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

Abstract 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 (MnO 2 ) electrodeposition, different from traditional ion intercalation/deintercalation‐type electrochromic materials is proposed. Such a deposition/dissolution‐based MnO 2 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 MnO 2 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 MnO 2 ‐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.