Sodium Ion Batteries using Ionic Liquids as Electrolytes

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Sodium is an abundant and evenly distributed element, making it a cost-effective raw material for large-scale battery production.
• Ionic liquids offer enhanced safety due to their non-volatile and non-flammable properties, improving battery reliability.
• Higher operating temperatures enabled by ionic liquids enhance electrode reactions and mass transfer, boosting battery performance.

Purpose of the Study:

• To develop and evaluate sodium ion batteries utilizing ionic liquids as electrolytes.
• To investigate the performance of various electrode materials in conjunction with ionic liquid electrolytes.
• To assess the safety, energy density, and cycle life of a prototype sodium ion battery.

Main Methods:

• Ionic liquids, specifically binary systems of sodium and quaternary ammonium salts, were synthesized and characterized for use as electrolytes.
• Various positive and negative electrode materials were screened for compatibility with the ionic liquid electrolytes.
• A 27 Ah full cell was assembled using sodium chromite (NaCrO2) as the positive electrode and hard carbon as the negative electrode.

Main Results:

• The fabricated sodium ion battery achieved a gravimetric energy density of 75 Wh/kg and a volumetric energy density of 125 Wh/L.
• The battery demonstrated excellent capacity retention, maintaining 87% after 500 cycles.
• The use of ionic liquids significantly improved battery safety and extended operational temperature ranges.

Conclusions:

• Sodium ion batteries with ionic liquid electrolytes represent a promising and safer alternative for large-scale energy storage.
• Further advancements in electrode materials and cell design are expected to enhance energy density and overall cell performance.
• The abundance of sodium and the safety features of ionic liquids position these batteries for widespread adoption in grid storage solutions.