Hierarchical nanorod-based TiO₂ microspheres for superior electrochemical energy storage

Nanorod-based rutile TiO₂ microspheres composed of numerous single-crystalline nanorods are successfully fabricated by hydrothermal treatment of peroxo titanic acid in acidic solution. The formation of highly oriented nanorod-based microspheres can be explained in view of crystal growth under the coordination chemistry rule, followed by particle attachment and coalescence. As anodes for Li-ion batteries, the TiO₂ microsphere electrodes show enhanced rate performance, deliver a high reversible specific capacity of 180 mAh g⁻¹ at 0.2 C (33.6 mA g⁻¹) and 85.6 mAh g⁻¹ at an extremely high rate of 50 C with an outstanding retention of 47.5%. These remarkable electrode properties are attributed to the efficient electron-transport by the hierarchical conductive pathway which promoted electronic conductivity and the shortened Li⁺ diffusion length resulting from the ultrafine nanorod structure.