Stabilizing Iodine Redox Mediator Enables High-Performance Aqueous Zinc-Sulfur Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous zinc-sulfur batteries (AZSBs) offer high energy density and low cost but face challenges.
• Sluggish sulfur conversion kinetics and polyiodide shuttle effects impede AZSB performance.

Purpose of the Study:

• To introduce ammonia-oxidized lignin (AOL) as an electrolyte additive in AZSBs.
• To stabilize the ZnI2 redox mediator and facilitate the sulfur conversion reaction.
• To improve the overall performance and cycle life of AZSBs.

Main Methods:

• Incorporation of ammonia-oxidized lignin (AOL) into the aqueous electrolyte.
• Investigation of AOL's chemisorption and thermodynamic properties for polyiodides.
• Electrochemical characterization of AZSBs with and without AOL.

Main Results:

• AOL effectively stabilized the ZnI2 mediator by blocking mediator loss and shuttle behavior.
• The optimized AZSBs achieved a high specific capacity of 1532 mAh g⁻¹ at 0.5 A g⁻¹.
• Remarkable cycling stability was demonstrated, with 326.2 mAh g⁻¹ after 320 cycles at 2 A g⁻¹ and 514.5 mAh g⁻¹ after 134 cycles in pouch cells with high sulfur loading.

Conclusions:

• AOL significantly enhances sulfur conversion kinetics by stabilizing redox mediators.
• This approach offers a promising strategy for developing high-performance and durable AZSBs.
• The findings provide new insights into accelerating redox mediator function in AZSBs.