What is the Role of Nb in Nickel-Rich Layered Oxide Cathodes for Lithium-Ion Batteries?

Nickel-rich layered metal oxide LiNi1-y-zMnyCozO2 (1 - y - z >= 0.8) materials are the most promising cathodes for next-generation lithium-ion batteries in electric vehicles. However, they lose more than 10% of their capacity on the first cycle, and interfacial/structural instability causes capacity fading. Coating and substitution are possible direct and effective solutions to solve these challenges. In this Letter, Nb coating and Nb substitution on LiNi0.8Mn0.1Co0.1O2 (NMC811) is easily produced through a scalable wet chemistry method followed by sintering from 400 to 800 degrees C. A Li-free Nb oxide treatment is found to remove surface impurities forming a LiNbO3/Li3NbO4 surface coating, to reduce the first capacity loss and to improve the rate performance. Nb substitution stabilizes the structure, as evidenced by less heat evolution on heating, thus providing better long cycling stability with a 93.2% capacity retention after 250 cycles.