Electrical conductivity relaxation in PVOH+LiH2PO4+Al2O3 polymer composites

• Published in: Ionics Vol. 19; no. 1; pp. 83 - 89
• Main Authors: Zapata, V. H., Castro, W. A., Vargas, R. A.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 2013
• Subjects: Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Electrochemistry; Energy Storage; Optical and Electronic Materials; Original Paper; Renewable and Green Energy; Electrical relaxation; Poly(vinyl alcohol); KWW model; Ionic conductivity
• ISSN: 0947-7047; 1862-0760
• DOI: 10.1007/s11581-012-0710-3

Low-frequency conductivity measurements have been performed in solid polymer electrolyte composites based on the anhydrous PVOH–LiH 2 PO 4 –Al 2 O 3 system. A typical power law dependency in the real part of the conductivity, at higher frequencies, of the form ω n is observed, with an exponent n that depends on the alumina content and nearly independent of temperature. An analysis of the frequency dependence of the electrical susceptibility is conducted to obtain relaxation functions of the form exp[−( t / τ ) β ], with an exponent β  ≈  n  − 1. Correlation times, τ , and parameters characterizing the electrical relaxation in time and frequency domains are compared to show the equivalence of these representations. The anhydrous dc conductivity of the electrolytes increases with increasing lithium salt content, becoming of the order of 10 −5  S/cm for a salt molar fraction of x  = 0.14. This conductivity value increased by about one order of magnitude by addition of nanoporous particles of Al 2 O 3 . The temperature dependence of the samples conductivity was well described by the Vogel–Tammann–Fulcher’s equation indicating the effect of the polymer chains flexibility on ion migration. Although all membranes exhibited a “universal dynamic response” associated to the random hopping of the mobile carriers, variations in the measured relaxation parameters with alumina content indicate an increase of ionic correlations when adding the nonporous particles to the polyelectrolyte.