Mesoporous dominated porous carbon with high nitrogen and phosphorus doping levels toward high area capacity zinc-iodine batteries

The synthesis of porous carbon materials as host materials to adsorb iodine solely through a high density of micropores is insufficient to meet the demands of high-performance aqueous zinc-iodine batteries (AZIBs). To address this limitation, we designed a nitrogen-phosphorus co-doped hierarchical porous carbon (NP-HPC) with mesopore dominance and high phosphorus doping levels (8.52 % nitrogen and 6.64 % phosphorus) using a sol carbonization strategy. Specifically, the abundant mesopores are conducive to promoting rapid mass transfer at the solid-liquid interface and enabling the electrolyte to reach the inaccessible micropore. The synergistic effect of special pore structure and high nitrogen and phosphorus doping levels in NP-HPC makes it a promising host to confine iodine tightly. Furthermore, the density functional theory calculations (DFT) results reveal that N, P codoping enhances nitrogen atom charge accumulation, improves carbon skeleton zinc adsorption capacity, and provides extra pseudo capacity for AZIB. Therefore, the optimized NP-HPC-assembled AZIBs exhibited an excellent discharge-specific capacity of 123.4 mAh g- 1 at 0.1 A g- 1 with a high iodine loading of 13.25 mg cm-2 and a capacity retention of 90 % after 1000 cycles at 1.0 A g- 1. This study not only presents insights into the design of porous carbon with high heteroatom doping level, but also proposes a novel approach for achieving high area-specific capacity AZIBs.