Quantifying Precursor Grain‐Structure Effects on Ultrahigh‑Ni Cathode Capacity

ABSTRACT The ultra‐high Ni cathode grain, as the fundamental structural unit, is essential for lithium‐ion transport, which is governed by the precursor structure. However, the quantitative relationship between the precursor structure and cathode capacity remains unclear. Herein, we prepare Ni 0.97 Co 0.03 (OH) 2 precursors with seven different grain sizes along the [100] direction (32.28, 31.01, 32.90, 35.89, 31.81, 32.88 and 33.66 nm) via the co‐precipitation method, and systematically investigate their effects on the electrochemical performances of cathode materials. Structural and electrochemical characterization of cathodes and a series of complex analyses of the precursors’ lithiation reactions provide insight into the underlying quantitative relationship between precursor grain structure and cathode performance, i.e., larger precursor grain size ( x , nm) along the [100] direction slows lithium‐ion transport kinetics while promoting nanopore formation, ultimately influencing electrochemical performance ( y , mAh g −1 ), which can be described by the formula: y = ‐5.55* x + 421.05. This work reveals a readily overlooked structural parameter in the preparation of ultra‐high‐nickel cathodes—the precursor [100] direction grain size, which exerts a significant effect on discharge capacity. It will provide guidance for the structural design of layered cathode precursors to achieve ultra‐high capacity.