Sole-Solvent High-Entropy Electrolyte Realizes Wide-Temperature and High-Voltage Practical Anode-Free Sodium Pouch...

Area of Science:

• Electrochemistry and Materials Science
• Energy Storage Technologies

Background:

• Anode-free sodium batteries (AFSBs) offer high energy density but face challenges with electrolyte compatibility at high voltages and wide temperature ranges.
• Existing electrolytes struggle to maintain stability on both cathode and anode interfaces under demanding operating conditions.

Purpose of the Study:

• To develop a novel electrolyte enabling stable, high-voltage operation of AFSBs across a wide temperature spectrum (-20 to 60 °C).
• To investigate the mechanism behind the electrolyte's enhanced performance and electrode interface stabilization.

Main Methods:

• Development of a sole-solvent high-entropy electrolyte using diethylene glycol dibutyl ether (D2) and NaPF6 salt.
• Electrochemical cycling of AFSBs within the -20 to 60 °C range.
• Analysis of electrode-electrolyte interphases using advanced characterization techniques.

Main Results:

• Achieved stable cycling of high-voltage AFSBs over a wide temperature range (-20 to 60 °C) for the first time.
• Demonstrated formation of stable anion-derived interphases on both cathode and anode due to unique solvent-ion effects.
• Fabricated ampere-hour (Ah)-level anode-free sodium pouch cells with a high energy density of 209 Wh kg⁻¹ and 83.1% capacity retention after 100 cycles.

Conclusions:

• A novel sole-solvent high-entropy electrolyte enables practical, wide-temperature operation of high-voltage AFSBs.
• The electrolyte's design facilitates entropy-driven salt dissociation and stable interphase formation, overcoming key limitations.
• This research provides a promising pathway for designing advanced electrolytes for next-generation high-performance AFSBs.