Preparation method of nickel-based positive electrode material precursor with multi-shell loose porous core-shell structure

Abstract

The invention discloses a preparation method of a nickel-based positive electrode material precursor with a multi-shell porous core-shell structure, the method directly realizes preparation of the nickel-based positive electrode material precursor with the multi-shell porous core-shell structure through partial reaction control of the precursor, and a seed crystal kettle and a reaction kettle are respectively connected with a concentration tank to realize particle size control of the precursor. In the precursor preparation stage, the flow of the complexing agent solution is continuously reduced to control the pH stage reduction of the reaction system, so that the continuous coating of the multi-layer loose shell layer on the surface of the seed crystal core is realized. The multi-shell structure in the positive electrode material prepared on the basis of the multi-shell porous core-shell structure nickel-based positive electrode material precursor with loose holes can store more electrolyte, so that the cycle performance in the charge-discharge process is improved; the loose porous structure in the positive electrode material prepared on the basis of the multi-shell porous core-shell structure nickel-based positive electrode material precursor with the loose holes can provide more storage and accommodation space under the condition of overcharge of the lithium ion battery, so that the safety performance of the lithium ion battery is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of new processes for preparing nickel-based positive electrode material precursors for lithium-ion batteries, and specifically relates to a method for preparing a nickel-based positive electrode material precursor with a multi-shell loose porous core-shell structure. Background Art

[0002] In recent years, 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 continued to increase 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] At present, more and more attention and research are being paid to positive electrode materials with porous structures. Porous positive electrode materials have the following advantages: first, the porous structure of porous positive electrode materials can store more electrolytes and effectively improve the cycle performance during the charge and discharge process; second, the porous structure of porous positive electrode materials can provide more storage space under the overcharge condition of lithium-ion batteries, thereby effectively improving their safety performance. At present, the pore structure of the porous precursor in the existing technology is uncontrollable.

[0004] After reviewing the preparation methods of porous positive electrode materials reported in many documents, most of the literature technologies are to add porous carbon and carbon nanotube dispersions during the preparation of the positive electrode material precursor, and the porous carbon and carbon nanotubes are decomposed and removed under high temperature conditions during the later sintering of the positive electrode material, leaving a pore structure inside the positive electrode material to obtain a porous positive electrode material. For example, the patent document CN116924487A discloses a porous precursor material and its preparation method and application. In the preparation process of the precursor material, by introducing a pore-forming agent and cooperating with a two-step method, the pores can be evenly distributed inside the precursor material, increasing the diffusion channel of lithium ions and giving full play to the capacity of the positive electrode material. However, this technical solution requires the additional addition of a pore-forming agent, which is cumbersome and relatively costly.

[0005] The patent document of CN103178262A discloses a ternary precursor and a preparation method thereof, and a positive electrode material, wherein the ternary precursor is nickel-cobalt-manganese hydroxide; the ternary precursor includes a core layer, a shell layer, and a multilayer connecting layer located between the core layer and the shell layer, and its specific preparation process makes the core layer and the shell layer of the ternary precursor finally prepared have a dense structure, and the multilayer connecting layer has a relatively loose structure. It can be seen from the cross-sectional electron microscope image provided that the internal structure of the precursor prepared by the patent document is dense, which is not conducive to mixed sintering with lithium salt to form a multi-lithium ion diffusion channel, and is not conducive to the coated modified elements entering the surface of the primary particles. This technical solution cannot highlight the advantages of the improved precursor.

[0006] Patent document CN115367815B discloses a multi-layer annular hole nickel-cobalt-aluminum precursor and a preparation method and a positive electrode material thereof, wherein the precursor D 50 The diameter of the secondary spherical particles is 8~20μm. From the cross-sectional electron microscope image, it can be seen that there are multiple layers of annular holes in the secondary spherical particle structure, and the porosity value of a single particle or multiple particles is 6%~14% on average. The preparation process is to co-precipitate the nickel-cobalt mixed salt solution, alkali-aluminum solution, complexing agent, and precipitant, strictly control the pH value and aluminum liquid concentration at each stage, and then perform solid-liquid separation, washing, drying, mixing, screening, and demagnetization to obtain a nickel-cobalt-aluminum precursor with multiple layers of annular holes. This patented technical solution is used to improve the lithium ion diffusion channel and the lithium ion diffusion rate. From the cross-sectional electron microscope image provided, it can be seen that the prepared precursor shell structure is relatively dense, which is not conducive to mixed sintering with lithium salts to form multiple lithium ion diffusion channels, and is not conducive to the coated modified elements entering the surface of the primary particles. This technical solution cannot highlight the advantages of the improved precursor. Summary of the invention

[0007] The technical problem solved by the present invention is to provide a method for preparing a multi-shell porous core-shell structure nickel-based positive electrode material precursor. The method does not require the additional addition of pore-forming agents or specific organic raw materials and additives, and can directly realize the preparation of the multi-shell porous core-shell structure nickel-based positive electrode material precursor through partial reaction control of the precursor. Based on the multi-shell structure of the nickel-based positive electrode material precursor, the finally obtained positive electrode material has multi-layer lithium ion diffusion channels, which can buffer the lattice mechanical strain of the positive electrode material during the charge and discharge process, thereby effectively improving the cycle stability performance. The multi-shell structure in the positive electrode material prepared based on the multi-shell porous core-shell structure nickel-based positive electrode material precursor with loose pores can store more electrolyte and thus improve the cycle performance of the charge and discharge process; the loose porous structure in the positive electrode material prepared based on the multi-shell porous core-shell structure nickel-based positive electrode material precursor with loose pores can provide more storage and accommodation space under the overcharge condition of the lithium ion battery, thereby improving its safety performance.

[0008] The present invention adopts the following technical solution to solve the above technical problems, a method for preparing a multi-shell porous core-shell structure nickel-based positive electrode material precursor, and its specific preparation steps are: Step S1: preparing 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 a soluble nickel salt and a soluble manganese salt, a soluble cobalt salt or a soluble aluminum salt, and then preparing 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; Step S2: adding deionized water into the seed kettle, the deionized water accounting for 40% to 80% of the volume of the seed kettle, heating the seed kettle to 35 to 70° C. and stirring, introducing protective gas into the seed kettle, and then continuously conveying the soluble mixed metal salt solution, the alkaline solution and the complexing agent solution into the seed kettle for reaction, controlling 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, the flow rate of the complexing agent solution to 1 to 300 L / h, the pH of the reaction system to 10.0 to 12.5, and when the total liquid in the seed kettle reaches 90% of the volume of the seed kettle, conveying the material in the seed kettle to a concentration tank for concentration, and the concentrated material is refluxed into the seed kettle for continuous reaction, and the continuous reaction time in the seed kettle is 20 to 60 hours, and finally obtaining a seed slurry; Step S3: adding the seed slurry and sodium sulfate solution in the seed kettle of step S2 into the reactor to form a mixed system, wherein the pH of the mixed system is 10.0-12.5, and the volume of the mixed system accounts for 40%-80% of the volume of the reactor, heating the reactor to 40-65° C. and stirring, and then continuously conveying the soluble mixed metal salt solution, the alkaline solution and the complexing agent solution into the reactor for reaction, controlling 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 ~550L / h, the flow rate of the complexing agent solution is 1~300L / h, and the pH of the reaction system is controlled to decrease in stages by continuously reducing the flow rate of the complexing agent solution during the reaction process, thereby achieving continuous coating of the surface of the seed core with multiple loose shells. When the total liquid in the reactor reaches 90% of the volume of the reactor, the material in the reactor is transported to another concentration tank for concentration, and the concentrated material is refluxed into the reactor to continue the reaction. The continuous reaction time in the reactor is 10~60h, and finally a precursor slurry is 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. 2- 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 positive electrode material precursor.

[0009] It is further defined that 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; the soluble aluminum salt is one or more of aluminum chloride, aluminum sulfate or sodium aluminate.

[0010] It is further defined that the alkaline solution in step S1 is one or more of a sodium hydroxide solution or a potassium hydroxide solution.

[0011] It is further defined that the complexing agent solution in step S1 is an ammonia solution or a citric acid solution.

[0012] It is further defined that the pore size of the filter element in the concentration tank in step S2 is 0.1~0.3μm, and the final particle size of the seed crystal 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 particle size of the nickel-based positive electrode material precursor is 5~16μm, and the material of the filter element in the concentration tank is polypropylene or polyethylene.

[0013] It is further defined that the stirring rate of the seed kettle in step S2 is 200-650 r / min, and the stirring rate of the reaction kettle in step S3 is 100-600 r / min.

[0014] It is further defined that the protective gas in step S2 is nitrogen with a purity of ≥99.99%, and the flow rate of the protective gas is 2-10m 3 / h, the time for introducing protective gas is 30~60min.

[0015] It is further defined that the nickel-based positive electrode material precursor in step S4 is spherical nickel cobalt hydroxide, spherical nickel manganese hydroxide, spherical nickel cobalt manganese hydroxide, spherical nickel cobalt aluminum hydroxide or spherical nickel cobalt manganese aluminum hydroxide, and the corresponding chemical formula is 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), where 0.10 <x<0.98、0.01<y<0.7、0.01<z<0.50。

[0016] Further defined, a method for preparing a multi-shell porous core-shell structure nickel-based positive electrode material precursor, the specific preparation steps of which are: Step S1: preparing a soluble mixed metal salt solution with a total concentration of 2.1 mol / L, namely 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, preparing a sodium hydroxide solution with a concentration of 5.5 mol / L, namely solution B, and preparing an ammonia solution with a concentration of 7 mol / L, namely solution C; Step S2: Add deionized water to the seed kettle, the deionized water accounts for 40% of the volume of the seed kettle, heat the seed kettle to 40°C and start stirring, the stirring speed is 600r / min, and introduce protective gas nitrogen into the seed kettle, the flow rate of the nitrogen is 4m 3 / h, the time for introducing nitrogen is 40min, and then solution A, solution B and solution C are continuously transported to the seed kettle for reaction, the flow rate of solution A is controlled to be 600L / h, the flow rate of solution B is 435L / h, the flow rate of solution C is 15L / h, the pH of the reaction system is 11, and when the total liquid in the seed kettle reaches 90% of the volume of the seed kettle, the material in the seed kettle is transported to the concentration tank for concentration, the pore size of the filter element in the concentration tank is 0.2μm, and the clear liquid in the concentration tank is directly discharged from the liquid outlet, and the concentrated material is refluxed to the seed kettle for continuous reaction, and the continuous reaction time in the seed kettle is 55h, and finally a seed slurry is obtained, and the average particle size of the seed is 2.7μm; Step S3: adding the seed slurry and sodium sulfate solution in the seed kettle of step S2 into the reactor to form a mixed system, wherein the pH of the mixed system is 11, and the volume of the mixed system accounts for 45% of the volume of the reactor, heating the reactor to 50°C and starting stirring, the stirring speed is 350r / min, and then continuously conveying solution A, solution B and solution C to the reactor for reaction, respectively, controlling the flow rate of solution A to 600L / h, the flow rate of solution B to 435L / h, and the flow rate of solution C to 15L / h, and continuously reducing the flow rate of solution A to 600L / h, the flow rate of solution B to 435L / h, and the flow rate of solution C to 15L / h during the reaction. The flow rate of solution C was 15L / h→10L / h, and the pH of the reaction system was controlled to decrease from 11→10.5 in stages, which lasted for 15 hours, to achieve continuous coating of the surface of the seed core with multiple loose shell layers. When the total liquid in the reactor reached 90% of the volume of the reactor, the material in the reactor was transported to another concentration tank for concentration. The pore size of the filter element in the concentration tank was 0.3μm, and the clear liquid in the concentration tank was directly discharged from the liquid outlet. The concentrated material was refluxed into the reactor to continue the reaction. The continuous reaction time in the reaction cycle was 20 hours, and finally a 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. 2- Content is 2000~3500ppm, Na + The content is 300ppm, and the filter cake is dried at 100°C to obtain a multi-shell porous core-shell structure nickel-based positive electrode material precursor. The chemical formula of the nickel-based positive electrode material precursor is Ni 0.35 Mn 0.65 (OH) 2 , D 50 The surface of the inner core with a loose pore structure in the prepared nickel-based positive electrode material precursor is sequentially coated with 4 shell layers with a loose pore structure and different thicknesses.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects: the present invention does not require the additional addition of pore-forming agents or specific organic raw materials and additives, and can directly realize the preparation of a multi-shell porous core-shell structure nickel-based positive electrode material precursor through partial reaction control of the precursor. In the precursor preparation process of the present invention, the reaction is started in the seed kettle, the purpose of which is to provide a porous seed kernel of a required specific size with good sphericity for the subsequent reactor; the reaction is continued in the reactor, the purpose of which is to achieve a multi-shell structure with loose holes on the kernel by controlling the reaction parameters, and the seed kettle and the reactor are both connected to a concentration tank to increase the solid content in the seed kettle and the reactor, thereby achieving the purpose of controlling the precursor particle size to 5~16μm. In addition, the multi-shell structure of the nickel-based positive electrode material precursor prepared by the present invention enables the final positive electrode material to have multi-layer lithium ion diffusion channels, which can buffer the lattice mechanical strain of the positive electrode material during the charge and discharge process, thereby effectively improving the cycle stability performance. The multi-shell structure in the positive electrode material prepared based on the multi-shell porous core-shell structure nickel-based positive electrode material precursor with loose pores can store more electrolyte and thus improve the cycle performance during the charge and discharge process; the loose porous structure in the positive electrode material prepared based on the multi-shell porous core-shell structure nickel-based positive electrode material precursor with loose pores can provide more storage and accommodation space under the overcharge condition of the lithium-ion battery, thereby improving its safety performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a process flow chart of the present invention.

[0019] Figure 2 This is the SEM image of the precursor prepared in Example 1.

[0020] Figure 3 This is a cross-sectional SEM image of the precursor prepared in Example 1.

[0021] Figure 4 This is a schematic diagram of the structure of the precursor prepared in Example 1.

[0022] Figure 5 This is a cross-sectional SEM image of the precursor prepared in Comparative Example 1.

[0023] Figure 6 This is a cross-sectional SEM image of the precursor prepared in Comparative Example 2. DETAILED DESCRIPTION

[0024] 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

[0025] Step S1: preparing a soluble mixed metal salt solution with a total concentration of 2.1 mol / L, namely 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, preparing a sodium hydroxide solution with a concentration of 5.5 mol / L, namely solution B, and preparing an ammonia solution with a concentration of 7 mol / L, namely solution C; Step S2: Add deionized water to the seed kettle, the deionized water accounts for 40% of the volume of the seed kettle, heat the seed kettle to 40°C and start stirring, the stirring speed is 600r / min, and introduce protective gas nitrogen into the seed kettle, the flow rate of the nitrogen is 4m 3 / h, the time for introducing nitrogen is 40min, and then solution A, solution B and solution C are continuously transported to the seed kettle for reaction, the flow rate of solution A is controlled to be 600L / h, the flow rate of solution B is 435L / h, the flow rate of solution C is 15L / h, the pH of the reaction system is 11, and when the total liquid in the seed kettle reaches 90% of the volume of the seed kettle, the material in the seed kettle is transported to the concentration tank for concentration, the pore size of the filter element in the concentration tank is 0.2μm, and the clear liquid in the concentration tank is directly discharged from the liquid outlet, and the concentrated material is refluxed to the seed kettle for continuous reaction, and the continuous reaction time in the seed kettle is 55h, and finally a seed slurry is obtained, and the average particle size of the seed is 2.7μm; Step S3: adding the seed slurry and sodium sulfate solution in the seed kettle of step S2 into the reactor to form a mixed system, wherein the pH of the mixed system is 11, and the volume of the mixed system accounts for 45% of the volume of the reactor, heating the reactor to 50°C and starting stirring, the stirring speed is 350r / min, and then continuously conveying solution A, solution B and solution C to the reactor for reaction, respectively, controlling the flow rate of solution A to 600L / h, the flow rate of solution B to 435L / h, and the flow rate of solution C to 15L / h, and continuously reducing the flow rate of solution A to 600L / h, the flow rate of solution B to 435L / h, and the flow rate of solution C to 15L / h during the reaction. The flow rate of solution C was 15L / h→10L / h, and the pH of the reaction system was controlled to decrease from 11→10.5 in stages, which lasted for 15 hours, to achieve continuous coating of the surface of the seed core with multiple loose shell layers. When the total liquid in the reactor reached 90% of the volume of the reactor, the material in the reactor was transported to another concentration tank for concentration. The pore size of the filter element in the concentration tank was 0.3μm, and the clear liquid in the concentration tank was directly discharged from the liquid outlet. The concentrated material was refluxed into the reactor to continue the reaction. The continuous reaction time in the reaction cycle was 20 hours, and finally a 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. 2- Content is 2000~3500ppm, Na + The content is 300ppm, and the filter cake is dried at 100°C to obtain a multi-shell porous core-shell structure nickel-based positive electrode material precursor. The chemical formula of the nickel-based positive electrode material precursor is Ni 0.35 Mn 0.65 (OH) 2 , D 50 is 10μm, Figure 2 It can be seen that the surface of the inner core with a loose porous structure in the prepared nickel-based positive electrode material precursor is sequentially coated with 4 shell layers with a loose porous structure and different thicknesses.

[0026] Comparative Example 1 (Not Continuously Reducing the Flow Rate of Complexing Agent Solution in Step S3) Step S1: preparing a soluble mixed metal salt solution with a total concentration of 2.1 mol / L, namely 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, preparing an alkali solution with a concentration of 5.5 mol / L, namely solution B, and preparing a complexing agent solution with a concentration of 7 mol / L, namely solution C; Step S2: Add deionized water to the seed kettle, the deionized water accounts for 40% of the volume of the seed kettle, heat the seed kettle to 40°C and start stirring, the stirring speed is 600r / min, and introduce protective gas nitrogen into the seed kettle, the flow rate of the nitrogen is 4m 3 / h, the time for introducing nitrogen is 40min, and then solution A, solution B and solution C are continuously transported to the seed kettle for reaction, the flow rate of solution A is controlled to be 600L / h, the flow rate of solution B is 435L / h, the flow rate of solution C is 15L / h, the pH of the reaction system is 11, and when the total liquid in the seed kettle reaches 90% of the volume of the seed kettle, the material in the seed kettle is transported to the concentration tank for concentration, the pore size of the filter element in the concentration tank is 0.2μm, and the clear liquid in the concentration tank is directly discharged from the liquid outlet, and the concentrated material is refluxed to the seed kettle for continuous reaction, and the continuous reaction time in the seed kettle is 55h, and finally a seed slurry is obtained, and the average particle size of the seed is 2.7μm; Step S3: adding the seed slurry and sodium sulfate solution in the seed kettle described in step S2 into 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 volume of the reactor. The reactor is heated to 50°C and stirred at a stirring speed of 350r / min. Then, solution A, solution B and solution C are continuously transported to the reactor for reaction, respectively, and the flow rate of solution A is controlled to be 600L / h, the flow rate of solution B is controlled to be 435L / h, and the flow rate of solution C is controlled to be 15L / h. When the total liquid in the reactor reaches 90% of the volume of the reactor, the material in the reactor is transported to another concentration tank for concentration. The pore size of the filter element in the concentration tank is 0.3μm, and the clear liquid in the concentration tank is directly discharged from the liquid outlet. The concentrated material is refluxed into the reactor to continue to react. The continuous reaction time in the reaction vessel is 20h, and finally a precursor slurry is 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, and then the filter cake is dried at 100° C. to obtain a nickel-based positive electrode material precursor. Figure 5 It can be seen that the complexing agent flow rate participates in the reaction at a constant value, and the internal structure of the material only has a single denser shell layer, which cannot provide more pore sizes.

[0027] Comparative Example 2 (Neither the seed kettle nor the reactor is connected to the concentration tank) Step S1: preparing a soluble mixed metal salt solution with a total concentration of 2.1 mol / L, namely 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, preparing an alkali solution with a concentration of 5.5 mol / L, namely solution B, and preparing a complexing agent solution with a concentration of 7 mol / L, namely solution C; Step S2: Add deionized water to the seed kettle, the deionized water accounts for 40% of the volume of the seed kettle, heat the seed kettle to 40°C and start stirring, the stirring speed is 600r / min, and introduce protective gas nitrogen into the seed kettle, the flow rate of the nitrogen is 4m 3 / h, the time of introducing nitrogen is 40min, and then solution A, solution B and solution C are continuously transported to the seed kettle for reaction, the flow rate of solution A is controlled to be 600L / h, the flow rate of solution B is 435L / h, the flow rate of solution C is 15L / h, the pH of the reaction system is 11, and the continuous reaction time in the seed kettle is 55h, and finally a seed slurry is obtained; Step S3: adding the seed slurry and sodium sulfate solution in the seed kettle of step S2 into 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 volume of the reactor, heating the reactor to 50°C and stirring, the stirring speed is 350r / min, and then continuously conveying solution A, solution B and solution C to the reactor for reaction, controlling the flow rate of solution A to 600L / h, the flow rate of solution B to 435L / h, and the flow rate of solution C to 15L / h. During the reaction, the pH of the reaction system (11→10.5) is controlled to decrease in stages by continuously reducing the flow rate of solution C (15L / h→10L / h), the duration is 15h, and the reaction time in the reactor is 20h, and finally a precursor slurry is 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, and then the filter cake is dried at 100° C. to obtain a nickel-based positive electrode material precursor. Figure 6 It can be seen that without the concentration operation, a well-spherical core cannot be provided, and irregular particles are formed in the subsequent reaction stage, and the internal structure is relatively disordered.

[0028] 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 a multi-shell porous core-shell structure nickel-based positive electrode material precursor, characterized in that The specific preparation steps are: Step S1: preparing 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 a soluble nickel salt and a soluble manganese salt, a soluble cobalt salt or a soluble aluminum salt, and then preparing 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; Step S2: adding deionized water into the seed kettle, the deionized water accounting for 40% to 80% of the volume of the seed kettle, heating the seed kettle to 35 to 70° C. and stirring, introducing protective gas into the seed kettle, and then continuously conveying the soluble mixed metal salt solution, the alkaline solution and the complexing agent solution into the seed kettle for reaction, controlling 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, the flow rate of the complexing agent solution to 1 to 300 L / h, the pH of the reaction system to 10.0 to 12.5, and when the total liquid in the seed kettle reaches 90% of the volume of the seed kettle, conveying the material in the seed kettle to a concentration tank for concentration, and the concentrated material is refluxed into the seed kettle for continuous reaction, and the continuous reaction time in the seed kettle is 20 to 60 hours, and finally obtaining a seed slurry; Step S3: adding the seed slurry and sodium sulfate solution in the seed kettle of step S2 into the reactor to form a mixed system, wherein the pH of the mixed system is 10.0-12.5, and the volume of the mixed system accounts for 40%-80% of the volume of the reactor, heating the reactor to 40-65° C. and stirring, and then continuously conveying the soluble mixed metal salt solution, the alkaline solution and the complexing agent solution into the reactor for reaction, controlling 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 ~550L / h, the flow rate of the complexing agent solution is 1~300L / h, and the pH of the reaction system is controlled to decrease in stages by continuously reducing the flow rate of the complexing agent solution during the reaction process, thereby achieving continuous coating of the surface of the seed core with multiple loose shells. When the total liquid in the reactor reaches 90% of the volume of the reactor, the material in the reactor is transported to another concentration tank for concentration, and the concentrated material is refluxed into the reactor to continue the reaction. The continuous reaction time in the reactor is 10~60h, and finally a precursor slurry is 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. 2- 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 positive electrode material precursor.

2. The method for preparing a multi-shell porous core-shell structure nickel-based 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 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.

3. The method for preparing a multi-shell porous core-shell structure nickel-based positive electrode material precursor according to claim 1, characterized in that: The alkaline solution in step S1 is one or more of a sodium hydroxide solution or a potassium hydroxide solution.

4. The method for preparing a multi-shell porous core-shell structure nickel-based positive electrode material precursor according to claim 1, characterized in that: The complexing agent solution in step S1 is an ammonia solution or a citric acid solution.

5. The method for preparing a multi-shell porous core-shell structure nickel-based positive electrode material precursor according to claim 1, characterized in that: The pore size of the filter element in the concentration tank described in step S2 is 0.1~0.3μm, and the final particle size of the seed crystal is 1.5~3.8μm; the pore size of the filter element in the concentration tank described in step S3 is 0.1~0.5μm, and the final particle size of the nickel-based positive electrode material precursor is 5~16μm. The material of the filter element in the concentration tank is polypropylene or polyethylene.

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

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

8. The method for preparing a multi-shell porous core-shell structure nickel-based positive electrode material precursor according to claim 1, characterized in that: The nickel-based positive electrode material precursor in step S4 is spherical nickel cobalt hydroxide, spherical nickel manganese hydroxide, spherical nickel cobalt manganese hydroxide, spherical nickel cobalt aluminum hydroxide or spherical nickel cobalt manganese aluminum hydroxide, and the corresponding chemical formula is 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) , where 0.10 <x<0.98、0.01<y<0.7、0.01<z<0.50。 9. The method for preparing a multi-shell porous core-shell structure nickel-based positive electrode material precursor according to claim 1, characterized in that: Step S1: preparing a soluble mixed metal salt solution with a total concentration of 2.1 mol / L, namely 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, preparing a sodium hydroxide solution with a concentration of 5.5 mol / L, namely solution B, and preparing an ammonia solution with a concentration of 7 mol / L, namely solution C; Step S2: Add deionized water to the seed kettle, the deionized water accounts for 40% of the volume of the seed kettle, heat the seed kettle to 40°C and start stirring, the stirring speed is 600r / min, and introduce protective gas nitrogen into the seed kettle, the flow rate of the nitrogen is 4m 3 / h, the time for introducing nitrogen is 40min, and then solution A, solution B and solution C are continuously transported to the seed kettle for reaction, the flow rate of solution A is controlled to be 600L / h, the flow rate of solution B is 435L / h, the flow rate of solution C is 15L / h, the pH of the reaction system is 11, and when the total liquid in the seed kettle reaches 90% of the volume of the seed kettle, the material in the seed kettle is transported to the concentration tank for concentration, the pore size of the filter element in the concentration tank is 0.2μm, and the clear liquid in the concentration tank is directly discharged from the liquid outlet, and the concentrated material is refluxed to the seed kettle for continuous reaction, and the continuous reaction time in the seed kettle is 55h, and finally a seed slurry is obtained, and the average particle size of the seed is 2.7μm; Step S3: adding the seed slurry and sodium sulfate solution in the seed kettle of step S2 into the reactor to form a mixed system, wherein the pH of the mixed system is 11, and the volume of the mixed system accounts for 45% of the volume of the reactor, heating the reactor to 50°C and starting stirring, the stirring speed is 350r / min, and then continuously conveying solution A, solution B and solution C to the reactor for reaction, respectively, controlling the flow rate of solution A to 600L / h, the flow rate of solution B to 435L / h, and the flow rate of solution C to 15L / h, and continuously reducing the flow rate of solution A to 600L / h, the flow rate of solution B to 435L / h, and the flow rate of solution C to 15L / h during the reaction. The flow rate of solution C was 15L / h→10L / h, and the pH of the reaction system was controlled to decrease from 11→10.5 in stages, which lasted for 15 hours, to achieve continuous coating of the surface of the seed core with multiple loose shell layers. When the total liquid in the reactor reached 90% of the volume of the reactor, the material in the reactor was transported to another concentration tank for concentration. The pore size of the filter element in the concentration tank was 0.3μm, and the clear liquid in the concentration tank was directly discharged from the liquid outlet. The concentrated material was refluxed into the reactor to continue the reaction. The continuous reaction time in the reaction cycle was 20 hours, and finally a 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. 2- Content is 2000~3500ppm, Na + The content is 300ppm, and the filter cake is dried at 100°C to obtain a multi-shell porous core-shell structure nickel-based positive electrode material precursor. The chemical formula of the nickel-based positive electrode material precursor is Ni 0.35 Mn 0.65 (OH)2,D 50 The surface of the inner core with a loose pore structure in the prepared nickel-based positive electrode material precursor is sequentially coated with 4 shell layers with a loose pore structure and different thicknesses.

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