Brønsted-Lowry Acid-Based Aqueous Eutectic Electrolyte for Practical Zinc Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous highly concentrated electrolytes (AHCEs) improve cycling stability in aqueous zinc batteries (AZBs).
• Zinc chloride (ZnCl2)-based AHCEs offer good Zn anode stability but suffer from acidic pH and anion reactivity, causing component incompatibility.
• Existing electrolytes present challenges for practical AZB applications due to material interactions.

Purpose of the Study:

• To develop a pH-buffered aqueous eutectic electrolyte (AEE) for enhanced aqueous zinc battery performance.
• To address the compatibility issues of ZnCl2-based electrolytes with battery components.
• To present an efficient, simple, and low-cost electrolyte strategy for AZBs.

Main Methods:

• Formulation of an aqueous eutectic electrolyte (AEE) using ZnCl2 and sodium acetate (NaAc) based on the Brønsted-Lowry concept.
• Balancing hydrogen bonding interactions to achieve higher water coordination at lower salt concentrations.
• Characterization of electrolyte properties including electrochemical stability, transport properties, and glass transition temperature.
• Testing compatibility with vanadium oxide cathodes, aluminum current collectors, and cellulose separators.

Main Results:

• The developed pH-buffered AEE exhibits improved electrolyte properties: high electrochemical stability, enhanced transport, and low glass transition temperature.
• AEE demonstrates superior compatibility with a vanadium oxide cathode, achieving a 50% increase in capacity retention compared to saturated ZnCl2.
• The AEE effectively resolves incompatibility issues with aluminum current collectors and cellulose separators, unlike traditional ZnCl2 electrolytes.
• The electrolyte enables higher water coordination at reduced salt concentrations through optimized hydrogen bonding.

Conclusions:

• The pH-buffered AEE offers a significant advancement for aqueous zinc battery electrolytes.
• This strategy provides a cost-effective and simple solution to enhance AZB performance and component compatibility.
• The developed electrolyte paves the way for the practical application of stable and efficient aqueous zinc batteries.