Preparation method and application of aluminum-doped lithium battery positive electrode material precursor

Abstract

The invention discloses a preparation method and application of an aluminum-doped lithium battery positive electrode material precursor, which comprises the following steps: dissolving aluminum salt and one or more of nickel salt, cobalt salt and manganese salt in water to prepare a mixed metal solution, and then selecting another aluminum salt to prepare an aluminum-alkali solution by taking alkali liquor as a solvent; the feeding of the mixed metal solution and the aluminum-alkali solution is controlled according to a certain feeding speed, and the precursor is prepared by a coprecipitation method, so that the sphericity of the precursor can be effectively improved, the particle size distribution is more uniform and consistent, and the electrochemical performance of the positive electrode material can be improved; meanwhile, formation of small balls in the precursor preparation process is reduced through a method of adding an additive into a kettle bottom solution, regulation and control of the length-width ratio of primary particles and improvement of the sphericity degree are facilitated, and meanwhile the particle size distribution of the precursor is more uniform and consistent.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation and application of lithium ion battery positive electrode material precursors, and specifically relates to a preparation method and application of an aluminum-doped lithium battery positive electrode material precursor. Background Art

[0002] In recent years, stimulated by green and sustainable development policies and enhanced people's green environmental protection concepts, with the rapid growth in sales of new energy vehicles and the steady growth in market demand for power tools, the demand for new energy power batteries has maintained a rapid growth. Lithium-ion batteries with high energy density and long cycle life are urgently needed by the market. The positive electrode material formed by sintering the ternary precursor and lithium salt is an important component of lithium-ion batteries, and is currently mainly used in power batteries for new energy vehicles. Due to its advantages in specific capacity and energy density, the installed capacity of ternary materials has been continuously increasing in recent years, and it has broad application prospects. After high-temperature sintering, the performance of the ternary precursor is continued on the ternary positive electrode material. Therefore, the control process of the ternary precursor is crucial.

[0003] High-nickel ternary cathode materials have high discharge capacity, but the cycle performance and safety will be reduced. In order to seek a balance between high capacity and high stability, higher requirements are placed on ternary precursors. Currently, the more high-nickel products on the market are nickel-cobalt-manganese and nickel-cobalt-aluminum. The production of ternary cathode material precursors mainly adopts the hydroxide co-precipitation process, but the nature of aluminum hydroxide determines that it may not be able to precipitate evenly with nickel hydroxide and cobalt hydroxide at the same time. It is very likely that aluminum hydroxide will nucleate alone during the precipitation process, causing the precursor particle size distribution to be uneven and inconsistent, and the spherical morphology is relatively poor, which is not conducive to the sintering of ternary cathode materials, and thus affects the performance of ternary cathode materials.

[0004] The patent document of CN103178262A discloses a method for preparing aluminum-doped lithium nickel cobalt oxide, wherein a soluble salt solution of nickel and cobalt, ammonia water and an alkaline solution are added to a reactor at the same time for a coprecipitation reaction, and a nickel cobalt hydroxide precursor is synthesized by controlling the process parameters in the preparation process; the nickel cobalt hydroxide precursor obtained by the above reaction is washed to a certain condition, a soluble aluminum salt solution is added thereto, and the process parameters in the reaction process are controlled to synthesize a nickel cobalt aluminum hydroxide precursor. The patented technology discloses a method for preparing a nickel cobalt aluminum hydroxide precursor by a step-by-step precipitation method, and the prepared nickel cobalt aluminum hydroxide precursor has a spherical or quasi-spherical morphology, but the step-by-step precipitation process cannot achieve a uniform distribution of nickel cobalt aluminum elements and the prepared nickel cobalt aluminum hydroxide precursor has an uneven and consistent particle size distribution, and a relatively poor spherical morphology, which is not conducive to the sintering of the positive electrode material, and thus affects the performance of the positive electrode material.

[0005] The patent document of CN106935844A discloses a method for preparing a positive electrode material for a lithium ion battery, wherein a salt solution, an alkaline solution containing aluminum and a complexing agent solution are added to a reactor with an overflow port in parallel for reaction, and the precursor slurry obtained by overflow is subjected to solid-liquid separation, washing, drying and screening to obtain a positive electrode material precursor, which is then mixed with a lithium source, sintered, crushed and screened to obtain a positive electrode material uniformly doped with aluminum. This method can achieve uniform doping of aluminum elements in the precursor, and has a simple process, a smooth flow, low production cost, and is suitable for large-scale industrial production. However, since the patented technology adopts a single aluminum source feeding method and the bottom liquid of the kettle does not contain additives, the particle size distribution of the prepared positive electrode material precursor is uneven and consistent, forming a small particle product, which is not conducive to the sintering of the positive electrode material, and thus affects the performance of the positive electrode material.

[0006] The patent document of CN109896552A discloses a method for preparing an aluminum-doped lithium ion positive electrode material precursor, wherein a cobalt solution, ammonia water and an aluminum complex solution mixed solution are added to the reactor from one side of the reactor in parallel, and a liquid alkali solution is added to the reactor from the other side of the reactor in a metered manner; the solution added to the reactor is stirred and mixed by a spiral stirring impeller and the pH value of the solution is controlled to be about 12.4; the uniformly mixed solution in the reactor is allowed to stand, the supernatant is filtered into an aging tank, and the aged reactants are sintered and mixed batch demagnetized to obtain a finished aluminum-doped cobalt oxide precursor. This patented technology ensures the strength of the prepared aluminum-doped lithium ion positive electrode material precursor, while the aluminum element distribution in the prepared aluminum-doped cobalt oxide precursor is more uniform. However, due to the use of a single aluminum source feeding method and the absence of additives in the bottom liquid of the reactor, the particle size distribution of the prepared positive electrode material precursor is uneven and uniform, forming a small particle product, which is not conducive to the sintering of the positive electrode material, and further affects the performance of the positive electrode material.

[0007] Based on the problems existing in the current preparation process of aluminum-doped positive electrode material precursors, the present invention focuses on providing a new aluminum doping method for preparing aluminum-doped positive electrode material precursors, selecting two aluminum sources and feeding them separately in different ways, effectively solving the problems of uneven distribution of metal elements and uneven particle size distribution of positive electrode material precursors during the co-precipitation process, thereby effectively improving the electrochemical properties and recycling performance of the positive electrode materials prepared by subsequent sintering. There are currently no related reports in this regard. Summary of the invention

[0008] The present invention aims to solve the existing problems of uneven co-precipitation of aluminum elements in aluminum-doped lithium battery positive electrode material precursors, relatively poor precursor sphericity, and uneven precursor particle size distribution. The present invention provides a method for preparing an aluminum-doped lithium battery positive electrode material precursor. The aluminum-doped lithium battery positive electrode material precursor prepared by the method has uniform metal element distribution, good precursor sphericity, and more uniform precursor particle size distribution, which is beneficial to improving the electrochemical properties of the positive electrode material to a certain extent. At the same time, the present invention reduces the formation of small balls in the precursor preparation process by adding additives to the kettle bottom liquid, which is beneficial to regulating the aspect ratio of the primary particles and improving the sphericity, and at the same time makes the precursor particle size distribution more uniform.

[0009] The present invention adopts the following technical solution to solve the above technical problems, a method for preparing an aluminum-doped lithium positive electrode material precursor, and the specific steps are: Step S1: dissolving a first aluminum salt and a metal salt in pure water to prepare a mixed metal solution, wherein the first aluminum salt is one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum sol or sodium aluminate, and the metal salt is one or more of a soluble nickel salt, a soluble cobalt salt or a soluble manganese salt; Step S2: dissolving a second aluminum salt in an alkaline solution to prepare an aluminum-alkaline solution, wherein the second aluminum salt is one or more of aluminum acetate, aluminum sulfate, aluminum chloride, aluminum nitrate or sodium aluminate; Step S3: adding pure water, alkaline solution, complexing agent and additives into the reaction kettle to prepare a mixed solution as the bottom liquid, wherein the complexing agent is one or more of ammonia water, urea, citric acid or sodium citrate, and the additive is one or more of sodium sulfate, potassium sulfate or cesium sulfate; Step S4: The mixed metal solution obtained in step S1, the aluminum-alkali solution obtained in step S2, the alkali solution and the complexing agent are simultaneously introduced into the reactor, the pH value of the reaction system is controlled to be 10.0-14.0, the rotation speed is 200-1000 rpm, and the precursor slurry is obtained by coprecipitation reaction at 30-90° C. The precursor slurry is washed, dehydrated, dried and sieved to obtain an aluminum-doped lithium battery positive electrode material precursor, the precursor particles have good sphericity and uniform particle size distribution, the aluminum element is uniformly distributed in the precursor, and the tap density of the precursor is greater than 1.5 g / cm 3 , with a specific surface area of ​​5~60m 2 / g, particle size D50 is 2~20μm.

[0010] It is further defined that the soluble nickel salt in step S1 is one or more of nickel sulfate, nickel nitrate, nickel acetate or nickel chloride; the soluble cobalt salt is one or more of cobalt sulfate, cobalt nitrate, cobalt acetate or cobalt chloride; the soluble manganese salt is one or more of manganese sulfate, manganese nitrate, manganese acetate or manganese chloride.

[0011] It is further defined that the alkaline solutions in step S2 and step S3 are one or more of sodium hydroxide solution or potassium hydroxide solution.

[0012] It is further defined that the concentration of the additive in the kettle bottom liquid in step S3 is 0.5-4 mol / L, and the pH value of the kettle bottom liquid is controlled to be 10.0-14.0 by adding a complexing agent and an alkaline solution.

[0013] It is further defined that the total concentration of the mixed metal solution in step S4 is 1.0~3.0 mol / L, and the flow rate of the mixed metal solution is 5~150 mL / min; the concentration of the aluminum-alkali solution is 0.01~5 mol / L, and the flow rate of the aluminum-alkali solution is 5~200 mL / min; the concentration of the alkali solution is 2~8 mol / L, and the flow rate of the alkali solution is 3~150 mL / min; the flow rate of the complexing agent is 0.02~100 mL / min.

[0014] Application of the precursor of the present invention in the preparation of positive electrode materials for lithium-ion batteries.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: the present invention can effectively improve the deposition rate of aluminum element in the coprecipitation process, achieve uniform distribution of aluminum element, obtain precursor particles with better sphericity and more uniform particle size distribution, and at the same time, the specific surface area of ​​the precursor reaches 5-60m 2 / g, tap density greater than 1.5g / cm 3, which is beneficial to improving the electrochemical performance and high-capacity long-cycle performance of the positive electrode material. The solubility product constant of aluminum is greatly different from that of nickel, cobalt, and manganese elements, and it is easy to precipitate preferentially to form small particles. The present invention simultaneously selects two aluminum source materials and feeds them simultaneously through two feeding methods, replacing the current feeding method of a single aluminum source. A variety of aluminum ion forms are introduced into the solution, and additives are added to the bottom liquid. On the one hand, the ion saturation in the reaction system is increased, and the ion exchange efficiency is reduced. In the ion exchange process, there is a complementary ion effect, which affects the exchange effect. On the other hand, the solution ion concentration is changed, which affects the diffusion rate, thereby affecting the ion precipitation rate, effectively avoiding the generation of small particles. And it effectively ensures that the precursor particles have good sphericity and uniform particle size distribution. The higher specific surface area of ​​the aluminum-doped lithium positive electrode material precursor prepared by the present invention is beneficial to improving the sintering efficiency of the positive electrode material, accelerating the diffusion of lithium ions during the sintering process, and the larger tap density is beneficial to the production of positive electrode sheets, reducing the production cost of secondary batteries. Therefore, the precursor prepared by the present invention not only has excellent spherical morphology and uniform particle size distribution, but also can reduce production costs and improve the electrochemical performance of positive electrode materials. In addition, the generation of small balls during the precursor preparation process is not conducive to particle size control and will reduce production efficiency. The present invention adds additives to the bottom liquid to effectively inhibit the formation of small particle products, which is conducive to regulating the aspect ratio of primary particles and improving sphericity, while making the particle size distribution of the precursor particles more uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the SEM image of the precursor prepared in Example 1.

[0017] Figure 2 This is the SEM image of the precursor prepared in Example 2.

[0018] Figure 3 This is the SEM image of the precursor prepared in Comparative Example 1.

[0019] Figure 4 This is the SEM image of the precursor prepared in Comparative Example 2.

[0020] Figure 5 This is the SEM image of the precursor prepared in Comparative Example 3.

[0021] Figure 6 This is the SEM image of the precursor prepared in Comparative Example 4. DETAILED DESCRIPTION

[0022] The above contents of the present invention are further described in detail below through examples, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies implemented based on the above contents of the present invention belong to the scope of the present invention. Example 1

[0023] The NCA precursor was prepared as follows: (1) nickel sulfate, cobalt sulfate and aluminum sulfate are prepared into a mixed metal solution with a total concentration of 1.8 mol / L using pure water, wherein the molar ratio of nickel, cobalt and aluminum is 88:8:4; sodium aluminate is prepared into an aluminum-alkali solution with a concentration of 1.5 mol / L using a NaOH solution; (2) pure water, ammonia water, sodium hydroxide solution and sodium sulfate were added into the reaction kettle to obtain a mixed solution as the bottom liquid, wherein the pH of the bottom liquid was 13.2, the ammonia concentration was 20 g / L, and the sodium sulfide concentration was 1.2 mol / L; (3) The stirring rate of the reactor was set to 300 rpm and the temperature in the reactor was controlled at 40 ± 0.5 °C. The metal mixed solution and the aluminum-alkali solution were continuously introduced into the reactor at a flow rate of 4:1. At the same time, sodium hydroxide solution and ammonia water were introduced to control the pH of the reaction system to 31.2 until the particle size reached 3.0-4.0 μm. Then, the feed into the reactor was stopped to obtain a precursor slurry. (4) Wash the precursor slurry and dry it at 130 °C for 15 h to obtain Ni 88 Co5Al7(OH)2 precursor, the precursor has good particle sphericity and uniform distribution of aluminum elements, the precursor particle size distribution is uniform, and the tap density of the precursor is 1.87g / cm 3 , the specific surface area is 23.43m 2 / g, and the particle size D50 is 3.5μm. Example 2

[0024] The NMA precursor was prepared as follows: (1) nickel sulfate, manganese sulfate and aluminum sulfate are prepared into a mixed metal solution with a total concentration of 2 mol / L using pure water, wherein the molar ratio of nickel, manganese and aluminum is 91:4:5; sodium aluminate is prepared into an aluminum-alkali solution with a concentration of 0.1 mol / L using a NaOH solution; (2) Adding pure water, ammonia water, sodium hydroxide solution and potassium sulfate into the reaction kettle to obtain a mixed solution as the bottom liquid, wherein the pH of the bottom liquid is 11.6-11.7, the ammonia concentration is 3-4 g / L, and the potassium sulfate concentration is 1 mol / L; (3) The stirring rate of the reactor was set to 800 rpm and the temperature in the reactor was controlled at 40 ± 0.5 °C. The metal mixed solution and the aluminum-alkali solution were continuously introduced into the reactor at a flow rate of 1:1. At the same time, sodium hydroxide solution and ammonia water were introduced to control the pH of the reaction system to 11.6-11.7 until the particle size reached 13.0-14.0 μm. Then, the feed into the reactor was stopped to obtain a precursor slurry. (4) Wash the precursor slurry and dry it at 100 °C for 15 h to obtain Ni 93Mn2Al5(OH)2 precursor, the precursor has good particle sphericity and uniform distribution of aluminum elements, the precursor particle size distribution is uniform, and the tap density of the precursor is 2.12g / cm 3 , the specific surface area is 13.47m 2 / g, and the particle size D50 is 12.4μm.

[0025] Comparative Example 1 This comparative example is a control experiment of Example 2, and is implemented according to the same conditions and steps as Example 2, except that only aluminum sulfate is used as the only aluminum source. The specific method is as follows: The NMA precursor was prepared as follows: (1) nickel sulfate, manganese sulfate and aluminum sulfate are prepared into a mixed metal solution with a total concentration of 2 mol / L using pure water, wherein the molar ratio of nickel, manganese and aluminum is 91:4:5; (2) Adding pure water, ammonia water, sodium hydroxide solution and potassium sulfate into the reaction kettle to obtain a mixed solution as the bottom liquid, wherein the pH of the bottom liquid is 11.6-11.7, the ammonia concentration is 3-4 g / L, and the potassium sulfate concentration is 1 mol / L; (3) The stirring rate of the reactor was set to 800 rpm and the temperature in the reactor was controlled at 40 ± 0.5 °C. The metal mixed solution and the aluminum-alkali solution were continuously introduced into the reactor at a flow rate of 1:1. At the same time, sodium hydroxide solution and ammonia water were introduced to control the pH of the reaction system to 11.6-11.7 until the particle size reached 13.0-14.0 μm. Then, the feed into the reactor was stopped to obtain a precursor slurry. (4) Wash the precursor slurry and dry it at 100 °C for 15 h to obtain Ni 93 Mn2Al5(OH)2 precursor, the sphericity of the precursor is relatively good, the element distribution is uneven, the particle size distribution of the precursor is uneven and uniform, forming a small particle product, and the tap density of the precursor is 1.57g / cm 3 , with a specific surface area of ​​10.24m 2 / g, and the particle size D50 is 12.2μm.

[0026] Comparative Example 2 This comparative example is a control experiment of Example 2, and is implemented according to the same conditions and steps as Example 2, except that only aluminum-alkali solution is used as the only aluminum source. The specific method is as follows: The NMA precursor was prepared as follows: (1) preparing nickel sulfate and manganese sulfate into a mixed metal solution with a total concentration of 2 mol / L using pure water, wherein the molar ratio of nickel to manganese is 95.8:4.2; preparing sodium aluminate into an aluminum-alkali solution with a concentration of 0.1 mol / L using a NaOH solution; (2) Adding pure water, ammonia water, sodium hydroxide solution and potassium sulfate into the reaction kettle to obtain a mixed solution as the bottom liquid, wherein the pH of the bottom liquid is 11.6-11.7, the ammonia concentration is 3-4 g / L, and the potassium sulfate concentration is 1 mol / L; (3) The stirring rate of the reactor was set to 800 rpm and the temperature in the reactor was controlled at 40 ± 0.5 °C. The metal mixed solution and the aluminum-alkali solution were continuously introduced into the reactor at a flow rate of 1:1. At the same time, sodium hydroxide solution and ammonia water were introduced to control the pH of the reaction system to 11.6-11.7 until the particle size reached 13.0-14.0 μm. Then, the feed into the reactor was stopped to obtain a precursor slurry. (4) Wash the precursor slurry and dry it at 100 °C for 15 h to obtain Ni 93 Mn2Al5(OH)2 precursor, the precursor particles have uneven sphericity, the aluminum element is evenly distributed, the precursor particle size distribution is uneven and uniform, forming a small particle product, the precursor tap density is 1.64g / cm 3 , the specific surface area is 12.33m 2 / g, and the particle size D50 is 7.4μm.

[0027] Comparative Example 3 This comparative example is a control experiment of Example 2, and is implemented according to the same conditions and steps as Example 2, except that the additive potassium sulfate is not added to the bottom liquid of the kettle. The specific method is as follows: (1) nickel sulfate, manganese sulfate and aluminum sulfate are prepared into a mixed metal solution with a total concentration of 2 mol / L using pure water, wherein the molar ratio of nickel, manganese and aluminum is 91:4:5; sodium aluminate is prepared into an aluminum-alkali solution with a concentration of 0.1 mol / L using a NaOH solution; (2) Adding pure water, ammonia water and sodium hydroxide solution into the reactor to obtain a mixed liquid as the bottom liquid, the pH of the bottom liquid is 11.6-11.7, and the ammonia concentration is 3-4 g / L; (3) The stirring rate of the reactor was set to 800 rpm and the temperature in the reactor was controlled at 40 ± 0.5 °C. The metal mixed solution and the aluminum-alkali solution were continuously introduced into the reactor at a flow rate of 1:1. At the same time, sodium hydroxide solution and ammonia water were introduced to control the pH of the reaction system to 11.6-11.7 until the particle size reached 13.0-14.0 μm. Then, the feed into the reactor was stopped to obtain a precursor slurry. (4) Wash the precursor slurry and dry it at 100 °C for 15 h to obtain Ni 93 Mn2Al5(OH)2 precursor, the precursor has good particle sphericity and uniform distribution of aluminum elements. The particle size distribution of the precursor is uneven and uniform, forming a small particle product. The tap density of the precursor is 1.72g / cm 3, the specific surface area is 12.93m 2 / g, and the particle size D50 is 13.8μm.

[0028] Comparative Example 4 This comparative example is a control experiment of Example 2, and is carried out under the same conditions and steps as Example 2, except that only aluminum sulfate is used as the only aluminum source and no additive potassium sulfate is added to the bottom liquid of the kettle. The specific method is as follows: The NMA precursor was prepared as follows: (1) nickel sulfate, manganese sulfate and aluminum sulfate are prepared into a mixed metal solution with a total concentration of 2 mol / L using pure water, wherein the molar ratio of nickel, manganese and aluminum is 91:4:5; (2) Adding pure water, ammonia water and sodium hydroxide solution into the reactor to obtain a mixed liquid as the bottom liquid, the pH of the bottom liquid is 11.6-11.7, and the ammonia concentration is 3-4 g / L; (3) The stirring rate of the reactor was set to 800 rpm and the temperature in the reactor was controlled at 40 ± 0.5 °C. The metal mixed solution and the aluminum-alkali solution were continuously introduced into the reactor at a flow rate of 1:1. At the same time, sodium hydroxide solution and ammonia water were introduced to control the pH of the reaction system to 11.6-11.7 until the particle size reached 13.0-14.0 μm. Then, the feed into the reactor was stopped to obtain a precursor slurry. (4) Wash the precursor slurry and dry it at 100 °C for 15 h to obtain Ni 93 Mn2Al5(OH)2 precursor, the particle sphericity of the precursor is relatively good, the aluminum element is unevenly distributed, the particle size distribution of the precursor is uneven, and small particle products are formed. The tap density of the precursor is 1.51g / cm 3 , with a specific surface area of ​​9.85m 2 / g, and the particle size D50 is 13.2μm.

[0029] The above embodiments describe the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the scope of the principles of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing an aluminum-doped lithium positive electrode material precursor, characterized in that The specific steps are: Step S1: dissolving a first aluminum salt and a metal salt in pure water to prepare a mixed metal solution, wherein the first aluminum salt is one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum sol or sodium aluminate, and the metal salt is one or more of a soluble nickel salt, a soluble cobalt salt or a soluble manganese salt; Step S2: dissolving a second aluminum salt in an alkaline solution to prepare an aluminum-alkaline solution, wherein the second aluminum salt is one or more of aluminum acetate, aluminum sulfate, aluminum chloride, aluminum nitrate or sodium aluminate; Step S3: adding pure water, alkaline solution, complexing agent and additives into the reaction kettle to prepare a mixed solution as the bottom liquid, wherein the complexing agent is one or more of ammonia water, urea, citric acid or sodium citrate, and the additive is one or more of sodium sulfate, potassium sulfate or cesium sulfate; Step S4: The mixed metal solution obtained in step S1, the aluminum-alkali solution obtained in step S2, the alkali solution and the complexing agent are simultaneously introduced into the reactor, the pH value of the reaction system is controlled to be 10.0-14.0, the rotation speed is 200-1000 rpm, and the precursor slurry is obtained by coprecipitation reaction at 30-90° C. The precursor slurry is washed, dehydrated, dried and sieved to obtain an aluminum-doped lithium battery positive electrode material precursor, the precursor particles have good sphericity and uniform particle size distribution, the aluminum element is uniformly distributed in the precursor, and the tap density of the precursor is greater than 1.5 g / cm 3 , with a specific surface area of ​​5~60m 2 / g, particle size D50 is 2~20μm.

2. The method for preparing an aluminum-doped lithium positive electrode material precursor according to claim 1, characterized in that: In step S1, the soluble nickel salt is one or more of nickel sulfate, nickel nitrate, nickel acetate or nickel chloride; the soluble cobalt salt is one or more of cobalt sulfate, cobalt nitrate, cobalt acetate or cobalt chloride; the soluble manganese salt is one or more of manganese sulfate, manganese nitrate, manganese acetate or manganese chloride.

3. The method for preparing an aluminum-doped lithium positive electrode material precursor according to claim 1, characterized in that: The alkaline solutions in step S2 and step S3 are one or more of sodium hydroxide solution and potassium hydroxide solution.

4. The method for preparing an aluminum-doped lithium positive electrode material precursor according to claim 1, characterized in that: The concentration of the additive in the kettle bottom liquid in step S3 is 0.5-4 mol / L, and the pH value of the kettle bottom liquid is controlled to be 10.0-14.0 by adding a complexing agent and an alkaline solution.

5. The method for preparing an aluminum-doped lithium positive electrode material precursor according to claim 1, characterized in that: The total concentration of the mixed metal solution in step S4 is 1.0-3.0 mol / L, and the flow rate of the mixed metal solution is 5-150 mL / min; the concentration of the aluminum-alkali solution is 0.01-5 mol / L, and the flow rate of the aluminum-alkali solution is 5-200 mL / min; the concentration of the alkali solution is 2-8 mol / L, and the flow rate of the alkali solution is 3-150 mL / min; the flow rate of the complexing agent is 0.02-100 mL / min.

6. Use of a precursor prepared by the method according to any one of claims 1 to 5 in preparing positive electrode materials for lithium-ion batteries.

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