A preparation method of a multi-shell loose porous core-shell structure nickel-based positive electrode material precursor

Abstract

This invention discloses a method for preparing a multi-shell porous core-shell structured nickel-based cathode material precursor. This method directly controls the preparation of the precursor through partial reaction control. A seed reactor and a reaction vessel are connected to a concentration tank to control the precursor particle size. During the precursor preparation stage, the pH of the reaction system is controlled by continuously reducing the flow rate of the complexing agent solution, thereby achieving continuous coating of the seed core surface with multiple loose shells. The cathode material prepared based on the multi-shell porous core-shell structured nickel-based cathode material precursor can store more electrolyte, thus improving the cycle performance during charge and discharge. Furthermore, the loose porous structure of the cathode material prepared based on the multi-shell porous core-shell structured nickel-based cathode material precursor can provide more storage space under overcharge conditions of lithium-ion batteries, thereby improving their safety performance.

Description

Technical Field

[0001] This invention belongs to the field of new process technology for preparing nickel-based cathode material precursors for lithium-ion batteries, specifically relating to a method for preparing a multi-shell loose porous core-shell structure nickel-based cathode material precursor. Background Technology

[0002] In recent years, with the rapid growth in sales of new energy vehicles and the stable growth in market demand for power tools, the demand for new energy power batteries has maintained rapid growth. High energy density and long cycle life lithium-ion batteries are urgently needed by the market. The cathode material formed by sintering ternary precursors and lithium salts is an important component of lithium-ion batteries, 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, showing broad application prospects. After high-temperature sintering, the performance of the ternary precursor is continued in the ternary cathode material; therefore, the control process of the ternary precursor is crucial.

[0003] Porous cathode materials are currently receiving increasing attention and research. Porous cathode materials offer several advantages: firstly, their porous structure allows for the storage of more electrolyte, effectively improving cycle performance during charge and discharge; secondly, their porous structure provides more storage space under overcharge conditions in lithium-ion batteries, thus enhancing their safety performance. However, current technologies lack control over the pore structure during the preparation of porous precursors.

[0004] After reviewing numerous literature reports on the preparation methods of porous cathode materials, most of these techniques involve adding porous carbon and carbon nanotube dispersions during the preparation of the cathode material precursor. Later, during the sintering process of the cathode material, the porous carbon and carbon nanotubes decompose and are removed under high-temperature conditions, leaving a porous structure inside the cathode material, thus obtaining the porous cathode material. For example, patent document CN116924487A discloses a porous precursor material, its preparation method, and its application. In the precursor material preparation process, by introducing a pore-forming agent and using a two-step method, the pores can be uniformly distributed inside the precursor material, increasing the diffusion channels for lithium ions and allowing the cathode material to fully utilize its capacity. However, this technical solution requires the addition of an additional pore-forming agent, making the process cumbersome and relatively expensive.

[0005] Patent document CN103178262A discloses a ternary precursor, its preparation method, and a cathode material. The ternary precursor is a nickel-cobalt-manganese hydroxide. The ternary precursor includes a core layer, a shell layer, and multiple connecting layers between the core and shell layers. Its specific preparation process results in a dense core and shell layer, while the connecting layers are relatively loose. The provided cross-sectional electron microscopy images show that the precursor prepared in this patent document has a dense internal structure, which is not conducive to the formation of multiple lithium-ion diffusion channels during sintering with lithium salts, and also hinders the entry of coating and modifying elements onto the primary particle surface. This technical solution fails to highlight the advantages of the improved precursor.

[0006] Patent document CN115367815B discloses a multilayer annular porous nickel-cobalt-aluminum precursor, its preparation method, and its cathode material. The precursor D... 50 The particle size ranges from 8 to 20 μm. Cross-sectional electron microscopy (TEM) images reveal multiple layers of annular pores in the secondary spherical particle structure, with the average porosity of a single or multiple particles ranging from 6% to 14%. The preparation process involves co-precipitation of a nickel-cobalt mixed salt solution, an alkaline aluminum solution, a complexing agent, and a precipitant. The pH value and aluminum concentration are strictly controlled at each stage. Solid-liquid separation, washing, drying, mixing, sieving, and demagnetization are then performed to obtain a nickel-cobalt-aluminum precursor with multiple layers of annular pores. This patented technology aims to improve lithium-ion diffusion channels and rates. However, the provided TEM images show that the prepared precursor has a relatively dense shell structure, which is not conducive to the formation of multiple lithium-ion diffusion channels through mixing and sintering with lithium salts, and also hinders the entry of coating and modifying elements onto the primary particle surface. This technology fails to highlight the advantages of the improved precursor. Summary of the Invention

[0007] The technical problem solved by this invention is to provide a method for preparing a multi-shell porous core-shell structured nickel-based cathode material precursor. This method does not require the addition of additional pore-forming agents or specific organic raw materials and additives. It can directly control the preparation of the multi-shell porous core-shell structured nickel-based cathode material precursor through partial reaction control of the precursor. Based on the multi-shell structure of this nickel-based cathode material precursor, the final cathode material has multiple lithium-ion diffusion channels, which can buffer the lattice mechanical strain force of the cathode material during charge and discharge, thereby effectively improving cycle stability. The multi-shell structure of the cathode material prepared based on the multi-shell porous core-shell structured nickel-based cathode material precursor can store more electrolyte, thereby improving the cycle performance during charge and discharge. The loose porous structure of the cathode material prepared based on the multi-shell porous core-shell structured nickel-based cathode material precursor can provide more storage space under the overcharge condition of lithium-ion battery, thereby improving its safety performance.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for preparing a multi-shell porous core-shell structure nickel-based cathode material precursor, the specific preparation steps of which are as follows:

[0009] Step S1: Prepare a soluble mixed metal salt solution with a total concentration of 0.6~2.8 mol / L, wherein the soluble mixed metal salt is a mixed salt containing one or more of soluble nickel salt, soluble manganese salt, soluble cobalt salt or soluble aluminum salt, and then prepare an alkaline solution with a concentration of 2~10 mol / L and a complexing agent solution with a concentration of 3~11 mol / L respectively;

[0010] Step S2: Add deionized water to the seed crystal reactor, making up 40% to 80% of the reactor's volume. Heat the reactor to 35 to 70°C and start stirring. Introduce a protective gas into the reactor. Then, continuously feed a soluble mixed metal salt solution, an alkaline solution, and a complexing agent solution into the reactor for reaction. Control the flow rate of the soluble mixed metal salt solution to 60 to 600 L / h, the flow rate of the alkaline solution to 24 to 550 L / h, and the flow rate of the complexing agent solution to 1 to 300 L / h. The pH of the reaction system should be 10.0 to 12.5. When the total liquid in the reactor reaches 90% of its volume, transfer the material to a concentration tank for concentration. Return the concentrated material to the reactor to continue the reaction. Circulate the material in the reactor for 20 to 60 hours to obtain the final seed slurry.

[0011] Step S3: Add the seed slurry and sodium sulfate solution from the seed tank described in Step S2 to the reaction vessel to form a mixed system. The pH of this mixed system is 10.0~12.5, and the volume of the mixed system accounts for 40%~80% of the reaction vessel volume. Heat the reaction vessel to 40~65℃ and start stirring. Then, continuously feed the soluble mixed metal salt solution, alkaline solution, and complexing agent solution into the reaction vessel for reaction. Control the flow rate of the soluble mixed metal salt solution to 60~600 L / h and the flow rate of the alkaline solution to 24 L / h. The flow rate of the complexing agent solution is 1-300 L / h, and the pH of the reaction system is controlled by continuously reducing the flow rate of the complexing agent solution during the reaction process. This achieves continuous coating of multiple loose shells on the surface of the seed core. When the total liquid in the reactor reaches 90% of the reactor volume, the material in the reactor is transferred to another concentration tank for concentration. The concentrated material is then returned to the reactor to continue the reaction. The continuous reaction time in the internal circulation is 10-60 h, and finally the precursor slurry is obtained.

[0012] Step S4: The precursor slurry obtained in step S3 is washed with an alkaline solution and deionized water, and then centrifuged to obtain a filter cake. The filter cake contains SO4. 2- The content is 1500~3500ppm, Na +The content is ≤400ppm, and then the filter cake is dried to obtain a multi-shell porous core-shell structure nickel-based cathode material precursor.

[0013] Further specifying, the soluble nickel salt in step S1 is one or more of nickel sulfate, nickel chloride, nickel nitrate, or nickel carbonate; the soluble manganese salt is one or more of manganese sulfate or manganese chloride; the soluble cobalt salt is one or more of cobalt sulfate, cobalt chloride, cobalt acetate, or cobalt nitrate; and the soluble aluminum salt is one or more of aluminum chloride, aluminum sulfate, or sodium aluminate.

[0014] Further specifying, the alkaline solution in step S1 is one or more of sodium hydroxide solution or potassium hydroxide solution.

[0015] Further specifying, the complexing agent solution in step S1 is an ammonia solution or a citric acid solution.

[0016] Further specified, the pore size of the filter element in the concentration tank in step S2 is 0.1~0.3μm, and the final seed crystal particle size is 1.5~3.8μm; the pore size of the filter element in the concentration tank in step S3 is 0.1~0.5μm, and the final nickel-based cathode material precursor particle size is 5~16μm, and the filter element in the concentration tank is made of polypropylene or polyethylene.

[0017] Further specified, the stirring rate of the seed tank in step S2 is 200~650 r / min, and the stirring rate of the reaction vessel in step S3 is 100~600 r / min.

[0018] Further specifying, the protective gas in step S2 is nitrogen with a purity ≥ 99.99%, and the flow rate of the protective gas is 2~10m³. 3 / h, the time for introducing protective gas is 30~60min.

[0019] Further specifying, the nickel-based cathode material precursor mentioned in step S4 is a spherical nickel-cobalt hydroxide, a spherical nickel-manganese hydroxide, a spherical nickel-cobalt-manganese hydroxide, a spherical nickel-cobalt-aluminum hydroxide, or a spherical nickel-cobalt-manganese-aluminum hydroxide, with the corresponding chemical formula Ni. x Co 1-x (OH)2, Ni x Mn 1-x (OH)2, Ni x Co y Mn 1-x-y (OH)2, Ni x Co y Al 1-x-y (OH)2 or Ni x Co y Mn Z Al 1-x-y-Z (OH)2+(1-x-y-z) , of which 0.10 <x<0.98、0.01<y<0.7、0.01<z<0.50。

[0020] Further specifying, a method for preparing a multi-shell porous core-shell structured nickel-based cathode material precursor, the specific preparation steps are as follows:

[0021] Step S1: Prepare a soluble mixed metal salt solution with a total concentration of 2.1 mol / L, i.e., solution A, wherein the soluble mixed metal salt is a mixed salt of nickel sulfate and manganese sulfate with a molar ratio of Ni:Mn=0.35:0.65; prepare a sodium hydroxide solution with a concentration of 5.5 mol / L, i.e. solution B; and prepare an ammonia solution with a concentration of 7 mol / L, i.e. solution C.

[0022] Step S2: Add deionized water to the seed crystal reactor, making up 40% of the reactor's volume. Heat the reactor to 40°C and start stirring at 600 rpm. Introduce nitrogen gas as a protective gas into the reactor at a flow rate of 4 m³ / min. 3 The nitrogen gas was introduced at a rate of 600 L / h for 40 min. Then, solutions A, B, and C were continuously fed into the seed crystal reactor for reaction. The flow rates of solution A, B, and C were controlled at 435 L / h and 15 L / h, respectively. The pH of the reaction system was 11. When the total liquid in the seed crystal reactor reached 90% of its volume, the material in the seed crystal reactor was transferred to a concentration tank for concentration. The filter element in the concentration tank had a pore size of 0.2 μm. The clear liquid in the concentration tank was discharged directly from the outlet. The concentrated material was returned to the seed crystal reactor to continue the reaction. The continuous reaction time in the seed crystal reactor was 55 h, and finally, a seed slurry was obtained with an average seed particle size of 2.7 μm.

[0023] Step S3: Add the seed slurry and sodium sulfate solution from the seed tank described in Step S2 to the reaction vessel to form a mixed system. The pH of this mixed system is 11, and its volume accounts for 45% of the reaction vessel volume. Heat the reaction vessel to 50°C and start stirring at a speed of 350 r / min. Then, continuously feed solutions A, B, and C into the reaction vessel for reaction, controlling the flow rate of solution A at 600 L / h, solution B at 435 L / h, and solution C at 15 L / h. During the reaction, continuously reduce the flow rate... The flow rate of solution C was controlled from 15 L / h to 10 L / h to gradually decrease the pH of the reaction system from 11 to 10.5 over a period of 15 h, achieving continuous coating of multiple loose shells on the surface of the seed crystal core. When the total liquid in the reactor reached 90% of the reactor volume, the material in the reactor was transferred to another concentration tank for concentration. The filter element in the concentration tank had a pore size of 0.3 μm, and the clear liquid in the concentration tank was directly discharged from the outlet. The concentrated material was returned to the reactor to continue the reaction. The reaction was continuously circulated within the reactor for 20 h, and finally the precursor slurry was obtained.

[0024] Step S4: The precursor slurry obtained in step S3 is washed with an alkaline solution and deionized water, and then centrifuged to obtain a filter cake. The filter cake contains SO4. 2- The content is 2000~3500ppm, Na + The content was 300 ppm. After drying the filter cake at 100℃, a multi-shell porous core-shell structure nickel-based cathode material precursor was obtained. The chemical formula of the nickel-based cathode material precursor is Ni. 0.35 Mn 0.65 (OH)2, D 50 The core surface of the nickel-based cathode material precursor, which has a loose porous structure, is sequentially coated with four shell layers of different thicknesses that also have loose porous structures, with a thickness of 10 μm.

[0025] Compared with existing technologies, this invention has the following advantages and beneficial effects: This invention eliminates the need for additional pore-forming agents or specific organic raw materials and additives, and can directly achieve the preparation of multi-shell porous core-shell structure nickel-based cathode material precursors through partial reaction control of the precursor. In the precursor preparation process of this invention, the reaction is initiated in a seed reactor to provide a porous seed core of the required specific size with good sphericity for the subsequent reactor. The reaction continues in the reactor to control reaction parameters and achieve the coating of the core with a loosely porous multi-shell structure. Both the seed reactor and the reactor are connected to concentration tanks to increase the solid content within both reactors, thereby achieving the goal of controlling the precursor particle size to 5~16μm. Furthermore, the multi-shell structure of the nickel-based cathode material precursor prepared by this invention enables the final cathode material to have multiple lithium-ion diffusion channels, which can buffer the lattice mechanical strain force of the cathode material during charging and discharging, thereby effectively improving cycle stability. The multi-shell structure of the cathode material prepared based on the nickel-based cathode material precursor with loose pores can store more electrolyte, thereby improving cycle performance during charging and discharging. The loose porous structure of the cathode material prepared based on the nickel-based cathode material precursor with loose pores can provide more storage space under the overcharge condition of lithium-ion battery, thereby improving its safety performance. Attached Figure Description

[0026] Figure 1 This is a process flow diagram of the present invention.

[0027] Figure 2 The image shows the SEM image of the precursor obtained in Example 1.

[0028] Figure 3 A cross-sectional SEM image of the precursor prepared in Example 1.

[0029] Figure 4 This is a schematic diagram of the precursor prepared in Example 1.

[0030] Figure 5 A cross-sectional SEM image of the precursor prepared for Comparative Example 1.

[0031] Figure 6 A cross-sectional SEM image of the precursor was prepared for Comparative Example 2. Detailed Implementation

[0032] The following examples further illustrate the above-described content of the present invention, but it should not be construed as limiting the scope of the subject matter of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Example 1

[0033] Step S1: Prepare a soluble mixed metal salt solution with a total concentration of 2.1 mol / L, i.e., solution A, wherein the soluble mixed metal salt is a mixed salt of nickel sulfate and manganese sulfate with a molar ratio of Ni:Mn=0.35:0.65; prepare a sodium hydroxide solution with a concentration of 5.5 mol / L, i.e. solution B; and prepare an ammonia solution with a concentration of 7 mol / L, i.e. solution C.

[0034] Step S2: Add deionized water to the seed crystal reactor, making up 40% of the reactor's volume. Heat the reactor to 40°C and start stirring at 600 rpm. Introduce nitrogen gas as a protective gas into the reactor at a flow rate of 4 m³ / min. 3 The nitrogen gas was introduced at a rate of 600 L / h for 40 min. Then, solutions A, B, and C were continuously fed into the seed crystal reactor for reaction. The flow rates of solution A, B, and C were controlled at 435 L / h and 15 L / h, respectively. The pH of the reaction system was 11. When the total liquid in the seed crystal reactor reached 90% of its volume, the material in the seed crystal reactor was transferred to a concentration tank for concentration. The filter element in the concentration tank had a pore size of 0.2 μm. The clear liquid in the concentration tank was discharged directly from the outlet. The concentrated material was returned to the seed crystal reactor to continue the reaction. The continuous reaction time in the seed crystal reactor was 55 h, and finally, a seed slurry was obtained with an average seed particle size of 2.7 μm.

[0035] Step S3: Add the seed slurry and sodium sulfate solution from the seed tank described in Step S2 to the reaction vessel to form a mixed system. The pH of this mixed system is 11, and its volume accounts for 45% of the reaction vessel volume. Heat the reaction vessel to 50°C and start stirring at a speed of 350 r / min. Then, continuously feed solutions A, B, and C into the reaction vessel for reaction, controlling the flow rate of solution A at 600 L / h, solution B at 435 L / h, and solution C at 15 L / h. During the reaction, continuously reduce the flow rate... The flow rate of solution C was controlled from 15 L / h to 10 L / h to gradually decrease the pH of the reaction system from 11 to 10.5 over a period of 15 h, achieving continuous coating of multiple loose shells on the surface of the seed crystal core. When the total liquid in the reactor reached 90% of the reactor volume, the material in the reactor was transferred to another concentration tank for concentration. The filter element in the concentration tank had a pore size of 0.3 μm, and the clear liquid in the concentration tank was directly discharged from the outlet. The concentrated material was returned to the reactor to continue the reaction. The reaction was continuously circulated within the reactor for 20 h, and finally the precursor slurry was obtained.

[0036] Step S4: The precursor slurry obtained in step S3 is washed with an alkaline solution and deionized water, and then centrifuged to obtain a filter cake. The filter cake contains SO4. 2- The content is 2000~3500ppm, Na +The content was 300 ppm. After drying the filter cake at 100℃, a multi-shell porous core-shell structure nickel-based cathode material precursor was obtained. The chemical formula of the nickel-based cathode material precursor is Ni. 0.35 Mn 0.65 (OH)2, D 50 It is 10μm, by Figure 2 It can be seen that the core surface of the prepared nickel-based cathode material precursor, which has a loose porous structure, is sequentially covered with four shell layers of different thicknesses, each having a loose porous structure.

[0037] Comparative Example 1 (without continuously reducing the flow rate of the complexing agent solution in step S3)

[0038] Step S1: Prepare a soluble mixed metal salt solution with a total concentration of 2.1 mol / L, i.e., solution A, wherein the soluble mixed metal salt is a mixed salt of nickel sulfate and manganese sulfate with a molar ratio of Ni:Mn=0.35:0.65; prepare an alkaline solution with a concentration of 5.5 mol / L, i.e. solution B; and prepare a complexing agent solution with a concentration of 7 mol / L, i.e. solution C.

[0039] Step S2: Add deionized water to the seed crystal reactor, making up 40% of the reactor's volume. Heat the reactor to 40°C and start stirring at 600 rpm. Introduce nitrogen gas as a protective gas into the reactor at a flow rate of 4 m³ / min. 3 The nitrogen gas was introduced at a rate of 600 L / h for 40 min. Then, solutions A, B, and C were continuously fed into the seed crystal reactor for reaction. The flow rates of solution A, B, and C were controlled at 435 L / h and 15 L / h, respectively. The pH of the reaction system was 11. When the total liquid in the seed crystal reactor reached 90% of its volume, the material in the seed crystal reactor was transferred to a concentration tank for concentration. The filter element in the concentration tank had a pore size of 0.2 μm. The clear liquid in the concentration tank was discharged directly from the outlet. The concentrated material was returned to the seed crystal reactor to continue the reaction. The continuous reaction time in the seed crystal reactor was 55 h, and finally, a seed slurry was obtained with an average seed particle size of 2.7 μm.

[0040] Step S3: Add the seed slurry and sodium sulfate solution from the seed tank in step S2 to the reactor to form a mixed system. The pH of the mixed system is 11, and the volume of the mixed system accounts for 45% of the reactor volume. Heat the reactor to 50°C and start stirring at a speed of 350 r / min. Then, continuously feed solutions A, B, and C into the reactor for reaction, controlling the flow rate of solution A to 600 L / h, the flow rate of solution B to 435 L / h, and the flow rate of solution C to 15 L / h. When the total liquid in the reactor reaches 90% of the reactor volume, transfer the material in the reactor to another concentration tank for concentration. The filter element in the concentration tank has a pore size of 0.3 μm. The clear liquid in the concentration tank is directly discharged from the outlet. The concentrated material is returned to the reactor to continue the reaction. The continuous reaction time in the reactor is 20 h, and finally the precursor slurry is obtained.

[0041] Step S4: The precursor slurry obtained in step S3 is washed with an alkaline solution and deionized water, then centrifuged to obtain a filter cake. The filter cake is then dried at 100°C to obtain the nickel-based cathode material precursor. Figure 5 It can be seen that the flow rate of the complexing agent participates in the reaction at a constant value, and the internal structure of the material is only a single, denser shell, which cannot provide a large number of pores.

[0042] Comparative Example 2 (Neither the seed crystal reactor nor the reaction vessel is connected to the concentration tank)

[0043] Step S1: Prepare a soluble mixed metal salt solution with a total concentration of 2.1 mol / L, i.e., solution A, wherein the soluble mixed metal salt is a mixed salt of nickel sulfate and manganese sulfate with a molar ratio of Ni:Mn=0.35:0.65; prepare an alkaline solution with a concentration of 5.5 mol / L, i.e. solution B; and prepare a complexing agent solution with a concentration of 7 mol / L, i.e. solution C.

[0044] Step S2: Add deionized water to the seed crystal reactor, making up 40% of the reactor's volume. Heat the reactor to 40°C and start stirring at 600 rpm. Introduce nitrogen gas as a protective gas into the reactor at a flow rate of 4 m³ / min. 3 The nitrogen gas was introduced at a rate of 600 L / h for 40 min. Then, solutions A, B, and C were continuously fed into the seed crystal reactor for reaction. The flow rates of solution A, B, and C were controlled at 600 L / h, 435 L / h, and 15 L / h, respectively. The pH of the reaction system was 11, and the reaction time in the seed crystal reactor was 55 h, finally yielding the seed crystal slurry.

[0045] Step S3: Add the seed slurry and sodium sulfate solution from the seed tank in step S2 to the reactor to form a mixed system. The pH of the mixed system is 11, and the volume of the mixed system accounts for 45% of the reactor volume. Heat the reactor to 50°C and start stirring at a speed of 350 r / min. Then, continuously feed solutions A, B, and C into the reactor for reaction. Control the flow rate of solution A at 600 L / h, the flow rate of solution B at 435 L / h, and the flow rate of solution C at 15 L / h. During the reaction, control the pH of the reaction system to decrease in stages (11→10.5) by continuously reducing the flow rate of solution C (15 L / h→10 L / h) for 15 hours. The reaction time is 20 hours, and finally the precursor slurry is obtained.

[0046] Step S4: The precursor slurry obtained in step S3 is washed with an alkaline solution and deionized water, then centrifuged to obtain a filter cake. The filter cake is then dried at 100°C to obtain the nickel-based cathode material precursor. Figure 6 It is evident that without concentration, a well-shaped nucleus cannot be provided, resulting in irregular particles with a chaotic internal structure in subsequent reaction stages.

[0047] 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 embodiments and descriptions in the specification are only illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from the scope of the principles of the present invention, and all such changes and modifications fall within the protection scope of the present invention.

Claims

1. A method for preparing a multi-shell porous core-shell structured nickel-based cathode material precursor, characterized in that... The specific preparation steps are as follows: Step S1: Prepare a soluble mixed metal salt solution with a total concentration of 0.6–2.8 mol / L, wherein the soluble mixed metal salt is a mixture containing one or more of soluble nickel salt and soluble manganese salt, soluble cobalt salt, or soluble aluminum salt. Then, prepare an alkaline solution with a concentration of 2–10 mol / L and a complexing agent solution with a concentration of 3–11 mol / L, respectively. The soluble nickel salt is one or more of nickel sulfate, nickel chloride, nickel nitrate, or nickel carbonate; the soluble manganese salt is one or more of manganese sulfate or manganese chloride; the soluble cobalt salt is one or more of cobalt sulfate, cobalt chloride, cobalt acetate, or cobalt nitrate; the soluble aluminum salt is one or more of aluminum chloride, aluminum sulfate, or sodium aluminate; the alkaline solution is one or more of sodium hydroxide solution or potassium hydroxide solution; and the complexing agent solution is an ammonia solution or a citric acid solution. Step S2: Add deionized water to the seed crystal reactor, making up 40%–80% of the reactor's volume. Heat the reactor to 35–70°C and start stirring. Introduce a protective gas into the reactor. Then, continuously feed the soluble mixed metal salt solution, alkaline solution, and complexing agent solution into the reactor for reaction. Control the flow rate of the soluble mixed metal salt solution to 60–600 L / h, the flow rate of the alkaline solution to 24–550 L / h, and the flow rate of the complexing agent solution to 1 L / h. The reaction rate is ~300L / h, the pH of the reaction system is 10.0~12.5, and when the total liquid in the seed crystal reactor reaches 90% of the seed crystal reactor volume, the material in the seed crystal reactor is transferred to the concentration tank for concentration. The concentrated material is then returned to the seed crystal reactor to continue the reaction. The continuous reaction time in the seed crystal reactor is 20~60h, and finally the seed crystal slurry is obtained. The pore size of the filter element in the concentration tank is 0.1~0.3μm, and the final seed crystal particle size is 1.5~3.8μm. Step S3: Add the seed slurry and sodium sulfate solution from the seed tank described in Step S2 to the reaction vessel to form a mixed system. The pH of this mixed system is 10.0–12.5, and the volume of the mixed system accounts for 40%–80% of the reaction vessel volume. Heat the reaction vessel to 40–65°C and start stirring. Then, continuously feed the soluble mixed metal salt solution, alkaline solution, and complexing agent solution into the reaction vessel for reaction. Control the flow rate of the soluble mixed metal salt solution to 60–600 L / h, the flow rate of the alkaline solution to 24–550 L / h, and the flow rate of the complexing agent solution to 1–300 L / h. / h, during the reaction process, the pH of the reaction system is controlled to decrease in stages by continuously reducing the flow rate of the complexing agent solution, thereby achieving continuous coating of multiple loose shells on the surface of the seed core. When the total liquid in the reactor reaches 90% of the reactor volume, the material in the reactor is transferred to another concentration tank for concentration. The concentrated material is returned to the reactor to continue the reaction. The continuous reaction time in the internal circulation is 10 to 60 hours, and finally the precursor slurry is obtained. The pore size of the filter element in the concentration tank is 0.1 to 0.5 μm, and the particle size of the nickel-based cathode material precursor is 5 to 16 μm. Step S4: The precursor slurry obtained in step S3 is washed with an alkaline solution and deionized water, and then centrifuged to obtain a filter cake. The filter cake contains SO4. 2- The content is 1500-3500 ppm, Na + The content is ≤400ppm, and then the filter cake is dried to obtain a multi-shell porous core-shell structure nickel-based cathode material precursor.

2. The method for preparing the multi-shell porous core-shell structure nickel-based cathode material precursor according to claim 1, characterized in that: The filter elements in the concentration tanks in steps S2 and S3 are made of polypropylene or polyethylene.

3. The method for preparing the multi-shell porous core-shell structure nickel-based cathode material precursor according to claim 1, characterized in that: The stirring rate of the seed crystal vessel in step S2 is 200-650 r / min, and the stirring rate of the reaction vessel in step S3 is 100-600 r / min.

4. The method for preparing the multi-shell porous core-shell structure nickel-based cathode material precursor according to claim 1, characterized in that: The protective gas mentioned in step S2 is nitrogen with a purity ≥ 99.99%, and the flow rate of the protective gas is 2-10 m³ / s. 3 / h, the time for introducing protective gas is 30 to 60 minutes.

5. The method for preparing the multi-shell porous core-shell structure nickel-based cathode material precursor according to claim 1, characterized in that: The nickel-based cathode material precursor mentioned in step S4 is a spherical nickel-cobalt hydroxide, a spherical nickel-manganese hydroxide, a spherical nickel-cobalt-manganese hydroxide, a spherical nickel-cobalt-aluminum hydroxide, or a spherical nickel-cobalt-manganese-aluminum hydroxide, with the corresponding chemical formula Ni. x Co 1-x (OH)2, Ni x Mn 1-x (OH)2, Ni x Co y Mn 1-x-y (OH)2, Ni x Co y Al 1-x-y (OH)2 or Ni x Co y Mn Z Al 1-x-y-Z (OH) 2+(1-x-y-z) , of which 0.10 <x<0.98、0.01<y<0.7、0.01<z<0.50。 6. The method for preparing the multi-shell porous core-shell structure nickel-based cathode material precursor according to claim 1, characterized in that: Step S1: Prepare a soluble mixed metal salt solution with a total concentration of 2.1 mol / L, i.e., solution A, wherein the soluble mixed metal salt is a mixed salt of nickel sulfate and manganese sulfate with a molar ratio of Ni:Mn = 0.35:0.65; prepare a sodium hydroxide solution with a concentration of 5.5 mol / L, i.e. solution B; and prepare an ammonia solution with a concentration of 7 mol / L, i.e. solution C. Step S2: Add deionized water to the seed crystal reactor, making up 40% of the reactor's volume. Heat the reactor to 40°C and start stirring at 600 rpm. Introduce nitrogen gas as a protective gas into the reactor at a flow rate of 4 m³ / min. 3 The nitrogen gas flow rate was 40 min, and solutions A, B, and C were continuously fed into the seed crystal reactor for reaction. The flow rates of solution A, B, and C were controlled at 600 L / h, 435 L / h, and 15 L / h, respectively. The pH of the reaction system was 11. When the total liquid in the seed crystal reactor reached 90% of its volume, the material in the seed crystal reactor was transferred to a concentration tank for concentration. The filter element in the concentration tank had a pore size of 0.2 μm. The clear liquid in the concentration tank was discharged directly from the outlet. The concentrated material was returned to the seed crystal reactor for further reaction. The continuous reaction time in the seed crystal reactor was 55 h, and finally, a seed slurry was obtained with an average seed particle size of 2.7 μm. Step S3: Add the seed slurry and sodium sulfate solution from the seed tank described in Step S2 to the reaction vessel to form a mixed system. The pH of this mixed system is 11, and its volume accounts for 45% of the reaction vessel volume. Heat the reaction vessel to 50°C and start stirring at a speed of 350 r / min. Then, continuously feed solutions A, B, and C into the reaction vessel for reaction, controlling the flow rate of solution A at 600 L / h, solution B at 435 L / h, and solution C at 15 L / h. During the reaction, continuously reduce the flow rate... The flow rate of solution C was controlled from 15 L / h to 10 L / h, and the pH of the reaction system was gradually decreased from 11 to 10.5 over a period of 15 h. This achieved continuous coating of the seed core with multiple loose shells. When the total liquid in the reactor reached 90% of the reactor volume, the material in the reactor was transferred to another concentration tank for concentration. The filter element in the concentration tank had a pore size of 0.3 μm. The clear liquid in the concentration tank was discharged directly from the outlet. The concentrated material was returned to the reactor to continue the reaction. The reaction was continuously circulated within the reactor for 20 h, and finally the precursor slurry was obtained. Step S4: The precursor slurry obtained in step S3 is washed with an alkaline solution and deionized water, and then centrifuged to obtain a filter cake. The filter cake contains SO4. 2- The content is 2000-3500 ppm, Na + The content was 300 ppm. After drying the filter cake at 100℃, a multi-shell porous core-shell structure nickel-based cathode material precursor was obtained. The chemical formula of the nickel-based cathode material precursor is Ni. 0.35 Mn 0.65 (OH)2, D 50 The core surface of the nickel-based cathode material precursor prepared with a porous structure is sequentially coated with four shell layers of different thicknesses and porous structures. The core surface has a porous structure and a porous structure ...

Images