Tailoring grain growth and densification toward a high-performance solid-state electrolyte membrane

The synthesis of dense and uniform solid-state electrolyte membranes for Li batteries is challenging due to the lack of fine control over the grain growth by conventional sintering methods. Using such techniques, abnormal grain growth can often occur, with associated contaminants and voids, often resulting in electrolyte membranes that suffer from high resistivity, poor stability, and the risk of Li dendrite penetration. Herein, we report a new high-temperature (1500 K) and rapid sintering (30 s) process by Joule heating that tailors the grain growth and densification toward high-quality, high-performance solid-state electrolyte membranes. The high temperature contributes to the rapid removal of impurities, leading to a dense and uniform microstructure in seconds. The short sintering time provides controlled grain growth, with nearly unchanged grain size and distribution compared to the solid-state electrolyte powders prior to sintering. Using calcined Ta-doped Li7La3Zr2O12 (LLZTO) garnet powders, we show that the grain size distribution before and after the rapid sintering are nearly identical (∼4 μm for both), while defects (e.g., voids and gaps) and impurities are effectively eliminated. The resulting high-quality membrane features good ionic conductivity (6.4 × 10−4 S cm−1 at room temperature) and excellent stability during lithium striping/plating (>300 h under 0.2 mA cm−2), making it suitable for Li battery applications. This high-temperature rapid sintering approach can be further extended to a variety of ceramic Li+ conductors toward the future development of solid-state batteries.