The influences of adding vanadium to the structure evolution and electrochemical performance of LiFePO4 are systematically investigated by in-situ X-ray powder diffraction and X-ray absorption near edge structure spectroscopy. The results indicate that the addition of a small amount of vanadium (less than at 1%) significantly reduces the formation of non-crystalline (highly disordered) triphylite and remnant heterosite phases in the cathode of battery especially at the rate capability higher than 0.5C. The cycle stability of LiFePO4 cathode with vanadium additive after 80 cycles is improved by 14.9% compared to that without vanadium additive. Such an enhancement could be attributed to the ion diffusion kinetics being improved and inactive triphylite being reduced by the supervalent-vanadium additive in cathode during electrochemical redox cycles.