制备温度对热解炭包覆磷酸铁锂/气相生长炭纤维复合正极材料的影响

Effects of Preparation Temperature on Pyrolytic Carbon Coated LiFePO_4/Vapor-grown Carbon Fiber (PCLFP/VGCF) Composite Cathode Material

采用微波化学气相沉积法一步合成了热解炭包覆磷酸铁锂/气相生长炭纤维复合正极材料.借助X射线衍射仪、场发射扫描电子显微镜、高分辨透射电镜和电化学测试仪等测试手段研究了不同制备温度对材料晶体结构、显微形貌和电化学性能的影响.结果表明,当制备温度由500℃升至600℃时,磷酸铁锂主晶相的颗粒尺寸没有发生明显变化,而原位VGCF的网络程度却明显增加,材料的放电比容量随之提高;当制备温度进一步升高到700℃时,磷酸铁锂颗粒异常生长现象加剧,VGCF直径较大且粗细不均,材料的电化学性能变差.研究发现,当温度为600℃时,材料表现出较优的电化学性能,25℃在0.2C、0.5C、1C和3C倍率下的放电比容量分别可达163、159、153和143mAh/g.

Pyrolytic carbon coated LiFePO4/vapor-grown carbon fiber（PCLFP/VGCF） composite cathode materi-als were prepared by microwave chemical vapor deposition（MCVD） process.Effects of preparation temperature on microstructures and electrochemical properties of the composites were investigated.The results show that with preparation temperature increasing from 500℃ to 600℃,the discharge capacities of the composite electrodes are improved because of the gradual formation of conductive network of VGCF.However,it decreases when the preparation temperature is up to 700 ℃,which may be attributed to the exaggerated grain growth of LiFePO4 and the reduction of VGCF network.In addition,the composite cathode materials prepared at 600℃ show better elec-trochemical properties,with the discharge capacity as high as 163,159,153 and 143mAh/g at rate of 0.2C,0.5C,1C,3C,respectively（25 ℃）.