Iron single atoms anchored on hierarchically porous carbon spheres as separator coating for high-performance magnesium-sulfur batteries

Abstract

Magnesium-sulfur (Mg–S) batteries have attracted increasing interest owing to their high theoretical energy density, intrinsic safety, and cost advantages. However, their practical deployment is hindered by several challenges, including the sluggish redox kinetics of sulfur species, severe polysulfide shuttle effects, and poor cycling stability. Herein, we report a separator modification strategy using single-atom iron anchored on hierarchically porous nitrogen-doped carbon nanospheres (Fe–NC) as a multifunctional interlayer. This Fe–NC coating functions both as a physical barrier to suppress polysulfide diffusion and as a catalytic interface offering abundant active sites for strong chemisorption and accelerated conversion of magnesium polysulfides (MgPSs), as evidenced by comprehensive structural, spectroscopic, and electrochemical analyses. Mg–S cells with Fe–NC-modified separators exhibit markedly enhanced electrochemical performance over those with pristine glass fiber (GF) separators, achieving an initial discharge capacity of 741 mAh g⁻¹ at 0.1 C and maintaining 248 mAh g⁻¹ after 150 cycles at 0.5 C. This work highlights the promise of atomic-level catalyst design for functional separator engineering toward high-performance Mg–S batteries.