A Self-Phase-Separated Deep Eutectic Solvent-Based Biphasic Electrolyte for Durable Four-Electron Zn-I₂ Batteries...

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous four-electron zinc-iodine batteries (4eZIBs) offer potential for long-term energy storage but face challenges like zinc dendrites, polyiodide shuttle, and I+ hydrolysis.
• Existing biphasic electrolytes often use toxic organic solvents, limiting safety and temperature adaptability.

Purpose of the Study:

• To design a novel, self-stratified biphasic electrolyte for 4eZIBs that mitigates performance limitations.
• To develop a safe, eco-friendly electrolyte system suitable for extreme temperature conditions.

Main Methods:

• Liquid-liquid phase separation of a choline chloride (ChCl)-trifluoroacetamide (TFA) deep eutectic solvent (DES) and a ZnSO4/H2O/ethylene glycol aqueous solution.
• Characterization of the electrolyte's ability to confine polyiodides, stabilize I+ species, regulate Zn2+ solvation, and inhibit dendrite formation.

Main Results:

• The biphasic electrolyte effectively suppressed polyiodide shuttle and zinc dendrite growth.
• The designed Zn-I2 battery demonstrated highly reversible four-electron conversion with suppressed self-discharge.
• Exceptional cycling stability exceeding 21,000 cycles and a wide operating temperature range (-30°C to 50°C) were achieved.

Conclusions:

• The self-stratified biphasic electrolyte offers a safe and effective strategy for high-performance 4eZIBs.
• This approach provides insights into designing advanced electrolytes for demanding energy storage applications.