Stabilizing Nickel-Copper Co-Deposition Electrochromism with the Assistance of Bromine Redox

As an attractive optical/heat dynamic management technology, reversible metal electrodeposition/dissolution electrochromism (RME-EC) shows many advantages, including high optical modulation amplitude, wide modulation band, and color neutrality, but also suffers from performance degradation because of uneven dendritic metal deposition as well as the formation/accumulation of isolated metal debris. In this paper, a facile RME-EC system is established in a green and affordable aqueous electrolyte, by making good use of the nondendritic Ni-Cu codeposition. Furthermore, an in situ self-healing strategy is further established by activating the Br⁰/Br^- couple of the Br-containing electrolyte to improve the EC performance. The generated Br⁰ species can spontaneously react with Ni/Cu and form soluble salts, preventing the accumulation of metal debris. With the assistance of bromine redox, the optimized device achieves a much higher cycling durability than the original one. This strategy can be achieved by simply modifying the electrolyte and applied voltage, providing an innovative approach for the design of high-performance EC systems.