Electrochemical activity of hydrothermally synthesized Li-Ti-O cubic oxides toward Li insertion

Li-Ti-O oxides prepared by hydrothermal synthesis are active hosts for lithium insertion. Annealing of synthesized samples at temperatures above 250degreesC leads to structural water removal, which causes narrowing of voltammetric peaks and, subsequently, shift of the insertion potential toward more negative potentials. An increase of annealing temperature also improves coulombic efficiency and stability against self-discharge reactions. On the other hand, the lithium insertion/extraction kinetics slows down with increasing annealing temperature. Hydrothermally synthesized Li-Ti-O spinels show more favorable charge transfer kinetics as well as lithium transport comparing with spinels prepared at 800degrees C. Thermodynamics of Li insertion into hydrothermally prepared phases can be described by the Frumkin insertion isotherm. The low temperature prepared spinels seem to be less susceptible to a lithium-insertion triggered phase transition than the high temperature synthesized materials. (C) 2002 The Electrochemical Society.