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

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 Li2Mn0.83Ni0.17O3 as the most stable phase with the lowest heat of formation. The study shows that Li2Mn0.83Ni0.17O3 is more thermodynamically stable than Li2MnO3 with a lower heat of formation. Additionally, the density of states showed that Li2Mn0.83Ni0.17O3 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, Li2Mn0.83Ni0.17O3 can be proposed as potential cathode materials for use in lithium-ion batteries.