Structural and electrical characteristics of PVA:NaTf based solid polymer electrolytes: role of lattice energy of salts on electrical DC conductivity

Abstract

Solid polymer electrolytes (SPEs) based on polyvinyl alcohol (PVA) and sodium triflate (NaTf) have been prepared by solution cast technique. X-ray diffraction was performed for structural analysis. The decrease of intensity of crystalline peaks of PVA upon addition of NaTf salt reveals the increase of amorphous domain in SPEs. Impedance plots (Zi vs. Zr) shows that the electrolyte samples have a smaller bulk resistance. The highest achieved room temperature DC conductivity is 7.39 × 10−5 S/cm for the sample incorporated with 30 wt% of NaTf. The influence of lattice energy of sodium salts on DC conductivity is discussed. It was appeared that the lattice energy of salts significantly affects the conductivity behavior of polymer electrolytes. High DC conductivity can be achieved for polymer electrolytes incorporated with low lattice energy salts. The pattern of DC ionic conductivity against 1000/T is follows Arrhenius equation. The highest conducting composition has the lowest activation energy (0.109 eV). The DC conductivities calculated from the complex impedance plots are close to those obtained from the plateau region of AC conductivity spectra. Transport parameters such as density of mobile ions (Na+), mobility, and diffusion coefficient were determined for the samples using the Rice and Roth models. The dielectric analysis suggests non-Debye type of relaxation of ions in the present work.