Tuning of d-p band centers with M-A (M = Co, Ni, Cu; A = N, P, O, Se) co-doped FeS2 for enhanced Li-S redox chemistry

Abstract

The sulfur host material has both excellent conductivity and catalytic performance, which is the key to highly efficient Li-S redox chemistry in lithium‑sulfur batteries (LSBs). FeS2, as the sulfur cathode host, shows high theoretical specific capacity. However, FeS2 is still insufficient in accelerating the kinetics of lithium polysulfide (LiPS) transformation and inhibiting the shuttle effect. Using first-principles calculations, we explore the physicochemical properties of M-A (M = Co, Ni, Cu; A = N, P, O, Se) co-doped FeS2, including the formation energy, conductivity, Li+ diffusion, chemical adsorption, catalytic performance and Li2S decomposition. Co-A (A = O, P) co-doped FeS2 shows lower formation energy and lattice distortion compared to other co-doping elements. Fe0.875Co0.125O0.125S1.875 has high electronic conductivity and low Li+ diffusion barrier, followed by Fe0.875Co0.125P0.125S1.875. Fe0.875Co0.125P0.125S1.875 (001) shows great potential in accelerating the kinetics of LiPS conversion and suppressing shuttle effects due to low Δɛ↓(d–p) band center. Fe0.875Co0.125A0.125S1.875(001) is favorable for the Li2S decomposition. Overall, Fe0.875Co0.125P0.125S1.875 as sulfur cathode host has potential application value in promoting Li-S redox chemistry. This work deepens the understanding of the co-doping strategy and provides theoretical guidance for the design and development of the sulfur cathode host to improve the Li-S redox chemistry in LSBs.