CN-122010082-A - Preparation method of lithium iron phosphate, positive electrode plate and lithium ion battery

Abstract

The invention relates to the technical field of lithium ion batteries, and particularly provides a preparation method of lithium iron phosphate, a positive pole piece and a lithium ion battery. The preparation method of the lithium iron phosphate comprises the steps of providing Ti-MOF/polymer composite nanofiber, mixing the Ti-MOF/polymer composite nanofiber with a lithium source and a ferrophosphorus source to obtain a precursor mixture, and sintering the precursor mixture in an inert atmosphere. The method not only avoids great loss and dust pollution caused by directly using nano powder, but also can keep the characteristics of large specific surface area and high activity of the nano fiber, is beneficial to diffusing into the crystal at a low sintering temperature and improving the ionic conductivity of the LFP, and the calcined carbonized fiber skeleton can construct a conductive network to further improve the electronic conductivity of the LFP and is beneficial to reducing the use of the conductive agent in the positive electrode plate.

Inventors

• GAO JIFAN
• PEI ZHEN
• LI QINGLING
• LU LIN
• JIANG ZHIYI

Assignees

• 江苏天合储能有限公司

Dates

Publication Date

20260512

Application Date

20260410

Claims (16)

1. 1. The preparation method of the lithium iron phosphate is characterized by comprising the following steps: Providing a Ti-MOF/polymer composite nanofiber; Mixing Ti-MOF/polymer composite nanofiber with a lithium source and a ferrophosphorus source to obtain a precursor mixture; Sintering the precursor mixture in an inert atmosphere to obtain the catalyst.
2. 2. The method for preparing lithium iron phosphate according to claim 1, wherein the Ti-MOF/polymer composite nanofiber is used in an amount of 0.2-2% of the total mass of the lithium source and the ferrophosphorus source.
3. 3. The method for producing lithium iron phosphate according to claim 2, wherein the ratio of the lithium source to the ferrophosphorus source is 1.01-1.08:1 in terms of the molar ratio of Li element to Fe element.
4. 4. The method for producing lithium iron phosphate according to claim 1, wherein the sintering temperature is 650-750 ℃.
5. 5. The method of preparing lithium iron phosphate according to claim 1, wherein the Ti-MOF/polymer composite nanofiber is provided by the following method: Providing a spin dope comprising carboxylic acid aromatic hydrocarbons and a polymer; Spinning the spinning solution to prepare composite nano fibers; mixing the composite nanofiber with an organic solvent solution of titanate to obtain a mixed system; reacting the mixed system at a preset temperature for a preset time to obtain the Ti-MOF/polymer composite nanofiber, wherein the spinning solution is prepared according to the following method: dispersing carboxylic aromatic hydrocarbon in a polar aprotic solvent to obtain a dispersion; adding a polymer to the dispersion to form a dope; Wherein: the carboxylic aromatic hydrocarbon is selected from terephthalic acid or benzene tricarboxylic acid.
6. 6. The method for producing lithium iron phosphate according to claim 5, wherein the carboxylic acid aromatic hydrocarbon or the polymer satisfies at least one of: The carboxylic aromatic hydrocarbon is selected from terephthalic acid; The polymer is a nitrogen-containing polymer; The polymer is selected from polyimide and/or polyacrylonitrile.
7. 7. The method for producing lithium iron phosphate according to claim 5, wherein the molar volume concentration of the dispersion is 0.033 to 0.1mmol/mL.
8. 8. The method for producing lithium iron phosphate according to claim 5, wherein the molar volume concentration of the organic solvent solution of the titanate is 0.033 to 0.1mmol/mL.
9. 9. The method according to claim 5, wherein the preset temperature is 100 to 150 ℃ and/or the preset time is 12 to 48 hours.
10. 10. The method for preparing lithium iron phosphate according to claim 1, wherein the Ti-MOF/polymer composite nanofiber is dried before being mixed with a lithium source and a ferrophosphorus source.
11. 11. The method for producing lithium iron phosphate according to any one of claims 1 to 10, wherein the lithium source is selected from lithium carbonate and/or the phosphorus iron source is selected from iron phosphate.
12. 12. The lithium iron phosphate is characterized in that titanium element bulk phase doping is arranged in the lithium iron phosphate crystal, the surface of the lithium iron phosphate crystal is coated by a carbon nanofiber network, and the titanium element and the carbon nanofiber network are derived from Ti-MOF/polymer composite nanofibers.
13. 13. Lithium iron phosphate, characterized in that it is obtained by the process for the preparation of lithium iron phosphate according to any one of claims 1 to 11.
14. 14. A positive electrode sheet, characterized in that the positive electrode sheet comprises the lithium iron phosphate according to claim 12 or 13.
15. 15. The positive electrode sheet of claim 14, further comprising a conductive agent, the content of the conductive agent configured to decrease based on the conductivity of the carbon nanofiber network in the lithium iron phosphate.
16. 16. A lithium ion battery comprising the positive electrode sheet of claim 14 or 15.

Description

Preparation method of lithium iron phosphate, positive electrode plate and lithium ion battery Technical Field The invention relates to the technical field of lithium ion batteries, and particularly provides a preparation method of lithium iron phosphate, a positive pole piece and a lithium ion battery. Background In recent years, lithium ion batteries have been widely focused on and applied to the energy storage field, wherein lithium iron phosphate (LFP) as a positive electrode active material has absolute advantages in the energy storage field due to the advantages of stable structure, low cost, long cycle life and the like. The energy efficiency is one of key indexes for judging performance of the lithium iron phosphate in an energy storage battery core, but the lithium iron phosphate is used as a semiconductor material, and the ionic conductivity and the electronic conductivity of the lithium iron phosphate are relatively low, so that element doping or surface coating modification is required to be carried out for improving the dynamic performance. At present, the Ti element doping and carbon coating are most common in the market, however, the Ti doping effect is often poor due to the difficulty of solid phase diffusion in the synthesis process. CN118610442a improves the material interface and improves the electrical properties by spraying a series of Metal Organic Framework (MOF) materials prepared on the surface of the lithium-rich manganese-based material. CN116829768A is used for modifying a lithium extraction electrode material of a salt lake, compounding a lithium manganate electrode with Ti-MOF, inhibiting Mn from dissolving out in the use process of the lithium manganate electrode, and improving the purity of lithium while improving the electrochemical lithium extraction rate. The scheme is mainly characterized in that the electrode material is modified by simple spraying or compounding, the advantages of large specific surface area and high reactivity of the MOF material are not fully utilized, and meanwhile, the uniformity of coating on the surface of the material is difficult to ensure by spraying or compounding. Accordingly, there is a need in the art for a new solution to the above-mentioned technical problems. Disclosure of Invention The invention aims to solve the technical problems, namely, the problems that the modification of the electrode material is carried out by simple spraying or compounding in the prior art, the advantages of large specific surface area and high reactivity of the MOF material are not fully utilized, and the uniformity of coating on the surface of the material is difficult to ensure by spraying or compounding. In a first aspect, the present invention provides a method for preparing lithium iron phosphate, wherein the method comprises: Providing a Ti-MOF/polymer composite nanofiber; Mixing Ti-MOF/polymer composite nanofiber with a lithium source and a ferrophosphorus source to obtain a precursor mixture; Sintering the precursor mixture in an inert atmosphere to obtain the catalyst. In the preferable technical scheme of the preparation method of the lithium iron phosphate, the dosage of the Ti-MOF/polymer composite nanofiber accounts for 0.2% -2% of the total mass of the lithium source and the ferrophosphorus source. In the preferable technical scheme of the preparation method of the lithium iron phosphate, the dosage ratio of the lithium source to the ferrophosphorus source is 1.01-1.08:1 according to the mole ratio of Li element to Fe element. In a preferred technical scheme of the preparation method of the lithium iron phosphate, the sintering temperature is 650-750 ℃. In a preferred technical scheme of the preparation method of the lithium iron phosphate, the Ti-MOF/polymer composite nanofiber is provided by adopting the following method: Providing a spin dope comprising carboxylic acid aromatic hydrocarbons and a polymer; Spinning the spinning solution to prepare composite nano fibers; mixing the composite nanofiber with an organic solvent solution of titanate to obtain a mixed system; reacting the mixed system at a preset temperature for a preset time to obtain the Ti-MOF/polymer composite nanofiber, wherein the spinning solution is prepared according to the following method: dispersing carboxylic aromatic hydrocarbon in a polar aprotic solvent to obtain a dispersion; adding a polymer to the dispersion to form a dope; Wherein: the carboxylic aromatic hydrocarbon is selected from terephthalic acid or benzene tricarboxylic acid. In a preferred embodiment of the above method for producing lithium iron phosphate, the carboxylic aromatic hydrocarbon or the polymer satisfies at least one of the following conditions: The carboxylic aromatic hydrocarbon is selected from terephthalic acid; The polymer is a nitrogen-containing polymer; The polymer is selected from polyimide and/or polyacrylonitrile. In a preferred embodiment of the above method for producing lithium ir