Electrochemical Fabrication of Multicomponent Electrode for Supercapacitors

Increasing operating voltage and capacitance are effective ways to increase energy density for supercapacitors. Electrode materials with a wide energy storage potential window are urgently needed to assemble high-performance symmetric supercapacitors, which are more reliable than asymmetric supercapacitors, as the uncertainty of real working potential ranges of the cathode and anode in the operated symmetric supercapacitor can be reduced. In this work, a multicomponent electrode of Na0.2MnO2/Fe-FeOOH/MnO2/REG was fabricated which showed an extended potential window of −1.1 V to 1.25 V for charge storage. Oxygen and hydrogen evolution reactions were restrained by the manganese oxides and iron materials, respectively. The electrode displayed high specific capacitance of 1528 mF cm−2 (611.2 F g−1) at a current density of 1 mA cm−2, with excellent rate capability (87.3% and 66.7% capacitance retention upon 20-fold and 100-fold increased current). The assembled symmetric supercapacitor displayed high energy of 120.5 Wh kg−1 at a high power density of 2.35 kW kg−1.