Tailoring of FeP nanoparticles and Fe single atoms on N, P co-doped porous carbon nanosheets to boost catalytic activities in lithium–sulfur batteries

The shuttle effect and sluggish redox kinetics of lithium polysulfides (LiPSs) limit the practical application of lithium–sulfur batteries (LSBs), causing rapid capacity fade and poor cycling performance. Transition-metal phosphides (TMPs) are considered promising catalysts for LSBs because they improve conductivity and catalytic activity. However, the catalytic efficiency of TMPs is often restricted by nanoparticle size, which limits the number of exposed active sites. In this study, FeP nanoparticles and isolated Fe single atoms supported on N, P co-doped porous carbons (Fe-NPCs) were synthesized using a simple self-assembly method followed by pyrolysis. In addition, multi-walled carbon nanotubes (MWCNTs) were also incorporated to enhance electrode conductivity. The unique morphology of Fe-NPC-CNT with MWCNT incorporated hierarchical porous structures provide abundant active interfaces for LiPSs conversion as well as rapid Li-ion transfer kinetics. Moreover, by adjusting the Fe precursor ratio, a synergistic coexistence of FeP nanoparticles and Fe single atoms significantly enhanced polysulfide conversion kinetics and suppressed the shuttle effect. As a consequence, the [email protected] Fe-NPC-CNT electrode demonstrated higher electrochemical performances with a discharge capacity of 1186.8 mAh g⁻¹ and retained a rate capacity of 179 mAh g⁻¹ at 2.0 C. Furthermore, the cathode exhibited a capacity retention of 55.7 % after 300 cycles and 74.3 % after 200 cycles with a high sulfur loading of 3.3 mg cm⁻².