Stable hexaazatrinaphthylene-based covalent organic framework as high-capacity electrodes for aqueous hybrid supercapacitors
Li Xu, Zhenhu Li, Yulin Zhang, Hanlin Guo, Meiying Zou, Haoxiang Li, Yuping Liu, Shuangyi Liu
Abstract
Covalent organic frameworks (COFs) have great potential as electrodes for aqueous hybrid supercapacitors (AHCs) owing to their designable structure and resourceful advantages. However, their low capacities and high structure instability in aqueous electrolytes limit the onward practical applications. Here, we have synthesized robust hexaazatrinaphthylene-based COF (HATN-COF) by a simple condensation between cyclohexanehexone and 2,3,6,7,10,11-hexaiminotriphenylene. The π-conjugation skeleton, porous structure, and high-proportioned imine bonds give HATN-COF sufficient electron and ion diffusion pathways for rapid reaction kinetics together with abundant exposed active sites for large capacity. Meanwhile, the formed hydrogen bond networks by ethanol molecules in frameworks improve the acid-base tolerance. As a consequence, HATN-COF delivers an exceptional specific capacity of 367 mAhg-1 at 1 A g-1 (maximum value among reported COF-related electrodes in AHCs), high rate capability with 259.7 mAhg-1 at 20 A g-1, and superior cycle durability with retaining 97.8% of its capacity even after 20,000 cycles. Moreover, the AHC, constructed by HATN-COF as the positive electrode and activated carbon as the negative electrode, exhibits a large energy density of 67 Wh kg-1 at a power density of 375 W kg-1, accompanied by outstanding cycling stability. The research presents a promising approach for designing high-performance COF electrodes for advanced AHCs.