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

Abstract

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. <i>In situ</i> and <i>ex situ</i> 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.