Lithium insertion into hollandite-type TiO2

Hollandite-type TiO2 compounds, isostructural with alpha-MnO2, have been investigated as insertion electrodes for lithium batteries. Parent materials of KxTi8O16 (0 < x < 2) were treated with concentrated acid to yield TiO2 products that were essentially free of potassium. Lithium can be inserted into the (2 x 2) tunnels of the TiO2 structure chemically (with n-butyllithium) and electrochemically to an approximate composition Li0.5TiO2. The lithium ions can be easily removed from the lithiated structure by chemical reaction with bromine; cyclic voltammetry indicates that high voltages are required to remove the lithium by electrochemical methods. The poor electrochemical behavior of hollandite-TiO2 contrasts strongly with alpha-MnO2 electrodes. The superior properties of alpha-MnO2 electrodes are attributed to the presence of oxygen ions, either as H2O or Li2O, in the (2 X 2) channels; lithia-stabilized electrodes, 0.15Li(2)O . MnO2, show good cycling behavior and a rechargeable capacity of approximately 180 mA h/g. (C) 1999 Elsevier Science S.A. All rights reserved.