Tuning of surface morphology in Li layered oxide cathode materials

High-Ni low-Co layered LiNi _xCo _yMn _zO ₂ (NCM, x + y + z = 1) compounds are widely used as cathode materials for the lithium-ion batteries of electrical vehicles due to their high energy density. Intrinsic chemomechanical instability and fast capacity fading of NCM degrade the battery performance; however, an emerging single-crystal particle strategy can potentially overcome these problems. In this study, we investigate possible ways of tuning the single-crystal NCM morphology by performing ab initio calculations combined with Wulff shape construction and crystal orbital Hamilton population analysis. As a result, surface structural units with different Miller indices were identified, and a linear relationship was established between the surface energy and the density of cleaved bonds. By constructing Wulff shapes, we found that LiCoO ₂ had the largest grain size among the studied NCM materials. Finally, we calculated the X–O ( X = Li, Ni, Co, or Mn) bond strengths and concluded that the NCM surface morphology can be effectively tuned by modulating the transition metal–O bond strength.