Fig. 1: Effects of the geometric and electronic structures of Fe–Nx on the behaviors of polysulfides.
a Configurations of Na2S4 adsorbed on Fe‒Nx, in which the pink, yellow, red, blue, and grey spheres represent Na, S, Fe, N, and C atoms, respectively. b Relationships among unsaturation degrees of Fe–Nx, binding energies, and geometric structure descriptors (γ, γ = lNa‒S/lFe‒N). c Schematic for the d-p orbital hybridization between Fe–Nx and sulfur species. d Projected DOS of different orbitals for Fe–Nx. e Projected crystal orbital Hamilton population (pCOHP) diagrams of Na–S bonds in Na2S adsorbed on Fe‒Nx. f Relationship between ICOHP values of Na‒S bonds in Na2S and electronic structure descriptor (φ, φ = eg/t2g). g Schematic illustration of Fe–Nx with high unsaturation degrees for efficient sulfur redox in Na||S batteries based on geometrical/electronic structure descriptors. The atomic coordinates of the configurations are provided as a Supplementary Data 1 file, and source data are provided as a Source Data file.
