Electrodeposited ZnNiO Nanocomposite as a Bifunctional Electrode for Enhanced Performance Electrochromic Supercapacitors

Electrochromic supercapacitors (ECSCs) have emerged as promising multifunctional devices capable of simultaneously storing energy and modulating optical properties. Nevertheless, developing cost-effective electrode materials with enhanced electrochemical and electrochromic performance remains a significant challenge. In this work, a zinc oxide/nickel oxide (ZnNiO) composite electrode was successfully fabricated via a facile cyclic voltammetry electrodeposition technique for advanced electrochromic supercapacitor applications. The electrochemical behaviour of the electrode was investigated using cyclic voltammetry, galvanostatic charge-discharge, and kinetic analyses, while its electrochromic performance was evaluated through reversible colour-switching measurements. The ZnNiO electrode exhibited a high specific capacitance of 379 F/g at 10 mV/s and 153.5 F/g at 1 A/g. Kinetic analysis revealed that charge storage was predominantly governed by diffusion-controlled processes, contributing 83.86% of the total capacitance at 10 mV/s. Furthermore, the electrode exhibited a reversible colour transition from light green (0 V) to black (0.5 V), achieving an optical contrast of 20%, coloration efficiency of 64.99 cm 2 /C, and rapid coloration and bleaching times of 8.02 and 6.20 s, respectively. An asymmetric ZnNiO//activated carbon (AC) device delivered a specific capacitance of 236 F/g at 5 mV/s, an energy density of 8.96 Wh/kg at a power density of 960 W/kg, and good cycling stability, retaining 77% of its initial capacitance after 10,000 cycles. These findings demonstrate that electrodeposited ZnNiO is a promising electrode material for next-generation electrochromic energy storage systems.