Acetonitrile-Based Highly Concentrated Electrolytes for High-Power Organic Sodium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium croconate is a promising high-voltage organic cathode for energy-dense, cost-effective organic sodium-ion batteries (OSIBs).
• A major challenge for organic cathodes is dissolution into the electrolyte, causing poor battery cyclability.
• Developing advanced electrolytes is crucial for highly reversible OSIB performance.

Purpose of the Study:

• To engineer a novel electrolyte addressing the limitations of current OSIB systems.
• To improve the cyclability and performance of organic sodium-ion batteries.
• To investigate the role of electrolyte composition on cathode stability and battery performance.

Main Methods:

• Fabrication of an acetonitrile (AN)-based highly concentrated electrolyte (HCE) using sodium bis(fluorosulfonyl)imide (NaFSI).
• Characterization of the electrolyte's ionic conductivity and Na+ transference number.
• Testing a full-cell OSIB utilizing the developed HCE to evaluate its performance.

Main Results:

• The NaFSI:AN HCE achieved an ionic conductivity of 12.1 mS cm^-1, surpassing previous HCEs.
• The electrolyte demonstrated a high Na⁺ transference number of 0.49 at a 1:2.7 molar ratio.
• The OSIB full-cell exhibited high-power operation and enhanced capacity retention due to suppressed organic molecule dissolution.

Conclusions:

• The developed AN-based HCE effectively suppresses organic cathode dissolution in OSIB systems.
• The unique solvation structure ([2Na⁺-FSI^-] aggregate) contributes to improved battery performance and stability.
• This electrolyte represents a significant advancement for high-performance, long-lasting organic sodium-ion batteries.