Tailoring C₃N₄ Host to Enable a High-Loading Iodine Electrode for High Energy and Long Cycling Zn–Iodine Battery

The high-energy-density zinc–iodine batteries (ZIBs) are hindered by low iodine loading in the cathode, which limited the specific capacity and energy density at the total electrode level. The unstable adsorption by the conventional host materials of the iodine electrode exacerbates the severe iodine shuttling and sluggish reaction kinetics. Here, we developed Br-doped carbon nitride (BrCN) nanosheets by using a chemical exfoliation strategy and doping engineering to obtain efficient iodine host materials for the iodine electrode. It eventually enhanced the adsorption force between BrCN and the iodine species, effectively stabilizing the high-loading iodine electrode and suppressing the polyiodide shuttle. As a result, BrCN-based host achieves an iodine mass loading of 14.1 mg cm^–2 of 46 wt % mass loading ratio (up to a maximum loading of 23.5 mg cm^–2), which achieves a high specific capacity of 97.0 mAh g^–1 and the energy density of 116.4 Wh kg^–1 based on the total iodine electrode.