Small polaron migration in LixMn2O4: From first principles calculations

Migration of small polarons in λ-MnO2, Li0.5Mn2O4 and LiMn2O4 is studied via first principles calculations. Migration energy barriers of single small polaron migrations in λ-MnO2, Li0.5Mn2O4 and LiMn2O4 are 0.22 eV, 0.45 eV and 0.35 eV, respectively. The energy level changes of Mn-3d states along the polaron migration path are analyzed in detail. Results indicate that the activation energy barrier of polaron migration is strongly associated with the energy level shift of Mn-3dz2 orbital, which is dependent on the short range structural arrangement of Mn3+/Mn4+ in the crystal. The electrical conduction properties of LixMn2O4 at room temperature are then discussed.