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[Co1/3Ni1/4Mn1/3]O-2 have been investigated using first principles calculations. One is so-called superlattice model of [root3 x root3]R30degrees-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[Co1/3M1/3Mn1/3]O-2 having a [root3 x root3]R30degrees-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 less than or equal to x less than or equal to 1/3, 1/3 less than or equal to x less than or equal to 2/3 and 2/3 less than or equal to x less than or equal to I in Li1-xCo1/3Ni1/3Mn1/3]O-2 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. (C) 2003 Elsevier Science B.V. All rights reserved.