Dielectric and electrochemical studies on carbonate free Na-ion conducting electrolytes for sodium-sulfur batteries

Research on sodium based electrolytes and batteries have received the researcher's attention as it may fulfill the energy storage needs, especially the grid level requirements where cost is as important as the performance. The present paper reports experimental investigations on carbonate free Na-ion conducting gel polymer electrolytes prepared by entrapment of sodium triflate salt in ionic liquid into poly (vinylidinefluoride-co-hexafluoropropyline) polymer matrix. This electrolyte system is subjected to X-ray diffraction and differential scanning calorimetry to probe changes in structural and thermal properties. The electrochemical impedance spectroscopy technique is employed to determine the bulk resistance and ionic conductivity of the polymer gel electrolyte system. In order to investigate the temperature dependent dielectric behavior of electrolyte system, real part of the permittivity and dielectric loss are discussed as a function of frequency. The open circuit voltage and discharge capacity is recorded to determine the initial voltage obtainable and discharge profile for the prototype sodium-sulfur cell. The investigations reveal that ionic liquid based electrolytes appear to be valid candidates to replace the unstable and flammable conventional carbonate for their use in fabricating electrolytes for future sodium-sulfur batteries.