Unlocking high-sulfur-content cathodes by an all-in-one high-entropy sulfide catalyst for all-solid-state Li-S...

Transition-metal sulfide (TMS) catalysis is a promising strategy for accelerating sulfur redox kinetics, yet its catalytic mechanisms in all-solid-state lithium-sulfur batteries (ASSLSBs) remain poorly understood. Here, two distinct catalytic failure modes are identified in conversion-type and intercalation-type TMS catalysts, namely, phase-separation-driven catalyst self-poisoning and transition-metal-migration-induced electrolyte degradation, respectively. Guided by these insights, we develop an all-in-one high-entropy sulfide (HES) catalyst that undergoes a solid-solution reaction to form a stable Li _x HES phase. This Li _x HES functions as both a dual ion-electron conductor, expanding the electrochemically active reaction zone, and an interfacial redox mediator, driving spontaneous Li₂S oxidation, thereby promoting extensive and rapid S↔Li₂S conversion. With only 3 wt% HES, the S@HES cathode (40 wt% S) achieves 93.4% sulfur utilization and 93.0% conversion efficiency. Even at 50 wt% sulfur, the cell retains a capacity of 900 mAh g^-1 at 5 mA cm^-2 (2C) over 250 cycles. Furthermore, a high areal capacity of 9.68 mAh cm^-2 is delivered under demanding conditions (8.5 mg cm^-2, 30°C), highlighting the great promise of the HES catalytic strategy for energy-dense ASSLSBs.