Efficient polysulfide conversion by Fe-N/C active sites anchored in N, P- doped carbon for high-performance lithium-sulfur batteries

Lithium-Sulfur batteries have become one of the most promising energy storage systems due to their ultra-high energy density, environmental friendliness, and low cost. However, the sluggish redox kinetics of lithium polysulfide (LPS) and its shuttling effects have impeded the practical applications of Li-S batteries. Single-atom catalysts (SACs) with atomically dispersed metal-based sites have been applied as a promising candidate for electrocatalysts for Li-S batteries. Herein, we design and demonstrate a single atom Fe-N/C catalyst impregnated with N, P–doped carbon (FeN₆–NPC), N, P–doped carbon material (NPC), as well as Fe₂P nanoparticles anchored with N, P–doped carbon (Fe₂P–NPC). In-depth XANES and FT-EXAFS analyses were used to characterize the precise architecture of SACs containing Fe-N/C active sites. The electrochemical results of SACs with Fe-N/C active site configuration reveal the highest catalytic lithium polysulfide conversion compared to the NPC and nanoparticle anchored samples. In addition, the SACs enable FeN₆–NPC/S electrode to deliver a high discharge capacity of 1115 mAh g⁻¹ at 0.1 C and maintain 570 mAh g⁻¹ after 200 cycles with excellent Columbic efficiency (>99%). This work successfully develops organic-based strategies for SACs that suppress lithium polysulfide formation, improve cyclic stability, and increase Coulombic efficiency for lithium-sulfur batteries.