Ion-Solvent Complexes Promote Gas Evolution from Electrolytes on a Sodium Metal Anode

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Lithium and sodium metal batteries offer high energy densities but suffer from reactivity issues.
• Alkali metal reactivity with organic electrolytes leads to electrolyte depletion, cell failure, and gas evolution.

Purpose of the Study:

• To investigate the mechanism of organic electrolyte decomposition and gas evolution on sodium metal anodes.
• To understand the role of ion-solvent complexation in alkali metal anode stability.
• To provide guidance for designing safer electrolytes and anodes for rechargeable batteries.

Main Methods:

• Utilized first-principles calculations to model electrolyte-electrode interactions.
• Employed in situ optical microscopy to observe reactions on the sodium metal anode surface.

Main Results:

• Identified that complexation with sodium ions reduces the LUMO of solvent molecules.
• Demonstrated that this reduction facilitates electrolyte decomposition and gas evolution.
• Showed this mechanism is applicable to lithium and other metal anodes.

Conclusions:

• Ion-solvent complexation is critical for the stability of alkali metal anodes.
• The study reveals the underlying mechanism of electrolyte gassing in metal batteries.
• Findings offer mechanistic insights for developing stable electrolytes and anodes.