The Application Of Three-dimensional Reduced Graphene-based Composites Prepared By Plasma Treatment In Supercapacitor

Supercapacitors,as a kind of energy storage device between batteries and ordinary capacitors,have many advantages of high power density,fast charge and discharge rate,stable cycle life and feasible operation.The key to achieving high power and energy density is to develop novel electrode materials with high performance.At present,the electrode materials of supercapacitors mainly include carbon-based materials,transition metal oxides and conducting redox polymers,etc.Among these materials,reduced graphene oxide（GO）was considered as one of promising double layer capacitors materials for its outstanding properties.However,the stacking composition and low specific capacitance of two-dimensional graphene limited its application in supercapacitors.As for pseudocapacitive materials,manganese dioxide（MnO₂）and Fe₃O₄ are attracting candidates because of their low cost and enhanced electrochemical performance.While the further enhanced performance was hindered by their too large internal resistance.In our work,three-dimensional graphene/MnO₂ and three-dimensional graphene/Fe₃O₄ were selected as the composite materials of supercapacitor,respectively.3D network structural composite materials was synthesized by combining 3D graphene and transition-metal oxides（MnO₂ and Fe₃O₄）,in which the former plays the role of bearing material in the composite for its high surface area and excellent mechanical strength,and the latter has high pseudopotential.The aim of our work is to explore the supercapacitor composite materials with excellent electrochemical performance by optimizing the preparation process.In this paper,graphene oxide（GO）was prepared by modified hummers method and three-Dimensional（3D）graphene was prepared by freeze-drying method.The structure,morphology and electrochemical performance of two composite materials-3D graphene/MnO₂ and 3D graphene/Fe₃O₄-were studied,which were prepared by plasma treatment and traditional hydrothermal method,respectively.The results showed that,plasma treatment has greatly reduced the agglomeration of graphene,and the electrochemical performance of the composite electrode material has also been improved.The advantage of NG/MnO₂ electrode was obvious compared with graphene/MnO₂ prepared by traditional hydrothermal method,such as improved electrochemical property and better cycling stability,and this result is also compliant to the result of NG/Fe₃O₄ and RGO/Fe₃O₄.The specific capacitance of NG/MnO₂ at the scan rate of 5 mVs^-1(393Fg^-1)is 151%higher than that of RGO/MnO₂(260 Fg^-1).The specific capacitance of NG/Fe₃O₄ at the scan rate of 5 mVs^-1(380 Fg^-1)is 150%higher than that of RGO/Fe₃O₄(253 Fg^-1).We found that the plasma treatment not only improved the specific capacitance of composite materials,but also improved their other electrochemical properties including cycle stability.