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Design of MnO2-MWCNTs Based Asymmetric Supercapacitor with Superior Electrochemical Performance and Its Application in Powering LEDs

ABSTRACT An asymmetric supercapacitor device (ASD) was fabricated using manganese oxide- multiwalled carbon nanotubes (MnO2-MWCNTs) nanocomposite as positive electrode and functionalized multiwalled carbon nanotubes (f-MWCNTs) as negative electrode. This ASD demonstrated a specific capacitance (Cs) of 47 F.g−1 at a scan rate of 2 mV.s−1 in a wide operating potential of 0-2V in 1 M Na2SO4. The energy density of the device was 14.3 Wh.kg−1 at 1 A.g−1 current density. The maximum power density obtained for the ASD was found to be 5.9 kW.kg−1 with a corresponding energy density of 7.3 Wh kg−1. The device was subjected to 20,000 galvanostatic charge-discharge cycles at a high current density of 25 A.g−1 to test its stability. The ASD retained 65% of the initial capacitance with 82% coulombic efficiency even at 20,000th cycle. Further, electrochemical impedance spectroscopic (EIS) studies indicated the charge transfer resistance (Rct) of the device as 2.6 Ω, with a phase angle of –72o, which confirmed its good capacitive behaviour. The ASD could power two red coloured LED lights connected in parallel for 6 min after it was charged to 2V at a current density of 1 A.g−1. GRAPHICAL ABSTRACT