Preparation And Electrochemical Properties Of Polyaniline/Graphene Composite

Supaercapacitor is a new type of environmentally friendly energy storage device which has large capacity, high power density, good stability and many other advantages,its performance is mainly determined by electrode materials. At present, electrode materials manily include carbon material, metal oxide, conducting polymer and their composites. Among these materials, graphene(GR) has excellent theoretical conductivity and fabulous eletrochemical stability, however, its high surface energy leads to agglomeration so its electrochemical performance is far lower than its theoretical value; polyaniline(PANI) has large specific capacity but poor cycle stability.In order to achieve complementary advantages and overcome the defects of each singer material, the preparation of high-performance PANI/GR composite is identified as feasible and promising. In this paper, GR, PANI and PANI/GR composite is prepared respectively, their morphology, structure and electrochemical performance is studied by scanning electron microscopy(SEM), transmission electron microscopy(TEM) and atomic force microscopy(AFM), X-ray diffraction(XRD), Fourier transform infrared spectrum(FT-IR), Raman spectroscopy(Raman), cyclic voltammetry(CV), constant current charge-discharge(GCD) method and electrochemical AC impedence(EIS) test.The main research content in this paper as follows:(1) Preparation of thin-layer GR is conducted by thermal expansion stripping method. The results of electrochemical test reaveals that specific capacitance of GR is178.6F/g at the scanning rate of 5m V/s and 175.5F/g under the current density of 0.1A/g. After 1000 times of charge-discharge cycles under the current density of 1 A/g, the capacitance retention of GR is as high as 93.2%, which shows its excellent electrochemical stability.(2) PANI is synthesized at-40℃, 20℃, 0℃ and 20℃ respectively within 50%(volume fraction) ethanol aqueous, the mass ratio of ammonium persulfate(APS) and aniline monomer(AN) is 1:1(APS) and the concentration of hydrochloric acid(HCl)solution, as doping acid, is 1mol/L. As a result, when the temperature reach to 40 centigrade below zero or lower, the nano-rodlike PANI particle, which could hardly reunite, appears and its open channel structure contrbitues to the high-speed movement of carrier and electrolyte ions on the base of which this article prepare the electrode slice using polyaniline synthesized at 40 centigrade and optimize the preparation process. It can be obtained from the results that when the mass ratio of PANI,conductive carbon black and PVDF is 85:5:15, the specific capacitance of the electrode reach to 316.4F/g under the scanning rate of 5m V/s and 302.4F/g under the currentdensity of 0.1A/g. After 1000 times charge-discharge cycles under the current density of1A/g, the capacitance retention rate of PANI is 31.2%, which shows a poor electrochemical stability.(3) On the basic of the optimization of polymerizaiton temperature of PANI and the preparation process of electrode slice, In situ preparation of PANI/GR composites is conducted and the paper explores the influence on electrochemical properties from the contents of the APS, GR and the concentration of HCl respectively. The results showed that the bilateral surface and edge of GR is coated by highly ordered nano-rodlike PANI particle homogeneously, which effectively refrain the GR from aggregation; the dimension of the PANI is about 20~50nm, the thickness of the GR could reach 0.83 nm approximately and the dimension of single GR size is about 2 ?m which are observed by AFM. When the concentration of HCl is 1 mol/L, the mass ratio of AN and APS is1:2, the mass fraction of GR is 10%, the bump of nano-rodlike PANI promotes the efficient transmission of charged particles, which make the composite has excellent electrochemical performance. The specific capacitance of PANI/GR reach to 507.6 F/g at the scan rate of 5m V/s, 496.7F/g under the current density of 0.1A/g and after 1000 times of charge-discharge cycles under the current density of 1A/g, the PANI/GR composite holds 89.2% of its original capacity which shows a fabulaous electrochemical stability and laids a foundation for its application in supercapacitor.