Cosolvent Multivalent Cation Hybrid Electrolyte for High-Performance Dual Band WO₃-Based Electrochromic Device

Electrochromic devices are potential entrants for applications in various cutting-edge fields, including energy-saving smart windows, wearable electronics, adaptive camouflage, etc. Nevertheless, the incompatibility between cations in electrolytes and electrochromic materials usually leads to unsatisfactory electrochromic performance. Here, a cosolvent multivalent cation hybrid electrolyte strategy was employed for the high-performance WO₃-based electrochromic film and device. The interaction between metal cations and the solvation shell is modulated by introducing highly polar H₂O molecules, which partially replace the large electronegative anions. This structural modification reshapes the solvation structure of the metal cations, facilitating ion transport and enhancing the compatibility of the interface between the electrolyte and the WO₃ electrochromic film. Moreover, leveraging the synergistic effect of Zn²⁺/Al³⁺ hybrid ions, which weakens electrostatic interaction between the cations and host materials, the WO₃ film delivers outstanding electrochromic performance, including large optical modulation (96.0% at 633 nm) and robust cycling stability (5000 cycles). Furthermore, the assembled electrochromic device based on the cosolvent multivalent cation hybrid electrolyte displays dual band independent modulation performance, robust cycling stability, and significant energy saving potential (128.66 MJ/m² in Honolulu). The cosolvent multivalent cation hybrid electrolyte highlights a rational direction for electrochromic devices to achieve large optical modulation and long-life stability.