Preparation Of Nano-MnO₂ By Solid-phase Reaction And Studies On Supercapacitor Properties

Supercapacitors, new energy storage components between batteries and electrostatic capacitors, could meet the high power need of electric vehicles when starting-up or accelerating. They could also be used as electric components and power sources for small apparatus or direct current switches. So it's of great importance to research on the relevant technology of supercapacitors to realize it industrialization. In this dissertation we conducted a series of experiments researching in electrode materials, electrolytes, assemble techniques and other related techniques with the aids of the measure methods such as cyclic voltammetric measurements, constant charge/discharge measurements, X-rays diffraction, electrochemical impedance spectroscopy, transmission electronic microscope measurements and so on.Nano-MnO₂ was synthesized by low temperature solid-phase reaction. XRD and TEM characterization suggest that the product contains α -MnO₂ and γ -MnO₂. The capacitive properties were tested by the cyclic voltammograms and the constant current charge/discharge. The cyclic voltammograms of the nano-MnO₂ show good capacitive performance. The dsicharge capacitance can reach to 153.2 F/g in (NH₄)₂SO₄ by the constant current charge/discharge curves. Using the method of adding K₂SO₄ to (NH₄)₂SO₄ solution, the corrosion degree of ion NH₄⁺ to nickel can be reduced. The result shows that the capacitance of MnO₂ electrode was reduced 15.6% and the corrosion time was increased 11 times. Compared with aqueous electrolyte, the working potential in LiNO₃/DMF could be increased to 2.0V. A maximum specific capacitance of 133.4 F/g was obtained by galavanostatic charge/discharge technique in 1mol/L LiNO₃/DMF solution. The electrolyte resistance was 10.032 Ω cm² by EIS.MnO₂ composite electrode material was synthesized by doping La₂O₃ with different ration. The conclusion is that the composite material has better capacitance character than undoped. The discharge capacity of the compositematerial is 230.3 F/g in (NH4)2SC>4 solution of 2 mol/L by constant charge/discharge measurements.In the article, by adding the modifier to the agar, a new type of supercapacitor membrane was prepared in order to improve the general performance of Agar. When the amount of PAM is 800ppm in the modified agar, the properties is excellent with the absorbency can be reached to 400.1%, the rate of rention is 335.1%, the discharge capacity is 23.4F/cm3 in the MnCVC supercapacitor.