A novel view at electrode polarization

With the scanning Kelvin probe the surface potential of the ion conducting polymer polyethylene oxide doped with lithium perchlorate is measured. The potential distribution after application of an external voltage between two metal electrodes is determined dynamically and in the stationary case. The strongly non-linear surface potential between the electrodes can be attributed to a space charge polarization of internal charges which prevails in these systems. The time dependent evolution of the surface potential after a voltage step shows how the distribution of charges changes dynamically. It can be shown that this behavior is influenced by the movement of mobile internal charges as well as by trapped charges at the electrodes. Furthermore, the results of the measurements are compared to computer simulations performed with a three-dimensional hopping model which show the same results qualitatively.