Suppression of Jahn–Teller distortion by chromium and magnesium doping in spinel LiMn2O4: A first-principles study using GGA and GGA+U

Abstract

The effect of doping spinel LiMn 2 O 4 with chromium and magnesium has been studied using the first-principles spin density functional theory within GGA (generalized gradient approximation) and GGA+U. We find that GGA and GGA+U give different ground states for pristine LiMn 2 O 4 and same ground state for doped systems. For LiMn 2 O 4 the body centered tetragonal phase was found to be the ground state structure using GGA and face centered orthorhombic using GGA+U, while for LiM 0.5 Mn 1.5 O 4 (M= Cr or Mg) it was base centered monoclinic and for LiMMnO 4 (M= Cr or Mg) it was body centered orthorhombic in both GGA and GGA+U. We find that GGA predicts the pristine LiMn 2 O 4 to be metallic while GGA+U predicts it to be the insulating which is in accordance with the experimental observations. For doped spinels, GGA predicts the ground state to be half metallic while GGA+U predicts it to be insulating or metallic depending on the doping concentration. GGA+U predicts insulator-metal-insulator transition as a function of doping in case of Cr and in case of Mg the ground state is found to go from insulating to a half metallic state as a function of doping. Analysis of the charge density and the density of 2 states suggest a charge transfer from the dopants to the neighboring oxygen atoms and manganese atoms. We have calculated the Jahn-Teller active mode displacement Q 3 for doped compounds using GGA and GGA+U. The bond lengths calculated from GGA+U are found to be in better agreement with the experimental bond lengths. Based on the bond lengths of metal and oxygen, we have also estimated the average oxidation states of the dopants.

First-principles electronic structure calculations for the whole spinel oxide solid solution range MnxCo3−xO4 (0 ≤ x ≤ 3) and their comparison with experimental data

“…Other studies have already underlined the possibility of stabilising tetragonal or orthorhombic manganite spinel lattices by using different approximations. 62 3.3.2 Magnetic properties. For the lowest non-zero concentration of Mn atoms (x = 0.25), the antiferromagnetic coupling between Co A and Mn B is sufficient to set up the ferrimagnetic ordering.…”

Full picture discovery for mixed-fluorine anion effects on high-voltage spinel lithium nickel manganese oxide cathodes

“…[8][9][10][11][12] An excess of Mn 3+ could produce structural distortions and disproportionations, degrading the cycle capability during high-voltage operations. [13][14][15] Alternatively, the ordered P4 3 32 phase has a limited power density. Low electron conductivity (two orders of magnitude lower than that of the Fd-3m LNMO) caused capacity fading in the high C-rate charge-discharge reaction.…”

Surface stability of spinel MgNi0.5Mn1.5O4 and MgMn2O4 as cathode materials for magnesium ion batteries

“…The research is now focused on finding suitable electrode materials with a good electrochemical performance for magnesium ion batteries (MIBs) in order to achieve high energy capacity and safety rechargeable ion batteries for electric vehicles [4][5][6][7][8][9][10][11]. Oxides with a spinel structure such as spinel-type Mn 2 O 4 are widely used as cathode materials for lithium ion batteries (LIBs) [12,13]. Actually spinel-type LiMn 2 O 4 has been used as the cathode materials of the LIBs in electric vehicles [14,15].…”