Stable Four-Electron Zinc-Iodine Battery Realized by Polyacrylamide as Catalytic Binder

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous zinc-iodine batteries (ZIBs) offer potential for high energy density but are limited by the stability of four-electron iodine reactions (I⁻/I₂/I⁺).
• Traditional methods to achieve these reactions often rely on catalytic halogen ions as electrolyte additives, which can complicate battery chemistry and performance.

Purpose of the Study:

• To investigate the use of a cost-friendly commercial binder, polyacrylamide (PAM), to catalyze stable four-electron iodine reactions in ZIBs.
• To enable high-energy-density ZIBs without the need for halogen ion additives.

Main Methods:

• Utilized commercial polyacrylamide (PAM) powder as an electrode binder in aqueous zinc-iodine batteries.
• Investigated the catalytic properties of PAM, specifically its nucleophilic -CONH₂ group, for iodine species interconversion.
• Assessed the impact of PAM on polyiodide shuttling and anode side reactions.

Main Results:

• PAM effectively catalyzed the stable interconversion between I⁰ and I⁺, enabling the desired four-electron reaction.
• The nucleophilic -CONH₂ groups in PAM strongly bind I⁺, and PAM shows affinity for polyiodide species, suppressing shuttling.
• The developed Zn-I₂ battery achieved a high capacity of 416 mAh g⁻¹ and an extended cycle life exceeding 10,000 cycles at 5 A g⁻¹.

Conclusions:

• Commercial polyacrylamide (PAM) powder serves as an effective, low-cost, and fluorine-free binder for catalyzing four-electron iodine reactions in aqueous ZIBs.
• PAM's dual function as a binder and catalyst significantly enhances battery performance by stabilizing iodine reactions and mitigating side reactions.
• This approach paves the way for developing high-energy-density and long-lasting aqueous zinc batteries.