Blocking polysulfides with a Janus Fe3C/N-CNF@RGO electrode via physiochemical confinement and catalytic conversion for high-performance lithium–sulfur batteries

Abstract

Lithium–sulfur batteries (LSBs) have shown great potential for application in high-density energy storage systems. However, the performance of LSBs is severely hindered by the shuttle effect and the sluggish reaction kinetics of lithium polysulfides (LiPSs). Here, a Janus Fe₃C/N-CNF@RGO electrode consisting of a 1D Fe₃C-decorated N-doped carbon nanofibers (Fe₃C/N-CNFs) side and a 2D reduced graphene oxide (RGO) side was applied as a free-standing carrier for the Li₂S₆ catholyte to improve the overall electrochemical performance of LSBs. The Fe₃C/N-CNF layer endows the cathode with strong chemisorption abilities for LiPSs and accelerated the redox kinetics via catalyzing the conversion of LiPSs. The 2D RGO sheets serve as a microscopic physical barrier and further resist the shuttling of LiPSs. Like a hunter's trap, behind the trap lies a net. Moreover, the 3D hierarchical conductive network based on 1D N-CNF and 2D RGO sheets enables fast electron transfer. Based on the synergetic effects of chemical immobilization, catalytic abilities, and a physical barrier in a 3D conductive network, LSBs with optimal Fe₃C/N-CNF@RGO electrodes exhibit robust long-term cycling stability (a decay rate of only 0.0089% per cycle at 0.5C for 300 cycles), superior rate capabilities (821.7 mA h g⁻¹ at 2.0C), and stable cycling performance at high sulfur loading (6.29 mg cm⁻²). This work defines an emerging viewpoint relating to the design of novel sulfur carriers with multiple synergistic effects for application in LSBs.