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Proton-conducting gel polymer electrolytes based on gelatin plasticized with glycerol and containing acetic acid were investigated, characterized, and applied to electrochromic window. For glycerol contents varying from 7% to 48%, the conductivity of the uniform and predominantly amorphous gel electrolyte was found to follow a Vogel-Tamman-Fulcher behavior with the temperature. Typically, for the electrolyte chosen to make 7×2 cm 2 electrochromic smart window with the configuration: glass/ fluor-doped tin oxide (FTO)/WO 3 /gelatin electrolyte/CeO 2 -TiO 2 /FTO/glass and containing 28% of glycerol, the conductivities were found to be of the order of 5×10 −5 S/cm at room temperature and 3.6×10 −4 S/cm at 80°C. The device was characterized by spectroelectrochemical techniques and was tested up to 10,000 cycles showing a fast coloring/ bleaching behavior, where the coloring process was achieved in 10 s and the bleaching in 2 s. The transmission variation at the wavelength of 550 nm was about 15%. The cyclic voltammograms showed a very good reversibility of the cathodic/anodic processes, and the charge density was about 3.5 mC/cm 2 . The memory tests showed that the transmittance in the colored state increased by 8% in 90 min after removing the potential.

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Nb 2 O 5 coatings prepared by the sol-gel route using the dip coating technique with sols prepared from alkoxide or chloroalkoxide (two different methods: sonocatalytic and conventional) precursors are a promising alternative for WO 3 electrochromic coatings. The crystalline films (TT phase) sintered at 560 and 600°C are transparent and present a deep blue colour under Li> ion insertion. Electrochemical stability is excellent as these systems are fully reversible and stable and no change in colour, amount of charge exchanged and corrosion effect could be observed after 2000 voltammetry cycles between 2 and !1.8 V versus Ag. The electrochemical and optical properties of these coatings have been determined as a function of sintering temperature. The superficial structure was visualized by atomic force microscopy (AFM) and scanning electron microscopy (SEM) and the Li> diffusion coefficient was determined for both kinds of coatings.