Zinc oxide/tin oxide nanoflower-based asymmetric supercapacitors for enhanced energy storage devices

Research on energy storage devices has focused on improving asymmetric supercapacitors (ASCs) by utilizing two different electrode materials. In this work, we have successfully prepared a unique material, ZnO/SnO₂ nanoflower, via the hydrothermal method. Graphene oxide (GO) was synthesized by applying the modified Hummers' technique. The ZnO/SnO₂ nanoflower was deposited on a polypyrrole (PPY) nanotube/graphene oxide composite (ZS/GP) in two steps: in situ chemical polymerization, followed by a hydrothermal method. Electrochemical properties of the prepared material nanocomposite were analyzed by applying cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques. An asymmetric supercapacitor (ASC) was constructed using ZS/GP nanocomposite as the positive electrode and Caesalpinia pod-based carbonaceous material as the negative electrode material, and its performance was investigated. As a result, the fabricated ASCs were found to have an excellent specific capacitance of 165.88 F g^-1 at 1.4 V, with an energy density of 5.12 W h kg^-1 and a power density of 2672 W kg^-1. The prepared nanocomposite material for the ASC showed a cycle stability of 17k cycles at a current density of 5 A g^-1. This study revealed that the electrode material ZS/GP nanocomposite is highly suitable for supercapacitor applications. The ASC device's extended cycle life experiments for 17k cycles produced a coulombic efficiency of 97% and a capacitance retention of 73%, demonstrating the promising potential of the electrode materials for greener as well as efficient energy storage applications while converting abundant bio waste into effective energy.