Anchoring high-mass iodine to nanoporous carbon with large-volume micropores and rich pyridine-N sites for high-energy-density and long-life Zn-I2 aqueous battery

Aqueous Zn-I 2 batteries (AZIBs) are highly desirable for green energy-storage technologies, but their development was greatly limited by their unsatisfactory energy densities. Herein, we report high-energy-density rechargeable AZIBs achieved by anchoring high-mass iodine to a distinctive N-doped hierarchical porous carbon (NHPC) material with large micropore volume and rich N-doping. The NHPC combined strong iodine confinement caused by the micropore and powerful chemisorption of iodine species with pyridine-N doping, which enabled high loads of iodine up to 61.6 wt%. Notably, density functional theory calculations and experimental studies showed that abundant pyridine-N active sites promoted electron transfer, and the interconnected micro-mesoporous structure facilitated the Zn-ion diffusion to synergistically promote the redox kinetics of AZIBs. The high content of iodine-loading cathode exhibited a high capacity of 219.3 mA h g −1 at 1.0 C, indicating excellent rate capability and superior cycling stability with a low capacity decay of 0.00147% per cycle within 10,000 cycles at 5.0 C. In addition, a preliminary device assembled with three batteries in series provided a high energy density of up to 72.6 W h kg −1 calculated by the total mass of the battery, which is almost two times that of the commercial aqueous lead-acid and Ni-Cd batteries. The high energy density and long cycle life of this aqueous battery indicate its great application potential in large-scale energy storage.