Spinel Type Of Lithium-ion Battery Cathode Material Of Li <sub> X </ Sub> Mn <sub> 2 </ Sub> The O <sub> 4 </ Sub> First-principles Study

Study of lithium manganese oxide for lithium battery cathode materials by first-principles are now focusing mainly on the phase transformations, electronic structures and transitional metal doping. To nonstoichiometric spinel Li_xMn₂O₄, the formation energies and electronic structures for oxygen-deficient LiMn₂O_4-y are only investigated. To the best of my knowledge, there is no report on Li_1±xMn₂O₄.The goal of this work is to understand the properties of defect spinels Li_1±xMn₂O₄. With the first-principles ultrasoft pseudopotenial method and the expansion of the plane waves as implemented in the Materials Studio program CASTEP code, we have investigated the effect of lithium-deficient and lithium-rich on the total energy, formation energy, density of states, partial density of states, phase diagram and average potential as well as theoretical capacity for the spinel Li_1±xMn₂O₄.For defect spinels Li_1±xMn₂O₄, with an increase in lithium content, the lattice parameter gradually increases, the total energy and the average potential gradually decreases. In addition, the theoretical capacity decreases with an increase in lithium content or the Li/Mn molar ratio.A negative formation energy for lithium-deficient spinel Li_1-xMn₂O₄ (0≤x≤1) indicates that the material is stable with respect to phase separation into MnO₂ and LiMn₂O₄. A positive formation energy for lithium-rich spinel Li_1±xMn₂O₄ (0≤x≤1) indicates that the material is unstable. As the result of Jahn-Teller distortion, the crystal structure transforms from cubic symmetry to tetragonal symmetry, space group transforms from Fd3m to I4₁/amd, and phase transforms from cubic phaseto tetragonal phase.