CN-117480118-B - Ferric phosphate and preparation method and application thereof

Abstract

The invention provides ferric phosphate and a preparation method and application thereof, wherein the preparation method comprises the following steps of (1) mixing ferrous salt, a phosphorus source and a solvent to obtain mixed salt solution, freezing the mixed solution to obtain frozen mixed salt solution, (2) placing the frozen mixed salt solution in a reflux device, controlling the reflux of hydrogen peroxide solution between the reflux device and a reaction device, controlling the concentration of hydrogen peroxide in a system to react until the frozen mixed salt solution is completely dissolved, (3) adjusting the pH in the system to perform aging reaction, and performing solid-liquid separation to obtain the ferric phosphate. According to the method, the solution containing ferrous salt and a phosphorus source is frozen in advance, hydrogen peroxide is controlled to flow through the frozen mixed salt solution, and the reaction can be slowly carried out by controlling the concentration and the flow rate of the hydrogen peroxide, so that iron elements and phosphorus elements in the prepared ferric phosphate precursor are uniformly distributed, and the surface defects are few.

Inventors

• LI AIXIA
• XIE YINGHAO
• YU HAIJUN
• LI CHANGDONG

Assignees

• 广东邦普循环科技有限公司
• 湖南邦普循环科技有限公司

Dates

Publication Date

20260505

Application Date

20230914

Claims (20)

1. 1. A method of preparing iron phosphate, the method comprising the steps of: (1) Mixing ferrous salt, a phosphorus source and a solvent to obtain a mixed salt solution, and carrying out freezing treatment on the mixed salt solution to obtain a frozen mixed salt solution; (2) Placing the frozen mixed salt solution in a reflux device, controlling the hydrogen peroxide solution to reflux between the reflux device and a reaction device, and controlling the concentration of the hydrogen peroxide in the system to react until the frozen mixed salt solution is completely dissolved; (3) Adjusting pH in the system to perform an aging reaction, and performing solid-liquid separation to obtain the ferric phosphate; the reflux speed of the hydrogen peroxide solution in the step (2) is 50-100 mL/min; and (3) the mass concentration of the hydrogen peroxide in the reaction in the step (2) is 5-10%.
2. 2. The method of claim 1, wherein the ferrous salt of step (1) comprises any one or a combination of at least two of ferrous chloride, ferrous sulfate, or ferrous nitrate.
3. 3. The method of claim 1, wherein the phosphorus source of step (1) comprises any one or a combination of at least two of phosphoric acid, monoammonium phosphate, diammonium phosphate, or ammonium phosphate.
4. 4. The method according to claim 1, wherein the concentration of iron in the mixed salt solution in the step (1) is 0.05 to 1mol/L.
5. 5. The method according to claim 1, wherein the concentration of phosphorus in the mixed salt solution in the step (1) is 0.5 to 1mol/L.
6. 6. The preparation method of claim 1, wherein the pH of the mixed salt solution in the step (1) is 1.8-2.5.
7. 7. The method according to claim 1, wherein the temperature of the freezing treatment in the step (1) is-30 to-40 ℃.
8. 8. The preparation method of claim 1, wherein the time of the freezing treatment in the step (1) is 6-12 hours.
9. 9. The preparation method of claim 1, wherein the mass concentration of the hydrogen peroxide solution in the step (2) is 5-10%.
10. 10. The preparation method of claim 1, wherein the molar ratio of the total molar amount of hydrogen peroxide in the hydrogen peroxide solution in the step (2) to the molar amount of iron in the iron source is (1-2): 1.
11. 11. The preparation method of claim 1, wherein the reaction temperature in the step (2) is 40-60 ℃.
12. 12. The process according to claim 1, wherein phosphoric acid is added to control the pH during the reaction in step (2).
13. 13. The method according to claim 1, wherein the pH in the step (2) is controlled to be 1.8 to 2.5.
14. 14. The process according to claim 1, wherein the pH adjuster in the system in the step (3) comprises ammonia.
15. 15. The method according to claim 1, wherein the pH in the step (3) is 2.5 to 3.5.
16. 16. The preparation method of claim 1, wherein the aging reaction in the step (3) is performed at a temperature of 40-80 ℃.
17. 17. The preparation method of claim 1, wherein the stirring speed of the aging reaction in the step (3) is 100-200 rpm.
18. 18. The preparation method of claim 1, wherein the aging reaction time of the step (3) is 10-60 hours.
19. 19. The process according to claim 1, wherein the solid-liquid separation in step (3) is followed by washing and vacuum drying.
20. 20. The method of claim 19, wherein the washed detergent comprises deionized water.

Description

Ferric phosphate and preparation method and application thereof Technical Field The present disclosure belongs to the technical field of battery materials, and relates to an iron phosphate, a preparation method and an application thereof. Background The iron phosphate is a white and off-white monoclinic crystal powder, and is mainly used for preparing lithium iron phosphate anode materials, catalysts, ceramics and the like. With the rapid development of lithium iron phosphate batteries, the demand for iron phosphate as one of the main precursors of lithium iron phosphate cathode materials is greatly increased, and the demand can be expected to be greater than 5 ten thousand tons per year. The structure of the ferric phosphate is very similar to that of the lithium iron phosphate, so that the performance of the lithium iron phosphate can be controlled by controlling the structure, morphology and granularity of the ferric phosphate, and the prior art generally adopts a precipitation method or a solid phase method to synthesize the lithium iron phosphate. CN116443834a discloses a method for continuously synthesizing ferric phosphate by using a microreactor, which comprises the steps of respectively introducing a raw material liquid for synthesizing ferric phosphate by an iron method and an oxidizing liquid into the microreactor to mix, reacting in the microreactor in a dynamic environment to obtain product slurry, and carrying out post-treatment on the product slurry to obtain ferric phosphate. CN103682341a discloses a synthesis method of a high tap density lithium iron phosphate material, which prepares ferric phosphate dihydrate precipitate by a precipitation method, and then mixes and sinters a ferric phosphate precursor with a lithium source, a carbon source and the like to obtain a carbon-coated lithium iron phosphate anode material. The ferric phosphate particles obtained by the scheme are larger, the particle size distribution is wider, sulfate radical is easy to be entrained in the synthesized ferric phosphate when sulfate is adopted as a raw material for precipitation, so that the synthesized ferric phosphate has higher sulfur content, and the nanoscale ferric phosphate particles are difficult to prepare. Disclosure of Invention The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims. The invention aims to provide iron phosphate, a preparation method and application thereof, wherein the method can reduce the by-products wrapped in the growth process of crystal nucleus, and the prepared nano iron phosphate has stable composition of particle size, fine and uniform particles and low sulfur content, and the lithium iron phosphate anode material prepared from the iron phosphate can show excellent multiplying power performance and cycle performance. To achieve the purpose, the present disclosure adopts the following technical scheme: In a first aspect, the present disclosure provides a method of preparing iron phosphate, the method comprising the steps of: (1) Mixing ferrous salt, a phosphorus source and a solvent to obtain a mixed salt solution, and carrying out freezing treatment on the mixed salt solution to obtain a frozen mixed salt solution; (2) Placing the frozen mixed salt solution in a reflux device, controlling the hydrogen peroxide solution to reflux between the reflux device and a reaction device, and controlling the concentration of the hydrogen peroxide in the system to react until the frozen mixed salt solution is completely dissolved; (3) Adjusting pH in the system to perform an aging reaction, and carrying out solid-liquid separation to obtain the ferric phosphate. According to the method, the solution containing ferrous salt and a phosphorus source is frozen in advance, hydrogen peroxide is controlled to flow through the frozen mixed salt solution, and the reaction can be slowly carried out by controlling the concentration and the flow rate of the hydrogen peroxide, so that iron elements and phosphorus elements in the prepared ferric phosphate are uniformly distributed and the surface defects are few. In one embodiment, the ferrous salt of step (1) comprises any one or a combination of at least two of ferrous chloride, ferrous sulfate, or ferrous nitrate. In one embodiment, the phosphorus source of step (1) comprises any one or a combination of at least two of phosphoric acid, monoammonium phosphate, diammonium phosphate, or ammonium phosphate. In one embodiment, the concentration of the iron element in the mixed salt solution in the step (1) is 0.05-1 mol/L, for example, 0.05mol/L, 0.1mol/L, 0.3mol/L, 0.5mol/L, 1mol/L, or the like. In one embodiment, the concentration of the phosphorus element in the mixed salt solution in the step (1) is 0.5-1 mol/L, for example, 0.5mol/L, 0.6mol/L, 0.7mol/L, 0.8mol/L, 1mol/L or the like. In one embodiment, the pH of the mixed salt solution in the step (1) is 1.8-2.5, for