INTERFACIAL PHENOMENA IN POLYMER-ELECTROLYTE CELLS - LITHIUM PASSIVATION AND CYCLEABILITY

The properties of the electrode interfaces in polymer electrolytes based on the combination of poly(ethylene oxide) (PEO) and lithium salts, such as LiClO4, have been investigated by impedance spectroscopy. Three main dispersion phenomena characterize the a.c. impedance spectra of the Li/PEO-LiClO4 interface. The evolution of these spectra as a function of time of storage has been explained and interpreted using a solid-polymer layer (SPL) model assuming that the passivation of the lithium surface may be described by a combination of solid inorganic and polymeric layers. The time evolution of the impedance parameters indicates that a passivation film grows rapidly on the lithium surface. The kinetics of the passivation process may be controlled by incorporating into the electrolyte membrane-suitable inhibition agents.