Anti‐Corrosive Covalent Iodo‐Thiadiazole Catalyst Enables Aqueous Zn─S Batteries with High Coulombic Efficiency

Aqueous zinc-sulfur batteries (AZSBs) hold great promise for large-scale energy storage but suffer from low Coulombic efficiency (CE) due to sluggish Zn─S redox kinetics and severe Zn anode corrosion, limiting their cycling life and practical applicability. Although state-of-the-art iodine-based redox mediators can accelerate cathode kinetics, they typically result in the formation of free I₃ ^- species, which exacerbate Zn corrosion. Here, we report a covalent iodo-thiadiazole redox mediator (CIM) as an anti-corrosive and highly efficient catalyst to achieve high CE in AZSBs. The covalently anchored iodine in CIM effectively suppresses free I₃ ^- formation and mitigates Zn corrosion. More importantly, dynamic electronic restructuring from C5═N to C5─N bonds (C5: 5th-position carbon in the thiadiazole ring) promotes Zn-S redox kinetics through a σ-coordination electron pathway facilitated by the Zn─I─C5 bond. As a result, CIM-based coin cells achieve an average CE of 99.56% and a capacity of 344 mAh g^-1 after 700 cycles at 8 C. The CIM-based pouch cell demonstrates a high capacity of 1398 mAh g^-1 after 120 cycles at 0.8 C. This work presents a practical design strategy for iodine-based catalysts, enabling next-generation aqueous metal-sulfur batteries with enhanced durability and performance.