Multi‐Hierarchical Structure Engineering Enables Superior Cycling Stability in Single‐Crystal Ultrahigh‐Nickel Cathodes

Ultrahigh‐nickel layered oxides are considered promising cathodes due to their high‐energy‐density. However, their practical application is limited by rapid structural degradation from surface to bulk, such as severe interfacial side reactions and dramatic lattice distortion. Here, we report a multi‐hierarchical single‐crystal LiNi 0.97 Co 0.01 Mn 0.02 O 2 cathode, which is achieved through a high‐low‐temperature calcination process combined with the effect of Nb/Mo on local structural reconstruction. The modified cathode exhibits a multi‐hierarchical structure with lattice matching, including composed of spinel‐like domains and a thin rock‐salt‐like surface layer. The rock‐salt‐like surface layer reduces cathode/electrolyte reactivity and suppresses lattice oxygen loss, while the spinel‐like domains mitigate severe lattice strain and crack formation. Furthermore, Nb/Mo co‐doping also enhances the Li + diffusion kinetics in the layered structure, thereby achieving multiscale structural improvements from surface to bulk. The results show that the modified cathode maintains high electrochemical activity after long‐term cycling, demonstrating reduced fatigue phase formation and limited electrolyte decomposition. Consequently, the prepared cathode delivers a high initial discharge capacity of 228.6 mAh g −1 at 0.1 C and an excellent capacity retention of 81.84% after 300 cycles at 1.0 C. This work proposes a multi‐level structural design strategy, offering new insights for the preparation of high‐energy‐density cathodes.