Computer modeling investigation of MgV2O4 for Mg-ion batteries

Abstract

MgV2O4 is a vanadium spinel considered for rechargeable magnesium ion batteries. Its defect chemistry, solution of dopants, and the diffusion of Mg ions are investigated using advanced atomistic modeling techniques. The energetically most favorable defect is Mg–V anti-site cluster (0.53 eV/defect) assuming that a small percentage of Mg2+ and V3+ ions would exchange their positions, particularly at higher temperatures. Reaction energies for the loss of MgO via MgO Schottky and the formation of Mg vacancies via Mg Frenkel are calculated to be 5.13 eV/defect and 5.23 eV/defect, respectively, suggesting that the concentrations of these two defects will not be significant. The most favorable diffusion mechanism of Mg ions is a three-dimensional pathway, where the activation energy of migration is 0.52 eV. The formation of Mg interstitials and O vacancies can be facilitated by doping with Co2+ at the V site in MgV2O4. The electronic structures of the favorable dopants calculated using the density functional theory are discussed.