Process for preparing lithium iron phosphate by using liquid phase cocrystallization and mechanical alloying

Abstract

The invention provides a process for preparing lithium iron phosphate by using liquid phase cocrystallization and mechanical alloying. The method is characterized by comprising the following steps: 1) wet ball-milling: mixing various raw materials in a wet ball mill and performing wet ball-milling on the mixture for 3-5 hours, wherein the particle size of the ball-milled raw materials is controlled at 100 meshes, the molar ratio of Fe to Li to PO4<3-> to dispersing agent to doping elements in the raw materials is 1:1:1:0.01-0.015:0.005-0.007, wherein the iron source is selected form ferric oxalate, ferric oxide and ferrous phosphate, the lithium source is selected form LiH2PO4 and Li2CO3, the phosphorus source is selected form NH4H2PO4 and LiH2PO4, the dispersing agent is cetyl trimethyl ammonium bromide, and the doping elements are an arbitrary mixture of yttrium oxide, titanium oxide and chromium oxide; 2) drying: drying the ball-milled raw materials; 3) presintering: performing presintering on the dried raw materials at a temperature of 300-400 DEG C for 4-6 hours; 4) dry ball-milling: adding 1-2wt% of starch into the above-mentioned raw materials, and performing dry ball-milling on the mixture to obtain a material with a particle size of 300 meshes; 5) high-temperature sintering: performing sintering on the mixture at a temperature of 650-700 DEG C for 8 hours; 6)smashing the mixture to obtain a final product of lithium iron phosphate. The process provided in the invention is applicable to industrial large-scale preparation. The products prepared according to the process have an uniform particle size and good electrical conductivity performance.

Description

technical field [0001] The invention relates to a method for preparing a positive electrode material of a lithium ion battery, in particular to a process for preparing lithium iron phosphate by liquid-phase eutectic crystallization combined with mechanical alloying. Background technique [0002] The olivine-type lithium iron phosphate (LiFePO4) material has become one of the most potential lithium-ion power battery materials due to its advantages such as high specific capacity, low price, no environmental pollution, good safety and thermal stability. [0003] In the prior art, methods for synthesizing lithium iron phosphate mainly include: solid-phase method, hydrothermal synthesis method, sol-gel method, aqueous co-deposition method, and the like. [0004] The solid-phase method is the earliest method used to synthesize lithium iron phosphate powder, and it is also a method often used in industrial applications in the early stage. Its equipment and process are simple, whic...

AI Technical Summary

Problems solved by technology

Its equipment and process are simple, which is conducive to the realization of industrialization. Its disadvantages are: large product particles, uneven phase, long calcination time, irregular crystal shape, large particle size distribution range, and poor electrochemical performance.

However, it is only limited to a small amount of powder preparation. Due to the difficulty in designing and manufacturing large-scale high-temperature and high-pressure reactors and the high cost, it is subject to certain restrictions in mass industrial production.

[0006] The sol-gel method is only suitable for the preparation of a small amount of powder. Due to the long aging time of the gel and the large drying shrinkage, the industrial preparation of large quantities is difficult.