Symmetry Breaking Enabled Stable Oxygen Redox in Li-Rich Cathodes via π-Type Interaction

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Stabilizing oxygen redox is critical for high-energy-density lithium-rich cathode materials.
• Achieving reversible oxygen redox by tuning oxygen energy levels remains a significant challenge.

Purpose of the Study:

• To achieve stable oxygen redox in layered Li-rich materials over the entire voltage range.
• To prevent irreversible O2 release during electrochemical cycling.

Main Methods:

• Adjusting the interlayer metal cation environment adjacent to the ligand.
• Synchrotron X-ray absorption spectroscopy (XAS) and theoretical analysis of metal-ligand orbital interactions.
• Ab initio molecular dynamics (AIMD) simulations.

Main Results:

• Confirmed charge transfer from O to Ni via π-type interaction between Ni 3d and O 2p orbitals.
• Demonstrated spontaneous symmetry breaking in Ni coordination environment after Li extraction.
• Showcased enhanced competition between anion and cation oxidation, preventing over-oxidation.

Conclusions:

• Tuning the adjacent metal environment effectively stabilizes oxygen redox reactions in Li-rich cathodes.
• Modified materials exhibit improved electrochemical performance and stable structural/interface evolution.
• Provides new insights into metal-ligand interactions governing anion redox.