Atomic Fe on hierarchically ordered porous carbon towards High-performance Lithium-sulfur batteries

Abstract

Lithium-sulfur (Li-S) battery is the promising next-generation energy storage device owing to its ultra-high theoretical energy density and low cost. Unfortunately, its practical performance is significantly hindered by the poor conductivity of sulfur, huge volume change, and soluble lithium polysulfides (LiPSs). To address above issues, single iron (Fe) atoms anchored on hierarchically porous carbon substrate configured by ordered macropores and widespread mesopores/micropores (Fe[sbnd]N[sbnd]C/OC) are synthesized and acted as carbon hosts for sulfur cathodes. Single Fe atoms in Fe-N4 moieties serve as active sites to accelerate conversion kinetics of LiPSs due to strong catalytic ability, thereby the shuttle effect being obviously restrained. Meanwhile, the trimodal-porous structure provides continuous carbon framework for enhanced electrical conductivity, ordered macroporous channels bridged by mesopores for rapid Li+ diffusion, and adequate spaces to reserve sulfur volume oscillation. Consequently, sulfur-loaded Fe[sbnd]N[sbnd]C/OC (Fe[sbnd]N[sbnd]C/OC/S) cathodes exhibit an impressive specific capacity of 1442 mAh g−1 at 0.1C and maintain the capacity retention of 89.2 % after 300 cycles at 1C. It offers fresh insights for designing efficient sulfur hosts to enhance the performance of Li-S batteries.