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

Abstract

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 P3[combining macron]1m. Lithium ions are embedded in Li0.5MnO3 until the trigonal Li2MnO3 phase is formed with the P3[combining macron]1m 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.