The basic physical properties of Li2MnO3 and LiMn2O4 cathode materials
Jialiang Xu, Shiji Zhu, Zhenming Xu, Hong Zhu
Abstract
The basic physical properties of the layered lithium manganese oxide Li 2 MnO 3 and the spinel lithium manganese oxide LiMn 2 O 4 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 Li 2 MnO 3 and LiMn 2 O 4 were discussed in detail. It was found that both Li 2 MnO 3 and LiMn 2 O 4 are semiconductors, but the band gap of Li 2 MnO 3 (2.1 eV) is much larger than that of LiMn 2 O 4 (0.36 eV). The phonon dispersions show both the anti-ferromagnetic (AFM) configurations of Li 2 MnO 3 and LiMn 2 O 4 are dynamically stable. Moreover, the migration of Li ions in LiMn 2 O 4 is faster than that in Li 2 MnO 3 . To further increase the Li diffusivity of Li 2 MnO 3 , the tetravalent dopants (Ir 4+ , Os 4+ , and Ru 4+ ) were considered to substitute the Mn site of Li 2 MnO 3 . Our theoretical results explain the higher stability of doped Li 2 MnO 3 through enhancing the Li migrating ability.