CN-122013292-A - Preparation method of blocky monocrystalline ferric phosphate

CN122013292ACN 122013292 ACN122013292 ACN 122013292ACN-122013292-A

Abstract

The invention relates to the technical field of battery materials, in particular to a preparation method of blocky monocrystalline ferric phosphate. The preparation method comprises the steps of (1) preparing a phosphoric acid solution, a hydrogen peroxide solution, ammonia water, a phosphorus salt solution and a ferrous salt solution, adding ammonia water into the phosphorus salt solution to obtain a phosphorus salt solution A, (2) uniformly mixing the hydrogen peroxide solution and the phosphorus salt solution A to obtain a phosphorus salt solution B, (3) feeding the ferrous salt solution and the phosphorus salt solution B together to obtain a slurry A, (4) filtering to obtain a filter cake, (5) pulping to obtain a slurry B, (6) dividing the slurry B into two parts, adding one part into a reaction kettle, adding the phosphoric acid solution, (7) heating, adding the other part of the slurry B, and preserving heat to obtain slurry, (8) obtaining ferric phosphate dihydrate, and (9) obtaining anhydrous ferric phosphate. The preparation method is compatible with the existing ammonium method process equipment, can realize batch production, and the prepared ferric phosphate is a blocky monocrystal, and meets the market product requirements in all specifications.

Inventors

Tan Shaosong
LI ZHI
PANG WEI
Huang Longcan
LIANG FUZHONG

Assignees

新洋丰农业科技股份有限公司

Dates

Publication Date: 20260512
Application Date: 20260415

Claims (10)

1. A method for preparing blocky monocrystalline ferric phosphate, which is characterized by comprising the following steps: (1) Preparing a phosphoric acid solution with the concentration of 40-85 wt%, a hydrogen peroxide solution with the concentration of 10-28 wt%, ammonia water with the concentration of 15-35 wt%, a phosphorus salt solution and a ferrous salt solution for standby; (2) Pouring the hydrogen peroxide solution and the phosphorus salt solution A into a mixing tank, and uniformly stirring to obtain a phosphorus salt solution B; (3) Adding pure water into a reaction kettle, heating to 20-60 ℃ under the condition that the stirring frequency is 30-180 Hz, adding the ferrite solution and the phosphonium salt solution B into the reaction kettle together within 30-90 min, and reacting for 30-60 min to obtain slurry A; (4) Performing solid-liquid separation on the slurry A, removing mother liquor to obtain a filter cake, and then adding hot pure water to wash the filter cake until the conductivity of washed washing water is reduced to below 5000 mu S/cm; (5) Transferring the filter cake into a slurrying tank, adding hot pure water, and stirring for 30-180 min to slurry to obtain slurry B; (6) Dividing the slurry B into two parts, wherein one part is reserved, and the other part is added into a reaction kettle and the phosphoric acid solution is added; (7) Heating to 80-98 ℃, after the color of the slurry is converted into white, adding another part of slurry B within 30-90 min, and preserving heat for 30-180 min after the addition is finished to obtain white slurry; (8) Performing solid-liquid separation on the white slurry, removing slurry liquid to obtain a ferric phosphate dihydrate filter cake, and then adding hot pure water to wash the filter cake until the conductivity of washing water after washing is reduced to below 500 mu S/cm; (9) And drying and calcining the filter cake to obtain the battery grade monocrystal anhydrous ferric phosphate.
2. The method for preparing bulk single crystal ferric phosphate according to claim 1, wherein in the step (1), the concentration of phosphorus element in the phosphorus salt solution A is 0.5-2.0 mol/L, and the phosphorus salt solution is at least one of monoammonium phosphate, ammonium phosphate, monosodium phosphate or sodium phosphate.
3. The method for preparing bulk single crystal ferric phosphate according to claim 1, wherein in the step (1), the concentration of iron element in the ferrite solution is 0.5-2.0 mol/L, and the ferrite solution is at least one of ferrous sulfate, ferrous nitrate, ferrous chloride, iron powder or iron scale.
4. The method for producing bulk single crystal iron phosphate according to claim 1, wherein in the step (2), the pH of the phosphorus salt solution a is 6 to 8.
5. The method for producing bulk single-crystal iron phosphate according to claim 1, wherein in the step (3), the molar ratio of the iron element in the ferrite solution to the phosphorus element in the phosphorus salt solution B is 1 (0.9 to 1.2).
6. The method for producing bulk single crystal iron phosphate according to claim 1, wherein in the step (3), the pH value in the reaction system is 1 to 4.
7. The method for producing bulk single crystal ferric phosphate according to claim 1, wherein in the step (4) and the step (8), the solid-liquid separation method is any one of centrifugation, press filtration and filtration.
8. The method for producing bulk single crystal ferric phosphate according to claim 1, wherein in the step (5), the solid content of the slurry is 8% -20%.
9. The method for preparing bulk single-crystal ferric phosphate according to claim 1, wherein in the step (6), the slurry B is divided into two parts, the ratio of the parts added into the reaction kettle to the spare parts is (1:9) - (7:3), and the molar ratio of phosphoric acid to iron in the reaction system is (0.1-0.8): 1.
10. The method for producing bulk single crystal iron phosphate according to claim 1, wherein the temperature of the hot pure water in the steps (4), (5) and (8) is 40 to 90 ℃.

Description

Preparation method of blocky monocrystalline ferric phosphate Technical Field The invention relates to the technical field of battery materials, in particular to a preparation method of blocky monocrystalline ferric phosphate. Background With the high-speed development of the current new energy industry, the lithium iron phosphate battery is widely applied to the fields of power batteries, energy storage batteries and the like by virtue of the advantages of high safety, long cycle life and the like, and the energy density requirements of the market are continuously improved. The compaction density of the lithium iron phosphate material is improved, so that the method is an effective technical path for improving the energy density of the lithium iron phosphate battery, and the multi-stage grain composition technology of the lithium iron phosphate material is one of the main technical means for realizing the high compaction density of the material. The ferric phosphate is used as a precursor for synthesizing the lithium iron phosphate, and the quality indexes such as chemical purity, particle morphology, particle size distribution and the like of the ferric phosphate material are directly determined to directly determine the microstructure and physical and chemical properties of the lithium iron phosphate material, so that the energy density and electrochemical properties of the lithium iron phosphate battery are decisively influenced. In the prior art, two kinds of ferric phosphate with different shapes and different particle size distribution are generally adopted as composite precursors to prepare the lithium iron phosphate material with the size particle grading, so as to optimize the compaction density and the electrochemical performance of the material. The scheme for preparing large-particle monocrystalline ferric phosphate in the prior art mainly comprises the following three steps of 1, mixing ferric salt and phosphorus salt to obtain an iron-dissolving solution, oxidizing and ageing at a certain temperature to prepare monocrystalline ferric phosphate, 2, respectively mixing the oxidized ferric salt, the phosphorus salt and phosphoric acid, and reacting at a low temperature under a certain pH condition to obtain monocrystalline ferric phosphate, 3, firstly preparing ferrous phosphate as an intermediate product, and then adding phosphoric acid and hydrogen peroxide for oxidation reaction to prepare monocrystalline ferric phosphate. The specific related technical scheme is briefly described as follows: the patent CN119776967A prepares a solution of iron by mixing purified chemical fertilizer acid with phosphoric acid, adds an iron source into the solution of iron, oxidizes at a certain temperature, and then heats to a certain temperature for aging for a period of time to obtain single crystal ferric phosphate. The patent CN115506006B is prepared by sequentially adding an iron source, hydrogen peroxide and 1, 2-propylene glycol into phosphoric acid, reacting at normal temperature for 10-30 min, reacting at 70-100 ℃ for 3-6 h, and standing and aging to obtain the single-crystal ferric phosphate. In the patent CN118814272B, an oxidant is added into a ferrous solution, the ferrous content is controlled to be 1% -5%, phosphorus salt and phosphoric acid are sequentially added to adjust the pH value, and the single-crystal ferric phosphate is obtained through reaction at 50-60 ℃. The patent CN119100346A prepares ferric phosphate as intermediate, filters, washes and pulps, adds mixed solution of phosphoric acid and hydrogen peroxide, heats and transforms to prepare monocrystal ferric phosphate. However, the technical scheme has two major problems that firstly, the phosphorus salt solution iron method of the patent CN119776967A and the phosphorus salt solution iron method of the patent CN115506006B are obviously different from the main ammonium method process in the market, are not compatible with the existing equipment and cannot be directly utilized, the production floor cost is increased, and the single crystal iron phosphate prepared by the one-step method of the patent CN118814272B and the ferrous phosphate intermediate method of the patent CN119100346A has the condition that the impurity content exceeds the market specification requirement. Disclosure of Invention Aiming at the technical problems that the existing single crystal ferric phosphate preparation method is not matched with the existing equipment and the content of partial impurities exceeds the market specification requirement, the invention provides the preparation method of the blocky single crystal ferric phosphate, which is based on the mainstream ammonium method process, and the prepared products have all specifications meeting the market product requirement. The technical scheme of the invention is as follows: the invention provides a preparation method of massive monocrystal ferric phosphate, which comprises the following steps: (1) Prep