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CN-122010072-A - Method for preparing iron phosphate dihydrate containing orthorhombic crystal form by ammonium method and preparation method of anhydrous iron phosphate

CN122010072ACN 122010072 ACN122010072 ACN 122010072ACN-122010072-A

Abstract

The invention belongs to the field of chemical technology, and in particular relates to a method for preparing iron phosphate dihydrate containing orthorhombic crystal form by an ammonium method and a method for preparing anhydrous iron phosphate. The method comprises the following steps of a) adding monoammonium phosphate solution into ferrous sulfate solution, then adjusting the pH value of a system to 1.25-1.6 by sulfuric acid to obtain mixed slurry, wherein in the step a), the molar ratio of P in the monoammonium phosphate solution to Fe in the ferrous sulfate solution is (2-2.25): 1, b) adding hydrogen peroxide into the mixed slurry to perform oxidation treatment to obtain oxidized slurry, C) heating the oxidized slurry to 90-95 ℃, aging for 2-8 h, filtering, washing and drying to obtain the ferric phosphate dihydrate containing orthorhombic crystal forms. The method provided by the invention can prepare and obtain the iron phosphate dihydrate containing the orthorhombic crystal form, and has the advantages of simple process and good economy.

Inventors

  • Liao Fuxia
  • LI MAOGANG
  • JIAN HANG
  • SHI LONG
  • LONG HUI
  • JU RONGMEI
  • CHEN XIN

Assignees

  • 贵州川恒化工股份有限公司

Dates

Publication Date
20260512
Application Date
20260227

Claims (10)

  1. 1. The method for preparing the iron phosphate dihydrate containing the orthorhombic crystal form by using the ammonium method is characterized by comprising the following steps of: a) Adding monoammonium phosphate solution into ferrous sulfate solution, and then regulating the pH value of the system to 1.25-1.6 by sulfuric acid to obtain mixed slurry; in the step a), the molar ratio of P in the monoammonium phosphate solution to Fe in the ferrous sulfate solution is (2-2.25): 1; b) Adding hydrogen peroxide into the mixed slurry for oxidation treatment to obtain oxidized slurry; c) And heating the oxidized slurry to 90-95 ℃, aging for 2-8 hours, filtering, washing and drying to obtain the ferric phosphate dihydrate containing the orthorhombic crystal form.
  2. 2. The method according to claim 1, wherein in step a), the concentration of the monoammonium phosphate solution is 0.8-1.2 mol/L.
  3. 3. The method according to claim 1, wherein in step a), the ferrous sulfate solution has a Fe 2+ content of 5-8 wt%.
  4. 4. The method according to claim 1, wherein in step a), the temperature of the ferrous sulfate solution is 30-40 ℃.
  5. 5. The method according to claim 1, wherein in the step b), the molar ratio of Fe 2+ in the mixed slurry to H 2 O 2 in the hydrogen peroxide is 2 (1.1-1.3).
  6. 6. The method according to claim 1, wherein in step b), the temperature of the oxidation treatment is 30-40 ℃.
  7. 7. The method according to claim 1, wherein in the step b), the time of the oxidation treatment is 60 to 70min.
  8. 8. The preparation method of the anhydrous ferric phosphate is characterized by comprising the following steps: preparing ferric phosphate dihydrate according to the method of any one of claims 1-7; calcining the ferric phosphate dihydrate to obtain anhydrous ferric phosphate.
  9. 9. The method according to claim 8, wherein the calcination temperature is 550 to 620 ℃.
  10. 10. The method according to claim 8, wherein the calcination time is 2 to 4 hours.

Description

Method for preparing iron phosphate dihydrate containing orthorhombic crystal form by ammonium method and preparation method of anhydrous iron phosphate Technical Field The invention belongs to the field of chemical technology, and in particular relates to a method for preparing iron phosphate dihydrate containing orthorhombic crystal form by an ammonium method and a method for preparing anhydrous iron phosphate. Background The lithium iron phosphate has the advantages of high heat stability, no cobalt and low cost (the cost of raw materials is only 50% of that of ternary materials) and longer than 3000 times of cycle life by virtue of the olivine structure, and the permeability of the lithium iron phosphate in the fields of power batteries (especially energy storage type electric vehicles) and large energy storage is continuously increased. However, the actual mass energy density (about 140-160 wh/kg) corresponding to the theoretical specific capacity (170 mAh/g) is difficult to meet the upgrading requirements of the new energy automobile on the basis of 1200 km of continuous voyage breakthrough and the energy storage system of high capacity and small volume, and becomes a core bottleneck for limiting the high-end market share. Numerous studies have demonstrated that the crystal structure and the microscopic morphology of ferric phosphate dihydrate directly determine the electrochemical performance of subsequent lithium iron phosphate. The ferric phosphate dihydrate (FePO 4·2H2 O) mainly comprises three crystal forms of an amorphous structure, a monoclinic structure and an orthogonal structure, wherein the amorphous crystal form is disordered due to crystal arrangement and has poor stability, the monoclinic crystal form has better stability than the amorphous crystal, but a lithium ion migration channel is locally blocked, the multiplying power performance is limited, and the orthogonal crystal form has more regular lattice arrangement and wider lithium ion diffusion channel, so that the electrochemical performance of the orthogonal crystal form is better. The traditional process for preparing the orthorhombic ferric phosphate dihydrate is mostly prepared by an iron powder route, and has high cost, long flow and poor economy. Disclosure of Invention In view of the above, the invention aims to provide a method for preparing iron phosphate dihydrate containing an orthorhombic crystal form by an ammonium method and a method for preparing anhydrous iron phosphate. The invention provides a method for preparing iron phosphate dihydrate containing orthorhombic crystal form by an ammonium method, which comprises the following steps: a) Adding monoammonium phosphate solution into ferrous sulfate solution, and then regulating the pH value of the system to 1.25-1.6 by sulfuric acid to obtain mixed slurry; in the step a), the molar ratio of P in the monoammonium phosphate solution to Fe in the ferrous sulfate solution is (2-2.25): 1; b) Adding hydrogen peroxide into the mixed slurry for oxidation treatment to obtain oxidized slurry; c) And heating the oxidized slurry to 90-95 ℃, aging for 2-8 hours, filtering, washing and drying to obtain the ferric phosphate dihydrate containing the orthorhombic crystal form. Preferably, in the step a), the concentration of the monoammonium phosphate solution is 0.8-1.2 mol/L. Preferably, in the step a), the content of Fe 2+ in the ferrous sulfate solution is 5-8wt%. Preferably, in the step a), the temperature of the ferrous sulfate solution is 30-40 ℃. Preferably, in the step b), the molar ratio of Fe 2+ in the mixed slurry to H 2O2 in the hydrogen peroxide is 2 (1.1-1.3). Preferably, in the step b), the temperature of the oxidation treatment is 30-40 ℃. Preferably, in the step b), the time of the oxidation treatment is 60-70 min. The invention provides a preparation method of anhydrous ferric phosphate, which comprises the following steps: preparing ferric phosphate dihydrate according to the method of the technical scheme; calcining the ferric phosphate dihydrate to obtain anhydrous ferric phosphate. Preferably, the calcination temperature is 550-620 ℃. Preferably, the calcination time is 2-4 hours. Compared with the prior art, the invention provides a method for preparing the iron phosphate dihydrate containing the orthorhombic crystal form by the ammonium method and a method for preparing the anhydrous iron phosphate. The method comprises the following steps of a) adding monoammonium phosphate solution into ferrous sulfate solution, then adjusting the pH value of a system to 1.25-1.6 by sulfuric acid to obtain mixed slurry, wherein in the step a), the molar ratio of P in the monoammonium phosphate solution to Fe in the ferrous sulfate solution is (2-2.25): 1, b) adding hydrogen peroxide into the mixed slurry to perform oxidation treatment to obtain oxidized slurry, C) heating the oxidized slurry to 90-95 ℃, aging for 2-8 h, filtering, washing and drying to obtain the ferric phos