First principles investigation of the structure and stability of LiNiO ₂ doped with Co and Mn

The structures of LiNiO₂ doped with Co and Mn were investigated. The distributions of the transition metals (TMs) throughout the crystal were examined using density functional theory calculations, and the underlying mechanism was analyzed based on molecular orbital methods. The positions of the Li ions in de-lithiated material states were also investigated, and the mechanism underlying the structural stabilization introduced by the Co and/or Mn atoms is discussed. The crystal was found to be most stable if Co and Mn were present in the same layer. This TM distribution eased stress arising from differences in the TM-O bond length caused by the different effective charges of the transition metals. Li ions were preferentially located in the Li layer closest to the Co and Mn layers. Thus, a cluster containing Co, Mn, and Li ions is expected to persist, even under highly de-lithiated states. These results explain the improved stability of LiNiO₂ upon the introduction of Co and/or Mn.