Hydrogen Bonding Stabilizing Sodium Metal Interfaces: Toward Ultralong-Life, High-Rate, and Heatless...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium metal batteries (SMBs) face challenges with interfacial instability in succinonitrile (SN)-based deep eutectic solvents (DES).
• The interaction mechanisms between fluoroethylene carbonate (FEC) and SN, and their effect on the solid electrolyte interphase (SEI), are not well understood.

Purpose of the Study:

• To elucidate the role of FEC in stabilizing SN-based DES for SMBs.
• To investigate the formation and chemical evolution of the SEI layer.
• To evaluate the electrochemical performance and safety of FEC-modified electrolytes in SMBs.

Main Methods:

• Investigated C─F···H─C hydrogen bonding between FEC and SN.
• Analyzed competitive coordination of Na+ by FEC versus SN.
• Fabricated and tested quasi-solid-state polymer electrolytes (QSPEs) in Na||Na3V2(PO4)3 (NVP) cells.

Main Results:

• FEC-SN hydrogen bonding significantly enhances SN stability with sodium metal.
• FEC competitively coordinates with Na+, suppressing SN's role and promoting electrolyte decomposition.
• QSPEs based on SN-DES-FEC demonstrate excellent electrochemical stability, achieving 20,000 cycles at 50 C and 3,000 cycles at 3 C.

Conclusions:

• FEC acts as a crucial stabilizer in SN-based DES for SMBs through specific intermolecular interactions.
• The developed QSPEs offer superior rate capability, long-term cycling stability, and enhanced safety.
• This advancement paves the way for high-power, robust SMBs operating under demanding conditions.