Theoretically unraveling the performance of 2D-FeS2 as cathode material for Li-S batteries

Abstract

The construction of electrode materials with high conductivity and satisfactory safety for lithium-sulfur (Li-S) batteries remains critical to enhancing the performance of energy storage devices. In recent years, two-dimensional (2D) materials with layered structures have been a hot spot for research due to their unique electronic properties and large specific surface area. As an emerging electrochemically active material, 2D-FeS2 has short ion diffusion paths and a high specific surface area. Based on theoretical calculations, we have systematically studied the performance of the 2D-FeS2 monolayer as cathode material for Li-S batteries from five aspects: obtainability of structure, thermodynamic stability, electrical, surface activity, and electrochemical properties. Simulation results show that the 2D-FeS2 monolayer structure is easy to form due to the small exfoliation energy and interlayer binding energy. The layered structure surface enhances the anchoring effect of polysulfide. Excellent stability was verified by tdynamics simulation. Additionally, the DOS results show that the 2D-FeS2 monolayer has higher conductivity, which effectively improves the mobility of Li+ and electrons. The theoretical specific capacity of the 2D-FeS2 monolayer is 446.96 mAh/g, and the lower Li+ diffusion barrier is 0.19 eV. Compared to traditional FeS2, the 2D-FeS2 monolayer has higher conductivity and stability. In brief, the 2D-FeS2 monolayer is a promising cathode material for Li-S batteries. This work opens up a new path for the application of 2D materials to new energy batteries and also deepens our understanding of 2D materials at the nanoscale.