Enhanced Ionic Conductivity via Suppressed Crystallization and Strengthened Dynamics in Solid Polymer-Blend Electrolytes: A Comprehensive Broadband Dielectric Spectroscopy Study

In this study, we introduce solid polymer-blend electrolytes (SPBEs) in which the crystallization of poly(ethylene glycol) (PEG) is completely suppressed. This achievement was realized by utilizing low molecular weight PEG and incorporating high molecular weight poly(vinylidene fluoride) (PVDF) as the blend matrix, resulting in flexible and self-standing SPBEs. Complete inhibition of PEG crystallization is observed when employing the lower molecular weight of PEG or the higher concentration of lithium salt, leading to an impressive ionic conductivity of 2.9 x 10-4 S/cm at room temperature. Temperature-dependent ionic conductivity shows a strong correlation between ionic transport and segmental motion of the blend matrix, following the Vogel-Tammann-Fulcher (VTF) relation. Further analysis of AC conductivity, electric modulus, and dielectric loss isotherms, obtained through broadband dielectric spectroscopy, reveals a coupling behavior between the relaxation times and the ionic conductivity. This experimental system can serve as a model system for designing high-performance polymer-blend-based solid electrolytes to achieve good mechanical properties and superior ionic conductivities.