Electrochromic tungsten oxyfluoride thin films were made by reactive magnetron sputtering of W in Ar+O2+CF4. A moderate CF4 fraction led to deposition at enhanced rates and films with fairly neutral color in their dark state. Transparent vanadium oxyfluoride films were made analogously; they were annealing post-treated in Ar+O 2+CF4. By fluorination it was possible to avoid the short-wavelength absorption that otherwise limits the usefulness of V2O5 in electrochromic smart windows. A transparent, adhesive, viscoelastic polymer electrolyte laminate was developed. It has good voltammetric cycling capability (106 times), good optical transmittance, and high conductivity, ranging from 10-6 S/cm (-10°C) to 10-3 S/cm (80°C).