New insight into the solid electrolyte interphase with use of a focused ion beam
Hong-Li Zhang1, Feng Li, Chang Liu
1Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China.
The Journal of Physical Chemistry. B
|July 21, 2006
Summary
The solid electrolyte interphase (SEI) film on natural graphite spheres evolves with cycling, showing increased thickness, cracks, and organic content. This study introduces the concept of an "internal SEI film."
Area of Science:
- Materials Science
- Electrochemistry
- Surface Science
Background:
- The solid electrolyte interphase (SEI) is crucial for lithium-ion battery performance.
- Understanding SEI formation and evolution on graphite anodes is key to improving battery longevity.
Purpose of the Study:
- To investigate the formation and evolution of the SEI film on natural graphite spheres.
- To characterize SEI morphology, composition, and structural changes during electrochemical cycling.
- To propose the concept of an "internal SEI film" and discuss capacity fading mechanisms.
Main Methods:
- Focused Ion Beam (FIB) technology for high-resolution imaging of SEI morphology.
- Secondary electron FIB imaging for surface and cross-section analysis.
- Elemental Line Scan Analysis (ELSA) to determine SEI composition variations.
Main Results:
- Initial SEI film (450-980 nm) is rough, nonuniform, and contains splits.
- Electrochemical cycling leads to SEI thickening, microscale holes, cracks, and increased organic content.
- The existence of an "internal SEI film" was proposed based on cross-section analysis.
Conclusions:
- SEI evolution significantly impacts natural graphite anode performance.
- The proposed "internal SEI film" offers new insights into SEI behavior.
- Understanding these SEI changes is vital for mitigating capacity fading in lithium-ion batteries.
