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, Li7–xPS6–xClx (LPSC) in particular, are receiving increasing attention. However, the instability of sulfides with H2O 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 H2O, focusing on often-overlooked H2O 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 H2O 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 H2O. This work provides valuable insights into the interactions between LPSC electrolytes and H2O, establishing a foundational framework for studying the moisture stability of sulfides.