High-Entropy Rock-Salt Surface Layer Stabilizes the Ultrahigh-Ni Single-Crystal Cathode

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Single-crystalline Ni-rich layered oxides are promising for lithium-ion batteries due to structural stability.
• However, sluggish ion diffusion and interfacial issues limit performance, especially in ultrahigh-Ni (≥90%) cathodes.
• These challenges threaten the practical application of single-crystalline ultrahigh-Ni layered oxide cathodes.

Purpose of the Study:

• To address the limitations of ultrahigh-Ni single-crystalline cathode materials.
• To enhance lithium-ion diffusion kinetics and suppress interfacial degradation.
• To improve the overall rate and cycling performance of these advanced battery materials.

Main Methods:

• Development of a high-entropy coating strategy using Zr and Al doping.
• In situ construction of an epitaxial, lattice-coherent high-entropy rock-salt layer (∼3 nm) on LiNi0.92Co0.05Mn0.03O2.
• Characterization of the modified cathode material (SC-Ni92-ZA) and evaluation of its electrochemical performance.

Main Results:

• The high-entropy rock-salt surface layer significantly improved lithium-ion diffusion kinetics.
• Parasitic interfacial reactions and surface structural degradations were effectively suppressed.
• The SC-Ni92-ZA cathode showed enhanced rate capability (127.5 mAh g⁻¹ at 20C) and cycling stability (74.9% retention after 500 cycles at 1C in half-cell).
• In a full-cell configuration, SC-Ni92-ZA maintained 87.1% capacity after 600 cycles at 1C.

Conclusions:

• The epitaxial lattice-coherent high-entropy coating strategy is a viable approach for stabilizing ultrahigh-Ni single-crystalline cathodes.
• This method offers a promising pathway for developing high-capacity, long-life cathode materials for advanced lithium-ion batteries.
• The tailored surface modification effectively overcomes key limitations in next-generation battery chemistries.