The Preparation And Energy Storage Mechanism Of Graphene Nanocomposite Electrode

The capacitance of the electrode is a major influence on the promotion of the energy density of the supercapacitor.Graphene with large specific surface area,good thermal and chemical stability is the ideal big theoretical specific capacity and long life as electrode material for supercapacitor.But the agglomeration in the preparation causes the lower capacity of graphene.In order to improving the agglomeration of the graphen,this paper depicts a method of preparing the composites with graphene and metal oxide to promoting the electrochemical performance.The open flower-like porous graphene/MnO₂ granules overlapping each other have prepared using the solution of oxide graphene and KMnO₄ with the foam nickel as a substrate by one-step hydrotherm.The characterization shows existence of the C-Mn bond indicting that graphene and MnO₂ not only covering but bonding.The three-electrode test demonstrating that the annealed open flower-like porous graphene/MnO₂ has the best electrochemical performance than pure MnO₂ and unannealed graphene/MnO₂ granules.The high specific capacitance of 347 F/g at 10 A/g is 2.38 times higher than unannealed graphene/MnO₂ composition in 6 mol/L KOH electrolyte and the remarkbale stability has found of annealed graphene/MnO₂.In order to further studying the energy storage characteristics of graphene composites,graphene/ZIF-67 was prepared by hydrothermal method,and the silkworm-like graphene/ZIF-67 derivative composites were prepared after pretreatment the ZIF-67.The X-ray photoelectron spectroscopy?XPS?,X-ray diffraction spectrum?XRD?and Fourier infrared spectroscopy?FT-IR?analysis indicating the ingredient of the graphene/ZIF-67ramification is the composites of graphene and CoO.The electrochemical test revealing that the graphene/ZIF-67 ramification has the best electrochemical performance.The high specific capacity of graphene/ZIF-67 ramification is 275 F/g,152 times,100 times and4.2 times higher than ZIF-67,ZIF-67 ramification and graphene/ZIF-67 electrode materials at 1 A/g in 6 mol/L KOH electrolyte.In addition,the hybrid asymmetric supercapacitor using graphene/ZIF-67 ramification as anode and active carbon as cathode shows the best energy density of 9.64 Wh/kg with the power density of 347 W/kg.In general,the capacity will be improved after compounding graphene materials.The graphene/MnO₂ composites can withstand high current density and maintain good cycle stability.The supercapacitor of the composites of graphene/ZIF-67 ramification can support excellent energy and power density.This shows promising application to prepare high performance supercapacitor using graphene/MnO₂ and graphene/ZIF-67 ramification composites.