锂掺杂对石墨电化学性能的影响

Effects of Li-doping on electrochemical characteristics of graphite anode

研究了掺杂锂元素对用作锂离子电池负极的石墨材料的结构与性能的影响。XRD及元素分析结果表明 :锂以化合物的形式存在于石墨材料中 ,由于缺陷结构的增加 ,掺杂后石墨材料的BET比表面积略有增大。电化学测试结果表明 :预先掺锂能够有效减少首次充放电过程中的不可逆容量 ,使石墨电极的可逆容量增加。与未掺杂的热处理石墨比较 ,可逆嵌锂容量由 30 4 .5mA·h/g增加到 312 .2mA·h/ g ,首次充放电不可逆容量由6 6 .4mA·h/ g减少到 5 2 .9mA·h/ g。以掺锂改性石墨为负极制作成 0 6 344 8型锂离子电池后 ,电池的容量和循环稳定性均得到改善 ,以 1C倍率充放电时 ,放电容量可达 84 5mA·h ,循环 2 0 0次后的容量保持率为 91.6 5 %。

Effects of Li-doping on the structure and characteristics of graphite anode for Li-ion batteries were studied. The results of X-ray diffraction (XRD) and element analysis show that lithium exists as compounds in the graphite. The Brunauer-Emmer-Teller (BET) surface area of Li doped graphite is increased because some defects are introduced. According to the electrochemical measurements, the Li doped graphite has large reversible capacity because of its low irreversible capacity loss in the initial charge/discharge cycle. The reversible capacity and irreversible capacity of the heat treated graphite are 304.5 mA·h/g and 66.4 mA·h/g, while those of the Li doped graphite are changed into 312.2 mA·h/g and 52.9 mA·h/g respectively. Being charged/discharged at 1C(800 mA) current rate, the Li-ion batteries with Li doped graphite anode have large capacity of 845 mA·h and high capacity retention ratio of 91.65% after 200 cycles.