The effect of Ni-doping on the stability of Li₂MnO₃ cathode material: a DFT study

Materials Modelling Centre, University of Limpopo, Private bag X1106, Sovenga, 0727, South Africa

^* Corresponding author: mphahlelegrm@gmail.com

Abstract

The density functional theory with Hubbard parameter (DFT+U) incorporated within the Vienna Ab Initio Simulation Package was utilized to investigate the structural, electronic, elastic, and dynamical properties of pristine and Ni-doped Li₂MnO₃. The cluster expansion technique was used to generate the doped phases of Li₂MnO₃. The binary phase diagram predicted Li₂Mn_0.83Ni_0.17O₃ as the most stable phase with the lowest heat of formation. The study shows that Li₂Mn_0.83Ni_0.17O₃ is more thermodynamically stable than Li₂MnO₃ with a lower heat of formation. Additionally, the density of states showed that Li₂Mn_0.83Ni_0.17O₃ has a narrower band gap of 1.54 eV compared to the undoped structure with a band gap of 1.89 eV which leads to a higher electrical conductivity of the material. The elastic constants show that both structures are mechanically stable and lastly the phonon dispersions showed that these structures are vibrationally stable with no presence of imaginary vibrations. Finally, based on the results, Li₂Mn_0.83Ni_0.17O₃ can be proposed as potential cathode materials for use in lithium-ion batteries.