Preparation And Electrochemical Properties Of MnO_x-based Composites For Supercapacitor Electrode Materials

The work of compound modification on the MnOxmaterial was conducted to makeup their limit using as supercapacitor electrode material.The microstructure, morphology and chemical composition were characterized byX-ray diffraction, scanning electron microscopy and N2absorption/desorption test. Cyclicvoltammetry(CV), electeochemical impedance spectra(EIS) and galvanostaticcharge/discharge measurements were applied to investigate the electrochemical propertiesof the materials.A simple liquid phase method was used to compound Ni(OH)2which is in naturegood conductor for proton to MnO2.The composite of MnO2/Ni(OH)2with3%molcontent of Ni(OH)2prepared in liquid under20oC for2h is constituted by tinynanoparticles which slightly aggregate, forming certain hole structure. The specific surfacearea and pore size distribution of the composite was132.89m2/g and6~8nm, respectively.The composite exhibits the specific capacitance value of412F/g at0.5A/g and excellentcapacitance retention ability that the electrode could maintain nearly100%of the initialspecific capacitance after5000cycles.MnO/Ni/C composite was prepared using citric acid as carbon resourse and theMnO2/Ni(OH)2as precursor. It has been found that the material obtsined under700oC fortemperature,2h for reaction time and2%mol content of Ni in the precursor in N2atmosphere displays the specific capacitance value of423F/g at0.5A/g. By recycled1500times, the stability of the material was also proved to be very good. XRD analysisshows that the as-synthesized powder have amorphous carbon and Ni exists in the MnO inthe form of solid solution or independent phase. The SEM obsevetion reveals theaggregated nanoparticles. The composites obtained by Mn(OH)2/Ni(OH)2precursordisplay higher specific capacitance with increasing content of Ni.Targeted on MnO/C, polyacrylamide(PAM) was added into active material andpolytetrafluroethene(PTFE) during electrodes preparation to change the constituents ofelectrolyte in and near the electrodes, perfectig the electrochemical properties of thematerial. The electrode prepared with mass ratio PAM:PTFE=1:1has the big specific capacitance value of572F/g at0.5A/g and slow capacitance decay within200cycles.Meanwhile, it is found that proper amount of potassium polyacrylate(PAAK) and sodiumalginate also ease the capacitance decay.