Identifying Electrolyte Reduction Intermediates in Lithium Metal Batteries with Spin Trapping

Area of Science:

• Electrochemistry
• Materials Science
• Organic Chemistry

Background:

• Understanding solid electrolyte interphase (SEI) formation is critical for advancing lithium metal battery technology.
• Current methods struggle to elucidate the mechanisms of SEI formation from electrolyte components.

Purpose of the Study:

• To establish a novel spin trapping approach for identifying radical intermediates during electrolyte reduction.
• To gain direct insights into the mechanisms governing SEI formation.

Main Methods:

• Employing spin trapping combined with electron paramagnetic resonance (EPR) spectroscopy.
• Utilizing liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) spectroscopy for radical identification.
• Investigating SEI properties using titration and spectroscopic techniques.

Main Results:

• Identified three distinct radical intermediates during fluoroethylene carbonate reduction, confirming a ring-opening mechanism.
• Demonstrated the utility of spin trapping for comprehensive radical characterization.
• Observed that inhibiting organic SEI formation leads to decreased stability and increased anion decomposition.

Conclusions:

• Direct characterization of radical intermediates in battery interphase formation is achieved for the first time.
• The study provides new insights into complex electrolyte reduction mechanisms.
• Established a valuable new approach for studying SEI formation and function in batteries.