Ultrathin Superhydrophobic Coatings for Air-Stable Inorganic Solid Electrolytes: Toward Dry Room Application for All-Solid-State Batteries

Abstract

Inorganic solid electrolytes (SEs), such as sulfides and halides, are crucial for developing practical all-solid-state batteries (ASSBs) owing to their high ionic conductivities and mechanical sinterabilities. However, their sensitivity to humid air necessitates stringent dry-room conditions during processing, which increases production costs. This study demonstrates that ultrathin (& AP;5 nm) superhydrophobic polydimethylsiloxane (PDMS) or fluorinated PDMS (F-PDMS) protective layers can enhance the stability of air-sensitive sulfide (Li6PS5Cl (LPSCl)) and halide (Li2.5Zr0.5In0.5Cl6) SEs in ASSBs. The (F)-PDMS coatings are applied using a scalable, straightforward vapor-phase deposition process, achieving high Li+ conductivity retention (92%, from 2.5 to 2.3 mS cm-1 at 30 & DEG;C). The protective layers effectively inhibit LPSCl degradation under practically relevant dry room conditions (dew point of -50 & DEG;C or -10 & DEG;C): e.g., from 2.3 to 0.97 mS cm-1 for PDMS-coated LPSCl versus from 2.5 to 0.57 mS cm-1 for bare LPSCl. Surprisingly, the superhydrophobic coatings facilitate the recovery of Li+ conductivity via vacuum heat treatment. This new phenomenon, known as regeneration, is achieved by the facile elimination of adsorbed water. Furthermore, the regenerated (F)-PDMS-coated LPSCl demonstrates significant performance in NCM||Li-In ASSB cells. These findings suggest that superhydrophobic (F)-PDMS coatings are a promising solution for practical all-solid-state technologies. Superhydrophobic coating strategies for air-stable inorganic solid electrolytes are designed using a facile vapor deposition method. The ultrathin 5 nm-thick layers suppress degradation by atmospheric air by blocking the intrusion of moisture and facilitate the recovery of Li+ conductivity by vacuum heat treatment. The layers exhibit excellent performance in dry room applications.image