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Operando studies of solid electrolyte interphase (SEI) formation with the electrochemical-surface force balance
1Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, OX1 3QZ, UK. susan.perkin@chem.ox.ac.uk.
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|July 28, 2026
Summary
The electrochemical-surface force balance (e-SFB) directly observes solid electrolyte interphase (SEI) formation on electrode surfaces. This technique measures SEI thickness and mechanical properties in situ for lithium-ion battery research.
Area of Science:
- Electrochemistry
- Materials Science
- Surface Science
Background:
- Solid electrolyte interphase (SEI) formation is critical for lithium-ion battery performance and longevity.
- Understanding SEI properties requires in situ characterization methods capable of direct observation.
Purpose of the Study:
- To demonstrate the utility of the electrochemical-surface force balance (e-SFB) for direct observation of SEI formation.
- To measure the in situ thickness and mechanical properties of SEIs formed in LiTFSI-based electrolytes.
Main Methods:
- Utilized the electrochemical-surface force balance (e-SFB) technique.
- Performed proof-of-concept measurements on lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) based electrolytes.
- Conducted in situ measurements before and after electrochemical cycling.
Main Results:
- Successfully observed SEI formation directly at the electrode surface using e-SFB.
- Quantified SEI thickness in the hundreds of nanometers.
- Measured SEI elastic moduli in the tens of megapascals, varying with cycling conditions and solvent composition.
Conclusions:
- The e-SFB is a powerful tool for direct in situ characterization of SEI formation and properties.
- SEI mechanical properties are dependent on electrochemical cycling and electrolyte composition.
- This technique provides crucial insights for designing more stable and efficient lithium-ion batteries.
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