Ion Transport and Segmental Dynamics in Cross-linked Poly(ethylene glycol) Diacrylate-Based Solid-like Polymer Electrolytes

Ion transport and segmental dynamics have been investigated in cross-linked poly(ethylene glycol) diacrylate-based solid-like polymer electrolytes containing 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) ionic liquid and lithium tetrafluoroborate (LiBF4) lithium salt using broadband dielectric spectroscopy. The conductivity spectra at different temperatures have been analyzed using the power law model coupled with the Poisson-Nernst-Planck model to account for the electrode polarization effect dominating the low frequency region of the spectra. It is observed that the temperature dependence of the ionic conductivity, hopping frequency, and ion diffusivity follows the Vogel-Tammann-Fulcher (VTF) relation. The dielectric relaxation data have been also analyzed in terms of electric modulus and derivative dielectric spectra. The temperature dependence of segmental relaxation time and conductivity relaxation time obtained from the derivative dielectric loss spectra and modulus loss spectra, respectively, obeys the VTF relation. A strong coupling between the segmental relaxation of polymer chains and the ionic transport in the cross-linked polymer electrolytes has been observed. The scaling of the conductivity spectra and the modulus loss spectra indicates that the ion transport in these cross-linked polymer systems obeys the time-temperature superposition principle.