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

Abstract Nickel‐rich layered transition metal oxides, LiNi 1− x (MnCo) x O 2 (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 0.7 Mn 0.15 Co 0.15 O 2 (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.