Imine-based nickel/cobalt covalent organic framework with high rate and stability for supercapacitor

Abstract

Due to their regular pore structure, long-range order, and structural stability, COFs (Covalent Organic Frameworks) have gradually been employed as electrode materials for supercapacitors. However, owing to their two-dimensional stacking structure, poor conductivity, and the lack of effective redox-active sites, they usually exhibit inferior rate performance and cycling stability. Therefore, we design an imine-based Ni_0.7Co_0.3-COF anchored with Ni/Co redox centres at the atomic level and adjust their proportion. This approach optimizes the electronic structure and enhances the electronic conductivity and redox activity of Ni_0.7Co_0.3-COF. Ni_0.7Co_0.3-COF are grown through thin-layered cross-linking, significantly shortening both the ion and electron transport pathways. This improves the contact area between electrolyte ions and electrode materials and enhances the utilization of redox centres, thereby substantially improving the rate performance (1300 F g⁻¹ at 50 A g⁻¹) and cycling stability (72% retention after 5000 cycles) of Ni_0.7Co_0.3-COF.