二次加碳中有机碳源对LiFePO4/C性能的影响

采用高温固相合成法制备了碳包覆磷酸铁锂正极材料,使用不同有机碳源对LiFePO4进行碳包覆。通过热分析(TG-DSC)、X-射线衍射光谱法(XRD)、热场发射透射电子显微镜(HRTEM)、显微激光拉曼光谱等分析方法对其相组成、化学结构和碳结构等进行分析,并对LiFePO4/C为正极材料的电池进行了测试。结果表明:酚醛树脂、蔗糖、聚乙二醇和柠檬酸为有机碳源所制备的LiFePO4材料,都为纯相的LiFePO4;碳包覆LiFePO4材料,具有较完整的碳包覆层,且都有石墨结构的有序碳生成,能改善材料的电导率;酚醛树脂为有机碳源得到的LiFePO4/C材料性能最好,在0.1C倍率下充放电,首次放电比容量达到148.6 mAh/g,1C倍率下充放电的比容量达到125.1 mAh/g。

Effects of Organic Carbon Source on Performance of LiFePO4/C in Twice Carbon Coating

LiFePO4/C cathode material was prepared by high temperature solid phase method,with different organic carbon sources as carbon coating.The phase composition,chemical structure and carbon structure of the LiFePO4/C were studied by the methods of TG-DSC,XRD,TEM and Raman.The battery with LiFePO4/C as cathode material was tested.It is shown that the LiFePO4/C synthesized with phenolic resin,sucrose,polyethylene glycol and citric acid as organic carbon sources were all single-phase materials.The carbon-coated LiFePO4 has a complete carbon coating where is generated ordered carbon with graphite structure,which can improve the conductivity of LiFePO4/C.The LiFePO4/C prepared with the organic carbon source of phenolic resin has the best electrical conductivity.The first discharge specific capacities of the samples were 148.6 mAh/g at 0.1C and 125.1 mAh/g at 1C,respectively.