Titanium doped LiVPO4F cathode for lithium ion batteries

• LiVPO4F is doped with Ti4+ by a modified carbothermal reduction method.
• The capacitive, rate and cycling performances are noticeably improved by Ti doping.
• The polarizations at various charge/discharge rates are reduced as well.

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.