Revitalizing Sulfide Solid Electrolytes for All‐Solid‐State Batteries: Dry‐Air Exposure and Microwave‐Driven Regeneration

Abstract Processing sulfide solid electrolytes under dry‐air conditions at which certain levels of moisture are unavoidable poses challenges in the practical mass production of all‐solid‐state batteries (ASSBs). Herein, a facile microwave‐driven regeneration method is presented for Li 6 PS 5 Cl (LPSCl) degraded by dry‐air exposure, particularly after solvent treatment. While dry‐air exposure with a dew point of −40 °C for 6 h degrades the Li + conductivity of wet‐processed LPSCl from 3.33 to 2.55 mS cm −1 at 30 °C, microwave irradiation at 800 W for only 10 min restores 98.3% of the Li + conductivity of pristine LPSCl (3.26 mS cm −1 ) and maintains its electron‐insulating property. By contrast, conventional furnace heat treatment recovers only 83.8% of Li + conductivity and causes severe carbonization. Comprehensive analyses reveal that microwave heating selectively eliminates hydration layers and carbonates without inducing structural alterations or byproduct evolution. Electrochemical tests demonstrate that the microwave‐regenerated LPSCl achieves performance nearly identical to the pristine LPSCl in LiNi 0.7 Co 0.15 Mn 0.15 O 2 ||(Li‐In) cells. Its practical applicability is further validated in LiNi 0.7 Co 0.15 Mn 0.15 O 2 ||(Ag−C) pouch‐type ASSBs. This rapid, scalable, and energy‐efficient regeneration method can ensure consistent sulfide solid electrolyte performance, regardless of storage or transport history, enabling reliable large‐scale manufacturing of ASSBs.