Stepwise Dopant Selection Process for High‐Nickel Layered Oxide Cathodes

Abstract NCM‐based lithium layered oxides (LiNi 1–x–y Co x Mn y O 2 ) have become prevalent cathode materials in state‐of‐the‐art lithium‐ion batteries. Higher energy densities can be achieved in these materials by systematically increasing the nickel content; however, this approach commonly results in inferior cycle stability. The poor cycle retention of high‐nickel NCM cathodes is generally attributed to chemo‐mechanical degradation (e.g., intergranular microcracks), vulnerability to oxygen‐gas evolution, and the accompanying rocksalt phase formation via cation mixing. Herein, the feasibility of doping strategies is examined to mitigate these issues and effective dopants for high‐nickel NCM cathodes are theoretically identified through a stepwise pruning process based on density functional theory calculations. Specifically, a sequential three‐step screening process is conducted for 38 potential dopants to scrutinize their effectiveness in mitigating chemo‐mechanical lattice stress, oxygen evolution, and cation mixing at charged states. Using this process, promising dopant species are selected rationally and a silicon‐doped LiNi 0.92 Co 0.04 Mn 0.04 O 2 cathode is synthesized, which exhibits suppressed lattice expansion/contraction, fewer intergranular microcracks, and reduced rocksalt formation on the surface compared with its undoped counterpart, leading to superior electrochemical performance. Moreover, a comprehensive map of dopants regarding their potential applicability is presented, providing rational guidance for an effective doping strategy for high‐nickel NCM cathodes.