Ion dynamics in PEO/PVP blend added with sodium triflouromethane sulphonate

Abstract

The solid polymer electrolyte membranes are required to fabricate safe and low-cost sodium batteries. This paper reports ion-dynamics studies on solid polymer electrolyte consisting of polyethylene oxide (PEO) and polyvinylpyrrolidone (PVP) as polymer blend and sodium triflate (NaCF3SO3) as sodium ion conducting salt. The solid polymer electrolytes PEO/PVP/NaCF3SO3 have been prepared using solution cast techniques. The electrochemical impedance spectroscopy has been utilized to study the role of incorporating NaCF3SO3 in varying amounts within PEO/PVP polymer blend. The optimized solid polymer electrolyte with 10 wt% NaCF3SO3 salt reports an ionic conductivity of 2.2 × 10-9 Scm−1 at room temperature. The ionic conductivity versus frequency plots indicates an increase in ionic conductivity values as the frequency increases. In order to explore the ion-dynamics the dielectric and modulus formulation has been adopted. The dielectric constant plots indicate polarizing effects at low frequencies and tangent loss curves shows presence of a relaxation peak. The frequency and relaxation time corresponding to the relaxation peak for optimized solid polymer electrolyte gives relaxation time of 2.69 × 10-3 s, charge carrier density of 1.18 × 1012 cm−3 and mobility of 0.01169 cm2 V−1 s−1. The safe potential window range of the optimized solid polymer electrolyte is determined to be 4.2 V which is good enough for usage in sodium batteries.