Charge Transfer Effect in Layered Cathodes Through MEMS-Based In Situ TEM Studies

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Irreversible lattice oxygen release is a key failure mechanism in layered oxide cathodes.
• This degradation is typically linked to phase transitions and reduced oxygen content.

Purpose of the Study:

• To investigate the early degradation mechanisms in oxygen vacancy defective layered oxide cathodes.
• To understand the role of local oxygen vacancy heterogeneity in cathode degradation.

Main Methods:

• Electron energy loss spectroscopy (EELS) to analyze elemental and electronic structure changes.
• Density functional theory (DFT) simulations to model atomic migration and electronic interactions.
• Investigation of oxygen vacancy defective layered cathodes.

Main Results:

• An anomalous metal segregation pathway was observed in defective cathodes, occurring before phase transitions.
• Early charge transfer from oxygen 2p to manganese (Mn) 3d orbitals was identified as the cause.
• Local oxygen vacancy heterogeneity significantly reduces the migration barrier for Mn.
• Oxygen release initiates from defective sites, not perfect crystal regions, changing the degradation pathway.

Conclusions:

• Local oxygen vacancy heterogeneity plays a critical role in the phase degradation of layered cathodes.
• The findings challenge the conventional understanding of cathode degradation pathways.
• Early metal segregation due to vacancy-induced Mn migration is a crucial factor in layered cathode failure.