Flexible Electrochromic Zn Mirrors Based on Zn/Viologen Hybrid Batteries

Herein, we present a strategy for a switchable electrochromic zinc mirror/battery, which acts as a battery and a switchable electrochromic device via the electrodeposition and dissolution of Zn onto a transparent electrode. In this device, Zn and viologen constitute the anode and the cathode, respectively. Upon battery charging, Zn is electrodeposited onto the electrode to form a mirror while electric energy is stored as chemical energy. If the Zn mirror dissolves, the stored energy is released as electric energy. Compared with traditional electrochemical metallic mirrors, energy is sufficiently and sustainably utilized in this way. Also, a high reflectance of 84.9% and a specific capacity of 65.0 mAh g–1 are obtained for the Zn mirror, suggesting its excellent mirror performance and intrinsic energy storage properties. It is believed that this successful introduction of the battery concept to electrochemical metallic mirrors opens a wide avenue to drive its development toward a more imaginative and environmentally friendly future.