Artificial Byproduct Coatings through a Sublimated Sulfur Vapor Reaction to Enhance the Stability of Cathode/Sulfide Electrolyte Interfaces

Cathodes in sulfide-based all-solid-state batteries (ASSBs) can be coated with stable materials (such as oxides) to mitigate unfavorable interfacial reactions with the sulfide electrolyte. However, the chemical potential difference between these coating materials and the electrolyte leads to a nonuniform distribution of Li⁺ ions at the interface and impedes their mobility. In this study, we create a thin, uniform layer of sulfur-containing byproducts by reacting sublimated sulfur vapor with the cathode surface to minimize interfacial side reactions. The cathodes treated with sulfur vapor exhibited better electrochemical performance than pristine cathodes. The electrochemical properties could be further enhanced when the sulfur treatment was combined with Li₃PO₄ coating. The sulfur treatment can enhance the chemical compatibility between the cathode surface and sulfide electrolyte, thereby improving the interfacial stability and facilitating Li⁺ ion migration during cycling. This study presents a promising method for stabilizing the cathode/sulfide electrolyte interface, potentially accelerating the practical adoption of ASSBs.