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

TLDR: In this paper, 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, board interlayer spacing of 4.1 A (1.16 times to that of HH- rGY), and negligible volumetric expansion (< 3%) during potassiation, which are investigated by experiments and theoretical calculations.

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 D2h-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, board interlayer spacing of 4.1 A (1.16 times to that of HH-rGY), and negligible volumetric expansion (< 3%) during potassiation, which are investigated by experiments 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) and 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.