Effect of Aqueous Electrolyte Ions on Electrochromic Properties of Amorphous WO3

： WO 3 is an ideal inorganic electrochromic material. Its electrochromic mechanism is reversible redox re⁃ action under the driving of voltage ， accompanied by the insertion and extraction of counterions in the material. In this paper ， we investigated the electrochromic properties of amorphous WO 3 in three aqueous electrolyte solutions of Li ， Zn and Al. WO 3 achieves the best electrochromic performances when Al 3+ was used as insertion ions ， including fast response speed （ 2. 8 s for coloring and 1. 1 s for decolorization ）， large optical contrast （ 83. 4% at 700 nm ）， good cycling stability （ 2. 8% decay for 1 000 successive cycles ）， high coloration efficiency （ 74. 7 cm 2 · C -1 ）， and its comprehensive performance is at high level among the reported WO 3 electrochromic devices. Mechanistic studies have revealed that the enhanced performance in Al 3+ electrolytes is due to the fast ion transport kinetics. These re⁃ sults will provide a simple and effective guidance for the construction of high - performance electrochromic devices and the optimization of electrolytes