High-rate and high conductivity mesoporous TiO2 nano hollow spheres: Synergetic effect of structure and oxygen vacancies

TiO 2 is exceptionally useful anode material for Li-ion batteries, and the ability to modify TiO 2 makes it a very attractive and challenging research object for use in different functional materials . In this paper, mesoporous TiO 2 nano hollow spheres (dubbed TiO 2 -1 andTiO 2 -2) with moderate oxygen vacancies were successfully prepared. Structure and composition characterizations revealed that the spheres had a hollow structure, surface oxygen vacancies and an excellent Ti 3+ /Ti 4+ molar ratio of 0.181. In addition, TiO 2 -2 demonstrated synergistic effects in terms of electron and lithium ion transportation, with impedances as low as 3.05 Ω, and its Li-ion diffusion coefficient (7.8 × 10 −12  cm 2  s −1 ) was at least a factor of 10 larger than that of TiO 2 -1(6.2 × 10 −13  cm 2  s −1 ). More importantly, experiments demonstrated that the well-balanced Li + /e − transportation arising from the synergetic effect between structure and Ti 3+ /oxygen vacancy in the optimal TiO 2 -2 sample had a high specific capacity of 233 mAh·g −1 at 0.1C, and 79.8% capacity retention after 100 cycles, as well as greatly enhanced rate performance and electrochemical reactivity and stability in comparison with the other TiO 2 . Our method for creating oxygen vacancies in TiO 2 nano hollow spheres can be generalized to other electrochemical energy storage materials .