TiO₂/C tetragons with a double-side concave nanostructure and its high rate performance on Na-ion storage

TiO₂ is acting as a low-cost and promising candidate for a high capacity anode material of Na-ion batteries. Its insufficient cyclability and poor capacity utilisation for Na-ion storage can be improved by manipulating its nanostructures. We designed and prepared a carbon-coated TiO₂ (TiO₂/C) material with a double-side concave structure and a large surface area. The as-synthesised TiO₂/C with such special nanostructure, delivered a high capacity of ca. 175 mAh g⁻¹ at 1 A g⁻¹ rate with roughly 100% capacity retention over 1600 cycles and ca. 100% Coulombic efficiency. More significantly, TiO₂/C concave tetragons exhibited an outstanding rate capacity of 150 mAh g⁻¹ and 60 mAh g⁻¹ at 5 A g⁻¹ and 20 A g⁻¹, respectively. These results demonstrate the design of the special TiO₂/C concave tetragons allows a sufficiently long cycle life for battery applications, superior reversibility and enhanced rate for the Na-ion storage.