Multi‐Cation Synergistic Confinement Enables Long‐Cycling Ultrahigh‐Nickel Cathodes

The growing demand for high‐specific‐energy batteries has driven significant interest in ultrahigh‐nickel‐layered oxide cathodes. However, rapid structural degradation during cycling remains a critical barrier to their large‐scale commercialization. Herein, a multi‐cation synergistic confinement strategy to enhance the structural stability of ultrahigh‐nickel LiNi _0.9 Co _0.06 Mn _0.04 O ₂ (NCM90) cathodes is reported. Zr, Mg, and Al are robust gradient‐diffused into the NCM90 lattice during in situ synthesis, leveraging the strong ZrO and AlO bonding energies to mitigate lattice distortion. Additionally, the pillar effect of Mg ²⁺ in the Li layer helps preserve structural integrity during charge/discharge cycles. Meanwhile, Zr ⁴⁺ segregates on the surface of the NCM90 lattice, forming a Li _x Zr _y O _z coating that effectively alleviates interfacial side reactions. As a result, the Zr/Mg/Al ‐ co‐doped NCM90 (NCM–ZMA) achieves a superior capacity retention of 94.2% after 200 cycles at 1 C (2.8–4.3 V), significantly outperforming the pristine NCM90 (82.5%). This work demonstrates that a rational doping strategy, integrating both crystal structure design and interface engineering, can maximize the long‐term cyclability of ultrahigh‐nickel cathodes, paving the way for their widespread application in high‐energy battery systems.