Polymethylmethacrylate based gel polymer electrolyte: An impedance spectroscopy study

Abstract

Gel polymer electrolytes have been recognized as a suitable class of electrolytes in various electrochemical applications such as rechargeable cells, super capacitors and electrochromic devices. It is due to the fact that they show appreciable ionic conductivities while possessing good mechanical stabilities which are absent with many other electrolytes. To be suitable for applications, any electrolyte should have a good stability with electrodes as well. In this work, the characteristics namely conductivity and stability have been studied for a gel polymer electrolyte based on the polymer, Polymethylmethacrylate (PMMA) using Impedance Spectroscopy technique. The composition of the sample was 22.5% PMMA / 30% EC / 30% PC / 17.5% Cu (CF3SO3)2 (by weight). Impedance measurements were carried out in the frequency range, 37 kHz – 0.01 Hz from room temperature to 600C using two stainless steel electrodes. Impedance plots were consisted with a semicircle and a spike at medium frequency and low frequency regions. The conductivity was found to be in the order of 10-3 S cm -1 . Impedance data obtained for a sample placed in between two Cu electrodes at different time intervals was used to evaluate the electrolyte – electrode interface. Impedance plots were consisted with two semi circles showing the effects of a surface film and the charge transfer resistance. It could be noticed that both of them increase with time. Investigations are being carried out to fine tune the composition of the electrolyte to have a lower amount of solvents which may affect for surface film and charge transfer resistance.