Effect of Mg doping on electrochemical properties of AMO2 (with A=Li/Na and M= Mn/Fe//Ni) type electrode materials - a density functional theory study

Effect of Mg doping at the M site of layered AMO 2 (A = Li/Na and M = Fe/Mn/Ni) for enhancing its electrochemical properties were studied using density functional theory. Structurally, Mg doping was found to suppress Jahn-Teller (JT) distortion in both AMnO 2 and ANiO 2 while it acts negatively by bringing JT distortion in AFeO 2 . The simulation of density of states indicate that after Mg doping electronic conduction increase in all AM (1-x) Mg x O 2 apart from LiMn 0.5 Mg 0.5 O 2 . The diffusion barrier was found to be ≤ 1.21 eV for all the Mg undoped and doped materials. Study of open circuit voltage (OCV) indicate that with Mg doping at M site, OCV increases for all the materials due to extraction of more electrons from M during charging. For LiNiO 2 and LiNi 0.5 Mg 0.5 O 2 the OCV are found to be respectively 4.022 V and 4.557 V, with moderate diffusion barriers of 1.057 eV and 0.841 eV respectively. Again with diffusion barrier of ∼0.47 eV to 0.64 eV and large OCV of 3.83 and 3.72 V, respectively NaMn 0.5 Mg 0.5 O 2 and NaNi 0.5 Mg 0.5 O 2 are found to be the best alternative to the commercial cathode materials.