Preparation method of low-cost prussian blue type sodium ion battery positive electrode material

Abstract

The application discloses a preparation method of a low-cost Prussian blue type sodium ion battery positive electrode material and belongs to the sodium ion battery field. In order to solve the problems of large wastewater quantity and high cost in the synthesis process of the Prussian blue type sodium ion battery positive electrode material by a liquid phase method, an improved liquid phase method for preparing the Prussian blue type sodium ion battery positive electrode material is provided. The improved liquid phase method is combined with a solid feeding and liquid feeding feeding mode or directly uses a solid feeding mode to perform co-precipitation synthesis, and the filtrate is recycled, that is, the mother liquor is used for reaction liquid preparation and pre-liquid addition again to perform the next synthesis. The obtained Prussian blue type sodium ion battery positive electrode material has little difference in electrical performance compared with the liquid phase method, but the wastewater quantity in the synthesis process of the improved liquid phase method is greatly reduced, the input of the complexing agent is not needed, the cost is greatly reduced, and the process is particularly simple, so that the industrialization process of the sodium ion battery can be accelerated.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery cathode materials, specifically to a method for preparing a low-cost Prussian blue sodium-ion battery cathode material. Background Technology

[0002] Lithium-ion batteries are currently considered superior chemical energy storage devices due to their high energy density and long cycle life, and are widely used in electronic products, high-power electric vehicles, energy storage power stations, and smart grids. However, the rapid increase in demand for lithium-ion battery energy storage devices in the energy storage and power battery markets has led to a continuous increase in lithium resource consumption and a steady rise in the price of lithium carbonate and lithium batteries, making it impossible to meet the growing demand for low-cost and high-energy / efficiency large-scale power storage facilities in the future. Sodium, located in the same group as lithium (Group 1), has similar chemical properties and a working principle very similar to lithium batteries, both being typical rocking chair batteries. Compared to lithium resources, sodium reserves are quite abundant, more evenly distributed geographically, and inexpensive. Therefore, sodium-ion batteries have greater advantages and potential for large-scale energy storage.

[0003] Prussian blue analogues are among the three most promising industrially viable cathode materials for sodium-ion batteries. Their excellent electrochemical performance and high energy density are due to their open three-dimensional structure and abundant sodium-ion storage sites. There are many methods for synthesizing Prussian blue-based sodium-ion cathode materials, with the following showing promising industrial potential: 1) Synthesis via liquid-phase co-precipitation. This method involves first dissolving the reactants by stirring, then feeding them into the liquid phase for co-precipitation. However, due to the inherent solubility limitations of the reactants, this method results in low solid content and low yield of the reaction product. Furthermore, because Prussian blue reacts very rapidly, to obtain low-defect, high-performance Prussian blue cathode materials, a slow growth method with a large amount of complexing agent is generally used. This method results in a large amount of complexing agent in the filtrate after the reaction. The common ion effect between the sodium salt of the complexing agent and the reactants makes it impossible to completely recycle the filtrate for synthesis. Therefore, the wastewater volume is large and the amount of complexing agent used is large, resulting in a relatively high production cost of the material; 2) Solid-phase ball milling synthesis method, such as patent CN109638241B and patent application CN114715917A, has the advantage of directly mixing and milling through solid-phase feeding, without the need for water dissolution or the addition of complexing agents, resulting in a high synthesis yield and relatively low cost. However, the Prussian blue-like materials synthesized by this method have very small particle sizes, making the cleaning and collection process very difficult. In addition, the electrical properties of the material are poor, far inferior to those synthesized by the liquid-phase method. Therefore, developing a low-cost Prussian blue-like sodium-ion battery cathode material that ensures performance is of great significance for the actual industrial application of Prussian blue-like sodium-ion batteries. Summary of the Invention

[0004] This invention aims to solve the problems of large wastewater volume and high cost in the existing liquid-phase synthesis of Prussian blue sodium-ion battery cathode materials, and provides a low-cost method for preparing Prussian blue sodium-ion battery cathode materials.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a low-cost Prussian blue-based sodium-ion battery cathode material includes the following steps:

[0007] Sodium ferrocyanide solid A and mixture B were simultaneously added in equal molar amounts to solution C, and a coprecipitation reaction was carried out under stirring. After the reaction was completed, the mixture was aged to obtain a suspension. The suspension was separated, the precipitate was collected, washed and dried to obtain Prussian blue sodium-ion battery cathode material.

[0008] The mixture B is either solution B1 or solid B2. Solution B1 is prepared by dissolving transition metal salt M1, doped metal salt M2, antioxidant and complexing agent in deoxygenated deionized water to prepare solution B1. Solid B2 is a mixture of transition metal salt M1 and doped metal salt M2.

[0009] The method for preparing solution C is as follows: dissolve the antioxidant and complexing agent in deoxygenated deionized water to prepare solution C;

[0010] Equimolar amounts of sodium ferrocyanide solid A and mixture B refer to the sum of the molar amounts of sodium ferrocyanide and the molar amounts of transition metal salt M1 and doped metal salt M2 in mixture B.

[0011] After separating the suspension, the filtrate is collected. When preparing Prussian blue sodium-ion battery cathode materials again, the transition metal salt M1, the doped metal salt M2, and the antioxidant are dissolved in the deoxygenated filtrate and used as solution B1 for recycling; the antioxidant is dissolved in the deoxygenated filtrate and used as solution C for recycling.

[0012] The filtrate is recycled several times until, when solutions B1 and C are prepared again, solid particles in solution B1 cannot be dissolved or solution C reaches saturation, at which point it is discarded.

[0013] Compared with the prior art, the beneficial effects of the present invention are:

[0014] The Prussian blue-based sodium-ion battery cathode material prepared by the method of this invention shows little difference in electrical performance compared to that prepared by the original liquid-phase method. However, the method of this invention significantly reduces wastewater generation during synthesis, eliminates the need for complexing agents, greatly lowers costs, and simplifies the process, thus accelerating the industrialization of sodium-ion batteries. Therefore, the preparation method of the Prussian blue-based cathode material of this invention has excellent application prospects. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the reaction apparatus for the Prussian blue sodium-ion battery cathode material in the comparative example of this invention;

[0016] Figure 2 This is a schematic diagram of the reaction apparatus for a low-cost Prussian blue sodium-ion battery cathode material in Embodiments 1 and 2 of the present invention;

[0017] Figure 3 This is a schematic diagram of the reaction apparatus for a low-cost Prussian blue sodium-ion battery cathode material in Embodiments 3 and 4 of the present invention;

[0018] Figure 4 The graph shows the cycling performance of a sodium-ion half-cell containing the Prussian blue sodium-ion battery cathode material prepared in the comparative example of this invention at a current density of 140 mA / g.

[0019] Figure 5 The graph shows the cycling performance of a sodium-ion half-cell containing the Prussian blue sodium-ion battery cathode material prepared in Examples 1 and 2 of this invention at a current density of 140 mA / g.

[0020] Figure 6 The graph shows the cycling performance of a sodium-ion half-cell containing the Prussian blue sodium-ion battery cathode material prepared in Examples 3 and 4 of this invention at a current density of 140 mA / g.

[0021] Figure 7 This is a comparison chart of the cycling performance of sodium-ion half-cells containing Prussian blue sodium-ion battery cathode materials prepared in Comparative Examples, Examples 1, 2, 3 and 4 of this invention at a current density of 140 mA / g. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Specific Implementation Method 1

[0024] A method for preparing a low-cost Prussian blue-based sodium-ion battery cathode material specifically includes the following steps:

[0025] Sodium ferrocyanide solid A and mixture B were simultaneously added in equal molar amounts to solution C, and a coprecipitation reaction was carried out under stirring. After the reaction was completed, the mixture was aged to obtain a suspension. The suspension was separated, and the separated precipitate and filtrate were collected. The precipitate was washed and dried to obtain Prussian blue sodium-ion battery cathode material.

[0026] The mixture B is either solution B1 or solid B2. Solution B1 is prepared by dissolving transition metal salt M1, doped metal salt M2, antioxidant and complexing agent in deoxygenated deionized water to prepare solution B1. Solid B2 is a mixture of transition metal salt M1 and doped metal salt M2.

[0027] The solution C is prepared by dissolving the antioxidant and complexing agent in deoxygenated deionized water.

[0028] Equimolar amounts of sodium ferrocyanide solid A and mixture B refer to the sum of the molar amounts of sodium ferrocyanide and the molar amounts of transition metal salt M1 and doped metal salt M2 in mixture B.

[0029] The collected filtrate is used to replace deionized water when preparing Prussian blue sodium-ion battery cathode materials again. No complexing agent needs to be added. The transition metal salt M1, doped metal salt M2, and antioxidant are dissolved in the deoxygenated filtrate as solution B1 and recycled. The antioxidant is dissolved in the deoxygenated filtrate as solution C and recycled. The filtrate is recycled several times until solutions B1 and C are prepared again. If solid particles in solution B1 cannot dissolve or solution C reaches saturation, it is discarded.

[0030] Furthermore, the sum of the concentrations of transition metal salt M1 and doped metal salt M2 in solution B1 is 0.05–3 mol / L; the molar ratio of transition metal salt M1 and doped metal salt M2 in both solution B1 and solid B2 is no greater than 1:1.

[0031] Furthermore, the transition metal salt M1 is a soluble salt of Ni, Mn, Fe, CO, Zn, Cr, Cu, or V; the doped metal salt M2 is one or more combinations of sulfates, nitrates, and chlorides of Ni, CO, Fe, Mn, Mg, Al, Zn, or Cu.

[0032] Furthermore, the antioxidant is one or more of butylated hydroxyanisole, butylated hydroxytoluene, propyl gallate, tert-butylhydroquinone, and ascorbic acid, preferably ascorbic acid; the complexing agent is at least one of trisodium citrate, citric acid, ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetic acid, and tetrasodium ethylenediaminetetraacetic acid.

[0033] Furthermore, in the reactants, solution B1 is fed precisely via a peristaltic pump or a mechanical gear pump, while solids A and B2 are both fed via a vibrating feeder.

[0034] Furthermore, in solutions B1 and C, the molar concentration of the complexing agent was 0.1–3 mol / L, and the pH was controlled between 4 and 7.

[0035] Furthermore, the temperature of the reaction system is controlled at 0–80°C, the coprecipitation reaction time is 2–24 h, and the aging time is 0.5–24 h. During the coprecipitation reaction, a protective gas is continuously introduced into the reaction system to remove oxygen from the reaction system. The protective gas is at least one of nitrogen and argon.

[0036] Furthermore, the suspension is separated by centrifugation, vacuum filtration, or pressure filtration; the drying process is vacuum drying, with a vacuum degree of 0.1 MPa or below, a temperature of 120–170°C, and a time of 8–20 h.

[0037] The present invention employs a combination of solid and liquid feeding methods, or directly uses solid feeding, to synthesize the reactants via co-precipitation. The filtrate (waste liquid or mother liquor) is recycled, meaning the mother liquor is entirely reused in the reaction mixture preparation and pre-addition for the next synthesis. This significantly reduces wastewater generation during the synthesis process, eliminates the need for complexing agents, and greatly lowers costs. The present invention discloses a low-cost method for preparing Prussian blue-based sodium-ion battery cathode materials, which is simple in process and can accelerate the industrialization of sodium-ion batteries.

[0038] Comparative Example

[0039] This comparative example provides a conventional liquid-phase method for preparing Prussian blue sodium-ion battery cathode materials, including the following steps:

[0040] Step 1: Dissolve 0.2 mol of sodium ferrocyanide decahydrate in 550 ml of deoxygenated deionized water to obtain reaction solution A;

[0041] Step 2: Dissolve 0.17 mol of ferrous sulfate heptahydrate, 0.03 mol of manganese sulfate monohydrate, 0.6 mol of trisodium citrate dihydrate, 0.4 mol of citric acid monohydrate, and 8 g of ascorbic acid (VC) in 468 ml of deoxygenated deionized water to obtain reaction solution B.

[0042] Step 3: Dissolve 1 mol of trisodium citrate dihydrate and 15 g of ascorbic acid (VC) in 600 ml of deoxygenated deionized water to obtain solution C.

[0043] use Figure 1 The apparatus shown is used for a coprecipitation reaction. Container A contains reaction solution A, container B contains reaction solution B, and container C contains solution C. Reaction solutions A and B are simultaneously added dropwise to solution C at a flow rate of 1 mL / min using a peristaltic pump through a silicone tube, with equal volumes. The stirrer in container C operates at 500 rpm. N2 is introduced into containers A, B, and C at a flow rate of 60 mL / min during the reaction. The temperature of solution C is maintained at 40°C, and the stirring speed is 500 rpm / min. After the addition of reaction solutions A and B is complete, stirring continues for 2 hours, followed by aging for 12 hours to obtain a suspension.

[0044] The suspension was centrifuged at 4500 rpm for 5 min, and the resulting precipitate was centrifuged and washed with deoxygenated deionized water, repeated three times. It was then placed in a vacuum oven at 0.1 MPa and dried at 120°C for 12 hours to obtain the Prussian blue sodium-ion battery cathode material.

[0045] The Prussian blue sodium-ion battery cathode material prepared in this comparative example was mixed evenly in a weight ratio of active material: carbon black: PVDF = 8:1:1, coated onto a 20µm aluminum foil current collector, dried, punched, pressed, weighed, and then placed in a vacuum oven with a vacuum degree below 50 Pa and dried at 120°C for 15 hours. After that, it was removed and transferred to a glove box. Glass fiber was used as the separator; 1 mol / L NaPF6, solvent EC:DEC = 1:1, and 5% FEC were added as electrolyte. Sodium-ion half-cells were assembled and their electrical performance was tested. The initial discharge capacity at a current density of 0.1C was 142.9 mAh / g, and the capacity retention rate after 100 cycles at 1C was 96.7%.

[0046] Example 1

[0047] This embodiment provides a method for preparing a low-cost Prussian blue-based sodium-ion battery cathode material, including the following steps:

[0048] Step 1: Weigh out 0.2 mol of sodium ferrocyanide decahydrate, and denote it as solid A;

[0049] Step 2: Dissolve 0.17 mol of ferrous sulfate heptahydrate, 0.03 mol of manganese sulfate monohydrate, 0.6 mol of trisodium citrate dihydrate, 0.4 mol of citric acid monohydrate, and 8 g of ascorbic acid (VC) in 468 ml of deoxygenated deionized water to obtain reaction solution B.

[0050] Step 3: Dissolve 1 mol of trisodium citrate dihydrate and 15 g of ascorbic acid (VC) in 600 ml of deoxygenated deionized water to obtain solution C.

[0051] use Figure 2 The apparatus shown is used for a co-precipitation reaction. Container B contains reaction solution B, and container C contains solution C. Solid A is fed by adjusting the vibration frequency of a vibrating feeder. Reaction solution B is fed by a peristaltic pump through a silicone tube at a flow rate of 1 mL / min. Solid A and reaction solution B are simultaneously added to solution C in equal molar amounts. The stirrer in container C is maintained at 500 rpm. N2 is introduced into containers A, B, and C at a flow rate of 60 mL / min during the reaction. The temperature of solution C is maintained at 40°C, and the stirring speed is 500 rpm / min. After solid A and reaction solution B have been added, stirring continues for 2 hours, followed by aging for 12 hours to obtain a suspension.

[0052] The suspension was centrifuged at 4500 rpm for 5 min, and the filtrate (mother liquor) was collected for later use. The precipitate was centrifuged and washed three times with deoxygenated deionized water. Then, it was placed in a vacuum oven with a vacuum degree of 0.1 MPa and dried at 120°C for 12 hours to obtain the Prussian blue sodium-ion battery cathode material.

[0053] The Prussian blue sodium-ion battery cathode material prepared in this embodiment was evaluated for its electrical performance using the same method as the comparative example. The initial discharge capacity at a current density of 0.1C was 142.7 mAh / g, and the capacity retention rate after 100 cycles at 1C was 96.9%.

[0054] Example 2

[0055] This embodiment provides a method for preparing a low-cost Prussian blue-based sodium-ion battery cathode material, including the following steps:

[0056] Step 1: Weigh out 0.2 mol of sodium ferrocyanide decahydrate, and denote it as solid A;

[0057] Step 2: Dissolve 0.17 mol of ferrous sulfate heptahydrate, 0.03 mol of manganese sulfate monohydrate, and 8 g of ascorbic acid (VC) in 468 ml of the mother liquor from Example 1 after centrifugation and filtration to remove peroxide, to obtain reaction solution B;

[0058] Step 3: Dissolve 15g of ascorbic acid (VC) in 600ml of mother liquor from Example 1 after centrifugation and filtration to obtain solution C.

[0059] use Figure 2The apparatus shown is used for a co-precipitation reaction. Container B contains reaction solution B, and container C contains solution C. Solid A is fed by adjusting the vibration frequency of a vibrating feeder. Reaction solution B is fed by a peristaltic pump through a silicone tube at a flow rate of 1 mL / min. Solid A and reaction solution B are simultaneously added to solution C in equal molar amounts. The stirrer in container C is maintained at 500 rpm. N2 is introduced into containers A, B, and C at a flow rate of 60 mL / min during the reaction. The temperature of solution C is maintained at 40°C, and the stirring speed is 500 rpm / min. After solid A and reaction solution B have been added, stirring continues for 2 hours, followed by aging for 12 hours to obtain a suspension.

[0060] The suspension was centrifuged at 4500 rpm for 5 min, and the filtrate (mother liquor) was collected for later use. The precipitate was centrifuged and washed three times with deoxygenated deionized water. Then, it was placed in a vacuum oven with a vacuum degree of 0.1 MPa and dried at 120°C for 12 hours to obtain the Prussian blue sodium-ion battery cathode material.

[0061] The Prussian blue sodium-ion battery cathode material prepared in this embodiment was evaluated for its electrical performance using the same method as the comparative example. The initial discharge capacity at a current density of 0.1C was 142.9 mAh / g, and the capacity retention rate after 100 cycles at 1C was 95.7%.

[0062] Example 3

[0063] This embodiment provides a method for preparing a low-cost Prussian blue-based sodium-ion battery cathode material, including the following steps:

[0064] Step 1: Weigh out 0.2 mol of sodium ferrocyanide decahydrate, and denote it as solid A;

[0065] Step 2: Weigh 0.17 mol of ferrous sulfate heptahydrate and 0.03 mol of manganese sulfate monohydrate and mix them evenly, denoted as solid B;

[0066] Step 3: Dissolve 1.6 mol of trisodium citrate dihydrate and 23 g of ascorbic acid (VC) in 600 ml of deoxygenated deionized water to obtain solution C.

[0067] use Figure 3 The apparatus shown undergoes a co-precipitation reaction, where container C contains liquid C, and solids A and B are controlled by adjusting the vibration frequency of a vibrating feeder at 0.3*10. -3The feed was simultaneously added equimolarly to solution C at a feed rate of mol / min, with the stirrer speed in container C controlled at 500 rpm. N2 was introduced into containers A, B, and C at a flow rate of 60 mL / min during the reaction. The temperature of solution C was maintained at 40℃, and the stirring speed was 500 rpm / min. After solids A and B were added, stirring continued for 2 hours, followed by standing and aging for 12 hours to obtain a suspension.

[0068] The suspension was centrifuged at 4500 rpm for 5 min, and the filtrate (mother liquor) was collected for later use. The precipitate was centrifuged and washed three times with deoxygenated deionized water. Then, it was placed in a vacuum oven with a vacuum degree of 0.1 MPa and dried at 120°C for 12 hours to obtain the Prussian blue sodium-ion battery cathode material.

[0069] The Prussian blue sodium-ion battery cathode material prepared in this embodiment was evaluated for its electrical performance using the same method as the comparative example. The initial discharge capacity at a current density of 0.1C was 141.5 mAh / g, and the capacity retention rate after 100 cycles at 1C was 95.79%.

[0070] Example 4

[0071] This embodiment provides a method for preparing a low-cost Prussian blue-based sodium-ion battery cathode material, including the following steps:

[0072] Step 1: Weigh out 0.2 mol of sodium ferrocyanide decahydrate, and denote it as solid A;

[0073] Step 2: Weigh 0.17 mol of ferrous sulfate heptahydrate and 0.03 mol of manganese sulfate monohydrate and mix them evenly, denoted as solid B;

[0074] Step 3: Dissolve 15g of ascorbic acid (VC) in the mother liquor after centrifugation and filtration in Example 3 (which has been deoxygenated) to obtain solution C.

[0075] use Figure 3 The apparatus shown undergoes a co-precipitation reaction, where container C contains liquid C, and solids A and B are controlled by adjusting the vibration frequency of a vibrating feeder at 0.3*10. -3 The feed rate was mol / min, and the same amount of N2 was added to solution C simultaneously. The stirrer speed in container C was controlled at 500 rpm. During the reaction, N2 was introduced into containers A, B, and C at a flow rate of 60 mL / min. The temperature of solution C was maintained at 40℃, and the stirring speed was 500 rpm / min. After solids A and B were added, stirring continued for 2 hours, followed by standing and aging for 12 hours to obtain a suspension.

[0076] The suspension was centrifuged at 4500 rpm for 5 min, and the filtrate (mother liquor) was collected for later use. The precipitate was centrifuged and washed three times with deoxygenated deionized water. Then, it was placed in a vacuum oven with a vacuum degree of 0.1 MPa and dried at 120°C for 12 hours to obtain the Prussian blue sodium-ion battery cathode material.

[0077] The Prussian blue sodium-ion battery cathode material prepared in this embodiment was evaluated for its electrical performance using the same method as the comparative example. The initial discharge capacity at a current density of 0.1C was 142 mAh / g, and the capacity retention rate after 100 cycles at 1C was 95.85%.

[0078] The electrical performance data from the comparative examples and embodiments show that, compared with the original liquid-phase method, the Prussian blue-based sodium-ion battery cathode material prepared by the proposed improved liquid-phase method is not significantly different in terms of discharge specific capacity and cycle capacity retention at 1C. However, the improved liquid-phase method proposed in this invention greatly reduces wastewater generation during synthesis, eliminates the need for complexing agents, significantly lowers costs, simplifies the process, and can be directly converted into industrial production, thus accelerating the industrialization of sodium-ion batteries. Therefore, the Prussian blue-based cathode material prepared by the method of this invention has excellent application prospects.

[0079] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a low-cost Prussian blue-based sodium-ion battery cathode material, characterized in that, Includes the following steps: Sodium ferrocyanide solid A and mixture B were simultaneously added in equal molar amounts to solution C, and a coprecipitation reaction was carried out under stirring. After the reaction was completed, the mixture was aged to obtain a suspension. The suspension was separated, the precipitate was collected, washed and dried to obtain Prussian blue sodium-ion battery cathode material. The mixture B is either solution B1 or solid B2. Solution B1 is prepared by dissolving transition metal salt M1, doped metal salt M2, antioxidant and complexing agent in deoxygenated deionized water to prepare solution B1. Solid B2 is a mixture of transition metal salt M1 and doped metal salt M2. The method for preparing solution C is as follows: dissolve the antioxidant and complexing agent in deoxygenated deionized water to prepare solution C; Equimolar amounts of sodium ferrocyanide solid A and mixture B refer to the sum of the molar amounts of sodium ferrocyanide and the molar amounts of transition metal salt M1 and doped metal salt M2 in mixture B.

2. The preparation method according to claim 1, characterized in that: After separating the suspension, the filtrate is collected. When preparing Prussian blue sodium-ion battery cathode materials again, the transition metal salt M1, the doped metal salt M2, and the antioxidant are dissolved in the deoxygenated filtrate and used as solution B1 for recycling; the antioxidant is dissolved in the deoxygenated filtrate and used as solution C for recycling.

3. The preparation method according to claim 2, characterized in that: The filtrate is recycled several times until, when solutions B1 and C are prepared again, solid particles in solution B1 cannot be dissolved or solution C reaches saturation, at which point it is discarded.

4. The preparation method according to claim 1, characterized in that: The sum of the concentrations of transition metal salt M1 and doped metal salt M2 in solution B1 is 0.05–3 mol / L; the molar ratio of transition metal salt M1 and doped metal salt M2 in both solution B1 and solid B2 is no greater than 1:

1.

5. The preparation method according to claim 1, characterized in that: The transition metal salt M1 is a soluble salt of Ni, Mn, Fe, CO, Zn, Cr, Cu, or V; the doped metal salt M2 is one or more of the sulfate, nitrate, and chloride salts of Ni, CO, Fe, Mn, Mg, Al, Zn, or Cu.

6. The preparation method according to claim 1, characterized in that: The antioxidant is one or more of butylated hydroxyanisole, butylated hydroxytoluene, propyl gallate, tert-butylhydroquinone, and ascorbic acid; the complexing agent is at least one of trisodium citrate, citric acid, ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetic acid, and tetrasodium ethylenediaminetetraacetic acid.

7. The preparation method according to claim 1, characterized in that: In the reactants, solution B1 is fed precisely via a peristaltic pump or a mechanical gear pump, while solids A and B2 are fed via a vibrating feeder.

8. The preparation method according to claim 1, characterized in that: In solutions B1 and C, the concentration of the complexing agent is 0.1–3 mol / L, and the pH is 4–7.

9. The preparation method according to claim 1, characterized in that: The temperature of the reaction system is controlled at 0–80℃, the coprecipitation reaction time is 2–24 h, and the aging time is 0.5–24 h. During the coprecipitation reaction, a protective gas is continuously introduced into the reaction system to remove oxygen.

10. The preparation method according to claim 1, characterized in that: The suspension is separated by centrifugation, vacuum filtration, or pressure filtration; the drying process is vacuum drying, with a vacuum degree of 0.1 MPa or below, a temperature of 120–170°C, and a time of 8–20 h.

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