Operando Magnetism on Oxygen Redox Process in Li-Rich Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Lithium-rich layered oxides offer high energy density for advanced batteries.
• The oxygen redox mechanism in these materials is not fully understood.
• Understanding oxygen redox is key to improving battery performance.

Purpose of the Study:

• To investigate the oxygen redox mechanism in Li_1.2Mn_0.6Ni_0.2O₂ using in situ magnetism.
• To correlate magnetic and electronic structure evolution with electrochemical cycling.
• To provide insights into designing high-performance cathode materials.

Main Methods:

• In situ magnetism measurements to track real-time magnetization changes.
• Electrochemical cycling of Li_1.2Mn_0.6Ni_0.2O₂ cathode material.
• Comprehensive in/ex situ characterizations and density functional theory (DFT) calculations.

Main Results:

• Magnetization decreases during charging, with a notable upturn above 4.6 V.
• The magnetization rebound is linked to evolving lattice oxygen interactions (Mn-O to O-O bonding).
• Decreased magnetization after cycling indicates irreversible structural changes and capacity fade.

Conclusions:

• The study elucidates the oxygen redox mechanism in lithium-rich layered oxides via in situ magnetism.
• The findings highlight the transition from π-type to σ-type bonding during oxygen redox.
• This research offers guidance for developing next-generation high-energy-density battery materials.