An electrochemical or an electroyltic device comprises a conductive anode and cathode separated by a solid electrolyte, and wherein one electrode surrounds the other, and the solid electrolyte comprises:(a) a matrix of polymer main chains, having side-chains linked to the main chains, which side chains comprise polar groups free from active hydrogen atoms,(b) a polar aprotic liquid dispersed in the matrix, and(c) an ionised ammonium, alkali metal or alkaline earth metal salt dissolved in the matrix and/or liquid, and a process for the preparation thereof.