Boosting Fast‐Charging Performance of Ni‐Rich NCM9055 Cathodes with Nb ₂ O ₅ Dual Functional Modification

ABSTRACT Polycrystalline Ni‐rich layered oxides are promising cathodes for Li‐ion batteries of high‐power density and long cycle life. However, their practical application is still hindered by the sluggish Li ⁺ diffusion rate and reaction inhomogeneity during redox cycles. In this work, LiNi _0.9 Co _0.05 Mn _0.05 O ₂ (NCM9055) cathode with a desired internal radial structure was designed and successfully synthesized using Nb ₂ O ₅ as a dual‐functional structural and interfacial modulator. During calcination, the Nb ₂ O ₅ reacts to form an intergranular LiNbO ₃ phase at grain boundaries. This phase, forming before high‐temperature grain growth, acts as a structural modulator to preserve the desirable radial alignment of primary particles by impeding random grain growth. It also functions as an interfacial conductor, creating fast Li ⁺ diffusion pathways along the grain boundaries. These structural and interfacial modifications synergistically mitigate chemical inhomogeneity and relieve accumulated strain during cycling. Consequently, the Nb‐modified NCM9055 exhibits superior electrochemical performance, delivering an excellent rate capacity (152.4 mA h g ^{− 1} at 10 C) and robust cycling stability under high‐rate conditions (83.0% capacity retention after 500 cycles at 5C). These findings clarify the mechanism of Nb modulation and demonstrate a robust strategy for preserving desirable microstructures in high‐rate, Ni‐rich cathode materials.