Fluorine-doped 3D honeycomb carbon network for long-duration aqueous zinc–iodine batteries

Aqueous zinc-iodine batteries (AZIBs) offer inherent safety and low cost for future energy storage. However, their energy density is severely limited by the lack of host materials capable of suppressing polyiodide shuttling and ensuring efficient redox kinetics under high iodine loading. Hence, we developed a fluorine-doped three-dimensional honeycomb-like carbon nanonetwork (F-Cnet) as an efficient iodine host. The material synergizes a hierarchical porous framework for physical confinement with fluorine-induced surface polarity and catalytic sites, which collectively enhance iodine adsorption, accelerate conversion kinetics, and improve structural stability. This design enables an I₂@F-Cnet cathode to achieve a high areal capacity of 5 mAh cm^-2 (iodine loading: 23.5 mg cm^-2) and exhibit exceptional stability, retaining 87.6% capacity after 1200 cycles at an ultrahigh current density of 100 mA cm^-2 with a specific electrode energy density of 110.1 Wh kg^-1. Moreover, the battery maintains long-duration operation for over 3200 hours (250 cycles) at 0.04 A g^-2 (12 h per cycle) with 88.7% capacity retention.