Promoting opposite diffusion and efficient conversion of polysulfides in “Trap” Fe x C-Doped asymmetric porous membranes as integrated electrodes

The shuttling effect in soluble polysulfides results in a sluggish redox reaction and poor cycling performance of Li-S batteries. Herein, a flexible asymmetric porous carbon membrane doped with iron carbide (Fe x C) nanoparticles was designed by a facile phase-inversion method to serve as an integrated electrode for high-performance Li-S batteries, replacing the traditional Al foil current collector. The strong Li-N binding of the membranes and Fe-S chemical adsorption of Fe x C can trap polysulfides and promote their gradual diffusion into the porous carbon membrane on the opposite side of the electrolyte. The unique triple-layer-structured multifunctional membrane is ideal as a Li-S battery electrode. The upper spongy-like pores realize physical confinement of polysulfides and sulfur loading; the hierarchical macropores can accommodate volume strain and provide reservoirs for the opposite diffusion of polysulfides; and the dense conductive lower layer can replace Al foil as a current collector. Furthermore, the electrocatalytic effect of Fe x C on promoting polysulfide conversion and accelerating redox reaction kinetics ensures a smooth trapping-diffusion-conversion mechanism, which greatly suppresses the shuttle effect. The opposite diffusion and catalytic conversion of this flexible membrane is expected to have significant potential for large-scale production in practical applications.