Ion dynamics and relaxation behavior of NaPF-doped polymer electrolyte systems.

The present paper discusses the ion dynamics of a novel polymeric system prepared by doping of NaPF in a lab-prepared polymer matrix. Ion dynamics of the system is analyzed by presenting the impedance data in different formalisms. Mobility (and hence the conductivity) continuously increases with salt concentration, and the phenomenon is correlated with salt's plasticization nature, which is reconfirmed by the shifting of minima in ∂log ε′/∂log ω vs. log ω curve towards high frequency. It has been observed that number of charge carriers ( N′) estimated from conductivity data do not represent the real charge concentration in the system. Within the experimental frequency (∼MHz) range, three different regions are identified in ∂log σ vs. ∂log ω curves namely (i) dc conductivity/free hopping, (ii) correlated ion hopping, and (iii) caged movement of ions. In the present case, also a scaled master conductivity curve is obtained by estimating the σ and ω (exclusively in Jonscher Power Law or JPL region) according to our previously proposed method. Scaling is realized with respect to salt concentration and temperature, which is an indication that salt concentration and temperature are only governing the number of charge carriers and mobility without affecting the underlying ion transport mechanism. Non-Debye-type relaxation phenomenon is indicated by KWW exponent β (<1). Relaxation times, obtained from tan δ vs. log ω curves, inversely follow the conductivity, indicating strongly correlated ion-polymer segmental motions. [ABSTRACT FROM AUTHOR]