CN-121990538-A - Method for preparing nano-particle ferric phosphate dihydrate

Abstract

The application discloses a method for preparing nano-particle ferric phosphate dihydrate, which uses water to dilute ferric phosphate complex solution, reduces the concentration to 10% or lower, and carries out solid-liquid separation to obtain the nano-particle ferric phosphate dihydrate. The nanometer irregular ferric phosphate dihydrate particles are obtained by the preparation method, and the nanometer irregular ferric phosphate dihydrate particles are further dehydrated at high temperature to form the ferric phosphate nano particles with crystal configuration. The method reduces the crystal aging process in the existing ferric phosphate dihydrate preparation process and greatly reduces the energy consumption. In addition, the nano-particle ferric phosphate is mixed with the large-particle-size ferric phosphate particles, so that gaps among the particles can be reduced in the high-compaction process, and the preparation of the high-compaction lithium iron phosphate can be realized. The preparation method has simple and controllable reaction conditions and can realize industrialized application.

Inventors

• MA XIAOLING
• DONG BIBO
• CHEN YAO

Assignees

• 黄冈林立新能源科技有限公司

Dates

Publication Date

20260508

Application Date

20241107

Claims (10)

1. 1. A process for preparing nano-particle ferric phosphate dihydrate, which is characterized in that the ferric phosphate complex solution is diluted by water, the concentration is reduced to 10 percent or less, preferably to 10 to 0.5 percent, the solid-liquid separation is carried out, so as to obtain the nano-particle ferric phosphate dihydrate, The phosphorus-iron ratio in the ferric phosphate complex solution is 2-10, preferably 3.75-6, and the concentration of phosphorus element in the complex solution is more than 2mol/L, preferably 2.5mol/L-14.6mol/L.
2. 2. The method of claim 1, wherein the dilution method comprises adding the complexing liquid to water or adding water to the complexing liquid.
3. 3. The method according to claim 1 or 2, wherein the volume ratio of water to complexing liquid is (12-120): 1, preferably the volume ratio of water to complexing liquid is (16-50): 1.
4. 4. A method according to any one of claims 1-3, wherein the dilution is performed at 0 ℃ to 90 ℃, preferably at 20-85 ℃.
5. 5. The method of any one of claims 1-4, wherein the diluted solution precipitates and the ferric phosphate dihydrate nanoparticles are obtained by solid-liquid separation.
6. 6. The method of claim 5, wherein the mother liquor after solid-liquid separation is recycled to partially replace the dilution water.
7. 7. A method of preparing nanoparticulate ferric phosphate, the method comprising: S1, preparing ferric phosphate complex liquid; S2, diluting the ferric phosphate complex solution to 10% or less of the original concentration by using water, and carrying out solid-liquid separation to obtain ferric phosphate dihydrate nano particles; S3, dehydrating the ferric phosphate dihydrate nano particles at a high temperature to obtain the ferric phosphate of the nano particles.
8. 8. The method of claim 7, wherein the iron phosphate complex solution is prepared by a process selected from the group consisting of reacting iron powder with phosphoric acid, oxidizing ferrous ions to ferric ions with an oxidizing agent to form an iron phosphate complex solution, reacting ferric oxide with phosphoric acid to form an iron phosphate complex solution, and reacting ferric oxide with phosphoric acid to oxidize ferrous ions to ferric ions with an oxidizing agent to form an iron phosphate complex solution.
9. 9. A method according to claim 7 or 8, wherein the high temperature dehydration temperature is 400-1000 ℃, preferably 500-800 ℃.
10. 10. The method of any one of claims 1-9, wherein the amorphous iron phosphate dihydrate nanoparticles are converted to anhydrous iron phosphate nanoparticles in a crystalline configuration after dehydration at high temperature.

Description

Method for preparing nano-particle ferric phosphate dihydrate Technical Field The invention belongs to the technical field of inorganic materials and lithium battery materials, and particularly relates to a preparation method of a precursor material ferric phosphate of a lithium ion battery. Background Lithium ion battery materials develop rapidly, especially lithium iron phosphate and ternary materials. Based on the requirement for the energy density improvement of the lithium iron phosphate battery, the compaction density of the lithium iron phosphate can be increased as one of ways for increasing the energy density of the lithium iron phosphate battery. The iron phosphate serving as a raw material for preparing the lithium iron phosphate has direct influence on the compaction density of the lithium iron phosphate, and the energy density of the lithium iron phosphate battery pack can be finally improved by preparing the high-purity high-compaction iron phosphate. The main methods for preparing the high-compaction ferric phosphate products at present are as follows: CN115215313A generates an amorphous ferrous phosphate octahydrate reaction precursor in situ in a first mixture system by controlling synthesis conditions, controls the dissolution rate of the amorphous ferrous phosphate octahydrate reaction precursor by controlling the pH of a second slurry, further regulates and controls the concentration of phosphate radical and ferrous ion in a reaction system, and then realizes the accurate regulation and control of the supersaturation degree of iron ion and phosphate radical ion in the reaction system by adding oxidizing substances. The method for preparing high-compaction ferric phosphate from industrial monoammonium phosphate and ferrous sulfate provided by CN116534820B adopts a reaction route of firstly oxidizing and then double decomposing, firstly using hydrogen peroxide to completely oxidize a refined ferrous sulfate solution, then slowly adding monoammonium phosphate, and enabling the initial iron element concentration of the reaction solution to be high, so that a small amount of added monoammonium phosphate and high-concentration iron ions can quickly react to form small-particle ferric phosphate, and in the subsequent reaction, the small-particle ferric phosphate is taken as a core to aggregate and grow, so that the reaction is thorough. CN111533103a is a preparation method of high-compaction ferric phosphate, the method firstly prepares ferric hydroxide colloid, then reacts with ammonium bicarbonate and phosphoric acid to obtain filter residues, the washed filter residues are added into sucrose solution, and the obtained slurry is spray dried. Calcining the spray-dried material to obtain the high-compaction ferric phosphate. Adding high-compaction ferric phosphate into an organic carbon source, lithium carbonate, a dispersing agent, graphite and water, mixing and grinding until the particle size of the material is 150-250nm to obtain grinding slurry, and calcining twice to obtain the high-compaction lithium iron phosphate. CN111377426B is a preparation method of anhydrous iron phosphate nano-particle, and the patent obtains a micron secondary structure formed by agglomeration of nano-particle, and the iron phosphate material is not nano primary particle. From the above patents or patent applications, the preparation of iron phosphate with nanoparticles or micrometer aggregates with nano primary particles is one of the important routes to the preparation of highly compacted lithium iron phosphate, but there is a lack of a simple, low cost industrial application method to obtain nanoscale iron phosphate particles. Disclosure of Invention The application aims to provide a preparation method of a random nanoparticle ferric phosphate dihydrate material. The inventors of the present application considered that the compacted density of lithium iron phosphate particles prepared by using nanoscale iron phosphate as a seed crystal is high, or that the compacted density of lithium iron phosphate material can be improved by mixing nanoparticles with large-sized iron phosphate material. The invention provides a method for preparing nano-particle ferric phosphate dihydrate, which comprises the steps of diluting ferric phosphate complex solution with water, reducing the concentration to 10% or less, preferably reducing the concentration to 10% -0.5%, and carrying out solid-liquid separation to obtain the nano-particle ferric phosphate dihydrate. And dehydrating the ferric phosphate dihydrate of the nano particles at high temperature to obtain the ferric phosphate of the nano particles. The high temperature dehydration temperature is 400-1000 ℃, preferably 500-800 ℃. The phosphorus-iron ratio in the ferric phosphate complex solution is 2-10, preferably 3.75-6, and the concentration of phosphorus element in the complex solution is more than 2mol/L, preferably 2.5mol/L-14.6mol/L. The phosphorus element (P) inclu