(中南大学 冶金科学与工程学院， 长沙 410083)
摘 要: 以碳凝胶作为碳添加剂， 采用固相法制备了复合型LiFePO4/C锂离子电池正极材料。研究了不同掺碳量对样品性能的影响。 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。 结果表明： 样品中的碳含量（质量分数）分别为0％、 5％、 10％、 22％， 所得样品均为单一的橄榄石型晶体结构， 碳的加入使LiFePO4颗粒粒径减小。另外， 碳分散于晶体颗粒之间， 增强了颗粒之间的导电性。 合成样品的电化学性能测试结果表明， 掺碳后的LiFePO4放电比容量和循环性能都得到显著改善。其中， 含碳量为22％的LiFePO4/C在0.1 C倍率下放电， 首次放电容量达 43.4 mA·h/g， 充放电循环6次后电容量为142.7 mA·h/g， 容量仅衰减0.7%。
关键字: 锂离子电池； 正极材料； 磷酸铁锂； 碳凝胶
（ College of Metallurgy Science and Engineering,
Central South University, Changsha 410083, China）
Abstract: LiFePO4/C composite obtained with carbon gel as carbon droped were prepared by solid-state reaction. The crystalline structure, morphology of particles, carbon contents were analyzed by X-ray diffraction, scanning electromicroscopy and carbon/sulfur determinator. The resulting carbon contents in these samples are 0％, 5％, 10％, 22%, respectively . The results of X-ray diffraction show that the LiFePO4/C is pure olivine-type phase. SEM micrographs confirmed that the addition of the carbon reduces 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 first specific discharge capacities of the LiFePO4/C coated with about 22% carbon is 143.4 mA·h/g, after 6 times cycling the discharge capacities is 142.7 mA·h/g. The capacity fade is about 0.7%.
Key words: Li-ion battery; cathode material; lithium iron phosphate; carbon gel
