Probing microstructure of polymer electrolyte-salt complex through impedance spectroscopy

In study of polymer-salt complexes usually one is interested in the dc conductivity, which can be extracted from impedance spectroscopy. However, impedance spectroscopy yields a host of additional information, for example, frequency variation of the measured admittance or impedance, nature of the Cole-Cole plot and dielectric function. Proper analysis of this information reveals details of the microstructure and transport processes in the sample. This in turn, will lead to development of better solid electrolytes with tailor-made properties. The polymer electrolyte PEO-NH₄ClO₄ shows an interesting variation in its properties in two different regimes, (1) where salt concentration is below ∼ 19 wt.% and (2) above this concentration. In the present paper we suggest an equivalent circuit incorporating a constant phase element (CPE), which reproduces the complex admittance behavior at different salt fractions. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.