Structure, stability, and ionic conductivity of perovskite Li2x-y Sr1-x-yLayTiO3 solid electrolytes

Solid electrolytes with high lithium-ion conductivity and superior stability are key components in the development of all-solid-state lithium-ion batteries. In this study, novel quaternary solid electrolytes Li2x-y Sr1-x-yLayTiO3 (x = 3y/4, y = 1/7, 2/7, 3/7, 1/2, 15/28, and 4/7) were synthesized by conventional solid-state reaction approach. X-ray diffraction analysis revealed that with the increase in La3+ content, La2x-ySr1-x-yLayTiO3 structure changes from cubic to tetragonal perovskite-type structure. Electrochemical impedance spectroscopy revealed that with the increase in y-value, enhanced conductivity was initial observed, followed by a decrease. Li15/56Sr1/16La15/28TiO3 electrolyte exhibited optimal total Li-ion conductivity of 4.84 x 10(-4) S cm(-1), electronic conductivity of 6.84 x 10(-10) S cm(-1), and activation energy of 0.29 eV. On the other hand, cyclic voltammetry revealed unstable Li1/8Sr1/8La1/2TiO3, and Li15/56Sr1/16La15/28TiO3, and Li2/7La4/TiO3 specimens at voltages of less than similar to 2 V, indicative of their incompatibility with lithium metal or Li4Ti5O12 in all-solid-state batteries. Charge-discharge tests confirmed the utility of electrolytes as solid separators with good performance in semi-solid-state batteries. Overall, these results are beneficial for future research on solid electrolytes and their applications in all-solid-state lithium-ion batteries.