A bidirectional interfacial engineering strategy for highly stable sodium metal batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium metal batteries (SMBs) offer high energy density but suffer from interfacial instability, limiting cycle life.
• Anode and cathode interfaces in SMBs experience degradation, leading to rapid capacity fade.
• Developing stable interfaces is crucial for practical SMB applications.

Purpose of the Study:

• To propose and investigate a bidirectional interfacial regulation strategy for stabilizing both anode and cathode interfaces in SMBs.
• To enhance the electrochemical performance and cycle life of sodium metal batteries.
• To explore the synergistic effects of specific electrolyte additives on interfacial stability.

Main Methods:

• Utilized a mixed electrolyte containing sulfolane and fluoroethylene carbonate additives.
• Investigated the impact of additives on Na+ solvation structure and anion decomposition at the cathode.
• Analyzed the formation of a NaF-rich layer at the anode and its effect on dendrite suppression.
• Conducted cycling tests on Na||Na symmetric cells, Na||Cu cells, and Na||Na3V2(PO4)3 full cells.

Main Results:

• Sulfolane additive tailored Na+ solvation and mitigated anion decomposition at the high-voltage cathode.
• Fluoroethylene carbonate additive formed a protective NaF-rich layer on the Na metal anode, suppressing dendrites.
• Na||Na symmetric cells achieved 1400 h of stable cycling.
• Na||Cu cells demonstrated over 500 cycles of stable operation.
• Na||Na3V2(PO4)3 full cells retained over 88% capacity after 1100 cycles.

Conclusions:

• The bidirectional interfacial regulation strategy effectively stabilizes both anode and cathode interfaces in SMBs.
• The synergistic action of sulfolane and fluoroethylene carbonate enhances cycling stability and energy density.
• This approach provides a promising pathway for developing high-performance and long-lasting sodium metal batteries.