The basic physical properties of Li2MnO3 and LiMn2O4 cathode materials

The basic physical properties of the layered lithium manganese oxide Li2MnO3 and the spinel lithium manganese oxide LiMn2O4 were investigated by the first-principles calculations based on density functional theory in this paper. Herein, the differences in crystal structures, electronic structures, and Li-ion transport characteristics between Li2MnO3 and LiMn2O4 were discussed in detail. It was found that both Li2MnO3 and LiMn2O4 are semiconductors, but the band gap of Li2MnO3 (2.1 eV) is much larger than that of LiMn2O4 (0.36 eV). The phonon dispersions show both the anti-ferromagnetic (AFM) configurations of Li2MnO3 and LiMn2O4 are dynamically stable. Moreover, the migration of Li ions in LiMn2O4 is faster than that in Li2MnO3. To further increase the Li diffusivity of Li2MnO3, the tetravalent dopants (Ir4+, Os4+, and Ru4+) were considered to substitute the Mn site of Li2MnO3. Our theoretical results explain the higher stability of doped Li2MnO3 through enhancing the Li migrating ability.