Improved electrochemical performances of nanocrystalline LiFePO4/C composite cathode via V-doping and VO2(B) coating

LiFePO4/C and V-doped LiFePO4/C with VO2(B) coating composite were prepared by an inorganic-based sol-gel method and the related properties were compared. The V-doping and VO2(B) coating was verified by high-resolution transmission electron microscopy and energy-dispersive X-ray spectrometry. The formation mechanism of the VO2(B) coating was deduced. The XPS analysis suggested that the valence state of V was +4. The coupling effects of the V-doping and VO2(B) coating on the electric conductivity, lithium-ion diffusion velocity and discharge specific capacities at various C-rates were investigated. It is found that the V-doping and VO2(B) coating result in the increase of the bulk electric conductivity, the improvement of the kinetics and the enhancement of the rate capability. Moreover, the cyclic stability was not influenced significantly, even at 10C. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.