Synthesis and characterization of Li3V2(PO4)3•LiMn0.33Fe0.67PO4/C cathode materials

A new polyanionic cathode material, Li3V2(PO4)(3)center dot LiMn0.33Fe0.67PO4/C for lithium-ion batteries, was synthesized using a sol-gel method and with N,N-dimethyl formamide as a dispersion agent. The analysis of electron transmission spectroscopy and X-ray diffraction revealed that the composite contained two phases. The material has high crystallinity with a grain size of 20-50 nm. The valence states of Mn, V, and Fe in the composite were analyzed by X-ray photoelectron spectroscopy. The electrochemical kinetics in Li3V2(PO4)(3) is effectively enhanced by the incorporation of LiMnPO4 and LiFePO4, via structure modification and reduced Li diffusion length. The Li3V2(PO4)(3)center dot LiMn0.33Fe0.67PO4/C materials displayed high rate capacity and steady cycle performance with discharge capacity remained 148 mAh g(-1) after 50 cycles at the rate of 0.2C. In particular, the composite exhibited excellent reversible capacities, with the values of 157, 134, 120, 102, and 94 mAh g(-1) at charge/discharge 0.2, 0.5, 1, 2, and 5C rates, respectively.