Robust electrochemistry of black TiO2 as stable and high-rate negative electrode for lithium-ion batteries

Electrochemically stable black TiO 2 composed of Ti 3+ ions and oxygen vacancies is successfully synthesized by a facile and economic sol–gel method followed by calcination in nitrogen atmosphere at 400 °C for 2 h. Several physicochemical techniques are probed to validate the desired state of the obtained material. The material is formed in a pure state with an average size of 10 nm. The electrochemical studies are conducted for its use as negative electrode for Li-ion batteries. At high current rate of 5 C, the electrodes deliver a high discharge capacity of 226 mA h g −1 even after 150 cycles. Similarly, the electrodes also deliver discharge capacities of 197 and 153 mA h g −1 at current rates of 7 C and 10 C, respectively. The robust electrochemical properties of black TiO 2 including large specific capacities at high current rates and high stability are ascribed to the formation of defective structure, conductive Ti 3+ ions and oxygen vacancies.