Poly(vinylidene chloride-co-acrylonitrile)-based gel polymer electrolytes are obtained using solution casting technique. The ionic conductivity and thermal behavior of polymer electrolytes have been investigated as a function of wt% of ethylene carbonate (EC). The thermal decompositions of polymer electrolytes have been determined by thermogravimetry and differential thermal analysis in the temperature range between 30 and 800°C. All the polymer complexes can be operated upto 170°C. This range well includes the operating temperature range of the lithium polymer batteries incorporating these materials. Bulk resistance of the electrolyte from alternating current (AC) impedance analysis gives the optimal EC ratio as 80 wt% for maximum ionic conductivity.