用碳热还原法制备LiFePO_4/C复合正极材料  

Preparation of LiFePO_4/C composite cathode materials by a carbothermal reduction method

作　　者：刘会平[1] 王志兴[1] 李新海[1] 郭华军[1] 彭文杰[1] 

机构地区：[1]中南大学冶金科学与工程学院,湖南长沙410083

出　　处：《功能材料》2008年第8期1302-1305,共4页Journal of Functional Materials

基　　金：国家重点基础研究发展计划(973计划)资助项目(2007CB613607);国家自然科学基金(50302016)

摘　　要：以Fe_2O_3为铁源,以葡萄糖为碳添加剂,利用碳热还原法成功地制备了LiFePO_4/C复合材料。研究了不同焙烧温度对样品性能的影响。利用X射线衍射仪、扫描电镜和碳硫(质量分数)分析方法对所得样品的晶体结构、表面形貌、含碳量进行分析研究。研究结果表明,样品中碳含量(质量分数)为10%的LiFePO_4/C复合材料为单一的橄榄石型晶体结构,碳的加入使LiFePO_4颗粒粒径减小。碳分散于晶体颗粒之间,增强了颗粒之间的导电性。电化学性能测试结果表明,LiFePO_4/C充放电性能和循环性能都得到显著改善。其中,碳含量为10%在700℃下焙烧8h合成出的样品电化学性能最佳,在0.1、0.5和1C倍率下放电,LiFePO_4/C首次放电比容量达159.3、137.0、130.6mAh/g,充放电循环30次,容量只衰减了2.2%、5.3%、7.6%。其表现出良好的循环性能。LiFePO4/C composite were prepared by carbothermal reduction method, Fe2O3 were used as Fe sources, glucose as carbon droped. We have studied the influence of the different temperature to the sample performance. The crystalline structure, morphology of particles, carbon contents were analyzed by X-ray diffraction, scanning electromicro scopy and carbon/sulfur determinator, The resulting carbon contents in these samples are 10wt% in theory. The results of X-ray diffraction showed that the LiFePO4/C was pure olivine-type phase. SEM micrographs confirmed that the addition of the carbon reduced the LiFePO4 grain size. The carbon is dispersed between the grains, ensuring a good electronic contact. Electrochemical tests show that the material obtained by adding carbon gives enhanced performance in term of improved practical capacity and cycleability. The products sintered at 700℃ for 8h possessed excellent electrochemical performance. The first specific discharge capacities of the LiFePO4/C is 159.3,137.0,130.6mAh/g respectively at 0.1, 0.5 and 1C, the discharge capacities fading is only 2.2% ,5.3% and 7.6% after 30 times cycles. The LiFePO4/C composite shows a good performance of the cycle.

关 键 词：锂离子电池 磷酸铁锂 三氧化二铁 碳热还原法 

分 类 号：TM912.9[电气工程—电力电子与电力传动]