Reversible Sodium Metal Electrodes: Is Fluorine an Essential Interphasial Component?

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Alkaline metals are promising for rechargeable battery negative electrodes.
• Fluorinated electrolytes are typically used to form protective interphases on lithium and sodium metal electrodes.
• Achieving stable and reversible sodium plating/stripping remains a significant challenge.

Purpose of the Study:

• To investigate the efficacy of fluorine-free electrolytes for sodium metal batteries.
• To develop a novel interphase that promotes reversible sodium deposition and stripping.
• To enhance the stability and cycle life of sodium metal batteries.

Main Methods:

• Utilized a sodium tetraphenylborate/monoglyme electrolyte system.
• Investigated the electrochemical performance of sodium metal electrodes in the fluorine-free electrolyte.
• Analyzed the composition and properties of the formed interphase.

Main Results:

• Achieved reversible sodium plating/stripping with an average Coulombic efficiency of 99.85% over 300 cycles.
• The interphase formed is primarily composed of carbon, oxygen, and sodium, with minimal fluorine.
• The fluorine-free interphase exhibits high stability and extremely low resistance.

Conclusions:

• A fluorine-free electrolyte strategy can effectively stabilize sodium metal electrodes.
• The developed interphase composition is key to achieving high performance and reversibility.
• This research opens a new avenue for designing advanced sodium metal batteries.