Ni 2+数量较多，还能够避免高镍正极材料表面在脱锂时被氧化，有利于维持正极材料结构的稳定性，从而避免了正极活性材料和电解液在充放电过程中的损失，进一步提高正极材料的容量，使得高镍正极材料的高温循环性能得到明显改善。此外，由于材料表面的Ni 3+数量较少，表面Ni 2+数量较多，能够减小材料在充放电过程中发生内部裂纹，使得材料内部结构稳定，使得本公开的正极材料应用于电池中进行长期循环时，电池的直流内阻增长得到明显的抑制。
本公开通过将含有化合价大于等于正4价的M2元素和化合价等于正2价的M3元素的掺杂剂经过一次热处理后，使得M2元素掺杂在材料的表面，M3元素掺杂在材料的内部，由于化合价大于等于正4价的M2元素存在于材料的表面，通过化合价平衡使得材料表面的Ni 3+数量减少，同时表面Ni 2+数量增加，避免正极材料表面在脱锂时被氧化，有利于维持正极材料结构的稳定性；化合价等于正2价的M3元素进入材料内部，可以抑制材料充放电过程中H2→H3的相转变，提高结构稳定性，同时M3可以取代材料内部晶格中一部分的Li +的位置，但是不影响材料的层状结构，本公开通过将含有M2元素和M3元素掺杂形成基体材料，可以提高高镍正极材料的稳定性，进一步提升高镍正极材料的容量性能。
对本公开的实施例进行说明，本公开只要未超出其主旨，并不限定于这些例子。
实施例
实施例1
(1)采用共沉淀法制备Ni 0.885Co 0.09Mn 0.025(OH) 2前驱体，将Ni 0.885Co 0.09Mn 0.025(OH) 2前驱体、LiOH·H O和掺杂剂纳米TiO 2、ZrO 2、MgO混合均匀，其中(n TiO2+n ZrO2):n MgO＝3：1，然后在830℃下进行第一次热处理制备得到基体材料，其中，Li/Me＝1.05，Me＝(Ni、Co和Mn)(其中，M表示“金属复合氢氧化物前驱体中金属)；
(2)将步骤(1)制备的基体材料和纳米Al 2O 3按照质量比1：0.002混合均匀，然后在700℃下进行二次热处理，二次热处理所得料投入蒸馏水中并在保持温度25℃的同时用水洗涤，在脱水工序后，将混合物在150℃的真空气氛下干燥得到一次包覆所得物。
(3)将一次包覆所得物和H 3BO 3(即第二包覆剂)按照质量比1：0.001混合均匀，在300℃下进行第三次热处理，再经过筛分和除磁得到高镍正极材料。
在本实施例的正极材料100的结构示意图如19所示，第一包覆层142形成于一次粒子122(一次粒子122即为步骤(1)制备得到的基体材料)的表面，即获得由步骤(2)制备得到的一次包覆所得物)，第二包覆层144形成于所述第一包覆层142的表面，正极材料100整体分布呈现单晶颗粒结构，即一次粒子122(即由步骤(3)制备获得)。如图2所示，为本实施例高镍正极材料的SEM图，晶体颗粒形貌包括近似球形、近似立方体形和近似长方体形。
实施例2
与实施例1不同的是，步骤(1)中(n TiO2+n ZrO2):n MgO＝1：1。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子。
实施例3
与实施例1不同的是，步骤(1)中(n TiO2+n ZrO2):n MgO＝2：1。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子。
实施例4
与实施例1不同的是，步骤(1)中(n TiO2+n ZrO2):n MgO＝4：1。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子。
实施例5
与实施例1不同的是，步骤(1)中(n TiO2+n ZrO2):n MgO＝5：1。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子。
实施例6
与实施例1不同的是，步骤(1)中(n TiO2+n ZrO2):n MgO＝6：1。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子。
实施例7
与实施例1不同的是，步骤(1)中(n TiO2+n ZrO2):n MgO＝7：1。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子
实施例8
与实施例1不同的是，步骤(1)中掺杂剂替换为WO 3、ZrO 2、MgO，且(n WO3+n ZrO2):n MgO＝3：1。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子。
实施例9
与实施例1不同的是，步骤(1)中掺杂剂替换为WO 3、ZrO 2、Y 2O 3，且(n WO3+n ZrO2):n Y2O3＝3：1。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子。
实施例10
与实施例1不同的是，步骤(1)中掺杂剂替换为MoO 3、ZrO 2、Y 2O 3，且(n MoO3+n ZrO2):n Y2O3＝3：1。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子。
实施例11
与实施例1不同的是，步骤(1)中掺杂剂替换为MoO 3、ZrO 2、Al 2O 3，且(n MoO3+n ZrO2):n Al2O3＝3：1。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子。
实施例12
与实施例1不同的是，步骤(1)中掺杂剂替换为ZrO 2、MgO，且n ZrO2:n MgO＝3：1。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子。
实施例13
与实施例1不同的是，步骤(1)中一次热处理温度为650℃。
在本实施例的正极材料100的结构示意图如20所示，在本实施例的高镍正极材料的结构与实施例1相近，不同之处在于，部分一次粒子122聚集形成二次粒子124，正极材料整体分布呈现多晶颗粒结构，即二次粒子。
实施例14
与实施例1不同的是，步骤(1)中一次热处理温度为680℃。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现多晶颗粒结构，即二次粒子。
实施例15
与实施例1不同的是，步骤(1)中一次热处理温度为700℃。
在本实施例的高镍正极材料的结构与实施例13相近，正极材料整体分布呈现多晶颗粒结构，即二次粒子。
实施例16
与实施例1不同的是，步骤(1)中一次热处理温度为850℃。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子。
实施例17
与实施例1不同的是，步骤(1)中一次热处理温度为900℃。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子。
实施例18
与实施例1不同的是，步骤(1)中一次热处理温度为910℃。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子。
实施例19
与实施例1不同的是，步骤(2)Al 2O 3替换为铝酸锂。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子。
实施例20
与实施例1不同的是，步骤(2)Al 2O 3替换为氧化钛。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子。
实施例21
与实施例1不同的是，步骤(3)中H 3BO 3替换为Li 3BO 3。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子。
实施例22
与实施例1不同的是，步骤(3)中H 3BO 3替换为B 2O 3。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布呈现单晶颗粒结构，即一次粒子。
实施例23
与实施例1不同的是，不进行步骤(3)。
在本实施例的高镍正极材料的结构示意图参照图25，仅第一包覆层形成于一次粒子的表面，正极材料整体分布呈现单晶颗粒结构。
实施例24
与实施例1不同的是，不进行步骤(2)。
在本实施例的高镍正极材料的结构示意图参照图26，仅第二包覆层形成于一次粒子的表面，正极材料整体分布呈现单晶颗粒结构。
实施例25
与实施例1不同的是，前驱体选择的是Ni 0.83Co 0.12Mn 0.06(OH) 2前驱体。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布着单晶颗粒，即一次粒子。
实施例26
与实施例1不同的是，前驱体选择的是Ni 0.9Co 0.05Mn 0.05(OH) 2前驱体。
在本实施例的高镍正极材料的结构与实施例1相近，正极材料整体分布着单晶颗粒，即一次粒子。
对比例1
与实施例1不同的是，步骤(1)中掺杂剂替换为MgO、Al 2O 3。
对比例2
与实施例1不同的是，步骤(1)中掺杂剂替换为SrO、MgO。
对比例3
与实施例1不同的是，步骤(1)中掺杂剂替换为Al 2O 3、Y 2O 3。
对比例4
与实施例1不同的是，步骤(1)中掺杂剂替换为Y 2O 3、MgO。
对比例5
与实施例1不同的是，步骤(1)中掺杂剂替换为La 2O 3、Al 2O 3。
对比例6
与实施例1不同的是，步骤(1)中掺杂剂替换为ZrO 2、TiO 2。
性能测试：
(1)高镍材料的碱性杂质测试：
高镍材料表面碱性杂质含量是材料表面的特性，其可通过分析表面与水之间的反应产物定量测量。如果高镍材料粉末浸入水中，则发生表面反应。在反应期间，水的pH增加(随着碱性杂质的溶解)，并且通过pH滴定将碱含量定量。滴定的结果为碱性杂质含量。碱性杂质的含量可如下测量：将5.0g高镍材料粉末浸入100ml去离子水中，并且在密封的玻璃烧瓶中搅拌10分钟。在搅拌以溶解碱后，将粉末在水中的悬浮液过滤以得到澄清溶液。然后，在搅拌下在以0.5ml/min的速率添加0.1M HCl期间，通过记录pH曲线来滴定90ml澄清溶液，直至pH达到3。通过滴定以低浓度溶解于去离子水中的LiOH和Li 2CO 3的合适的混合物，获得参考电压曲线。在几乎所有情况下，观察到两个不同的平台。在pH 8～9之间具有终点y1(以ml为单位)的上平台是平衡OH -/H 2O，之后是平衡CO 3 2-/HCO 3 -，在pH 4～6之间具有终点y2(以ml为单位)的下平台是HCO 3 -/H 2CO 3。在第一与第二平台之间的拐点y1以及在第二平台之后的拐点y2由pH曲线的导数dpH/dVol的相应最小值获得。第二拐点一般接近pH 4.7。然后将结果以LiOH和Li 2CO 3重量百分比表示如下式(3)和(4)所示：
Figure PCTCN2022130946-appb-000001
Figure PCTCN2022130946-appb-000002
(2)高镍正极材料的XPS测试：
X射线光电子能谱(XPS)可以进行从材料表面到5nm至10nm左右(一般是5nm左右)的深度范围的分析，所以可以定量地分析表层部的约一半区域中的各元素的浓度。另外，通过进行窄扫描分析，可以分析元素的键合状态。X射线光电子能谱法(XPS)例如可以使用ULVAC-PHI,X射线光电子能谱分析(QuanteraII)进行。X射线源：Al单色100μm，25W，15kV；表面无蚀刻；光电子取出角度：45°；键合能量校正：将C1s光谱的C-C峰设为284.6eV；对本公开的高镍材料测定XPS，根据所得到的XPS谱图，对出现在结合能为850eV～870eV的位置的Ni键合部分的峰Ni2P 3/2进行分峰和曲线拟合，求出Ni 2+峰面积和Ni 3+峰面积，对出现在结合能为526eV～540eV的位置的O键合部分的峰O1S进行分峰和曲线拟合，求出O1S 晶格氧峰面积和O1S 杂质氧峰面积。
(3)电池容量标定
首先对进行电池容量标定，在常温25℃下以1/3C电流充电至4.25V，静置30min，然后以1/3C电流放电至2.5V，静置30min，循环2次并设第二次放电容量为C0，并以此为基准进行后续的DCIR测试。
(4)DCIR测试(保护电压1.0V～4.4V，测试温度：25℃)
a.25℃以0.2C0恒流充电10％C0，搁置2h[终止电压记为V1]，测试DCIR(1.5C0放电30s[终止电压记为V2]，搁置30min[终止电压记为V3]；以1.5C0充电30s[终止电压记为V4]，搁置5min)，以0.33C0放电至2.5V/cell，搁置30min；
b.25℃以0.2C0恒流充电20％C0，搁置2h[终止电压记为V1]，测试DCIR(1.5C0放电30s[终止电压记为V2]，搁置30min[终止电压记为V3]；以1.5C0充电30s[终止电压记为V4]，搁置5min)，以0.33C0放电至2.5V/cell，搁置30min；
c.25℃以0.2C0恒流充电50％C0，搁置2h[终止电压记为V1]，测试DCIR(1.5C0放电30s[终止电压记为V2]，搁置30min[终止电压记为V3]；以1.5C0充电30s[终止电压记为V4]，搁置5min)，以0.33C0放电至2.5V/cell，搁置30min；
d.25℃以0.2C0恒流充电80％C0，搁置2h[终止电压记为V1]，测试DCIR(1.5C0放电30s[终止电压记为V2]，搁置30min[终止电压记为V3]；以1.5C0充电30s[终止电压记为V4]，搁置5min)，以0.33C0放电至2.5V/cell，搁置30min；
按以下公式(5)和(6)计算不同SOC下的DCIR值：
DCIR放＝(V1-V2)/1.5C0*1000(单位：mΩ)  (5)
DCIR充＝(V1-V2)/1.5C0*1000(单位：mΩ)  (6)
用与上述循环前的DCIR的测定同样的方法进行每100次循环后的DCIR值的测定。
(5)高镍材料的全电池进行厚度膨胀测试：
在常温下将电池以0.5C恒流充电至4.25V，再恒压充电至电流为0.05C，此时电池处于满电态。测试存储前满电态电池的初始厚度，然后将电池置于60℃烘箱中，每隔20天测量电池的厚度，按如下计算公式(7)计算电池厚度膨胀率：
厚度膨胀率＝(存储后厚度-存储前厚度)/(存储前厚度)     (7)
(6)高温循环300周后的高镍材料进行切面测试：
采用日立E-3500离子研磨机将高温循环500周后的高镍材料进行切开，在日立S4800型冷场发射扫描电镜上观测其截面的形貌结构。
(7)pH的测试：
测试方法：GB/T 1717-1986《颜料水悬浮液pH值的测定》
仪器型号：梅特勒托利多pH计
方法简述：称取5.0000±0.0100g样品于100ml玻璃烧杯中，加入纯水45g，用玻璃棒搅匀，使其全部溶入纯水中，在超声波清洗仪里超声5min后，静置10min后，进行测定。
(8)电导率测试：
仪器型号：粉末电阻率测试仪
方法简述：将料腔深度调节至10mm；用药匙将待测样品粉末加入料腔，直至加满，将样品压平，转动手轮，调节压强，将压强依次调节至4，8，12，16，20MPa处，在每个压强处保压5s，读取并记录数据。
(9)比表面积测试：
测试方法：GB/T 19587-2017《气体吸附BET法测定固态物质比表面积》
仪器型号：Tristar3020比表面积分析仪
方法简述：称取3.0000±0.1000g样品，在300℃真空脱气1.0h进行完全脱气，去除表面吸附质后，使用氮气吸附法，通过吸附氮气量，计算出颗粒的比表面积
(10)平均粒径测试：
测试方法：GB/T 19077-2016《粒度分析激光衍射法》
仪器型号：马尔文激光粒度仪
方法简述：取适量样品于100mL烧杯中，加适量水，240W外超声15s，一次性全部倒入进样系统中进行充分分散使遮光度在8～15％，采用激光衍射原理进行粒度分布的测定。
一、高镍正极材料XPS与拟合测试
将各实施例和对比例制备的高镍正极材料XPS的测试Ni2P 3/2和O1S分峰和拟合后的面积比结果如下表1所示，其中实施例1、实施例8、对比例1、对比例2的Ni2P 3/2的分峰和拟合依次如图3、图4、图5及图6所示，实施例1、实施例8、对比例1、对比例2的O1S的分峰和拟合如图7、图8、图9及图10所示。
表1.各实施例和对比例制备的高镍正极材料XPS的测试Ni2P 3/2和O1S分峰和拟合后的面积比结果
Figure PCTCN2022130946-appb-000003
Figure PCTCN2022130946-appb-000004
如实施例1～26和对比例1～6所示，本公开制备的高镍正极材料，经过测定正极材料满足S1/(S1+S2)＞0.5且0.9＜α/β＜1.5，表明高镍材料基体表面的Ni 3+数量较少、Ni 2+数量较多，避免正极材料表面在脱锂时被氧化，有利于维持正极材料结构的稳定性，从而避免了正极活性材料和电解液的损失，进一步提高正极材料的容量，使得高镍正极材料的高温循环性能得到明显改善。此外，由于材料表面的Ni 3+数量较少，表面Ni 2+数量较多，能够减小材料在充放电过程中发生内部裂纹，使得材料内部结构稳定，使得本公开的正极材料应用于电池中进行长期循环时，电池的直流内阻增长得到明显的抑制。
实施例1、实施例8、对比例1、对比例2的Ni2P 3/2的分峰和拟合依次如图3、图4、图5及图6所示，实施例1、实施例8、对比例1、对比例2的O1S的分峰和拟合如图7、图8、图9及图10所示。本公开制备的高镍正极材料和对比例制备的材料S1/(S1+S2)面积比发生了明显变化，本公开实施例中样品的S1/(S1+S2)面积比＞1，说明材料表面的Ni 2+数量明显比Ni 3+数量多，而对比例中的S1/(S1+S2)面积比＜1；O1S 晶格氧/O1S 杂质氧面积比基本都＞0.5，这说明实施例的材料表面的碱性杂质都比较低。
经过表面碱性杂质测试可知：本公开实施例的高镍正极材料的表面碱性杂质总和更低，对比例的样品测试的表面碱性杂质LiOH和Li 2CO 3之和更高。
如表2所示，为本公开实施例1～26和对比例1～6的高镍正极材料的性能测试对比。
表2.实施例1～26和对比例1～6的高镍正极材料的性能测试
Figure PCTCN2022130946-appb-000005
根据本公开实施例1～26和对比例1～6制备的高镍正极材料在不同电压下，高温45℃全电池1C/1C循环300周容量保持率，经过高温性能测试可知：本公开实施例和对比例的正极材料高温循环性能发生了明显变化，在2.5V～4.2V条件下，本公开部分实施例正极材料的容量保持率在95％左右，而对比例正极的容量保持率都在93％以下，在2.5V～4.25V条件下测试，因为都存在相变，所以实验例和对比例的样品高温循环性能都有所降低，但是部分实施例依然明显优于对比例。
根据本公开实施例和对比例制备的高镍正极材料在2.5V～4.2V条件下高温45℃全电池1C/1C每循环100周测试直流内阻增长，实施例1、实施例8、对比例1及对比例2的容量微分曲线对比分析见图11、图12、图13、图14，结合表1和附图可知：本公开实施例和对比例的正极材料的直流内阻增长发生了明显变化，实施例的直流内阻增长明显低于对比例。由图11、12、13、14可知，实施例1的不可逆相转变最小，循环300周后的电压差ΔV最小，可见同时掺杂高化合价和低化合价的结构稳定性更好，材料表面和内部的结构更稳定。
根据本公开实施例和对比例制备的高镍正极材料制作成全电池，然后测试其高温60℃存储产气情况，每隔20天测量电池厚度，并计算厚度膨胀率，由表1可知：实施例和对比例的电池厚度增长发生了明显变化，但是，实施例的厚度膨胀增长明显低于对比例。
通过实施例12～18可知：将材料的一次合成温度控制在本公开的范围内，正极材料具备优异的电化学性能，一次热 处理的温度小于本公开限定的范围(实施例12)或一次热处理的温度大于本公开限定的范围(实施例18)，均会存在循环性能差、膨胀率高等缺点。
通过实施例1-22与实施例23的比较可知：本公开实施例通过对材料的第一层包覆的基础上进行第二层包覆，不但减少材料表面碱性杂质而且保护材料表面，减少材料表面碱性杂质中的Li 2CO 3分解产气，减少材料表面碱性杂质与电解液发生副反应产气，从而可以进一步提高材料的循环性能。实施23仅对基体材料进行一次包覆得到的正极材料，会存在循环性能差的缺点。
通过实施例1-22与实施例24的比较可知：本公开实施例通过对材料在二次包覆的同时，在内层进行一次包覆，通过化合价平衡使得高镍正极材料表面的Ni 2+数量不变或者进一步增加，提高了材料结构的稳定性，避免了材料与空气中的水分接触生成碱性杂质，减少了材料的产气，进而提高了材料的循环性并且降低了材料的膨胀率。实施例24仅对基体材料进行二次包覆得到的正极材料，会存在循环性能差和膨胀率高的缺点。
根据实施例1、8、25、26和对比例1、2、6的高镍材料循环300周进行氩离子切面分析，实施例1、8、25、26的切面分析结果参见附图15、16、19和20，对比例1、2、6的切面分析结果参见附图17、18和21，通过比较实施例和对比例的切面分析结果可知，实施例1、8、25、26的材料内部没有发生裂纹，而对比例1、2、6的材料内部出现了的裂纹，这一步说明本公开同时掺杂高化合价和低化合价的有利于材料结构的稳定，从而有利于进一步提高材料的循环性能。
以上所述仅为本公开的典型的实施例而已，并不用于限制本公开，对于本领域的技术人员来说，本公开可以有各种更改和变化。凡在本公开的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本公开的保护范围之内。
工业实用性
本公开提供一种高镍正极材料及其制备方法、锂离子电池，本公开的高镍正极材料表面的Ni 3+数量较少、Ni 2+数量较多，能够避免高镍正极材料表面在脱锂时被氧化，从而能够提升高镍正极材料的高温循环性能和结构稳定性，避免了正极活性材料和电解液的损失，进一步提高正极材料的容量，使得高镍正极材料的高温循环性能得到明显改善，具有优异的实用性能。

Claims (11)

  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通式为式(1)所示：
    Li xNi 1-(a+b+c+d+e+f)Co aM1 bM2 cM3 dM4 eM5 fO 2   (1)
    其中，0.95≤x≤1.2，0≤a≤0.15，0≤b≤0.10，0≤c≤0.05，0≤d≤0.05，0≤e≤0.05，0≤f≤0.05，0＜a+b+c+d+e+f≤0.2；
    所述高镍正极材料使用AlKα射线进行粉末XPS测定，当将结合能在850eV～870eV范围内出现的Ni2P 3/2峰进行分峰和拟合后，将Ni 2+的峰值面积设定为S1，Ni 3+的峰值面积设定为S2，将Ni 2+的峰半峰宽设定为α，将Ni 3+的峰半峰宽设定为β，S1、S2、α和β满足以下关系：
    S1/(S1+S2)＞0.5且0.9＜α/β＜1.5       (2)。
  2. 根据权利要求1所述的正极材料，其特征在于，所述正极材料包括二次粒子和/或一次粒子，所述一次粒子的至少部分表面包覆有包覆层，所述二次粒子包括多个带有包覆层的一次粒子。
  3. 根据权利要求2所述的正极材料，其特征在于，所述包覆层包括如下特征(1)～(11)中的至少一种：
    (1)所述包覆层包括第一包覆层和第二包覆层，所述第一包覆层形成于所述一次粒子的表面，所述第二包覆层形成于所述第一包覆层的表面；
    (2)所述包覆层包括第一包覆层，所述第一包覆层形成于所述一次粒子的表面；
    (3)所述包覆层包括第二包覆层，所述第二包覆层形成于所述一次粒子的表面；
    (4)所述包覆层包括第一包覆层和第二包覆层，所述第一包覆层包括在所述高镍正极材料中化合价大于等于正3价的元素；
    (5)所述包覆层包括第一包覆层和第二包覆层，所述第一包覆层包括Al、Ti、P、Si、Nb、Y、W、Cr、Zr和La中的至少一种；
    (6)所述包覆层包括第一包覆层和第二包覆层，所述第一包覆层包括含有Al、Ti、P、Si、Nb、Y、W、Cr、Zr和La中的至少一种的化合物；
    (7)所述包覆层包括第一包覆层和第二包覆层，所述第一包覆层包括含有Al、Ti、P、Si、Nb、Y、W、Cr、Zr和La中的至少一种的化合物，所述化合物为氧化物、氢氧化物或盐中的至少一种；
    (8)所述包覆层包括第一包覆层和第二包覆层，所述第二包覆层包括含有B、La和Al中的至少一种的化合物；
    (9)所述包覆层包括第一包覆层和第二包覆层，所述第二包覆层包括含有B、La和Al中的至少一种的化合物，所述化合物为氧化物、酸及含锂的盐中的至少一种；
    (10)所述包覆层包括第一包覆层和第二包覆层，第二包覆层包括含硼化合物，所述含硼化合物包括含硼的氧化物、含硼的酸及含硼和锂的盐中的至少一种；
    (11)所述包覆层包括第一包覆层和第二包覆层，第二包覆层包括含硼化合物，所述含硼化合物包括B 2O 3、H 3BO 3、Li 2O-B 2O 3、Li 3BO 3、Li 2B 4O 7、Li 2B 2O 7和Li 2B 8O 13中的至少一种。
  4. 根据权利要求1-3中任一项所述的正极材料，其特征在于，所述材料包括如下特征(1)～(18)中的至少一种：
    (1)所述M1包括Mn和/或Al；
    (2)所述M2包括在所述高镍正极材料中化合价大于等于正4价的元素；
    (3)所述M3包括在所述高镍正极材料中化合价等于正2价的元素；
    (4)所述M2和M3均包括Zr、Ti、Nb、Ce、Hf、W、Mo、Ta、Ge、Sn、Sr、Mg和Ba中的至少一种，且M2和M3不相同；
    (5)所述M4包括在所述高镍正极材料中化合价大于等于正3价的元素；
    (6)所述M4包括Al、Ti、P、Si、Nb、Y、W、Cr、Zr和La中的至少一种；
    (7)所述M5包括B、La和A中的至少一种；
    (8)所述高镍正极材料使用AlKα射线进行粉末XPS测定：当将结合能在850eV～870eV范围内出现的Ni2P 3/2峰进行分峰和拟合后，Ni 2+/Ni 3+的面积比大于1；
    (9)所述高镍正极材料使用AlKα射线进行粉末XPS测定：当将结合能在526eV～540eV范围内出现的O1S峰进行分峰和拟合后，O1S 晶格氧/O1S 杂质氧的面积比大于1/2；
    (10)所述高镍正极材料中LiOH的质量含量小于0.3wt％；
    (11)所述高镍正极材料中Li 2CO 3的质量含量小于0.3wt％；
    (12)所述高镍正极材料的晶体结构属于六方晶型晶体结构或单斜晶型晶体结构；
    (13)所述高镍正极材料的晶体颗粒形貌包括近似球形、近似立方体形和近似长方体形中的至少一种；
    (14)所述高镍正极材料的pH为：10＜pH＜12；
    (15)所述高镍正极材料的pH为：10.5＜pH＜11.7；
    (16)所述高镍正极材料的粉体电导率大于0.02S/cm；
    (17)所述高镍正极材料的比表面积为0.3m 2/g～0.8m 2/g；
    (18)所述高镍正极材料的平均粒径为2.5μm～4.5μm。
  5. 一种高镍正极材料的制备方法，其特征在于，包括以下步骤：
    将金属复合氢氧化物前驱体、含锂化合物和掺杂剂混合后进行一次热处理得到基体材料；
    所述掺杂剂包括含M2元素的化合物和含M3元素的化合物，所述含M2元素的化合物为含M2的氧化物、氢氧化物、锂金属氧化物中的至少一种，且所述M2在该化合物中的化合价大于等于正4价，所述含M3元素的化合物为含M3的氧化物、氢氧化物中的至少一种，且所述M3在该化合物中的化合价为正2价；
    将所述基体材料进行包覆得到高镍正极材料。
  6. 根据权利要求5所述的制备方法，其特征在于，所述方法包括如下特征(1)～(12)中的至少一种：
    (1)所述金属复合氢氧化物前驱体、含锂化合物和掺杂剂的质量比为1：(0.46～0.49)：(0.001～0.005)；
    (2)所述金属复合氢氧化物前驱体、含锂化合物和掺杂剂的质量比为1：(0.46～0.48)：(0.001～0.003)；
    (3)所述金属复合氢氧化物前驱体中金属总量Me与含锂化合物中Li的原子比为1.0＜Li/Me＜1.2；
    (4)所述含锂化合物包括含锂的盐、含锂的氢氧化物；
    (5)所述含锂化合物包括碳酸锂、氢氧化锂、硝酸锂和乙酸锂中的至少一种；
    (6)所述M2元素和M3元素均包括Zr、Ti、Nb、Ce、Hf、W、Mo、Ta、Ge、Sn、Sr、Mg和Ba中的至少一种，且M2和M3不相同；
    (7)所述掺杂剂中M2和M3的摩尔比n M2:n M3大于等于2：1；
    (8)所述掺杂剂的平均粒径为10nm～50nm；
    (9)所述一次热处理的温度为680℃～900℃；
    (10)所述一次热处理的时间为5h～20h；
    (11)所述一次热处理的升温速率为50℃/h～550℃/h；
    (12)所述基体材料的氧含量大于等于85％。
  7. 根据权利要求5或6所述的制备方法，其特征在于，所述方法包括将所述基体材料与第一包覆剂混合后进行二次热处理得到一次包覆所得物的步骤，所述方法包括如下特征(1)～(12)中的至少一种：
    (1)所述基体材料与第一包覆剂的质量比为1000：(0.5～3)；
    (2)所述第一包覆剂包括化合价大于等于正3价的金属元素或非金属元素；
    (3)第一包覆剂包括化合价大于等于正3价的金属元素或非金属元素的氧化物、盐或者氢氧化物中的至少一种；
    (4)所述第一包覆剂包括化合价大于等于正3价的金属元素或非金属元素，所述金属元素或非金属元素包括Al、Ti、P、Si、Nb、Y、W、Cr、Zr或La中的至少一种；
    (5)所述第一包覆剂包括铝酸锂、钛酸锂、钛酸镧锂、氧化钇、氧化铝和氧化钛中的至少一种；
    (6)所述第一包覆剂的平均粒径为10nm～50nm；
    (7)所述二次热处理的温度为600℃～800℃；
    (8)所述二次热处理的时间为1h～20h；
    (9)所述二次热处理的升温速率为50℃/h～550℃/h；
    (10)在所述二次热处理之后还包括在恒温条件下进行洗涤、洗涤后在真空条件下进行干燥处理的步骤，所述恒温条件的温度为10℃～25℃；
    (11)在所述二次热处理之后还包括在恒温条件下进行洗涤、洗涤后在真空条件下进行干燥处理的步骤，所述干燥处理的温度为100℃～200℃；
    (12)所述一次包覆所得物中的氧含量大于等于85％。
  8. 根据权利要求7所述的制备方法，其特征在于，所述方法还包括将所述一次包覆所得物与第二包覆剂混合后进行三次热处理的步骤，所述方法包括如下特征(1)～(9)中的至少一种：
    (1)所述第二包覆剂包括含有B、La和Al中的至少一种的化合物；
    (2)所述第二包覆剂包括含有B、La和Al中的至少一种的化合物，所述化合物为氧化物、酸，或者含锂的盐；
    (3)所述第二包覆剂包括含硼化合物；
    (4)所述第二包覆剂包括含硼化合物，所述含硼化合物包括含硼的氧化物、含硼的酸、或者含硼和锂的盐；
    (5)所述第二包覆剂包括含硼化合物，所述含硼化合物包括B 2O 3、H 3BO 3、Li 2O-B 2O 3、Li 3BO 3、Li 2B 4O 7、Li 2B 2O 7和Li 2B 8O 13中的至少一种；
    (6)所述一次包覆所得物与第二包覆剂的质量比为1：(0.0005-0.005)；
    (7)所述三次热处理的温度为200℃～600℃；
    (8)所述三次热处理的时间为1h～20h；
    (9)所述三次热处理的升温速率为50℃/h～550℃/h。
  9. 根据权利要求5-8任一项所述的制备方法，其特征在于，所述金属复合氢氧化物前驱体通过将金属盐溶液、络合剂和pH调节剂混合处理得到。
  10. 根据权利要求9所述的制备方法，其特征在于，所述方法包括如下特征(1)～(10)中的至少一种：
    (1)所述金属盐溶液、络合剂和pH调节剂的质量比为1：(0.01～0.10)：(0.1～0.8)；
    (2)所述金属盐溶液包括镍的盐溶液、钴的盐溶液、锰的盐溶液和铝的盐溶液中的至少一种；
    (3)所述络合剂包括氨水、硫酸铵、氯化铵、碳酸铵、氟化铵、肼、乙二胺四乙酸、次氮基三乙酸、尿嘧啶二乙酸和甘氨酸中的至少一种；
    (4)所述pH调节剂包括氢氧化钠和氢氧化钾中的至少一种；
    (5)所述混合处理的pH为9～13；
    (6)所述混合处理的温度为10℃～80℃；
    (7)所述混合处理的时间为10h～200h；
    (8)所述混合处理在搅拌状态下进行，所述搅拌速率为800rpm～1200rpm；
    (9)所述混合处理后还包括固液分离、洗涤和干燥的步骤；
    (10)所述金属复合氢氧化物前驱体的平均粒径为3μm～10μm。
  11. 一种锂离子电池，其特征在于，所述锂离子电池包括权利要求1～4任一项所述的高镍正极材料或由权利要求5～10所述的方法制备的高镍正极材料。
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