Bidirectional Confined Redox Catalysis Manipulated Quasi-Solid Iodine Conversion for Shuttle-Free Solid-State Zn-I₂...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Achieving reversible iodine speciation in metal-iodine batteries is crucial for practical applications.
• Existing metal-iodine batteries often suffer from issues related to polyiodide formation and inefficient redox conversion.

Purpose of the Study:

• To develop a polyiodide-free zinc-iodine (Zn-I2) battery with enhanced electrochemical performance.
• To demonstrate a novel cathode structure that facilitates controlled and reversible iodine conversion.
• To investigate the catalytic role of Prussian blue and polypyrrole in mediating the redox reactions.

Main Methods:

• Fabrication of a core-shell structured iodine cathode using multiporous Prussian blue nanocubes and a polypyrrole sheath.
• Utilizing a zincate (Znx+1FeIII/II[Fe(CN)6]y) redox mediator to catalyze polyiodide reduction during discharge.
• Employing the same mediator to catalyze polyiodide oxidation during recharge, enabling reversible ZnI2 to I2 conversion.

Main Results:

• The developed Zn-I2 battery operates without polyiodide formation, showcasing bidirectional confined redox catalysis.
• The core-shell cathode demonstrates efficient zinc-ion intercalation kinetics and overlapping kinetic voltage profiles.
• A flexible solid-state battery utilizing this cathode achieved a high energy density of 215 Wh kg-1 (iodine basis).

Conclusions:

• The demonstrated polyiodide-free Zn-I2 battery design offers a promising pathway for advanced energy storage solutions.
• The synergistic catalytic effect of Prussian blue and polypyrrole is key to the battery's reversible iodine conversion.
• This approach paves the way for high-performance, flexible solid-state metal-iodine batteries.