Recognizing the contrasting role of N, O dual-coordinated single-atom iron catalyst in Li-S and Al-S batteries

Single-atom catalysts (SACs) have been increasingly employed to promote the sluggish reaction kinetics of metal-sulfur (M-S) batteries. Nevertheless, the structure-property relationship between coordinating elements and catalytic properties remains unexplored by far. Herein, N, O dual-coordinated single-atom iron catalysts (Fe -NO-C) were exemplified to unravel the influence of coordinating oxygen on catalytic efficiencies for lith-ium-sulfur (Li-S) and aluminum-sulfur (Al-S) batteries. Doping of high electronegative oxygen depressed the d -p hybridization of Fe-NO-C towards sulfur species as well as its catalytic activities for Li-S batteries. Interestingly, an opposite effect of coordinating oxygen was predicted in Al-S batteries. The inefficient d -p hybridization stabilized aluminum polysulfides on Fe-NO-C through dipole-dipole interactions, which accelerated Al-S con-version kinetics and improved the bidirectional catalytic performance. These findings enabled noncovalent interaction to be alternative way to access desirable catalytic effect. Guided by these design principles, advanced Al-S batteries using S@Fe-NO-C cathode exhibited a high reversible capacity of 550.1 mAh g-1 after 400 cycles and excellent high-rate capability of 352.1 mAh g-1 at 3 A g-1. This work provides valuable insights into the understanding of coordination structures of SACs and paves the way for developing superior catalysts in M-S applications.