Li-Ion Conductivity of Single-Step Synthesized Glassy-Ceramic Li₁₀GeP₂S₁₂ and Post-heated Highly Crystalline Li₁₀GeP₂S₁₂

Li10GeP2S12 is a phosphosulfidesolid electrolyte that exhibits exceptionally high Li-ion conductivity,reaching a conductivity above 10(-3) S cm(-1) at room temperature, rivaling that of liquid electrolytes. Herein,a method to produce glassy-ceramic Li10GeP2S12 via a single-step utilizing high-energy ball milling wasdeveloped and systematically studied. During the high energy millingprocess, the precursors experience three different stages, namely,the 'Vitrification zone' where the precursors undergohomogenization and amorphization, 'Intermediary zone'where Li3PS4 and Li4GeS4 are formed, and the 'Product stage' where the desiredglassy-ceramic Li10GeP2S12 is formedafter 520 min of milling. At room temperature, the as-milled sampleachieved a high ionic conductivity of 1.07 x 10(-3) S cm(-1). It was determined via quantitative phaseanalyses (QPA) of transmission X-ray diffraction results that theas-milled Li10GeP2S12 possessed ahigh degree of amorphization (44.4 wt %). To further improve the crystallinityand ionic conductivity of the Li10GeP2S12, heat treatment of the as-milled sample was carried out.The optimal heat-treated Li10GeP2S12 is almost fully crystalline and possesses a room temperature ionicconductivity of 3.27 x 10(-3) S cm(-1), an over 200% increase compared to the glassy-ceramic Li10GeP2S12. These findings help provide previouslylacking insights into the controllable preparation of Li10GeP2S12 material.