In this work we report the electrochemical and physical characterization of proton-conducting gels prepared by means of a swelling procedure proved successful for the synthesis of membranes of interest for lithium battery technology. Basically, this new approach considers the formation of a precursor membrane by the gelification of a selected polymer matrix, e. g., a poly(acrylonitrile), matrix using a suitable solvent. This membrane is then embedded in an acidic solution: by a phase inversion process, the gelling solvent leaves the polymer matrix to be replaced by the acid solution, to finally obtain a self-standing, proton-conducting membrane. Impedance spectroscopy analysis demonstrated the good conductivity of the materials, and infrared, Raman, and fuel-cell studies confirm that this conductivity is due to protonic transport. (C) 2003 The Electrochemical Society.