The low and high temperature electrochemical performance of Li3VO4/C anode material for Li-ion batteries

The carbon-coated Li3VO4 (Li3VO4/C) sample was synthesized by simple solid-state reaction method using glucose as carbon source. Rietveld refinement, XPS and element analysis results show that, though it is synthesized in the presence of carbon and reducing atmosphere, both the single-phase Li3VO4/C and the valence of vanadium of +5 can be retained. The SEM and TEM images reveal that Li3VO4/C composite has uniform particles with size less than 1 mu m. Electrochemical testing results show that Li3VO4/C at high operation temperatures holds both higher specific capacity and cyclic performance than that of low temperatures. The initial discharge capacities for the Li3VO4/C electrodes at temperatures of -20, 0, 25 and 50 degrees C are 312, 600, 760 and 721 mAh g(-1) with the coulombic efficiency of 40.45%, 72.09%, 74.34% and 73.41%, respectively. Even at a high discharge/charge rate of 15 C, the capacities of the Li3VO4/C electrodes at -20, 0, 25 and 50 degrees C still can retain about 20, 120, 370 and 450 mAh g(-1), respectively. The CV results demonstrate that the higher operation temperature can decrease the voltage polarization of the electrode, thus benefit the electrochemical performance of the Li3VO4/C electrode. In addition, the EIS results indicate that larger charge-transfer resistance and smaller lithium diffusion coefficient can be obtained at low operation temperatures, which should be one of the major reasons for its poor low-temperature performance of the Li3VO4/C electrode. (C) 2015 Elsevier B.V. All rights reserved.