Achieving enhanced capacitance retention in an extended potential window for pristine co-HAB metal-organic framework supercapacitors

Abstract

2D conductive metal-organic frameworks (MOFs) have garnered attention as new functional materials for energy storage devices due to their high porosity, large surface area, structural tailorability, and versatile functionality. However, their generally low conductivity has hindered their application in device applications. Herein, we present an innovative solution-processable method for the fabrication of high-performance pristine cobalt hexaaminobenzene (Co-HAB) metal-organic framework (MOF) supercapacitors. The Co-HAB electrodes were effectively deposited onto nickel foam substrates using electrophoretic deposition (EPD). The EPD induced a layer-by-layer assembly mechanism for the Co-HAB nanosheets, which resulted in a binder free MOF-based symmetric supercapacitor that demonstrated superior electrochemical performance in a wide potential window of 0.0–1.2 V. Notably, the obtained Co-HAB MOF supercapacitors exhibited an impressive conductivity, operating at ultra-high charge-discharge rates of up to 4000 mV s⁻¹, and achieved an outstanding areal specific capacitance of 13.77 mF cm⁻². Furthermore, the Co-HAB supercapacitors exhibited remarkable long-term cycling stability, with 105 % of capacitance retention after 10,000 cycles, marking the best retention reported for an MOF to date. The outstanding performance of the Co-HAB supercapacitor can be attributed to the binder-free EPD process and the conductive 2D MOF nanosheets featuring abundant nanopores, which facilitate efficient electron transfer and fast ion diffusion. These encouraging results suggest a promising avenue for exploring pristine conductive MOFs as functional materials for high-performance supercapacitors and other energy storage solutions.