Electrochromic devices (ECDs) with different liquid electrolytes were fabricated using NiO film as counter electrode, WO 3 film as working electrode. The effect of liquid electrolytes containing different lithium salts (LiClO 4 , LiPF 6 , LiTFSI) on films and ECDs was investigated, such as transmittance change, charge density, memory effect and cyclic stability. Films or ECDs using LiPF 6 electrolyte have excellent electrochromic properties but low cyclic stability, compared with LiClO 4 and LiTFSI electrolytes. In order to deeply understand the effect of electrolyte on films and devices, the voltage distribution of films based on an analog cell and electrochemical impedance spectroscopy (EIS) were measured and analyzed in different lithium salts electrolytes. Results show that voltage distribution and EIS characteristics of films have obvious difference in liquid LiClO 4 , LiPF 6 and LiTFSI electrolytes. Voltage distribution on NiO and WO 3 films is unbalanced and the impedance of films in bleached and colored states is different in the same electrolyte.
Abstract Tungsten oxide (WO 3 ) has received attention as an electrochromic material because of its excellent properties. However, the long switch time and low coloration efficiency of WO 3 film limit its use. Herein, a nanocomposite film containing Preyssler-type polyoxometalate (POM) K 12.5 Na 1.5 [NaP 5 W 30 O 110 ]·15H 2 O (P 5 W 30 ) and WO 3 nanoparticles has been fabricated by layer-by-layer (LbL) self-assembly methods and characterized by UV-Vis spectra, scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical workstation. Compared to the pure WO 3 film, the [P 5 W 30 /WO 3 ] 20 film has better electrochromic properties. Then, the electrochromic properties of [P 5 W 30 /WO 3 ] 20 film were studied in different electrolyte. The results indicated that the composite film show high coloration efficiency (191.62 cm 2 C − 1 ), fast switch time (2.58 s, 1.48 s), good CV stability (500 th) in 0.5 M LiClO 4 /PC electrolyte, and successfully assembled of an electrochromic device. These advantages can make the nanocomposite film become a promising candidate for potential application in electrochromic devices. Graphic Abstract
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