Asymmetrically Coordinated Single-Atom Ni Catalysts on Curved Supports for Efficient Sodium–Sulfur Batteries

Developing efficient single-atom catalysts (SACs) is crucial in alleviating the shuttle effect of sodium polysulfides (NaPSs) and accelerating the sulfur redox reaction kinetics for sodium-sulfur (Na-S) batteries yet remains challenging. Herein, we design and develop a type of single-atom Ni catalyst with an asymmetric Ni-N₃S coordination structure supported on curved carbon layers (cNi-N₃S/C) for Na-S batteries. Experimental and theoretical calculations reveal that the synergistic effect of the curvature and the asymmetric Ni-N₃S coordination induce a localized charge distribution around the Ni centers. The regulated electronic structure with upshifted d-orbital center accelerates the charge transfer, strengthens adsorption energy, and enhances sulfur redox reaction kinetics in Na-S batteries. The resultant Na-S batteries incorporated with cNi-N₃S/C delivers a capacity of 422 mAh g^-1 at 3.0 C after 2500 cycles and a low-capacity decay rate of only 0.021% per cycle. This work provides valuable insights for developing efficient SACs for Na-S batteries.