Entropy‐Driven Formation of Multi‐Site Coupled Network in LiNi 0.9 Co 0.05 Mn 0.05 O 2 Cathodes for Long‐Cycle Li‐Ion Batteries

ABSTRACT Ni‐rich layered oxides have emerged as leading candidates for next‐generation high‐energy lithium‐ion batteries (LIBs), leveraging superior specific capacity and cost‐effectiveness. However, the practical application of high‐nickel cathodes is hampered by inherent structural challenges, primarily due to bulk‐phase TM‐O framework collapse and surface deterioration during prolonged cycling. In this study, we address these challenges through B‐Mg‐Al‐Ti entropy‐driven multi‐site doping in LiNi 0.9 Co 0.05 Mn 0.05 O 2 (NCM90) cathodes. By increasing the diversity of dopant atomic occupancy, the obtained (Li 0.99 Mg 0.01 )(Ni 0.88 Co 0.05 Mn 0.05 Al 0.01 Ti 0.01 )B 0.01 O 2 (HE‐NCM90) cathode establishes a multi‐site reinforced network that substantially strengthens TM─O bonding interactions, as evidenced by a 68% reduction in Ni─O bond shrinkage in the charged state. This strategy establishes a graded architecture comprising: (i) a B‐enriched high‐entropy surface layer that stabilizes lattice and surface oxygen via robust Li‐O‐B coordination (7.9% reduction in O 2p IDOS near Fermi level) and strengthened TM─O bonds, suppressing parasitic reactions; and (ii) a high‐entropy bulk matrix that mitigates irreversible phase transitions, as reflected by a 26.4% reduction in the (003) peak shift. Such hierarchical structural engineering enables synergistic stabilization of both surface and bulk phase integrity. Consequently, the HE‐NCM90 cathode demonstrates exceptional cycling stability, delivering 98.76% capacity retention after 100 cycles at 1C (2.7–4.3V) and 93.37% retention at 0.5C (2.7–4.4V).