锂离子电池正极材料LiFePO4/C的制备及电化学性能研究

摘要

分别以葡萄糖和柠檬酸为碳源,通过碳热还原法合成橄榄石结构的LiFePO4/C正极材料.采用X射线衍射(XRD)及透射电子显微镜(TEM)对产物的结构表面和微观形貌进行了分析,通过恒流充放电以及交流阻抗谱(EIS)表征了产物的电化学性能,探讨了产物容量衰减的原因.结果表明:以葡萄糖为碳源的产物结晶度好,晶粒尺寸小.恒流充放电测试显示其具有更好的电化学性能:0.2 C倍率下首次放电比容量为140.2 mAh/g,循环50次后基本无衰减;1 C的首次放电比容量也达到了120.5 mAh/g.此外,在高倍率充放电过程中,交流阻抗谱显示LiFePO4/C的扩散系数减小,约为1.798×10-12 cm2/s.%The olivine-structured LiFePO4/C cathode material is synthesized with glucose and cit-ric acid as carbon sources via the carbothermal reduction method.X-ray diffraction (XRD)and transmission electron microscopy (TEM)are used to carry out the analysis of the product struc-ture surface and micro-morphology. The product electrochemical properties are characterized through the galvanostatic charge-discharge tests and electrochemical impedance spectroscope (EIS).The product capacity attenuation is discussed.The results show that the product of glu-cose as carbon source has good crystallinity with small grain size.Galvanostatic charge-discharge tests indicate that it has better electrochemical performance:The initial discharge capacity is 140.2 mAh/g at 0.2 C rate,almost no attenuation after 50 cycles.The capacity at 1 C reaches 120.5 mAh/g.In addition,electrochemical impedance spectroscope shows that the diffusion coef-ficient of LiFePO4/C decreases at the process of high rate,about 1.798×10-12 cm2/s.