Polymerized Melamine Catalyzes Direct I^-/I₂ Conversion via ─N═N─ Motif for HighCapacity Zn-I₂ Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Low iodine conversion efficiency and polyiodide shuttling limit the performance of traditional zinc-iodine batteries.
• Developing stable and efficient cathodes is crucial for advancing high-capacity battery technologies.

Purpose of the Study:

• To develop a high-performance catalytic organic cathode for zinc-iodine batteries.
• To address the challenges of low iodine conversion efficiency and polyiodide shuttling.

Main Methods:

• In situ polymerization of melamine on activated carbon to create a pMA@AC cathode.
• Electrochemical characterization, including capacity and cycling tests.
• In/ex situ characterization techniques and theoretical calculations to understand catalytic mechanisms.

Main Results:

• The pMA@AC cathode achieved a high capacity of 1.6 mAh cm⁻² and over 20,000 cycles.
• Demonstrated stable pouch cell performance with 440 mAh and 183 Wh kg⁻¹ after 100 cycles.
• Polymelamine catalyzed efficient I⁻/I₂ conversion, suppressing polyiodide shuttling and enhancing Coulombic efficiency.

Conclusions:

• The developed pMA@AC cathode offers a promising solution for high-capacity and long-lifespan zinc-iodine batteries.
• The unique catalytic properties of polymelamine, attributed to its π electron cloud and triazine groups, are key to its performance.
• This work highlights the potential of azo compounds in advanced zinc-halogen batteries.