The lithium-ion conducting gel polymer electrolytes (GPE), PVAc-DMF-LiClO4 of various compositions have been prepared by solution casting technique. H-1 NMR results reveal the existence of DMF in the gel polymer electrolytes at ambient temperature. Structure and surface morphology characterization have been studied by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) measurements. Thermal and conductivity behavior of polymer- and plasticizer-salt complexes have been studied by differential scanning calorimetry (DSC), TG/DTA, and impedance spectroscopy results. XRD and SEM analyses indicate the amorphous nature of the gel polymer-salt complex. DSC measurements show a decrease in T, with the increase in DMF concentrations. The thermal stability of the PVAc : DMF : LiClO4 gel polymer electrolytes has been found to be in the range of (30-60 degrees C). The dc conductivity of gel polymer electrolytes, obtained from impedance spectra, has been found to vary between 7.6 X 10(-7) and 4.1 x 10(-4) S cm(-1) at 303 K depending on the concentration of DMF (10-20 wt %) in the polymer electrolytes. The temperature dependence of conductivity of the polymer electrolyte complexes appears to obey the VTF behavior. (C) 2008 Wiley Periodicals, Inc.