Abstract: Disclosed herein is a high voltage electrochromic device comprising a number of electrodes, a non-aqueous electrolyte system, said system comprising one or more alkali and/or ammonium salts and a solvent in the form of one or more ortho-, meta- or para-phthalates. Also disclosed is a method for producing said electrochromic devices and the use of phthalate based electrolyte systems in electrochromic devices.

Abstract: A new non-aqueous electrolyte system for use in batteries, capacitors and electrochromic displays, and consisting essentially of an alkali or ammonium salt, a solvent mixture, and optionally a polymer is disclosed. The new system is characterized in that the solvent mixture comprises a mixture of ethylene carbonate (EC) and -valerolactone (-VL), optionally containing one or more additional solvents selected from other organic carbonates, other lactones, esters and glymes, said system optionally being confined a separator. The electrolyte system can be applied in a broad voltage range, has a conductivity higher than 10.sup.-3 S/cm at room temperature, and shows a high stability against reduction. The improved stability towards reduction is mirrored in a cycling efficiency which is superior to the cycling efficiency of known non-aqueous electrolyte systems.