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CN-121983534-A - Lithium iron phosphate positive electrode material, preparation method and application thereof

CN121983534ACN 121983534 ACN121983534 ACN 121983534ACN-121983534-A

Abstract

The application discloses a lithium iron phosphate anode material, a preparation method and application thereof. The lithium iron phosphate positive electrode material comprises a lithium iron phosphate matrix (LFP) and a coating layer coated on the surface of the lithium iron phosphate matrix, wherein the coating layer contains polyaramid and carbon. The lithium iron phosphate anode material can improve the electrochemical performance of LFP at low temperature, and improve the low-temperature cycling stability and capacity retention rate of the battery.

Inventors

  • LI ZHENG
  • JIN XINKAI
  • GUO DEXIANG
  • WANG YANG
  • YU ZHEXUN
  • YU HONGJIANG

Assignees

  • 江苏正力新能电池技术股份有限公司

Dates

Publication Date
20260505
Application Date
20251224

Claims (10)

  1. 1. The lithium iron phosphate anode material is characterized by comprising a lithium iron phosphate matrix and a coating layer coated on the surface of the lithium iron phosphate matrix, wherein the coating layer contains polyaramid and carbon.
  2. 2. The lithium iron phosphate positive electrode material according to claim 1, wherein the carbon is a carbon quantum dot, and/or the polyaramid is poly-paraphenylene terephthalamide and/or poly-m-phenylene isophthalamide.
  3. 3. The lithium iron phosphate positive electrode material according to claim 1, wherein the particle size of the lithium iron phosphate matrix is in the range of 0.15-6 μm, and/or the thickness of the composite coating layer is 50-200 nm.
  4. 4. The lithium iron phosphate positive electrode material according to claim 2, wherein the weight of the polyaramid is 0.5-2.5 wt% of the weight of the lithium iron phosphate matrix, and/or the molecular weight of the polyaramid is 4000-6000.
  5. 5. The lithium iron phosphate positive electrode material of claim 2, wherein the weight of the carbon quantum dots is 0.5-2.5 wt% of the weight of the lithium iron phosphate matrix, and/or the particle size range of the carbon quantum dots is 5-20 nm.
  6. 6. A method for preparing the lithium iron phosphate positive electrode material according to any one of claims 1 to 5, which is characterized by comprising the following steps: preparing a lithium iron phosphate matrix; Uniformly dispersing the carbon quantum dots to form a dispersion liquid; adding the raw material A for synthesizing the polyaramide into the dispersion liquid to be dissolved, then adding the lithium iron phosphate matrix to form LFP dispersion liquid, adding the raw material B for synthesizing the polyaramide into the LFP dispersion liquid under low-temperature rapid stirring, and obtaining the lithium iron phosphate anode material after in-situ polymerization reaction.
  7. 7. The method for preparing a lithium iron phosphate positive electrode material according to claim 6, wherein the preparation of the lithium iron phosphate matrix is specifically performed by mixing an iron source, a lithium source and a phosphorus source, ball milling, drying and then performing heat treatment to obtain the lithium iron phosphate matrix.
  8. 8. The method for preparing a lithium iron phosphate positive electrode material according to claim 6, wherein at least one of the following conditions is satisfied: (1) The raw material A of the polyaramid is p-phenylenediamine and/or m-phenylenediamine, and the raw material B of the polyaramid is at least one of terephthaloyl chloride, m-phthaloyl chloride, trimesoyl chloride and oxalyl chloride; (2) The temperature of the low-temperature rapid stirring is-20 ℃ to 0 ℃, the stirring speed is 100-300 rap/min, and the time of the in-situ polymerization reaction is 10-18 h; (3) The preparation method further comprises the step of heating the obtained lithium iron phosphate positive electrode material to 300-500 ℃ at a temperature of 2-5 ℃ per minute under the protection of inert gas, and preserving heat for 2-4 hours.
  9. 9. A positive electrode sheet characterized by comprising the lithium iron phosphate positive electrode material according to any one of claims 1 to 5, and/or A lithium iron phosphate positive electrode material produced by the production method according to any one of claims 6 to 8.
  10. 10. A lithium ion battery is characterized by comprising the positive electrode plate of claim 9.

Description

Lithium iron phosphate positive electrode material, preparation method and application thereof Technical Field The application relates to the technical field of lithium ion batteries, in particular to a lithium iron phosphate positive electrode material, and preparation and application thereof. Background Lithium iron phosphate (LiFePO 4, LFP) has become one of the most important positive electrode materials in the fields of power cells and energy storage cells because of its high safety, long cycle life, low cost, and the like. However, its intrinsically low electron conductivity (10 -9 S/cm) and slow lithium ion diffusion rate (10 -¹4~10-¹6 cm 2/S) result in extremely poor low temperature performance. Below 0 ℃, the discharge capacity thereof decays sharply, and the capacity retention rate is generally lower than 60% at-20 ℃, severely limiting the application thereof in cold regions. Currently, conventional methods for improving LFP low temperature performance include (1) carbon coating, which is the most common modification method, to increase electron conductance by coating the surface of LFP particles with an amorphous carbon layer. However, the carbon layer produced by pyrolysis of conventional carbon sources (such as glucose and sucrose) has high disorder degree and many lattice defects, the improvement of ion conduction capacity is limited, and the interface resistance between the carbon layer and the electrolyte is still larger at low temperature. (2) nanocrystallization of particles, shortening the lithium ion diffusion path. However, the nanoparticles are easy to agglomerate, the tap density is low, and side reactions with electrolyte are increased, so that the processing is difficult and the circulation stability is reduced. (3) Ion doping, namely expanding a lithium ion diffusion channel through doping elements such as Mg2 +、Ti4+ and the like. However, the process is complicated to control, and impurity phases may be introduced, sacrificing part of the specific capacity. Disclosure of Invention The invention aims to provide a lithium iron phosphate positive electrode material, a preparation method and application thereof, and the lithium iron phosphate positive electrode material can improve the electrochemical performance of LFP at low temperature and improve the low-temperature cycling stability and capacity retention rate of a battery. In order to achieve the purpose of the invention, the following technical scheme is adopted: In one aspect, the invention provides a lithium iron phosphate positive electrode material, which comprises a lithium iron phosphate matrix and a coating layer coated on the surface of the lithium iron phosphate matrix, wherein the coating layer contains polyaramid and carbon. In an embodiment of the present invention, the carbon is a carbon quantum dot. In an embodiment of the invention, the polyaramid is poly (paraphenylene terephthalamide) and/or poly (m-phenylene isophthalamide). Preferably, the polyaramid is poly (paraphenylene terephthalamide). In the embodiment of the invention, the particle size of the lithium iron phosphate matrix is in the range of 0.15-6 mu m. In the embodiment of the invention, the thickness of the composite coating layer is 50-200 nm. Preferably, the weight of the polyaramid accounts for 0.5-2.5 wt% of the weight of the lithium iron phosphate matrix. Preferably, the molecular weight of the polyaramid is 4000-6000. Preferably, the weight of the carbon quantum dots accounts for 0.5-2.5 wt% of the weight of the lithium iron phosphate matrix. Preferably, the particle size range of the carbon quantum dots is 5-20 nm. On the other hand, the invention also provides a preparation method of the lithium iron phosphate anode material, which comprises the following steps: preparing a lithium iron phosphate matrix; Uniformly dispersing the carbon quantum dots to form a dispersion liquid; adding the raw material A for synthesizing the polyaramide into the dispersion liquid to be dissolved, then adding the lithium iron phosphate matrix to form LFP dispersion liquid, adding the raw material B for synthesizing the polyaramide into the LFP dispersion liquid under low-temperature rapid stirring, and obtaining the lithium iron phosphate anode material after in-situ polymerization reaction. In the embodiment of the invention, the preparation of the lithium iron phosphate matrix is specifically carried out by mixing an iron source, a lithium source and a phosphorus source, ball milling, drying and then carrying out heat treatment to obtain the lithium iron phosphate matrix. Preferably, the iron source includes at least one of iron phosphate, ferrous oxalate, iron nitrate, iron oxide red, ferroferric oxide, and ultrafine iron powder. Preferably, the lithium source comprises at least one of lithium carbonate, lithium dihydrogen phosphate, lithium hydroxide, lithium chloride, and lithium nitrate. Preferably, the phosphorus source comprises at least one of ferric p