Synthesis And Electrochemical Performances Of Electrode Materials For Supercapacitor

Supercapacitor is a new energy storage device.Because of its rapid charge-discharge energy storage,high power density,maintenance free,long cycle life and friendly to the environment,supercapacitor has focus scientists interest all over the world.The most important factors which influence on the capacitor performances are electrode materials and electrolyte solution.How to improve the capacitance value and power density is the point of research.In order to investigate the relation between microstructure of the material and the capacitor behavior,mesoporous carbon and carbon spheres were prepared.Base on the study above,ordered mesoporous carbon(OMC) is added into MnO₂ material to form MnO₂/OMC composite,after that the capacitance value will be increased because of the pseud-capacitor effect.Firstly,mesoporous silicas were selected as templates,furfuryl alcohol as carbon precursor.Mesoporous carbons with different pore structure were synthesized via nanocasting pathway.The mesostructures of MCs were analyzed by X-ray diffraction,Transmission electron microscope and nitrogen sorption,the results show that the prepared carbons are mesoporous carbon.The electrochemical testing results show that the pore geometries in ordered mesoporous carbons should be considered as one of the crucial factors affecting the electrochemical performance of a porous carbon.At a fixed loading current density,the straighter the open porous channels are,the higher the capacitance will be.Mesopore structure plays an important role in improving the utility of specific areas.Carbon sphere was synthesized via self-assemble method,dihydroxybenzoic acid and formaldehyde as the polymer precursors,lysine as catalyst,and alcohols as solvent.After polymerization,the sample was then carbonized under N₂ atmosphere.It was found out that the resultant carbons have high specific surface area and uniform spherical shape and dispersion.The solution influences on the carbon shape and dispersion.The obtained polymer spheres were subject to ion-exchange with Fe³⁺ to incorporate functional ion species. Followed by carbonization step,hollow carbon spheres with graphitized nature were obtained. The electrochemical research results show that carbon spheres with high microporocity and specific surface area represent well capacitive performances.a-Manganese dioxide was synthesized by liquid-decomposition method using potassium permanganate(KMnO₄) and manganese acetate(Mn(Ac)₂)as reactants.The electrochemical performances of as-synthesized a-MnO₂ were tested by cyclic voltammetry method in different electrolyte solution.It showed that a-MnO₂ exhibited nearly idea capacitance behavior in 0.5 M Na₂SO₄ solution and the determined capacitance was 145 F·g^-1.In order to further improve the specific surface area and conductivity of a-MnO₂ certain amount of ordered mesoporous carbon(OMC) was added to form MnO₂/OMC composite.The influence of amount of OMC on the capacitance of MnO₂/OMC anode was investigated.When 20 wt% of OMC was added,the MnO₂/OMC anode materials exhibited the optimal electrochemical behavior and with good stability,the capacitance can reached to 182 F·g^-1.