Solvation Rule for Solid-Electrolyte Interphase Enabler in Lithium-Metal Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Lithium-metal batteries (LMBs) offer high energy density but suffer from unstable solid-electrolyte interphase (SEI) formation.
• Electrolyte solvation behavior critically influences the electrochemical properties and stability of the lithium-metal anode.
• Developing functional electrolytes is essential for practical LMB applications.

Purpose of the Study:

• To elucidate the solvation rule governing SEI enablers in electrolyte systems for LMBs.
• To investigate the role of fluoroethylene carbonate (FEC) as an SEI enabler.
• To determine the optimal solvation number of FEC for stable LMB cycling.

Main Methods:

• Utilized fluoroethylene carbonate (FEC) as an SEI enabler for lithium-metal anodes.
• Analyzed the solvation status of FEC in the electrolyte system.
• Evaluated the stability of the SEI layer formed on the lithium metal surface.
• Assessed the cycling performance of LMBs with FEC-containing electrolytes.

Main Results:

• Demonstrated that a solvation number of fluoroethylene carbonate (FEC) greater than or equal to one (≥1) is required for stable SEI formation.
• Showcased that FEC's sacrificial reduction contributes to the formation of a robust SEI layer.
• Achieved relatively stable cycling performance in LMBs by optimizing FEC solvation.

Conclusions:

• The solvation number of FEC is a critical parameter for achieving stable SEI formation in LMBs.
• A minimum solvation number of one for FEC ensures the formation of a protective SEI layer.
• This understanding facilitates the rational design of electrolytes for high-performance lithium-metal batteries.