Ionic Conductivity Study of a New Promising Blended Solid Polymer Electrolytes for Sodium-ion Transport: Synthesis and Characterization

Abstract

Superionic polymer electrolytes are advanced solid-state ionic materials with high conductivity, widely studied for next-generation electrochemical device applications. In this study, Polyethylene oxide (PEO) and Polyvinyl pyrrolidine (PVP)-based a new sodium-ion conducting blended solid polymer electrolytes (BSPEs) were prepared using the composition (1−x) [70PEO:30NaCl] + xPVP, with x varying up to 15 wt.%. The blending strategy was employed to harness the complementary properties of the two polymers enhancing mechanical support and the other facilitating ion transport. A recently developed hot-press technique was utilized for the fabrication of these BSPEs. Among the composition studied, the formulation 98(70PEO:30NaCl) + 2PVP demonstrated the highest ionic conductivity (~3.7×10⁻⁵ S·cm⁻¹) and was identified as the optimal conducting composition (OCC). Material properties and the occurrence of polymer–salt/PVP complexation were validated using Scanning Electron Microscopy (SEM) for morphological assessment and Differential Scanning Calorimetry (DSC) for thermal characterization. Ion transport behavior was examined using a range of experimental methods and theoretical models, focusing on key parameters such as ionic conductivity (σ), ionic mobility (μ), mobile ion concentration (n), and ionic transference number (tion). Temperature-dependent conductivity measurements were conducted to determine the activation energy (Eₐ) of the OCC film. The findings indicate that the optimized polymer blend outperforms single-polymer systems in terms of both conductivity and thermal resilience, making it a promising candidate for use in solid-state battery applications.