DFT and AIMD studies on the conversion and decomposition of Li2S2 to Li2S on 2D-FeS2

• The 2D-FeS 2 substrate is capable of reducing the activation energy of the polysulfide conversion reaction. • LiS is predicted to be an intermediate in the conversion of Li 2 S 2 RR. • Li 2 S is more dynamically stable than Li 2 S 2 on the 2D-FeS 2 surface. • The Li 2 S decomposition energy barrier is 0.16 eV on the 2D-FeS 2 surface, aiding in the next conversion of Li 2 S. Anchoring polysulfides to prevent their shuttling and dissolution into the electrolyte of Li-S batteries has been extensively studied. Whereas, the sulfur reduction reaction kinetics and the conversion process of lithium polysulfides are still unclear. In this study, the transformation of LiPSs and the decomposition of Li 2 S on 2D-FeS 2 were calculated using the first-principles calculation method. The activation energies for the multistep reduction of S 8 to Li 2 S 4 processes were downhill, indicating that the reaction is relatively easy, except for the conversion of Li 2 S 2 to Li 2 S (Li 2 S 2 RR). Moreover, LiS is likely an intermediate for Li 2 S 2 RR conversion, with optimal adsorption strength and low activation energy using the computational hydrogen electrode (CHE) approach. The dynamic results indicate that the lower decomposition barriers enable the deposited Li 2 S to move quickly to the next step of the vulcanization reaction. This study confirms that the 2D-FeS 2 cathode material significantly contributes to the electrocatalytic reaction and shows promise in addressing the challenges of Li-S batteries by reducing the activation energy during the conversion process in the future.