不同平均分子量PEG组合体系对合成LiFePO_4/C复合材料结构与电化学性能的影响

Structural and Electrochemical Property of LiFePO_4/C Composites Prepared by Different PEG Combination Systems

以不同平均分子量的聚乙二醇(PEG)组合体系为纳米结构控制剂和碳源,采用旋转蒸干法制备了LiFePO4/C复合材料。采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和恒电流充放电测试等手段对其晶体结构、形貌与电化学性能进行了表征。结果表明:不同的PEG组合体系对LiFePO4的晶体尺寸和颗粒形貌具有调控作用,由PEG200+PEG35K(平均分子量为35 000的聚乙二醇)组合体系制备的LiFePO4/C颗粒呈球形,粒径细小而均匀,且具有较好的电化学性能,0.1C和1C倍率下首次放电比容量分别为168.3 mA.h/g和138.1 mA.h/g。

The LiFePO4/C composites were prepared by rotary evaporation method using different molecular weights polyethylene glycol（PEG） combination systems as the template and the carbon source.The crystal structure,morphology and electrochemical performance of the samples were investigated by X-ray diffraction（XRD）,scanning electron microscope（SEM）,transmission electron microscopy（TEM） and galvanostatic charge-discharge tests.The results show that the crystalline size and morphology of the LiFePO4/C composites can be controlled by the different combination systems.The sample synthesized using PEG200＋PEG35K as carbon source has spherical shape and small size with narrow size distribution.It shows the outstanding electrochemical performance with the first discharge capacities of 168.3 mA·h/g,138.1 mA·h/g at 0.1C and 1C rate respectively.