Internal Asymmetric Tandem Supercapacitor for High Working Voltage along with Superior Rate Performance

An asymmetric tandem supercapacitor (ATSC) is fabricated for the first time by using a unique hybrid nanocomposite for a wider working voltage. The as-fabricated flexible ATSC displays a much higher working voltage of 4.5 V and hence efficient energy density as well as power density, which are 61% and 33% higher than those of the single asymmetric supercapacitor, respectively. The ATSC displays high capacitance stability over large working voltage of 4.5 V with 97% capacitance retention after 5000 charging–discharging cycles. In addition, a stable capacitive response is maintained during the flexible bending, and a constant capacitive response is maintained even at a much higher scan rate of 5000 mV/s. Moreover, the ATSC could be easily coupled with a photodetector to provide stable power during the detection of multiple illumination signals. Therefore, results suggest that ATSCs are a promising energy storage device with efficient power and energy density and a much wider working voltage of 4.5 V.