Humidity-Dependent Ion Conduction Mechanism of PVA-Based Polymer Electrolyte Films

Abstract

Polymer electrolytes are studied worldwide for their possible applications in various electrochemical devices. In the last few decades, a large number of polymer electrolytes have been developed and characterized. However, in most cases, the effect of humidity has been ignored. In this paper, we report a systematic study on a polymer electrolyte's electrical and dielectric properties at different humidity. The chosen system is a Polyvinyl Alcohol (PVA) based polymer electrolyte in which potassium iodide (KI) with differing weight percentage is selected as the dopant salt for the synthesis of PVA-KI films. Four different compositions of PVA-KI films are synthesized using the solution cast technique. Electrical impedance spectroscopy (EIS) technique is used to determine its conductivity at three different humidity levels: 55%, 75%, and 85%. Analysis of dielectric permittivity and electrical modulus of the films is also done at these humidity levels. The highest conductivity for all the four different compositions of films is found to be at 85% humidity level, of which the optimum ionic conductivity is seen in the 75:25 composition of PVA:KI with a value of 1.25×10−4 S cm−1.The number of charge carriers and their mobility are calculated for all samples at different humidity levels. A correlation has been established between the conductivity of the films and the mobility of charge carriers. © 2023 Wiley-VCH GmbH.