Tungsten Oxide Electrochromic Windows with Lithium Polymer Electrolytes

Abstract

Electrochromic windows are built using as the electrochromic material and as the counter electrode. Both are deposited onto indium tin oxide coated glass panes by vacuum evaporation and are amorphous to X-ray diffraction. The electrolytes are lithium conducting polymers constituted by lithium--diallylamide-1-tetrafluoroethane sulfonate grafted in a cross-linked polyether network poly(isobutenyloligooxyethylene), with close to unity, and poly(ethylene glycol)–borate ester with , with close to 0.34. The electrochemical characterization of the electrodes is carried out by cyclic voltammetry, coulometric titration, and impedance spectroscopy, allowing the determination of the chemical diffusion coefficients of lithium into and . Potentiostatic cycling of the complete transmissive cells yield a transmission variation from 48 to 12% at with a response time of 10 s at room temperature. The main drawbacks are the residual coloration in the bleached state and the low exchange current densities at room temperature, which underline the need for good electrolyte/electrode contacts.