Synergistic promotion of electrocatalytic activities and multilevel descriptors in nitrogen-doped graphene supported dual-atom catalysts for lithium-sulfur batteries

Abstract

Lithium-sulfur battery (LSB) is emerging as one of the most promising candidates in energy storage systems, but its performance is greatly limited by the polysulfide shuttle and sluggish reaction kinetics. Here, we focus on 18 dual-atom catalysts (DACs) supported by nitrogen-doped graphene with three types of metal coordination environment, namely M1M2Nx (M1, M2 = Fe, Co, Ni and x = 6 or 8), for sulfur redox by using first-principles calculations. Our results show that most DACs exhibit enhanced anchoring capacity toward polysulfides and superior electrocatalytic activity via a synergistic effect between the bimetallic sites. Among them, FeNiN8 presents balanced bifunctional catalytic activities with reduced Gibbs free energy change during the conversion of Li2S4 to Li2S (1.091 eV) and decomposition barrier of Li2S (1.330 eV) to boost reaction kinetics during charge-discharge cycling, surpassing single-atom counterparts. In particular, multilevel descriptors correlating the target catalytic properties with adsorption energies of key sulfur species, ICOHP of M-S atom pairs, and the fundamental geometric and electronic properties are identified to characterize the catalytic activities of DACs. Extended DACs to other 3d transition metals further demonstrate the effective design strategy and their broad application prospects in LSBs, which contributes to a deep understanding of the origin of catalytic activity of dual-atom sites.