Preparation And Electrochemical Performances Of Composite Materials For Supercapacitor

Recent years, electrochemical capacitors as novel devices for energy storage, which fill the gap in the power density between batteries and dielectric capacitors, have attracted tremendous attention.Having a higher energy density than conventional capacitors, higher power density than batteries and cycle life, it have faster charge and discharge speed, higher storage efficiency, good temperature characteristic, green environmental protection, etc. Research and development of high performance, low cost of electrode material is the core content of the research task. Various carbon material, transition metal oxides and conducting polymers can be used for supercapacitor materials. Composite materials selected as electrode material because of the existence of synergistic effect, we can obtain efficient, low cost and improve the electrochemical performance of composite materials at the same time.Take the high abundance of natural manganese dioxide and low price into consideration, amorphous manganese dioxide is preferred as one of the most development potential of the electrochemical capacitor electrode material. Among the conductive polymer materials, Polypyrrole, due to its high conductivity, good oxidation stability, simple synthesis and easy to operate and the environment advantages, have a broad application prospect in photoelectric material, in anti-corrosion, polymer battery, especially biological sensors and other fields. Meanwhile, Silver has the highest conductivity, in all the elements are often used to improve the electrical conductivity of the composite materials, improving the properties of the material.In this paper, we discuss the preparation and modification of silver particles, polypyrrole and manganese oxide composite material and their electrochemical properties:(1)Study the MnO2/PPy composites via in-situ chemical polymerization for supercapacitor electrode material. Firstly, prepared by chemical oxidation method under different conditions of polypyrrole, we discusse the temperature,reaction time and oxide dosage on the influence of the polypyrrole.Under the influence factors of cross correlation filter out the most suitable reaction conditions:reaction temperature 0℃,the reaction time of 6 h, the antioxidant content of ferric trichloride and the molar ratio of 3:1 of pyrrole, drying chamber and electrode preparation temperature is 80℃. SEM tests find PPy chains show hemispherical particles in series and the accumulation state. When cyclic voltammograms test in 1 mol/LNa2SO4 electrolyte with a scanning rate of 2 mV/s, the specific capacitance is 256.9 F/g, and showed good cycle stability. On the basis of using chemical oxidation of MnO2/PPy composites, prepared by XRD, SEM characterization of morphology structure, PPy coating on the surface of MnO2, MnO2 PPy composites show some of the amorphous structure and core-shell structure. Electrochemical performance test results show that PPy/MnO2 composite materials circulation volt-ampere curve shows the characteristics of good rectangle, also showes a typical capacitance behavior. MnO2 content when the mass fraction of 30.5%, the volume of MnO2/PPy composites reach 204.3 F/g, the optimal cycle capacity retention 400 times still keep 96.5%.(2) By chemical oxidation method and compare the different kinds of PPy/Ag composites preparation path, the presence of sodium borohydride can’t play a positive role in the electrochemical properties of composite materials, while the sodium citrate can successfully implement stability and reduction of silver ions. The silver precursor of silver nitrate content is influenced by the change of composite material, determine the pyrrole monomer:silver nitrate, the molar ratio of sodium citrate was prepared when 12:13, PPy/Ag composites present obvious monodisperse microspheres structure, metal ions, uniform distribution in the PPy/Ag, improve the conductivity of the material.Galvanostatic charge curve is close to triangle, has good symmetry, good capacitive..PPy/Ag PPy, on average, than in 0.1 A capacitance in g is 315.8 Fg-1.The highest energy density when 50 W Kg-1 is 43.9 Wh Kg-1, then 0.5 KW kg-1 remains 30.5 Wh Kg-1, the same test condition of PPy only keep Wh in 21.3 Kg Wh-1 and 16.5 Wh Kg-1, showing good power density characteristics.(3) In order to further improve the electrochemical performance of super capacitor, we tried different methods for the preparation of ternary composites via in-situ chemical polymerization.Preparation solution from three of the morphology structure of the ternary composites and electrochemical testing results show that the synthesis of use synthesis Ag/ PPy then MnO2 method can obtain relatively good composite materials, keep good shape and morphology as PPy and Ag/PPy, maintain half spherical granular structure. In 1 mol/LNa2S04 electrolyte, when cyclic voltammograms test with a scanning rate of 2 mV/s, the specific capacitance is 168.8 F/g.The PPy, MnO2, PPy/MnO2, PPy/Ag, and PPy/Ag/MnO2 materials are characterized by X-ray diffractometry and Scanning electron microscopy. Their electrochemical properties are investigated using cyclic voltammetry, chrono-potentiometry, charge-discharge tests and life test The specific capacitance is calculated from galvanostatic chargeedischarge cycling experiments.