Basicity-controlled synthesis of Li₄Ti₅O₁₂ nanocrystals by a solvothermal method

Spinel-type lithium titanate (Li₄Ti₅O₁₂) nanocrystals were synthesized at a low temperature with control of the basicity by a solvothermal method without any calcination processes. The Li-Ti-O precursor was produced under relatively high pH conditions (pH > 11) in the initial stage. The spinel phase was then formed through delithiation and dehydration from the precursor by lowering the pH of the system (pH < 10). The direct synthesis of the Li₄Ti₅O₁₂ nanocrystals was achieved through self-control of the basicity using a two-phase system of water-ethanol and toluene-oleic acid. The Li₄Ti₅O₁₂ crystals were formed from the precursor by decreasing the basicity. The average size of the nanocrystals prepared by the one-step method was ca. 13 nm, and the specific surface area was 158 m² g^-1. On the basis of the electrochemical measurement, the Li₄Ti₅O₁₂ nanocrystals produced in a low-temperature solution system are applicable for an anode material of a lithium-ion rechargeable battery.