Study On The Graphene Based Composites For Supercapacitors

Supercapacitor,stemming from traditional capacitor,is a new device for storing energy.It has exhibited interesting prospect in many application fields because of the higher energy density,proper power density,superior cycle stability,few restrictions and environmentally friendly.However,its relatively lower energy density need be improved.Generally,electrode material and electrolyte are the main points focused by researchers,such as enhancing specific surface area,reducing resistance and using ionic liquid.In this article,electrode materials is concerned by us.Therefore,studying on supercapacitor begin with its electrode material.Nano-materials,specially carbon nano-materials,exhibiting many superior physicochemical properties are always used for negative electrodes of batteries and substrate material.Graphene,a two-dimensional material is composed of monolayer graphite.Starting from the date of discovery,it has attracted wide attention since it exhibits high specific surface area,superior carrier mobility and thermal conductivity,admirable mechanical property.Therefore,it would appear good prospect in electrode materials of storing energy devices.However,some drawbacks such as poor processability,easy to restack hinder its advanced applications.Hence,graphene oxide rather than graphene is always employed.Some advantages of graphene still remain in graphene oxide,for example large specific surface area.However,some disappear,such as good conductivity.In this paper,graphene oxide was used as substrate material to synthesize CPA/RGO for supercapacitor electrode material and PANI/GO/MWCNT//A-GM composites for asymmetrical supercapacitor.The main works were presented as follows:1.Preparation of 4R-CPA/RGO and its electrochemical properties.In this section,we synthesized 4R-CPA/RGO by facile solution polymerization.Firstly,in order to obtain stable RGO solution,we used microwave reactor to reduce GO.Then,the RGO solution was employed as substrate material and adsorbed monomer by ?-?.After while,the initial composite was gained by in-situ polymerization and reduced it again to obtain the final composite.Regular CPA nano-pillar adsorbed on RGO sheets was observed by TEM and SEM.The working electrode was prepared by dipping the active material on the glass carbon electrode.Then,the electrochemical measurements(EIS,CV,GCD)proved that our composite exhibited many good electrochemical properties,such as good conductivity,high energy density,good sensitivity and so on.2.Preparation of PAGM//A-GM and its electrochemical properties for asymmetry supercapacitor.In this section,we have prepared a coherent polyaniline/graphene oxides/multi-walled carbon nanotubes composite by in-situ solution polymerization as a positive electrode of asymmetric supercapacitors.The orderly growth of polyaniline nano-dots on the graphene oxides led to the formation of the nano-ravines that can enhance ions diffusion.In addition,multi-walled carbon nanotubes surrounded by PANI connected each other,and thus the conductivity as well as the electron transfer rate for the composites were improved.The results showed that the electrode exhibited the outstanding electrochemical performances.Moreover,the KOH activated GO/MWCNT was acquired through a simple method,in which KOH was simultaneously served as flocculant and activator to generate uniform and poriferous structure.It was uesd as the negative electrode,and then an asymmetric supercapacitor(ASC)was assembled.The ASC exhibits an extended working potential,a good rate capability,an excellent cycling stability,and a decent average energy and power density.