A Versatile InF3 Substituted Argyrodite Sulfide Electrolyte Toward Ultrathin Films for All-Solid-State Lithium Batteries

Abstract

All-solid-state lithium batteries (ASSLBs) incorporating sulfide solid electrolytes capture great attention due to their intrinsic safety features and high energy density. Nevertheless, the implementation of sulfide solid electrolytes faces significant challenges, including moisture sensitivity, narrow intrinsic electrochemical windows, and excessively thick solid electrolyte layers. Here, the substitution of In for P and F for Cl in argyrodite sulfide Li_5.7PS_4.7Cl_1.3 is presented. With appropriate elemental substitutions, the Li symmetric cells exhibit a high critical current density value of 2.5 mA cm⁻² and deliver prolonged plating/stripping over 1000 h at 1 mA cm⁻² and 25 °C. Further, the Li_5.82P_0.94In_0.06S_4.7Cl_1.12F_0.18 displays high chemical stability toward organic solvents, which is further demonstrated by the density functional theory (DFT) calculations. Using polyisobutylene as a binder, a uniform sulfide film (35 µm) is prepared by slurry casting and hot pressing process, delivering a high ionic conductivity of 1.4 mS cm⁻¹ at 25 °C. Coupled with FeS₂ and LiCoO₂ cathode, the all-solid-state lithium metal cell exhibits a long cycling life and excellent rate performance. This study provides a design strategy and reveals the importance of high-performance sulfide SEs in the scalable production of sulfide film.