Surface Reconstruction as a Design Principle for Ni‐rich Cathodes

Surface reconstruction by formation of inert phases in Ni‐rich cathodes is widely viewed as a degradation mechanism for batteries. Herein, this seemingly undesirable phase is leveraged to stabilize Ni‐rich cathodes. Density functional theory reveals a reduction in Ni 3d–O 2p hybridization in NiO compared to LiNiO 2 (LNO), suggesting its potential as a protective layer. Guided by theory, variable temperature X‐ray diffraction is used to identify optimal conditions for introducing oxygen vacancies on the surface of LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) particles, which triggers a phase transformation from layered to rock‐salt NiO on the surface, creating a core–shell structure as evidenced by X‐ray photoelectron spectroscopy and scanning transmission electron microscopy (STEM). Electrochemical methods such as constant‐current long‐term cycling, cyclic voltammetry, and electrochemical impedance spectroscopy reveal improved capacity, higher Li + diffusivity, and lower resistance during cycling. X‐ray absorption spectroscopy confirms that the bulk‐averaged oxidation state remains unchanged after modification, and STEM imaging confirm reduced structural heterogeneity. By reframing surface NiO as a controllable design principle, a materials‐intrinsic, scalable route to extend the durability of Ni‐rich cathodes is offered.