Feasibility of nickel oxide as a smart electrochromic supercapacitor device: A review

Smart and multifunctional devices are gaining interest in the scientific community as technological advancements increase as per the requirements of society. The need for renewable and sustainable energy has increased as growing pollution and urbanization started affecting the environment. The reliance on renewable energy and its intermittent nature forced scientists to focus on energy storage systems that can fulfill the requirements as per demand. Supercapacitors can fill the gap between batteries and fuel cells with capabilities of high energy as well as power density. The electrochromic supercapacitors which can store energy with color-changing abilities make them multifunctional and reduce production costs to be spent on individual devices. The bifunctionality of the electrochromic supercapacitor is possible due to their similar device structure and working principle. Nickel oxide is an anodic oxide with the ability to show color modulation from fully transparent to dark brown with a high theoretical capacitance value, making it capable of being used as a bifunctional electrochromic energy storage electrode for a variety of applications. In this article, all the basic terms regarding electrochromism and supercapacitors with performance evaluation are discussed first. The next section covers the progress of NiO-based electrochromism, electrochromic energy storage electrodes, and devices in detailed analysis. This report will highlight NiO-based literature published in this field along with performance statistics which can be used to develop new and compatible strategies to meet real-world applications in wearable electronics, smart windows, sunroofs in automobiles, lightning LEDs, and LCDs.