(592g) Preparation of Cubic Garnet Oxide As Solid-State Electrolyte with High Li-Ion Conductivity

The cubic garnet-type ceramic with the formula of Li₇La₃Zr₂O₁₂ (LLZO) is a promising solid-state electrolyte (SSE) with high chemical stability against lithium metal and electrode materials, and a wide electrochemical potential window. However, the practical application of this LLZO electrolyte is limited, due to its low total conductivity. The root cause of the low conductivity is the high boundary resistance between grains in electrolyte pellet, combining with the formation of a tetragonal phase during material synthesis. In this study, cubic LLZO was prepared through an approach involving the co-precipitation, followed by hydrothermal treatment and high temperature sintering processes in sequence. The hydroxide precursor was firstly synthesized through the co-precipitation routine, and then modified by using the hydrothermal treatment. Mixed with lithium salt, the cubic LLZO was fabricated through the high temperature sintering. The effect of hydrothermal conditions on the properties of final LLZO products was investigated. The results from electron microscopy demonstrated that precursors with columnar shape and tunable particle size were obtained after the hydrothermal treatment. In further, the final LLZO electrolyte pellet prepared with hydrothermally treated precursor showed significantly improved the total ionic conductivity, compared with those without hydrothermal treatment.