REACTIONS OF TETRAHYDROFURAN AND LITHIUM HEXAFLUOROARSENATE WITH LITHIUM

As part of a basic study of the secondary Li electrode, the reactions of tetrahydrofuran (THF) with Li have been evaluated. Tetrahydrofuran is reductively cleaved by Li to lithium n-butoxide (BuOLi), the enolate anion of acetaldehyde, and ethylene. The AsF6- anion is reduced by Li to AsF3 which further reacts with BuOLi to form a brown film on Li. The brown film appears to be composed of an [formula omitted]n polymer and LiF. These products were observed to form irrespective of electrolyte purification procedure. In fact, highly purified media reacted most readily with Li presumably due to the absence of protective film-forming gases such as O2 and N2. Extended preelectrolysis of LiClO4/THF electrolytes formed large amounts of basic material, as expected. The same experiment periormed on LiAsF6/THF electrolyte revealed essentially no change in the medium's pH. Apparently, the AsF3 from AsF6- and the basic material from THF degradation effectively neutralize each other. A mechanism which accounts for Li-cyclic ether reactivity is proposed. © 1979, The Electrochemical Society, Inc. All rights reserved.