The Ni/Li disordering evolution mechanisms in Ni-based layered cathode materials: insights from first-principles...

Area of Science:

• Materials Science
• Computational Chemistry
• Electrochemistry

Background:

• Ni-based layered cathode materials are crucial for high-energy density batteries.
• Ni/Li disordering is a key degradation mechanism affecting battery performance and lifespan.
• Understanding the origins of disordering is essential for designing stable cathode materials.

Purpose of the Study:

• To investigate the fundamental origins of Ni/Li disordering in Ni-based layered cathode materials.
• To establish correlations between structural and electronic factors and the extent of Ni/Li disordering.
• To identify the primary mechanism driving Ni/Li disordering during material synthesis and electrochemical cycling.

Main Methods:

• First-principles calculations were employed to simulate and analyze Ni/Li disordering.
• Systematic investigation of the relationship between interlayer distance, Li vacancies, Ni valence state, ionic radii, and coordination environments.
• Analysis of ion migration pathways and energy barriers.

Main Results:

• A strong correlation was identified between interlayer distance, Li vacancies, Ni valence state, ionic radius, and coordination polyhedron size with Ni/Li disordering.
• Pre-existing Ni/Li disorder significantly accelerates further degradation.
• Synergistic migration of Li and Ni ions was found to substantially lower migration energy.

Conclusions:

• Synergistic Li-Ni migration is proposed as the key mechanism driving Ni/Li disordering during synthesis and charge-discharge cycles.
• The findings provide critical insights into the degradation pathways of Ni-based layered cathodes.
• This understanding can guide the development of more stable and durable cathode materials for advanced batteries.