Nanosized MnO2 spines on Au stems for high-performance flexible supercapacitor electrodes
Journal of Materials Chemistry A
Electrodes composed of ultrathin MnO 2 (thickness 5-80 nm) spines on Au nanowire (NW) stems (length 10-20 mm, diameter 20-100 nm) were electrochemically grown on flexible polyethylene terephthalate (PET) substrates. The electrodes demonstrated high specific capacitance, high specific energy value, high specific power value, and long-term stability. In Na 2 SO 4 (aq.) (1 M), the maximum specific capacitance was determined to be 1130 F g À1 by cyclic voltammetry (CV, scan rate 2 mV s À1 ) using a
... 2 mV s À1 ) using a three-electrode system. From a galvanostatic (GV) charge/discharge test using a two-electrode system, a maximum capacitance of 225 F g À1 (current density 1 A g À1 ) was measured. Even at a high charge/discharge rate of 50 A g À1 , the specific capacitance remained at an extremely high value of 165 F g À1 . The flexible electrodes also exhibited a maximum specific energy of 15 W h kg À1 and a specific power of 20 kW kg À1 at 50 A g À1 . After five thousand cycles at 10 A g À1 , 90% of the original capacitance was retained. A highly flexible solid-state device was also fabricated to reveal its supercapacitance performance.