Crystal and electronic structures of superstructural Li1−x[Co1/3Ni1/3Mn1/3]O2 (0≤x≤1)

Crystal and electronic structures of two model crystals for Li[Co1/3Ni1/3Mn1/3]O2 have been investigated using first principles calculations. One is so-called superlattice model of [√3×√3]R30°-type in triangular lattice of sites and the other is piled-up model among CoO2, NiO2 and MnO2 slabs. For both models, the formal charges of Co, Ni and Mn are, respectively, estimated to be +3, +2 and +4 from the interatomic distances and electronic structures. The formation energy for a superlattice model is −0.17 eV while that for a piled-up model is +0.06 eV, indicating that Li[Co1/3Ni1/3Mn1/3]O2 having a [√3×√3]R30°-type superlattice can be prepared when the processing method is exploited. The solid-state redox reactions in a superlattice model are also calculated and predicted that the reaction in the ranges of 0≤x≤1/3, 1/3≤x≤2/3 and 2/3≤x≤1 in Li1−x[Co1/3Ni1/3Mn1/3]O2 consists of Ni2+/Ni3+, Ni3+/Ni4+ and Co3+/Co4+, respectively, with smaller change in unit-cell volume associated with lithium insertion reaction than those of LiCoO2, LiNiO2 and LiMnO2.