Wide‐Temperature Adaptive Electrochromic Device Enabled by Deep Eutectic Solvent‐Based Electrolytes

Abstract Diverse application scenarios often require electrochromic devices (ECDs) to possess high durability over a wide temperature range. Unfortunately, most ECDs suffer from limited operating temperatures due to electrolyte decomposition at high temperatures and sluggish reaction kinetics at low temperatures. Herein, by tailoring the solvation structure, a temperature‐adaptive deep eutectic solvent (DES)‐based electrolyte is developed. Over a wide temperature range of −25 to 60 °C, this DES‐based electrolyte exhibits exceptionally high transmittance of over 95% within the broad visible‐near infrared range (300–1100 nm) and outstanding ionic conductivity. Moreover, the DES‐based electrolyte enables WO 3 film to achieve excellent electrochromic performance in a wide temperature range, embodying large optical modulation (74% at −25 °C and 82% at 60 °C), fast responses (< 8 s), good optical memory, and remarkable cycling stability (1500 cycles). ECDs assembled by the DES‐based electrolyte can also operate over −25 to 60 °C. The DES‐based temperature adaptive electrolyte opens an avenue for wide‐temperature ECD designs.