锂离子电池LiMn_(1-x)Fe_xPO_4(0<x<1)正极材料的制备及性能研究

Preparation and characterization of positive materials LiMn_(1-x)Fe_xPO_4(0<x<1) for lithium ion batteries

本文采用固相法制备了纯相LiMn1-xFexPO4/C(x=0.2,0.4,0.6)正极材料,并用X射线衍射(XRD)和扫描电镜(SEM)进行表征,用高精度电池测试系统进行充放电和循环伏安测试.结果表明不同Mn和Fe原子比的电极材料具有很大的性能差异,其中当x=0.4时,材料具有优异的循环稳定性和较高的可逆容量.首次充电容量和放电容量分别达到141.5mAh/g和125.7mAh/g,库仑效率高达88.8%,经25次循环后,该电极的放电容量为125.5mAh/g,容量保持率为99.8%.

In this study, a series of phase-pure LiMn1-xFexPO4/C （x = 0. 2, 0.4, 0.6） cathode materials were successfully synthesized by solid-state method. The structure, particle size, surface morphology and electrochemical properties of these cathode active materials were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, electrochemical model cell and cyclic vohammograms （ CV）. The results indicated that the different atom ratio of Mn/Fe affected its electrochemical preformance. A lithium battery using LiMn0.6 Fe0.4 PO4 as the active materials of the positive electrode exhibits a high initial charge capacity and discharge capacity of 141.5 mAh g^-1 and 125.7 mAh g^-1, respectively, and the initial coulombic efficiency is 88.8%. After 25 cycles, it retains 99. 8% of the initial discharge capacity at 0.2C rate, showing perfect cyclic property.