New solid electrolytes and mixed conductors: Li3 + xCr1 ? xMxO4: M = Ge, Ti

Abstract

New Li+ ion conducting solid solutions with ?-LISICON type structure have been found in the system Li3 + xCr1 ? xGexO4 for 0.35 < x < 0.92. Conductivity increases with x; at x = 0.90, ? (bulk) ? 1.4 ? 10?5 S cm?1 at 27 �C rising to 0.044 S cm?1 at 300 �C; Ea = 0.51 eV. Similar ? solid solutions form in the Ti system, Li3 + xCr1 ? xTixO4: 0.5 < x <0.8; however, these are mixed Li+ ion and electronic conductors. Both systems are unusual in containing Cr in the +V oxidation state.