纳米LiFePO_4/石墨烯复合材料的制备与表征

Preparation and characterization of LiFePO_4/graphene composite nanomaterial

以LiOH、H3PO4和FeSO4为原料,采用水热法合成了结晶良好的纳米LiFePO4材料。在此基础上,掺入少量还原石墨烯,水热合成LiFePO4/0.5%石墨烯复合材料。XRD、SEM等表征结果表明,LiFePO4/0.5%石墨烯复合材料具有典型橄榄石结构,添加少量石墨烯能进一步减小LiFePO4颗粒尺寸。恒流充放电和交流阻抗测试结果表明,掺入石墨烯能够改善LiFePO4颗粒之间以及LiFePO4颗粒与导电集流体的接触电导,这样减小锂离子嵌入过程的电荷转移电阻,从而改善高倍率充放电性能。此外,添加石墨烯后LiFePO4颗粒尺寸变小,锂离子扩散路径减小,有利于改善高倍率性能。

The LiFePO4/0.5 %graphene composite nanomaterial was prepared by hydrothermal method with I.iOH, H3 PO4 and FeSO4 as starting materials. The characterization by XRD and SEM showed that the composite was single phase material of olivine structure and the particle size was reduced. The electrochemical charge/discharge showed that the high- rate performance of LiFePO4 cathode was significantly improved with the addition of graphene. And this can be ascribed to the reduced charge transfer resistance hecause of improved electronic conductivity between LiFePO4 particles, and the parti- cles with the current collector. On the other hand,the reduced particle size can reduce the diffusion path of Li＋ ions. This was also helpful to the improvement of high rate performance.