Conclusions
By controlling the concentration of metallic cations and H+
,
we successfully synthesized three different MnO2 structures (a-,
b- and d-type). Different MnO2 samples were investigated as
possible active electrode materials for electrochemical capacitors in an alkaline solution electrolyte. The capacitance of the
different materials depends strongly on the crystalline structure. The SC decreases in the order a-MnO2 > d-MnO2 > b-MnO2.
a-MnO2 is more suitable as the working electrode at high
current densities. Both a- and d-MnO2 have a poor cycling
performance up to 3000 cycles, whereas b-MnO2 shows good
stability and maintains a cycling efficiency of 80% under the
same conditions.
Acknowledgements
This work was supported by the Scientic Research Fund of
Heilongjiang Provincial Education Department (12531179) and
the Program for Scientic and Technological Innovation Team
Construction in Universities of Heilongjiang (no. 2011TD010)