An electrochemical impedance study on the interfacial behaviour of KC8 electrodes in LiClO4 containing electrolytes

The evolution of the impedance spectra of KC8 electrodes in 1 M LiClO4 + et hylene carbonate + dimethylcarbonate solution have been studied under open circuit voltage as a function of time. Additional studies have been perform ed before and after potassium deintercalation and in cycled electrodes. It has been found that KC8 slowly decomposes giving rise to a layer of insolub le KClO4 on the electrode surface that protects the compound from further d ecomposition. The interface may be simulated using two passivating layers i n addition to the charge transfer and diffusion impedance. The same type of equivalent circuit, with the eventual inclusion of a third layer, may be u sed to simulate the spectra after K deintercalation, and during lithium int ercalation. (C) 1999 Elsevier Science S.A. All rights reserved.