A polymeric solid electrolyte (PSE) based on a poly(ethylene oxide)/poly(bisphenol A-co-epichlorohydrin) (PEO/PBE) blend with LiClO4 was obtained and characterized by its thermal, morphological, spectroscopic and electrochemical properties. DSC analysis showed suppression of PSE crystallinity for O:M lower than 32. The phase diagram exhibited four distinct regions, associated with the vitreous, viscoelastic and melt miscible phases, and a region where a viscoelastic and an immiscible vitreous phase are in equilibrium. Fourier transform infrared spectroscopy indicated complexation of the cation Li+ by both PEO and PBE oxygen atoms. Electrochemical impedance spectroscopy was used to characterize the ionic transport in the PSE at various temperatures and cyclic voltammetry provided information on the electrochemical stability window, which was found to be 5.5 V (C) 2003 Elsevier B.V. All rights reserved.