Electrochemical modification of spinel oxide materials using lithium solid state electrolyte

Solid solutions of the general formula LiFe1-yTi1-xMnx+yO4 (0 <= x <= 1; 0 <= y <= 1) were prepared and investigated using X-ray diffraction, Mossbauer spectroscopy and electrical measurements. It was shown that substitution of transition elements, first titanium, then iron, for Mn in the spinel structure results in a linear decrease in the lattice parameter. Electrical conductivity increases monotonously with an increase in the concentration of manganese. Conductivity is electronic and proceeds by thermally activated polaron hopping mechanism with the activation energy decreasing with x + y from 0.50 eV to 0.33 eV. Quenched samples have enhanced conductivity and larger lattice parameter, possibly due to the oxygen nonstoichiometry. According to Mossbauer spectroscopy data, the distribution of iron cations changes as a function of the Mn content; for x + y < 1, almost all the Fe3+ cations occupy tetrahedral positions. The first experiments were made on the electrochemical charging of Fe-containing spinels under study using solid-state electrochemical cells with oxide anodes and cathodes. (c) 2006 Elsevier B.V. All rights reserved.