Improving the electrochemical performance of anatase titanium dioxide by vanadium doping as an anode material for lithium-ion batteries

摘要

Undoped and 2 wt% vanadium (V~(5+)) doped TiO_2 samples are prepared in polyol medium by lowtemperature solvothermal method. The as-prepared samples are annealed at 400 ℃ for 5 h in an air atmosphere to increase the crystallinity. The XRD pattern shows that pure anatase TiO_2 is formed in both the doped and undoped samples. The maximum sizes of nanopartides are found to be 300 nm and 15 nm with spherical shaped morphology for undoped TiO_2 and V~(5+) doped TiO_2 samples respectively. In addition, 2 wt% V~(5+) doped sample exhibits excellent electrochemical performance with high reversible specific capacity and excellent rate capability compared to the undoped case. This improvement can be attributed to the substitution of the Ti~(4+) ions by V~(5+) ions in the TiO_2 lattice and create more Ti~(4+) vacancies in the lattice. This action may lead to the generation of apparently more number of free holes in the doped p-type semiconductor. Therefore, the increased hole concentration in the valence band can contribute to the electrical conductivity of the doped sample. Vanadium doping also influences the sample crystallinity and reduces the particle size, which provides a larger active surface area than that of undoped TiO_2.