The Role of Chlorine Content in H₂O Adsorption and Reactions on Argyrodite Sulfide Electrolytes

Sulfide electrolytes are considered to be key materials for high-performance all-solid-state batteries. Chlorine-rich lithium argyrodite sulfides, Li 7– x PS 6– x Cl x (LPSC) in particular, are receiving increasing attention. However, the instability of sulfides with H 2 O remains a major issue, and the influence of the chlorine content on moisture stability is not well understood. This study investigates LPSC electrolytes with varying chlorine contents to explore their interaction mechanisms with H 2 O, focusing on often-overlooked H 2 O adsorption. A series of techniques, including adsorption energy calculations, dynamic vapor sorption, in situ Raman spectroscopy, and solid-state nuclear magnetic resonance, were employed. The degradation product LiCl accelerates H 2 O adsorption when the atmospheric vapor pressure exceeds that of saturated LiCl aqueous solution. Under low humidity, LiCl promotes the conversion of thio-phosphates, enhancing their reactivity with H 2 O. This work provides valuable insights into the interactions between LPSC electrolytes and H 2 O, establishing a foundational framework for studying the moisture stability of sulfides.