# Surface Reconstruction as a Design Principle for Ni‐rich Cathodes

## TL;DR

This paper shows how turning surface NiO into a protective layer improves battery performance and durability of Ni-rich cathodes.

## Contribution

Reframing surface NiO as a functional design principle for stabilizing Ni-rich cathodes through controlled oxygen vacancy-induced phase transformation.

## Key findings

- Surface NiO formed via oxygen vacancies stabilizes NMC811 cathodes, improving cycling performance.
- Electrochemical tests show enhanced capacity, higher Li+ diffusivity, and lower resistance.
- X-ray and microscopy techniques confirm structural stability and reduced heterogeneity after modification.

## Abstract

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 LiNiO2 (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 LiNi0.8Mn0.1Co0.1O2 (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.

A comprehensive understanding of how controlled surface reconstruction via oxygen vacancy‐induced NiO formation enhances the electrochemical performance of Ni‐rich cathodes is presented. This work reframes inert phase formation as a functional design principle, enabling scalable surface protection and improving the cycling performance of NMC811.© 2026 WILEY‐VCH GmbH