Ion Conduction Mechanism and Interfacial Stability in Fluorine Containing Lithium Argyrodite Electrolytes for Solid-State Lithium-Sulfur Batteries

Solid-state lithium-sulfur batteries (SSLSBs) hold great potential as a safe and energy-dense storage technology for wide variety of applications. Among solid-state electrolytes, halogen-doped lithium argyrodites have become an attractive category. This is attributed to their notable features, including high lithium-ion conductivity (~10 -3 S/cm), favorable elastic stiffness (~ 30 GPa), and low flammability, making them promising candidates for enhancing the performance of SSLSBs.Despite their potential, SSLSBs based on sulfide faces challenges due to a limited atomic-scale understanding of ion-conduction, charge transport, structural evolution, and interfacial reactions such as dendrite growth, electrolyte decomposition. Here we employ a combination of density functional theory calculations, and ab initio molecular dynamics simulations to address this challenge for fluorinated argyrodites. Specifically, using accurate materials modeling, we design fluorine-containing argyrodite electrolytes that simultaneously offer enhanced (a) Li-ion conduction facilitated by unique Li-disorder induced by fluorine and other halogen co-dopants, and (b) stability against Li-anode owing to formation of a stable solid-electrolyte interface containing conductive species (Li 3 P), alongside LiCl and LiF. We will discuss these results in the context of accelerating design of novel solid-state electrolytes for long-lived, stable, and high-energy density SSLSBs.