Ultra-Stable Aqueous Electrochromism Based on [EMIM]+/I3- Coordination

Electrochromic (EC) windows are receiving numerous attentions owing to their flexibly adjustable optical properties controlled by external bias. Nevertheless, the widespread commercialization of EC windows still faces substantial impediments including high cost, intricate fabrication process, slow switching times and especially poor durability. Herein, we propose a facile yet high-performance EC system based on the reversible electrodeposition of iodine, which is theoretically free of “ion-trapping”, structure degradation, dendrite growth and corrosion issues encountered by the traditional EC windows. To overcomes the polyiodide shuttle problem, the electrolyte is further modified with [EMIM]+, which can coordinate with the polyiodide intermediates to form insoluble [EMIM]I3, and thereby effectively suppress polyiodide formation and shuttling. Moreover, the preferential adsorption of [EMIM]+ on to the Zn counter electrode ensures uniform and stable Zn deposition/striping, synergistically improving the durability of the I2-Zn EC window. With these multifaceted merits, the austere EC system simultaneously achieves rapid response speeds (tcoloring: 7 s, tbleaching: 6 s), high optical modulation amplitude (89.6% at 500 nm), impressive coloration efficiency (44.8 cm2 C-1) and excellent lifetime (without performance attenuation after 10,000 cycles). The scaling potential of the device is further demonstrated by constructing a large-area (10 * 10 cm2) device.