Enhancing Li-S battery performance by harnessing the power of single atoms on 2D borophene

Abstract

Li-S batteries, with their high energy density and low cost, hold promise for green energy applications Nonetheless, their practical performance falls short of theoretical predictions due to the sluggish redox kinetics of lithium polysulfides (LiPS). Although attempts have been made to address volumetric expansion and enhance conductivity via porous scaffolds, considerable obstacles persist. Single-atom catalysts (SACs) represent a promising approach, facilitating atomic-level engineering and accurate characterization of reaction intermediates, thereby providing pathways to surmount these challenges. Inspired by the single-atom catalysis approach, we designed an innovative electrocatalyst including FeN₄ single-atom active sites anchored to 2D borophene nanosheets. The significant electronic coupling between Fe 3d and S 2p orbitals promotes charge transfer and improves the redox dynamics of lithium polysulfide intermediates. Moreover, the unique properties of 2D borophene, including its low volumetric mass density, superior electrical conductivity, rapid Li-ion transport, and robust binding energy with polysulfides, render it a promising choice for Li-S battery materials. The synergistic effect of robust polysulfide adsorption by 2D borophene and improved redox kinetics, enabled by the unique electronic configuration and three-dimensional architecture of FeN₄/borophene (Fe@BNS), results in outstanding electrochemical performance in Li-S batteries. The fabricated Li-S cells exhibit exceptional long-term cycle life (1180 mAh g⁻¹ at 1 C for 1000 cycles) and outstanding high-rate charge-discharge performance (790.3 mAh g⁻¹ at 1 C) with a significant sulfur loading of 6.5 mg cm⁻².