Several gel membranes of the type PVdF/EC-PC/SiO2 without and with electrolyte salts have been characterised by vibrational spectroscopy and by galvanostatic cycling tests. It is found that the structure of the PVdF matrix in the membranes depends on the gel composition and preparation conditions. At high loads of polymer parts of the PVdF chains assume a TGTG' conformation typical of the so-called "structural form II". The formation of PVdF of form II is favoured when slow cooling rates are employed during the membrane preparation. In galvanostatic cycling tests in combination with a Sn/SnSb electrode, the present gel-type polymer electrolytes give results comparable to those obtained with the corresponding liquid electrolytes. (C) 2004 Elsevier Ltd. All rights reserved.