Manipulating Interfacial Water Molecules via Eutectic-Polymer Dual-Network for Stable Electrochromic Devices

Aqueous Zn-WO₃ electrochromic devices (ZWEDs) represent a promising frontier in energy-efficient electrochromic systems. However, their practical application is hindered by the short device lifespans due to the poor electrode/electrolyte interfacial stability which originates from high water activity. Herein, we develop a eutectic-polymer dual-network electrolyte to regulate water activity and stabilize the electrode/electrolyte interface. Combined in situ/ex situ spectroscopic analysis and simulations reveal that this eutectic-polymer dual-network stabilize the electrode structure via two complementary effects: (i) reconstruction of the hydrogen-bond network confines free water molecules, suppressing water activity and parasitic reactions; and (ii) preferential adsorption of acetamide molecules over water on the electrode surfaces forms a stable molecular interfacial layer that regulates Zn²⁺ electrochemical behavior and further mitigates water-induced side reactions. Benefiting from the synergy between hydrogen-bond reconstruction and interfacial adsorption, the interfacial stabilities of both Zn anode and WO₃ cathode are significantly enhanced. Consequently, the Zn-WO₃ device achieves outstanding cyclic stability in both ion storage and optical modulation over 1000 cycles, with an operational temperature range expanded to -30°C∼80°C. This strategy offers a promising pathway to enhance the interfacial stability in ZWEDs across a wide temperature range.