Improved electron/Li-ion transport and oxygen stability of Mo-doped Li2MnO3

Abstract

Li₂MnO₃ is an important building block for stabilizing the structure as well as ensuring the high specific lithium storage capacity of xLi₂MnO₃·(1 − x)LiMO₂ (M = Ni, Co, Mn, etc.) cathode materials for lithium-ion batteries. However, the drawbacks of Li₂MnO₃ such as its low conductivity and oxygen evolution during delithiation make cathode materials less attractive in terms of safety, rate and cycling performances than traditional cathode materials. This work aims to improve the properties of Li₂MnO₃-related cathode materials by doping molybdenum (Mo) into Li₂MnO₃ (C2/c). First-principles calculations within the PBE + U scheme show that Mo doping is beneficial for improving both the dynamic and thermodynamic properties of Li₂MnO₃ by reducing the band gap and increasing the number of electronic states near the Fermi level. This promotes Li-ion diffusion between the lithium layer and transition-metal layer and charge transference from Mo to O, lowering the delithiation potential, adding Mo as another charge compensation donator upon Li removal, and enhancing the stability of oxygen according to the reaction enthalpy. Therefore, Mo doping is expected to be an effective way to improve the structural stability and rate performance of Li₂MnO₃ and xLi₂MnO₃·(1 − x)LiMO₂ cathode materials.