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CN-116768183-B - Ferric phosphate precursor and preparation method thereof, lithium iron phosphate material and preparation method thereof

CN116768183BCN 116768183 BCN116768183 BCN 116768183BCN-116768183-B

Abstract

The invention provides an iron phosphate precursor, a preparation method thereof, a lithium iron phosphate material and a preparation method thereof, wherein the iron phosphate precursor enables transition metal-containing iron phosphate to be deposited on a fibrous polyhydroxy carbon material template in situ through the action of hydrogen bonds, and the lithium source is added and then calcined, so that the lithium iron phosphate anode material with a porous structure can be obtained. In the preparation process, the fibrous polyhydroxy-containing carbon material is excessive and serves as a reducing agent and a conductive agent to coat the inner wall and the outer wall of the material. The lithium iron phosphate material has stronger liquid retention, not only increases the conductivity of the material, but also improves the multiplying power performance, and the porous inner part has a certain supporting function, so that the shape is not easily damaged in the compaction process.

Inventors

  • ZHAO XIAOLIAN
  • WANG CHENGLONG
  • XU JIAN
  • LI SHIWEN

Assignees

  • 高点(深圳)科技有限公司

Dates

Publication Date
20260505
Application Date
20230727

Claims (9)

  1. 1. A method for preparing lithium iron phosphate by using fibrous iron phosphate precursor containing polyhydroxy carbon material is characterized by comprising the following steps of mixing a carbon source, a lithium source and fibrous iron phosphate precursor containing polyhydroxy carbon material in a liquid phase according to a ratio of (0.005-0.05) (1.0-1.05), drying the mixture after uniform mixing, and sintering at a high temperature under the protection of inert gas to obtain the lithium iron phosphate material with a porous structure; the preparation method of the ferric phosphate precursor of the fibrous polyhydroxy carbon-containing material comprises the following steps: (1) Uniformly dispersing the fibrous polyhydroxy-containing carbon material in the solution under continuous stirring to obtain solution A; (2) Adding an iron source and a complexing agent into the solution A obtained in the step (1), continuously stirring, and then adding a phosphorus source to enable the solution to contain iron ions and phosphate ions to obtain a solution B; (3) Adding a surfactant into the solution B obtained in the step (2), uniformly stirring, adjusting the pH value, and reacting to obtain a product; (4) Aging, press-filtering, washing and drying the product obtained in the step (3) to obtain a fibrous ferric phosphate precursor containing polyhydroxy carbon materials; the mass of the fibrous polyhydroxy-containing carbon material is 0.1-5% of the mass of the ferric phosphate precursor of the fibrous polyhydroxy-containing carbon material; The fibrous polyhydroxy carbon-containing material comprises at least one of polyhydroxy polyvinyl resin, polyhydroxy epoxy resin, polyhydroxy polypropylene-based resin, polyhydroxy phenolic resin, polyvinyl alcohol acrylonitrile copolymer, polyvinyl alcohol and polyvinyl alcohol pyrrolidone copolymer; The chemical structural formula of the ferric phosphate precursor of the fibrous polyhydroxy carbon-containing material is as follows: Wherein x is more than or equal to 0 and less than or equal to 1,100000 and less than 10000000, M is a transition metal element, and the transition metal element comprises at least one of Mn, ni, V, cu.
  2. 2. The method for preparing lithium iron phosphate according to claim 1, wherein the fibrous polyhydroxyl carbon containing material has a diameter of 0.1 to 5 μm and a length of 2 to 50 μm.
  3. 3. The method of preparing lithium iron phosphate according to claim 1, wherein the fibrous polyhydroxyl carbon containing material has a carbon content of 30-80%, a hydroxyl content of 30-50% and a carboxyl content of 10-20%.
  4. 4. The method for preparing lithium iron phosphate according to claim 1, wherein the iron source is at least one of ferric sulfate, ferric acetate, ferric chloride and ferric nitrate, the phosphorus source is at least one of ammonium phosphate, monoammonium phosphate, phosphoric acid, sodium phosphate, sodium monohydrogen phosphate and sodium dihydrogen phosphate, the complexing agent is at least one of oxalic acid, citric acid, tartaric acid, gluconic acid and diethanolamine, and the surfactant is at least one of fatty acid polyoxyethylene ester, alkylphenol polyoxyethylene ether, alkyl alcohol amide and sucrose fatty acid ester.
  5. 5. The method for preparing lithium iron phosphate according to claim 1, wherein the molar ratio of phosphate to iron ions in the solution B is 1.05-1.10:1, and the carbon content in the iron phosphate precursor of the fibrous polyhydroxy carbon containing material is 0.1-3%.
  6. 6. The method for preparing lithium iron phosphate according to claim 1, wherein in the step (3), the reaction temperature is 60-90 ℃, the ph=1.0-5.0, and the reaction time is 3-5h.
  7. 7. The method for preparing lithium iron phosphate according to claim 1, wherein the carbon source is at least one of glucose, sucrose, starch, cellulose, phenolic resin, and carbon black, the lithium source is at least one of lithium carbonate, lithium hydroxide, lithium acetate, and lithium sulfate, and the inert gas is at least one of nitrogen, argon, helium, neon, and xenon.
  8. 8. The method for preparing lithium iron phosphate according to claim 1, wherein the high temperature sintering temperature is 550-850 ℃.
  9. 9. A lithium iron phosphate material, characterized in that the material is prepared by the method for preparing lithium iron phosphate according to any one of claims 1 to 8.

Description

Ferric phosphate precursor and preparation method thereof, lithium iron phosphate material and preparation method thereof Technical Field The invention relates to the technical field of lithium ion batteries, and discloses an iron phosphate precursor and a preparation method thereof, and an iron phosphate lithium material and a preparation method thereof. Background In recent years, with the rapid development of the lithium ion battery industry, particularly the lithium iron phosphate material in the power battery industry, has higher capacity, low raw material price and good stability and cycle performance. However, due to the limitation of the structure, the electron conductivity and the ion conductivity are lower, so that the conductivity and the ion mobility of the material are poorer, and the improvement of the electrochemical performance of the material is greatly influenced. The current-stage solution to the above problems is mainly element doping, coating, nanoparticle preparation and the like. Patent CN1785799a discloses a preparation method of transition metal doped lithium iron phosphate powder, namely mixing ferrous salt and phosphate of lithium salt with elements such as Mn, co, ni and the like according to a proportion, drying, presintering at low temperature and secondary calcining at high temperature to obtain transition element doped lithium iron phosphate powder. The transition metal is doped by the traditional solid-phase sintering method, so that the migration rate and conductivity of ions are improved, and the capacity and the cycle electrical performance of the battery are improved. However, the effect of improving the conductivity of lithium iron phosphate materials by metal doping alone is limited and does not improve the conductivity of the materials to a greater extent. Chinese patent CN 110510593A discloses a preparation method of ferric phosphate precursor and lithium iron phosphate, wherein ferric phosphate suspension is obtained by adding ferric source and phosphoric acid under a certain pH and temperature, using complexing agent and surfactant, ageing, press filtering, washing and drying to obtain ferric phosphate dihydrate precursor, adding lithium source and carbon source, calcining, and obtaining lithium iron phosphate anode material. However, after the precursor is prepared by the material obtained by the method, the carbon source is added for calcination, and the carbon source is only coated on the outer side of the material, so that the conductivity and the rate capability are lower. Chinese patent CN 113540455A discloses a hollow carbon coated lithium iron phosphate particle and a preparation method thereof, as long as the hollow Li 3PO4 particle is prepared, an iron source and a phosphorus source are added, and the hollow lithium iron phosphate precursor is converted into the hollow lithium iron phosphate, and the hollow lithium iron phosphate precursor is mixed with a reducing carbon source and sintered in a protective atmosphere, so as to obtain the hollow spherical carbon coated lithium iron phosphate. However, the lithium iron phosphate manufactured by the method is only of a hollow structure, the dispersibility problem of materials and coated carbon is not solved, the compaction of the hollow structure is low, and the morphology is not easy to maintain in the process of preparing the battery. Chinese patent CN 107507975A discloses a preparation method of carbon-coated lithium iron phosphate nano hollow spheres, which comprises the steps of mixing polyethylene glycol 600 with deionized water, mixing the mixture with phosphoric acid and lithium hydroxide monohydrate to react to obtain a lithium phosphate precursor, mixing the precursor with ethylene glycol and ferrous chloride tetrahydrate, carrying out ultrasonic treatment, carrying out heating reaction in a high-pressure reaction kettle to obtain lithium iron phosphate nano hollow spheres, adding a carbon source, calcining under a protective atmosphere, and taking the precursor shape as a template to obtain the carbon-coated lithium iron phosphate nano hollow spheres. Although the preparation process can solve the problems of conductivity and multiplying power performance, the preparation process is complex, is not beneficial to industrial production, and increases the preparation cost by using organic solvents such as ethylene glycol and the like and a reaction kettle. In view of the above-mentioned drawbacks of the current lithium iron phosphate materials, it is necessary to provide a solution to the above-mentioned problems. Disclosure of Invention The invention aims to provide an iron phosphate precursor, which is characterized in that transition metal-containing iron phosphate is in-situ deposited on a fibrous polyhydroxy carbon material template through the action of hydrogen bonds, and is calcined after a lithium source is added, so that a lithium iron phosphate anode material with a porous structure can be