Analysis of the Detrimental Impact of Residual Solvent in Solid Electrolyte Membranes for Sulfide All-Solid-State Batteries

Developing thin solid electrolyte membranes is critical for achieving high-energy-density batteries and typically requires a slurry-casting process. Whereas lab-scale studies generally employ vacuum drying, industrial roll-to-roll manufacturing relies on hot air drying, which can leave residual solvent in both the electrodes and the solid electrolyte membrane. Insufficient removal of this solvent can increase the cell overpotential. However, its impact on all-solid-state batteries remains underreported. In this study, we investigated the effects of residual solvent in Li6PS5Cl-based solid electrolyte membranes, quantified it by gas chromatography, and correlated the results with fast charge capability and cycle stability. The findings provide practical guidelines for optimizing solvent drying processes during the scale-up of sulfide-based, all-solid-state batteries.