Facile Synthesis of Nanocrystalline Li[sub 4]Ti[sub 5]O[sub 12] (Spinel) Exhibiting Fast Li Insertion

Nanocrystalline (spinel) was prepared via a sol-gel route employing lithium ethoxide and Ti(IV) alkoxides as the starting reagents. The optimized materials contained less than 1% of anatase as the main impurity and, depending on the synthetic conditions, they exhibited the Brunauer-Emmett-Teller surface areas of Trace amounts of anatase in were conveniently determined by cyclic voltammetry of Li insertion. The lattice constant of the thus-prepared nanocrystalline was between 0.8297 and 0.8340 nm. After hydrothermal growth for 10 h at the lattice constant increased to 0.8366 nm. Thin-film electrodes (2-4 μm) from nanocrystalline exhibited excellent activity toward Li insertion, even at charging rates as high as 250C. This behavior compares favorably with that of microcrystalline made by the usual high temperature solid-state synthesis.