The intrinsic behavior of lithium fluoride in solid electrolyte interphases on lithium

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Lithium metal anodes are crucial for high-energy density batteries.
• The native solid electrolyte interphase (SEI) on lithium anodes causes issues like dendrite growth.
• Enriching the SEI with lithium fluoride (LiF) is a strategy to improve lithium cycling, but LiF's role is unclear.

Purpose of the Study:

• Investigate the stability and function of LiF in LiF-enriched SEIs.
• Determine the effect of LiF source (artificial vs. electrolyte-derived) on lithium electrode behavior.
• Clarify the intrinsic role of LiF in SEI performance.

Main Methods:

• Studied LiF stability in preformed and electrolyte-derived LiF-enriched SEIs.
• Examined lithium electrode behavior under plating conditions.
• Analyzed the dynamic changes and repair mechanisms of the SEI interface.

Main Results:

• The mechanical integrity of LiF is compromised during lithium plating.
• LiF alone is insufficient for protecting the lithium anode.
• In situ electrolyte-mediated repair, forming LiF or elastomeric layers, is critical for performance.

Conclusions:

• The LiF-enriched SEI is dynamic, not static.
• Electrolyte-driven interface regeneration is more important than intrinsic LiF stability.
• Future battery designs should consider the interplay between ionic layers and electrolyte-derived components.