Investigations on PEO/PVP/NaBr complexed polymer blend electrolytes for electrochemical cell applications

Experimental investigations on a sodium ion conducting polymer blend electrolyte system based on polyethylene oxide (PEO) and polyvinyl pyrrolidone (PVP), complexed with NaBr salt are presented in this paper. The complexed polymer blend electrolytes were obtained in the form of dimensionally stable and free-standing films by solution cast technique. Physical characterization by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were performed to study the structural properties, their change along with ion-polymer interactions and thermal stability of the samples. The transport numbers of different mobile species were determined by means of d.c. polarization and combined a.c./d.c. techniques. Cationic transportation was found to be dominant in the films of high degree of amorphicity. Electrical properties were measured as a function of composition and temperature using complex impedance spectroscopy. The temperature dependent electrical conductivity showed Arrhenius type behavior. Activation energies were found to decrease with increasing concentration of the salt. Electrochemical cells were prepared using PEO/PVP/NaBr polymer blend electrolyte system and their discharge characteristics were studied. These studies suggested the practical realization of electrochemical cells using the present sodium ion conducting polymer blend electrolyte system.