Interfacial modulation-based ternary eutectic electrolyte enhances fast response and high stability of NbWOx electrochromic energy storage devices

Bifunctional electrochromic devices incorporating electrochromic and energy storage have great potential for future applications, however, current performance shortcomings limit their practical application. Here, a ternary eutectic electrolyte coupling aluminum sulfate octadecahydrate, urea, and ethylene glycol is proposed. Based on a specific crystal superstructure, Nb 18 W 16 O 93 material achieves reversible insertion/deintercalation of Al 3+ , exhibiting fast response (t c  = 3.1 s, t b  = 2.6 s), high cycling stability (after 2000 cycles, the light modulation amplitude remains at the initial 92.85 %), and high surface capacitance (30.88 mF cm −2 ) at a surface current density of 0.25 mA cm −2 . In addition, Nb 18 W 16 O 93 /NiO electrochromic energy storage devices assembled using ternary eutectic electrolytes have excellent properties such as high coloring efficiency and high surface current density. The enhanced performance is attributed to the assistance of urea in weakening the strong interaction between aluminum ions and water molecules, along with the enhancement of ionic conductivity by glycol. This work, combined with green and sustainable eutectic electrolytes, provides an effective strategy to improve cycling stability and fast response time of electrochromic energy storage devices.