Mechanochemical constructing ordered rhombic channels in graphyne analogues for rapid potassium-ion storage

Abstract

Constructing a new topological structure with unique ordered channels for rapid potassiation kinetics is crucial to ameliorating the inherent drawbacks of carbon anodes, arising from the large K-ion radius, such as huge volume expansion, slow diffusion rate, and poor interfacial transfer dynamics. Herein, dihydrogen- and nitrogen/hydrogen-substituted rhombic graphynes (HH-rGY, NH-rGY) were synthesized through a mechanochemical cross-coupling method using specific D 2h-symmetric tetrahalogenated organic molecules and alkynyl-containing calcium carbide as precursors. The pyridinic-N atoms in NH-rGY can efficiently manipulate electron distribution and tailor structural arrangement, endowing unique AA′-stacking mode with ordered vertical rhombic channels, broad interlayer spacing of 4.1 Å (1.16 times to that of HH-rGY), and negligible volumetric expansion (<3%) during potassiation, which are studied by experimental investigation and theoretical calculations. Instead of a common capacitive-dominated storage mechanism, intercalation-dominated K-storage is verified in rhombic graphynes by quantitative kinetics analysis. Especially, the NH-rGY electrode delivers a reversible capacity of 230 mAh g−1 at 50 mA g−1 (90.2% after 500 cycles), 97 mAh g−1 at 5 A g−1 and retains 146 mAh g−1 at 2 A g−1 after 5000 cycles, owing to outstanding structural stability and rapid in-plane and inter-layer K+ diffusion. This work proposes a universal mechanochemical cross-coupling synthetic methodology and brings new insight into the topological structure design of carbon skeletons for high-performance potassium storage.