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CN-117602603-B - Nanometer ferric phosphate and preparation method thereof, nanometer lithium ferric phosphate positive electrode material and preparation method and application thereof

CN117602603BCN 117602603 BCN117602603 BCN 117602603BCN-117602603-B

Abstract

The invention discloses a nano ferric phosphate and a preparation method thereof, a nano lithium iron phosphate positive electrode material and a preparation method and application thereof, belonging to the technical field of lithium battery materials, and the preparation method of the nano ferric phosphate provided by the invention comprises the following steps: and preparing first precursor slurry from an iron source and a phosphorus source by adopting a coprecipitation method, adding a surfactant, adding a precipitant under the condition of stirring and heating to control the pH value to obtain second precursor slurry, and performing aftertreatment on the second precursor slurry to obtain the nano ferric phosphate. And adding a surfactant into the first precursor slurry obtained by the coprecipitation reaction, so that the generation of large particles can be inhibited in the growth stage of ferric phosphate crystal grains, and then the stable and uniform growth of the crystal grains is controlled, so that the nano ferric phosphate is obtained. The nano ferric phosphate, the lithium source and the carbon source are mixed and sintered to obtain the nano ferric phosphate lithium anode material, and experiments prove that the nano ferric phosphate is converted into the nano ferric phosphate lithium, and the morphology and the volume corresponding to the nano ferric phosphate lithium are not changed excessively.

Inventors

  • XIA YUXIN
  • KONG LINGYONG
  • WAN YUANXIN
  • WANG PENG
  • FENG ZE
  • YE FENG

Assignees

  • 佛山市德方纳米科技有限公司

Dates

Publication Date
20260512
Application Date
20231124

Claims (20)

  1. 1. A preparation method of nano iron phosphate comprises the steps of adjusting the pH value of a mixed solution of an iron source and a phosphorus source to 1-2, performing coprecipitation reaction with an oxidant, performing burst nucleation in the solution to obtain first precursor slurry, performing coprecipitation reaction at 80-90 ℃ for 1-3 hours, then uniformly mixing the first precursor slurry with a surfactant, adding a precipitant under the condition of stirring and heating to keep the pH value of the reaction at 1-2, obtaining second precursor slurry after the reaction is finished, wherein the content of the surfactant in the second precursor slurry is 0.2-1 g/500ml, the stirring rotation speed is 400-700 rpm, the heating temperature is 80-90 ℃, and performing aging, washing and calcining treatment on the second precursor slurry to obtain nano iron phosphate, wherein the surfactant comprises at least one of citric acid, polyethylene glycol, cetyltrimethylammonium bromide and sodium hexadecyl benzene sulfonate, and the particle size of the nano iron phosphate is spherical or spherical, and the particle size of the nano iron phosphate is 50-150 nm.
  2. 2. The preparation method of the first precursor slurry according to claim 1, wherein the preparation of the first precursor slurry comprises the steps of mixing an iron source solution and a phosphorus source solution to obtain a mixed solution, adjusting the pH of the mixed solution to 1-2, and then adding an excessive oxidant solution to perform coprecipitation reaction to obtain the first precursor slurry.
  3. 3. The preparation method of claim 2, wherein the iron source comprises at least one of ferrous sulfate and iron powder, the phosphorus source comprises at least one of phosphoric acid, ammonium phosphate and ammonium dihydrogen phosphate, the concentration of the iron source solution is 1-3 mol/L, and the concentration of the phosphorus source solution is 1-3 mol/L.
  4. 4. The preparation method according to claim 2, wherein the pH of the mixed solution is adjusted to 1-2 by using a sulfuric acid solution, and the concentration of the sulfuric acid solution is 1-3 mol/L.
  5. 5. The preparation method according to claim 2, wherein the oxidant is hydrogen peroxide, the molar ratio of the iron source to the hydrogen peroxide is 1 (0.55-0.75), and the concentration of the oxidant solution is 1-4 mol/L.
  6. 6. The preparation method of the second precursor slurry according to claim 1, wherein the preparation of the second precursor slurry comprises the steps of uniformly mixing the first precursor slurry with the surfactant, dropwise adding the precipitant step by step under the condition of stirring and heating, and controlling the pH of the reaction to be 1-2, so as to obtain the second precursor slurry.
  7. 7. The method of preparing according to claim 6, wherein the surfactant comprises at least one of citric acid, polyethylene glycol, cetyltrimethylammonium bromide and sodium hexadecyl benzene sulfonate.
  8. 8. The method of claim 7, wherein the surfactant is citric acid.
  9. 9. The preparation method according to claim 6, wherein the precipitant comprises at least one of sodium hydroxide solution and ammonia water, and the concentration of the precipitant is 1-4 mol/L.
  10. 10. The preparation method according to claim 6, wherein the total dripping time of the precipitant is controlled to be 20-40 min, and the pH of the final solution is 1-2 after the dripping of the precipitant is completed.
  11. 11. The preparation method of the nano ferric phosphate according to claim 1, wherein the preparation method comprises the steps of adding a phosphoric acid solution into the second precursor slurry for aging and crystallization after filtering and washing, filtering and washing again, and calcining to obtain the nano ferric phosphate.
  12. 12. The method according to claim 11, wherein the stirring speed is 300 to 700rpm, the heating temperature is 80 to 90 ℃ and the aging time is 2 to 4 hours during the aging crystallization.
  13. 13. The method according to claim 11, wherein the concentration of the phosphoric acid solution is 1 to 3mol/L.
  14. 14. The method according to claim 11, wherein the calcination temperature is 550 to 650 ℃ and the time is 4 to 6 hours.
  15. 15. The preparation method of the nano lithium iron phosphate anode material is characterized by comprising the step of mixing and sintering nano iron phosphate, a lithium source and a carbon source in an inert gas atmosphere to obtain the nano lithium iron phosphate anode material, wherein the nano iron phosphate is prepared by the preparation method according to any one of claims 1-14.
  16. 16. The preparation method of claim 15, wherein the nano-iron phosphate, the lithium source and the carbon source are mixed and ground to obtain a nano-lithium iron phosphate precursor, and the nano-lithium iron phosphate precursor is sintered and cooled to obtain the nano-lithium iron phosphate anode material.
  17. 17. The preparation method of the nano lithium iron phosphate precursor according to claim 16, wherein the nano lithium iron phosphate precursor is obtained by mixing nano lithium iron phosphate, a lithium source and a carbon source in a molar ratio of (2-2.5): (1-1.50): (0.2-0.4) and then ball milling for 4-6 hours at a rotating speed of 200-400 rpm.
  18. 18. The method of claim 16, wherein the carbon source comprises at least one of glucose, sucrose, and polyacrylate.
  19. 19. The method of claim 16, wherein the sintering comprises a first stage sintering in which the temperature is increased from room temperature to a first sintering temperature at a first rate of increase for a first period of time, a second stage sintering in which the temperature is increased from the first sintering temperature to a second sintering temperature at a second rate of increase for a second period of time, and a third stage sintering in which the temperature is increased from the second sintering temperature to a third sintering temperature at a third rate of increase for a third period of time.
  20. 20. The method according to claim 19, wherein the first sintering temperature is 30-50 ℃, the first sintering time period is 1-2 hours, the second sintering temperature is 550-600 ℃, the second sintering time period is 3-4 hours, the third sintering temperature is 700-750 ℃, and the third sintering time period is 7-10 hours.

Description

Nanometer ferric phosphate and preparation method thereof, nanometer lithium ferric phosphate positive electrode material and preparation method and application thereof Technical Field The invention relates to the technical field of lithium battery materials, in particular to a nano ferric phosphate and a preparation method thereof, a nano ferric phosphate lithium positive electrode material and a preparation method and application thereof. Background The lithium iron phosphate is an important positive electrode material of a lithium ion battery, and has the advantages of high structural stability, good safety performance, moderate working voltage, good platform characteristic, large theoretical capacity and the like, however, the existing lithium iron phosphate has the problems of uneven particles, large granularity, small specific surface area and the like. This results in a fabricated battery with low volumetric specific capacity and poor electrochemical performance. Disclosure of Invention The invention aims to overcome the defects in the prior art and provide a nano ferric phosphate and a preparation method thereof, a nano lithium iron phosphate positive electrode material and a preparation method and application thereof. The invention solves the technical problems by adopting the following technical scheme. The invention provides a preparation method of nano ferric phosphate, which comprises the steps of preparing a first precursor slurry from an iron source and a phosphorus source by adopting a coprecipitation method, adding a surfactant, adding a precipitant under the condition of stirring and heating to control the pH value to obtain a second precursor slurry, and carrying out post-treatment on the second precursor slurry to obtain the nano ferric phosphate, wherein the surfactant comprises at least one of citric acid, polyethylene glycol, cetyltrimethylammonium bromide and sodium hexadecyl benzenesulfonate. The invention also provides the nano iron phosphate prepared by the preparation method, wherein the primary particle size of the nano iron phosphate is 50-150 nm, and the morphology of the nano iron phosphate is spherical or spheroid. The invention also provides a preparation method of the nano lithium iron phosphate anode material, which comprises the step of mixing and sintering the prepared nano lithium iron phosphate, lithium source and carbon source in an inert gas atmosphere to obtain the nano lithium iron phosphate anode material. The invention also provides the nano lithium iron phosphate anode material prepared by the preparation method, wherein the primary particle size of the nano lithium iron phosphate anode material is 150-250 nm, and the morphology of the nano lithium iron phosphate anode material is spherical or spheroid. The invention also provides a lithium ion battery, which comprises the nano lithium iron phosphate anode material. The invention has the following beneficial effects: The invention provides a nano ferric phosphate and a preparation method thereof, a nano lithium iron phosphate positive electrode material and a preparation method and application thereof, and the preparation method of the nano ferric phosphate comprises the following steps: preparing first precursor slurry by adopting an iron source and a phosphorus source through a coprecipitation method, adding a surfactant, adding a precipitator under the condition of stirring and heating to control the pH value to obtain second precursor slurry, and performing aftertreatment on the second precursor slurry to obtain nano ferric phosphate, wherein the surfactant comprises at least one of citric acid, polyethylene glycol, cetyltrimethylammonium bromide and sodium hexadecyl benzenesulfonate. In the preparation process of the nano ferric phosphate, a coprecipitation method is firstly adopted to prepare and form a first precursor slurry, and then a surfactant is added, so that on one hand, the surfactant can inhibit the growth of crystal nucleus of a precipitation product to obtain more uniform nano ferric phosphate particles, and on the other hand, in the process of preparing the nano ferric phosphate lithium anode material by mixing and sintering nano ferric phosphate, a lithium source and a carbon source, the surfactant can also be used as a part of carbon source to be distributed in the nano ferric phosphate lithium anode material, and the conductivity and the ion conductivity of the finished nano ferric phosphate lithium anode material are improved. The method is unique and effective in preparation, and the prepared nano lithium iron phosphate positive electrode material is uniform in appearance, fine in particles, spherical or spheroidic, good in conductivity and high in stability. Drawings In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the followin