Microwave-assisted solvothermal synthesis of nanostructured Ga-Doped Li7La3Zr2O12 solid electrolyte with enhanced densification and Li-ion conductivity

Highlights•Highly conductive Ga-doped Li7La3Zr2O12 formed by a microwave–solvothermal method.•We optimized the Ga content, calcination temperature, grain-size evolution.•Nanostructured precursor and powder formed in a short time at a low temperature.•Dense pellets with less grain boundaries and high cyclic stability were achieved.•These pellets with high Li-ion conductivities are promising solid electrolytes.AbstractGarnet-type Li7La3Zr2O12 (LLZO) Li-ion solid electrolytes are promising candidates for safe, next-generation solid-state batteries. In this study, we synthesize Ga-doped LLZO (Ga–LLZO) electrolytes using a microwave-assisted solvothermal method followed by low-temperature heat treatment. The nanostructured precursor (<50 nm) produced by the microwave-assisted solvothermal process has a high surface energy, facilitating the reaction for preparing garnet-type Ga–LLZO powders (<800 nm) within a short time (<5 h) at a low calcination temperature (<700 °C). Additionally, the calcined nanostructured Ga–LLZO powder can be sintered to produce a high-density pellet with minimized grain boundaries under moderate sintering conditions (temperature: 1150 °C, duration: 10 h). The optimal doping concentration was determined to be 0.4 mol% Ga, which resulted significantly increased the ionic conductivity (1.04 × 10−3 S cm−1 at 25 °C) and stabilized the cycling performance over 1700 h at 0.4 mA cm−2. This approach demonstrates the potential to synthesize oxide-type solid electrolyte materials with improved properties for solid-state batteries.