Regulating polysulfide intermediates by ultrathin Co-Bi nanosheet electrocatalyst in lithium-sulfur batteries

The practical application of lithium-sulfur (Li-S) batteries is hindered by the nonconductivity of sulfur, sluggish reaction kinetics and polysulfide shuttling. The liquid lithium polysulfide intermediates, connecting the Li-S battery electrochemical reaction of sulfur to Li2S, play a decisive role on battery performance. Herein, Co-Bi nanosheets intimately grown on reduced graphene oxides (Co-B-i/rGO) composite has been reported for the first time to regulate the polysulfide intermediates. The Co-B-i could not only chemically trap polysulfides but also propel the acceleration of polysulfide conversion enabled by a lower free energy and decomposition energy barrier in Li-S reaction process. Therefore, the Co-B-i/rGO-S cathode delivers a high capacity of 1334 mAh g(-1) at 0.2 C, impressive rate performance up to 8 C, outstanding cycling stability over 500 cycles at 1 C, and remarkable areal capacity of 8.3 mAh cm(-2) with a high sulfur mass loading of 9.5 mg cm(-2). The chemical binding strength, the Gibbs free energy and the energy barrier for transition state from theoretical calculations give a deep insight of polysulfide regulation by Co-B-i. (c) 2021 Elsevier Ltd. All rights reserved.