Identifying a Li-rich superionic conductor from charge-discharge structural evolution study: Li2MnO3

Li2MnO3 is a critical member of the Li-rich Mn-based layered material. To understand the process of electrochemical reaction in the monoclinic Li2MnO3, the structural evolution is investigated through the first-principles calculations based on density functional theory. During the delithiation process, a phase transformation together with a new trigonal phase at x = 0.5 (LixMnO3) has been reported, which belongs to the space group P31m. Lithium ions are embedded in Li0.5MnO3 until the trigonal Li2MnO3 phase is formed with the P31m symmetry preserved. Phonon and molecular dynamics simulations verify that this trigonal Li2MnO3 is dynamically and thermodynamicaly stable. Furthermore, our calculated results reveal that it has high conductivity of 0.36 S cm(-1) in the ab plane, which proves that this trigonal Li2MnO3 is a promising lithium superionic conductor.