Electrochemical device

In an electrochemical device having one or more substrates (1, 7), one or more electrically conductive layers (2, 6), one or more electrochemically active layers capable of reversible ion insertion (especially of H, Li, Na and Ag) and an electrolyte, the electrolyte (4) comprises one or more layers of mineral oxide-type material in which ionic conduction is created or enhanced by incorporation of hydrogen and/or nitrogen compounds, especially nitrides. Also claimed are (i) electrochromic glazing including the above device, especially having variable energy and/or light transmission, together with one or more transparent glass or plastic substrates preferably assembled as multiple or laminated glazing; (ii) energy storage elements, especially a battery, including the above device; and (iii) a gas sensor including the above device. Further claimed is a process for making the above device, involving deposition of the hydrogen and/or nitrogen compound layer of the electrolyte by a vacuum method (cathodic sputtering, vapour deposition or plasma CVD), by a sol-gel synthesis method (especially by dipping, spray coating or laminar coating) or even by gas, powder or liquid phase pyrolysis.