IMPEDANCE STUDY ON THE INTERFACE OF POLYELECTROLYTE AND METAL SODIUM

Ac impedance technique was used to study the electrochemical behaviour of polyelectrolyte-sodium interface, in which the polyelectrolyte has a single-Na+-ion conductivity of 3.5 X 10(-6) S/cm at 25 degrees C. I mpedance diagram of platinum electrode system consists of a depressed semicircle and a spur, whereas that of sodium electrode system has thr ee incomplete semicircles. This difference suggests there is an ion-co nducting passivation layer on the polyelectrolyte-sodium interface, wh ich is characterised by the semicircle of the impedance diagram of sod ium electrode system at intermediate frequency. Time dependence of the impedance spectra reveals that the formation of passivation layer is due to the reaction between polyelectrolyte and metal sodium, related to the storage time after the assembly of cells. The passivation layer was found to have a comparable resistance with that of the bulk polye lectrolyte, and hence have little effect on electrochemical process of the cells. Using impedance data, dielectric property of the polyelect rolyte media was discussed, and impedance spectra were explained as we ll.