Honeycomb-like porous carbon embedded ferrous sulfide nanoparticles as bifunctional separator modifier by forming sulfur bonds with polysulfides in advanced lithium-sulfur batteries

To develop practical and outstanding lithium-sulfur (Li-S) batteries, it is advisable to adsorb soluble polysulfides and catalyze insoluble Li2S2/Li2S. Herein, a ferrous sulfide decorated honeycomb-like porous carbon (FeS/ HMPC) was synthesized by sulfuration strategy to act as a separator modifier in Li-S batteries. Owing to the positive migration of the Fe D-band center, the binding of FeS to polysulfides is dominated by the S bond (FeSLiPSs), which makes FeS have strong adsorption capacity for various types of polysulfides. Moreover, FeS shows the minimum energy path for the migration of typical polysulfide Li2S. In other words, it has the smallest diffusion barrier. Hence, the FeS/HMPC-PP not only realizes the efficient suppression of the shuttle effect but also catalyzes the redox reaction of polysulfides. Benefiting from the above advantages, the FeS/HMPC-PP based cells exhibit a high initial capacity of 1673 mAh g- 1 at 0.2 C and a reversible capacity of 686.7 mAh g- 1 at 3 C after 500 cycles. Moreover, the cell with a high sulfur loading of 2.4mg cm-2 demonstrates an ultra-low-capacity decay of 0.007% per cycle at 0.2 C. This work provides novel insights and promising candidates to act as a functional separator for Li-S batteries with long life and high-rate electrochemical performance.