Titanium doped LiVPO₄F cathode for lithium ion batteries

LiVPO₄F is doped with titanium (Ti) by a modified carbothermal reduction method. X-ray photoelectron spectroscopy indicates Ti is 4+. X-ray diffraction in combination with Rietveld refinement demonstrates that the lattice parameter of LiVPO₄F gets smaller after Ti doping. The doped LiVPO₄F has a specific discharge capacity of 128 mA h g^{- 1}, 107 mA h g^{- 1}, 87 mA h g^{- 1} and 66 mA h g^{- 1} at 0.2 C, 1 C, 2 C and 3 C, respectively, whereas, that of the undoped LiVPO₄F is only 95 mA h g^{- 1}, 84 mA h g^{- 1}, 71 mA h g^{- 1} and 50 mA h g^{- 1}, respectively. The specific capacity at 0.08 C of the doped material even approaches the theoretical capacity of LiVPO₄F if the residual carbon is excluded from calculation. In addition, the capacity retention after 100 cycles at 1 C is enhanced from 77% to 82% by Ti doping.