Selective dopant segregation modulates mesoscale reaction kinetics in layered transition metal oxide

Highlights: • The impact of Zr modification on single crystalline NMC material was investigated from electrochemical kinetics perspective. • The facet dependent Zr distribution on the NMC particle can modulate the Li-ion diffusion pathways. • The electrochemical kinetically favored corners on the mesoscale were uncovered with advanced synchrotron imaging techniques. Incorporation of foreign elements into the cathode material is broadly adopted by both academia and industry to improve the battery performance. The lack of an in-depth understanding for the underlying mechanism, however, makes it a largely try-and-error process with unsatisfactory efficiency and effectiveness. This is particularly true for the electrochemical reaction kinetics that is heterogeneous over a broad range of length scales and is determined collectively by the cathode's electronic structure, lattice configuration, and micro-morphology. Here we unveiled a facet-dependent dopant segregation effect in Zr-modified single-crystal LiNi_0.6Co_0.2Mn_0.2O₂ cathode. By forming kinetically favored corners on the cathode particles, the presence of a trace amount of Zr critically modulates the mesoscale reaction kinetics. Our findings suggest that a delicately controlled dopant distribution is a viable strategy for designing the next-generation battery cathode with superior structural and chemical robustness.