Monte Carlo simulation of the open-circuit potential and the entropy of reaction in lithium manganese oxide

Abstract

The open-circuit potential and the entropy of reaction for Li in the intercalation compound LiyMn2O4 were simulated with the Monte Carlo method. Two variations of the Monte Carlo method were implemented: one with the open-circuit potential being held constant, and one with concentration of lithium ions being held constant. The entropy of reaction simulated by the constant-potential method agrees with the experimental data in terms of overall shape. The value of the entropy obtained from the simulation is also of comparable magnitude to the experimental data, but with a displaced composition dependence. Only open-circuit-potential isotherms were obtained from the constant-Li-concentration method because results were not sufficiently precise to generate a smooth entropy curve. Nonetheless, the isotherms obtained from the constant-Li-concentration method still capture the basic feature of an isotherm, such as the sudden change of slope at y approximately equal to 0.5 and the frustration of the ordering process due to the presence of pinned Li ions. (C) 2002 The Electrochemical Society