Preparation of dense Ta-LLZO/MgO composite Li-ion solid electrolyte: Sintering, microstructure, performance and the role of MgO

Abstract Cubic phase Li 7 La 3 Zr 2 O 12 (LLZO), a member of the Li–Garnet family, is a promising solid electrolyte and has been widely studied in recent years. However, LLZO samples prepared via conventional ambient air sintering reported in the published literature often contain large grains with lower than desired ( −4  S cm −1 at 25 °C and fracture strength of ∼150 MPa. The sintered samples have uniform fine-grained microstructure and high critical current densities of 0.75–0.95 mA cm −2 at room temperature in Li–Li symmetry cell with Au modification. In addition, systematic sintering experiments and characterizations are conducted to explore the function of MgO in inhibiting the Ta-LLZO grain growth and its existing form inside the composite ceramics.