Migration of Mn cations in delithiated lithium manganese oxides

Abstract

Li₂MnO₃ is an integrated component in lithium-manganese-rich nickel manganese cobalt oxides, and the conversion of Li₂MnO₃ to a spinel-like structure after electrochemical activation has been associated with the continuous potential decay of the material. Delithiated Li₂MnO₃ and delithiated LiMn₂O₄ were used as model materials to investigate the mechanism of forming the spinel-like structure. An in situ high-energy X-ray diffraction technique was used to trace the structural change of materials at elevated temperatures, a procedure to mimic the structural transformation during the normal cycling of batteries. It was also found that the migration of Mn atoms from the octahedral sites to tetrahedral sites is the key step for phase transformation from a monoclinic structure to a spinel structure.