Tuning of surface morphology in Li layered oxide cathode materials

High-Ni low-Co layered LiNixCoyMnzO2 (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 LiCoO2 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.