Analyzing the effect of Li/Ni intermixing on Ni-rich layered cathode structures using atomistic simulation of the Li–Ni–Mn–Co–O quinary system

LiNixMnyCozO2 (x + y + z = 1, x > 0.6) Ni-rich layered structures are the most investigated and used cathode materials these days due to their high energy density. However, it is hard to avoid Li/Ni intermixing during synthesis and the charge/discharge cycle. This intermixing is known to degrade the cathode by inducing anisotropic stresses and phase transformations. On the other hand, some studies report that a certain amount of intermixing enhances electrochemical properties. Studying the detailed effect of the intermixing using an atomistic simulation may help in designing the cathode structure. In this paper, an interatomic potential for the Li–Ni–Mn–Co–O quinary system is developed by newly developing or modifying interatomic potentials for sub-unary, binary and ternary systems based on a second-nearest-neighbor modified embedded-atom method (2NNMEAM) formalism combined with a charge equilibration (Qeq) concept. This potential is used to analyze the effect of Li/Ni intermixing on Ni-rich cathode properties from three perspectives: lithium diffusion for rate properties, change in lattice parameter and internal stress for structural stability. The results show how the intermixing affects individual cathode properties and that controlling the intermixing will be particularly decisive in Ni-rich cathode materials. The Li–Ni–Mn–Co–O quinary potential also will be useful for analyzing and designing cathode materials.