Synergistic vacancy engineering and phosphorus doping in FeS to accelerate sulfur reduction kinetics in lithium-sulfur batteries.

Lithium‑sulfur batteries (LSBs) are regarded as a promising next-generation energy storage system due to their high theoretical energy density. However, the shuttle effect of lithium polysulfides (LiPSs) and sluggish sulfur conversion kinetics remain major bottlenecks for practical applications. Herein, we propose and implement a "vacancy and heteroatom doping dual-modulation" strategy to synthesize phosphorus-doped FeS catalysts enriched with sulfur vacancies (P-4-FeS). We reveal a volcano-type relationship between sulfur vacancy concentration and catalytic activity in the FeS system, with an optimal vacancy concentration (4-FeS) exhibiting the best catalytic performance. Further introduction of phosphorus doping effectively supports structural stability, overcoming the long-standing trade-off between high activity and poor stability. The P-4-FeS catalyst significantly enhances LiPS adsorption, charge transfer, and redox kinetics. Consequently, LSBs with the S/P-4-FeS cathode deliver outstanding rate capability (557.3 mAh g-1 at 7C) and exceptional long-term cycling stability (an ultralow capacity decay rate of 0.034% per cycle over 1400 cycles at 1C). Moreover, under a high sulfur loading of 6.0 mg cm-2 and a lean electrolyte condition (electrolyte/sulfur = 5 μL mg-1), the battery achieves a high areal capacity of 4.16 mAh cm-2 with excellent capacity retention. This dual-modulation strategy offers a versatile approach for designing highly active and stable electrocatalysts for high-energy-density LSBs.