Electrochromic Lithium Nickel Oxide Thin Films by RF-Sputtering from a LiNiO₂ Target

Thin films of lithium nickel oxide were deposited by rf sputtering from a stoichiometric LiNiO₂ target. The composition and structure of these films depended on the oxygen pressure during deposition (sputtering gas is Argon), and, to a certain extent, the target history. The sputtering geometry, i.e. the substrate to target distance and the sputtering angle were also critical. the films exhibit excellent reversibility in the potential range 1.1V to 3.8 V vs Li/Li⁺ and could be cycled in a liquid electrolyte half cell for more than 3000 cycles with a switching range ΔT_vis close to 70%. The coloration efficiency in the visible was typically -30 to -40 cm² C^-1. The switching performance of a device utilizing a lithium nickel oxide film as counter electrode for a tungsten oxide electrochromic film is reported.