Synergistic Nb Doping and Carbon Coating for Stabilized Ultrahigh-Ni-Layered Cathodes in Durable Lithium-Ion Batteries

Ultrahigh-Ni layered oxides, LiNi x Co y Mn 1– x – y O 2 ( x ≥ 0.85), have attracted increasing attention as promising cathode materials for high-energy-density lithium-ion batteries (LIBs). However, structural instability during the cyclic charge/discharge process limits their widespread application. Here, we present a bulk and interfacial synergistic modification strategy that combines trace (∼1%) Nb doping with carbon coating to improve the electrochemical performances of LiNi 0.9 Co 0.05 Mn 0.05 O 2 (NCM90) cathodes. The introduction of Nb doping stabilizes the crystal structure and accelerates Li + ion diffusion by expanding the interslab spacing of the layered channels in NCM90. Simultaneously, the Ketjen black carbon coating effectively reduces the interfacial resistance and shields the NCM90 cathodes from harmful electrolyte corrosion. Our developed dual modification leads to a synergistic effect, unlocking remarkable improvements in both electrochemical performance and structural stability of NCM90. The optimized Nb-doped NCM90@C delivers exceptional rate capability (∼121 mAh g –1 at 10 C) and cyclic performance (∼192 mAh g –1 after 100 cycles at 0.5 C). Notably, voltage and capacity decay during cycling is significantly suppressed, showcasing the powerful impact of this synergistic strategy in enhancing the stability and lifespan of ultrahigh-Ni layered cathodes for next-generation LIBs.