Nano-carbon Supported B/N-coordinated Fe Single Atoms with Tuned Electronic Structure for Long Lifespan Zinc-iodine Batteries

Abstract

Single-atom catalysts (SACs) have great potential to boost the sluggish iodine redox kinetics and alleviate polyiodides shuttle in aqueous zinc-iodine (Zn-I2) batteries. Nevertheless, it is a big challenge to improve the catalytic activity of traditional metal nitrogen (M-N4) SACs by adjusting the microenvironment to enhance iodine redox kinetics. Herein, asymmetric B/N-coordinated Fe single atoms (Fe-B2N2) immobilized on carbon nanotube forests (denoted as Fe-SAs@BNCF) are prepared by one-pot calcination method and used as the iodine host in Zn-I2 batteries. Theoretical calculation results have revealed that the B sites function to increase the electron density by disrupting the symmetrical electron distribution around the Fe sites compared to traditional Fe-N4. Correspondingly, the as-synthesized Fe-B2N2 SACs significantly improve the polyiodide adsorption and electrocatalytic activities in Zn-I2 batteries. Moreover, carbon nanotube forests provide more adsorption sites for polyiodides. Consequently, the Zn-I2 batteries with Fe-SAs@BNCF as host enable superb long lifespan (78% retention over 60,000 cycles at 5 A g−1) and capable rate ability (147 mAh g−1 at 10 A g−1). This work provides a promising strategy for designing advanced I2 cathodes with asymmetric single atoms for long-life Zn-I2 batteries.