High‐Performance Aqueous Zn²⁺/Al³⁺ Electrochromic Batteries based on Niobium Tungsten Oxides

Abstract Electrochromic energy storage devices (EESDs) are incorporating electrochromic and energy storage functions, which can visually display energy storage levels in real‐time to promote the next generation of transparent battery development. However, their performances are still limited for practical applications. Herein, a self‐powered EESD based on complex niobium tungsten oxide is designed using aqueous Zn²⁺ and hybrid Zn²⁺/Mⁿ⁺ (Mⁿ⁺ = Al³⁺, Mg²⁺, and K⁺) electrolytes. The results reveal that the use of Zn²⁺/Al³⁺ hybrid electrolyte achieves superior electrochromic performances including a short self‐coloring time, high optical contrast, and excellent cyclic stability. Furthermore, it is also found that the self‐coloring process is accompanied by a high discharged capacity of niobium tungsten oxide, with high optical modulation in the Zn²⁺/Al³⁺ hybrid electrolyte. The detailed mechanism on the performances of EESD using various electrolytes is systematically studied. This work provides a simple and effective strategy for an aqueous and self‐powered EESD with high optical contrast and good cycle stability.