WO2024197844A1 - 高镍三元正极材料表面改性的方法及其应用 - Google Patents

高镍三元正极材料表面改性的方法及其应用 Download PDF

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Publication number
WO2024197844A1
WO2024197844A1 PCT/CN2023/085570 CN2023085570W WO2024197844A1 WO 2024197844 A1 WO2024197844 A1 WO 2024197844A1 CN 2023085570 W CN2023085570 W CN 2023085570W WO 2024197844 A1 WO2024197844 A1 WO 2024197844A1
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lithium silicate
positive electrode
silicate solution
nickel ternary
electrode material
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French (fr)
Inventor
黄龙胜
李长东
阮丁山
刘伟健
袁玲
区炜聪
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Hunan Brunp Recycling Technology Co Ltd
Guangdong Brunp Recycling Technology Co Ltd
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Hunan Brunp Recycling Technology Co Ltd
Guangdong Brunp Recycling Technology Co Ltd
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Priority to CN202380009014.7A priority Critical patent/CN116830320A/zh
Priority to PCT/CN2023/085570 priority patent/WO2024197844A1/zh
Publication of WO2024197844A1 publication Critical patent/WO2024197844A1/zh
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the invention belongs to the technical field of lithium ion batteries, and specifically relates to a method for surface modification of a high-nickel ternary positive electrode material and application thereof.
  • Ternary layered oxide cathode materials have moderate cost, high specific capacity, and the ratio of transition metals can be adjusted within a certain range. They are widely used in the field of long-range power batteries. Among them, high-nickel ternary cathode materials have their unique advantages in energy density. However, poor cycling and thermal performance also limit their application. In addition, as the nickel content increases, the amount of residual alkali gradually increases, and the air sensitivity problem of the material itself is aggravated. To meet this challenge, various doping/coating strategies are used to change the bulk structure or surface and interface properties of high-nickel materials. Among them, hydrophobic modification can change the inherent hydrophilic properties of the material surface, reduce the hygroscopicity of the material, and play an important role in alleviating the deterioration of the material.
  • Alkyl silicates are a type of surface modification material widely used in the field of building waterproofing. They have the characteristics of good water solubility, strong adhesion to the substrate, excellent waterproofness and weather resistance, etc. They are often used for waterproofing treatment of building materials such as concrete and have a wide range of applications.
  • Alkyl silicates used on the market include sodium methyl silicate, potassium methyl silicate, sodium ethyl silicate, sodium phenyl silicate, etc. These products often have some residual sodium and potassium ions when directly used for waterproofing modification. They are often difficult to remove in the process of direct application to lithium battery materials, which is not conducive to the electrochemical performance of the materials.
  • organosilicon materials are often used as hydrophobic modifiers to modify the surface of positive electrode materials.
  • the solvents used in these methods are mostly organic reagents, which are relatively expensive. Even if some methods can use water as an optional solvent, there is still the problem that the hydrolysis reaction time of organosilicon materials in aqueous solution is too long, and high-nickel ternary positive electrode materials cannot be stored in aqueous solution for a long time. The longer the time, the more serious the lithium loss in the material lattice, which will seriously weaken the electrical properties of the material.
  • the present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a method for surface modification of a high-nickel ternary positive electrode material and its application.
  • a method for surface modification of a high-nickel ternary cathode material comprising the following steps:
  • the spray method is to spray the alkyl lithium silicate solution onto the surface of the high-nickel ternary positive electrode material while keeping it in a stirred state to cause a chemical reaction, and the wet material obtained after spraying is subjected to the drying heat treatment;
  • the solid-liquid blending method is to disperse the high-nickel ternary positive electrode material into the alkyl lithium silicate solution for reaction, and the solid obtained after solid-liquid separation is subjected to the drying heat treatment.
  • the preparation method of the alkyl lithium silicate solution is: alkyltrialkoxysilane, an acid catalyst and water are mixed for hydrolysis reaction to obtain an alkyl silicic acid solution, the alkyl silicic acid solution is mixed with a lithium hydroxide solution for reaction, and the solid-liquid separation is performed to obtain the alkyl lithium silicate solution.
  • the temperature of the hydrolysis reaction is 25-50°C, and the reaction time is 0.1-5h.
  • the molar ratio of the alkyl silicic acid in the alkyl silicic acid solution to the lithium hydroxide in the lithium hydroxide solution is 1:(0.8-2).
  • the mass concentration of the lithium hydroxide solution is 10-120g/L.
  • the mixing reaction time of the alkyl silicic acid solution and the lithium hydroxide solution is 5-30min.
  • the solid-liquid separation method is filtration or vacuum-assisted filtration. It should be noted that the solid The solid separated from the liquid is generally an insoluble alkyl silicate generated by excessive hydrolysis polymerization. Although the amount of insoluble alkyl silicate is relatively small, it still needs to be filtered out to avoid interference with the product.
  • the alkyl lithium silicate solution is at least one of a methyl lithium silicate solution, a vinyl lithium silicate solution, a propyl lithium silicate solution, an octyl lithium silicate solution, a phenyl lithium silicate solution or a dodecyl lithium silicate solution.
  • the corresponding alkyl trialkoxy silane can be selected as needed to prepare the corresponding alkyl lithium silicate.
  • the alkyl lithium silicate solution is a methyl lithium silicate solution or a propyl lithium silicate solution.
  • the selected alkyl trialkoxy silane is preferably methyl trimethoxy silane or methyl triethoxy silane.
  • the selected alkyl trialkoxy silane is preferably propyl trimethoxy silane.
  • the molar ratio of the alkyltrialkoxysilane to water is 1:(1-5); the amount of the acid catalyst is 0.1%-2% of the weight of the alkyltrialkoxysilane.
  • the acid catalyst is at least one of hydrochloric acid, acetic acid or phytic acid.
  • the mass ratio of the alkyl lithium silicate to the high-nickel ternary positive electrode material in the alkyl lithium silicate solution is (0.1-3):100.
  • the stirring speed is 600-1500 rpm.
  • the alkyl lithium silicate solution in the spraying method, is sprayed for 5-15 minutes.
  • the spray rate is 10-30 mL/min.
  • the reaction time of the high-nickel ternary positive electrode material and the alkyl lithium silicate solution is 3-30 minutes.
  • the reaction of the high-nickel ternary positive electrode material and the alkyl lithium silicate solution is carried out at a stirring speed of 100-300 rpm.
  • the high-nickel ternary positive electrode material in the solid-liquid blending method, is dispersed in the alkyl lithium silicate solution in any of the following ways: (1) diluting the alkyl lithium silicate solution to 5-50 g/L, and then adding the high-nickel ternary positive electrode material to the diluted alkyl lithium silicate solution; (2) adding the high-nickel ternary positive electrode material to the alkyl lithium silicate solution; The mixture is dispersed in water, and then an alkyl lithium silicate solution is added. The concentration of the alkyl lithium silicate in the obtained mixture is 5-50 g/L.
  • the temperature of the drying heat treatment is 110-150° C. and the time is 8-24 hours.
  • the drying and heat treatment further includes a sieving operation, and the mesh number of the sieving sieve is 100-400 meshes.
  • the invention also provides application of the method in preparing lithium ion batteries.
  • the present invention applies alkyl lithium silicate to the modification process of high-nickel ternary positive electrode materials.
  • the hydrophilic oxygen-containing groups (hydroxyl-OH, oxygen-containing anions Si-O-Li + ) of the alkyl lithium silicate itself can react with the hydrophilic oxygen-containing functional groups (-OH, -O-) of the high-nickel ternary positive electrode materials, so that the hydrophobic alkyl groups are exposed to form a hydrophobic protective coating, which changes the inherent hydrophilic properties of the oxide substrate, reduces the surface energy and water absorption capacity of the high-nickel ternary positive electrode materials, alleviates the deterioration process of the materials in the air, increases the storage stability of the materials in a high humidity environment, improves the processing performance of the materials, relaxes the humidity requirements, and reduces the material processing costs.
  • the hydrophobic groups exposed by the modified positive electrode materials have enhanced affinity with the hydrophobic electrolyte used in battery assembly, and the electrolyte infiltration characteristics are improved, thereby affecting the component structure of the positive electrode electrolyte layer during battery operation, and improving the battery discharge capacity and cycle performance.
  • the present invention first hydrolyzes the alkyl trialkoxy group and then uses lithium hydroxide for neutralization reaction to obtain alkyl lithium silicate with good water solubility. Compared with ordinary organosilicon hydrophobic modifiers, no other organic solvents or dispersants are needed.
  • the prepared alkyl lithium silicate has good water solubility and strong reactivity, and can quickly hydrophobically modify the high-nickel ternary positive electrode material, so that the modification treatment time can be greatly shortened.
  • the alkyl lithium silicate itself contains Li + , it can provide a lithium source and is strongly alkaline, which can reduce the loss of internal lattice lithium caused by the high-nickel ternary positive electrode material during the aqueous solution treatment process and supplement the lithium source, which helps to maintain the electrical properties of the material itself and avoids the introduction of other alkali metals.
  • the alkyl lithium silicate provided by the present invention has good water solubility and is a water-based silane waterproof modifier.
  • the alkyl lithium silicate solution provided by the present invention can avoid the use of organic reagents compared with traditional organic silane coupling agents, has strong reaction activity, saves time and production costs, improves the safety of the modification process, and has a wider range of applications.
  • the preparation method of alkyl lithium silicate provided by the present invention is simple and efficient, does not require ion exchange, has strong operability, mild reaction conditions, and is relatively environmentally friendly; the prepared alkyl lithium silicate has good water solubility and high reactivity. Stronger and more applicable.
  • FIG1 is a SEM image of the modified high-nickel ternary positive electrode material of Example 1 of the present invention.
  • FIG. 2 is a comparison of the cycle performance of Examples 1, 2, and 5 of the present invention and Comparative Example 1.
  • a method for surface modification of a high-nickel ternary cathode material is as follows:
  • FIG1 is a SEM image of the modified high-nickel ternary positive electrode material of this embodiment.
  • a layer of film-like material can be found uniformly covering the surface of the particles.
  • a method for surface modification of a high-nickel ternary cathode material is as follows:
  • a method for surface modification of a high-nickel ternary cathode material is as follows:
  • a method for surface modification of a high-nickel ternary cathode material is as follows:
  • a method for surface modification of a high-nickel ternary cathode material is as follows:
  • a method for surface modification of a high-nickel ternary cathode material is as follows:
  • a method for surface treatment of a high-nickel ternary positive electrode material is different from Example 2 in that: Comparative Example 1 does not use a lithium methyl silicate solution for modification, and the specific process is as follows:
  • Lithium ion button cells were assembled in an argon atmosphere glove box (H 2 O ⁇ 0.1 ppm, O 2 ⁇ 0.1 ppm).
  • the high nickel ternary positive electrode materials, conductive agents, and binders prepared in the examples and comparative examples were mixed at 90: 5:5 was mixed evenly, nitrogen-methylpyrrolidone solvent was added and stirred to form a slurry, and then coated. After baking at 110°C for 2 hours, the sheet was punched, and it was dried again in a vacuum oven at 105°C for 4 hours.
  • the button battery was assembled.
  • the electrolyte was LiPF 6 dissolved in a mixed solvent of ethylene carbonate and diethyl carbonate.
  • the diaphragm was glass fiber.
  • the cycle performance test used a fully electric button battery, replaced the lithium metal negative electrode with a carbon material, and continued to test the battery cycle stability at 1C after one cycle at 0.1C.
  • Table 1 shows the residual lithium compounds and first-cycle electrical properties of Comparative Example 1 and Examples 1, 2, 3, 4, 5, and 6, wherein the residual lithium compounds are measured by acid-base titration, and the first-cycle electrical performance data are obtained by testing with the Blue Electric Battery Testing System equipment.
  • the first cycle charge and discharge capacity of the battery is improved in the embodiment.
  • the high-nickel ternary positive electrode material is treated with an aqueous solution, in addition to washing away the residual lithium compounds, the lithium in the lattice will also be washed out, which is prone to "overwashing" and reduces the charge and discharge capacity of the material.
  • the alkyl lithium silicate prepared by the present invention has strong alkalinity. In the process of aqueous solution modification of the material, in addition to forming a hydrophobic layer on the surface of the material, it can also effectively inhibit the loss of lattice lithium inside the material particles.
  • this method will inhibit the dissolution loss of residual lithium compounds on the surface, making the residual lithium compound content of the material relatively high, due to the presence of the surface hydrophobic layer, even if the residual lithium is high, it will not reduce the material performance, and the hydrophobic layer It can enhance its affinity with the electrolyte, improve the electrolyte wetting characteristics, and have a certain benefit effect on the cyclability of the material.
  • FIG2 is a comparison of the cycle performance of Examples 1, 2, and 5 with the comparative example. It can be found from FIG2 that, relative to Comparative Example 1, Examples 1, 2, and 5 improve the discharge capacity and cycle performance of the high-nickel ternary positive electrode material. After 170 cycles under 1C conditions, the capacity retention rate of Comparative Example 1 is 77.96%, and the capacity retention rates of Examples 1, 2, and 5 are 84.06%, 81.34%, and 80.72%, respectively.

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Abstract

本发明公开了一种高镍三元正极材料表面改性的方法及其应用，先制备烷基硅酸锂溶液，采用喷雾法或固液共混法将所述烷基硅酸锂溶液与高镍三元正极材料混合进行反应，再经干燥热处理后得到改性后的高镍三元正极材料。本发明将烷基硅酸锂应用到高镍三元正极材料的改性过程中，烷基硅酸锂本身的亲水含氧基团可以与高镍三元正极材料的亲水含氧官能团发生反应，使得疏水烷基基团暴露，形成疏水保护涂层，降低高镍三元正极材料的表面能和材料吸水能力；疏水基团与电池组装所使用的疏水电解质的亲和性增强，电解液浸润特性提升，进而提升电池放电容量和循环性能。

Description

高镍三元正极材料表面改性的方法及其应用 技术领域
本发明属于锂离子电池技术领域，具体涉及一种高镍三元正极材料表面改性的方法及其应用。
背景技术
发展新能源汽车是有效应对能源和环境挑战的重要举措。电池作为动力来源，已成为新能源电动汽车的主要发展方向。进一步提高电池的能量和功率密度，延长电池的使用寿命，缩短电池的充电时间，提高电池的安全性，降低电池的成本是新能源技术发展的主题和趋势。锂离子电池由于综合性能最好，仍然是动力电池的主流产品。研制高电压、高容量的正极材料已成为进一步提高电池能量密度的主要途径。
三元层状氧化物正极材料成本适中、比容量高、过渡金属比例可在一定范围内调节，在长续航动力电池领域广泛应用。其中，高镍三元正极材料在能量密度上有其独有的优势。然而较差的循环和热性能也限制了其应用。此外，随着镍含量提升，残碱量逐渐增大，材料本身的空气敏感问题加剧。为应对这一挑战，各种掺杂/包覆策略被用来改变高镍材料的体相结构或表界面性质，其中，疏水改性能够改变材料表面固有的亲水特性，使得材料的吸湿性降低，在缓解材料变质过程中发挥重要作用。
烷基硅酸盐是一类被广泛应用于建筑防水领域的表面改性材料，其具有水溶性好、与基材结合力强、防水性和耐候性优异等特点，常用于混凝土等建材的防水处理，适用范围广。市面上使用的烷基硅酸盐包括甲基硅酸钠、甲基硅酸钾、乙基硅酸钠、苯基硅酸钠等，这些产品在直接用于防水改性时往往会残留有部分钠钾离子，在直接应用到锂电池材料过程中往往不易除去，不利于材料电化学性能的发挥。
现有方法中多采用有机硅材料作为疏水改性剂对正极材料进行表面改性，但这些方法所用的溶剂多为有机试剂，成本较高，即使有些方法可选的溶剂包括水，也会存在有机硅材料在水溶液中水解反应时间过长的问题，而高镍三元正极材料无法长期在水溶液 中处理，因为时间越长，材料晶格内的锂损耗越严重，会严重削弱材料的电性能。
发明内容
本发明旨在至少解决上述现有技术中存在的技术问题之一。为此，本发明提出一种高镍三元正极材料表面改性的方法及其应用。
根据本发明的一个方面，提出了一种高镍三元正极材料表面改性的方法，包括以下步骤：
制备烷基硅酸锂溶液，采用喷雾法或固液共混法将所述烷基硅酸锂溶液与高镍三元正极材料混合进行反应，再经干燥热处理后得到改性后的高镍三元正极材料；
所述喷雾法是在高镍三元正极材料保持搅拌状态下将所述烷基硅酸锂溶液喷雾到材料表面发生化学反应，喷雾后所得湿料进行所述干燥热处理；
所述固液共混法是将高镍三元正极材料分散到所述烷基硅酸锂溶液中进行反应，固液分离后所得固体进行所述干燥热处理。
当通过喷雾法进行混合时，采用高速混料设备，在高镍三元正极材料保持高速运动状态下将烷基硅酸锂溶液喷洒到材料表面发生化学反应；当通过固液共混法(湿法)使烷基硅酸锂与高镍三元正极材料反应时，烷基硅酸锂作为一种水溶液添加剂，直接与高镍三元正极材料表面进行反应达到疏水改性效果。
在本发明的一些实施方式中，所述高镍三元正极材料为镍钴锰酸锂，其化学式为LiNixCoyMnzO2，其中x+y+z＝1，且0.8≤x＜1，0＜y≤0.1，0＜z≤0.1。
在本发明的一些实施方式中，所述烷基硅酸锂溶液的制备方法为：将烷基三烷氧基硅烷、酸类催化剂和水混合进行水解反应，得到烷基硅酸溶液，将所述烷基硅酸溶液与氢氧化锂溶液混合反应，固液分离，得到所述烷基硅酸锂溶液。进一步地，所述水解反应的温度为25-50℃，反应的时间0.1-5h。进一步地，所述烷基硅酸溶液中烷基硅酸与氢氧化锂溶液中氢氧化锂的摩尔比为1：(0.8-2)。进一步地，所述氢氧化锂溶液的质量浓度为10-120g/L。进一步地，所述烷基硅酸溶液与氢氧化锂溶液混合反应的时间为5-30min。进一步地，所述固液分离的方式为过滤或真空辅助抽滤。需要说明的是，固 液分离出来的固体一般是过度水解聚合生成的不溶性烷基硅酸盐，虽然出现的不溶性烷基硅酸盐的量比较少，但仍然需要过滤去除以避免其对产物的干扰。
在本发明的一些实施方式中，所述烷基硅酸锂溶液为甲基硅酸锂溶液、乙烯基硅酸锂溶液、丙基硅酸锂溶液、辛基硅酸锂溶液、苯基硅酸锂溶液或十二烷基硅酸锂溶液中的至少一种。本发明中，可根据需要，选择对应的烷基三烷氧基硅烷来制备相应的烷基硅酸锂。优选的，所述烷基硅酸锂溶液为甲基硅酸锂溶液或丙基硅酸锂溶液。进一步地，当制备甲基硅酸锂溶液时，选用的烷基三烷氧基硅烷优选为甲基三甲氧基硅烷或甲基三乙氧基硅烷。当制备丙基硅酸锂溶液时，选用的烷基三烷氧基硅烷优选为丙基三甲氧基硅烷。
在本发明的一些实施方式中，所述烷基三烷氧基硅烷和水的摩尔比为1：(1-5)；所述酸类催化剂的用量为所述烷基三烷氧基硅烷重量的0.1％-2％。
在本发明的一些实施方式中，所述酸类催化剂为盐酸、醋酸或植酸中的至少一种。
在本发明的一些实施方式中，所述烷基硅酸锂溶液中的烷基硅酸锂与高镍三元正极材料的质量比为(0.1-3)：100。
在本发明的一些实施方式中，所述喷雾法中，所述搅拌的转速为600-1500rpm。
在本发明的一些实施方式中，所述喷雾法中，所述烷基硅酸锂溶液喷雾的时间为5-15min。
在本发明的一些实施方式中，所述喷雾法中，所述喷雾的速率为10-30mL/min。
在本发明的一些实施方式中，所述固液共混法中，高镍三元正极材料与烷基硅酸锂溶液反应的时间为3-30min。
在本发明的一些实施方式中，所述固液共混法中，高镍三元正极材料与烷基硅酸锂溶液的反应在100-300rpm的搅拌转速下进行。
在本发明的一些实施方式中，所述固液共混法中，所述高镍三元正极材料分散到所述烷基硅酸锂溶液中的方式为以下任选一种：(1)将烷基硅酸锂溶液稀释到5-50g/L，再将高镍三元正极材料加入到稀释后的烷基硅酸锂溶液中；(2)将高镍三元正极材料加 入到水中进行分散，再加入烷基硅酸锂溶液，所得混合物料中烷基硅酸锂的浓度为5-50g/L。
在本发明的一些实施方式中，所述干燥热处理的温度为110-150℃，时间为8-24h。
在本发明的一些实施方式中，所述干燥热处理后还包括过筛的操作，过筛的筛网目数为100-400目。
本发明还提供所述的方法在制备锂离子电池中的应用。
根据本发明的一种优选的实施方式，至少具有以下有益效果：
1.本发明将烷基硅酸锂应用到高镍三元正极材料的改性过程中，烷基硅酸锂本身的亲水含氧基团(羟基-OH，含氧阴离子Si-O-Li+)可以与高镍三元正极材料的亲水含氧官能团(-OH，-O-)发生反应，使得疏水烷基基团暴露，形成疏水保护涂层，改变了氧化物基材固有的亲水特性，降低高镍三元正极材料的表面能和材料吸水能力，缓解材料在空气中的变质过程，增加材料在高湿度环境下的存储稳定性，提升了材料的加工性能，放宽湿度要求，降低材料加工成本。此外，改性正极材料暴露出的疏水基团与电池组装所使用的疏水电解质的亲和性增强，电解液浸润特性提升，进而影响电池运行过程中正极电解质层的组分结构，提升电池放电容量和循环性能。
2.本发明先将烷基三烷氧基水解再用氢氧化锂进行中和反应制得水溶性好的烷基硅酸锂，与普通的有机硅疏水改性剂相比，无需使用其它有机溶剂或分散剂，所制备的烷基硅酸锂水溶性好，反应性强，能够快速对高镍三元正极材料进行疏水改性，使改性处理时间能够大幅缩短。此外，由于烷基硅酸锂本身含有Li+，能够提供锂源，呈强碱性，能够降低高镍三元正极材料在水溶液处理过程中造成的内部晶格锂的损失和补充锂源，有助于维持材料本身的电性能，还避免了其它碱金属的引入。
3.本发明提供的烷基硅酸锂水溶性好，是水性硅烷防水改性剂。在进行防水改性过程中，本发明提供的烷基硅酸锂溶液与传统有机硅烷偶联剂相比，可以避免有机试剂的使用，反应活性强，节约时间和生产成本，提高改性过程的安全性，适用范围更广。
4.优选的，本发明提供的烷基硅酸锂的制备方法，其过程简单高效，无需进行离子交换，可操作性强，反应条件温和，相对环保；制备出的烷基硅酸锂水溶性好，反应性 强，适用范围更广。
附图说明
下面结合附图和实施例对本发明做进一步的说明，其中：
图1为本发明实施例1改性后高镍三元正极材料的SEM图；
图2为本发明实施例1、2、5与对比例1的循环性能对比。
具体实施方式
以下将结合实施例对本发明的构思及产生的技术效果进行清楚、完整地描述，以充分地理解本发明的目的、特征和效果。显然，所描述的实施例只是本发明的一部分实施例，而不是全部实施例，基于本发明的实施例，本领域的技术人员在不付出创造性劳动的前提下所获得的其他实施例，均属于本发明保护的范围。
实施例1
一种高镍三元正极材料表面改性的方法，具体过程为：
1)取136g甲基三甲氧基硅烷溶于54g去离子水与0.3g浓盐酸的混合液，在30℃保温条件下反应1h；然后100rpm的搅拌状态下加入200mL质量浓度为120g/L的氢氧化锂溶液，反应10min后真空抽滤，得到甲基硅酸锂溶液。
2)取2kg高镍三元正极材料LiNi0.92Co0.06Mn0.02O2加入到川田混料机，在800rpm转速下将上述甲基硅酸锂溶液52mL喷洒到高镍三元正极材料表面，喷雾速率为10mL/min，喷雾时间为8min，喷雾完后继续搅拌5min，然后在鼓风干燥箱中120℃干燥12h，最后用400目筛网过筛即得改性后的高镍三元正极材料。
图1为本实施例改性后高镍三元正极材料的SEM图，图中可以发现一层膜状物质均匀覆盖在颗粒表面。
实施例2
一种高镍三元正极材料表面改性的方法，具体过程为：
1)取136g甲基三甲氧基硅烷溶于54g去离子水与0.6g的50wt％植酸混合液，在30℃保温条件下反应1h；然后100rpm的搅拌转速下加入200mL质量浓度为120g/L的 氢氧化锂溶液，反应10min后真空抽滤，得到甲基硅酸锂溶液。
2)在水洗反应釜中加入4.8L去离子水，加入200mL上述甲基硅酸锂溶液，开启搅拌，转速为200rpm，之后快速加入10kg高镍三元正极材料LiNi0.92Co0.06Mn0.02O2，继续搅拌3min，然后离心去除溶剂，收集的固体在120℃烘箱干燥12h，最后400目筛网过筛得改性后的高镍三元正极材料。
实施例3
一种高镍三元正极材料表面改性的方法，具体过程为：
1)取164g丙基三甲氧基硅烷溶于20g去离子水与0.3g浓盐酸的混合液，在40℃保温条件下反应2h；然后100rpm的搅拌状态下加入含有200mL质量浓度为120g/L的氢氧化锂溶液，反应10min后真空抽滤，得到丙基硅酸锂溶液。
2)取3kg高镍三元正极材料LiNi0.92Co0.06Mn0.02O2加入到川田混料机，在800rpm转速下将上述丙基硅酸锂溶液80mL喷洒到高镍三元正极材料表面，喷雾速率为20mL/min，喷雾时间为10min，喷雾完后继续搅拌3min，然后在鼓风干燥箱中120℃烘箱干燥12h，最后用400目筛网过筛即得到改性后的高镍三元正极材料。
实施例4
一种高镍三元正极材料表面改性的方法，具体过程为：
1)取136g甲基三甲氧基硅烷溶于54g去离子水与0.3g浓盐酸的混合液，在35℃保温条件下反应0.5h；然后150rpm的搅拌状态下加入含有400mL质量浓度为120g/L的氢氧化锂溶液，反应10min后真空抽滤，得到甲基硅酸锂溶液。
2)取2kg高镍三元正极材料LiNi0.92Co0.06Mn0.02O2加入到川田混料机，在800rpm转速下将上述甲基硅酸锂溶液53mL喷洒到高镍三元正极材料表面，喷雾速率为10mL/min，喷雾时间为8min，喷雾完后继续搅拌5min，然后在鼓风干燥箱中120℃烘箱干燥12h，最后用400目筛网过筛即得到改性后的高镍三元正极材料。
实施例5
一种高镍三元正极材料表面改性的方法，具体过程为：
1)取136g甲基三甲氧基硅烷溶于54g去离子水与0.3g浓盐酸的混合液，在30℃保温条件下反应1h；然后100rpm的搅拌状态下加入含有200mL质量浓度为120g/L的氢氧化锂溶液，反应10min后真空抽滤，得到甲基硅酸锂溶液。
2)取500g高镍三元正极材料LiNi0.92Co0.06Mn0.02O2分散到500mL去离子水中，保持去离子水温度在5℃，300rpm转速下缓慢滴加上述甲基硅酸锂溶液40mL，继续搅拌反应5min，真空辅助抽滤得到固体，在120℃烘箱干燥12h，最后用400目筛网过筛得到改性后的高镍三元正极材料。
实施例6
一种高镍三元正极材料表面改性的方法，具体过程为：
1)取178g甲基三乙氧基硅烷分散于54g去离子水与0.5g浓盐酸的混合液中，高速搅拌混合，在100rpm转速和50℃保温条件下继续反应3h；然后加入含有200mL质量浓度为120g/L的氢氧化锂溶液，反应30min后真空抽滤，得到甲基硅酸锂溶液。
2)取2kg高镍三元正极材料LiNi0.92Co0.06Mn0.02O2加入到川田混料机，在800rpm转速下将上述甲基硅酸锂溶液60mL喷洒到高镍三元正极材料表面，喷雾速率为10mL/min，喷雾时间为8min，喷雾完后继续搅拌5min，然后在鼓风干燥箱中120℃烘箱干燥12h，最后用400目筛网过筛即得到改性后的高镍三元正极材料。
对比例1
一种高镍三元正极材料表面处理的方法，与实施例2的区别在于：对比例1不采用甲基硅酸锂溶液改性，具体过程为：
在水洗反应釜中加入5L去离子水，开启搅拌，然后快速加入10kg高镍三元正极材料LiNi0.92Co0.06Mn0.02O2，继续搅拌3min，然后离心去除去离子水溶剂，120℃烘箱干燥12h，最后400目筛网过筛得到湿法处理但未改性的高镍三元正极材料。
试验例
电池组装与测试：在氩气气氛手套箱内(H2O＜0.1ppm，O2＜0.1ppm)进行锂离子扣式电池组装。将实施例和对比例制备的高镍三元正极材料，导电剂，粘结剂按照90： 5：5混合均匀，加入氮-甲基吡咯烷酮溶剂搅拌形成浆料后进行涂布，110℃下烘2小时后进行冲片，在105℃真空烘箱下再次干燥4小时，组装扣式电池，电解液采用LiPF6溶于碳酸乙烯酯和碳酸二乙酯混合溶剂，隔膜为玻璃纤维，负极采用锂金属片，组装好后静置3小时进行电池首圈测试，测试条件为25℃测试0.1C下的充放电容量及首效，1C＝210mAh/g。循环性能测试采用全电扣式电池，将锂金属负极更换为碳材料，在0.1C下循环一圈后继续在1C下测试电池循环稳定性。
表1为对比例1与实施例1、2、3、4、5、6的残余锂化合物及首圈电性能，其中残余锂化合物是通过酸碱滴定测得，首圈电性能数据是通过蓝电电池测试系统设备测试得到。
表1残余锂化合物含量及首圈电性能对比
由表1可知，实施例中对电池首圈充放电容量有所提升，高镍三元正极材料在用水溶液进行处理时，除了能够洗去残余锂化合物，晶格内的锂也会被洗出，容易发生“过洗”，降低材料的充放电容量，而本发明制备的烷基硅酸锂碱性强，在水溶液改性材料过程中除了能够在材料表面形成一层疏水层，还能够有效抑制材料颗粒内部晶格锂的损失。虽然该方法会抑制表面残余锂化合物的溶解损耗，使得材料的残余锂化合物含量相对较高，但由于表面疏水层的存在，即使残余锂较高也不会降低材料性能，而且疏水层 能够增强其与电解质的亲和性，提升电解液浸润特性，对材料的循环性产生一定增益效果。
图2为实施例1、2、5与对比例的循环性能对比，从图2可以发现，相对于对比例1，实施例1、2、5提高了高镍三元正极材料的放电容量以及循环性能，在1C条件下循环170圈后，对比例1容量保持率为77.96％，实施例1、2、5的容量保持率分别为84.06％、81.34％、80.72％。
上面结合附图对本发明实施例作了详细说明，但是本发明不限于上述实施例，在所属技术领域普通技术人员所具备的知识范围内，还可以在不脱离本发明宗旨的前提下作出各种变化。此外，在不冲突的情况下，本发明的实施例及实施例中的特征可以相互组合。

Claims (10)

  1. 一种高镍三元正极材料表面改性的方法，其特征在于，包括以下步骤：
    制备烷基硅酸锂溶液，采用喷雾法或固液共混法将所述烷基硅酸锂溶液与高镍三元正极材料混合进行反应，再经干燥热处理后得到改性后的高镍三元正极材料；
    所述喷雾法是在高镍三元正极材料保持搅拌状态下将所述烷基硅酸锂溶液喷雾到材料表面发生化学反应，喷雾后所得湿料进行所述干燥热处理；
    所述固液共混法是将高镍三元正极材料分散到所述烷基硅酸锂溶液中进行反应，固液分离后所得固体进行所述干燥热处理。
  2. 根据权利要求1所述的方法，其特征在于，所述烷基硅酸锂溶液的制备方法为：将烷基三烷氧基硅烷、酸类催化剂和水混合进行水解反应，得到烷基硅酸溶液，将所述烷基硅酸溶液与氢氧化锂溶液混合反应，固液分离，得到所述烷基硅酸锂溶液。
  3. 根据权利要求1或2所述的方法，其特征在于，所述烷基硅酸锂溶液为甲基硅酸锂溶液、乙烯基硅酸锂溶液、丙基硅酸锂溶液、辛基硅酸锂溶液、苯基硅酸锂溶液或十二烷基硅酸锂溶液中的至少一种。
  4. 根据权利要求2所述的方法，其特征在于，所述烷基三烷氧基硅烷和水的摩尔比为1：(1-5)；所述酸类催化剂的用量为所述烷基三烷氧基硅烷重量的0.01％-2％。
  5. 根据权利要求2所述的方法，其特征在于，所述酸类催化剂为盐酸、醋酸或植酸中的至少一种。
  6. 根据权利要求1所述的方法，其特征在于，所述烷基硅酸锂溶液中的烷基硅酸锂与高镍三元正极材料的质量比为(0.1-3)：100。
  7. 根据权利要求1所述的方法，其特征在于，所述喷雾法中，所述烷基硅酸锂溶液喷雾的时间为5-15min。
  8. 根据权利要求1所述的方法，其特征在于，所述固液共混法中，高镍三元正极材料与烷基硅酸锂溶液反应的时间为3-30min。
  9. 根据权利要求1所述的方法，其特征在于，所述干燥热处理的温度为110-150℃， 时间为8-24h。
  10. 如权利要求1-9中任一项所述的方法在制备锂离子电池中的应用。
PCT/CN2023/085570 2023-03-31 2023-03-31 高镍三元正极材料表面改性的方法及其应用 Ceased WO2024197844A1 (zh)

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