Sulfonate-functionalization in Zn-iodine batteries as one stone kills two birds: iodine limiter and uniform Zn plating guidance layer

Aqueous Zn-iodine (Zn-I₂) batteries have attracted extensive research interest as an emerging redox conversion energy storage system due to the low cost and high safety. However, the shuttling effects of polyiodides arising from incomplete redox conversion and inhomogeneous Zn plating on the Zn anode surface always hinder the commercial application of Zn-I₂ batteries. In this work, a two-birds-with-one-stone strategy is reported for long-life Zn-I₂ batteries. Based on the strategy, the sulfonate-functionalized carbon fiber not only acts as the excellent iodine limiter to inhibit iodine species shuttling, but also as the uniform Zn plating guidance layer on the Zn anode surface to prevent the inhomogeneous deposition of Zn²⁺. Consequently, a superior cycling stability (a capacity of 124 mAh g⁻¹ after 10,000 cycles at 5 A g⁻¹) is achieved. Theoretical calculations illustrate that sulfonate groups successfully induce charge redistribution on the carbon substrate, thereby strengthening the electronic interactions of the iodine species with the carbon substrate. The charge-enriched sulfonate groups can guide the uniform deposition of Zn²⁺ through a strong Coulombic effect with Zn²⁺. This work gives a new perspective on the integrated design of cathodes and anodes for rechargeable batteries.