Influence of tetragonal/cubic phase composition on the total ionic conductivity of Li3xLa2/3−xTiO3

Abstract

Lithium lanthanum titanate (Li3xLa2/3−xTiO3, abbreviated as LLTO, where x = 0.08, 0.1, 0.12, 0.14, 0.16, and 0.167) is prepared using a conventional solid-phase method, and its crystal structure, phase composition, microstructure, and electrical properties are investigated. Experimental results indicate that when the Li content is low (x = 0.8), there exist tetragonal, cubic, and orthogonal phases in LLTO. As the Li content increases (x ≥ 0.1), the orthogonal phase disappears, and there are changes in the phase composition of tetragonal and cubic phases. When the occupancy rates of Li and La are low, the number of A-site vacancies increases, as does the electrical conductivity of LLTO. At room temperature, the ionic conductivity of LLTO increases and then decreases. The Li0.30La0.56TiO3 ceramic electrolyte exhibits the highest total ionic conductivity of 7.22 × 10−5 S/cm, a minimum activation energy of 0.31 eV, and an electrical conductivity of 6.26 × 10−11 S/cm. This paper provides a theoretical basis for subsequent research on solid Li3xLa2/3−xTiO3 electrolytes.