Boosting Fast-Charging Performance of Ni-Rich NCM9055 Cathodes with Nb₂O₅ Dual Functional Modification

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_0.9Co_0.05Mn_0.05O₂ (NCM9055) cathode with a desired internal radial structure was designed and successfully synthesized using Nb₂O₅ as a dual-functional structural and interfacial modulator. During calcination, the Nb₂O₅ reacts to form an intergranular LiNbO₃ 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.