Oxygen vacancies enhance lithium-ion storage properties of TiO2 hierarchical spheres

Titanium dioxide (TiO2) is a promising electrode material for reversible lithium storage. However, the poor electronic conductivity, sluggish diffusivity, and intrinsic kinetics limit hinder its fast lithium storage capability. Here we present that the oxygen-deficient TiO2 hierarchical spheres can address the issues for high capacity, long-term lithium-ion battery anode. First-principles calculations show that introducing oxygen vacancies to anatase TiO2 can reduce the bandgap, thus improving the electronic conductivity and further the lithium storage properties of TiO2. By annealing TiO2/H(2)Ti(5)O(11)3H(2)O hierarchical spheres precursor in nitrogen, accompanying with the phase transfer process, the growth of TiO2 crystallites is restricted due to the generation of residual carbon species, resulting in a well maintained hierarchical spherical structure. Rich oxygen vacancies are generated in the oxygen-deficient environment and evidenced by EPR, XPS, and UV-Vis spectra, which enable the TiO2 hierarchical spheres reduced bandgap. The oxygen vacancies in the as-obtained TiO2 hierarchical spheres together with the high structural integrity of the hierarchical spheres gives rise to superior lithium storage properties including a high specific capacity of 282 mAh g(-1) at 200 mA g(-1), and long-term cycling stability with a capacity retention of 85.2 % at 4 A g(-1) over 10000 cycles.