Enhanced densification of garnet-type solid electrolytes under oxygen-enriched sintering atmosphere

Abstract

High-temperature sintering is essential for the densification of garnet-type solid electrolytes to achieve high ion conductivity and suppression of Li-dendrite growth. In this study, the densification and electrochemical performance of Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZT) electrolyte was optimized by controlling the oxygen content of the atmosphere during sintering. Electrochemical tests were performed on sintered and densified pellets at oxygen contents between 0.005 and 99.995 vol.% using a gassing approach. The relative density and critical current density were optimized to 97.6% and 1.0 mA/cm², respectively, at a high oxygen content. As oxygen content increased, sintered pellets exhibited increased lithium-oxide content by inhibiting Li-loss, facilitating densification. These results are expected to promote the implementation of high-quality LLZT electrolyte and solid-state batteries by exploiting the role of oxygen content during sintering. This study shows that high-quality manufacturing can be achieved with low-cost, pressureless sintering.