Large-Scale Color-Changing Thin Film Energy Storage Device with High Optical Contrast and Energy Storage Capacity

Thin film energy storage technology has great potential in emerging applications. The concept of integrating a smart window and energy storage provides an ideally large area for a thin film battery and a structural power backup for an energy-efficient building. However, due to the limited number of candidate materials, there is still a significant challenge in optimizing the electrochemical energy storage and electrochromic properties. Here we demonstrate a novel nickel–carbonate–hydroxide (NCH) nanowire thin-film-based color-changing energy storage device that possesses a high optical contrast of ∼85% at 500 nm and a superior capacitance of more than 170 mF/cm² at 10 mV/s, as well as good cycling performance and controllability. Its versatility as a smart energy storage and display device is successfully demonstrated. In addition, the scalable and cost-efficient method for fabricating the NCH material and its compatibility with flexible substrates are also expected to expand its horizon for future applications.