碳和石墨烯对磷酸锰锂材料性能的影响

摘要

LiMnPO4 was synthesized by solvothermal method.LiMnPO4/carbon/graphene composites with different amount of pyrolytic carbon and graphene were prepared using sucrose and graphene as carbon sources.The effect of pyrolytic carbon and graphene on the performance of material was investigated.The morphology of the material was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM).Pyrolytic carbon coating can enhance the surface electronic conductivity of LiMnPO4 nanoplates,which plays a major role in improving the performances of the material.Graphene can enhance the electronic and ionic conductivity between nanoplates,and then improve the electrochemical properties of the material.Electrochemical measurements indicate that LiMnPO4 electrode with 4％ pyrolytic carbon and 2％ graphene exhibits better electrochemical performances.The specific capacity is 139.1 mAh ·g-1 at 0.5C and the capacity retention is 93.6％ after 100 cycles.Compared with single carbon and single graphene LiMnPO4 electrode,the specific capacity at 0.5C of LMP-C(4)-G(2) electrode is increased by 35.0％ and 48.6％.%在采用溶剂热法制备磷酸锰锂的基础上,以蔗糖和石墨烯为碳源,制备了裂解碳和石墨烯含量不同的磷酸锰锂/碳/石墨烯复合材料,研究了裂解碳和石墨烯对材料性能的影响.采用扫描电镜(SEM)和透射电镜(TEM)对材料的形貌进行了表征.裂解碳包覆可以提高LiMnPO4纳米片表面的电子导电性,对于材料性能的改善起到主要的作用;石墨烯可以提高纳米片之间的电子和离子导电性,改善材料的电化学性能.电化学测试表明,当裂解碳含量为4％、石墨烯含量为2％时,LiMnPO4电极具有较好的电化学性能,在0.5C下的放电比容量为139.1 mAh·g-1,循环100次后,容量保持率为93.6％.与添加单一碳和单一石墨烯的LiMnPO4电极相比,该电极在0.5C下的放电比容量分别提高了35.0％和48.6％.