Preparation of Nano-structured LiFe xMn 1-xPO 4 (x=0, 0.2, 0.4) by Reflux Method and Research on the Influences of Fe(II) Substitution

Nano structured LiFe xMn 1-xPO 4 (x=0, 0.2, 0.4) materials were successfully prepared by one-step reflux method in a water/PEG400 mixed solvent, and were coated by carbon using glucose as the precursor. The materials were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The electrochemical properties of the materials were investigated by galvanostatic cycling, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It was found that the materials consisted of nanorods with a diameter of 50 nm and a length of 500 nm. Galvanostatic cycling showed that the capacity of LiMnPO 4 could be largely increased by Fe 2+ substitution. At a current rate of C/20, the capacity of the three samples (x=0, 0.2, 0.4) were 47, 107 and 150 mA·h·g -1 respectively. CV result showed that the Fe 2+ substitution could decrease the polarization during charging/discharging, accelerating the electrochemical process. EIS result showed that the Fe 2+ substitution could decrease the charge transfer resistance between the electrode and electrolyte, as well as increase the Li-ion diffusion coefficient in the bulk material, resulting in an improved electrochemical performance. © 2012 The Chinese Society for Metals.