Synthesis and ionic conductivity study of new blended solid polymer electrolytes for sodium-ion transport

Blended solid polymer electrolytes (SPEs) are gaining attention as potential materials for advanced energy storage technologies, thanks to their improved ionic conductivity, mechanical integrity, and thermal stability. In this study, a series of 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—one 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 compositions 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). 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 (t_ion). 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.