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.
