Strong d−π 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−π coupling catalytic configuration of single-atom Co anchored between two alkynyls of graphdiyne (Co-GDY). The d−π orbital coupling of the Co–C4 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−π orbital coupling of Co–C4 configuration promotes the reversible solid-state transformation kinetics of potassium polysulfide for high-performance K–S batteries.