氧化石墨烯对LiMn_(0.7)Fe_(0.3)PO_4的复合改性

Compound modification of LiMn_(0.7)Fe_(0.3)PO_4 with graphene oxide

为提高LiMn_(0.7)Fe_(0.3)PO_4(LMFP)的电化学性能,首先,采用溶剂热法将氧化石墨烯(GO)与LMFP复合,合成了GO/LMFP复合材料;然后,利用XRD和电感耦合等离子体(ICP)对所得样品的结构和元素进行分析,利用SEM对样品的形貌进行表征,利用电池充放电测试系统和电化学工作站对其进行电化学性能测试。结果表明:所得GO/LMFP复合材料呈现单相橄榄石结构;粒径在200nm左右,且分布较均匀。经GO改性后的复合材料在0.2C、0.5C、1.0C、5.0C和10.0C倍率下的首次放电比容量分别为157.9、148.1、142.0、122.3、87.3mAh·g-1,与C/LMFP复合材料相比,分别提高了5.9%、4.7%、7.0%、24.3%和66.6%。所得结论表明GO的加入有效提高了材料的电子电导率和电化学活性,且与无定型碳共同作用,活性物质的有效利用率提高,GO/LMFP复合材料的循环稳定性也得到改善。

In order to improve the electrochemical performance of LiMn0.7Fe0.3PO4（LMFP）,the graphene oxide（GO）/LMFP composites were synthesized using solvothermal method by compound of GO and LMFP firstly.Then,structure and elements of the samples obtained were analyzed by XRD and inductively coupled plasma（ICP）,the morphologies of samples were characterized by SEM,and the tests for electrochemical performances were conducted by program-controlled battery test system and electrochemical workstation.The results show that the GO/LMFP composites obtained are uniphase olivine structure,the particle size is about 200 nm and the distribution is relatively uniform.The initial discharge specific capacities of composite after the modification of GO were 157.9,148.1,142.0,122.3,87.3mAh·g-1 at rates of 0.2C,0.5C,1.0C,5.0Cand 10.0Crespectively,which increases 5.9%,4.7%,7.0%,24.3%and 66.6%respectively compared with C/LMFP composite.The conclusions obtained show that the adding of GO improves the electronic conductivity and electrochemical activity of the material effectively,and synergistically effects on amorphous carbon,the effective utilization rate of active material increases,and the cycle stability of GO/LMFP composite improve.