Prototypical Study of Double-Layered Cathodes for Aqueous Rechargeable Static Zn-I₂ Batteries.

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous rechargeable zinc-iodine batteries (ZIBs) offer safe, low-cost, and high-energy-density solutions for grid storage.
• A major challenge in ZIBs is the shuttling of soluble triiodide ions, which degrades Coulombic efficiency.

Purpose of the Study:

• To develop a novel cathode structure for ZIBs that effectively suppresses triiodide ion shuttling.
• To improve the Coulombic and voltage efficiency of ZIBs without using ion-selective membranes.

Main Methods:

• A double-layered cathode configuration was designed, comprising a conductive layer (CL) and an adsorptive layer (AL).
• The CL (carbon cloth) and AL (polypyrrole) were integrated to facilitate ion adsorption and electrochemical reactions at their interface.
• Performance was evaluated in an aqueous ZnI2 electrolyte under high-rate intermittent conditions.

Main Results:

• The double-layered cathode successfully suppressed triiodide ion shuttling by enabling the formation and reduction of adsorbed I3- ions at the CL/AL interface.
• The ZIB prototype achieved high Coulombic efficiency (up to 95.6%) and voltage efficiency (up to 91.3%).
• Efficient operation was demonstrated even at high charge/discharge rates without ion-selective membranes.

Conclusions:

• The developed double-layered cathode is a promising strategy for enhancing ZIB performance.
• This approach offers a new pathway for designing efficient and stable ZIBs and other conversion-reaction-based batteries.
• The findings contribute to advancing safe and cost-effective energy storage solutions.