The solubility of lithium oxide (Li2O) and diffusion coefficient of oxide ions (O2-) has been determined to be 0.83 mol% and 2.1 x 10(-6) cm(2) s(-1), respectively, at 773 K in a LiCl-KCl-CsCl eutectic melt. Cyclic voltammograms show that oxygen (O-2) evolution on a boron-doped diamond (BDD) electrode is reversible and carbon dioxide (CO2) evolution on a glassy carbon electrode is irreversible. The standard formal potential of O-2/O2- estimated by electromotive force measurements using the BDD electrode is 2.431 V +/- 0.001 vs. Li+/Li at 773 K. (C) 2013 The Electrochemical Society. All rights reserved.