Study On Electrochemical Properties Of Three-dimensional Graphene/Polyaniline Supercapacitor

With the current climate change and the reduction of fossil fuels,the development of energy storage devices has become more important than ever.Due to the long life,high power density and green environmental advantages,supercapacitor,a new energy storage device,has gained much more attention by researchers.Three-dimensional graphene has a high conductivity,high specific surface area and as well-known as its pore structure.When it is used as the electrode material,the supercapacitor can achieve good rate performance and cycle stability,but lower on the capacitance and energy density.Polyaniline is widely used because of its rapid doping/dedoping property,simple synthesis and low cost.In this paper,the supercapacitor with three-dimensional graphene/polyaniline composite as the electrode material has been made.In order to increase the energy density while maintaining its good rate performance and cycle stability,we have made some effort on the material,the type of electrolyte and device structure.The main research contents are as follows:1.GP-HCl was obtained by in-situ polymerization of PANI-HCl on the surface of GH.The content of PANI-HCl in the composite was controlled by adjusting the concentration of aniline and ammonium persulfate.The effects of PANI-HCl concentration on the electrochemical properties of GP-HCl was investigated.When the content of PANI-HCl is 10%,the electrochemical performance of GP-HCl is the best.2.GP-HCl,GP-H2SO4 and GP-HClO4 were prepared using GH as the substrate and HCl,H2SO4 and HClO4 as the doping acids,respectively.The effects of three kinds of doping acids on the electrochemical properties of PANI were discussed from the aspects of surface structure,pore size distribution and crystallinity.GP-H2SO4 has the largest specific capacitance and energy density than the others.3.The voltage window can be extended to 1.6 V when using a Na2SO4 electrolyte to form a GH//GH supercapacitor.The electrochemical performance of GH//GH is tested with 1.6V voltage window.Compared with the H2SO4 electrolyte,the capacitance for Na2SO4 electrolyte based supercapacitor is slightly lower,but its maximum energy density is improved.4.The effects of active electrolyte on the electrochemical performance of supercapacitor were studied,CuCl2 and FeCl3 were used as active electrolyte,GH and GP-HCl were used as electrode material(four supercapacitors:GH@CuCl2,GP-HCl@CuCl2,GH@FeCl3 and GP-HCl@FeCl3).Compared with H2SO4 electrolyte,the specific capacitance of the active electrolyte has been improved.The voltage window of CuCl2 electrolyte supercapacitor is 0.7 V,which is smaller than FeCl3 electrolyte.FeCl3 electrolyte has a greater effect on the electrochemical performance of supercapacitors.5.The asymmetric supercapacitor GP//GH was formed,here GP-Vc and GH were used as positive and negative electrodes,respectively,then it was compared with the two symmetrical supercapacitor(GH//GH and GP//GP).The asymmetric supercapacitor can achieve a voltage of 1.6 V with ensuring electrochemical performance.Its maximum energy density is higher than the symmetrical supercapacitor.