CoS-FeS heterostructures supported by N-doped carbon nanocage as efficient catalyst for lithium sulfur batteries

The sluggish redox reactions and the shuttle effect associated with lithium polysulfides significantly impede the advancement of LSBs. To solve these problems, we synthesized CoS-FeS heterostructures supported by N-doped carbon nanocage (CoS-FeS@NC). The kinetic analysis shows that the enriched heterojunctions strengthens the bonding of host with polysulfides, thus promotes the redox reaction kinetics of polysulfides. XPS analysis reveals valence state of cobalt is elevated following incorporation of iron. This increase is attributed to the transfer of electrons from Co2+/Co3+ to Fe3+. The configuration of the cationic valence electrons drives this electron transfer, which in turn improves the catalytic efficiency of the CoS-FeS@NC composites. Leveraging these advantages, the S@CoS-FeS/NC cathode demonstrates an exceptional ability to adsorb lithium polysulfides (LiPSs), along with rapid reaction kinetics and enduring stability in cycling (reversible capacity of 638 mAh g-1 at 0.2 C after 200 cycles). Remarkably, even when subjected to a charge/discharge rate as high as 1 C, the cathode sustains a capacity of 619 mAh g- 1 and it keeps 542 mAh g- 1 at 1 C after 1000 cycles at a degradation rate of merely 0.05 % for each cycle. This offers a feasible strategy to thoughtfully fabricate bimetallic sulfide heterostructures and fosters advancements in various electrochemical energy storage and conversion applications.