Enthalpy of formation and heat capacity of Li2MnO3

Abstract

The enthalpy of formation of Li2MnO3 was measured by high temperature oxide solution calorimetry in a sodium molybdate solvent and the heat capacity of the compound was determined using differential scanning calorimetry. The enthalpy of formation of Li2MnO3 from the elements is slightly less exothermic than that of the orthorhombic and monoclinic modifications of LiMnO2 but more exothermic than that of LiNiO2, LiCoO2, the LiNi1-xCoxO2 solid solutions and the Li1+xMn2-xO4 spinels. The heat capacity of Li2MnO3 is also slightly lower than the estimated heat capacity based on stoichiometric amounts of Li2O and MnO2 according to the Neumann-Kopp approximation. The slight differences in heat capacities are attributed to the differences in the bonding environments of Li+ ions in Li2MnO3 and the constituent binary oxide Li2O. The thermochemical data presented here are essential for the advanced thermodynamic modeling of multicomponent electrode materials based on the promising xLi2MnO3·(1-x)LiMO2 nano-composite cathode system.