Kinetic Control of Anisotropic Grain Growth in Ni‐Rich Layered Cathodes

Abstract The particle morphology governed by anisotropic grain growth of Ni‐rich layered oxide cathodes plays a crucial role in electrochemical stability and can be tuned via element doping during the high‐temperature lithiation process. However, the fundamental impact of dopants on the anisotropic grain growth kinetics remains unclear. Herein, this work systematically investigates how dopants with different valences (Mg 2+ , Al 3+ , Zr 4+ , Ta 5+ , and Mo 6+ ) affect the anisotropic grain growth during the high‐temperature lithiation process. The findings demonstrate that the grain growth rate along the [104] and [110] directions is initially faster, followed by a higher growth rate along the [003] direction. The coarsening exponents n for the grain growth (along the [003], [104], and [110] directions) with low‐valence ions (Mg 2+ , Al 3+ ) dopants are approximately equal to 2, indicating that the grain growth depends solely on short‐range diffusion at the grain boundary. Interestingly, the n value along the [003] direction enlarges with an increase in valence. Notably, the higher valence of Mo 6+ results in a significant elevation of the exponent n along the [003] direction to 4.5, indicating a strong pinning effect due to Mo 6+ segregation at the grain boundary. This pinning impedes grain boundary migration, inhibits grain coarsening, and effectively enhances cycle stability.