Pore-Engineered Carbon Cloth via Thermal Activation for Shuttle-Free Zinc-Iodine Batteries with Ultralow Self-Discharge.

Abstract

Zinc-iodine (Zn-I₂) batteries are promising for grid-scale energy storage but suffer from severe polyiodide shuttling and rapid self-discharge. Here, a thermally activated carbon cloth (CC450) that simultaneously addresses iodine confinement and reaction kinetics through precisely engineered hierarchical porosity is reported. By optimizing oxidative calcination at 450 °C in air, CC450 develops a unique pore structure with nanopores for strong I₃ ^- adsorption and interconnected macropores for rapid ion transport, while maintaining the intrinsic conductivity and flexibility of CC. The CC450 cathode achieves an exceptional balance of performance metrics: high areal capacity, ultralow self-discharge (3.05% in 24 h), and outstanding cycling stability (94.63% capacity retention over 1000 cycles), which represents the best-reported performance for binder-free carbon electrodes in Zn-I₂ batteries. Mechanistic studies reveal that CC450's 12-fold reduction in charge-transfer resistance and low activation energy for I^- oxidation stem from its optimal surface chemistry and pore hierarchy. The self-discharge tests and UV-vis spectroscopy confirm efficient iodine shuttle suppression. Unlike complex nanomaterial-based hosts, CC450 is fabricated through a scalable ambient-air process, offering immediate industrial relevance. This work provides critical insights into pore-engineered carbon hosts for metal-iodine batteries and establishes a generalizable strategy for achieving high-energy, long-life energy storage systems.