Influence of microstucture on the charge storage properties of chemically synthesized manganese dioxide

被引:890
作者
Toupin, M
Brousse, T
Bélanger, D
机构
[1] Univ Quebec, Dept Chim, Lab Electrochim Appl, Montreal, PQ H3C 3P8, Canada
[2] Univ Nantes, Ecole Polytech, Lab Genie Mat, F-44306 Nantes 3, France
关键词
D O I
10.1021/cm020408q
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
alpha-MnO2 was synthesized by a very simple coprecipitation technique and tested as active electrode material for an electrochemical supercapacitor. The powder presents a poorly crystallized cryptomelane phase with a chemical composition of K0.05MnO2H0.10.0.15H(2)O. Different aqueous electrolytes were tested including 0.1 M Na2SO4, 0.5 M K2HPO4/KH2PO4 buffer solution, 0.3 M H2SO4, and 1 M NaOH, but interesting pseudocapacitance behavior was only observed in the case of 0.1 M Na2SO4. Further testing using this electrolyte showed that an average capacitance of 166 F/g can be reproducibly obtained within a voltage range -0.4/+0.5 V vs Hg/Hg2SO4 using a sweep rate of 2 mV/s. This interesting value is mainly due to the chimisorption of Na+ ions and/or protons at the surface of the alpha-MnO2 electrode. Nearly all the Mn surface atoms are involved in the pseudocapacitive process. Therefore, the high specific capacitance seems to be related to the high surface area of the MnO2 powder rather than intercalation of Na+ ions and/or protons in the structure of alpha-MnO2. An optimum composition of 80% of active material in the composite electrode was determined. With such a composition, the alpha-MnO2 electrode can withstand 1000 cycles with 100% capacitance retention.
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页码:3946 / 3952
页数:7
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