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

• Nano-sized anatase TiO2 was synthesized using surfactant-free hydrolysis method.
• The sizes of TiO2 were systematically tuned by controlling the ratio of anion.
• Each TiO2 particle consists of an aggregation of 5 nm primary crystallites.
• The capacity of the TiO2 NA which were 50 nm in size was 171 mAh g− 1 at 100 cycles.
• More than 0.5 Li was inserted into TiO2, which indicates good rate capability.

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 Ti4 + 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.