Effect of Coprecipitated Metal Ions on the Electrochromic Properties of Nickel Hydroxide

Electrochromic films of a series of binary composite hydroxides of nickel and other metals (in a ratio of about 1:10) were deposited cathodically from mixed nitrate solutions onto transparent, conducting substrates. Visible spectra of the composite hydroxides were generally similar to those for nickel hydroxide, itself; the reduced forms were essentially transparent and the oxidized forms exhibited a strong, broad absorption band throughout the visible region. The coprecipitated metal ions did have significant effects on the switching of the electrochromic nickel couple. The composite hydroxide with silver displayed complex electrochromic switching behavior due to the presence of an additional electrochromic silver couple which could be colored cathodically. Significantly for electrochromic window applications, coprecipitation of cerium or lanthanum improved the durability of switching of the electrochromic nickel couple.