Characterisation of an ionic liquid-based gel polymer electrolyte for potential applications

Gel polymer electrolytes (GPEs) have received global attention as a viable substitute for liquid and solid electrolytes. They consist of a salt/solvent mixture encapsulated within a suitable polymer. GPEs have been immensely used for various applications. However, the presence of solvents has now been found to be creating some adverse effects for the performance of GPEs owing to their toxic features. Hence, attention has been focused on ionic liquids, which are known to be safe and have the ability to act as solvents. In this study, investigations were carried out on a gel polymer electrolyte prepared using 1-butyl-3-methy limidazolium trifluoromethanesulfonate as the ionic liquid, zinc trifluoromethanesulfonate as the salt and poly(vinylidinefluoride-co-hexafluoropropylene) as the polymer. It is well-known that ionic liquids are room temperature molten salts. They are considered as ionic solvents with plasticising effect. The optimum composition of the electrolyte, 14.2 % polymer, 28.4 % ionic liquid and 57.4 % salt by weight showed a maximum room temperature conductivity of 4.52 x 10(-3) Scm(-1). This value together with the good mechanical properties proved the suitability of the GPE to be employed for energy storage applications. The sample was purely an ionic conductor. The electrochemical stability window was about 0.45 V. It was observed that plating and stripping of Zn ions takes place on Zn electrodes but not on stainless steel electrodes.