Smart electrochromic devices based on reversible (non-)metal electrodeposition

Smart electrochromic devices based on reversible electrodeposition/dissolution have attracted increasing attention owing to their large optical modulation, simplified device configuration, and potential multifunctionality. Different from conventional electrochromic systems relying on ion insertion/extraction in pre-deposited films, these devices offer dynamic optical regulation through reversible electrochemical deposition and dissolution at the electrode/electrolyte interface. In this review, recent progress in reversible electrodeposition-based electrochromic devices is summarized with emphasis on three representative families: reversible metal, iodine, and MnO2 electrodeposition. For metal-based devices, deposition morphology, alloy composition, electrolyte regulation, and electrode surface modification are key factors determining optical contrast, color tunability, and cycling stability. For iodine systems, the suppression of the polyiodide shuttle and dead iodine formation is central to achieving stable neutral-color modulation. For MnO2 systems, reversible Mn2+/MnO2 conversion enables wide ultraviolet (UV)-visible modulation and multicolor states, while dead manganese residues and non-uniform deposition remain major challenges. Finally, the common design principles and system-specific trade-offs are compared and discussed, followed by an outlook on practical reliability, large-area fabrication, adaptive thermal regulation, and multifunctional integration. This review aims at inspiring future endeavors towards implementation of reversible (non-)metal electrodeposition-based smart electrochromic devices.