Abstract:

The development of highly efficient catalysts for anchoring lithium polysulfides (LiPSs) and facilitating the Li₂S redox process is crucial for advancing high-performance lithium-sulfur (Li-S) batteries. In this work, we introduce single-atom 3d transition metals anchored on V₂NS₂ MXene substrates (V₂NS₂-T, where T = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) as host materials to enhance the electrochemical behavior of Li-S batteries. By using density functional theory calculations, we demonstrate that all ten systems exhibit moderate adsorption strength toward LiPSs, effectively suppressing their dissolution and shuttling. Among them, V₂NS₂-Cr and V₂NS₂-Zn show the lowest Gibbs free energy barriers for the sulfur reduction reaction during discharge (0.15 and 0.17 eV, respectively). In addition, three V₂NS₂-T configurations exhibit impressive catalytic activity toward Li₂S decomposition during charging, reducing the energy barrier from 0.66 eV (pristine V₂NS₂) to 0.27 eV (V₂NS₂-Cr), 0.27 eV (V₂NS₂-Fe), and 0.28 eV (V₂NS₂-Mn). Based on these results, the V₂NS₂-Cr monolayer is identified as a promising sulfur host material because of its fast charge/discharge kinetics. Moreover, we develop an energy-based ΔE descriptor to reduce the computational cost associated with determining Li₂S decomposition barriers. This work provides valuable insights for designing high-potential MXene-based sulfur hosts and other two-dimensional conductive anchoring materials for Li-S batteries.

Key words: Li-S batteries, Single-atom catalyst, Mxene, Polysulfides conversion, Decomposition kinetics