Lithium Isotope Effects Accompanying Electrochemical Insertion of Lithium into Metal Oxides

Abstract

Lithium was electrochemically inserted into SnO2 and Fe2O3--SiO2 binary oxide from the mixed solution of ethylene carbonate and methyl ethyl carbonate containing 1 M LiClO4, and the lithium isotope effect accompanying the insertion was investigated. Tin(IV) oxide showed a slight selectivity towards the heavier isotope of lithium with the separation factor (S) ranging from 0.982 to 0.999 at 25°C. Fe2O3--SiO2 binary oxide, on the other hand, showed no specific lithium isotope selectivity with S scattered around unity at the same temperature. These results were reasonably understood by assuming the reduction of the metals in the host materials from Sn(IV) to Sn(0) and from Fe(III) to Fe(II) and the formation of lithium oxide upon Li insertion.