Low-cost and Non-flammable Eutectic Electrolytes for Advanced Zn-I₂ Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Eutectic electrolytes based on ZnCl2/Zn(CF3SO3)2/Zn(TFSI)2 are promising for Zn-I2 batteries but face safety and cost challenges.
• The development of safer and more economical electrolyte systems is crucial for advancing Zn-I2 battery technology.

Purpose of the Study:

• To introduce novel, safe, and cost-effective ZnSO4-based eutectic electrolytes for advanced Zn-I2 batteries.
• To investigate the solvation mechanisms and stability of these new electrolytes in polyhydric alcohol solvents.

Main Methods:

• Synthesis and characterization of ZnSO4-based eutectic electrolytes using various polyhydric alcohols.
• Electrochemical performance evaluation of Zn-I2 cells utilizing the developed electrolytes, including cycling stability and rate capability.
• Fabrication and testing of scaled-up pouch cells with high active material loading.

Main Results:

• The developed ZnSO4-based eutectic electrolytes exhibit non-flammability and significantly lower cost (<1/200) compared to traditional systems.
• Propylene glycol-based hydrated eutectic electrolyte demonstrates effective suppression of I2 shuttle effects and Zn anode side reactions.
• Zn-I2 cells show high reversibility at 1C and 91.4% capacity retention at 20C.
• Scaled-up pouch cells achieve 96.7% capacity retention after 500 cycles at a record mass loading of 33.3 mg cm-2.

Conclusions:

• ZnSO4-based eutectic electrolytes represent a safe, cost-effective, and high-performance alternative for Zn-I2 batteries.
• The interaction of polyhydric alcohol solvents with Zn2+ and water contributes to electrolyte stability.
• This research expands the scope of eutectic electrolytes for next-generation aqueous battery designs.