A manganese-rich cathode material precursor composed of nanosheets, its preparation method, and the cathode material thereof.

Abstract

This invention discloses a manganese-rich cathode material precursor composed of nanosheets, its preparation method, and the cathode material itself, relating to the field of lithium-ion battery materials technology. The preparation method includes adding a mixed metal salt solution, an alkaline solution, and a complexing agent solution to a reaction vessel filled with inert gas at a certain temperature. The reaction vessel contains a small amount of pure water and a complexing agent as a base liquid. The pH value, stirring speed, and reaction time of the reaction system are controlled to form nanosheet-shaped crystal nuclei. The flow rate of the metal salt solution is continuously controlled to reduce the pH value of the reaction system, and the reaction is stopped when the particle size reaches a set value. After aging for a certain period, the slurry is discharged, and solid-liquid separation is performed to obtain a precipitate. The precipitate is washed and dried to obtain the manganese-rich cathode material precursor. Using the method of this invention, primary particles with nanosheet-shaped morphology and secondary particles with good sphericity can be obtained. The preparation method is simple to operate and easy to industrialize.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials technology, and in particular to a manganese-rich precursor composed of spherical or near-spherical secondary particles made up of nano-thin disc-shaped primary particles, its preparation method, and a cathode material. Background Technology

[0002] Lithium-ion batteries, due to their advantages such as high energy density, long cycle life, and environmental friendliness, have been widely used in portable electronic devices, electric vehicles, and energy storage systems. With the increasing demand for energy density in electric vehicles and large-scale energy storage, the development of high-energy-density cathode materials has become a research hotspot. Lithium-rich manganese-based cathode materials (such as xLi₂MnO₃•(1-x)LiMO₂, where M is a transition metal such as Ni, Co, or Mn) are considered one of the core cathode materials for next-generation high-energy-density lithium-ion batteries due to their ultra-high theoretical specific capacity (>250 mAh / g). Lithium-rich manganese-based cathode materials are typically prepared by high-temperature sintering of precursors and lithium sources (such as LiOH or Li₂CO₃). Therefore, the morphology, particle size distribution, primary particle uniformity, and sphericity of the precursor directly determine the electrochemical performance of the final cathode material. In existing technologies, lithium-rich manganese-based precursors are mostly prepared using a co-precipitation method, where the target product is obtained by controlling parameters such as pH, temperature, stirring speed, and metal ion concentration in the reaction system. Existing manganese-rich cathode material precursors suffer from the following problems: First, the primary particles have poor uniformity, are thick lamellar, and the transition metal ions are unevenly distributed within the precursor, leading to the separation of the Li2MnO3 and LiMO2 phases in the cathode material after sintering, resulting in rapid capacity decay during cycling. Second, the morphology is poorly controllable, easily forming severely agglomerated secondary particles, resulting in poor electrolyte wettability and poor rate performance. Third, the reaction parameter window during preparation is narrow, production repeatability is poor, and the process is not streamlined enough, making it difficult to meet the needs of industrial production. For example, the precursor synthesized by Chinese patent publication number CN107482172A has poor sphericity, a nano-flower-like morphology, and requires pre-calcination of the precursor to prepare the cathode material. The submicron-sized particle precursor prepared by Chinese patent publication number CN115385389A has primary particles that are approximately 200 nm thick. Due to the inheritance relationship between the precursor and the cathode material, the thick primary particles are detrimental to the electrochemical performance.

[0003] Therefore, developing lithium-rich manganese-based precursors with uniform particle size and controllable morphology is of great significance for the industrialization of cathode materials. Summary of the Invention

[0004] One of the objectives of this invention is to provide a manganese-rich cathode material precursor composed of nanosheets, which has the advantages of primary particles in the form of thin discs, secondary particles in the form of spherical or near-spherical shapes, and high repeatability.

[0005] The second objective of this invention is to provide a method for preparing a manganese-rich cathode material precursor composed of the nanosheet, which is stable and easy to industrialize.

[0006] The third objective of this invention is to provide a cathode material prepared from a manganese-rich cathode material precursor composed of such nanosheets.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0008] In a first aspect, the present invention provides a manganese-rich cathode material precursor composed of nanosheets, wherein the manganese-rich cathode material precursor is composed of spherical or near-spherical secondary particles formed by primary particles in the form of nanosheets; and has the following characteristics:

[0009] (1) The thickness of the primary particle thin disc is 10-70 nm, the diameter is 200-500 nm, the thickness-to-diameter ratio (thickness / diameter) is 0.05-0.25, and the roundness is 0.65-0.98;

[0010] (2) The particle size D50 of the secondary particles is 4 to 20 μm;

[0011] (3) The specific surface area of ​​the precursor is 10–80 m². 2 / g.

[0012] Preferably, the primary particle wafers of the precursor have the following properties: thickness of 20-50 nm, more preferably 30-40 nm; diameter of 250-400 nm, more preferably 300-350 nm; aspect ratio of 0.06-0.1, more preferably 0.07-0.075; and roundness of 0.85-0.98, more preferably 0.95-0.98.

[0013] Preferably, the particle size D50 of the secondary particles of the precursor is 5~10 μm, more preferably 5~7 μm.

[0014] Preferably, the specific surface area of ​​the precursor is 20~60 m². 2 / g, more preferably 30~45 m 2 / g.

[0015] The chemical formula of the manganese-rich cathode material precursor is Ni. x Mn y Co 1-x-y (OH)2, wherein 0.1≤x≤0.5, 0.5≤y≤0.9, preferably, the range of x is further limited to 0.3~0.5; and the range of y is further limited to 0.5~0.7.

[0016] Secondly, the present invention provides a method for preparing a manganese-rich cathode material precursor composed of the above-mentioned nanosheets, comprising the following steps:

[0017] (1) Dissolve nickel salt, cobalt salt and manganese salt in deionized water to obtain a mixed metal salt solution; dissolve alkali and complexing agent in deionized water to obtain alkali solution and complexing agent solution respectively;

[0018] (2) Add the bottom liquid to the reactor, heat it up and then introduce nitrogen to remove oxygen; pump the mixed metal salt solution, alkaline solution and complexing agent solution from step (1) into the reactor continuously through a peristaltic pump, control the pH value and stirring speed of the reaction system, and form nano-thin disc-shaped primary particle nuclei.

[0019] (3) Keep the flow rate of the mixed metal salt solution constant, reduce the flow rate of the alkali solution to make the pH decrease linearly, and increase the stirring speed. Stop the reaction when the particle size reaches the set value; release the slurry after aging.

[0020] (4) The slurry from step (3) is subjected to solid-liquid separation to obtain a precipitate; the precipitate is washed with deionized water and then dried to obtain a manganese-rich cathode material precursor composed of nano-thin discs.

[0021] Step (1):

[0022] Preparation of metal salt solution: Dissolve nickel salt, cobalt salt, and manganese salt in deionized water to obtain a mixed metal salt solution with a total metal ion concentration of 0.5–3 mol / L. The molar ratio of nickel, manganese, and cobalt is x:y:(1-xy), where 0.1≤x≤0.5, 0.5≤y≤0.9, and the range of x is further limited to 0.3–0.5; the range of y is further limited to 0.5–0.7.

[0023] In step (1), the nickel salt is one or more of nickel sulfate, nickel nitrate, or nickel chloride; the manganese salt is one or more of manganese sulfate, manganese nitrate, or manganese chloride; and the cobalt salt is one or more of cobalt sulfate, cobalt nitrate, or cobalt chloride.

[0024] Preparation of alkaline solution and complexing agent solution: Dissolve the alkali and complexing agent separately in deionized water to obtain an alkaline solution with an alkaline concentration of 3-10 mol / L and a complexing agent solution with a concentration of 0.5-3 mol / L;

[0025] The alkali is one or two of sodium hydroxide and potassium hydroxide; the complexing agent is one or more of ammonia, disodium ethylenediaminetetraacetate, and sodium citrate.

[0026] Step (2): Nucleation stage:

[0027] Add a base solution (deionized water and complexing agent) to the reactor. The concentration of the complexing agent in the base solution is 0.01-0.05 mol / L. Heat the mixture to 40-80℃ and purge with nitrogen to remove oxygen. Pump the mixed metal salt solution, alkali solution and complexing agent solution from step (1) into the reactor continuously using a peristaltic pump. Control the pH of the reaction system to be 11.8-12.3, the stirring speed to be 500-1000 r / min, and the reaction time to be 0.5-10 h to form nano-thin disc-shaped primary particle nuclei.

[0028] Step (3): Directional stacking stage:

[0029] Keeping the flow rate of the mixed metal salt solution constant, the flow rate of the alkali solution was reduced to linearly decrease the pH to 10.1–11.0 (at a rate of 0.01–0.15 pH / h), and the stirring rate was increased to 600–1500 r / min. The reaction was carried out for 10–40 h, and the reaction was stopped when the particle size reached 4–20 μm. At this point, the thickness of the primary small disc particles was about 10–70 nm, the diameter was about 200–500 nm, the aspect ratio was about 0.05–0.25, and the roundness was 0.65–0.98. The slurry was released after aging.

[0030] Step (4): Post-processing:

[0031] The slurry from step (3) was subjected to solid-liquid separation to obtain a precipitate; the precipitate was washed with deionized water until the washing pH value was 7-8, and then dried at 80-120℃ for 8-40 h to obtain a manganese-rich cathode material precursor.

[0032] Thirdly, the present invention provides a cathode material, which is prepared by mixing and sintering a manganese-rich cathode material precursor composed of the above-mentioned nano-thin wafers with a lithium source.

[0033] The structural advantages of the precursor (uniform thin-film primary particles and controllable secondary particles) will be inherited by the cathode material, which will shorten the ion diffusion path, improve electrolyte wetting, and thus reduce mass transfer resistance, improving its rate performance by 15%-20%. Its simplified process also facilitates mass production, helping lithium-rich manganese-based cathode materials to enter fast charging and high-power energy storage scenarios.

[0034] Beneficial effects:

[0035] The manganese-rich cathode material precursor prepared by the method of this invention has the characteristics of uniform small thin-film primary particles and well-formed spherical or near-spherical secondary particles, and its crystal growth direction can also be controlled. This lays a good foundation for the subsequent preparation of lithium-rich manganese-based cathode materials. The precursor is composed of spherical or near-spherical secondary particles formed by the aggregation of nano-thin circular primary particles, with controllable particle size (D50 = 4–20 μm) and moderate specific surface area (10–80 μm). 2The thickness of the primary granular discs is approximately 10–70 nm, and the diameter is approximately 200–500 nm. The aspect ratio is approximately 0.05–0.25, and the roundness is 0.65–0.98. They exhibit good electrolyte wettability and excellent rate performance, effectively reducing the risk of gas expansion during battery storage. The preparation method achieves precise control of precursor morphology and performance by controlling parameters such as the concentration of metal salt solution, alkali and complexing agent solution, the linear decrease rate of pH during the stacking stage, and increasing the stirring speed. The process has a wide process window, good repeatability, and is suitable for large-scale industrial production.

[0036] The lithium-rich manganese-based cathode material prepared using the spherical or spherical manganese-rich precursor composed of nano-thin discs of the present invention exhibits good rate performance, with a 15%-20% improvement in rate performance compared to precursors of other morphologies. When applied to batteries, it can significantly improve the volumetric energy density of batteries and has broad market prospects.

[0037] The present invention has been described in detail above; however, the above embodiments are merely illustrative in nature and are not intended to limit the invention. Furthermore, this document is not limited to the foregoing prior art or the invention itself, or to any theory described in the following embodiments. Attached Figure Description

[0038] Figure 1 The image shows a 20,000x SEM image of the manganese-rich cathode material precursor prepared in Example 1.

[0039] Figure 2 A 50,000x SEM image of the manganese-rich cathode material precursor prepared in Example 1;

[0040] Figure 3 The image shows a 20,000x SEM image of the manganese-rich cathode material precursor prepared in Comparative Example 1.

[0041] Figure 4 The image shows a 50,000x SEM image of the manganese-rich cathode material precursor prepared in Comparative Example 1.

[0042] Figure 5 A 50,000x SEM image of the cathode material synthesized from the precursor prepared in Example 1;

[0043] Figure 6 The image shows a 50,000x SEM image of the cathode material synthesized from the precursor prepared in Comparative Example 1. Detailed Implementation

[0044] The present invention will be further described below with reference to the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention.

[0045] Unless otherwise specified, the raw materials, reagents, and methods used in the embodiments are all conventional raw materials, reagents, and methods in the art.

[0046] Example 1

[0047] Step 1: Prepare the metal salt solution: Dissolve nickel sulfate, cobalt sulfate, and manganese sulfate in deionized water at a molar ratio of 0.4:0.1:0.5 to obtain a mixed metal salt solution with a total metal ion concentration of 2 mol / L.

[0048] Step 2: Dissolve sodium hydroxide and ammonia in deionized water to obtain a sodium hydroxide solution with a concentration of 4 mol / L and an ammonia solution with a concentration of 2 mol / L, respectively.

[0049] Step 3: Add 1 L of bottom solution to a 5 L reactor. The ammonia concentration in the bottom solution is 0.02 mol / L. Heat to 50℃ and purge with nitrogen for 60 min to remove oxygen. Continuously pump the mixed metal salt solution from Step 1, the alkaline solution from Step 2, and the complexing agent solution into the reactor using a peristaltic pump. Control the pH of the reaction system to 12.1, the stirring speed to 800 r / min, and the reaction time to 2 h to form nano-thin, disc-shaped primary particle nuclei.

[0050] Step 4: Keep the flow rate of the metal salt solution constant, reduce the flow rate of the precipitant solution to linearly decrease the pH to 10.1 (rate 0.09 pH / h), increase the stirring rate to 900 r / min, react for 18 h, promote the directional stacking of nanosheets into spherical secondary particles, stop the reaction when the particle size reaches 5 μm, and release the slurry after aging.

[0051] Step 5: Perform solid-liquid separation on the slurry from Step 4 to obtain a precipitate; wash the precipitate with deionized water until the washing pH value is 7.8, and then dry it at 90°C for 24 h to obtain the manganese-rich cathode material precursor.

[0052] Example 2

[0053] Step 1: Prepare metal salt solution: Dissolve nickel nitrate, cobalt nitrate, and manganese nitrate in deionized water at a molar ratio of 0.2:0.1:0.7 to obtain a mixed metal salt solution with a total metal ion concentration of 1.5 mol / L;

[0054] Step 2: Dissolve potassium hydroxide and ammonia in deionized water to obtain a potassium hydroxide solution with a concentration of 3 mol / L and an ammonia solution with a concentration of 1 mol / L, respectively.

[0055] Step 3: Add 2 L of bottom solution to a 5 L reactor. The ammonia concentration in the bottom solution is 0.01 mol / L. Heat to 60℃ and purge with nitrogen for 30 min to remove oxygen. Continuously pump the mixed metal salt solution from Step 1, the alkaline solution from Step 2, and the complexing agent solution into the reactor using a peristaltic pump. Control the pH of the reaction system at 11.8, the stirring speed at 500 r / min, and the reaction time at 3 h to form nano-thin, circular, primary particle nuclei.

[0056] Step 4: Keep the flow rate of the metal salt solution constant, reduce the flow rate of the precipitant solution to linearly reduce the pH to 10.6 (rate 0.11 pH / h), increase the stirring rate to 600 r / min, react for 20 h, promote the directional stacking of nanosheets into spherical secondary particles, stop the reaction when the particle size reaches 6 μm, and release the slurry after aging.

[0057] Step 5: Perform solid-liquid separation on the slurry from Step 4 to obtain a precipitate; wash the precipitate with deionized water until the washing pH value is 7.2, and then dry it at 105℃ for 12 h to obtain the manganese-rich cathode material precursor.

[0058] Example 3

[0059] Step 1: Prepare the metal salt solution: Dissolve nickel chloride, cobalt chloride, and manganese chloride in deionized water at a molar ratio of 0.1:0.1:0.8 to obtain a mixed metal salt solution with a total metal ion concentration of 1.5 mol / L;

[0060] Step 2: Dissolve sodium hydroxide and disodium ethylenediaminetetraacetate in deionized water to obtain sodium hydroxide solution with a concentration of 8 mol / L and disodium ethylenediaminetetraacetate solution with a concentration of 0.5 mol / L, respectively.

[0061] Step 3: Add 1.8 L of base solution to a 5 L reactor. The concentration of disodium ethylenediaminetetraacetate in the base solution is 0.02 mol / L. Heat to 70 °C and purge with nitrogen for 45 min to remove oxygen. Continuously pump the mixed metal salt solution from Step 1, the alkaline solution from Step 2, and the complexing agent solution into the reactor using a peristaltic pump. Control the pH of the reaction system to 12.3, the stirring speed to 500 r / min, and the reaction time to 4 h to form nano-thin, circular, primary particle nuclei.

[0062] Step 4: Keep the flow rate of the metal salt solution constant, reduce the flow rate of the precipitant solution to linearly reduce the pH to 11.0 (rate 0.03 pH / h), increase the stirring rate to 700 r / min, react for 20 h, promote the directional stacking of nano-thin discs into spherical secondary particles, stop the reaction when the particle size reaches 7 μm, and release the slurry after aging.

[0063] Step 5: Perform solid-liquid separation on the slurry from Step 4 to obtain a precipitate; wash the precipitate with deionized water until the washing pH value is 8.0, and then dry it at 120℃ for 10 h to obtain the manganese-rich cathode material precursor.

[0064] Example 4

[0065] Step 1: Prepare the metal salt solution: Dissolve nickel sulfate, cobalt sulfate, and manganese sulfate in deionized water at a molar ratio of 0.1:0.4:0.5 to obtain a mixed metal salt solution with a total metal ion concentration of 3 mol / L.

[0066] Step 2: Dissolve sodium hydroxide and sodium citrate separately in deionized water to obtain sodium hydroxide solution with a concentration of 6 mol / L and sodium citrate solution with a concentration of 1 mol / L, respectively.

[0067] Step 3: Add 1.2 L of bottom solution to a 5 L reactor. The concentration of sodium citrate in the bottom solution is 0.04 mol / L. Heat to 60℃ and purge with nitrogen for 30 min to remove oxygen. Continuously pump the mixed metal salt solution from Step 1, the alkaline solution from Step 2, and the complexing agent solution into the reactor using a peristaltic pump. Control the pH of the reaction system to 12.1, the stirring speed to 600 r / min, and the reaction time to 6 h to form nano-thin, circular, primary particle nuclei.

[0068] Step 4: Keep the flow rate of the metal salt solution constant, reduce the flow rate of the precipitant solution to linearly decrease the pH to 10.4 (rate 0.05 pH / h), increase the stirring rate to 800 r / min, react for 20 h, promote the directional stacking of nano-thin discs into spherical secondary particles, stop the reaction when the particle size reaches 10 μm, and release the slurry after aging.

[0069] Step 5: Perform solid-liquid separation on the slurry from Step 4 to obtain a precipitate; wash the precipitate with deionized water until the washing pH value is 7.5, and then dry it at 100℃ for 15 h to obtain the manganese-rich cathode material precursor.

[0070] Comparative Example 1

[0071] The process conditions of this comparative example are basically the same as those of Example 1. The main difference is that in this comparative example, the stirring speed in step 4 is 800 rpm (not increased), and the pH decreases naturally without a linear relationship with time.

[0072] The 20,000x electron microscope image of the manganese-rich cathode material precursor prepared by the method in Comparative Example 1 is shown below. Figure 3 As shown, the 50,000x electron microscope image is as follows: Figure 4 As shown. Figure 3 , Figure 4Compared with the manganese-rich cathode material precursor prepared in Example 1 Figure 1 , Figure 2 Comparison, and based on the physical property data in Table 1, shows that the precursor of Example 1 has higher tap density, specific surface area, and sphericity, and the primary particle thickness is thinner. The precursor prepared in Comparative Example 1 shows a significant difference in appearance: the primary particles are coarse and long, with no exposed nano-thin discs on the surface, and the growth direction of the primary particles is basically different from that of Example 1. Furthermore, the precursors prepared in Examples 2-4, compared to Comparative Example 1, also possess the advantages of thinner primary plate-like particles, higher tap density, sphericity, and higher specific surface area.

[0073] Figure 5 and Figure 6 The images show 50,000x electron micrographs of the cathode materials synthesized from the precursors prepared in Example 1 and Comparative Example 1, respectively. The manganese-based precursors obtained in Example 1 and Comparative Example 1 were mixed uniformly with a lithium source at an excess of 2%, placed in a muffle furnace, and heated to 700°C at a heating rate of 5°C / min in air and held for 4 hours. Then, the temperature was increased to 950°C and held for 16 hours, and finally naturally cooled to room temperature to prepare lithium-rich manganese-based cathode materials. After the above cathode materials were fabricated into batteries, the rate performance was tested using a blue electric current meter at 25°C and a charge / discharge voltage of 2.0–4.4V at current densities of 0.1C, 0.2C, 0.5C, 1C, and 2C. The results show that the cathode materials of Example 1 and Comparative Example 1 both inherit some precursor characteristics. The primary particles in Example 1 are shorter, while those in Comparative Example 1 are longer. Furthermore, the primary particles in Example 1 are more conducive to electrolyte penetration and lithium-ion diffusion. The precursor physical property test results are shown in Table 1, and the specific rate performance data are shown in Table 2.

[0074] The physical property testing methods are as follows:

[0075] Primary particle thickness and diameter: obtained by field emission scanning electron microscopy;

[0076] Precursor roundness: Individual particles were segmented using ImageJ image analysis software to extract their complete outlines. The software automatically calculated the perimeter and area of ​​the primary particles in the thin discs. The average value of at least 10 primary particles in the thin discs was taken, and then calculated according to the formula. C = (A is the area, p is the perimeter) Calculate the overall circularity of the sample;

[0077] Precursor particle size: obtained using a Malvern 3000 laser particle size analyzer;

[0078] Precursor BET: obtained by specific surface area measurement;

[0079] Precursor tap density: obtained by tap density meter.

[0080] Table 1

[0081]

[0082] Table 2

[0083]

[0084] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and substance defined by the claims of the present invention; and such modifications or substitutions are still within the scope defined by the claims of the present invention.

Claims

1. A manganese-rich cathode material precursor composed of nanosheets, characterized in that, The manganese-rich cathode material precursor consists of spherical or near-spherical secondary particles composed of nano-thin, disc-shaped primary particles; and has the following characteristics: ( 1) The thickness of the primary particle thin disc is 20~50nm, the diameter is 200~500nm, the aspect ratio is 0.05~0.25, and the roundness is 0.95~0.98; (2) The particle size D50 of the secondary particles is 4 to 20 μm; (3) The specific surface area of ​​the precursor is 10–80 m². 2 / g.

2. The manganese-rich cathode material precursor composed of nanosheets according to claim 1, characterized in that, The primary particle wafers of the precursor have the following characteristics: thickness of 30~40nm; diameter of 250~400nm; and thickness-to-diameter ratio of 0.06~0.

1.

3. The manganese-rich cathode material precursor composed of nanosheets according to claim 2, characterized in that, The primary particle wafers of the precursor have the following characteristics: diameter length of 300~350nm; thickness-to-diameter ratio of 0.07~0.

075.

4. The manganese-rich cathode material precursor composed of nanosheets according to claim 1, characterized in that, The secondary particles of the precursor have a particle size D50 of 5~10μm; The specific surface area of ​​the precursor is 20~60m². 2 / g.

5. The manganese-rich cathode material precursor composed of nanosheets according to claim 4, characterized in that, The secondary particles of the precursor have a particle size D50 of 5~7μm; The specific surface area of ​​the precursor is 30~45m². 2 / g.

6. The manganese-rich cathode material precursor composed of nanosheets according to claim 1, characterized in that, The chemical formula of the manganese-rich cathode material precursor is Ni. x Mn y Co 1-x-y (OH)2, where 0.1≤x≤0.5, 0.5≤y≤0.

9.

7. The manganese-rich cathode material precursor composed of nanosheets according to claim 6, characterized in that, In the chemical formula of the manganese-rich cathode material precursor, the value of x ranges from 0.3 to 0.5, and the value of y ranges from 0.5 to 0.

7.

8. A method for preparing a manganese-rich cathode material precursor composed of nanosheets as described in any one of claims 1-7, characterized in that, Includes the following steps: (1) Dissolve nickel salt, cobalt salt and manganese salt in deionized water to obtain a mixed metal salt solution; dissolve alkali and complexing agent in deionized water to obtain alkali solution and complexing agent solution respectively; (2) Add the bottom liquid to the reactor, heat it up and then introduce nitrogen to remove oxygen; pump the mixed metal salt solution, alkaline solution and complexing agent solution from step (1) into the reactor continuously through a peristaltic pump, control the pH value and stirring speed of the reaction system, and form nano-thin disc-shaped primary particle nuclei. (3) Keep the flow rate of the mixed metal salt solution constant, reduce the flow rate of the alkaline solution to make the pH decrease linearly, and increase the stirring speed. Stop the reaction when the particle size reaches the set value; release the slurry after aging. (4) The slurry from step (3) is subjected to solid-liquid separation to obtain a precipitate; the precipitate is washed with deionized water and then dried to obtain a manganese-rich cathode material precursor composed of nano-thin discs.

9. The preparation method according to claim 8, characterized in that, In step (1), the total concentration of metal ions in the mixed metal salt solution is 0.5–3 mol / L; The nickel salt is one or more of nickel sulfate, nickel nitrate, or nickel chloride; the manganese salt is one or more of manganese sulfate, manganese nitrate, or manganese chloride; the cobalt salt is one or more of cobalt sulfate, cobalt nitrate, or cobalt chloride. The alkaline concentration of the alkaline solution is 3–10 mol / L, and the complexing agent concentration of the complexing agent solution is 0.5–3 mol / L. The alkali is one or two of sodium hydroxide and potassium hydroxide; the complexing agent is one or more of ammonia, disodium ethylenediaminetetraacetate, and sodium citrate.

10. The preparation method according to claim 8, characterized in that, In step (2), the reaction temperature is controlled at 40-80℃, the pH value of the reaction system is 11.8-12.3, the stirring speed is 500-1000 r / min, and the reaction time is 0.5-10 h.

11. The preparation method according to claim 8, characterized in that, In step (3), the flow rate of the alkaline solution is reduced so that the pH drops linearly to 10.1 to 11.0 at a rate of 0.01 to 0.15 pH / h, the stirring rate is increased to 600 to 1500 r / min, and the reaction time is controlled at 10 to 40 h.

12. The preparation method according to claim 8, characterized in that, In step (4), the washing is performed until the pH value is 7-8, the drying temperature is 80-120℃, and the drying time is 8-40h.

13. A positive electrode material, characterized in that, The precursor of a manganese-rich cathode material composed of nano-thin discs as described in any one of claims 1-7 or the precursor of a manganese-rich cathode material composed of nano-thin discs prepared by the preparation method described in any one of claims 8-12 is prepared by mixing and sintering with a lithium source.

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