Selecting non-metal doped FeS₂ as efficient sulfur cathode host for enhanced Li-S redox chemistry

Lithium-sulfur batteries (LSBs) are considered as the development direction of the new generation energy storage system due to their high energy density and low cost. The slow redox kinetics of sulfur and the shuttle effect of lithium polysulfide (LiPS) are considered to be the main obstacles to the practical application of LSBs. Transition-metal sulfide as the cathode host can improve the Li-S redox chemistry. However, there has been no investigation of the application of FeS₂ host in Li-S redox chemistry. Applying the first-principles calculations, we investigated the formation energy, band gap, Li⁺ diffusion, adsorption energy, catalytic performance and Li₂ S decomposition barrier of FeA_x S_2-x (A=N, P, O, Se; x=0, 0.125, 0.25, 0.375) to explore the Li-S redox chemistry and finally select excellent host material. FeA_0.25 S_1.75 (A=P, Se) has a low Li⁺ diffusion barrier and superior electronic conductivity. FeO_0.25 S_1.75 is more favorable for LiPS adsorption, followed by FeP_0.25 S_1.75 . FeP_0.25 S_1.75 (001) shows a low overpotential for the Li-S redox chemistry. In summary, FeP_0.25 S_1.75 has more application potential in LSBs due to its physical and chemical properties, followed by FeSe_0.25 S_1.75 . This work provides theoretical guidance for the design and selection of the sulfur cathode host materials in LSBs.