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CN-121757834-B - Gas-phase doped lithium iron phosphate and preparation method thereof

CN121757834BCN 121757834 BCN121757834 BCN 121757834BCN-121757834-B

Abstract

The invention discloses gas-phase doped lithium iron phosphate and a preparation method thereof, which belong to the technical field of lithium iron phosphate anode materials, and comprise the following steps of S1, dispersing ferric phosphate, a lithium source and a morphology control agent in water to obtain precursor slurry, and carrying out spray drying on the precursor slurry to obtain precursor powder; S2, under the protection of inert gas, performing three-stage sintering on precursor powder, wherein the first-stage sintering is performed at 500-650 ℃, the second-stage sintering is performed at 400-600 ℃ and is performed by introducing M source gas, and the M source is doped through gas phase, and the third-stage sintering is performed by performing heat preservation at 300-400 ℃ and introducing carbon source gas, and coating the carbon source through gas phase. According to the invention, through the optimization of the gas phase doping morphology and the three-section gas phase doping-carbon cladding sintering process which are directionally constructed by the monodisperse polymer microspheres, the technical problems of uneven doping and poor morphology controllability of the traditional lithium iron phosphate are solved, and the improvement of the electrochemical performance of the anode material is realized.

Inventors

  • LI QIFENG
  • WANG LONG
  • CHEN LIPENG
  • CHEN ZHIXIN
  • HOU JUNKE
  • LONG BIAO
  • CHEN PENGJIE

Assignees

  • 福安国隆纳米材料有限公司

Dates

Publication Date
20260512
Application Date
20260228

Claims (7)

  1. 1. The preparation method of the gas-phase doped lithium iron phosphate is characterized by comprising the following steps of: S1, dispersing ferric phosphate, a lithium source and a morphology control agent in water to obtain precursor slurry with the solid content of 8% -25%, and performing spray drying on the precursor slurry to obtain precursor powder, wherein the morphology control agent is polymethyl methacrylate microspheres or polystyrene microspheres, and the adding proportion of the morphology control agent is 1.5% -6% of that of the precursor slurry; s2, under the protection of inert gas, performing three-stage sintering on the precursor powder; the first-stage sintering is carried out at 500-650 ℃; The second stage of sintering is to keep the temperature at 400-600 ℃ and introduce M source gas, and dope M source gas through gas phase, wherein the M source gas is titanium tetrachloride; the third sintering is to keep the temperature at 350-400 ℃ and introduce carbon source gas, and coat the carbon source by gas phase, wherein the carbon source gas is acetylene.
  2. 2. The method for preparing gas-phase doped lithium iron phosphate according to claim 1, wherein the lithium source is one or more of lithium carbonate, lithium hydroxide, and lithium acetate; and/or mixing the lithium source and the ferric phosphate according to the molar ratio of Li/Fe of 0.98-1.1/1.
  3. 3. The method for preparing gas-phase doped lithium iron phosphate according to claim 1, wherein the pH of the precursor slurry is controlled to be 3.5-6.0.
  4. 4. The method for preparing gas-phase doped lithium iron phosphate according to claim 1, wherein the inlet temperature of spray drying is controlled to be 180-250 ℃ and the outlet temperature is controlled to be 80-110 ℃.
  5. 5. The method for preparing gas-phase doped lithium iron phosphate according to claim 1, wherein the heat preservation temperature of the first-stage sintering is 550-600 ℃; and/or the heat preservation time of the first section sintering is 2-8 hours; And/or the temperature rising rate in the three-stage sintering process is controlled to be 2-5 ℃ per minute.
  6. 6. The method for preparing gas-phase doped lithium iron phosphate according to claim 1, wherein the volume ratio of the M source gas to the carrier gas is 1:5-1:20, and the flow rate of the carrier gas is 50 mL/min-200 mL/min; And/or the heat preservation temperature of the second-stage sintering is 400-550 ℃; And/or the heat preservation time of the second-stage sintering is 0.5-3 h.
  7. 7. The method for preparing gas-phase doped lithium iron phosphate according to claim 1, wherein the volume ratio of the carbon source gas to the carrier gas is 1:5-1:20, and the flow rate of the carrier gas is 50 mL/min-200 mL/min; and/or the heat preservation time of the third sintering is 0.5-3 h.

Description

Gas-phase doped lithium iron phosphate and preparation method thereof Technical Field The invention belongs to the technical field of lithium iron phosphate anode materials, and particularly relates to gas-phase doped lithium iron phosphate and a preparation method thereof. Background Lithium iron phosphate (LiFePO 4) has become a core choice of a positive electrode material of a lithium ion battery due to the advantages of high safety, long cycle life, low cost and the like, and is widely applied to the fields of new energy automobiles, energy storage power stations and the like. Along with the continuous improvement of requirements of terminal application on battery energy density, multiplying power performance and mass production stability, the existing lithium iron phosphate preparation process gradually exposes a plurality of defects to be solved urgently. The existing doping mode of lithium iron phosphate mainly comprises solid phase doping, and common preparation methods comprise a solid phase method, a hydrothermal method, a sol-gel method and the like. The solid phase method has the advantages that the process is simple, the cost is low, the doping process depends on mechanical mixing, the doping elements are distributed discretely due to uneven mixing of raw materials, metal ions are easy to agglomerate to form a local enrichment region, uniform doping of a lattice layer cannot be achieved, more lattice defects of a product are caused, the ion transmission efficiency is limited, the multiplying power performance is difficult to meet the requirement of a high-power scene, meanwhile, the accurate cooperative regulation and control of a doping structure and morphology are difficult to achieve by the traditional solid phase method, the tap density and the doping uniformity of the product are mutually restricted, and the electrode compacting effect and the ion diffusion rate are influenced. Although the hydrothermal method and the sol-gel method can improve the dispersibility of the product to a certain extent, the method has the defects of harsh reaction conditions, high mass production difficulty and high cost, the doping process still takes solid phase addition as a core, metal ions are easy to migrate and agglomerate in a reaction system, and lithium iron phosphate lattices are difficult to uniformly embed, so that the stability of the electrical property of the material is poor. In addition, the existing carbon coating process mostly adopts solid-phase carbon sources (such as sucrose and glucose), has the problems of uneven thickness of a carbon layer and easy falling, is not cooperated with an efficient doping process, cannot optimize the ion and electron conduction performance of the material at the same time, and is lack of a specific doping process cooperation in a part of gas-phase carbon coating technology, so that the structural advantage of the material is difficult to fully develop, and the further improvement of the electrochemical performance of lithium iron phosphate is limited. Disclosure of Invention The invention aims to overcome the technical problems, and therefore provides a gas-phase doped lithium iron phosphate and a preparation method thereof. The invention solves the technical problems through the following technical proposal. According to the invention, through the optimization of the gas phase doping morphology and the three-section gas phase doping-carbon cladding sintering process which are directionally constructed by the monodisperse polymer microspheres, the technical problems of uneven doping and poor morphology controllability of the traditional lithium iron phosphate are solved, and the improvement of the electrochemical performance of the anode material is realized. The invention discloses a preparation method of gas-phase doped lithium iron phosphate, which comprises the following steps: S1, dispersing ferric phosphate, a lithium source and a morphology control agent in water to obtain precursor slurry, and performing spray drying on the precursor slurry to obtain precursor powder, wherein the morphology control agent is polymethyl methacrylate microspheres or polystyrene microspheres; s2, under the protection of inert gas, performing three-stage sintering on the precursor powder; the first-stage sintering is carried out at 500-650 ℃; The second stage of sintering is to keep the temperature at 400-600 ℃ and introduce M source gas, and dope the M source gas through gas phase, wherein the M source gas is at least one of titanium tetrachloride, zirconium tetrachloride and magnesium acetylacetonate; And the third sintering is to keep the temperature at 200-400 ℃ and introduce carbon source gas, and cladding the carbon source through gas phase. According to some embodiments of the invention, the lithium source is one or more of lithium carbonate, lithium hydroxide, and lithium acetate, preferably lithium carbonate. According to some embodiments of the present invention