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

Abstract

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 Li₂S on 2D-FeS₂ were calculated using the first-principles calculation method. The activation energies for the multistep reduction of S₈ to Li₂S₄ processes were downhill, indicating that the reaction is relatively easy, except for the conversion of Li₂S₂ to Li₂S (Li₂S₂RR). Moreover, LiS is likely an intermediate for Li₂S₂RR 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 Li₂S to move quickly to the next step of the vulcanization reaction. This study confirms that the 2D-FeS₂ 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.