Thermodynamic behaviour of lead oxides in organic electrolyte lithium cells

Abstract

The behaviour, in equilibrium conditions, of PbO 2, Pb 2O 3, Pb 3O 4 and PbO cathodes in organic electrolyte lithium cells has been investigated on the basis of thermodynamic data. The possible discharge reactions of Li/lead oxide cells are examined and their standard Gibbs free energy changes evaluated as well as the electrode potentials at which such reactions take place. The results are utilised for constructing the phase diagram of the ternary Pb-O-Li system at constant temperature and pressure which allows to obtain the potential-composition curves in reversible conditions. The composition and morphology changes occurring during cell discharge are also considered. The theoretical results are finally discussed in connection with published experimental data, particularly with those on PbO 2 and Pb 3O 4, and the importance of thermodynamics is stressed to substantiate our understanding of electrochemical systems.