Caging Polyhalide Anions in Polycyclodextrin for Long-Lasting Aqueous Zinc-Iodine Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Aqueous zinc-iodine batteries (AZIBs) stability is limited by polyiodide shuttling.
• Existing methods using physical trapping or electrostatic binding are ineffective due to size mismatches or weak interactions.

Purpose of the Study:

• To develop a host-guest strategy for confining polyhalide species in AZIBs.
• To improve the stability and cycle life of AZIBs using a cross-linked polycyclodextrin network.

Main Methods:

• Synthesis of a cross-linked polycyclodextrin (polyCD) network.
• Experimental and computational studies of polyhalide binding within the polyCD network.
• Electrochemical testing of AZIBs with poly(β-CD)/KI3 cathodes.

Main Results:

• The poly(β-CD) network demonstrates moderate binding affinity for polyhalide anions.
• Addition of Br- enhances polyhalide binding and inhibits hydrolysis compared to Cl-.
• AZIBs achieved 2e storage at 205 mAh/g and 4e storage at 365 mAh/g.
• Batteries demonstrated over 60,000 cycles with exceptional capacity retention.

Conclusions:

• The host-guest strategy using poly(β-CD) effectively mitigates polyhalide shuttling in AZIBs.
• This approach offers a sustainable and cost-effective method for developing long-lasting AZIBs.
• The use of biodegradable oligosaccharide-derived polymers presents a promising avenue for next-generation batteries.