Entropy-Driven Formation of Multi-Site Coupled Network in LiNi_0.9Co_0.05Mn_0.05O₂ Cathodes for Long-Cycle Li-Ion Batteries

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_0.9Co_0.05Mn_0.05O₂ (NCM90) cathodes. By increasing the diversity of dopant atomic occupancy, the obtained (Li_0.99Mg_0.01)(Ni_0.88Co_0.05Mn_0.05Al_0.01Ti_0.01)B_0.01O₂ (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).