Quantitative Operando EPR Method on Redox-Active Ions in Electrode Materials: Considering the Conversion-Type...

Area of Science:

• Electrochemistry
• Materials Science
• Spectroscopy

Background:

• Electron paramagnetic resonance (EPR) is valuable for studying electrochemical systems with narrow spectral lines.
• Interpreting broad, featureless EPR signals from ions in solid materials, like those in electrodes, is challenging.
• Understanding these signals is crucial for optimizing energy storage devices.

Purpose of the Study:

• To develop a quantitative operando EPR method for analyzing redox-active ions in electrode materials.
• To establish a relationship between spin and electron transfer amounts for signal assignment.
• To demonstrate the method's utility in revealing detailed electrode processes.

Main Methods:

• Development of a quantitative operando electron paramagnetic resonance (EPR) technique.
• Establishing a correlation between absolute spin quantities and electron transfer.
• Application to four manganese-based conversion electrode materials (MnO, MnF2, Mn2O3, MnF3).

Main Results:

• Accurate interpretation of broad, featureless EPR signals from ions in electrode materials.
• Detailed elucidation of electrode processes, including redox mechanisms and structural changes.
• Identification of transition metal dissolution during electrochemical cycling.
• Successful differentiation between Kramers and non-Kramers ion behavior.

Conclusions:

• The developed quantitative operando EPR method provides a robust strategy for interpreting complex spectral data.
• This approach enhances the understanding of electrochemical mechanisms in electrode materials.
• It offers significant potential for advancing research in critical areas like battery cathode development.