Confinement of iodine species into oxygen doped hierarchical porous carbon host for high loading zinc-iodine batteries

The aqueous zinc-iodine batteries (ZIBs) have been expected to be the most promising next-generation energy storage device. However, it is still struggling with the limited intrinsic electronic conductivity, poor thermal stability and high solubility of the discharge products. Additionally, the iodine loading is below 2 mg cm−2 in most of the reported aqueous ZIBs, impeding their widespread application. Herein, we present a one-step production method for O-doped hierarchical porous carbon framework (OHPCF) from biomass as an iodine host material to solve the problems mentioned above. Benefiting from synergistic physical confinement (high-density microporous structure) and chemical anchoring (abundant oxygen atom doping) effect of the OHPCF samples, the electrode exhibits low polarization, high iodine utilization and excellent electrochemical stability in ZIBs. Encouragingly, we achieve an ultra-high area capacity of 3.3 mAh cm−2 with a loading of 20.3 mg cm−2, demonstrating its superior application potential. This work introduces a simple yet effective strategy for developing 3D microporous electrodes for ZIBs with high iodine loading, enabling high areal capacity with remarkable rate and cycling performance.