Coupled Ion Conduction Mechanism and Dielectric Relaxation Phenomenon in PEO20-LiCF3SO3-Based Ion Conducting Polymer Nanocomposite Electrolytes

This study focuses on the effect of anatase titania acting as nanofiller on the relaxation dynamics and ionic conductivity behavior in polymer nanocomposite electrolyte based on PEO20-LiCF3SO3-TiO2. Using broadband dielectric spectroscopy, the dynamics of ion transport mechanism is studied over a wide range of temperature and frequency. Polymer salt complex exhibit the direct current (dc) conductivity sigma(dc) = 3.760 X 10(-7) S cm(-1) at 303 K. But with the addition of 8 wt % TiO2, a 2-order increase in the magnitude of dc conductivity is observed at the same temperature. Ion conduction mechanism is analyzed employing a complex relative permittivity as well as modulus formalisms. Isotherms of real part of conductivity spectra and dielectric loss spectra are analyzed to explain the observed first and second universalities in the ion conduction mechanism. Kramer-Kronig approach is used to discuss the crossover between the two universalities. Ratners classical approach in combination with modified Nernst-Einstein relation is used to correlate the coupling nature of polymer segmental relaxation and ionic transport mechanism. Successful scaling of conductivity spectra using the Summerfield approach and imaginary modulus spectra using maxima normalization approach indicate that ionic transport mechanism is a thermally activated temperature-independent phenomenon. Temperature-dependent dc conductivity is explained using a mismatch-generated relaxation for the accommodation and transport of ions concept as well as Vogel-Tammann-Fulcher relation to get a better insight into the ion conduction mechanism. With a comprehensive study of the relaxation events and ionic conductivity, a close coupling between polymer segmental relaxation and ionic conduction in polymer nanocomposite electrolytes is observed.