Manganese-rich precursor, positive electrode material and preparation method thereof

Abstract

The invention discloses a manganese-rich precursor, a positive electrode material and a preparation method of the positive electrode material, and relates to the technical field of lithium ion batteries. The invention provides the manganese-rich precursor which does not need to add a complexing agent and is provided with the seed crystal layer and the shell layer, the manganese-rich precursor prepared by the method is low in production cost, safe, environment-friendly and high in sphericity degree, and can effectively improve the distribution uniformity of lithium ions and reduce the residual lithium amount in the charging and discharging process of a sintered positive electrode material; meanwhile, the material is not easy to break during rolling and charge-discharge cycles, the structural integrity of the particles is improved, the particle breaking condition is reduced, and the material cycle performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular, to a manganese-rich precursor, a cathode material and a preparation method thereof. Background Art

[0002] With the continuous and vigorous development of the new energy vehicle industry, the performance indicators and cost requirements for lithium ion batteries, the core components of new energy vehicles, have also risen rapidly. Against this background, lithium-rich manganese-based cathode materials have become the direction of the next generation of products due to their high energy density and low cost. Although they have a high energy density, problems such as voltage drop and gas generation during the cycling process of lithium-rich manganese-based cathodes restrict their development and application.

[0003] A cathode precursor refers to a compound or mixture used to prepare a lithium ion battery cathode material, and a lithium-rich manganese-based precursor specifically refers to a precursor compound Ni x Co y Mn z (OH)2, where x + y + z = 1 and z ≥ 50. Currently, the most commonly used method for synthesizing lithium-rich manganese-based precursors (hereinafter referred to as manganese-rich precursors) is the co-precipitation method, which generates a synergistic effect among nickel, cobalt, and manganese through co-precipitation, giving play to the advantages of the three elements. After the polycrystalline precursor undergoes lithium mixing and high-temperature sintering, its structure changes little, indicating that the structure of the cathode material largely inherits the structure of the precursor, which is then reflected in the performance. Therefore, designing and optimizing the precursor structure plays an important role in improving the performance and stability of lithium ion batteries.

[0004] Due to the high manganese content in manganese-rich products, the precursor characteristics are close to those of manganese hydroxide, and it is easy to agglomerate and has poor sphericity during the wet co-precipitation process. In the prior art, the large particles of manganese-rich precursors have poor sphericity and mostly form grape-like particles, with a sphericity < 0.96. The poor consistency and wide diameter distance of the secondary particles of the precursor will not only reduce the uniformity of lithium ion diffusion during the cathode sintering process, but also cause particle cracking and fragmentation during cathode rolling, resulting in poor cycling performance.

[0005] Therefore, there is an urgent need to prepare a manganese-rich precursor material with high sphericity to improve the electrochemical performance of the cathode material.

[0006] In view of this, the present invention is specifically proposed. Summary of the Invention

[0007] The purpose of the present invention is to provide a manganese-rich precursor, a cathode material and a preparation method thereof, aiming to provide a manganese-rich precursor with good sphericity and high particle size consistency to improve the cycling performance of the cathode material.

[0008] The present invention is realized as follows:

[0009] In a first aspect, the present invention provides a manganese-rich precursor, which includes a seed layer and a shell layer coated on the seed layer;

[0010] The sphericity of the manganese-rich precursor is greater than or equal to 0.96;

[0011] The volume distribution diameter distance K of the manganese-rich precursor particles 90 =(D v90 -D v10 ) / D v50 , 0.3 < K 90 ≤0.8;

[0012] The chemical general formula of the manganese-rich precursor is Ni x Co y Mn z (OH)2, where 0.30 ≤ x < 0.50, 0 ≤ y < 0.10, 0.50 ≤ z < 1.00, and x + y + z = 1.

[0013] In an optional embodiment, the diameter of the seed layer is 1.8 μm - 4.5 μm, and the thickness of the shell layer is 0.8 μm - 5.0 μm;

[0014] Preferably, the specific surface area of the manganese-rich precursor is 20 m 2 / g - 40 m 2 / g, and the tap density is 1.50 g / cm 3 -1.80 g / cm 3 .

[0015] In a second aspect, the present invention provides a preparation method for the manganese-rich precursor in any one of the foregoing embodiments, including:

[0016] Prepare a mixed salt solution according to the chemical general formula of the manganese-rich precursor, and perform a coprecipitation reaction in the presence of a precipitant, successively carrying out a first-stage reaction, a second-stage reaction, and a third-stage reaction;

[0017] The first-stage reaction is carried out under the condition that the first pH value is 11.0 - 12.2 to complete the nucleation stage;

[0018] The second-stage reaction is carried out under the condition that the second pH value is 8.0 - 10.0 to complete the growth of the seed crystals and obtain manganese-rich precursor seed crystals;

[0019] The process of the third-stage reaction includes: mixing water and manganese-rich precursor seed crystals to obtain a second bottom liquid, and adding a mixed metal salt solution and a precipitant to the second bottom liquid for reaction.

[0020] In an optional embodiment, it includes:

[0021] Mix water and a precipitant to prepare a first bottom solution with a first pH value; add a mixed metal salt solution of nickel manganese or nickel cobalt manganese and a precipitant to the first bottom solution for a first-stage reaction, and maintain the flow rate of the mixed metal salt solution and the reaction pH value unchanged during the reaction;

[0022] When the particle size D v50 is 0.7 μm - 1.1 μm, carry out a second-stage reaction, gradually reduce the reaction pH value to a second pH value, gradually increase the flow rate of the mixed metal salt solution to the metal solution flow rate in the second stage, and stop the reaction when the particle size reaches D1 to obtain a manganese-rich precursor seed; when the metal solution flow rate in the second stage is reached, the volume of the mixed metal salt solution introduced in 1 h is 3% - 10% of the effective volume of the reaction kettle;

[0023] Mix water and the manganese-rich precursor seed to obtain a second bottom solution, add the mixed metal salt solution and a precipitant to the second bottom solution for a third-stage reaction, and maintain the third pH value unchanged; when the third-stage reaction starts to t1, reach the fourth stage, where t1 is 1 h - 4 h; during the fourth-stage reaction, gradually increase the flow rate of the mixed metal salt solution and maintain the third pH value unchanged, and stop the reaction when the particle size reaches D2 to obtain a manganese-rich precursor; among them, the third pH value is 8.0 - 10.0;

[0024] Preferably, during the first to fourth stage reactions, continuously introduce a mixed gas of an inert gas and air to make the oxygen content reach 0.5% - 5.0%; among them, the inert gas is selected from at least one of nitrogen, argon, and helium.

[0025] In an alternative embodiment, when the particle size reaches D1, the volume distribution average particle size D of the obtained manganese-rich precursor seed v50 is 1.8 μm - 4.5 μm, preferably 2.0 μm - 4.0 μm;

[0026] Preferably, when the particle size reaches D2, the volume distribution average particle size D of the obtained manganese-rich precursor v50 is 3.6 μm - 14.5 μm, preferably 4.0 μm - 13.0 μm;

[0027] Preferably, the first pH value is 11.5 - 12.0, the second pH value is 8.5 - 9.8, and the third pH value is 8.5 - 9.8;

[0028] Preferably, the ratio of the first bottom solution to the effective volume of the reaction kettle is controlled at 0.6 - 0.8.

[0029] In an alternative embodiment, during the first-stage reaction, control the volume of the mixed metal salt solution introduced in 1 h to be 1.0% - 5.0% of the effective volume of the reaction kettle, preferably 1.5% - 4.0%;

[0030] Preferably, when the metal liquid flow rate reaches the second stage, the volume of the mixed metal salt solution introduced per hour is 4%-9% of the effective volume of the reaction kettle;

[0031] Preferably, during the third stage of the reaction, control the volume of the mixed metal salt solution introduced per hour to be 1.0%-5.0% of the effective volume of the reaction kettle, preferably 1.5%-4.0%;

[0032] Preferably, at the end point of the fourth stage of the reaction, control the volume of the mixed metal salt solution introduced per hour to be 7.0%-15.0% of the effective volume of the reaction kettle, preferably 8.0%-14.0%.

[0033] In an alternative embodiment, during the first stage of the reaction, control the rotation speed to be constant, and the rotation speed is 300 rpm - 520 rpm; preferably 380 rpm - 500 rpm;

[0034] During the process from the third stage of the reaction to the fourth stage of the reaction, control the rotation speed to gradually decrease. At the beginning, the rotation speed is 300 rpm - 520 rpm, preferably 380 rpm - 500 rpm; at the end, the rotation speed is 100 rpm - 410 rpm, preferably 120 rpm - 400 rpm.

[0035] In an alternative embodiment, the concentration of the mixed metal salt solution is 115 g / L - 140 g / L, preferably 120 g / L - 135 g / L;

[0036] Preferably, the precipitant is an alkali solution, and the alkali solution is selected from at least one of sodium hydroxide solution, sodium carbonate solution, and sodium bicarbonate solution;

[0037] Preferably, in terms of mass fraction, the concentration of the precipitant is 15% - 40%, more preferably 20% - 35%;

[0038] Preferably, during the reaction process of each stage, control the reaction temperature to be 35°C - 75°C, preferably 45°C - 70°C.

[0039] In a third aspect, the present invention provides a method for preparing a cathode material, including mixing and sintering any one of the manganese-rich precursors in the foregoing embodiments or the manganese-rich precursor prepared by any one of the preparation methods in the foregoing embodiments with a lithium salt.

[0040] In a fourth aspect, the present invention provides a cathode material prepared by the preparation method of the foregoing embodiment.

[0041] The present invention has the following beneficial effects: The present invention provides a manganese-rich precursor with a seed layer and a shell layer. The manganese-rich precursor has a high sphericity. During the charge and discharge process of the sintered cathode material, it can effectively improve the uniformity of lithium-ion distribution, reduce the residual lithium content, and is not easily broken during rolling and charge and discharge cycles, improving the integrity of the particle structure, reducing the particle breakage situation, and improving the cycle performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0043] Figure 1 SEM and CP diagrams for Example 1; (a) is the SEM diagram, and (b) is the CP diagram;

[0044] Figure 2 SEM and CP diagrams for Example 2; (a) is the SEM diagram, and (b) is the CP diagram;

[0045] Figure 3 SEM and CP diagrams for Example 3; (a) is the SEM diagram, and (b) is the CP diagram;

[0046] Figure 4 SEM and CP diagrams for Comparative Example 1; (a) is the SEM diagram, and (b) is the CP diagram;

[0047] Figure 5 SEM and CP diagrams for Comparative Example 2; (a) is the SEM diagram, and (b) is the CP diagram;

[0048] Figure 6 SEM and CP diagrams for Comparative Example 3; (a) is the SEM diagram, and (b) is the CP diagram. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0050] The embodiments of the present invention provide a manganese-rich precursor, including a seed layer and a shell layer coated on the seed layer; wherein, the diameter of the seed layer is 1.8 μm - 4.5 μm, and the thickness of the shell layer is 0.8 μm - 5.0 μm. The sizes of the seed layer and the shell layer within the above range are conducive to forming uniform precursor particles.

[0051] Specifically, the diameter of the seed layer of the manganese-rich precursor can be 1.8 μm, 1.9 μm, 2.0 μm, 3.0 μm, 4.0 μm, 4.5 μm, etc.; the thickness of the shell layer can be 0.8 μm, 1.5 μm, 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, etc.

[0052] Furthermore, the sphericity of the manganese-rich precursor is greater than or equal to 0.96 and less than 1, with a relatively high sphericity; the volume distribution diameter distance K of the manganese-rich precursor particles 90 =(D v90 -D v10 ) / D v50 , 0.3 < K 90 ≤0.8. The value of K of the manganese-rich precursor provided by the embodiments of the present invention 90 is relatively low, with a narrow particle size distribution, effectively improving the cycle performance of the cathode material.

[0053] Specifically, the sphericity of the manganese-rich precursor can be 0.96, 0.965, 0.97, 0.975, 0.98, etc.; the specific value of the volume distribution diameter distance K of the manganese-rich precursor particles 90 can be 0.80, 0.70, 0.60, 0.50, 0.40, 0.30, etc.

[0054] In some embodiments, the chemical general formula of the manganese-rich precursor is Ni x Co y Mn z (OH)2, where 0.30 ≤ x < 0.50, 0 ≤ y < 0.10, 0.50 ≤ z < 1.00, and x + y + z = 1. It is appropriate that the molar ratio of each metal element is within the above range, and a lithium-rich manganese-based cathode material with excellent electrochemical performance can be further prepared. Specifically, the value of x can be 0.30, 0.40, 0.50, etc., the value of y can be 0.00, 0.03, 0.05, 0.08, 0.09, etc., and the value of z can be 0.50, 0.60, 0.70, 0.80, 0.90, etc.

[0055] In some embodiments, the specific surface area of the manganese-rich precursor is 20 m 2 / g - 40 m 2 / g, and the tap density is 1.50 g / cm 3 -1.80 g / cm 3 . When used in a battery, a high specific surface area and rich pores are beneficial to the release of the capacity of the manganese-rich cathode, and a high sphericity is beneficial to improving the cycle performance. Specifically, the specific surface area of the manganese-rich precursor can be 20 m 2 / g, 25 m 2 / g, 30 m 2 / g, 35 m 2 / g, 40 m 2 / g, etc.; The tap density can be 1.50 g / cm 3 、1.55 g / cm 3 、1.65 g / cm 3 、1.75 g / cm 3 、1.80 g / cm 3 etc. The interior of the manganese-rich precursor particles has a loose structure. During the sintering process to the cathode and the charge and discharge process of the cathode, the loose structure is conducive to the infiltration of the electrolyte, improving the lithium-ion transmission rate and the capacity performance of the material.

[0056] The influence of the precursor particle consistency on the performance of the cathode material is complex and interrelated. When designing and preparing the precursor material, it is necessary to balance these factors and optimize according to specific application requirements to achieve a high-performance high-nickel cathode battery material. Aiming at the problems of the manganese-rich precursor particles prepared by coprecipitation at present, such as more agglomeration, low sphericity, and poor secondary particle consistency, a method for reducing agglomeration and improving the secondary particle consistency is provided to optimize the precursor structure and improve the performance of the cathode material.

[0057] The embodiment of the present invention also provides a preparation method of a manganese-rich precursor, which can effectively control and improve the secondary particle consistency and have a high sphericity, effectively enhancing the cycle performance of the cathode material. The steps are as follows:

[0058] S1. Prepare a mixed metal salt solution, a precipitant, and a first bottom liquid

[0059] Mix the metal salt and a solvent (such as water) to prepare a mixed metal salt solution of nickel manganese or nickel cobalt manganese. The types of metal elements and the molar ratio of each metal element are adjusted according to the chemical formula of the precursor. The metal salt used is selected from at least one of sulfates, nitrates, and chlorides, and the metal salt can be any one or several of the above.

[0060] Furthermore, the concentration of the mixed metal salt solution is 115 g / L - 140 g / L, preferably 120 g / L - 135 g / L. The concentration of the mixed metal salt solution refers to the total concentration of the metal salt. Within this range, it is convenient for uniform deposition and improves the uniformity of the particles. Specifically, the concentration of the mixed metal salt solution can be 115 g / L, 120 g / L, 125 g / L, 130 g / L, 135 g / L, 140 g / L, etc.

[0061] In some embodiments, the precipitant is an alkali solution for regulating the pH value of the reaction. The alkali solution is selected from at least one of sodium hydroxide solution, sodium carbonate solution, and sodium bicarbonate solution, and the alkali solution can be any one or several of the above.

[0062] Furthermore, the mass fraction of the precipitant is 15%-40%, preferably 20%-35%. Within this range, the pH value of the reaction can be more accurately regulated. Specifically, the mass fraction of the precipitant can be 15%, 20%, 25%, 30%, 35%, 40%, etc.

[0063] Mix water and the precipitant to prepare a first bottom liquid with a first pH value; wherein, the first pH value is 11.0-12.2; preferably 11.5-12.0, so as to meet the pH value requirement for the first-stage reaction. Specifically, the first pH value can be 11.0, 11.3, 11.5, 11.8, 12.0, 12.1, 12.2, etc. The method provided by the embodiments of the present invention does not require ammonia water, reducing production costs and at the same time reducing the safety and environmental risks.

[0064] S2. First-stage reaction

[0065] Add the mixed metal salt solution of nickel and manganese or nickel, cobalt and manganese and the precipitant to the first bottom liquid for the first-stage reaction. During the reaction, keep the flow rate of the mixed metal salt solution and the reaction pH value unchanged, and the reaction pH value is maintained at the first pH value. The ratio of the effective volume of the first bottom liquid to the reaction kettle is controlled at 0.6-0.8, such as 0.6, 0.7, 0.8, etc.

[0066] In some embodiments, during the first-stage reaction, control the volume of the mixed metal salt solution introduced per hour to be 1.0%-5.0% of the effective volume of the reaction kettle, preferably 1.5%-4.0%. By regulating the introduction flow rate during the seed crystal formation process, the reaction rate can be better controlled, making the formed seed crystal particles more uniform. Specifically, control the volume of the mixed metal salt solution introduced per hour to be 1.0%, 1.5%, 2.0%, 3.0%, 4.0%, 5.0%, etc. of the effective volume of the reaction kettle. The effective volume of the reaction kettle is a design parameter of the reaction kettle.

[0067] Furthermore, during the first-stage reaction, keep the rotation speed unchanged, and the rotation speed is 300 rpm-520 rpm; preferably 380 rpm-500 rpm. Within this rotation speed range, the uniformity of the material distribution in the reaction kettle is higher, making the formed seed crystal particles more uniform. Specifically, during the first-stage reaction, the rotation speed is constant, for example, it can be 300 rpm, 350 rpm, 380 rpm, 400 rpm, 450 rpm, 500 rpm, 520 rpm, etc.

[0068] Further, during the first-stage reaction, the reaction temperature is controlled to be 35°C - 75°C, preferably 45°C - 70°C, such as 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, etc. During the first-stage reaction, the gas introduced is not limited, such as at least one of air, nitrogen, and argon.

[0069] S3. Second-stage reaction

[0070] When the particle size D v50 is 0.7 μm - 1.1 μm (such as 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, etc.), the second-stage reaction is carried out. The reaction pH value is gradually decreased to reach the second pH value, and the flow rate of the mixed metal salt solution is gradually increased to the second-stage metal liquid flow rate. When the particle size reaches D1, the reaction is stopped to obtain the manganese-rich precursor seed crystal. In the later stage of the preparation of the manganese-rich precursor seed crystal, decreasing the pH value while increasing the flow rate of the mixed metal salt solution can improve the seed crystal production capacity, optimize the internal pores of the seed crystal, and maintain the loose structure of the manganese-rich product from the inside to the outside.

[0071] Further, the second pH value is 8.0 - 10.0, preferably 8.5 - 9.5. The pH value is decreased by 1.5 - 3.5 from the first pH value to reach the second pH value, and the preparation of the manganese-rich precursor seed crystal is completed under weak alkaline conditions. Specifically, the second pH value can be 8.0, 8.5, 9.0, 9.5, 10.0, etc. When the second-stage metal liquid flow rate is reached, the volume of the mixed metal salt solution introduced in 1 h is 3% - 10% of the effective volume of the reaction kettle, preferably 4% - 9%, such as 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., and the flow rate is increased to meet the needs of the rapid particle growth stage.

[0072] When the particle size reaches D1, the volume distribution average particle size D of the obtained manganese-rich precursor seed crystal v50 is 1.8 μm - 4.5 μm, preferably 2.0 μm - 4.0 μm. The size of the manganese-rich precursor seed crystal is preferably within the above range to form precursor particles with higher uniformity. Specifically, the volume distribution average particle size D v50 (D1) of the manganese-rich precursor seed crystal can be 1.8 μm, 2.0 μm, 2.5 μm, 3.0 μm, 3.5 μm, 4.0 μm, 4.5 μm, etc.

[0073] Further, during the second-stage reaction, the reaction temperature is controlled to be 35°C - 75°C, preferably 45°C - 70°C, such as 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, etc. During the second-stage reaction, the gas introduced is not limited, such as at least one of air, nitrogen, and argon.

[0074] Further, during the second-stage reaction, the rotation speed is controlled to be constant, and the rotation speed is 300 rpm - 520 rpm; preferably 380 rpm - 500 rpm. Within this rotation speed range, the uniformity of the material distribution in the reaction kettle is higher, and the formed seed particles are more uniform. Specifically, during the first-stage reaction, the rotation speed is constant, for example, it can be 300 rpm, 350 rpm, 380 rpm, 400 rpm, 450 rpm, 500 rpm, 520 rpm, etc.

[0075] S4. Third-stage reaction and fourth-stage reaction

[0076] Mix water and the manganese-rich precursor seeds to obtain a second bottom liquid. Add the mixed metal salt solution and the precipitant to the second bottom liquid for the third-stage reaction, and maintain the third pH value unchanged; when the third-stage reaction starts and reaches t1, it enters the fourth stage, where t1 is 1 h - 4 h; during the fourth-stage reaction, gradually increase the flow rate of the mixed metal salt solution and maintain the third pH value unchanged. Stop the reaction when the particle size reaches D2 to obtain the manganese-rich precursor. By keeping the third pH value unchanged and gradually increasing the flow rate of the mixed metal salt solution, the shell layer grows rapidly and uniformly.

[0077] Among them, the third pH value is 8.0 - 10.0, preferably 8.5 - 9.5. The pH value control during the growth of the shell layer is basically the same as that at the end of the seed growth stage, which can better control the growth rate of the shell layer and form uniform precursor particles. When the particle size reaches D2, the volume distribution average particle size D of the obtained manganese-rich precursor v50 is 3.6 μm - 14.5 μm, preferably 4.0 μm - 13.0 μm. By regulating the final size of the precursor product, the thickness of the shell layer growth is controlled, so that the thickness of the seed layer and the shell layer is more matched, and the electrochemical performance of the prepared cathode material is improved.

[0078] Specifically, the third pH value can be 8.0, 8.5, 9.0, 9.5, 10.0, etc. The volume distribution average particle size D of the manganese-rich precursor v50 (D2) can be 3.6 μm, 4.0 μm, 4.5 μm, 5.0 μm, 5.5 μm, 6.0 μm, 6.5 μm, 7.0 μm, 7.5 μm, 8.0 μm, 9.0 μm, 10.0 μm, 11.0 μm, 12.0 μm, 13.0 μm, 14.0 μm, 14.5 μm, etc.

[0079] In some embodiments, during the third-stage reaction, the mixed metal salt solution is introduced at a uniform speed, and the volume of the mixed metal salt solution introduced in 1 h is controlled to be 1.0%-5.0% of the effective volume of the reaction kettle, preferably 1.5%-4.0%, such as 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, etc. The end point of the fourth-stage reaction controls the volume of the mixed metal salt solution introduced in 1 h to be 7.0%-15.0% of the effective volume of the reaction kettle, preferably 8.0%-14.0%, such as 7.0%, 8.0%, 9.0%, 10.0%, 11.0%, 12.0%, 13.0%, 14.0%, 15.0%, etc.

[0080] Furthermore, during the process from the third-stage reaction to the fourth-stage reaction, the rotation speed is controlled to gradually decrease. At the beginning, the rotation speed is 300 rpm - 520 rpm, preferably 380 rpm - 500 rpm. The rotation speed at the beginning can be 300 rpm, 330 rpm, 350 rpm, 380 rpm, 400 rpm, 450 rpm, 500 rpm, 520 rpm, etc. The rotation speed at the end is 100 rpm - 410 rpm, preferably 120 rpm - 400 rpm. The rotation speed at the end can be 100 rpm, 120 rpm, 200 rpm, 300 rpm, 350 rpm, 400 rpm, etc. The stirring rotation speed decreases slowly and continuously with time, avoiding the cracking and breaking of particles caused by high rotation speed after particle growth, which is beneficial to the synthesis of high-sphericity manganese-rich precursors.

[0081] Furthermore, during the first to fourth-stage reactions, a mixed gas of inert gas and air is continuously introduced to make the oxygen content reach 0.5% - 5.0%, such as 0.5%, 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, etc.; wherein, the inert gas is selected from at least one of nitrogen, argon, and helium, and the inert gas can be any one or several of the above.

[0082] Furthermore, during the third-stage reaction and the fourth-stage reaction, the reaction temperature is controlled to be 35°C - 75°C, preferably 45°C - 70°C, such as 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, etc. During the second-stage reaction and the fourth-stage reaction, the gas introduced is not limited, such as at least one of air, nitrogen, and argon.

[0083] The embodiment of the present invention proposes a technical solution of seed + shell growth. Through inheritance growth, the surface active sites of particles are reduced, the growth time of single particles is extended, and the particles grow fully in the wet chemical co-precipitation system, and finally a high-sphericity manganese-rich precursor is prepared, solving the technical problems of high agglomeration degree and poor sphericity of the manganese-rich precursor.

[0084] An embodiment of the present invention also provides a method for preparing a cathode material, which includes mixing and sintering the manganese-rich precursor provided by the embodiment of the present invention with a lithium salt to obtain a lithium-rich manganese-based cathode material. By optimizing the structure of the precursor, the electrochemical performance of the cathode material is improved.

[0085] An embodiment of the present invention also provides a cathode material prepared by the above preparation method, which has good cycling performance.

[0086] The features and properties of the present invention will be further described in detail below in conjunction with embodiments.

[0087] Example 1

[0088] This embodiment provides a method for preparing a manganese-rich precursor, and the steps are as follows:

[0089] (1) Prepare a mixed metal salt solution and a bottom solution

[0090] Mixed metal salt solution: Mix and dissolve nickel sulfate, cobalt sulfate, manganese sulfate and water, and adjust the molar ratio of nickel, cobalt and manganese to 35:0:65 to make the concentration of the prepared mixed metal salt solution 132 g / L.

[0091] Prepare an aqueous sodium hydroxide solution with a mass fraction of 24% as a precipitating agent.

[0092] Add water and the precipitating agent into a reaction kettle with an effective volume of 450 L, control the reaction temperature to reach 60 °C, and obtain a first bottom solution (volume: 350 L) with a first pH value of 12.00 for standby.

[0093] (2) First-stage reaction

[0094] Add the mixed metal salt solution and the precipitating agent prepared in step (1) into the first bottom solution of the reaction kettle, continuously introduce a mixed gas into the reaction kettle, with an oxygen content of 2.9%, keep the volume of the mixed metal salt solution introduced per hour as 2.3% of the effective volume of the reaction kettle, and keep the pH value of the reaction solution in the reaction kettle at 12.10. During the reaction process, keep the reaction temperature at 60 °C and the stirring speed at 420 rpm.

[0095] (3) Second-stage reaction

[0096] When the particle size D in the reaction kettle is detected v50When it is 0.9 μm (reaction time is about 1.0 h), the second-stage reaction is carried out, and the pH value of the system is slowly decreased (the pH value is decreased by 3.0 every 30 min) to reach the second pH value of 8.9. At the same time, the flow rate of the mixed metal salt solution is slowly increased (the flow rate is increased by 32% every 60 min) to the metal liquid flow rate in the second stage. When the metal liquid flow rate in the second stage is reached, the volume of the mixed metal salt solution introduced per hour is 5.6% of the effective volume of the reaction kettle. During the second-stage reaction, a mixed gas is continuously introduced into the reaction kettle, the oxygen content is 2.9%, the reaction temperature is 60 °C, and the stirring speed is 420 rpm.

[0097] When it is detected that the particle size in the reaction kettle reaches D1 (i.e., particle D v50 is 3.7 μm), stop the machine to prepare the manganese-rich precursor seed crystal.

[0098] (4) The third-stage reaction and the fourth-stage reaction

[0099] Add pure water as the bottom liquid into the second reaction kettle (effective volume is 450 L), and add the seed crystal material obtained in step (3). The mass ratio of pure water to the dry seed crystal material is 27:1 to obtain the second bottom liquid.

[0100] Introduce the nickel-cobalt-manganese mixed metal salt solution and the precipitant prepared in step (1) into the second bottom liquid, and continuously introduce a mixed gas into the reaction kettle. The oxygen content is 4.0%. During the third-stage reaction, the third pH value of 9.0 is maintained unchanged, and the flow rate of the mixed metal salt solution is maintained unchanged. When the reaction starts to t1 = 2 h, the fourth stage is reached; when the fourth-stage reaction is reached, the flow rate of the mixed metal salt solution is slowly increased (the flow rate is increased by 250% every 360 min), and the third pH value is maintained unchanged. The reaction stops when the particle size reaches D2. The volume distribution average particle size D v50 (D2) is 11.25.

[0101] During the third-stage reaction, the flow rate of the mixed metal salt solution introduced per hour is maintained at 3.1% of the effective volume of the reaction kettle, and the flow rate of the mixed metal salt solution at the end point of the fourth-stage reaction is 7.8% of the effective volume of the reaction kettle. During the process from the third-stage reaction to the fourth-stage reaction, the rotation speed is gradually decreased. The rotation speed at the start of the third-stage reaction is 400 rpm, and the rotation speed at the end of the fourth-stage reaction is 140 rpm. During the process from the third-stage reaction to the fourth-stage reaction, the reaction temperature is maintained at 60 °C.

[0102] This example also provides a preparation method of a lithium-ion battery cathode material, and the steps refer to Example 1.

[0103] Example 2

[0104] This example provides a preparation method of a manganese-rich precursor, and the steps are as follows:

[0105] (1) Prepare a mixed metal salt solution and a bottom solution

[0106] Mixed metal salt solution: Dissolve nickel sulfate, cobalt sulfate, manganese sulfate and water, and adjust the molar ratio of nickel, cobalt and manganese to 30:1:69 to make the concentration of the prepared mixed metal salt solution 133 g / L.

[0107] Prepare an aqueous sodium hydroxide solution with a mass fraction of 24% as a precipitant.

[0108] Add water and the precipitant to a reactor with an effective volume of 450 L, control the reaction temperature to reach 60 °C, and obtain a first bottom solution (volume: 340 L) with a first pH value of 11.90 for standby.

[0109] (2) First-stage reaction

[0110] Add the mixed metal salt solution and the precipitant prepared in step (1) to the first bottom solution in the reactor, continuously introduce a mixed gas into the reactor, with an oxygen content of 4.0%, keep the volume of the mixed metal salt solution introduced per hour at 2.0% of the effective volume of the reactor, and keep the pH value of the reaction solution in the reactor at 11.90. During the reaction process, keep the reaction temperature at 60 °C and the stirring speed at 465 rpm.

[0111] (3) Second-stage reaction

[0112] When the particle size D in the reactor is detected v50 At 0.80 μm (reaction time is about 5 h), carry out the second-stage reaction, slowly reduce the pH value of the system (the pH value decreases by 3.2 every 60 min) to reach the second pH value of 8.8, and at the same time slowly increase the flow rate of the mixed metal salt solution (the flow rate increases by 90% every 120 min) to the second-stage metal liquid flow rate. When reaching the second-stage metal liquid flow rate, the volume of the mixed metal salt solution introduced per hour is 6% of the effective volume of the reactor. During the second-stage reaction process, continuously introduce a mixed gas into the reactor, with an oxygen content of 4.0%, the reaction temperature is 60 °C, and the stirring speed is 465 rpm.

[0113] When the particle size in the reactor is detected to reach D1 (i.e., particle D v50 At 2.0 μm), stop the machine to prepare a manganese-rich precursor seed crystal.

[0114] (4) Third-stage reaction and fourth-stage reaction

[0115] Add pure water as the bottom solution to a second reactor (effective volume: 450 L), add the seed crystal material obtained in step (3), and the mass ratio of pure water to the dry seed crystal material is 4:1 to obtain a second bottom solution.

[0116] The nickel-cobalt-manganese mixed metal salt solution and the precipitant prepared in step (1) are introduced into the second bottom liquid, and a mixed gas is continuously introduced into the reaction kettle. The oxygen content is 4.0%. During the third-stage reaction, the third pH value of 8.8 is maintained unchanged, and the flow rate of the mixed metal salt solution is maintained unchanged. When the reaction starts until t1 = 4 h, the fourth stage is reached; when the fourth-stage reaction is reached, the flow rate of the mixed metal salt solution is slowly increased (the flow rate is increased by 300% every 360 min), and the third pH value is maintained unchanged. The reaction is stopped when the particle size reaches D2. The volume distribution average particle size D v50 (D2) is 4.0 μm.

[0117] During the third-stage reaction, the flow rate of the mixed metal salt solution introduced per hour is maintained at 3.0% of the effective volume of the reaction kettle, and the flow rate of the mixed metal salt solution at the end of the fourth-stage reaction is 9.0% of the effective volume of the reaction kettle. During the process from the third-stage reaction to the fourth-stage reaction, the rotation speed is gradually decreased. The rotation speed at the start of the third-stage reaction is 465 rpm, and the rotation speed at the end of the fourth-stage reaction is 400 rpm. During the process from the third-stage reaction to the fourth-stage reaction, the reaction temperature is maintained at 60 °C.

[0118] This example also provides a method for preparing a cathode material for a lithium-ion battery, and the steps are as follows: The manganese-rich precursor prepared in this example is mixed and sintered with lithium hydroxide, and the molar ratio of the total amount of nickel, cobalt, and manganese to lithium is controlled to be 1:1.2, and the temperature is raised to 820 °C at a heating rate of 5 °C / min and held for 5 h.

[0119] Example 3

[0120] This example provides a method for preparing a manganese-rich precursor, and the steps are as follows:

[0121] (1) Prepare a mixed metal salt solution and a bottom liquid

[0122] Mixed metal salt solution: Nickel sulfate, cobalt sulfate, manganese sulfate and water are mixed and dissolved, and the molar ratio of nickel, cobalt and manganese is adjusted to 45:2:53, so that the concentration of the prepared mixed metal salt solution is 130 g / L.

[0123] Prepare an aqueous sodium hydroxide solution with a mass fraction of 24% as a precipitant.

[0124] Water and a precipitant are added to a reaction kettle with an effective volume of 450 L, and the reaction temperature is controlled to reach 60 °C to obtain a first bottom liquid (volume: 330 L) with a first pH value of 12.05 for standby.

[0125] (2) First-stage reaction

[0126] Add the mixed metal salt solution and the precipitant configured in step (1) to the first bottom liquid in the reaction kettle, continuously introduce a mixed gas into the reaction kettle with an oxygen content of 2.5%, keep the volume of the mixed metal salt solution introduced per hour to be 2.7% of the effective volume of the reaction kettle, and keep the pH value of the reaction liquid in the reaction kettle at 12.05. During the reaction process, keep the reaction temperature at 60 °C and the stirring speed at 420 rpm.

[0127] (3) Second-stage reaction

[0128] When the particle size D in the reaction kettle is detected v50 When it is 0.75 μm (reaction time is about 2.0 h), carry out the second-stage reaction. Slowly reduce (the pH value decreases by 2.5 every 40 min) the pH value of the system to the second pH value of 9.5, and slowly increase (the flow rate increases by 300% every 360 min) the flow rate of the mixed metal salt solution to the second-stage metal liquid flow rate. When reaching the second-stage metal liquid flow rate, the volume of the mixed metal salt solution introduced per hour is 8.0% of the effective volume of the reaction kettle. During the second-stage reaction process, continuously introduce a mixed gas into the reaction kettle with an oxygen content of 2.5%, the reaction temperature is 60 °C, and the stirring speed is 420 rpm.

[0129] When the particle size in the reaction kettle is detected to reach D1 (i.e., particle D v50 is 4.5 μm), stop the machine to obtain a manganese-rich precursor seed crystal.

[0130] (4) Third-stage reaction and fourth-stage reaction

[0131] Add pure water as the bottom liquid to the second reaction kettle (effective volume is 450 L), add the seed crystal material obtained in step (3), and the mass ratio of pure water to the dry seed crystal material is 23:1 to obtain the second bottom liquid.

[0132] Introduce the nickel-cobalt-manganese mixed metal salt solution and the precipitant prepared in step (1) into the second bottom liquid, continuously introduce a mixed gas into the reaction kettle with an oxygen content of 2.0%. During the third-stage reaction, keep the third pH value of 9.5 unchanged and keep the flow rate of the mixed metal salt solution unchanged. When starting the reaction to t1 = 3 h, reach the fourth stage; when reaching the fourth-stage reaction, slowly increase (the flow rate increases by 387% every 360 min) the flow rate of the mixed metal salt solution and keep the third pH value unchanged. Stop the reaction when the particle size reaches D2. The volume distribution average particle size D v50 (D2) of the manganese-rich precursor is 12.50.

[0133] During the third-stage reaction process, maintain the flow rate of the mixed metal salt solution introduced per hour at 2.3% of the effective volume of the reaction kettle. The flow rate of the mixed metal salt solution at the end point of the fourth-stage reaction is 8.9% of the effective volume of the reaction kettle. During the process from the third-stage reaction to the fourth-stage reaction, control the rotational speed to gradually decrease. The rotational speed at the start of the third-stage reaction is 380 rpm, and the rotational speed at the end of the fourth-stage reaction is 120 rpm. During the process from the third-stage reaction to the fourth-stage reaction, maintain the reaction temperature at 55 °C.

[0134] This embodiment also provides a method for preparing a cathode material for a lithium-ion battery, and the steps refer to Embodiment 1.

[0135] Comparative Example 1

[0136] This comparative example provides a method for preparing an existing manganese-rich precursor, and the steps are as follows:

[0137] (1) Prepare a mixed metal salt solution and a bottom solution

[0138] The steps refer to Embodiment 1.

[0139] (2) Coprecipitation reaction: the first-stage reaction

[0140] Add the mixed metal salt solution and the precipitant prepared in step (1) to the first bottom solution in the reaction kettle. Continuously introduce nitrogen into the reaction kettle, and maintain the volume of the mixed metal salt solution introduced per hour at 2.0% of the effective volume of the reaction kettle. Maintain the pH value of the reaction liquid in the reaction kettle at 11.90. During the reaction process, maintain the reaction temperature at 60 °C and the stirring rotational speed at 460 rpm.

[0141] (3) The second-stage reaction

[0142] When the particle size D in the reaction kettle is detected v50 is 1.2 μm (the reaction time is about 0.5 h), carry out the second-stage reaction. Slowly decrease (the pH value decreases by 3.0 every 30 min) the pH value of the system to the second pH value of 8.9, and at the same time slowly increase (the flow rate increases by 100% every 60 min) the flow rate of the mixed metal salt solution to the second-stage metal liquid flow rate. When the second-stage metal liquid flow rate is reached, the volume of the mixed metal salt solution introduced per hour is 8.0% of the effective volume of the reaction kettle. During the second-stage reaction process, continuously introduce a mixed gas into the reaction kettle, and the oxygen content is 4.0%.

[0143] When the particle size in the reaction kettle is detected to reach D1 (i.e., particle D v50 is 4.0 μm), stop the machine to obtain the manganese-rich precursor.

[0144] During the second-stage reaction, the rotation speed is gradually decreased. The rotation speed at the start of the second-stage reaction is 460 rpm, and the rotation speed at the end of the second-stage reaction is 430 rpm. During the process from the first-stage reaction to the second-stage reaction, the reaction temperature is maintained at 60 °C.

[0145] This embodiment also provides a method for preparing a cathode material for a lithium-ion battery. The steps refer to Embodiment 1.

[0146] Comparative Example 2

[0147] (1) Prepare a mixed metal salt solution and a bottom solution

[0148] The steps refer to Embodiment 2.

[0149] (2) Coprecipitation reaction: the first-stage reaction

[0150] Add the mixed metal salt solution and the precipitant prepared in step (1) to the first bottom solution in the reaction kettle. Continuously introduce nitrogen into the reaction kettle, and keep the volume of the mixed metal salt solution introduced per hour to be 3.0% of the effective volume of the reaction kettle. Keep the pH value of the reaction solution in the reaction kettle at 11.65. During the reaction process, keep the reaction temperature at 65 °C and the stirring rotation speed at 400 rpm.

[0151] (3) The second-stage reaction

[0152] When the particle size D in the reaction kettle is detected v50 When it is 1.5 μm (the reaction time is about 0.3 h), the second-stage reaction is carried out. Slowly decrease (the pH value decreases by 3.0 every 30 min) the pH value of the system to the second pH value of 9.5, and at the same time slowly increase (the flow rate of the mixed metal salt solution increases by 300% every 360 min) the flow rate of the mixed metal salt solution to the second-stage metal liquid flow rate. When the second-stage metal liquid flow rate is reached, the volume of the mixed metal salt solution introduced per hour is 9.0% of the effective volume of the reaction kettle. During the second-stage reaction, continuously introduce a mixed gas into the reaction kettle, and the oxygen content is 1.4%.

[0153] When it is detected that the particle size in the reaction kettle reaches D1 (i.e., the particle D v50 is 10.0 μm), stop the machine to obtain a manganese-rich precursor.

[0154] During the second-stage reaction, control the rotation speed to gradually decrease. The rotation speed at the start of the second-stage reaction is 400 rpm, and the rotation speed at the end of the second-stage reaction is 200 rpm. During the process from the first-stage reaction to the second-stage reaction, keep the reaction temperature at 65 °C.

[0155] This embodiment also provides a method for preparing a cathode material for a lithium-ion battery. The steps refer to Embodiment 1.

[0156] Comparative Example 3

[0157] (1) Prepare a mixed metal salt solution and a bottom solution

[0158] The steps refer to Example 3.

[0159] (2) Coprecipitation reaction: The first-stage reaction

[0160] Add the mixed metal salt solution and the precipitant prepared in step (1) to the first bottom solution in the reaction kettle, continuously introduce nitrogen into the reaction kettle, keep the volume of the mixed metal salt solution introduced per hour to be 3.3% of the effective volume of the reaction kettle, and keep the pH value of the reaction solution in the reaction kettle at 11.65. During the reaction process, keep the reaction temperature at 70 °C and the stirring speed at 420 rpm.

[0161] (3) The second-stage reaction

[0162] When the particle size D in the reaction kettle is detected v50 to be 1.1 μm (the reaction time is about 0.5 h), carry out the second-stage reaction, slowly reduce (the pH value is reduced by 2.85 every 15 min) the pH value of the system to the second pH value of 8.8, and at the same time slowly increase (the flow rate of the mixed metal salt solution is increased by 60% every 60 min) the flow rate of the mixed metal salt solution to the metal solution flow rate in the second stage. When the metal solution flow rate in the second stage is reached, the volume of the mixed metal salt solution introduced per hour is 11.0% of the effective volume of the reaction kettle. During the second-stage reaction, continuously introduce a mixed gas into the reaction kettle, and the oxygen content is 2.0%.

[0163] When it is detected that the particle size in the reaction kettle reaches D1 (i.e., particle D v50 is 12.5 μm), stop the machine to obtain a manganese-rich precursor.

[0164] During the second-stage reaction, control the rotation speed to gradually decrease. The rotation speed at the start of the second-stage reaction is 420 rpm, and the rotation speed at the end of the second-stage reaction is 120 rpm. During the process from the first-stage reaction to the second-stage reaction, keep the reaction temperature at 70 °C.

[0165] This example also provides a preparation method for the positive electrode material of a lithium-ion battery. The steps refer to Example 1.

[0166] Note: No seeds were prepared during the processes of Comparative Examples 1-3.

[0167] Test Example 1

[0168] Test the SEM and CP diagrams of the products obtained in Examples 1-3 and Comparative Examples 1-3 as Figures 1 - 6 shown.

[0169] From Figure 1 and Figure 4It can be seen from the comparison that after using the seed process and segmented growth, the sphericity and consistency of small particles are significantly improved, and the internal pore distribution is more uniform, which is beneficial to the improvement of the cathode performance.

[0170] From Figure 2 、 3 and Figure 5 、 6 It can be seen that when large particles rich in manganese do not use seeds and do not distinguish the growth stages, the sphericity is poor, and as the particles grow, the uneven parts will wear and fall off during the cycle, generating small particles and reducing the material performance.

[0171] It can be seen that by designing the structural configuration of the seed layer + growth layer, by extending the growth time of small particles, reducing the specific surface area and active sites of small particles, the agglomeration of rich-manganese precursors caused by the increase in Mn content is effectively improved, the sphericity and dispersibility are improved, and the electrochemical performance is optimized.

[0172] Test Example 2

[0173] The sphericity, volume distribution diameter distance K 90 , specific surface area, tap density and particle size of the lithium-rich precursors prepared in the test examples and comparative examples were measured, and the results are shown in Table 1.

[0174] Table 1 Performance test results of the lithium-rich precursors prepared in the examples and comparative examples

[0175]

[0176] It can be seen from Table 1 that the lithium-rich precursors prepared in the examples of the present invention have the advantages of good sphericity and high particle size consistency.

[0177] Test Example 3

[0178] The performance of the cathode materials prepared in the test examples and comparative examples was tested, and the results are shown in Table 2.

[0179] Test method: The ternary precursors and Li prepared in Examples 1-3 and Comparative Examples 1-2 were mixed evenly by a mixer at a molar ratio of 1:1.25, the sintering temperature was 830 °C, the high-temperature sintering duration was 12 h, and after cooling to room temperature, they were pulverized and sieved to obtain the lithium-rich manganese-based cathode material.

[0180] The electrochemical performance was tested using a coin cell: The above lithium-rich manganese-based cathode material was mixed with a conductive agent, a binder and other materials to form a slurry, which was coated on an aluminum foil to make a positive electrode sheet, and then assembled into a coin cell in a vacuum glove box. The electrochemical performance was tested using a BlueTEC test system. The 0.1C cycle test was carried out 20 times under the condition of 3.0V - 4.40V.

[0181] Table 2 Performance test results of the lithium-ion battery cathode materials prepared in the examples and comparative examples

[0182]

[0183] As can be seen from Table 2, the cathode materials prepared in the examples of the present invention have more excellent electrochemical performance.

[0184] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A manganese-rich precursor, characterized in that, The manganese-rich precursor includes a seed layer and a shell layer coated on the seed layer; The sphericity of the manganese-rich precursor is greater than or equal to 0.96; Volume distribution diameter distance K of manganese-rich precursor particles 90 =(D v90 -D v10 ) / D v50 , 0.3 < K 90 ≤ 0.8; The chemical general formula of the manganese-rich precursor is Ni x Co y Mn z (OH)2, where 0.30 ≤ x < 0.50, 0 ≤ y < 0.10, 0.50 ≤ z < 1.00, and x + y + z = 1.

2. The manganese-rich precursor according to claim 1, wherein The diameter of the seed layer is 1.8 μm - 4.5 μm, and the thickness of the shell layer is 0.8 μm - 5.00 μm; Preferably, the diameter of the seed layer is 2.0 μm - 4.0 μm, and the thickness of the shell layer is 1.0 μm - 4.5 μm; Preferably, the specific surface area of the manganese-rich precursor is 20 m 2 / g - 40 m 2 / g, and the tapped density is 1.50 g / cm 3 - 1.80 g / cm 3 .

3. A method for preparing the manganese-rich precursor according to any one of claims 1-2, characterized in that, Including: Preparing a mixed salt solution according to the chemical general formula of the manganese-rich precursor, and performing a co-precipitation reaction in the presence of a precipitant, successively performing a first-stage reaction, a second-stage reaction, and a third-stage reaction; The first-stage reaction is carried out under the condition that the first pH value is 11.0 - 12.2 to complete the nucleation stage; The second-stage reaction is carried out under the condition that the second pH value is 8.0 - 10.0 to complete the growth of the seed crystal and obtain a manganese-rich precursor seed crystal; The process of the third-stage reaction includes: mixing water and the manganese-rich precursor seed crystal to obtain a second bottom liquid, and adding a mixed metal salt solution and a precipitant to the second bottom liquid for reaction.

4. The preparation method according to claim 3, characterized in that, Including: Mixing water and a precipitant to prepare a first bottom liquid with the first pH value; Adding a mixed metal salt solution of nickel manganese or nickel cobalt manganese and a precipitant to the first bottom liquid for the first-stage reaction, and maintaining the flow rate of the mixed metal salt solution and the reaction pH value unchanged during the reaction; When the particle size D v50 is 0.7 μm - 1.1 μm, the second-stage reaction is carried out, the reaction pH value is gradually reduced to the second pH value, the flow rate of the mixed metal salt solution is gradually increased to the metal liquid flow rate in the second stage, and the reaction is stopped when the particle size reaches D1 to obtain a manganese-rich precursor seed; when the metal liquid flow rate in the second stage is reached, the volume of the mixed metal salt solution introduced in 1 h is 3% - 10% of the effective volume of the reaction kettle; Mixing water and the manganese-rich precursor seed crystal to obtain a second bottom liquid, adding the mixed metal salt solution and a precipitant to the second bottom liquid for the third-stage reaction, and maintaining the third pH value unchanged; when the reaction starts in the third stage until t1, it reaches the fourth stage, where t1 is 1 h - 4 h; during the fourth-stage reaction, gradually increase the flow rate of the mixed metal salt solution and maintain the third pH value unchanged, and stop the reaction to obtain a manganese-rich precursor when the particle size reaches D2; wherein, the third pH value is 8.0 - 10.

0.

5. The preparation method according to claim 4, characterized in that When the particle size reaches D1, the volume distribution average particle size D of the obtained manganese-rich precursor seed crystal v50 is 1.8 μm - 4.5 μm, preferably 2.0 μm - 4.0 μm; Preferably, when the particle size reaches D2, the volume distribution average particle size D of the obtained manganese-rich precursor v50 is 3.6 μm - 14.5 μm, preferably 4.0 μm - 13.0 μm; Preferably, the first pH value is 11.5 - 12.1, the second pH value is 8.5 - 9.8, and the third pH value is 8.5 - 9.8; Preferably, the volume ratio of the first bottom liquid to the effective volume of the reaction kettle is controlled at 0.6 - 0.8; Preferably, during the first to fourth stage reactions, a mixed gas of an inert gas and air is continuously introduced to make the oxygen content reach 0.5% - 5.0%; wherein, the inert gas is selected from at least one of nitrogen, argon, and helium.

6. The preparation method according to claim 5, characterized in that, During the first-stage reaction, control the volume of the mixed metal salt solution introduced per hour to be 1.0% - 5.0% of the effective volume of the reaction kettle, preferably 1.5% - 4.0%; Preferably, when reaching the metal liquid flow rate in the second stage, the volume of the mixed metal salt solution introduced per hour is 4% - 9% of the effective volume of the reaction kettle; Preferably, during the third-stage reaction, control the volume of the mixed metal salt solution introduced per hour to be 1.0% - 5.0% of the effective volume of the reaction kettle, preferably 1.5% - 4.0%; Preferably, the end point control of the fourth-stage reaction is that the volume of the mixed metal salt solution introduced in 1 h is 7.0%-15.0% of the effective volume of the reaction kettle, preferably 8.0%-14.0%.

7. The preparation method according to claim 4, characterized in that, During the first-stage reaction and the second-stage reaction, the rotation speed is controlled to be constant, and the rotation speed is 300 rpm - 520 rpm; preferably 380 rpm - 500 rpm; During the process from the third-stage reaction to the fourth-stage reaction, the rotation speed is controlled to gradually decrease. The initial rotation speed is 300 rpm - 520 rpm, preferably 380 rpm - 500 rpm; the final rotation speed is 100 rpm - 410 rpm, preferably 120 rpm - 400 rpm.

8. The preparation method according to any one of claims 3-7, characterized in that, The concentration of the mixed metal salt solution is 115 g / L - 140 g / L, preferably 120 g / L - 135 g / L; Preferably, the precipitant is an alkali solution, and the alkali solution is selected from at least one of sodium hydroxide solution, sodium carbonate solution and sodium bicarbonate solution; Preferably, by mass fraction, the concentration of the precipitant is 15% - 40%, more preferably 20% - 35%; During the reaction process of each stage, the reaction temperature is controlled to be 35°C - 75°C, preferably 45°C - 70°C.

9. A method for preparing a cathode material, characterized in that, It includes mixing and sintering the manganese-rich precursor described in any one of claims 1-2 or the manganese-rich precursor prepared by the preparation method described in any one of claims 3-8 with a lithium salt.

10. A cathode material, characterized in that, It is prepared by the preparation method described in claim 9.

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