Engineering Electron Cloud Density to Achieve Bifunctional Electrophilic Hosts for Aqueous Zn-I2 Batteries with Ultrahigh Rate Property and Cycling Stability

For I 2 cathodes, the severe polyiodide shuttling and sluggish reaction kinetics result in unsatisfactory cycling lifespan and rate performance. Herein, a bifunctional electrophilic host is designed by engineering the electron cloud density to effectively anchor electron-rich polyiodides. Three configurations are initially screened through density functional theory simulations, which reveal that Si─O bonds can firmly anchor I 3 − via Si electrophilic centers. Owing to the considerably lower electronegativity of Si (1.90) than that of O (3.44), electrons surrounding Si atoms are strongly drawn toward O atoms, creating Si electrophilic centers. Specifically, I 3 − adsorbed onto Si─O bonds exhibits a favorable orbital configuration with a low energy gap, thereby kinetically enhancing polyiodide conversion. As a proof of concept, SiO 2 nanocrystals embedded in conductive microporous bio-carbon are derived from poplar flowers. The resulting I 2 cathodes demonstrate excellent cycling stability over 110 000 cycles at 4 A g −1 and a high rate performance with a capacity of 123.8 mAh g −1 at 100 C. Furthermore, the I 2 cathode with a loading as high as 36.5 mg cm −2 can also perform well in terms of 127.6 mAh g −1 after 100 cycles. This study presents a new route for the rational design of high-efficiency and sustainable hosts for I 2 cathodes.