Carbon/PbO2 asymmetric electrochemical capacitor based on methanesulfonic acid electrolyte

A new hybrid electrochemical capacitor based on an activated carbon negative electrode, lead dioxide thin film and nanowire array positive electrode with an electrolyte made of a lead salt dissolved in methanesulfonic acid was investigated. It is shown that the maximum energy density and specific capacity of the C/PbO2 nanowire system increase during the first 50 cycles before reaching their maximum values, which are 29 Wh kg−1 and 34 F g−1, respectively, at a current density of 10 mA cm−2 and a depth of discharge (positive active electrode material) of 3.8%, that corresponds to a 22C rate. This is 7–8 times higher than the corresponding maximum values reached with a C/PbO2 thin film cell operated in the same conditions. After an initial activation period, the performances of the C/PbO2 nanowire system stay constant and do not show any sign of degradation during more than 5000 cycles. For comparison, the C/PbO2 thin film system exhibits a 50% decrease of its performances in similar conditions.

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► We compare a PbO2 thin and nanowire array.
► Methanesulfonic acid is used as electrolyte.
► The cell capacity and maximum energy of C/PbO2 nanowire are 7–8 times larger than for C/PbO2 thin film.
► Stable performances over 5000 charge/discharge cycles were obtained.