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

Abstract 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 LixHES phase. This LixHES 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.