Electrochemical Performance of PbO2 and PbO2-CNT Composite Electrodes for Energy Storage Devices

In this work we report the electrochemical performance comparison of two new hybrid supercapacitors one based on graphene as negative electrode and lead dioxide thin film as positive electrode and the other with graphene as negative electrode and lead dioxide-carbon nanotube composite as positive electrode in 0.1 M KOH electrolyte. In the present work, PbO2 was synthesized using sol-gel method which is one of the promising materials for hybrid supercapacitors. The XRD confirmed the single phase of the PbO2 and the grain size is 39 nm which has been determined using Scherrer's formula. Thin films of PbO2, PbO2-CNT composite and graphene were coated on the titanium substrate by electrophoretic deposition. Further material characterisation has been carried out using SEM, TEM, XPS and electrochemical characterisation using CV, charge/discharge and electrochemical impedance spectroscopy (EIS) for obtaining energy density and power density, cyclic stability and internal resistance respectively. The present results revealed that PbO2-CNT composite/graphene asymmetric hybrid supercapacitor exhibits large specific capacitance and energy density over PbO2/graphene based system. The PbO2-CNT composite/graphene asymmetric hybrid supercapacitor exhibited maximum power density and energy density of 1200 W/Kg and 65 Wh/Kg respectively at a current density of 2 A/g. The PbO2-CNT composite/graphene asymmetric hybrid system exhibited excellent cycling stability with the capacitance retained 85% of its maximum value up to 3000 cycles.