WO2023050763A1 - 高镍三元镍钴锰酸锂正极材料及其制备方法 - Google Patents

高镍三元镍钴锰酸锂正极材料及其制备方法 Download PDF

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WO2023050763A1
WO2023050763A1 PCT/CN2022/085905 CN2022085905W WO2023050763A1 WO 2023050763 A1 WO2023050763 A1 WO 2023050763A1 CN 2022085905 W CN2022085905 W CN 2022085905W WO 2023050763 A1 WO2023050763 A1 WO 2023050763A1
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cobalt
nickel
positive electrode
nano
preparation
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French (fr)
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马加力
张树涛
李子郯
江卫军
王壮
王亚州
白艳
杨红新
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蜂巢能源科技股份有限公司
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the invention relates to the field of lithium batteries, in particular to a high-nickel ternary nickel-cobalt lithium manganate positive electrode material and a preparation method thereof.
  • NCM nickel-cobalt lithium manganese oxide
  • NCA nickel-cobalt lithium aluminate
  • the source of the structural stability problem is: the phase transition (specifically from a layered structure to a rock-salt-like structure) that occurs during the electrochemical cycle of the high-nickel cathode material.
  • the simple high-nickel ternary positive electrode material is depleted by lithium ions during the charging and discharging process of the battery and divalent nickel ions
  • the ionic radii are basically the same, and the divalent nickel ions can easily migrate into the lithium layer, so there is a serious phenomenon of lithium-nickel mixing.
  • the cation mixed layer composed of this inactive NiO-like phase makes lithium ion transport worse, resulting in poor thermal stability. More seriously, the continuous phase transition increases the stress and strain inside the cathode material particles, generates microcracks along the grain boundaries, and may eventually accelerate side reactions with the electrolyte.
  • the source of the chemical stability problem is: usually, the residual alkali content on the surface of the high-nickel ternary cathode material is relatively high, generally in the form of lithium carbonate, lithium hydroxide and lithium oxide, etc., resulting in high alkalinity and high water absorption of the cathode material.
  • it poses difficulties for the subsequent coating of the positive electrode material, and at the same time puts forward higher requirements for the electrolyte in terms of alkali resistance. High alkalinity will cause the battery to swell during the cycle, which will affect the cycle performance of the battery.
  • Ni 4+ has high activity and is prone to side reactions with the electrolyte, thereby increasing the impedance of the battery and causing irreversible capacity loss.
  • the nucleophilic reaction between the cathode material and the electrolyte will also generate an SEI layer on the surface of the cathode material.
  • SEI solid electrolyte interface
  • the hydrofluoric acid (HF) formed by the decomposition of LiPF 6 salt is likely to dissolve the transition metal ions (TMs) in the cathode material, which are continuously deposited on the anode side or on the conductive agent, resulting in the degradation of battery performance.
  • the main purpose of the present invention is to provide a high-nickel ternary nickel-cobalt lithium manganese oxide positive electrode material and its preparation method, to solve the problem of high-nickel ternary positive electrode materials in the prior art because of their poor structural stability and relatively low chemical stability. Poor and the SEI layer formed on the surface of the battery during cycling cannot be effectively controlled, resulting in poor electrochemical performance of the battery.
  • the ratio of the total moles of nickel, cobalt and manganese in Ni x Co y Mnz (OH) 2 to the moles of lithium in lithium hydroxide is 1:(1.00 ⁇ 1.10).
  • the amount of nano-oxides of transition metals is Ni x Co y Mnz (OH) 2 and 0.05% to 0.35% of the total weight of lithium hydroxide; preferably, the weight ratio of cobalt phosphate, zirconium source and matrix material (0.005-0.015): (0.002-0.005): 1; preferably, the cobalt phosphate is cobalt phosphate and/or cobalt pyrophosphate.
  • transition metal nano-oxide is one or more of nano-zirconia, nano-titanium oxide, nano-tungsten oxide, nano-molybdenum oxide, nano-alumina or nano-yttrium oxide.
  • the source of zirconium is one or more of zirconium oxide, zirconium hydroxide, zirconium nitrate, zirconium phosphate and zirconium chloride.
  • the step of mixing Ni x Co y Mn z (OH) 2 , lithium hydroxide and transition metal nano-oxides includes: first stirring Ni x Co y Mn z (OH) 2 and lithium hydroxide , and then add the transition metal nano-oxide and perform the second stirring; preferably, during the first stirring process, the rotating speed is 700-2500rpm, and the stirring time is 15-35min; preferably, during the second stirring process, the rotating speed is 800 ⁇ 2000rpm, stirring time is 10 ⁇ 30min.
  • the calcination temperature is 700-850° C., and the calcination time is 5-20 hours; preferably, during the primary calcination process, the oxygen volume concentration is ⁇ 99.99%, and the oxygen flow rate is 10-30 L/min.
  • the phosphate of cobalt is obtained by the following preparation method: after mixing cobalt acetate and phosphoric acid, carry out precipitation reaction, filtration and drying in sequence, so as to obtain a mixture containing cobalt phosphate and cobalt pyrophosphate as cobalt phosphate; preferably , in the step of mixing the cobalt phosphate, the zirconium source and the base material: the third stirring method is used for mixing; preferably, in the third stirring process, the rotation speed is 400-2000 rpm, and the stirring time is 10-30 minutes.
  • the calcination temperature is 650-800° C., and the calcination time is 5-10 hours; preferably, during the secondary calcination process, the oxygen volume concentration is ⁇ 99.99%, and the oxygen flow rate is 10-30 L/min.
  • a high-nickel ternary nickel-cobalt lithium manganese oxide positive electrode material is provided, which is prepared by the above-mentioned preparation method.
  • the invention uses cobalt phosphate and zirconium source as raw materials to co-coat the high-nickel ternary nickel-cobalt lithium manganate positive electrode material, and can coat the surface to form a passivation layer after calcining.
  • the passivation layer can react with by-products (such as H 2 O and HF) and rearrange along the grain boundaries of the primary particles, thus effectively avoiding phase formation of high-nickel cathode materials during the electrochemical cycle. change (from layered structure to rock-salt-like structure).
  • the passivation layer is a cobalt-rich layer phase, which reacts with the residual alkali (LiOH and Li 2 CO 3 ) on the surface of the positive electrode material to generate lithium phosphate.
  • the reaction to generate lithium phosphate can consume most of the residual alkali on the surface, and then Effectively reduce the residual alkali content on the surface of the positive electrode material.
  • the lithium phosphate produced by it is also easy to react with H 2 O and HF in the by-products to form Li x POH y and Li x POF y , which prevents HF from corroding materials and avoids the loss of positive electrode active materials, thereby improving the performance of positive electrode materials. electrical properties.
  • the composition of the above-mentioned passivation layer is similar to the composition of the SEI layer formed by the nucleophilic reaction between the positive electrode material and the electrolyte.
  • the present invention is equivalent to artificially constructing an SEI film with high ionic conductivity, electrochemical and thermal stability on the positive electrode in advance, which can not only reduce the residual alkali content of the material, but also improve the electrical properties of the material , and its structural performance is easier to control, and its stability is better.
  • this method is simple and easy to operate, and is easier for industrial production.
  • the present invention additionally adds nano-oxides of transition metals, which can be doped into the lattice of the host material during the calcination process, thereby improving the electronic conductivity of the material, improving the conductivity and resistive conductivity.
  • Fig. 1 shows the SEM picture of the high-nickel ternary nickel-cobalt lithium manganate cathode material prepared in an embodiment of the present invention
  • Fig. 2 shows a graph of the cycle retention rate of the high-nickel ternary nickel-cobalt lithium manganate positive electrode material prepared in an embodiment of the present invention after being cycled 50 times at 25°C.
  • the invention uses cobalt phosphate and zirconium source as raw materials to co-coat the high-nickel ternary nickel-cobalt lithium manganate positive electrode material, and can coat the surface to form a passivation layer after calcining.
  • the passivation layer can react with byproducts (the source of which is the side reaction between the positive electrode material and the electrolyte, such as H 2 O and HF) and rearrange along the grain boundaries of the primary particles, thereby effectively Reduce the phase change (specifically from layered structure to rock-salt structure) of high-nickel cathode materials during electrochemical cycling.
  • the passivation layer is a cobalt-rich layer phase, which reacts with the residual alkali (LiOH and Li 2 CO 3 ) on the surface of the positive electrode material to generate lithium phosphate.
  • the reaction to generate lithium phosphate can consume most of the residual alkali on the surface, and then The residual alkali content on the surface of the positive electrode material is effectively reduced, and the residual alkali content on the surface of the material of the present invention can reach ⁇ 3500ppm.
  • the lithium phosphate produced by it is also easy to react with water and HF in the by-products to form Li x POH y and Li x POF y , which prevents HF from corroding materials, avoids the loss of positive electrode active materials, and improves the electric capacity of positive electrode materials. performance.
  • the reaction formula is as follows:
  • the composition of the above-mentioned passivation layer is similar to the composition of the SEI layer formed by the nucleophilic reaction between the positive electrode material and the electrolyte.
  • the present invention is equivalent to artificially constructing an SEI film with high ionic conductivity, electrochemical and thermal stability on the positive electrode in advance, which can not only reduce the residual alkali content of the material, but also improve the electrical properties of the material , and its structural performance is easier to control, and its stability is better.
  • this method is simple and easy to operate, and is easier for industrial production.
  • the present invention additionally adds nano-oxides of transition metals, which can be doped into the lattice of the host material during the high-temperature calcination process, thereby improving the electronic conductivity of the material.
  • the above-mentioned matrix material, cobalt phosphate and zirconium source can all be solid substances, and co-coating by dry method is better in operability and simpler than wet method.
  • the ratio of the total moles of nickel, cobalt, manganese in Ni x Co y Mnz (OH) to the moles of lithium in lithium hydroxide is 1:(1.00 ⁇ 1.10) ;
  • the amount of nano-oxides of transition metals is 0.05-0.35% of the total weight of Ni x Co y Mnz (OH) 2 and lithium hydroxide.
  • the weight ratio of cobalt phosphate, zirconium source and base material is (0.005-0.015):(0.002-0.005):1.
  • the passivation layer has better coating integrity and uniformity on the base material, and the surface material has better structural performance, better chemical stability, and better electrochemical performance.
  • the cobalt phosphate is cobalt phosphate and/or cobalt pyrophosphate.
  • the transition metal nano-oxide is one or more of nano-zirconia, nano-titanium oxide, nano-tungsten oxide, nano-molybdenum oxide, nano-alumina or nano-yttrium oxide.
  • the nano-oxides of transition metals are selected from the above types, and the conductivity and resistance conductivity of the material are better.
  • the source of zirconium is one or more of zirconium oxide, zirconium hydroxide, zirconium nitrate, zirconium phosphate or zirconium chloride.
  • the zirconium source is selected from the above types, and it has better compatibility with cobalt phosphate. When the two are coated on the surface of the base material together, the coating effect is better, and the electrochemical performance of the material is better.
  • the step of mixing Ni x Co y Mnz (OH) 2 , lithium hydroxide and transition metal nano-oxides includes: first mixing Ni x Co y Mnz (OH) 2 and hydrogen Lithium oxide is stirred for the first time, and then nano-oxides of transition metals are added for the second stirring; preferably, during the first stirring process, the rotation speed is 700-3000 rpm, and the stirring time is 15-35 minutes; preferably, the second stirring process , the rotation speed is 800-2000rpm, and the stirring time is 10-30min.
  • the calcination temperature is 700-850° C.
  • the calcination time is 5-20 hours
  • the oxygen volume concentration is ⁇ 99.99%
  • the oxygen flow rate is 10-30 L/min. Based on this, the doping process of nanomaterials is more stable and uniform, and the conductivity of the material is better.
  • the primary calcination is performed in a box furnace, and the temperature in the furnace is raised from room temperature to the temperature required for the primary calcination at a rate of 2-5° C./min. After the primary calcination, the temperature in the furnace is naturally lowered to 100°C, and the materials are sequentially crushed and sieved to obtain a powdery matrix material.
  • the sieve used in the sieving process is 300-400 mesh.
  • the cobalt phosphate is prepared by the following preparation method: after mixing cobalt acetate and phosphoric acid, successively carry out precipitation reaction, filtration and drying, to obtain a mixture containing cobalt phosphate and cobalt pyrophosphate, as cobalt of phosphate. Specifically, add cobalt acetate and phosphoric acid to absolute ethanol, and perform magnetic stirring to cause precipitation reaction of cobalt acetate and phosphoric acid.
  • Co 2 P 2 O 7 and Precipitate Co 3 (PO 4 ) 2 use a centrifuge for solid-liquid separation, wash and put the precipitated mixture in a vacuum oven at 120-150°C for 5-10 hours, and finally crush and sieve to obtain powdered cobalt-containing phosphate
  • the mixture of cobalt pyrophosphate and cobalt has an average particle size of 0.8-1.5 ⁇ m.
  • the particle size of the mixture containing cobalt phosphate and cobalt pyrophosphate obtained based on this step is better, and its compatibility with zirconium source and matrix material is better.
  • a more uniform and stable passivation layer can be formed, thereby more effectively improving the electrochemical performance of the material.
  • a third stirring method is used for mixing.
  • the rotation speed is 400-2000 rpm
  • the stirring time is 10-30 min. Based on this, the mixture containing cobalt phosphate and cobalt pyrophosphate, the zirconium source and the matrix material are mixed more uniformly and fully, which provides a strong foundation for the subsequent formation of a uniform and stable coating layer.
  • the calcination temperature is 650-800°C, and the calcination time is 5-10 hours; preferably, during the secondary calcination process, the oxygen volume Concentration ⁇ 99.99%, oxygen flow rate is 10-30L/min. If the secondary calcination temperature is too low, the bonding strength between the coating layer and the base material will be slightly weaker, and if the secondary calcination temperature is too high, the primary particles of the material will be burned and the capacity of the material will be slightly poor.
  • the secondary calcination is carried out in a box furnace, and the temperature in the furnace is raised from room temperature to the temperature required for the secondary calcination at a rate of 2-5° C./min. After the secondary calcination is completed, the temperature in the furnace is naturally lowered to 100°C, and the materials are sequentially crushed and sieved to obtain a high-nickel ternary nickel-cobalt lithium manganate cathode material.
  • the sieve used in the sieving process is 300-400 mesh.
  • the present invention also provides a high-nickel ternary nickel-cobalt lithium manganate positive electrode material, which is prepared by the above-mentioned preparation method.
  • the present invention uses cobalt phosphate and zirconium source as raw materials to co-coat the high-nickel ternary nickel-cobalt lithium manganese oxide positive electrode material, so as to form a passivation layer on its surface.
  • the passivation layer can react with by-products (the source of which is the side reaction between the positive electrode material and the electrolyte) and rearrange along the grain boundaries of the primary particles, thereby effectively reducing the negative impact of the high-nickel positive electrode material on the battery.
  • the phase transition (specifically, from layered structure to rock-salt-like structure) occurred during the chemical cycle.
  • the passivation layer is a cobalt-rich layer phase, which reacts with the residual alkali (LiOH and Li 2 CO 3 ) on the surface of the positive electrode material to generate lithium phosphate.
  • the reaction to generate lithium phosphate can consume most of the residual alkali on the surface, and then The residual alkali content on the surface of the positive electrode material is effectively reduced, and the residual alkali content on the surface of the material of the present invention can reach ⁇ 3500ppm.
  • the lithium phosphate produced by it is also easy to react with water and HF in the by-products to form Li x POH y and Li x POF y , which prevents HF from corroding materials, avoids the loss of positive electrode active materials, and improves the electric capacity of positive electrode materials. performance.
  • the composition of the above-mentioned passivation layer is similar to the composition of the SEI layer formed by the nucleophilic reaction between the positive electrode material and the electrolyte.
  • the present invention is equivalent to artificially constructing an SEI film with high ionic conductivity, electrochemical and thermal stability on the positive electrode in advance, which can not only reduce the residual alkali content of the material, but also improve the electrical properties of the material , and the structural properties are easier to control and the stability is better.
  • the present invention additionally adds nano-oxides of transition metals, which can be doped into the host material during the calcination process, thereby improving the electronic conductivity of the material.
  • the molar ratio of the total moles of nickel-cobalt-manganese metal in Ni x Co y Mn z (OH) 2 to lithium in lithium hydroxide is 1:1.00; the amount of nano-zirconia is Ni x Co y Mn z (OH) 2 and hydrogen 0.05% of the total weight of lithium oxide.
  • Example 2 The difference with Example 2 is that the molar ratio of the total moles of nickel-cobalt-manganese metal in Ni 0.83 Co 0.11 Mn 0.06 (OH) to lithium in lithium hydroxide is 1:1.10; the amount of nano-zirconia is Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 and 0.35% of the total weight of lithium hydroxide.
  • Example 2 The only difference from Example 2 is that the weight ratio of mixture, zirconium source and base material is 0.015:0.005:1.
  • Example 2 The difference with Example 2 is only that the molar ratio of the total moles of nickel-cobalt-manganese metal in Ni 0.83 Co 0.11 Mn 0.06 (OH) to lithium in lithium hydroxide is 1:0.8; the amount of nano-zirconia is Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 and 0.01% of the total weight of lithium hydroxide.
  • Example 2 contains a mixture of cobalt phosphate and cobalt pyrophosphate, and the weight ratio of zirconium source to matrix material is 0.001:0.001:1.
  • Example 2 The difference from Example 2 is only that during one calcination process, the calcination temperature is 850° C., and the calcination time is 20 h.
  • Example 2 The difference from Example 2 is only that in the secondary calcination process, the calcination temperature is 800° C., and the calcination time is 10 h.
  • Example 2 The difference from Example 2 is only that in the secondary calcination process, the calcination temperature is 850° C., and the calcination time is 20 h.
  • Example 1 The difference from Example 1 is only that zirconium oxide (zirconium source) is replaced by zirconium chloride in equal amounts.
  • Example 1 The difference from Example 1 is only that zirconium oxide (zirconium source) is replaced by zirconium nitrate in equal amounts.
  • Example 1 The difference from Example 1 is only that nano-zirconia (nano-oxide of transition metal) is replaced by nano-tungsten oxide in equal amounts.
  • Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 and lithium hydroxide First add Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 and lithium hydroxide to a high-speed mixer for stirring. During the stirring process, the stirring speed is 1500 rpm and the stirring time is 20 minutes. The molar ratio of the total moles of nickel-cobalt-manganese metal in Ni x Co y Mn z (OH) 2 to lithium in lithium hydroxide is 1:1.05.
  • Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 and lithium hydroxide are calcined in a box furnace to obtain the product; wherein, during the calcining process, the temperature in the furnace is increased at a heating rate of 2°C/min from The room temperature is raised to 750°C for calcination, and the calcination time is 10 hours; the oxygen volume concentration is ⁇ 99.99%, and the oxygen flow rate is 10-30L/min.
  • the temperature in the furnace was naturally lowered to 100°C, and the materials were sequentially crushed and sieved (the screen was 300 mesh).
  • Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 and lithium hydroxide into a high-speed mixer and stir to mix the two. During the stirring process, the stirring speed was 1500 rpm, and the stirring time was 20 min. The molar ratio of the total moles of nickel-cobalt-manganese metal in Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 to lithium in lithium hydroxide is 1:1.05.
  • Fig. 1 shows the SEM image of the high-nickel ternary nickel-cobalt lithium manganate cathode material prepared in Example 1 of the present invention
  • Fig. 2 shows the high-nickel ternary nickel prepared in Example 1 of the present invention Cycle retention curve of lithium cobalt manganese oxide cathode material after 50 cycles at 25°C.

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Abstract

本发明提供了一种高镍三元镍钴锰酸锂正极材料及其制备方法。该制备方法包括以下步骤：将Ni xCo yMn z(OH) 2、氢氧化锂及过渡金属的纳米氧化物混合后，进行一次煅烧，得到基体材料，其中x≥0.8，x+y+z＝1；将钴的磷酸盐、锆源与基体材料混合后，进行二次煅烧，得到高镍三元镍钴锰酸锂正极材料。基于此，本发明的正极材料电化学性能更佳，有效地解决了现有技术中存在的高镍三元正极材料因其结构稳定性较差、化学稳定性较差及电池循环过程中在其表面形成的SEI层无法有效控制从而导致的电池电化学性能较差的问题。

Description

高镍三元镍钴锰酸锂正极材料及其制备方法
本申请是以CN申请号为202111146774.1，申请日为2021年09月28日的中国申请为基础，并主张其优先权，该CN申请的公开内容再次作为整体引入本申请中。
技术领域
本发明涉及锂电池领域，具体而言，涉及一种高镍三元镍钴锰酸锂正极材料及其制备方法。
背景技术
现如今，低成本、高能量密度及低毒性的高镍三元镍钴锰酸锂正极材料(NCM)正极材料或者镍钴铝酸锂(NCA)正极材料被大量用于新能源动力汽车领域。虽然高镍正极材料镍含量很高，可以提高充放电容量，但其结构稳定性和化学稳定性会在后续电化学循环过程中不断下降。
其中，结构稳定性问题来源为：高镍正极材料在电化学循环过程中会发生的相变(具体由层状结构变为类岩盐结构)。而且，单纯的高镍三元正极材料在电池充放电过程中，因锂离子
Figure PCTCN2022085905-appb-000001
和二价镍离子
Figure PCTCN2022085905-appb-000002
的离子半径基本一致，二价镍离子很容易迁移进锂层，所以存在严重的锂镍混排现象。这种非活性类NiO相组成的阳离子混合层使得锂离子传输变差，导致热稳定性变差。更严重的是，连续相变使得正极材料颗粒内部的应力和应变变大，沿晶界产生微裂纹，并且最终可能加速与电解液的副反应。
化学稳定性问题来源为：通常高镍三元正极材料表面残余碱含量较高，一般以碳酸锂、氢氧化锂和氧化锂等形式存在，从而导致正极材料具有高碱度以及高吸水性。一方面，对于正极材料后续的涂覆造成困难，同时在耐碱性方面对电解液提出了更高的要求，高碱度会导致电池在循环过程中胀气，进而影响电池的循环性能。另一方面，在充电状态下，因正极材料颗粒表面上存在Ni 4+，Ni 4+活性较高，易与电解液发生副反应，从而增加了电池的阻抗以及带来不可逆容量的损失。
除此之外，正极材料与电解液之间发生亲核反应还会在正极材料表面产生SEI层。在电池长期的循环过程中，电化学催化正极材料与电解液之间的副反应，严重地增加了正极表面的非导电性和不稳定的固体电解质界面(SEI)层，从而导致材料的循环性能变差。而且，LiPF 6盐分解形成的氢氟酸(HF)很可能溶解正极材料中的过渡金属离子(TMs)，这些过渡金属离子不断地沉积在负极侧或导电剂上，导致电池性能下降。到目前为止，虽然本领域中研究人员已经引入了许多方法来减少正极侧不需要的副产物。然而，在实际电池循环使用过程中，正极SEI膜的生成完全没有办法被完全控制，这可能会导致电池电阻的增加和安全问题。近年来，在高镍正极材料中引入了晶界涂层的新概念，即利用钴含量高的阳离子混合层和类尖晶石Li xCoO 2相，以确保结构和界面的稳定性。然而，这种技术忽略了一点是这些方法并不能完全 防止微裂纹的产生，在电池循环期间，正极SEI膜在裂纹部位没有得到有效控制。因此，早期在正极上构建具有高离子电导率和电化学/热稳定性的SEI膜是非常必要的，既可以降低材料的残碱含量，又可以提高材料的电性能。
综上，现有技术中存在高镍三元正极材料因其结构稳定性较差、化学稳定性较差及无法有效控制电池循环过程中在其表面形成的SEI层从而导致电池电化学性能较差的问题。
发明内容
本发明的主要目的在于提供一种高镍三元镍钴锰酸锂正极材料及其制备方法，以解决现有技术中存在高镍三元正极材料因其结构稳定性较差、化学稳定性较差及电池循环过程中在其表面形成的SEI层无法有效控制从而导致电池电化学性能较差的问题。
为了实现上述目的，根据本发明的一个方面，提供了一种高镍三元镍钴锰酸锂正极材料的制备方法，该制备方法包括以下步骤：将Ni xCo yMn z(OH) 2、氢氧化锂及过渡金属的纳米氧化物混合后，进行一次煅烧，得到基体材料，其中x≥0.8，x+y+z＝1；将钴的磷酸盐、锆源与基体材料混合后，进行二次煅烧，得到高镍三元镍钴锰酸锂正极材料；钴的磷酸盐中钴的摩尔数与锆源中锆的摩尔数之比为1:(0.1～0.3)。
进一步地，Ni xCo yMn z(OH) 2中镍钴锰的总摩尔数与氢氧化锂中锂的摩尔数之比为1:(1.00～1.10)。
进一步地，过渡金属的纳米氧化物的用量为Ni xCo yMn z(OH) 2及氢氧化锂总重量的0.05～0.35％；优选地，钴的磷酸盐、锆源与基体材料的重量比为(0.005～0.015)：(0.002～0.005)：1；优选地，钴的磷酸盐为磷酸钴和/或焦磷酸钴。
进一步地，过渡金属的纳米氧化物为纳米氧化锆、纳米氧化钛、纳米氧化钨、纳米氧化钼、纳米氧化铝或纳米氧化钇中的一种或多种。
进一步地，锆源为氧化锆、氢氧化锆、硝酸锆、磷酸锆和氯化锆中的一种或多种。
进一步地，将Ni xCo yMn z(OH) 2、氢氧化锂与过渡金属的纳米氧化物混合的步骤包括：先将Ni xCo yMn z(OH) 2及氢氧化锂进行第一搅拌，再将过渡金属的纳米氧化物加入并进行第二搅拌；优选地，第一搅拌过程中，转速为700～2500rpm，搅拌时间为15～35min；优选地，第二搅拌过程中，转速为800～2000rpm，搅拌时间为10～30min。
进一步地，一次煅烧过程中，煅烧温度为700～850℃，煅烧时间为5～20h；优选地，一次煅烧过程中，氧气体积浓度≥99.99％，氧气流量为10～30L/min。
进一步地，钴的磷酸盐由以下制备方法制得：将醋酸钴及磷酸混合后依次进行沉淀反应、过滤及干燥，以得到含有磷酸钴和焦磷酸钴的混合物，作为钴的磷酸盐；优选地，将钴的磷酸盐、锆源与基体材料混合的步骤中：采用第三搅拌的方式进行混合；优选地，第三搅拌过程中，转速为400～2000rpm，搅拌时间为10～30min。
进一步地，二次煅烧过程中，煅烧温度为650～800℃，煅烧时间为5～10h；优选地，二次煅烧过程中，氧气体积浓度≥99.99％，氧气流量为10～30L/min。
为了实现上述目的，根据本发明的一个方面，提供了一种高镍三元镍钴锰酸锂正极材料，高镍三元镍钴锰酸锂正极材料由上述的制备方法制备得到。
本发明以钴的磷酸盐及锆源为原料，对高镍三元镍钴锰酸锂正极材料进行共包覆，经过煅烧后能够在其表面包覆形成钝化层。首先，在后续充放电过程中，该钝化层可与副产物(诸如H 2O和HF)反应沿着一次颗粒晶界重排，从而有效避免高镍正极材料在电化学循环过程中发生相变(由层状结构变为类岩盐结构)。同时，基于此钝化层，二价镍离子难以迁移进锂层，从而有效地避免了锂镍混排现象，进而，锂离子的传输性能及热稳定性均更佳。另外，基于此钝化层，还有效地避免了晶界产生微裂纹的现象，进而有效地降低了材料与电解液的副反应速率，促使材料的循环性能更佳。
其次，该钝化层为富钴层相，其与正极材料表面残碱(LiOH和Li 2CO 3)反应生成磷酸锂，一方面，生成磷酸锂的反应可以消耗其表面大部分残碱，进而有效地降低正极材料表面的残余碱含量。另一方面，由其生成的磷酸锂还容易与副产物中的H 2O和HF反应生成Li xPOH y和Li xPOF y，防止HF腐蚀材料，避免正极活性材料的损失，进而提高正极材料的电性能。
再者，上述钝化层的成分和正极材料与电解液发生亲核反应形成的SEI层成分相类似。本发明基于上述方法，相当于在正极上提前人为的构建了一个具有高离子电导率、电化学及热稳定性的SEI膜，其既可以降低材料的残碱含量，又可以提高材料的电性能，且其结构性能更易控制，稳定性也更佳。另外，此法简单易操作，更易于工业化生产。
除此以外，本发明在制备基体材料的步骤中，额外加入过渡金属的纳米氧化物，其可以在煅烧处理过程中掺杂进入主体材料晶格中，从而提高材料的电子电导率、提高材料的导电性及电阻导电率。
附图说明
构成本申请的一部分的说明书附图用来提供对本发明的进一步理解，本发明的示意性实施例及其说明用于解释本发明，并不构成对本发明的不当限定。在附图中：
图1示出了本发明一种实施例中制备得到的高镍三元镍钴锰酸锂正极材料的SEM图；
图2示出了本发明一种实施例中制备得到的高镍三元镍钴锰酸锂正极材料在25℃下循环50次后的循环保持率曲线图。
具体实施方式
需要说明的是，在不冲突的情况下，本申请中的实施例及实施例中的特征可以相互组合。下面将参考附图并结合实施例来详细说明本发明。
正如背景技术部分所描述的，现有技术中存在高镍三元正极材料因其结构稳定性较差、化学稳定性较差及电池循环过程中在其表面形成的SEI层无法有效控制从而导致电池电化学性能较差的问题。为了解决这一问题，本发明提出了一种高镍三元镍钴锰酸锂正极材料的制备方法，该制备方法包括以下步骤：将Ni xCo yMn z(OH) 2、氢氧化锂及过渡金属的纳米氧化物混合后，进行一次煅烧，得到基体材料，其中x≥0.8，x+y+z＝1；将钴的磷酸盐、锆源与基体材料混合后，进行二次煅烧，得到高镍三元镍钴锰酸锂正极材料；钴的磷酸盐中钴的摩尔数与锆源中锆的摩尔数之比为1:(0.1～0.3)。
本发明以钴的磷酸盐及锆源为原料，对高镍三元镍钴锰酸锂正极材料进行共包覆，经过煅烧后能够在其表面包覆形成钝化层。首先，在后续充放电过程中，该钝化层可与副产物(其来源为正极材料与电解液发生副反应产生，诸如H 2O和HF)反应沿着一次颗粒晶界重排，从而有效减少高镍正极材料在电化学循环过程中发生的相变(具体由层状结构变为类岩盐结构)情况。同时，基于此，二价镍离子难以迁移进锂层，从而有效地避免了锂镍混排现象，进而，锂离子的传输性能及热稳定性均更佳。另外，基于此，还有效地避免了晶界产生微裂纹的现象，进而有效地降低了材料与电解液的副反应速率，促使材料的循环性能更佳。
其次，该钝化层为富钴层相，其与正极材料表面残碱(LiOH和Li 2CO 3)反应生成磷酸锂，一方面，生成磷酸锂的反应可以消耗其表面大部分残碱，进而有效地降低正极材料表面的残余碱含量，本发明材料表面残碱含量可达到≤3500ppm。另一方面，由其生成的磷酸锂还容易与副产物中的水和HF反应生成Li xPOH y和Li xPOF y，防止HF腐蚀材料，避免正极活性材料的损失，进而提高正极材料的电性能。反应式如下所示：
LiOH/Li 2CO 3(正极材料表面上)+钴的磷酸盐→富钴层相(正极材料表面)+Li 3PO 4
Li 3PO 4+H 2O+HF→Li xPOH y和Li xPOF y
再者，上述钝化层的成分和正极材料与电解液发生亲核反应形成的SEI层成分相类似。本发明基于上述方法，相当于在正极上提前人为的构建了一个具有高离子电导率、电化学及热稳定性的SEI膜，其既可以降低材料的残碱含量，又可以提高材料的电性能，且其结构性能更易控制，稳定性也更佳。另外，此法简单易操作，更易于工业化生产。
除此以外，本发明在制备基体材料的步骤中，额外加入过渡金属的纳米氧化物，其可以在高温煅烧处理过程中掺杂进入主体材料晶格中，从而提高材料的电子电导率。
在一种优选的实施方案中，上述基体材料、钴的磷酸盐及锆源均可采用固体物质，采用干法共包覆相较湿法而言，其操作性更佳，更简单易行。
为了进一步提高材料的导电性及电阻导电率，优选Ni xCo yMn z(OH) 2中镍钴锰的总摩尔数与氢氧化锂中锂的摩尔数之比为1:(1.00～1.10)；优选地，过渡金属的纳米氧化物的用量为Ni xCo yMn z(OH) 2及氢氧化锂总重量的0.05～0.35％。
优选地，钴的磷酸盐、锆源与基体材料的重量比为(0.005～0.015):(0.002～0.005):1。基于此，钝化层对基体材料的包覆完整性及均匀性更佳，表面材料的结构性能更佳、化学稳定性更佳，电化学性能更佳。更优选地，钴的磷酸盐为磷酸钴和/或焦磷酸钴。
优选地，过渡金属的纳米氧化物为纳米氧化锆、纳米氧化钛、纳米氧化钨、纳米氧化钼、纳米氧化铝或纳米氧化钇中的一种或多种。过渡金属的纳米氧化物选自上述类型，材料的导电性及电阻导电率均更佳。
优选地，锆源为氧化锆、氢氧化锆、硝酸锆、磷酸锆或氯化锆中的一种或多种。锆源选自上述类型，其和钴的磷酸盐的适配性更佳，二者在共同包覆在基体材料表面时，包覆效果更佳，材料的电化学性能更佳。
在一种优选的实施方案中，将Ni xCo yMn z(OH) 2、氢氧化锂与过渡金属的纳米氧化物混合的步骤包括：先将Ni xCo yMn z(OH) 2及氢氧化锂进行第一搅拌，再将过渡金属的纳米氧化物加入进行第二搅拌；优选地，第一搅拌过程中，转速为700～3000rpm，搅拌时间为15～35min；优选地，第二搅拌过程中，转速为800～2000rpm，搅拌时间为10～30min。一次煅烧过程中，煅烧温度为700～850℃，煅烧时间为5～20h；氧气体积浓度≥99.99％，氧气流量为10～30L/min。基于此，纳米材料的掺杂过程更平稳及均匀，材料的导电性能更佳。
在一种优选的实施方案中，在箱式炉中进行一次煅烧，以2～5℃/min的升温速率将炉内温度由室温升至一次煅烧所需温度。一次煅烧结束后，将炉内温度自然降到100℃后，对物料依次进行破碎及过筛处理，即得到粉末状的基体材料。优选过筛处理过程中所用的筛网为300～400目。
在一种优选的实施方案中，钴的磷酸盐由以下制备方法制得：将醋酸钴及磷酸混合后依次进行沉淀反应、过滤及干燥，以得到含磷酸钴和焦磷酸钴的混合物，作为钴的磷酸盐。具体地，将醋酸钴和磷酸加入到无水乙醇中，进行磁力搅拌，使醋酸钴和磷酸发生沉淀反应，搅拌速度300～600rpm下，搅拌时间30～40min后，生成Co 2P 2O 7和Co 3(PO 4) 2沉淀，利用离心机进行固液分离，洗涤后将沉淀混合物放入真空烘箱120～150℃下烘干5～10h，最后经过破碎、过筛得到粉末状的含磷酸钴和焦磷酸钴的混合物，其平均粒径为0.8～1.5μm。基于此步骤得到的含有磷酸钴和焦磷酸钴的混合物颗粒度更佳，且其和锆源、基体材料的适配性更佳。在后续共包覆过程中，能更形成更均匀稳定的钝化层，进而更有效地提高材料的电化学性能。
在一种优选的实施方案中，将钴的磷酸盐、锆源与基体材料混合的步骤中，采用第三搅拌的方式进行混合。优选地，第三搅拌过程中，转速为400～2000rpm，搅拌时间为10～30min。基于此，含磷酸钴和焦磷酸钴的混合物、锆源与基体材料的混合更均匀、更充分，为后续形成均匀稳定包覆层付出了强有力的铺垫。
出于提高包覆过程稳定性、均匀性及完整性的考虑，优选二次煅烧过程中，煅烧温度为650～800℃，煅烧时间为5～10h；优选地，二次煅烧过程中，氧气体积浓度≥99.99％，氧气流量为10～30L/min。二次煅烧温度如果过低，则包覆层与基体材料的结合力度稍差，二次煅烧温度过高，则会使材料的一次颗粒被烧大，材料的容量稍差。
在一种优选的实施方案中，在箱式炉中进行二次煅烧，以2～5℃/min的升温速率将炉内温度由室温升至二次煅烧所需温度。二次煅烧结束后，将炉内温度自然降到100℃后，对物料依次进行破碎及过筛处理，即得到高镍三元镍钴锰酸锂正极材料。优选过筛处理过程中所用的筛网为300～400目。
本发明还提供了一种高镍三元镍钴锰酸锂正极材料，其由上述的制备方法制备得到。
基于前文的各项原因，本发明以钴的磷酸盐及锆源为原料，以对高镍三元镍钴锰酸锂正极材料进行共包覆，从而在其表面包覆形成钝化层。首先，在后续充放电过程中，该钝化层可与副产物(其来源为正极材料与电解液发生副反应产生)反应沿着一次颗粒晶界重排，从而有效减少高镍正极材料在电化学循环过程中发生的相变(具体由层状结构变为类岩盐结构)情况。同时，基于此，二价镍离子难以迁移进锂层，从而有效地避免了锂镍混排现象，进而，锂离子的传输性能及热稳定性均更佳。另外，基于此，还有效地避免了晶界产生微裂纹的现象，进而有效地降低了材料与电解液的副反应速率，促使材料的循环性能更佳。其次，该钝化层为富钴层相，其与正极材料表面残碱(LiOH和Li 2CO 3)反应生成磷酸锂，一方面，生成磷酸锂的反应可以消耗其表面大部分残碱，进而有效地降低正极材料表面的残余碱含量，本发明材料表面残碱含量可达到≤3500ppm。另一方面，由其生成的磷酸锂还容易与副产物中的水和HF反应生成Li xPOH y和Li xPOF y，防止HF腐蚀材料，避免正极活性材料的损失，进而提高正极材料的电性能。再者，上述钝化层的成分和正极材料与电解液发生亲核反应形成的SEI层成分相类似。本发明基于上述方法，相当于在正极上提前人为的构建了一个具有高离子电导率、电化学及热稳定性的SEI膜，其既可以降低材料的残碱含量，又可以提高材料的电性能，且结构性能更易控制，稳定性也更佳。除此以外，本发明在制备基体材料的步骤中，额外加入过渡金属的纳米氧化物，其可以在煅烧处理过程中掺杂进入主体材料，从而提高材料的电子电导率。
以下结合具体实施例对本申请作进一步详细描述，这些实施例不能理解为限制本申请所要求保护的范围。
实施例1
1、先将Ni 0.83Co 0.11Mn 0.06(OH) 2及氢氧化锂先加入至高速混合机中进行第一搅拌，再将过渡金属的纳米氧化物加入至高速混合机中进行第二搅拌以混合三者。其中，第一搅拌过程中，搅拌速度为1500rpm，搅拌时间为20min。Ni xCo yMn z(OH) 2中镍钴锰金属总摩尔数与氢氧化锂中锂的摩尔比为1:1.05；纳米氧化锆的用量为Ni xCo yMn z(OH) 2及氢氧化锂总重量的0.15％。
2、将Ni 0.83Co 0.11Mn 0.06(OH) 2、氢氧化锂及纳米氧化锆混合后，在箱式炉中进行一次煅烧，得到基体材料；其中，一次煅烧过程中，以2℃/min的升温速率将炉内温度由室温升至750℃进行煅烧，煅烧时间为10h；氧气体积浓度≥99.99％，氧气流量为10～30L/min。一次煅烧结束后，将炉内温度自然降到100℃后，对物料依次进行破碎及过筛处理(筛网为300目)，得到基体材料。
3、将醋酸钴和磷酸加入到无水乙醇中，进行磁力搅拌，使醋酸钴和磷酸发生沉淀反应，搅拌速度450rpm下，搅拌时间30min后，生成Co 2P 2O 7和Co 3(PO 4) 2沉淀，利用离心机进行固液分离，洗涤后将沉淀混合物放入真空烘箱120℃下烘干5h，最后经过破碎、过筛得到粉末状的含磷酸钴和焦磷酸钴的混合物，其粒度大小为0.8μm。
4、将上述含磷酸钴和焦磷酸钴的混合物、锆源(氧化锆)与上述基体材料加入至高速混合机中进行第三搅拌；第三搅拌过程中，转速为1200rpm，搅拌时间为20min。其中，混合物、锆源与基体材料的重量比为0.012：0.0035：1。
5、将混合后的物料箱式炉中进行二次煅烧，以3℃/min的升温速率将炉内温度由室温升至700℃，煅烧时间为5h；氧气体积浓度≥99.99％，氧气流量为10～30L/min。二次煅烧结束后，将炉内温度自然降到100℃后，对物料依次进行破碎及过筛(325目)处理，即得到高镍三元镍钴锰酸锂正极材料。
实施例2
1、先将Ni 0.83Co 0.11Mn 0.06(OH) 2及氢氧化锂先加入至高速混合机中进行第一搅拌，再将过渡金属的纳米氧化物加入至高速混合机中进行第二搅拌以混合三者。其中，第一搅拌过程中，搅拌速度为1000rpm，搅拌时间为20min；第二搅拌过程中，转速为1000rpm，搅拌时间为30min。Ni xCo yMn z(OH) 2中镍钴锰金属总摩尔数与氢氧化锂中锂的摩尔比为1：1.00；纳米氧化锆的用量为Ni xCo yMn z(OH) 2及氢氧化锂总重量的0.05％。
2、将Ni 0.83Co 0.11Mn 0.06(OH) 2、氢氧化锂及纳米氧化锆混合后，在箱式炉中进行一次煅烧，得到基体材料；其中，一次煅烧过程中，以2℃/min的升温速率将炉内温度由室温升至700℃进行煅烧，煅烧时间为5h；氧气体积浓度≥99.99％，氧气流量为10～30L/min。一次煅烧结束后，将炉内温度自然降到100℃后，对物料依次进行破碎及过筛处理(筛网为300目)，得到基体材料。
3、将醋酸钴和磷酸加入到无水乙醇中，进行磁力搅拌，使醋酸钴和磷酸发生化学沉淀反应，搅拌速度450rpm下，搅拌时间30min后，生成Co 2P 2O 7和Co 3(PO 4) 2沉淀，利用离心机进行固液分离，洗涤后将沉淀混合物放入真空烘箱120℃下烘干5h，最后经过破碎、过筛得到粉末状的含磷酸钴和焦磷酸钴的混合物，其粒度大小为0.8μm。
4、将上述含磷酸钴和焦磷酸钴的混合物、锆源(氧化锆)与上述基体材料加入至高速混合机中进行第三搅拌；第三搅拌过程中，转速为1000rpm，搅拌时间为30min。其中，混合物、锆源与基体材料的重量比为0.005：0.002：1。
5、将混合后的物料箱式炉中进行二次煅烧，以3℃/min的升温速率将炉内温度由室温升至650℃，煅烧时间为5h；氧气体积浓度≥99.99％，氧气流量为10L/min。二次煅烧结束后，将炉内温度自然降到100℃后，对物料依次进行破碎及过筛(325目)处理，即得到高镍三元镍钴锰酸锂正极材料。
实施例3
和实施例2的区别在于Ni 0.83Co 0.11Mn 0.06(OH) 2中镍钴锰金属总摩尔数与氢氧化锂中锂的摩尔比为1:1.10；纳米氧化锆的用量为Ni 0.83Co 0.11Mn 0.06(OH) 2及氢氧化锂总重量的0.35％。
实施例4
和实施例2的区别仅在于混合物、锆源与基体材料的重量比为0.015:0.005:1。
实施例5
和实施例2的区别仅在于Ni 0.83Co 0.11Mn 0.06(OH) 2中镍钴锰金属总摩尔数与氢氧化锂中锂的摩尔比为1:0.8；纳米氧化锆的用量为Ni 0.83Co 0.11Mn 0.06(OH) 2及氢氧化锂总重量的0.01％。
实施例6
和实施例2的区别仅在于含有磷酸钴和焦磷酸钴的混合物、锆源与基体材料的重量比为0.001:0.001:1。
实施例7
和实施例2的区别仅在于一次煅烧过程中，煅烧温度为850℃，煅烧时间为20h。
实施例8
和实施例2的区别仅在于二次煅烧过程中，煅烧温度为800℃，煅烧时间为10h。
实施例9
和实施例2的区别仅在于二次煅烧过程中，煅烧温度为850℃，煅烧时间为20h。
实施例10
和实施例1的区别仅在于将氧化锆(锆源)等量替换为氯化锆。
实施例11
和实施例1的区别仅在于将氧化锆(锆源)等量替换为硝酸锆。
实施例12
和实施例1的区别仅在于将纳米氧化锆(过渡金属的纳米氧化物)等量替换为纳米氧化钨。
对比例1
1、先将Ni 0.83Co 0.11Mn 0.06(OH) 2及氢氧化锂加入至高速混合机中进行搅拌，搅拌过程中，搅拌速度为1500rpm，搅拌时间为20min。Ni xCo yMn z(OH) 2中镍钴锰金属总摩尔数与氢氧化锂中锂的摩尔比为1：1.05。
2、将Ni 0.83Co 0.11Mn 0.06(OH) 2、氢氧化锂混合后，在箱式炉中进行煅烧，得到产品；其中，煅烧过程中，以2℃/min的升温速率将炉内温度由室温升至750℃进行煅烧，煅烧时间为10h；氧气体积浓度≥99.99％，氧气流量为10～30L/min。煅烧结束后，将炉内温度自然降到100℃后，对物料依次进行破碎及过筛处理(筛网为300目)。
对比例2
1、先将Ni 0.83Co 0.11Mn 0.06(OH) 2及氢氧化锂加入至高速混合机中进行搅拌以混合二者。搅拌过程中，搅拌速度为1500rpm，搅拌时间为20min。Ni 0.83Co 0.11Mn 0.06(OH) 2中镍钴锰金属总摩尔数与氢氧化锂中锂的摩尔比为1:1.05。
2、将Ni 0.83Co 0.11Mn 0.06(OH) 2及氢氧化锂混合后，在箱式炉中进行一次煅烧，得到基体材料；其中，一次煅烧过程中，以2℃/min的升温速率将炉内温度由室温升至750℃进行煅烧，煅烧时间为10h；氧气体积浓度≥99.99％，氧气流量为10～30L/min。一次煅烧结束后，将炉内温度自然降到100℃后，对物料依次进行破碎及过筛处理(筛网为300目)，得到基体材料。
3、将醋酸钴和磷酸加入到无水乙醇中，进行磁力搅拌，使醋酸钴和磷酸发生沉淀反应，搅拌速度450rpm下，搅拌时间30min后，生成Co 2P 2O 7和Co 3(PO 4) 2沉淀，利用离心机进行固液分离，洗涤后将沉淀混合物放入真空烘箱120℃下烘干5h，最后经过破碎、过筛得到粉末状的含磷酸钴和焦磷酸钴的混合物，其粒度大小为0.8μm。
4、将上述含磷酸钴和焦磷酸钴的混合物与上述基体材料加入至高速混合机中进行第三搅拌；第三搅拌过程中，转速为1200rpm，搅拌时间为20min。其中，混合物与基体材料的重量比为0.012：1。
5、将混合后的物料箱式炉中进行二次煅烧，以3℃/min的升温速率将炉内温度由室温升至700℃，煅烧时间为5h；氧气体积浓度≥99.99％，氧气流量为10～30L/min。二次煅烧结束后，将炉内温度自然降到100℃后，对物料依次进行破碎及过筛(325目)处理，得到产品。
对比例3
1、先将Ni 0.83Co 0.11Mn 0.06(OH) 2及氢氧化锂先加入至高速混合机中进行第一搅拌，再将过渡金属的纳米氧化物加入至高速混合机中进行第二搅拌以混合三者。其中，第一搅拌过程中，搅拌速度为1500rpm，搅拌时间为20min。Ni 0.83Co 0.11Mn 0.06(OH) 2中镍钴锰金属总摩尔数与氢氧化锂中锂的摩尔比为1:1.05；纳米氧化锆的用量为Ni 0.83Co 0.11Mn 0.06(OH) 2及氢氧化锂总重量的0.15％。
2、将Ni 0.83Co 0.11Mn 0.06(OH) 2、氢氧化锂及纳米氧化锆混合后，在箱式炉中进行一次煅烧，得到基体材料；其中，一次煅烧过程中，以2℃/min的升温速率将炉内温度由室温升至750℃进行煅烧，煅烧时间为10h；氧气体积浓度≥99.99％，氧气流量为10～30L/min。一次煅烧结束后，将炉内温度自然降到100℃后，对物料依次进行破碎及过筛处理(筛网为300目)，得到基体材料。
3、将锆源(氧化锆)与上述基体材料加入至高速混合机中进行第三搅拌；第三搅拌过程中，转速为1200rpm，搅拌时间为20min。其中，锆源与基体材料的重量比为0.0035：1。
4、将混合后的物料箱式炉中进行二次煅烧，以3℃/min的升温速率将炉内温度由室温升至700℃，煅烧时间为5h；氧气体积浓度≥99.99％，氧气流量为10～30L/min。二次煅烧结束后，将炉内温度自然降到100℃后，对物料依次进行破碎及过筛(325目)处理，得到产品。
性能表征：
将上述实施例及对比例中的高镍三元镍钴锰酸锂正极材料与导电剂、粘结剂以及NMP进行匀浆，再进行涂布、辊压、裁片以组装2032扣式电池，从而评价正极材料的电化学性能(充放电电压为3.0～4.3V，温度为25℃)，测试其残碱含量。
其中，图1示出了本发明实施例1中制备得到的高镍三元镍钴锰酸锂正极材料的SEM图；图2示出了本发明实施例1中制备得到的高镍三元镍钴锰酸锂正极材料在25℃下循环50次后的循环保持率曲线。
上述实施例及对比例的电化学性能及残碱含量测试结果见下表1所示。
表1
Figure PCTCN2022085905-appb-000003
以上仅为本发明的优选实施例而已，并不用于限制本发明，对于本领域的技术人员来说，本发明可以有各种更改和变化。凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种高镍三元镍钴锰酸锂正极材料的制备方法，其特征在于，所述制备方法包括以下步骤：
    将Ni xCo yMn z(OH) 2、氢氧化锂及过渡金属的纳米氧化物混合后，进行一次煅烧，得到基体材料，其中x≥0.8，x+y+z＝1；
    将钴的磷酸盐、锆源与所述基体材料混合后，进行二次煅烧，得到所述高镍三元镍钴锰酸锂正极材料；其中，所述钴的磷酸盐中钴的摩尔数与所述锆源中锆的摩尔数之比为1:(0.1～0.3)。
  2. 根据权利要求1所述的制备方法，其特征在于，所述Ni xCo yMn z(OH) 2中镍钴锰的总摩尔数与所述氢氧化锂中锂的摩尔数之比为1:(1.00～1.10)。
  3. 根据权利要求1或2所述的制备方法，其特征在于，所述过渡金属的纳米氧化物的用量为所述Ni xCo yMn z(OH) 2及所述氢氧化锂总重量的0.05～0.35％；
    优选地，所述钴的磷酸盐、所述锆源与所述基体材料的重量比为(0.005～0.015):(0.002～0.005):1；
    优选地，所述钴的磷酸盐为磷酸钴和/或焦磷酸钴。
  4. 根据权利要求1至3中任一项所述的制备方法，其特征在于，所述过渡金属的纳米氧化物为纳米氧化锆、纳米氧化钛、纳米氧化钨、纳米氧化钼、纳米氧化铝或纳米氧化钇中的一种或多种。
  5. 根据权利要求1至3中任一项所述的制备方法，其特征在于，所述锆源为氧化锆、氢氧化锆、硝酸锆、磷酸锆或氯化锆中的一种或多种。
  6. 根据权利要求1至5中任一项所述的制备方法，其特征在于，将所述Ni xCo yMn z(OH) 2、所述氢氧化锂与所述过渡金属的纳米氧化物混合的步骤包括：
    先将所述Ni xCo yMn z(OH) 2及所述氢氧化锂进行第一搅拌，再将所述过渡金属的纳米氧化物加入并进行第二搅拌；
    优选地，所述第一搅拌过程中，转速为700～2500rpm，搅拌时间为15～35min；
    优选地，所述第二搅拌过程中，转速为800～2000rpm，搅拌时间为10～30min。
  7. 根据权利要求1至6中任一项所述的制备方法，其特征在于，所述一次煅烧过程中，煅烧温度为700～850℃，煅烧时间为5～20h；优选地，所述一次煅烧过程中，氧气体积浓度≥99.99％，氧气流量为10～30L/min。
  8. 根据权利要求1至3中任一项所述的制备方法，其特征在于，所述钴的磷酸盐由以下制备方法制得：将醋酸钴及磷酸混合后依次进行沉淀反应、过滤及干燥，以得到含有所述磷酸钴和所述焦磷酸钴的混合物，作为所述钴的磷酸盐；
    优选地，将所述钴的磷酸盐、所述锆源与所述基体材料混合的步骤中，采用第三搅拌的方式进行混合；优选地，所述第三搅拌过程中，转速为400～2000rpm，搅拌时间为10～30min。
  9. 根据权利要求1至8中任一项所述的制备方法，其特征在于，所述二次煅烧过程中，煅烧温度为650～800℃，煅烧时间为5～10h；优选地，所述二次煅烧过程中，氧气体积浓度≥99.99％，氧气流量为10～30L/min。
  10. 一种高镍三元镍钴锰酸锂正极材料，其特征在于，所述高镍三元镍钴锰酸锂正极材料由权利要求1至9中任一项所述的制备方法制备得到。
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