Solvent Footprint in Wet-Chemical Processing of Sulfide Solid Electrolytes for All-Solid-State Batteries

Sulfide solid electrolytes uniquely combine high ionic conductivity, mechanical compliance, and solvent-mediated processability, positioning them at the forefront of all-solid-state battery (ASSB) development. This perspective provides a comprehensive view of liquid-phase routes across the entire life cycle─from synthesis and electrode fabrication to regeneration and potential recycling. We discuss how solvent-based processes facilitate particle uniformity, densification, and interfacial contact while imparting distinctive morphological and mechanical characteristics that are unattainable through solid-state methods. We then highlight the often-overlooked solvent footprint, whereby solvent exposure introduces persistent organic species in the form of coordinated adducts, surface-adsorbed molecules, or chemically transformed byproducts. These residues markedly alter interfacial chemistry, interparticle contact mechanics, electronic conductivity, and overall electrochemical performance, thereby necessitating residue-aware processing strategies. Finally, we outline the key challenges and future research directions for solvent-compatible and residue-conscious design, underscoring its importance in scalable manufacturing, electrochemical reliability, and sustainable ASSB technologies.