Abstract
Polycrystalline pellets of Li2Ti3O7 with the ramsdellite-type structure and Li4Ti5O12 with the spinel-type structure were prepared by solid state reaction of Li2CO3 and TiO2. The temperature dependence and annealing effect of Li+ ion conductivity were examined by the complex impedance technique. The conductivity of Li2Ti3O7 decreased due to transformation of the ramsdellite phase to the hexagonal phase during annealing. A break was observed at about 350°C in the Arrhenius conductivity plot of Li4Ti5O12. The conductivity of Li4Ti5O12 was lower than that of Li2Ti3O7, but remained unchanged during annealing. The conduction mechanism of Li+ ion through the spinel structure was discussed based on the ratio of bottleneck radius to Li+ ion radius, and a conduction path was proposed to be 8a→16c→8a positions.
