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MnO_2 based supercapacitor electrode materials Preparation and Properties

Author: PengBo
Tutor: HuangKeLong
School: Central South University
Course: Applied Chemistry
Keywords: supercapacitors MnO2 chemical co-precipitation electrolyte
CLC: TM53
Type: Master's thesis
Year: 2005
Downloads: 429
Quote: 11
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Abstract


In this dissertation, Amorphous hydrous MnO2 were successfully synthesized by chemical co-precipitation reaction between KMnO4 and Mn（Ac）2·4H2O and it’s physical properties and electrochemical properties were investigated.The experiment results showed that the optimal pH value was 1.0,the optimal reaction time was 6 hours,the optimal drying temperature was 100℃ and the drying time was 6 hours. Moreover, the crystal structure of the synthesized sample is mainly α -MnO2 · nH2O by XRD. SEM result showed that the shape is amorphous spherical material.Electrochemical properties of the resultant were investigated by testing the charge/discharge curves and cyclic voltammetrys of a three electrode system in different electrolyte, in which working electrode was made by the product. We founded that the manganese dioxide electrode has a good electrochemical capacitor performance and high reversibility in the neutral electrolyte. Cyclic voltammetrys showed the electrode has the best capacitor performance in 0.5mol/L Na2SO4 solution and -0.20.9V（vs.SCE） potential range and the specific capacitance contains to 160F/g. By 5mA/cm2 constant current charge/discharge in 0.5mol/L Na2SO4, MnO2 electrode can provide a discharge specific capacitance of 180.2F/g, charge/discharge efficiency of 95.3%,which is the highest of all the other neutral electrolytes.MnO2/activated carbon composite electrode materials were also prepared by chemical co-precipitation method. The results show that MnO2/activated carbon composite electrode materials have better electrochemical kinetic reversibility and ideal capacitor performance than those of α -MnO2 · nH2O of activated carbon electrode by CV, alternating current impedance and constant current charge/discharge tests. The specific capacitance of composite electrodes keep constant with increase of active material.The basic capacitance expression of pseudocapacitors is deduced. Based on planar model and porous model, the impedance andcapacitance equations of supercapacitors are obtained.In this dissertation, our creative and innovational research in chemical co-precipitation reaction, neutral electrolyte, MnCVactivated carbon composite electrode materials and so on gives some significative results, we hope that will give some elicitation for the further investigation of supercapacitors, although there are still something needed given more research, such as composite electrode of MnO2N new current collector > new electrolyte.

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CLC: > Industrial Technology > Electrotechnical > Electrical > Capacitor
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