Improving Electrochromic Cycle Life of Prussian Blue by Acid Addition to the Electrolyte

In this study, we examined the cyclic stability of Prussian blue (PB) films in electrolytes with acid. The cyclic stabilities of the PB films were investigated in K⁺ based electrolytes with different values of solution pH. The acidified KCl solution can significantly improve the durability of the film. Among the three pH values tested, the KCl solutions (pH = 2.15 and pH = 3.03) showed better performance. Furthermore, we investigated the cyclic stabilities of the PB films in LiClO₄/PC electrolyte containing different acids. We found that the cyclic stability of PB film was significantly improved when a small amount of acetic acid was dissolved in LiClO₄/PC electrolyte. The PB film exhibited stable optical modulation after up to 20,000 cycles in LiClO₄/PC electrolyte containing acetic acid-a much higher result than those of some literatures. This suggests that the addition of acetic acid to LiClO₄/PC electrolyte can promote the development of PB-based devices with improved stability.