Rational Design of Non-Noble Metal Single-Atom Catalysts in Lithium-Sulfur Batteries through First Principles Calculations.

Lithium-sulfur (Li-S) batteries with a high theoretical energy density of 2600 Wh·kg are hindered by challenges such as low S conductivity, the polysulfide shuttle effect, low S reduction conversion rate, and sluggish LiS oxidation kinetics. Herein, single-atom non-noble metal catalysts (SACs) loaded on two-dimensional (2D) vanadium disulfide (VS) as the potential host materials for the cathode in Li-S batteries were investigated systematically by using first-principles calculations. Based on the comparisons of structural stability, the ability to immobilize sulfur, electrochemical reactivity, and the kinetics of LiS oxidation decomposition between these non-noble metal catalysts and noble metal candidates, Nb@VS and Ta@VS were identified as the potential candidates of SACs with the decomposition energy barriers for LiS of 0.395 eV (Nb@VS) and of 0.162 eV (Ta@VS), respectively. This study also identified an exothermic reaction for Nb@VS and the Gibbs free energy of 0.218 eV for Ta@VS. Furthermore, the adsorption and catalytic mechanisms of the VS-based SACs in the reactions were elucidated, presenting a universal case demonstrating the use of unconventional graphene-based SACs in Li-S batteries. This study presents a universal surface regulation strategy for transition metal dichalcogenides to enhance their performance as host materials in Li-S batteries.