Study On The Application Of Ionic Liquids And Polyaniline In Supercapacitors

Super-capacitors is a good energy storage devices, their power density and energy density are vrey high, they can be charged fast and discharged in big current. because of their potential applications as energy storage devices in many field, they have attracted worldwide research interest. Ionic liquids(ILs) is a new kind electrolyte, they have such properties an non-volatility, non-flammability, relatively high ionic conductivity and big electrochemical window, the application of ionic liquids in supercapacitors has attracted considerable interest. Polyaniline(PANI) is a kind of conducting polymers, it has advantageous properties with respect to high conductivity and low cost, is an important electrode material for super-capacitors.The properties of super-capacitors with ionic liquids as electrolyte and active carbon as electrode material were tested the cyclic voltammetry (CV) measurements showed that the working voltage of supercapacitors used ionic liquids as electrolyte can arrive 3V. galvanostatic charge-discharge tests the specific capacitance of [EMIm]BF4、[EMIm]NTf2、[BMIm]BF4、[BMIm]NTf2,etc ionic liquids. Super- capacitors with a methoxyethyl group ionic liquids electrolyte was test in different working voltage. The self-discharge behaviour of supercapacitors was tested used ionic liquids and organic electrolyte. The measurements of the self-discharge rates shows that super-capacitors with ionic liquids electrolyte has very low self-discharge rate. The impact of water content in ionic liquids to the self-discharge of super- capacitor was test.The in-situ electropolymerized-polyaniline(PANI) film (thickness:5～10μm) on SS (stainless steel) doped with various conterions ClO4-, SO42-, NO3-,BF4-, p-toluenesulfonate (TsO-) etc. was prepared. SEM(scanning electron microscopy) morphologies showed that different doping conterions have great impact on the morphology of electropolymerized PANI film, various morphologies and microstructures of porous, particle and fibrillar were observed. The cyclic voltammetry (CV) measurements of PANI-SS electrodes showed that the electropolymerized-polyaniline doped with SO42- (PANI-SO4) and ClO4- (PANI-ClO4) electrodes have more specific capacitance. Galvanostatic charge-discharge tests indicated that the specific capacitance of electropolymerized-PANI doped with different ions at a current density of 2.0 A/g was 645.6 F/g,468.3 F/g,345.8 F/g,275.6 F/g,218.6 F/g, respectively. However, after 1000 cycles, about 48% and 23% specific capacitance loss for PANI-SO4 and PANI-ClO4 were observed, indicating that the PANI-SO4 electrode was much stable than the PANI-ClO4 electrode.