The Electrochemical Displacement Reaction of Lithium with Metal Oxides

Abstract

The electrochemical reaction of lithium with α­LiFeO2,α­LiFeO2, β­Li5FeO4,β­Li5FeO4, and CoO is studied by in situ X-ray diffraction and in situ Mössbauer measurements. The results of the measurements show that these metal oxides are immediately decomposed during discharge to form lithia and the reduced metal. This reaction proceeds through a single intermediate or surface phase. The reaction products are nanometer-sized, but are not amorphous as was suggested previously. During charge the metal displaces the lithium in lithium oxide to form a metal oxide and lithium. In the case of CoO, the original lithium oxide oxygen lattice is preserved and the reaction resembles an ion exchange process. This also appears to be the case for the iron oxides. Upon discharge, the reverse occurs and the lithium replaces the metal in the metal oxide, once again forming lithium oxide and reduced metal on the bottom of discharge. Further cycling proceeds via oxidation/reduction of the metal by these displacement reactions with lithium. © 2001 The Electrochemical Society. All rights reserved.