MOF-deviated zinc-nickel-cobalt ZIF-67 electrode material for high-performance symmetrical coin-shaped supercapacitors.

In this study, an MOF-derived ternary zinc-nickel-cobalt hollow polyhedron (ZNC ZIF-67) is synthesized via a facile and scalable templated method and evaluated as the electrode material for supercapacitors. Several physical methods, including XRD, EDX, SEM, TEM, and HR-TEM, are used to characterize the morphology, structure, and composition of this material, and electrochemical methods, such as cyclic voltammetry, galvanostatic charge and discharge, and electrochemical impedance spectroscopy, are also used to evaluate the electrode performance. The porous polyhedral structure of ZNC ZIF-67 with different shell compositions consisting of interconnected nanoparticles is found to play an important role in increasing the specific surface area of the material. This electrode material with interconnected nanoparticles shows an improved capacitance, giving a specific capacitance of 247F/g at a current density of 0.1 A/g when symmetrically assembled into a coin-shaped supercapacitor. The assembled supercapacitor with this material also demonstrates an outstanding rate performance and an excellent cycling stability with an average coulombic efficiency of 99% over 5000 cycles and a high energy density of 27.94 Wh/kg at a power density of 1.3 kW/kg. It is believed that this work could provide a simple strategy to fabricate nanostructured MOF-derived ternary metal oxide-based electrodes for high-performance and practical energy storage devices, including supercapacitors.