Mo-doped Gray Anatase TiO2: Lattice Expansion for Enhanced Sodium Storage

Gray-colored Mo6+-doped anatase TiO2 is prepared uniformly with particle size of 10-20 nm, and is firstly employed as anode material in sodium-ion batteries (SIBs), presenting excellent electrochemical performances. It delivered reversible specific capacities of 231.8 mAh g−1 at 0.1 C (33.5 mA g−1) after 100 cycles and 108.3 mAh g−1 at 5 C (1.68 A g−1), comparing to 170.5 mAh g−1 at 0.1 C and only 41.7 mAh g−1 at 5C for the bare TiO2. The improved electrochemical performances might be beneficial from the doping of Mo6+, which can effectively enhance the conductivity of TiO2 resulting from induced conduction band electrons, interstitial oxygen defects and vacancies. In addition, the doping can also lead to the lattice expansion, which can facilitate the diffusion of Na+. In combination with natural abundance and environmental benignity, Mo6+-doped TiO2 can be expected to be utilized as an anode material for enhanced sodium storage.