Facile synthesis of nanocrystalline Li4Ti5O12 (spinel) exhibiting fast Li insertion

Nanocrystalline Li4Ti5O12 (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 53-183 m(2)/g. Trace amounts of anatase in Li4Ti5O12 were conveniently determined by cyclic voltammetry of Li insertion. The lattice constant of the thus-prepared nanocrystalline Li4Ti5O12, was between 0.8297 and 0.8340 nm. After hydrothermal growth for 10 h at 150degreesC, the lattice constant increased to 0.8366 nm. Thin-film electrodes (2-4 mum) from nanocrystalline Li4Ti5O12 exhibited excellent activity toward Li insertion, even at charging rates as high as 250C. This behavior compares favorably with that of microcrystalline Li4Ti5O12 made by the usual high temperature solid-state synthesis. (C) 2001 The Electrochemical Society.