Effect of Gallium Substitution on Lithium-Ion Conductivity and Phase Evolution in Sputtered Li_{7-3 x}Ga _x La₃Zr₂O₁₂ Thin Films

Replacing the liquid electrolyte in conventional lithium-ion batteries with thin-film solid-state lithium-ion conductors is a promising approach for increasing energy density, lifetime, and safety. In particular, Li₇La₃Zr₂O₁₂ is appealing due to its high lithium-ion conductivity and wide electrochemical stability window. Further insights into thin-film processing of this material are required for its successful integration into solid-state batteries. In this work, we investigate the phase evolution of Li_7-3xGa_xLa₃Zr₂O₁₂ in thin films with various amounts of Li and Ga for stabilizing the cubic phase. Through this work, we gain valuable insights into the crystallization processes unique to thin films and are able to form dense Li_7-3xGa_xLa₃Zr₂O₁₂ layers stabilized in the cubic phase with high in-plane lithium-ion conductivities of up to 1.6 × 10^-5 S cm^-1 at 30 °C. We also note the formation of cubic Li₇La₃Zr₂O₁₂ at the relatively low temperature of 500 °C.