Study of nanocomposites for supercapacitor applications

Abstract

The objective of this thesis is to study the supercapacitive behaviour of the nanocomposites. Nickel cobalt oxide nanostructures (NCO-NS) have been prepared by hydrothermal method and calcined at different temperatures. It is observed that highest value of specific capacitance has been obtained in the sample (NCO-300) calcined at 300 ºC. The composites of NCO-300 have been prepared with reduced graphene oxide (NCO-rGO) by varying the ratio of NCO-300 and rGO. Among these samples maximum value of specific capacitance is obtained in NCO5-rGO1.5. The nanocomposite of NCO-300 and polyvinyl alcohol (NCO-PVA) is also prepared. The aqueous solution of Na2SO4 is used as electrolyte for studying the electrochemical properties of all the samples. Symmetric supercapacitor is prepared by using NCO-PVA as electrodes. In asymmetric supercapacitors (ASC), NCO-300 and NCO5-rGO1.5 are used as +ve electrodes and rGO as the -ve electrode. In the ASC made up of NCO-300 and rGO, a high potential window (PW) of 2.5 V can be achieved. Further in the ASC made up of NCO5-rGO1.5//rGO, the device has responded well within the PW of 3.4 V and in the symmetric supercapacitor of NCO-PVA, the PW of 3.3 V has been obtained. Also, the solid state devices have been fabricated for both the ASC (NCO-300//rGO and NCO5-rGO1.5//rGO) and the symmetric device (NCO-PVA//NCO-PVA). As the large PW results in enhancement of energy density (Ed), so this work can be very useful for fabricating supercapacitors with high energy density. newline