Effect of Mo6+ doping on electrochemical performance of anatase TiO2 as a high performance anode material for secondary lithium-ion batteries

The effects of molybdenum (Mo6+) doping on the electrochemical properties of anatase-type titanium dioxide (TiO2) were investigated. The Mo6+-doped TiO2 samples were prepared using a simple and cost-effective solvothermal method with the doping levels of 1, 3, and 5 wt%, followed by annealing at a low temperature of 300 °C for 5 h. High-resolution synchrotron X-ray diffraction and electron microscopy were conducted to know the structural and morphological properties of doped TiO2 samples. The dopant significantly suppresses the growth of TiO2 grains and reduces the particles sizes, which can also improve markedly the performance and stability of charge/discharge cycles. The particles sizes are in the range of 115-250 nm and 5-10 nm for undoped and Mo-doped TiO2 nanoparticle samples, respectively. Electrochemical results show that the Mo6+-doped TiO2 nanoparticle samples display a significantly lower charge transfer resistance, higher rate capability and excellent reversibility. Author's believed that the high rate performance offered by Mo-doped TiO2 nanoparticle electrodes may be attributed to the enhanced electronic and ionic conductivity, which are achieved by increasing the number of Ti4+ vacancies in the lattice via Mo6+ doping, which may lead to the generation of more free holes in the doped p-type semiconductor. The increased hole concentration in the valence band can contribute to the electrical conductivity of the doped sample.