Electroactive ferrocene/ferrocenium redox coupling for shuttle-free aqueous zinc-iodine pouch cells

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous zinc-iodine batteries offer safety and rate advantages for grid storage.
• Conventional iodine cathodes suffer from low energy density and shuttle effects due to poor polyiodide interaction.

Purpose of the Study:

• To enhance energy density and suppress shuttle effects in zinc-iodine batteries.
• To introduce an electroactive redox coupling strategy using ferrocene.

Main Methods:

• Incorporation of ferrocene into iodine cathodes.
• Investigation of ferrocene/ferrocenium redox coupling with polyiodides.
• Electrochemical performance testing in coin and pouch cells.

Main Results:

• Formation of insoluble ferrocenium-polyiodide complexes effectively suppressed shuttle effects.
• Achieved a discharge capacity of 160.5 mAh g_cathode^-1 and >99.5% Coulombic efficiency at 1 C.
• A 1.2 Ah pouch cell demonstrated 600 stable cycles at 0.5 C with 99.8% average Coulombic efficiency.

Conclusions:

• The electroactive redox coupling strategy successfully addresses shuttle effects and host-derived energy density limitations.
• Ferrocene incorporation provides a viable pathway for high-performance aqueous zinc-iodine batteries.
• This approach is promising for practical grid-scale energy storage applications.