Strong d- Orbital Coupling of Co-C₄ Atomic Sites on Graphdiyne Boosts Potassium-Sulfur Battery Electrocatalysis

Potassium-sulfur (K-S) batteries are severely limited by the sluggish kinetics of the solid-phase conversion of K2S3/K2S2 to K2S, the rate-determining and performance-governing step, which urgently requires a cathode with facilitated sulfur accommodation and improved catalytic efficiency. To this end, we leverage the orbital-coupling approach and herein report a strong d-pi coupling catalytic configuration of single-atom Co anchored between two alkynyls of graphdiyne (Co-GDY). The d-pi orbital coupling of the Co-C-4 moiety fully redistributes electrons two-dimensionally across the GDY, and as a result, drastically accelerates the solid-phase K2S3/K2S2 to K2S conversion and enhances the adsorption of sulfur species. Applied as the cathode, the S/Co-GDY delivered a record-high rate performance of 496.0 mAh g(-1) at 5 A g(-1) in K-S batteries. In situ and ex situ characterizations coupling density functional theory (DFT) calculations rationalize how the strong d-pi orbital coupling of Co-C-4 configuration promotes the reversible solid-state transformation kinetics of potassium polysulfide for high-performance K-S batteries.