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CN-118324111-B - Phosphate positive electrode material, preparation method thereof and lithium ion battery

CN118324111BCN 118324111 BCN118324111 BCN 118324111BCN-118324111-B

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a phosphate positive electrode material, a preparation method thereof and a lithium ion battery. The preparation method comprises the steps of dispersing a primary semi-finished product of a phosphate positive electrode material in a solvent, adding an etchant to etch the particle surface of the primary semi-finished product to obtain a secondary semi-finished product, wherein the particle surface crystallinity of the primary semi-finished product is lower than the particle internal crystallinity, mixing the secondary semi-finished product with each raw material of the added phosphate positive electrode material, and then performing secondary sintering to obtain a finished product of the phosphate positive electrode material, wherein the raw materials comprise an organic iron source, and the use amount of the etchant is 1.2-8 wt% of the primary semi-finished product. The phosphate positive electrode material prepared by the preparation method not only obviously improves the mass transfer problem of a lithium interface, but also improves the electronic conductivity, thereby effectively improving the cycle stability of the phosphate positive electrode material.

Inventors

  • TANG JIE
  • WANG PENG
  • KONG LINGYONG
  • FENG ZE
  • Li Boqiao
  • YE FENG
  • HANG JING
  • Rao Yinan
  • Li yineng

Assignees

  • 深圳市德方纳米科技股份有限公司

Dates

Publication Date
20260512
Application Date
20240410

Claims (11)

  1. 1. The preparation method of the phosphate positive electrode material is characterized by comprising the following steps: Dispersing a primary semi-finished product of a phosphate positive electrode material in a solvent, and adding an etchant to etch the particle surfaces of the primary semi-finished product to obtain a secondary semi-finished product, wherein the particle surface crystallinity of the primary semi-finished product is lower than the particle internal crystallinity; mixing the secondary semi-finished product with the raw materials of the added phosphate positive electrode material, and then performing secondary sintering to obtain a finished product of the phosphate positive electrode material, wherein the raw materials of the added phosphate positive electrode material comprise a lithium source, a phosphorus source and an organic iron source, and the organic iron source comprises at least one of ferrocene, ferrocene derivatives, ferrous protoporphyrin and ferrous protoporphyrin derivatives; The consumption of the etchant is 1.2-8wt% of the primary semi-finished product, and the etchant comprises hydrofluoric acid; Heating a precursor of the phosphate positive electrode material to 320-380 ℃ at a heating rate of 0.1-0.5 ℃ per minute for primary sintering to obtain a primary semi-finished product, wherein the raw materials of the primary semi-finished product of the phosphate positive electrode material comprise a lithium source, a phosphorus source and an iron source; The temperature of the secondary sintering is 700-780 ℃.
  2. 2. The method for producing a phosphate-based positive electrode material according to claim 1, wherein the amount of hydrofluoric acid is 3 to 6wt% of the primary semi-finished product in terms of HF.
  3. 3. The method for producing a phosphate-based positive electrode material according to claim 2, wherein the fluorine content of the particle surface in the finished product of the phosphate-based positive electrode material is 0.5 to 3wt% based on the mass of lithium manganese iron phosphate.
  4. 4. The method for producing a phosphate-based positive electrode material according to claim 1, wherein the heat-retaining time for the secondary sintering is 4 to 8 hours.
  5. 5. The method for preparing a phosphate-based cathode material according to claim 1, wherein the secondary sintering comprises heating to 700-780 ℃ at a heating rate of 5-10 ℃/min, maintaining for 4-8 hours, and cooling to room temperature at 1-3 ℃/min.
  6. 6. The method for producing a phosphate-based positive electrode material according to claim 1, wherein the solid content of the system is 60% -80% after the primary semi-finished product is dispersed in a solvent.
  7. 7. The method of producing a phosphate-based positive electrode material according to claim 1, wherein the precursor of the phosphate-based positive electrode material further comprises a doping element including at least one of Ti, mg, V, co, in, ni, zr and Nb.
  8. 8. The method for producing a phosphate-based positive electrode material according to claim 7, wherein the doping element source is used in an amount of 0.5wt% to 3wt% based on the mass of the final product.
  9. 9. The method for producing a phosphate-based positive electrode material according to claim 1, wherein the raw material of the additional phosphate-based positive electrode material further comprises a manganese source.
  10. 10. The phosphate positive electrode material according to any one of claims 1 to 9.
  11. 11. A lithium ion battery comprising the phosphate-based positive electrode material produced by the production method of the phosphate-based positive electrode material according to any one of claims 1 to 9 or the phosphate-based positive electrode material according to claim 10.

Description

Phosphate positive electrode material, preparation method thereof and lithium ion battery Technical Field The invention relates to the technical field of lithium ion batteries, in particular to a phosphate positive electrode material, a preparation method thereof and a lithium ion battery. Background At present, phosphate positive electrode materials (such as lithium iron phosphate or lithium manganese iron phosphate) are favored in the market due to the advantages of high safety, good cycle performance, rich raw material sources, small environmental pollution and the like. However, with the development of the battery field, the market has set higher requirements on the positive electrode material of the lithium ion battery, and the development and application of the phosphate positive electrode material have problems. Taking lithium manganese phosphate as an example, the main problems of the lithium manganese phosphate are defects of poor lithium ion conductivity, poor electron conductivity and the like, and the problems greatly limit the large-scale application of the lithium manganese phosphate. In order to solve the above problems, the most commonly used technical optimization directions at present include particle refinement, element doping, carbon coating and the like, but the implementation of the three technical optimization directions is often required to be completed independently from each other and one step after another, which not only reduces the production efficiency, but also has limited effect of improving the electrochemical performance of phosphate systems. In view of this, the present invention has been made. Disclosure of Invention The invention aims to provide a preparation method of a phosphate positive electrode material, the phosphate positive electrode material prepared by the method and a lithium ion battery containing the phosphate positive electrode material. In order to achieve the above object, the present invention provides a method for preparing a phosphate-based positive electrode material, comprising the steps of: Dispersing a primary semi-finished product of a phosphate positive electrode material in a solvent, and adding an etchant to etch the particle surfaces of the primary semi-finished product to obtain a secondary semi-finished product, wherein the particle surface crystallinity of the primary semi-finished product is lower than the particle internal crystallinity; Mixing the secondary semi-finished product with each raw material of the added phosphate positive electrode material, and then performing secondary sintering to obtain a finished product of the phosphate positive electrode material, wherein the raw materials comprise an organic iron source; the using amount of the etching agent is 1.2-8 wt% of the primary semi-finished product. Further, the precursor of the phosphate-based positive electrode material is heated to 320-380 ℃ at a heating rate of 0.1-0.5 ℃ per minute for primary sintering, and the primary semi-finished product is obtained. Further, the etchant includes a fluorine-containing etchant. Further, the etchant includes hydrofluoric acid. Further, the dosage of the hydrofluoric acid is 3-6 wt% of the primary semi-finished product by using HF. Further, the fluorine content of the particle surface in the finished product of the phosphate positive electrode material is 0.5-3 wt% relative to the mass percentage of the lithium iron manganese phosphate. Further, the organic iron source includes iron and cyclic organic structures. Further, the organic iron source includes at least one of ferrocene, ferrocene derivatives, ferroprotoporphyrin, and ferroprotoporphyrin derivatives. Further, the temperature of the secondary sintering is 700-780 ℃, and the heat preservation time of the secondary sintering is 4-8 hours. Further, the secondary sintering comprises the steps of heating to 700-780 ℃ at a heating rate of 5-10 ℃ per minute, preserving heat for 4-8 hours, and cooling to room temperature at 1-3 ℃ per minute. Further, after the primary semi-finished product is dispersed in a solvent, the solid content of the system is 60% -80%. Further, the precursor of the phosphate-based cathode material further includes a doping element including at least one of Ti, mg, V, co, in, ni, zr and Nb. Further, the dosage of the doping element source is 0.5-3 wt% of the mass of the finished product. Further, the raw materials of the additional phosphate-based cathode material include a lithium source, a phosphorus source, and an iron source. Further, the raw material of the additional phosphate-based cathode material further includes a manganese source. In another aspect, the invention provides a phosphate positive electrode material prepared by any one of the preparation methods. In yet another aspect, the present invention provides a lithium ion battery comprising any one of the above-described phosphate-based cathode materials. Compared with the prior art, the invention ha