Electrochemical capacitors (ECs) are promising power sources for portable electronics and hybrid electric vehicles. To solve the poor ionic conductivity, intrinsic inflammability and toxicity issues of current ECs incorporating organic electrolytes, aqueous electrolyte-based asymmetric supercapacitors (ASCs) have been attracting intensive attention recently by applying a battery-like Faradic cathode and a capacitive anode. In this presentation, we first report a facile synthesis of highly monodisperse nanostructured MnO2 flowers with averaged diameter of ~25 nm via redox reaction between KMnO4 and N-Methyl-2-pyrrolidone under mild conditions. Then neutral aqueous ASCs were assembled using these nanostructured MnO2 as cathode and functional carbon nanotubes (CNTs) as anode. These ASCs exhibits an operational window as high as 2.0 V, a highest energy density of 29.2 Wh kg-1 at a power density of 105 W g-1 and competitive rate performance. The electrochemical performances, especially the rate capacity, of these ASC devices have been improved by the monodisperse and fine MnO2 nanoflowers and intertwined CNT networks with complementary potential windows. This novel nanoarchitecture offers more accessible sites for the surface electrochemistry/adsorption and short paths for ionic diffusion/percolation, and high ionic conductivity and safety by the selected neutral aqueous electrolyte. This study demonstrated a robust synthesis route for MnO2 nanoflowers as the cathode material, but also synergistic effects of ASC components for their practical applications.

Neutral aqueous asymmetric supercapacitors with synergistically coupled MnO<sub>2</sub> nanoflowers and CNTs

246th National Meeting (2013)

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Neutral aqueous asymmetric supercapacitors with synergistically coupled MnO2 nanoflowers and CNTs

Neutral aqueous asymmetric supercapacitors with synergistically coupled MnO₂ nanoflowers and CNTs