The grain morphology and surface properties of a Li-rich Li2MnO3 cathode material: a first-principles study

Abstract

Complex surface evolution plays a critical role in the rapid energy degradation of Li₂MnO₃ as a cathode material for high-energy-density Li-ion batteries. Here, we demonstrate that the defect-containing (001) surface of Li₂MnO₃ satisfies the stoichiometric relationship under air conditions and in the main experimental temperature window. For Li₂MnO₃ cathode materials, the surface area fraction of the terminals that satisfy stoichiometry (STO) can reach at least 70% when the synthesis environments are under Li&Mn-mid and Mn-rich conditions, while it is hard to exceed 40% under Li-rich conditions. All the stable surfaces exhibit excellent electrochemical properties, save the poor charge voltage and conductivity of the (001)_STO terminal. The low p-band center of O ions and stronger Mn–O bond strength effectively prevent the release of oxygen during Li-ion extraction in Li₂MnO₃. In addition, the low surface energy of the (001)_STO terminal and the high energy barrier between the different terminals dominates the dish-shape appearance of the grain morphology.