Dynamic Evolution of Antisite Defect and Coupling Anionic Redox in High-Voltage Ultrahigh-Ni Cathode

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Ultrahigh-nickel (Ni≥0.9) cathodes (LiNi_xCo_yMn_1-x-yO₂) offer enhanced energy density and cost-effectiveness for Li-ion batteries.
• However, Li-Ni antisite defects and their dynamic evolution during high-voltage cycling hinder performance.
• Anionic redox is another critical challenge limiting ultrahigh-Ni cathode development.

Purpose of the Study:

• To quantify the dynamic evolution of Li-Ni antisite defects in ultrahigh-Ni cathodes.
• To investigate the coupling relationship between Li-Ni antisite defects and anionic redox.
• To establish strategies for stable high-voltage cycling in these advanced battery materials.

Main Methods:

• Operando neutron diffraction was employed to monitor defect evolution during cycling.
• Electrochemical cycling was performed to assess battery performance.
• Structural analysis was conducted to correlate defect dynamics with electrochemical stability.

Main Results:

• The study quantified dynamic evolutions of Li-Ni antisite defects.
• A coupling between Ni migration, unstable oxygen lattice, and anionic redox was identified at high voltages.
• Minimized Li-Ni antisite defects and controlled Ni migration were shown to be essential for stable cycling.

Conclusions:

• Minimizing Li-Ni antisite defects and controlling Ni migration are crucial for stable high-voltage cycling in ultrahigh-Ni cathodes.
• Reduced defect evolution effectively inhibits anionic redox, enhancing cycling stability at 4.5 V.
• This research provides a pathway for developing next-generation high-energy-density Li-ion batteries.