Li-ion conductivity and electrochemical stability of A-site deficient perovskite-structured Li3x-yLa1-xAl1-yTiyO3 electrolytes

Perovskite-type Li3x-yLa1-xAl1-yTiyO3 (x = 5y/12) solid electrolytes with varying Ti content (y = 0.4, 0.6, 0.8, 0.9, and 1) were prepared by conventional solid-state reaction process. Furthermore, the crystal structure, Li-ion conductivity, and electrochemical stability were investigated by X-ray diffraction, alternating current impedance, and cyclic voltammetry. X-ray diffraction analysis showed minimum impurities and a change from cubic to tetragonal with increasing Ti content. Maximum bulk and total conductivities of 1.99 × 10–3 S cm–1 and 4.53 × 10–4 S cm–1 were obtained in Li0.25La0.583TiO3, with activation energy of 0.28 eV and electronic conductivity of 2.30 × 10–9 S cm–1 at 20 °C. Cyclic voltammetry showed that Al-contained materials such as Li0.2La0.667Al0.2Ti0.8O3, and Li0.225La0.625Al0.1Ti0.9O3 were slightly more stable than Li0.25La0.583TiO3 vs. Li+/ Li. LiFePO4/Li batteries were fabricated using Li0.225La0.625Al0.1Ti0.9O3, and Li0.25La0.583TiO3 as solid electrolyte separators, a capacity of 79.0, and 112.0 mA h g–1 at 25 °C were maintained over 100 cycles, respectively.