The effects of chemical composition of adsorbed molecular layers on lithium electrode/polymer electrolyte interface stabilization

Previous work: in our laboratory has shown that the adsorption of self-asse mbled molecular layers on a polymer electrolyte surface can make the interf ace between the electrolyte and a lithium metal electrode more stable and c an hinder the growth of the type of passivation layer that inhibits ion mov ement between the electrode and electrolyte. This work is concerned with th e effect that the molecular composition of the adsorbed layer has on interf ace stability. Several compounds of the form R-(CH2CH2O)H have been found t o adsorb on the surface of the polymer electrolyte and stabilize the interf ace. It was found that the R group could be a long, straight hydrocarbon ta il capable of forming an ordered self-assembled structure or a branched hyd rocarbon or a siloxane with bulky hydrocarbon groups that form a brush-type structure. Molecules of the form R-OH and R-COOK, where R was a long, stra ight-chain hydrocarbon, would adsorb but appeared to have much disorder in their hydrocarbon chains. It is proposed that this disorder results from a low adsorption density that results in regions where the lithium metal can come in direct contact with the polymer electrolyte causing reactions that promote interface destabilization. (C) 2001 Elsevier Science B.V. All right s reserved.