New Li+-ion conductors, Li4 ? 2xTi1 ?xSxO4, based on the Li4TiO4 structure

Abstract

In the system Li4TiO4?Li2SO4, a wide range of solid solutions, Li4 ? 2xSxTi1 ?xO4(0 < x < 0.2) with Li4TiO4 structure is formed. The ionic conductivity increases with x and exhibits a maximum (bulk) value of 8.30 ? 10?6 S cm?1at 27 �C with an activation energy of 0.51 eV for x= 0.2. The enhancement in conductivity is associated with an increase in concentration of lithium-ion vacancies, created via the mechanism 2Li++ Ti4+ S6+, but is attributable specifically to a decrease in activation energy for conduction. This is the first report of high Li+-ion conductivity in the Li4TiO4structural family.