Can We See SEI Directly by Naked Eyes?

Area of Science:

• Electrochemistry
• Materials Science
• Battery Technology

Background:

• A stable solid electrolyte interface (SEI) is critical for enhancing the electrochemical performance of lithium metal batteries (LMBs).
• Understanding SEI formation is challenging due to complex reactions and a lack of direct observation methods.

Purpose of the Study:

• To develop a method for direct observation and quantification of the SEI in LMBs.
• To investigate the formation, distribution, and evolution of SEI during battery cycling.

Main Methods:

• Design and synthesis of novel fluorescent tracers as electrolyte additives.
• Utilizing tracers with olefin, polar, and AIEgen moieties for SEI participation and fluorescence.
• Directly observing and quantifying SEI using its intrinsic fluorescence signal.

Main Results:

• Successfully achieved direct visualization of the SEI film with intrinsic fluorescence.
• Enabled quantification of SEI distribution, relative abundance, and macro morphology.
• Revealed the regularity of SEI formation, growth, and destruction during charge/discharge cycles.

Conclusions:

• The fluorescent tracers provide unprecedented insight into SEI behavior in LMBs.
• Understanding SEI evolution aids in optimizing electrolyte-anode interactions for improved battery performance and cycle life.
• This method enriches knowledge of SEI morphology and dynamics, crucial for advancing battery technology.