Three-Dimensional ZnCo-MOF Modified Graphene Sponge: Flexible Electrode Material for Symmetric Supercapacitor

Developing flexible, lightweight, and portable energy storage systems have become a necessity with the advent of wearable electronic devices in modern society. We report a novel, easy, and low-cost way to fabricate flexible bimetallic metal–organic framework (MOF) doped graphene sponge (GS) free-standing materials (ZnCo-MOF/GS). The electrochemical behavior of the flexible ZnCo-MOF/GS was probed via galvanostatic charge–discharge, electrochemical impedance spectroscopy, and cyclic voltammetry. The morphological and structural studies of this material were performed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectrometry. ZnCo-MOF/GS exhibited a high specific capacitance of 695 F/g at 1.0 A/g and excellent cyclic stability with 78% retention after a 7500 cycle test in 3.0 M KOH. Furthermore, a ZnCo-MOF/GS based symmetric supercapacitor (SC) was fabricated, and this flexible device displayed a specific capacitance of 302 F/g at 1.0 A/g, an energy density of 108 W h/kg, and a power density of 5037 W/kg. Moreover, this flexible SC kept its excellent performance at severe bending conditions. We believe that our electrode with its outstanding electrochemical performance has a great potential in energy storage applications, especially for lightweight and flexible electronics.