Enhancing Long Stability of Solid‐State Batteries Through High‐Energy Ball Milling‐Induced Decomposition of Sulfide‐Based Electrolyte to Sulfur

Metal sulfides are increasingly favored as cathode materials in all-solid-state batteries (ASSBs) due to their high energy density, stability, affordability, and conductivity. Metal sulfides often exhibit capacities exceeding their theoretical limits, a phenomenon that remains not fully understood. In this study, it reveals that this phenomenon is primarily due to the sulfur decomposition from sulfide-based electrolyte. By employing the high-energy ball milling (HEBM) technique, the deposition of sulfide-based electrolyte onto sulfur is intentionally promoted, resulting in higher charge capacities compared to the discharge capacities and surpass theoretical limits of metal sulfides. Using chromium sulfide (Cr₂S₃) as the active material, the sulfur decomposed from sulfide-based electrolyte transforms into lithium sulfide (Li₂S) after discharge, resulting in an increased capacity by ≈439.6 mAh g^-1 and improved cycling stability. Consequently, it demonstrates a specific capacity surpassing 1200 mAh g^-1 with a capacity retention of over 80% after 650 cycles, maintaining cycling stability for more than 1900 cycles and achieving a Coulombic efficiency exceeding 99.9%. This versatile HEBM approach enables the fabrication of ASSBs utilizing various transition metal sulfides, such as molybdenum disulfide (MoS₂), niobium disulfide (NbS₂), and iron disulfide (FeS₂), all exhibiting over theoretical limited capacities and prolonged cycling capabilities.