LI INSERTION AND ION-EXCHANGE REACTIONS IN THE IONIC CONDUCTING TL2(M,TI)8O16 PHASES WITH HOLLANDITE-TYPE STRUCTURE

Ion exchange reactions and Li insertion in the Tl2(M(x) Ti(8-x))O-16 (M is transition metal and x = 1,2) hollandite-type structure compounds have been investigated. Several new phases were synthesized at 450-degrees-C by an ion exchange reaction using alkali halide salts. A correlation between the ionicity of the M-O bonds and conductivity was confirmed, but no samples exhibited an ionic conductivity exceeding 10(-4)-OMEGA-1 cm-1 at 200-degrees-C. For the first time it was shown that Li can be chemically or electrochemically intercalated into hollandite-type phases as Li(x)Tl2MTi7O(y) with x ranging from 0 to 6. Electrochemical and in situ x-ray powder diffraction measurements have shown that Li insertion in these compounds proceeds at voltages lower than 1.2V and is partially reversible. Upon lithiation, the material undergoes a reversible phase transition. Because of their low Li intercalation voltages, these materials could possibly be used as anodes, instead of Li metal, in secondary Li cells.