Anion-controlled synthesis of TiO₂ nano-aggregates for Li ion battery electrodes

Nano-sized anatase TiO₂ was synthesized using surfactant-free hydrolysis method by controlling the ratio of anions in solution. The particle sizes of TiO₂ were systematically tuned by the molar ratio of the Ti^{4 +} precursors (chlorides and sulfates). Each TiO₂ particle consists of an aggregation of 5 nm primary crystallites, resulting in a large specific surface area. TiO₂ nano-aggregates (TiO₂ NAs) which were 50 nm in size exhibited the best cycle stability. After calcination, the capacity of the TiO₂ NA was enhanced to 171 mAh g^{- 1} at 100 cycles at a rate of 0.2 C due to the removal of impediments such as a hydroxyl group and physisorbed water, indicating that more than 0.5 Li was inserted into TiO₂ at 100 cycles, and that these NAs had good rate capability at high current densities.