Synergistic Integration of Fe-N₄ Single-Atom Sites and Directionally Aligned Electrode Architecture for...

Sluggish kinetics of redox reactions and slow ion transport restrict the performance of lithium-sulfur (Li─S) batteries. Here, we fabricate cathodes containing vertically aligned porous structures hosting atomically dispersed Fe─N₄ single-atom catalyst (SAC) sites on graphitic carbon nitride (g-C₃N₄). Density functional theory (DFT) calculations suggest that the Fe─N₄ sites strengthen Li₂S adsorption, optimize electronic structure, and lower the reaction energy change associated with liquid-solid transition and Li₂S oxidation. Experimental results demonstrate that the atomically dispersed Fe─N₄ sites in the vertically aligned porous cathodes made by directional ice templating (DIT) accelerate Li⁺ ion transport and enable high sulfur loading while exposing abundant catalytic centers, resulting in strong polysulfide affinity, promoted nucleation and decomposition of Li₂S bidirectional redox catalysis, and suppressed polysulfide shuttle effect. Benefiting from this structural-catalytic synergy, the cathode delivers a high capacity of 1299.2 mAh g^-1 at 0.1 C, and the capacity is retained at 505.9 mAh g^-1 after 1 000 cycles at 0.5 C, with a low capacity decay rate of ∼0.042% per cycle. This study highlights a scalable strategy to integrate SAC with vertically aligned porous electrode architecture that promotes fast kinetics of sulfur redox in both directions and mass transport for Li─S batteries.