Effect of Vanadium Substitution on Electrochemical Performance of LiFePO4/C for Lithium-Ion Batteries

LiFe1-xVxPO4/C (x=0, 0.01, 0.03, 0.05, 0.07, 0.1)composites with Vanadium doped and carbon coated were prepared by solid-state method synthesis route, using LiH2PO4 and low-priced Fe2O3 as starting materials. well-crystallized LiFei,VPO4/C composites with high tap density (rho=1.2 g.cm(-3)) were obtained at 700 degrees C for 4 h, which had good electrochemical performance. XPS of V2p and Fe2p for LiFe1-xVxPO4/C samples indicated that the doped Vanadium was V5+ which produced more excess electrons, and improved the electronic conductivity; and the doped Vanadium would not change Iron valence. The analyses of AC impedance indicated that the doped V5+ reduced the charge migration resistance and improved electronic conductivity of the material. The optimum LiFe0.95V0.05PO4/C cathode displayed 155 mAh.g(-1) at 0.1C, 146.5 mAh.g(-1) at 1C, 135.3 mAh.g(-1) at 2C, 125.9 mAh.g(-1) at 5C discharge rate, showing good rate properties. The discharge capacity remained at 119.5 mAh.g(-1) after 500 cycles with a capacity maintenance of 94.9%, showing good cycling stability and practical applications.