Synthetic Control of Kinetic Reaction Pathway and Cationic Ordering in High-Ni Layered Oxide Cathodes

Nickel-rich layered transition metal oxides, LiNi_1−x(MnCo)_xO₂ (1−x ≥ 0.5), are appealing candidates for cathodes in next-generation lithium-ion batteries (LIBs) for electric vehicles and other large-scale applications, due to their high capacity and low cost. However, synthetic control of the structural ordering in such a complex quaternary system has been a great challenge, especially in the presence of high Ni content. Herein, synthesis reactions for preparing layered LiNi_0.7Mn_0.15Co_0.15O₂ (NMC71515) by solid-state methods are investigated through a combination of time-resolved in situ high-energy X-ray diffraction and absorption spectroscopy measurements. The real-time observation reveals a strong temperature dependence of the kinetics of cationic ordering in NMC71515 as a result of thermal-driven oxidation of transition metals and lithium/oxygen loss that concomitantly occur during heat treatment. Through synthetic control of the kinetic reaction pathway, a layered NMC71515 with low cationic disordering and a high reversible capacity is prepared in air. The findings may help to pave the way for designing high-Ni layered oxide cathodes for LIBs.

High-nickel layered oxides are promising high-capacity cathodes for next-generation lithium-ion batteries; however, synthetic control of cationic ordering in this type of material has been challenging. Herein, in situ studies are carried out on synthesis reactions for preparing LiNi_0.7Mn_0.15Co_0.15O₂ under real synthesis conditions, providing insights into thermodynamic and kinetic parameters governing cationic ordering in high-Ni layered oxides.

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