From Screening to Site Control: Phytic-Acid Mediated P-Tuning of M–N Coordination to Balance Iodine Adsorption and Stability in Zn–I2 Batteries

Aqueous zinc-iodine batteries (AZIBs) show promise for grid-scale energy storage, but they are hampered by polyiodide shuttling, sluggish iodine redox kinetics, and irreversible active-site poisoning caused by uncontrolled adsorption. We provide a comprehensive screening of M 1 (M 1  = P, S, B) heteroatom dopants, and P is identified as the best candidate for achieving coordination-tuned, moderate adsorption that balances adsorption and catalytic activity while mitigating site poisoning. Using phytic acid as both the P source and an etchant, we create a universal in situ approach to core–shell single-atom catalysts (M 2 -P-CSNC, M 2  = Fe, Co, Ni). The unique core–shell structure achieves stable confinement of polyiodides, rapid ion transport, and protection of active sites, while in situ P doping precisely regulates the local electronic environment and d -band center of the Fe–N x active centers. In situ characterization confirms that Fe–P-CSNC has a strong reversible anchoring ability for polyiodides, which can significantly accelerate redox kinetics. The optimized Fe–P-CSNC/I 2 exhibits almost no capacity decay after 20,000 cycles at a current density of 2 A g −1 . This work’s facile heteroatom doping strategy for electronic modulation offers a reference for high-performance catalyst design in conversion-type energy storage systems. Kindly check and confirm the edit made in the title.1. We have checked and confirmed the edited title.2. We found some issues with Figure 3d and have uploaded the revised image as an attachment.