Lithium-sulfur (Li-S) batteries are regarded as promising secondary energy storage devices for their high energy density and low cost. The electrochemical performance of Li-S batteries is mainly determined by the efficient and reversible conversion of lithium-polysulfides to Li2S when discharging and to S when charging. Herein, a catalytic strategy is proposed to accelerate the reversible conversion of S and the discharge products in Li-S batteries. This reversible transformation is achieved with active sites of single-atom iron on nitrogen- and sulfur-doped porous carbon (FeNSC). We prove that the synergy between atomically dispersed iron and doped sulfur accelerates the reversible electrochemical conversion reactions in Li-S batteries. The FeNSC/S hybrid cathode exhibits superior long-term cycling stability even at a high current density of 1C, with only 0.047% capacity decay per cycle over 1000 cycles. This study demonstrates a novel method for improving the conversion of polysulfides based on electrocatalysis strategies to ultimately obtain high-performance Li-S batteries.
Keywords: electrocatalysis; energy barrier; lithium−sulfur battery; polysulfide conversion; single-atom iron.