固相法合成原位碳包覆LiFePO4复合正极材料及其性能

以LiH2PO4和FeC2O4.2H2O为原料,聚乙烯醇为碳源,通过机械化学活化辅助固相法合成原位碳包覆的LiFePO4材料;考察合成温度对LiFePO4/C材料晶体结构、物理和电化学性能的影响。结果表明:700℃下处理的产物结晶良好、分布均匀、颗粒细小;在最佳的热处理条件下,热解碳在LiFePO4颗粒表面形成了良好的纳米导电层,LiFePO4/C材料在0.1C、0.5C、1C和2C倍率下放电比容量分别为155.7、150.1、140.1和130 mA.h/g,且材料在0.1～2C范围内充放电都有很平稳的平台,极化小,并具有较高的高倍率(2C)放电比容量和较好的循环性能。

Synthesis of in-situ carbon-coated LiFePO4 cathode material by solid state reaction and its performance

In-situ carbon-coated LiFePO4 cathode material was prepared by ball-milling activation and subsequent solid state reaction with LiH2PO4 and FeC2O4·2H2O as starting materials,and polyvinyl alcohol(PVA) as carbon source.The effects of synthetic temperature on the crystal structure,physical property and electrochemical performance of LiFePO4/C composites were studied.The results show that 700 ℃ is the optimal synthetic temperature.Under this temperature,the pyrolytic carbon forms an excellent nano conducting layer on the surface of LiFePO4 particles.The discharge capacities of the sample at 0.1C,0.5C,1C and 2C rate are 155.7,150.1,140.1 and 130 mA·h/g,respectively.The sample has a very stable discharge plateau,mild polarization,preferable high rate performance between 0.1C and 2C rate which displays good cyclic capability and higher reversible discharge specific capacity at 2C rate.