A Reversible MnO2 Deposition‐Enabled Multicolor Electrochromic Device with Efficient Tunability of Ultraviolet–Visible Light

Electrochromic technology offers exciting opportunities for smart applications such as energy-saving and interactive systems. However, achieving dual-band regulation together with the multicolor function is still an unmet challenge for electrochromic devices. Herein, an ingenious electrochromic strategy based on reversible manganese oxide (MnO₂) electrodeposition, different from traditional ion intercalation/deintercalation-type electrochromic materials is proposed. Such a deposition/dissolution-based MnO₂ brings an intriguing electrochromic feature of dual-band regulation for the ultraviolet (UV) and visible lights with high optical modulation (93.2% and 93.6% at 400 and 550 nm, respectively) and remarkable optical memory. Moreover, a demonstrative smart window assembled by MnO₂ and Cu electrodes delivers the electrochromic properties of effective dual-band regulation accompanied by multicolor changes (transparent, yellow, and brown). The robust redox deposition/dissolution process endows the MnO₂-based electrochromic device with excellent rate capability and an areal capacity of 570 mAh m^-2 at 0.1 mA cm^-2. It is believed that the metal oxide-based reversible electrodeposition strategy would be an attractive and promising electrochromic technology and provide a train of thought for the development of multifunctional electrochromic devices and applications.