By thermogravimetric analysis, impedance spectroscopy and potentiodynamic cycling, the thermal and electrochemical stability of polymer electrolytes based on PVC and its chlorinated derivatives have been studied. The methods used to modify the properties of these polymeric electrolytes and to provide them with electrochemical stability when used in lithium batteries where the cathode is based on natural, nanostructured, and thermally-sprayed pyrite have been demonstrated.