High-nickel ternary positive electrode precursor material as well as preparation method and application thereof

Abstract

The invention provides a high-nickel ternary positive electrode precursor material as well as a preparation method and application thereof. The preparation method comprises the following steps: adding a nickel-cobalt-manganese mixed salt solution, a precipitant solution and a complexing agent solution in a parallel flow manner, and carrying out a co-precipitation reaction to obtain reaction slurry of a positive electrode precursor base material; the reaction slurry and the silicon source solution are mixed, hydrolysis coating is carried out, the high-nickel ternary positive electrode precursor material is obtained, and the high-nickel ternary positive electrode precursor material comprises a positive electrode precursor base material and a silicon dioxide coating layer coating the surface of the positive electrode precursor base material. According to the preparation method, the positive electrode precursor base material is prepared firstly, then silicon source hydrolysis coating is performed, and a silicon dioxide coating layer which is compact in coating, uniform in distribution and complete in coating is obtained, so that the cycling stability and the high-temperature performance of the high-nickel positive electrode material prepared from the precursor are improved, surface side reactions are reduced, and the performance of the high-nickel positive electrode material is improved. Particularly, the cycle performance and the high-temperature performance of the high-nickel positive electrode material under high voltage are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries and relates to a high-nickel ternary positive electrode precursor material and a preparation method and application thereof. Background Art

[0002] With the widespread use of lithium-ion batteries, the development of high-performance electrode materials has become a research hotspot. High-nickel ternary precursors (wherein the molar proportion of nickel in the main metal element is ≥80%) are widely used as battery positive electrode materials due to their high capacity and low cost, especially further ultra-high nickel positive electrode materials (wherein the molar proportion of nickel in the main metal element is ≥90%). However, such materials are prone to structural instability and surface side reactions under high temperature and high voltage (≥4.3V) conditions, affecting the cycle life and safety of the battery.

[0003] In order to solve this problem, the improvement methods in the existing technology include element doping, nano-sizing, concentration gradient control and electrolyte matching regulation. Element doping can significantly improve the electrochemical performance and cycle stability of the positive electrode material, but the doping process will have the risk of over-doping, uniformity problems and cost problems. The use of nano-sizing technology can increase the specific surface area of ​​the material, promote the rapid diffusion of lithium ions, and improve the high-rate discharge performance, but the synthesis conditions are difficult to control. Although the concentration gradient can improve battery performance and stability, the preparation process is difficult, it is difficult to control uniformity and the cost will increase significantly, which seriously limits its large-scale production. Improving the electrolyte has significant advantages in improving the performance of lithium-ion batteries, but it is also accompanied by challenges in cost, compatibility and environment.

[0004] Therefore, how to improve the structural stability of high-nickel positive electrode materials under high temperature and high voltage, improve their cycle performance, and inhibit side reactions are technical problems that need to be solved urgently. Summary of the Invention

[0005] In response to the shortcomings of the prior art, the present invention aims to provide a high-nickel ternary cathode precursor material, its preparation method, and its use. The present invention first prepares a cathode precursor matrix material, then hydrolyzes and coats it with a silicon source to obtain a dense, evenly distributed, and completely covered silica coating. This improves the cycle stability and high-temperature performance of the high-nickel cathode material obtained from the precursor material, reduces the occurrence of surface side reactions, and particularly improves the cycle performance and high-temperature performance of the high-nickel cathode material at high voltage.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a high-nickel ternary positive electrode precursor material, the preparation method comprising the following steps:

[0008] Adding a nickel-cobalt-manganese mixed salt solution, a precipitant solution, and a complexing agent solution in parallel to perform a coprecipitation reaction to obtain a reaction slurry of a positive electrode precursor matrix material;

[0009] The reaction slurry and the silicon source solution are mixed and hydrolyzed and coated to obtain the high-nickel ternary positive electrode precursor material. The high-nickel ternary positive electrode precursor material includes a positive electrode precursor base material and a silicon dioxide coating layer coated on the surface of the positive electrode precursor base material.

[0010] In the preparation method provided by the present invention, a positive electrode precursor matrix material is first prepared, and then a silicon source is used for hydrolysis and coating to obtain a silicon dioxide coating layer. On the one hand, co-precipitation and coating are carried out step by step, and parameters are independently regulated, which is more suitable for large-scale production; on the other hand, the step-by-step preparation can accurately control the SiO2 distribution, avoid the deterioration of the coating effect caused by incomplete hydrolysis of the silicon source, reduce the morphological damage to the precursor material, improve the uniformity, and achieve ultra-thin and uniform coating of the silicon dioxide coating layer, complete coverage and dense coating layer, thereby improving the cycle stability and high-temperature performance of the high-nickel positive electrode material obtained from the precursor material, effectively inhibiting the dissolution of transition metals, and reducing the occurrence of surface side reactions, especially improving the cycle performance and high-temperature performance of the high-nickel positive electrode material under high voltage.

[0011] In the present invention, if the silicon source is added during the co-precipitation reaction, problems such as uneven coating, incomplete hydrolysis of the silicon source, and poor density of the coating layer will occur; in addition, premature hydrolysis of the silicon source will not only destroy the co-precipitation process, but also the generated SiO2 will compete with the precursor matrix for heterogeneous nucleation. If the silicon source contains halogen, simultaneous coating may even cause the risk of introducing metal impurities.

[0012] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0013] Preferably, the median particle size D50 of the positive electrode precursor matrix material in the reaction slurry is 2.5μm to 4μm, for example, 2.5μm, 2.8μm, 3μm, 3.3μm, 3.5μm, 3.8μm or 4μm, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0014] Small-particle positive electrode precursor matrix materials have a large specific surface area and are more difficult to coat. The preparation method provided by the present invention can reduce the degree of morphological damage, improve the uniformity of coating, and also reduce precursor morphological damage and reduce impurity risks.

[0015] Preferably, the silicon source in the silicon source solution has a silicon-halogen bond and / or a silicon-alkoxy bond.

[0016] Preferably, the silicon source includes any one of silicon tetrachloride, methyl orthosilicate or ethyl orthosilicate, or a combination of at least two of them.

[0017] The silicon source provided by the present invention can be hydrolyzed in an alkaline environment to obtain a silicon dioxide material.

[0018] Preferably, the concentration of the silicon source solution is 0.05mol / L to 1.5mol / L, for example, 0.05mol / L, 0.1mol / L, 0.2mol / L, 0.3mol / L, 0.4mol / L, 0.5mol / L, 0.6mol / L, 0.7mol / L, 0.8mol / L, 0.9mol / L, 1mol / L, 1.1mol / L, 1.2mol / L, 1.3mol / L, 1.4mol / L or 1.5mol / L, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] In the present invention, the concentration of the silicon source solution is regulated to be 0.05 mol / L to 1.5 mol / L, which is more conducive to controlling the hydrolysis rate, avoiding excessively rapid deposition of SiO2 resulting in uneven coating or particle agglomeration, while ensuring sufficient silicon source coverage and improving the coating effect.

[0020] Preferably, the pH value of the hydrolysis coating is 8 to 10, such as 8, 8.3, 8.5, 8.8, 9, 9.3, 9.5, 9.8 or 10, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] In the present invention, the pH value of the hydrolysis coating is regulated to 8-10, which can not only realize the hydrolysis reaction of the silicon source under mild conditions to obtain silicon dioxide, but also avoid the surface morphology of the positive electrode precursor matrix material from being destroyed.

[0022] Preferably, the temperature of the hydrolysis coating is 40°C to 80°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] Preferably, the thickness of the silica coating layer is 1 nm to 20 nm, for example, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm or 20 nm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] The silicon dioxide coating layer formed by hydrolysis coating in the present invention is thin and uniformly coated. The relatively thin coating layer thickness of 1 nm to 20 nm can better achieve a balance between interface stability and ion conduction, structural integrity protection and sintering compatibility.

[0025] Preferably, the voids in the positive electrode precursor matrix material are filled with silicon dioxide.

[0026] The present invention first prepares a positive electrode precursor matrix material, which is a secondary particle formed by primary particles, and then hydrolyzes and coats the silicon source solution. The silicon source solution can also fill the gaps in the positive electrode precursor matrix material, thereby further improving its structural stability and avoiding the generation of microcracks.

[0027] Preferably, the concentration of the nickel-cobalt-manganese mixed salt solution is 80 g / L to 120 g / L, for example, 80 g / L, 90 g / L, 100 g / L, 110 g / L or 120 g / L, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0028] Preferably, in the nickel-cobalt-manganese mixed salt solution, the proportion of nickel in the total molar amount of nickel-cobalt-manganese is ≥80%, for example, 80%, 83%, 85%, 88%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%, etc., preferably ≥90%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0029] The preparation method provided by the present invention is more effective when used in the preparation process of high-nickel, or even ultra-high-nickel, positive electrode precursor materials.

[0030] Preferably, the mass concentration of the precipitant solution is 28% to 32%, such as 28%, 29%, 30%, 31% or 32%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] Preferably, the mass concentration of the precipitant solution is 10% to 20%, for example, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] Preferably, the feed rate of the nickel-cobalt-manganese mixed salt solution is 6 L / h to 10 L / h, for example, 6 L / h, 7 L / h, 8 L / h, 9 L / h or 10 L / h, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0033] Preferably, the feed rate of the precipitant solution is 2 L / h to 3 L / h, such as 2 L / h or 3 L / h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] Preferably, the concentration of the complexing agent solution is 0.6L / h to 1L / h, such as 0.6L / h, 0.7L / h, 0.8L / h, 0.9L / h or 1L / h, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0035] It is understandable that the types of salts, specific species of precipitants and complexing agents in the nickel-cobalt-manganese mixed salt solution of the present invention are all conventional technical solutions, and those skilled in the art can make adaptive selections and adjustments based on actual needs.

[0036] Optionally, the salt in the nickel-cobalt-manganese mixed salt includes at least one of sulfate, nitrate, chloride or acetate.

[0037] Optionally, the precipitant includes at least one of potassium hydroxide, sodium hydroxide, sodium carbonate or sodium bicarbonate.

[0038] Optionally, the complexing agent includes at least one of ammonia water, citric acid or ethylenediaminetetraacetic acid.

[0039] Preferably, the reaction temperature of the coprecipitation reaction is 40°C to 60°C, such as 40°C, 45°C, 50°C, 55°C or 60°C, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0040] Preferably, the stirring speed of the coprecipitation reaction is 200 rpm to 400 rpm, for example, 200 rpm, 230 rpm, 250 rpm, 280 rpm, 300 rpm, 330 rpm, 350 rpm, 380 rpm or 400 rpm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] Preferably, the pH value of the coprecipitation reaction is 10-12, for example, 10, 10.3, 10.5, 10.8, 11, 11.3, 11.5, 11.8 or 12, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] It should also be noted that:

[0043] In the present invention, before adding the raw materials in parallel, the reaction base liquid can be added into the reaction container in advance.

[0044] The reaction base liquid includes water, a precipitant and a complexing agent. The concentration of the complexing agent in the reaction base liquid is 4g / L to 8g / L, for example, 4g / L, 5g / L, 6g / L, 7g / L or 8g / L, etc. The temperature of the reaction base liquid is 40°C to 60°C, for example, 40°C, 45°C, 50°C, 55°C or 60°C, etc. The pH value of the reaction base liquid is 10 to 12, for example, 10, 10.3, 10.5, 10.8, 11, 11.3, 11.5, 11.8 or 12, etc.

[0045] The coprecipitation reaction is carried out in a protective atmosphere, that is, a protective gas such as nitrogen or an inert gas (helium, argon, etc.) is introduced before and during the reaction.

[0046] In addition, after the hydrolysis and coating are completed, the present invention sequentially carries out conventional treatment processes of aging, washing and drying, and the above-mentioned aging, washing and drying have methods, and those skilled in the art can make adaptive selections and adjustments based on the disclosure of the prior art.

[0047] In a second aspect, the present invention provides a high-nickel ternary positive electrode precursor material, which is prepared by the preparation method described in the first aspect.

[0048] In a third aspect, the present invention provides a high-nickel positive electrode material, which is obtained by mixing the high-nickel ternary positive electrode precursor material as described in the second aspect and a raw material including at least a lithium source and then sintering the mixture.

[0049] The high-nickel positive electrode material provided by the present invention is prepared from a high-nickel precursor positive electrode material, wherein the silicon dioxide coating layer and the silicon dioxide filled in the gaps of the positive electrode precursor matrix material can also react with the lithium source to generate lithium silicate, which is more conducive to interface engineering optimization, residual lithium neutralization effect, structural stabilization and kinetic performance improvement.

[0050] The present invention does not impose any special limitation on the specific process of preparing the positive electrode material from the precursor material. The present invention is applicable to all conventional technical solutions disclosed in the prior art and reasonably known to those skilled in the art.

[0051] For example, the preparation method of the high nickel positive electrode material includes:

[0052] The high-nickel positive electrode precursor material provided in the second aspect is mixed with a lithium source and sintered in an oxygen-containing atmosphere to obtain the high-nickel positive electrode precursor material.

[0053] Optionally, the lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium nitrate or lithium acetate.

[0054] Optionally, the oxygen-containing atmosphere includes an air atmosphere or an oxygen atmosphere.

[0055] Optionally, the sintering temperature can be 600-1000°C, for example, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C or 1000°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0056] In a fourth aspect, the present invention further provides a lithium-ion battery, comprising the high-nickel positive electrode material as described in the third aspect.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] In the preparation method provided by the present invention, a positive electrode precursor matrix material is first prepared, and then a silicon source is used for hydrolysis and coating to obtain a silicon dioxide coating layer. On the one hand, co-precipitation and coating are carried out step by step, and parameters are independently regulated, which is more suitable for large-scale production; on the other hand, the step-by-step preparation can accurately control the SiO2 distribution, avoid the deterioration of the coating effect caused by incomplete hydrolysis of the silicon source, reduce the morphological damage to the precursor material, improve the uniformity, and achieve ultra-thin and uniform coating of the silicon dioxide coating layer, complete coverage and dense coating layer, thereby improving the cycle stability and high-temperature performance of the high-nickel positive electrode material obtained from the precursor material, effectively inhibiting the dissolution of transition metals, and reducing the occurrence of surface side reactions, especially improving the cycle performance and high-temperature performance of the high-nickel positive electrode material under high voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is the SEM image of the positive electrode precursor matrix material obtained in step S1 in Example 1. DETAILED DESCRIPTION

[0060] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0061] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusions.

[0062] In the description of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0063] Example 1

[0064] This embodiment provides a high-nickel positive electrode precursor material, and the preparation method of the high-nickel positive electrode precursor material is as follows:

[0065] S1. Preparation of NCM precursor powder:

[0066] A nickel-cobalt-manganese sulfate solution with a concentration of 100 g / L (the molar ratio of nickel, cobalt and manganese is 0.91:0.03:0.06), a liquid alkali solution with a mass concentration of 30%, and an ammonia solution with a mass concentration of 15% are simultaneously added to a reactor containing a bottom liquid (the temperature of the bottom liquid is 50°C, and it consists of water, liquid alkali and ammonia water, wherein the pH value is 11.3 and the concentration of ammonia water is 6 g / L) at a feeding rate of 8 L / h, 2.5 L / h and 0.8 L / h, respectively. The coprecipitation reaction is carried out at a stirring rate of 380 r / min. During the reaction, the pH of the reaction system is controlled to be 11.8, the ammonia concentration is 6 g / L, and the temperature is 50°C. The particle size is continuously monitored. Before the particle size does not meet the requirements, the reaction process will use a high-efficiency concentrator to collect all the particles and return them to the reactor for continuous reaction and growth. When the particle size D50 reaches 3.3 μm, the feeding is stopped and the reaction is continued until the material reaction is complete to obtain the positive electrode precursor matrix material Ni 0.91 Co 0.03 Mn 0.06 (OH)2 reaction slurry.

[0067] S2: A 0.2 mol / L tetraethyl orthosilicate (TEOS) solution is added dropwise to the reaction slurry of S1, and a 10 nm SiO2 coating layer is formed on the surface of the positive electrode precursor matrix material through a hydrolysis-condensation reaction at a pH of 9 and a temperature of 60°C. The voids in the positive electrode precursor matrix material are also filled with silicon dioxide. After aging, washing and drying, the high nickel positive electrode precursor material is obtained.

[0068] Figure 1 The SEM image of the positive electrode precursor matrix material obtained in step S1 of Example 1 is shown. Figure 1 It can be seen that the precursor material provided by the present invention has a uniform particle size and certain gaps exist between the particles, which can achieve further filling of silicon dioxide.

[0069] Example 2

[0070] This embodiment provides a high-nickel positive electrode precursor material, and the preparation method of the high-nickel positive electrode precursor material is as follows:

[0071] S1. Preparation of NCM precursor powder:

[0072] A nickel-cobalt-manganese sulfate solution with a concentration of 120 g / L (the molar ratio of nickel, cobalt and manganese is 0.91:0.03:0.06), a liquid alkali solution with a mass concentration of 32%, and an ammonia solution with a mass concentration of 20% are simultaneously added to a reactor containing a bottom liquid (the temperature of the bottom liquid is 40°C, and it consists of water, liquid alkali and ammonia water, wherein the pH value is 10.5 and the concentration of ammonia water is 8 g / L) at a feeding rate of 6 L / h, 2 L / h and 0.6 L / h, respectively. A coprecipitation reaction is carried out at a stirring rate of 380 r / min. During the reaction, the pH of the reaction system is controlled to be 10.8, the ammonia concentration is 8 g / L, and the temperature is 40°C. The particle size is continuously monitored. Before the particle size does not meet the requirements, a high-efficiency concentrator is used in the reaction process to collect all the particles and return them to the reactor for continuous reaction and growth. When the particle size D50 reaches 2.5 μm, the feeding is stopped and the reaction is continued until the material reaction is complete to obtain the positive electrode precursor matrix material Ni 0.91 Co 0.03 Mn 0.06 (OH)2 reaction slurry.

[0073] S2: A 0.05 mol / L tetraethyl orthosilicate (TEOS) solution is added dropwise to the reaction slurry of S1, and a 1 nm SiO2 coating layer is formed on the surface of the positive electrode precursor matrix material through a hydrolysis-condensation reaction at a pH of 8 and a temperature of 40°C. The voids in the positive electrode precursor matrix material are also filled with silicon dioxide. After aging, washing and drying, the high nickel positive electrode precursor material is obtained.

[0074] Example 3

[0075] This embodiment provides a high-nickel positive electrode precursor material, and the preparation method of the high-nickel positive electrode precursor material is as follows:

[0076] S1. Preparation of NCM precursor powder:

[0077] A nickel-cobalt-manganese sulfate solution with a concentration of 80 g / L (the molar ratio of nickel, cobalt and manganese is 0.91:0.03:0.06), a liquid alkali solution with a mass concentration of 28%, and an ammonia solution with a mass concentration of 10% are simultaneously and concurrently added to a reactor containing a bottom liquid (the temperature of the bottom liquid is 60°C, and it consists of water, liquid alkali and ammonia water, wherein the pH value is 10 and the concentration of ammonia water is 4 g / L) at a feeding rate of 10 L / h, 3 L / h and 1 L / h, respectively. A coprecipitation reaction is carried out at a stirring rate of 250 r / min. During the reaction, the pH of the reaction system is controlled to be 10.3, the ammonia concentration is 4 g / L, and the temperature is 60°C. The particle size is continuously monitored. Before the particle size does not meet the requirements, a high-efficiency concentrator is used in the reaction process to collect all the particles and return them to the reactor for continuous reaction and growth. When the particle size D50 reaches 4 μm, the feeding is stopped and the reaction is continued until the material reaction is complete to obtain the positive electrode precursor matrix material Ni0.91 Co 0.03 Mn 0.06 (OH)2 reaction slurry.

[0078] S2: A 1.5 mol / L tetraethyl orthosilicate (TEOS) solution is added dropwise to the reaction slurry of S1, and a 20 nm SiO2 coating layer is formed on the surface of the positive electrode precursor matrix material through a hydrolysis-condensation reaction at a pH of 10 and a temperature of 80°C. The voids in the positive electrode precursor matrix material are also filled with silicon dioxide. After aging, washing and drying, the high nickel positive electrode precursor material is obtained.

[0079] Example 4

[0080] The difference between this embodiment and embodiment 1 is that in step S1 of this embodiment, the molar ratio of nickel, cobalt and manganese in the nickel-cobalt-manganese sulfate solution is 0.8:0.1:0.1.

[0081] The rest of the preparation methods and parameters were the same as those in Example 1.

[0082] Example 5

[0083] The difference between this embodiment and embodiment 1 is that in step S1 of this embodiment, the D50 of the positive electrode precursor matrix material is 8 μm.

[0084] The rest of the preparation methods and parameters were the same as those in Example 1.

[0085] Example 6

[0086] The difference between this embodiment and embodiment 1 is that in step S2 of this embodiment, the concentration of the tetraethyl orthosilicate (TEOS) solution is 2.0 mol / L.

[0087] The rest of the preparation methods and parameters were the same as those in Example 1.

[0088] Example 7

[0089] The difference between this embodiment and embodiment 1 is that in step S2 of this embodiment, the concentration of the tetraethyl orthosilicate (TEOS) solution is 0.01 mol / L.

[0090] The rest of the preparation methods and parameters were the same as those in Example 1.

[0091] Example 8

[0092] The difference between this embodiment and embodiment 1 is that in step S2 of this embodiment, the pH value of the hydrolysis reaction is 10.5.

[0093] The rest of the preparation methods and parameters were the same as those in Example 1.

[0094] Example 9

[0095] The difference between this embodiment and embodiment 1 is that in step S2 of this embodiment, the pH value of the hydrolysis reaction is 7.5.

[0096] The rest of the preparation methods and parameters were the same as those in Example 1.

[0097] Example 10

[0098] The difference between this embodiment and embodiment 1 is that in step S2 of this embodiment, the thickness of the silicon dioxide coating layer is 25 nm.

[0099] In the preparation method, the hydrolysis time and the amount of silicon source added are adaptively adjusted.

[0100] The rest of the preparation methods and parameters were the same as those in Example 1.

[0101] Comparative Example 1

[0102] The difference between this comparative example and Example 1 is that the silicon source hydrolysis process in step S2 is not performed in this comparative example, and the reaction slurry is directly aged, washed and dried.

[0103] The rest of the preparation methods and parameters were the same as those in Example 1.

[0104] Comparative Example 2

[0105] The difference between this comparative example and Example 1 is that in the preparation method of this comparative example, tetraethyl orthosilicate (TEOS) solution is directly added during the coprecipitation reaction, that is, the coprecipitation reaction and the hydrolysis reaction are carried out simultaneously.

[0106] The rest of the preparation methods and parameters were the same as those in Example 1.

[0107] [Battery preparation and performance testing]

[0108] (I) Preparation of positive electrode materials: The high-nickel positive electrode precursor materials provided in Examples 1-10 and Comparative Examples 1-2 and lithium carbonate powder were weighed and uniformly mixed at a molar ratio of Li / Me = 1.05:1, and then subjected to two-terminal solid-phase sintering in an oxygen atmosphere, i.e., a first sintering, a second sintering, and a third sintering.

[0109] The first sintering step was to increase the temperature from room temperature to 500°C at a heating rate of 4°C / min and keep the temperature for 6 hours. The second sintering step was to increase the temperature from 500°C to 900°C at a heating rate of 3°C / min and keep the temperature for 12 hours. After the sintering step, the sample was naturally cooled to room temperature in the furnace. The sample was crushed and passed through a 300-mesh sieve to obtain the positive electrode material.

[0110] (II) Preparation of the battery: providing a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte for battery preparation:

[0111] Preparation of the positive electrode plate: a positive electrode slurry is prepared according to the ratio of positive electrode material: SP: PVDF = 90:5:5, wherein the slurry solid content is 60%; an aluminum foil is placed on a coating machine, a 150μm film applicator is placed on the aluminum foil, the single crystal slurry is poured into the coating machine, and the equipment is turned on for coating. After coating, the electrode plate is obtained, and the electrode plate is placed in a 110°C oven for drying and roller pressing to obtain the positive electrode plate;

[0112] The positive electrode sheets provided in the embodiment and the comparative example were cut into discs with a diameter of 15 mm using a punch press in a dry environment. In a glove box, a metal lithium sheet was used as a counter electrode, a Ceglar composite membrane was selected as the isolation membrane, and an electrolyte was added to assemble a button battery; the electrolyte was an organic solution obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) in a mass ratio of 30:50:20, and the concentration of lithium salt (lithium hexafluorophosphate) in the electrolyte was 1.15 mol / L.

[0113] (III) Performance test:

[0114] The performance tests of the button batteries provided in Examples 1-9 and Comparative Examples 1-4 were performed using the Wuhan Blue Power CT2001A system:

[0115] The electrochemical performance test was carried out at 45°C in the voltage range of 2.7 to 4.3 V under 1C conditions, and the capacity retention rate after 100 cycles at 1C rate was obtained.

[0116] The test results of the above tests are shown in Table 1.

[0117] Table 1

[0118]

[0119]

[0120] In summary, in the preparation method provided by the present invention, a positive electrode precursor matrix material is first prepared, and then a silicon source is used for hydrolysis and coating to obtain a silicon dioxide coating layer. On the one hand, co-precipitation and coating are carried out step by step, and the parameters are independently controlled, which is more suitable for large-scale production; on the other hand, the step-by-step preparation can accurately control the SiO2 distribution, avoid the deterioration of the coating effect caused by incomplete hydrolysis of the silicon source, reduce the morphological damage to the precursor material, improve the uniformity, and achieve ultra-thin and uniform coating of the silicon dioxide coating layer, complete coverage and dense coating layer, thereby improving the cycle stability and high-temperature performance of the high-nickel positive electrode material obtained from the precursor material, effectively inhibiting the dissolution of transition metals, and reducing the occurrence of surface side reactions, especially improving the cycle performance and high-temperature performance of the high-nickel positive electrode material under high voltage.

[0121] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a high-nickel ternary positive electrode precursor material, characterized in that: The preparation method comprises the following steps: Adding a nickel-cobalt-manganese mixed salt solution, a precipitant solution, and a complexing agent solution in parallel to perform a coprecipitation reaction to obtain a reaction slurry of a positive electrode precursor matrix material; The reaction slurry and the silicon source solution are mixed and hydrolyzed and coated to obtain the high-nickel ternary positive electrode precursor material. The high-nickel ternary positive electrode precursor material includes a positive electrode precursor base material and a silicon dioxide coating layer coated on the surface of the positive electrode precursor base material.

2. The preparation method according to claim 1, characterized in that The median particle size D50 of the positive electrode precursor matrix material in the reaction slurry is 2.5 μm to 4 μm.

3. The preparation method according to claim 1, characterized in that The silicon source in the silicon source solution has a silicon-halogen bond and / or a silicon-alkoxy bond; Preferably, the silicon source comprises any one of silicon tetrachloride, methyl orthosilicate or ethyl orthosilicate, or a combination of at least two thereof; Preferably, the concentration of the silicon source solution is 0.05 mol / L to 1.5 mol / L.

4. The preparation method according to claim 1 or 2, characterized in that The pH value of the hydrolysis coating is 8 to 10; Preferably, the temperature of the hydrolysis coating is 40°C to 80°C.

5. The preparation method according to claim 1, characterized in that The thickness of the silicon dioxide coating layer is 1 nm to 20 nm; Preferably, the voids in the positive electrode precursor matrix material are filled with silicon dioxide.

6. The preparation method according to claim 1, characterized in that The concentration of the nickel-cobalt-manganese mixed salt solution is 80 g / L to 120 g / L; Preferably, in the nickel-cobalt-manganese mixed salt solution, nickel accounts for ≥80% of the total molar amount of nickel-cobalt-manganese, preferably ≥90%; Preferably, the mass concentration of the precipitant solution is 28% to 32%; Preferably, the mass concentration of the precipitant solution is 10% to 20%; Preferably, the feed rate of the nickel-cobalt-manganese mixed salt solution is 6 L / h to 10 L / h; Preferably, the feed rate of the precipitant solution is 2 L / h to 3 L / h; Preferably, the concentration of the complexing agent solution is 0.6 L / h to 1 L / h.

7. The preparation method according to claim 1, characterized in that The reaction temperature of the coprecipitation reaction is 40° C. to 60° C., the stirring speed of the coprecipitation reaction is 200 rpm to 400 rpm, and the pH value of the coprecipitation reaction is 10 to 12.

8. A high nickel ternary cathode precursor material, characterized in that: The high-nickel ternary positive electrode precursor material is prepared by the preparation method according to any one of claims 1 to 7.

9. A high nickel cathode material, characterized in that The high-nickel positive electrode material is obtained by mixing the high-nickel ternary positive electrode precursor material according to claim 8 and a raw material including at least a lithium source and then sintering the mixture.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the high-nickel positive electrode material according to claim 9.

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