Propelling polysulfides conversion in lithium-sulfur batteries via separator modification with nitrogen-doped porous carbon nanosheets decorated by iron carbide nanoparticles

The propensity of lithium polysulfides (LiPSs) to dissolve in electrolytes and shuttle between anode and cathode during cycling limits the practicality of lithium-sulfur batteries (LSBs). To overcome these issues, improving adsorption of LiPSs and enhancing catalytic effects to promote LiPSs conversion have been considered promising solutions, which can increase the utilization of sulfur species. In the current study, iron carbide nanoparticles incorporated in N-doped porous carbon nanosheets (Fe₃C/CNS) have been fabricated by pyrolyzing mixed precursors. The modified separator with Fe₃C/CNS coating layer primarily serves two functions: 1) Fe₃C/CNS coating layer could function as a physical barrier and adsorbent to anchor LiPSs, and 2) Fe₃C nanoparticles could work as electrocatalysts to promote redox conversion of LiPSs. Experimental results showed that a coin cell with Fe₃C/CNS modified separator and a cathode containing sulfur content at 81 wt% displayed excellent discharge capacity, good cycling stability, and low polarization voltages during the cycling process. Specifically, the coin cell achieved a reversible discharge capacity of 1050.6 mA h g⁻¹ at 1C and maintained a capacity of 640.5 mA h g⁻¹ over 500 cycles at a decay rate of 0.078 % each cycle.