p–d orbital hybridization induced by transition metal atom sites for room-temperature sodium–sulfur batteries

For energy storage applications involving sulfur redox reactions, uniformly dispersed metal sites in sulfur hosts serve as an effective approach to facilitate electron transfer during charge and discharge cycles. In this study, we exploited a facile method to construct transitional single-atom catalysts to overcome the kinetic limitations for electron transportation in room-temperature sodium-sulfur batteries. By the synergistic effect of polysulfide adsorption and p-d orbital hybridization between catalysts and intermediates, electron-donating and electron-capturing capabilities of different atomic sites towards sulfur redox reactions are systematically revealed. Remarkably, atomic Mn-N₄ active moiety structures possess abundant unfilled antibonding orbitals, promoting p-d hybridization and leading to superior sulfur conversion reactions. This work establishes a design paradigm for single-atom catalysts in metal-sulfur batteries by linking atomic-scale electronic features to macroscopic performance. This atomic-level engineering strategy paves the way for high-energy-density room-temperature sodium-sulfur batteries, with potential extensions to other multivalent sulfur-based energy storage systems.