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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。
LiOH, H3PO4 and FeSO4 as raw materials, hydrothermal synthesis of a well-crystalline nano-LiFePO4 material. On this basis, LiFePO4 / 0.5% graphene composite was hydrothermally synthesized by adding a small amount of graphene. XRD, SEM and other characterization results show that, LiFePO4 / 0.5% graphene composites have the typical olivine structure, adding a small amount of graphene can further reduce the LiFePO4 particle size. The results of constant current charge-discharge and AC impedance tests show that the incorporation of graphene can improve the contact conductance between LiFePO4 particles and LiFePO4 particles and the current collector, thus reducing the charge transfer resistance during lithium ion insertion and thus improving high-rate charge and discharge performance. In addition, the particle size of LiFePO4 becomes smaller after adding graphene, and the diffusion path of lithium ions is reduced, which is beneficial to improve the high-rate performance.