Bringing Hetero‐Polyacid‐Based Underwater Adhesive as Printable Cathode Coating for Self‐Powered Electrochromic Aqueous Batteries

Abstract The advent of electrochromic aqueous batteries represents a promising trend in the development of smart and environmentally friendly energy storage devices. However, it remains a great challenge to integrate electrochromic, flexible, and patterned features into a single battery unit through a simple operation. Herein, an entirely new class of hetero‐polyacid‐based underwater adhesives is designed and synthesized by combining the redox properties of hetero‐polyacids and the water‐resistant binding of adhesives in single system. The hybrid underwater adhesives not only serve as printable electrode coatings in aqueous solution but also offer unique electrochromic feature for guiding the convenient fabrication of self‐powered electrochromic aqueous battery. The reversible discharging and H 2 O 2 assistant charging behavior is also demonstrated. This kind of wet and electrochromic adhesive with excellent toleration of mechanical deformation offers great promise in developing flexible and smart energy storage configuration, which provides a user‐device interface platform allowing one to evaluate the battery's charging state based on the naked eye–visible change in color.