CN-117999243-B - Lithium iron phosphate positive electrode material, preparation method thereof and lithium ion battery

CN117999243BCN 117999243 BCN117999243 BCN 117999243BCN-117999243-B

Abstract

The application provides a lithium iron phosphate anode material, a preparation method thereof and a lithium ion battery, wherein the preparation method comprises the following steps of (1) preparing an iron hydroxymethyl acid salt two-dimensional precursor; mixing the two-dimensional precursor of the iron hydroxymethyl acid salt with a nitrogen-containing carbon source for reaction to obtain a two-dimensional precursor material, and mixing the two-dimensional precursor material, a lithium source and a phosphorus source for sintering to obtain the lithium iron phosphate anode material. The lithium iron phosphate anode material is prepared by a simple process and simple operation, has a larger electrode/electrolyte contact interface, is favorable for complete infiltration of electrolyte and the anode material, and has a microstructure inheriting the two-dimensional sheet morphology of the iron hydroxymethyl acid salt precursor, the large specific surface area of the anode material provides sufficient active sites for storage of lithium ions and electrons, rapid diffusion and transmission of the lithium ions are promoted, and the electrochemical performance of a lithium ion battery is improved.

Inventors

YU HAIJUN
LI CHANGDONG
LI AIXIA
WANG TAO
XIE YINGHAO

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: 20231229

Claims (13)

1. The preparation method of the lithium iron phosphate positive electrode material comprises the following steps: (1) Preparing a two-dimensional precursor of iron hydroxymethyl acid salt; (2) Mixing the iron hydroxymethyl acid salt two-dimensional precursor with a nitrogen-containing carbon source, and reacting to obtain a two-dimensional precursor material; (3) Mixing the two-dimensional precursor material, a lithium source and a phosphorus source, and sintering to obtain the lithium iron phosphate anode material; The preparation method of the two-dimensional precursor of the iron hydroxymethylate in the step (1) comprises the following steps: mixing ferrous acetate tetrahydrate and an alcohol solvent, and performing solvothermal reaction to obtain the iron hydroxymethyl acid salt two-dimensional precursor; The nitrogen-containing carbon source in the step (2) comprises dopamine hydrochloride; The mass concentration of the dopamine hydrochloride in the solution obtained by mixing in the step (2) is 0.5-0.8g/L; the molar ratio of the two-dimensional precursor material, the phosphorus source and the lithium source in the step (3) is 1 (0.98-1.05): 1; The sintering mode in the step (3) is multi-stage sintering, wherein the multi-stage sintering comprises primary sintering and secondary sintering; The temperature of the primary sintering is 400-550 ℃ and the time is 2-5h; the temperature of the secondary sintering is 650-750 ℃ and the time is 6-10h.
2. The method according to claim 1, wherein the concentration of the solution obtained by mixing the ferrous acetate tetrahydrate and the alcohol solvent is (0.17-0.5) mol/L.
3. The method according to claim 1, wherein the solvothermal reaction is carried out at a temperature of 150-200 ℃ for a period of 24-36 hours.
4. The method of claim 1, wherein the mixing in step (2) comprises: dispersing the two-dimensional precursor of the iron hydroxymethylate in a buffer solution, and then adding a nitrogen-containing carbon source for blending.
5. The method of claim 4, wherein the buffer solution comprises Tris buffer solution.
6. The method of claim 1, wherein the temperature of the mixing in step (2) is room temperature for a period of 12 to 24 hours.
7. The method of claim 1, wherein the means of mixing in step (3) comprises ball milling.
8. The method of claim 1, wherein the sintering in step (3) is performed in a protective atmosphere.
9. The preparation method according to claim 1, characterized in that it comprises the following steps: (1) Mixing ferrous acetate tetrahydrate and an alcohol solvent with dissolved oxygen removed, carrying out solvothermal reaction at 150-200 ℃ for 24-36h, cooling to room temperature after the reaction is finished, and then centrifuging and washing to obtain the iron hydroxymethylate two-dimensional precursor; Wherein, the concentration of the solution obtained by mixing ferrous acetate tetrahydrate and an alcohol solvent is (0.17-0.5) mol/L; (2) Ultrasonically dispersing the iron hydroxymethyl acid salt two-dimensional precursor in a buffer solution, adding dopamine hydrochloride, stirring and mixing, reacting at room temperature for 12-24 hours, and centrifuging and washing after the reaction is finished to obtain a two-dimensional precursor material, namely Fe (OH) (OCH 3 ) @ polydopamine material; Wherein the mass concentration of dopamine hydrochloride in the mixed solution is 0.5-0.8g/L; (3) In a protective atmosphere, carrying out ball milling and mixing on the two-dimensional precursor material, a phosphorus source and a lithium source according to the molar ratio of 1 (0.98-1.05) to 1 for 2-5 hours, and obtaining the lithium iron phosphate anode material after drying, primary sintering and secondary sintering; Wherein the temperature of the primary sintering is 400-550 ℃, the time is 2-5h, the temperature of the secondary sintering is 650-750 ℃ and the time is 6-10h.
10. The lithium iron phosphate positive electrode material prepared by the preparation method according to any one of claims 1 to 9, wherein the lithium iron phosphate positive electrode material comprises a LiFePO 4 inner core and a nitrogen-doped carbon layer coated on the surface of the LiFePO 4 inner core; The LiFePO 4 inner core is of a two-dimensional lamellar porous structure.
11. The lithium iron phosphate positive electrode material according to claim 10, wherein the LiFePO 4 core has a porosity of 26-32% and an average pore size of 8.3-11.5nm.
12. The lithium iron phosphate positive electrode material according to claim 10, wherein the thickness of the nitrogen-doped carbon layer is 5.5-6.7nm.
13. A lithium ion battery, wherein the positive electrode of the lithium ion battery comprises the lithium iron phosphate positive electrode material according to any one of claims 10 to 12.

Description

Lithium iron phosphate positive electrode material, preparation method thereof and lithium ion battery Technical Field The application relates to the technical field of battery materials, in particular to a lithium iron phosphate positive electrode material, a preparation method thereof and a lithium ion battery. Background As the market demand for portable electronic devices and electric vehicles continues to expand, rechargeable lithium ion batteries have been receiving attention because of their high energy density, long relative life, and environmental friendliness. The lithium iron phosphate (LiFePO 4) serving as the positive electrode material of the lithium ion battery has the advantages of low price, safety, environmental protection, high capacity, stable circulation and the like, and becomes one of the first choice of the power battery. However, due to the structural limitation, liFePO 4 has the disadvantages of low electron conductivity, low diffusion rate of lithium ions at the two-phase interface of FePO 4/LiFePO4, low tap density and the like, which limits the application of the LiFePO 4 in the scenes of large-scale energy storage, high-rate power batteries and the like. In order to solve the problem, the means such as particle surface coating modification, ion doping, morphology regulation and nanocrystallization are used for modifying lithium iron phosphate, so that the electrochemical properties of the material are improved. The material with the two-dimensional flaky morphology structure can provide rich electrochemical active sites due to the characteristics of large specific surface area and ultrathin lamellar thickness, so that the removal/intercalation channel of lithium ions can be well shortened, the migration range of the material is enlarged, and the multiplying power and low temperature resistance of the lithium ion battery are improved. If the structure is introduced into the design of the lithium iron phosphate anode material, the method has great significance for improving the comprehensive electrical performance of the battery. In addition, the related preparation methods of lithium iron phosphate such as a solid phase method, a liquid phase method and a sol-gel method have the defects of incomplete reaction, irregular crystallization, complex and harsh process and high energy consumption, and the electrical property of the prepared lithium iron phosphate is also a certain difference from the theoretical capacity and needs to be further improved. Therefore, a method with simple process and simple and convenient operation is developed to prepare the novel lithium iron phosphate anode material with excellent performance parameters, and the method has important significance for improving the overall electrochemical performance of the lithium ion battery. Disclosure of Invention The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims. The application aims to provide a lithium iron phosphate positive electrode material, a preparation method thereof and a lithium ion battery. The application prepares the lithium iron phosphate anode material coated by the nitrogen doped carbon layer with a two-dimensional porous structure by a method with simple process and easy operation, the anode material has a larger electrode/electrolyte contact interface, which is beneficial to complete infiltration of electrolyte and anode material, and the microstructure of the anode material inherits the two-dimensional flaky shape of the iron hydroxymethyl acid salt precursor, and the large specific surface area provides sufficient active sites for lithium ions and electrons to store, thereby promoting rapid diffusion and transmission of lithium ions and being beneficial to improving the electrochemical performance of a lithium ion battery. The preparation method has good industrial application prospect. In order to achieve the purpose of the application, the application adopts the following technical scheme: In a first aspect, the present application provides a method for preparing a lithium iron phosphate positive electrode material, the method comprising the steps of: (1) Preparing a two-dimensional precursor of iron hydroxymethyl acid salt; (2) Mixing the iron hydroxymethyl acid salt two-dimensional precursor with a nitrogen-containing carbon source, and reacting to obtain a two-dimensional precursor material; (3) And mixing the two-dimensional precursor material, a lithium source and a phosphorus source, and sintering to obtain the lithium iron phosphate anode material. According to the application, the surface of the two-dimensional iron hydroxymethyl acid salt precursor sheet is coated with a nitrogen-containing carbon layer, after being mixed with a lithium source and a phosphorus source, organic groups Fe (OH) (OCH 3) in the two-dimensional precursor material are pyrolyzed, and a porous structure is formed on the two