Surface Reconstruction as a Design Principle for Ni-rich Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Surface reconstruction in nickel-rich cathodes is typically a degradation pathway.
• Formation of inert phases like NiO is often associated with battery failure.

Purpose of the Study:

• To leverage the surface NiO phase as a stabilizing element in nickel-rich cathodes.
• To develop a materials-intrinsic and scalable method for enhancing battery durability.

Main Methods:

• Density functional theory (DFT) calculations to predict NiO stability.
• Variable temperature X-ray diffraction (VTXRD) to control surface phase transformation.
• X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM) for structural analysis.
• Electrochemical techniques (cycling, CV, EIS) to evaluate performance.

Main Results:

• A core-shell structure with a protective NiO surface layer was successfully created on NMC811.
• Modified cathodes exhibited improved capacity, enhanced Li+ diffusivity, and reduced resistance.
• Bulk oxidation state remained unchanged, and structural heterogeneity was reduced.

Conclusions:

• Surface NiO can be controllably engineered as a beneficial component, not a defect.
• This approach offers a scalable route to improve the cycle life of high-nickel battery cathodes.
• Reframing surface reconstruction as a design principle enhances battery longevity.