CN-118851118-B - Iron phosphate composite material and preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium ion battery materials, and particularly relates to an iron phosphate composite material, a preparation method and application thereof. The preparation method comprises the steps of (1) uniformly mixing ferric salt, two-dimensional titanium carbide multilayer nano sheets and nitrogen carbon quantum dots, obtaining a flower-ball-shaped frame precursor material through hydrothermal reaction, (2) mixing the flower-ball-shaped frame precursor material with a phosphorus source, adjusting pH value, obtaining a flower-ball-shaped hydrated ferric phosphate material through coprecipitation reaction, and (3) carrying out high-temperature sintering and acid treatment on the hydrated ferric phosphate material to obtain the ferric phosphate composite material. The construction of the three-dimensional flower-ball structure and the doping of the nitrogen-carbon quantum dots and a small amount of titanium element are beneficial to cooperatively promoting the rapid diffusion of lithium ions and electrolyte, and the specific capacity and the overall electrochemical performance of the lithium battery anode material are improved.

Inventors

• YU HAIJUN
• LI CHANGDONG
• XIE YINGHAO
• WANG TAO
• ZHANG XIAOLU

Assignees

• 广东邦普循环科技有限公司
• 湖南邦普循环科技有限公司

Dates

Publication Date

20260505

Application Date

20240628

Claims (13)

1. 1. The preparation method of the iron phosphate composite material is characterized by comprising the following steps of: (1) Mixing ferric salt, a two-dimensional titanium carbide multilayer nano sheet and nitrogen carbon quantum dots in water to obtain a suspension, and performing hydrothermal reaction to obtain a flower-sphere-shaped frame precursor material; (2) Dispersing the flower-sphere-shaped frame precursor material into water and mixing the mixture with a phosphorus source to obtain a mixed solution, and performing coprecipitation reaction to obtain a flower-sphere-shaped hydrated ferric phosphate material; (3) Sintering the hydrated ferric phosphate material to obtain a titanium-doped anhydrous ferric phosphate material; (4) And (3) soaking the titanium-doped anhydrous ferric phosphate material in an acid solution to obtain the ferric phosphate composite material.
2. 2. The method of claim 1, wherein in the step (1), ferric salt and two-dimensional titanium carbide multilayer nano-sheets are dispersed in water to form a dispersion liquid, then nitrogen and carbon quantum dots are dispersed in water to obtain a nitrogen and carbon quantum dot dispersion liquid, and then the two dispersion liquids are mixed to obtain a suspension liquid.
3. 3. The preparation method according to claim 2, wherein the mass ratio of the trivalent ferric salt to the two-dimensional titanium carbide multilayer nano-sheet is 1 (1-1.5).
4. 4. The preparation method according to claim 2, wherein the mass concentration of the nitrogen-carbon quantum dot dispersion is 2mg/mL, and the solid-to-liquid ratio of the ferric salt to the nitrogen-carbon quantum dot dispersion is 1g (5-12 mL).
5. 5. The method according to claim 1, wherein the hydrothermal reaction is carried out at a temperature of 150 to 180 ℃ for a period of 5 to 8 hours.
6. 6. The method of claim 1, wherein one or more of the following features one to three are satisfied in the step (2): The first characteristic is that after mixing, the pH value of the mixed solution is adjusted to be 1.5-2.2 by adding ammonia water or sodium hydroxide solution; The temperature of the coprecipitation reaction is 80-90 ℃, and the time of the coprecipitation reaction is 6-8 hours; and thirdly, further aging treatment is carried out after the coprecipitation reaction is finished, wherein the aging treatment time is 3-5h.
7. 7. The method according to claim 1, wherein the sintering treatment in step (3) is performed at a temperature of 550 to 750 ℃ for a time of 4 to 6 hours; The sintering treatment atmosphere comprises oxygen-containing nitrogen, wherein the volume ratio of nitrogen in the oxygen-containing nitrogen is 95%, and the oxygen accounts for 4% -5%.
8. 8. The preparation method of claim 1, wherein the acid solution in the step (4) comprises hydrofluoric acid, the molar concentration of the hydrofluoric acid is 0.1-0.2mol/L, and the soaking time is 2-3 h.
9. 9. The method of claim 1, wherein the ferric salt comprises any one or a combination of at least two of ferric chloride, ferric sulfate, or ferric nitrate; the phosphorus source comprises any one or a combination of at least two of phosphoric acid, monoammonium phosphate or diammonium phosphate; the molar ratio of the iron element in the ferric salt to the phosphorus element in the phosphorus source is 1:1.
10. 10. The method of claim 1, wherein the iron phosphate composite material comprises titanium-doped iron phosphate and nitrogen-carbon quantum dots; The iron phosphate composite material has a three-dimensional flower-ball shape.
11. 11. The method of manufacturing according to claim 1, wherein the iron phosphate composite material meets one or more of the following features one to three: The specific surface area of the iron phosphate composite material is 7m 2 /g-10m 2 /g; the second characteristic is that the content of titanium element in the iron phosphate composite material is 5.0% -8.5%; And the average particle size of the nitrogen-carbon quantum dots is 5.5nm-9.0nm.
12. 12. The lithium iron phosphate positive electrode material is characterized by being prepared by mixing and sintering the lithium iron phosphate composite material, a lithium source and a carbon source according to the preparation method of any one of claims 1-11.
13. 13. A lithium ion battery comprising the lithium iron phosphate positive electrode material of claim 12.

Description

Iron phosphate composite material and preparation method and application thereof Technical Field The invention belongs to the technical field of battery materials, and particularly relates to an iron phosphate composite material, and a preparation method and application thereof. Background Lithium power batteries have been widely used in the field of electric automobiles as novel high-energy batteries, and the types mainly include ternary lithium batteries and lithium iron phosphate batteries. Compared with a ternary lithium battery, the olivine crystal-structured lithium iron phosphate battery has high safety, long cycle life, low price and environmental protection, and has become the most potential lithium battery anode material, however, the lithium ions can only diffuse in one-dimensional channels due to the structural characteristics, which results in low lithium ion diffusion rate and poor conductivity of the lithium iron phosphate material (LiFePO 4), and limits the further commercialized application of the anode material. Iron phosphate (FePO 4) is an important precursor for the preparation of lithium iron phosphate, and changes in its microstructure and chemical composition directly affect the properties of LiFePO 4 materials. In the process of improving the defects of the ferrophosphorus positive electrode material, although the carbon coating means can improve the conductivity of the material to some extent, it is difficult to solve the problem of poor conductivity essentially, and the specific capacity of the battery is also reduced. The conventional preparation methods such as coprecipitation and high temperature solid phase method have problems of serious agglomeration, large particle size and small specific surface area, which limits diffusion and transfer of lithium ions and affects the electrical properties of lithium batteries. Therefore, how to improve the conductivity of the lithium iron phosphate and reduce the influence on the specific capacity of the lithium iron phosphate becomes a technical problem to be solved urgently, and development of a simple and reliable modification method for preparing the ferric phosphate with stable physicochemical properties has important significance for obtaining the lithium iron phosphate anode material with excellent performance. Disclosure of Invention In view of the problems existing in the prior art, the invention aims to provide an iron phosphate composite material, a preparation method and application thereof, and aims to improve the specific capacity of a lithium iron phosphate positive electrode material and the overall electrochemical performance of a lithium battery. In order to achieve the aim of the invention, the invention adopts the following technical scheme: In a first aspect, the present invention provides an iron phosphate composite material, the iron phosphate composite material comprising titanium element doped iron phosphate and nitrogen carbon quantum dots; The iron phosphate composite material has a three-dimensional flower-ball shape. In an alternative embodiment, the specific surface area of the iron phosphate composite is 7m 2/g-10m2/g; In an alternative embodiment, the iron phosphate composite material has a titanium content of 5.0% to 8.5%. ; In an alternative embodiment, the average particle size of the nitrogen carbon quantum dots is 5.5nm to 9.0nm. In the iron phosphate composite material prepared by the invention, the construction of the three-dimensional flower-sphere structure, the doping of the nitrogen-carbon quantum dots and a small amount of titanium elements are beneficial to cooperatively promoting the rapid diffusion of lithium ions and electrolytes, improving the specific capacity of the lithium iron phosphate positive electrode material and improving the overall electrochemical performance of a lithium battery. In a second aspect, the present invention provides a method for preparing an iron phosphate composite material, the method comprising the steps of: (1) Mixing ferric salt, a two-dimensional titanium carbide multilayer nano sheet and nitrogen carbon quantum dots in water to obtain a suspension, and performing hydrothermal reaction to obtain a flower-sphere-shaped frame precursor material; (2) Dispersing the three-dimensional flower-sphere frame precursor material into water, mixing with a phosphorus source, and performing coprecipitation reaction to obtain flower-sphere hydrated ferric phosphate material; (3) Sintering the hydrated ferric phosphate material to obtain a titanium-doped anhydrous ferric phosphate material; (4) And (3) soaking the titanium-doped anhydrous ferric phosphate material in an acid solution to obtain the ferric phosphate composite material. The preparation method comprises the steps of preparing a two-dimensional titanium carbide (Ti 3C2Tx) multilayer nanosheet by taking titanium aluminum carbide (Ti 3AlC2) as a precursor through a chemical etching method, dissolving ferric salt i