Impedance and ionic transport properties of proton-conducting electrolytes based on polyethylene oxide/methylcellulose blend polymers

Proton-conducting polymer electrolyte films were prepared by dissolving NH4I salt in polyethylene oxide/methylcellulose (PEO/MC) blend polymers using the solution cast technique. The semi-crystalline nature of the sample was identified from the X-ray diffraction (XRD) pattern. The surface morphology on the electrical conductivity was analyzed by scanning electron microscopy (SEM). The highest ionic conductivity of 7.62 x 10(-5) S/cm was achieved at room temperature for the sample containing 30 wt. % of NH4I. The temperature dependence of the Jonscher's exponent shows that the conduction mechanism can be well represented by the overlapping large polaron tunneling (OLPT) model. The electrical conductivity enhancement was analyzed by the Rice and Roth model, which showed that the increase in the salt concentration caused an increment in the mobility and the diffusion coefficient of the ions. For all prepared samples, the highest value of conductivity was associated with the minimum value of activation energy. The dielectric data were analyzed for the highest ionic conducting sample at various temperatures to clarify an important factor of the ion conduction. The non-Debye behavior of the samples can be expressed from the electric modulus formalism and the dielectric properties of the electrolytes that have been proven by the incomplete semicircular arc of the Argand plots. (C) 2020 The Authors. Publishing services by Elsevier B.V. on behalf of Vietnam National University, Hanoi.