Study On The Ionic Liquids And Pseudo-capacitive Electrode Materials In Supercapacitors

Super-capacitors have been recognized as a new green energy storage devices, having a high power density^high energy density and long cycle life. They can be charged fast and discharged instantaneously in big current, their promising application in such fields as electric vehicle, mobile telecommunication and military force, have been attracting widespread concern all over the world. The performance and cost of the electrode material and the electrolyte are the most important factor affecting on the nature of Super-capacitor. Among them, polyaniline(PANI) and manganese dioxide having advantageous properties with raw materials readily available, easy synthesis, low cost, good chemical stability and electrical conductivity characteristics, are the research hotspot as Super-capacitor electrode materials. Ionic liquids(ILs) as Super-capacitor electrolyte having practical value is a new kind of green solvents, with wide electrochemical windows, relatively high ionic conductivity and strong in design to meet the demand of Super-capacitor operating voltage and normal running under harsh environment. This paper studies on high performance of the Ionic Liquids and pseudo-capacitive electrode materials for Super-capacitors. The main results of this dissertation are as the following:In this work, preparing different active carbon electrodes and using cyclic voltammertry (CV) measurements to test the electrochemical properties of the carbon material in different electrolytes. Mechanical physical mixing(MPM) and chemical in-situ polymerization (CIP) were used to synthesize polyaniline(PANI)/Huaxian carbon(HXC) hybrid materials, investigating the electrochemical properties by CV and galvanostatic charge-discharge(GCD) in acidic electrolyte. Then, Manganese dioxide(MnO2) was synthesized on nickel foam by using a novel unipolar pulse electro-polymerization method and to study the electrochemical behavior of it. This paper also by adding organic solvent, lithium perchlorate(LiClO4) to the [EMIm]BF4for improving the viscosity and conductivity of electrolyte in the symmetric carbon-based Super-capacitor. Results showed that:the ionic liquids is a very good Super-capacitor electrolyte, greatly enhancing the specific energy of Super-capacitor. The method of CIP was superior then MPM for the synthesis of PANI/HXC. The CV behavior exhibited the idea capacitance characteristics under different scan rates for Manganese dioxide (MnO2). We mixed the [EMIm]BF4with acetonitrile(ACN) and LiClO4, according to a certain proportion of the ratio. The mixed electrolyte had been further improved.Finally, a3V/18.5F Super-capacitor group was assembled with HXC as electrode and1M LiC104/ACN/[EMIm]BF4as electrolyte. Compared with the monomer Super-capacitor at the current density of5mA/cm2, effective electrode area of shunt capacitor was improved with the total electric capacity increased and all-in resistance decreased.