氮掺杂碳包覆LiMn0.8Fe0.2PO4的制备与性能

Preparation and performance of LiMn0. 8Fe0. 2PO4 with nitrogen doped carbon coating

采用溶剂热法制备LiMn0.8Fe0.2PO4(LMFP),再利用聚苯胺热解形成的氮掺杂碳(N-C)进行包覆,得到LMFP/N-C复合材料。用XRD、SEM、透射电镜(TEM)和X射线光电子能谱(XPS)对样品的晶体结构、微观形貌及元素进行分析;以产物为正极活性物质组装锂离子电池,用恒流充放电、循环伏安和交流阻抗实验进行电化学性能测试。在2.0~4.6V充放电,LMFP/N-C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152.5mAh/g、147.5mAh/g、140.0mAh/g、101.8mAh/g和64.6mAh/g,比普通碳包覆的LMFP/C材料分别提高3.6%、14.8%、14.4%、39.0%和90.0%;LMFP/N-C复合材料以5.0C循环80次,比容量仍有81.9mAh/g,容量保持率为80.45%。

LiMn0.8Fe0.2PO4(LMFP)was prepared by solvothermal method,then coated with nitrogen doped carbon(N-C)formed by the pyrolysis of polyaniline to obtain LMFP/N-C composite.The crystal structure,micromorphology and elements were analyzed by XRD,SEM,transmission electron microscope(TEM)and X-ray photoelectron spectrum(XPS).Li-ion battery was assembled with the products as cathode active material,the electrochemical performance was tested by galvanostatic charge/discharge tests,cyclic voltammetry and electrochemical impedance spectroscopy.When charged-discharged in 2.0-4.6 V,the initial specific discharge capacities of the LMFP/N-C composite at 0.2 C,0.5 C,1.0 C,5.0 C and 10.0 C were 152.5 mAh/g,147.5 mAh/g,140.0 mAh/g,101.8 mAh/g and 64.6 mAh/g,respectively,which were 3.6%,14.8%,14.4%,39.0%and 90.0%higher than those LMFP/C materials with conventional carbon coating.The specific capacity of LMFP/N-C composite could still maintain 81.9 mAh/g at the 80th cycle at 5.0 C,the capacity retention rate was 80.45%.