Rechargeable aqueous Zn–I₂ batteries face challenges from zinc anode degradation (dendrites, corrosion) and polyiodide (I₃⁻/I₅⁻) shuttling at the cathode, limiting cycle life. To address these issues simultaneously, a novel ion-selective, solvation-regulating, and flexible sulfonic acid-based water reducer gel electrolyte (polyacrylamide (PAM)-polynaphthalene sulphonate (FDN)-carboxylated chitosan (CCS)/zinc sulfate (ZSO)) is designed in this work. This electrolyte features a three-dimensional (3D) porous structure and abundant polar groups enabling efficient Zn²⁺ transport and solvation structure regulation, promoting uniform zinc deposition and suppressing water-related side reactions (e.g., hydrogen evolution) at the anode. Crucially, the strongly negatively charged sulfonic acid groups impart exceptional ion selectivity: They electrostatically repel polyiodide anion, effectively blocking their shuttle to the anode and minimizing active iodine loss, while permitting unimpeded Zn²⁺ diffusion. Consequently, Zn–I₂ full cells employing this multifunctional gel electrolyte achieve outstanding cycling stability, retaining 118.5 mAh·g⁻¹ after 9000 cycles at 5 A·g⁻¹. This work achieves the synergistic optimization of interface issues in Zn–I₂ batteries by constructing an ion-selective multifunctional gel electrolyte, significantly enhancing their overall electrochemical performance.

Aqueous zinc-ion batteries (AZIBs) are regarded as one of the most promising rivals in the upcoming high-energy secondary battery market because of their safety and non-toxicity. However, the zinc dendrites growth and hydrogen evolution corrosion of the Zn anode have seriously restricted the application of AZIBs. Herein, to overcome these constraints, a three-dimensional (3D) porous PFA-COOH-CNT artificial solid electrolyte interface (SEI) film with high hydrophobic and zincophilic properties was constructed on Zn anode surface by in-situ polymerization of furfuryl alcohol (FA) and carboxyl carbon nanotubes (COOH-CNT). A series of in-situ, ex-situ characterizations as well as the density functional theory (DFT) calculations reveal that the formed PFA-COOH-CNT SEI film with an abundant oxygen-containing group can provide abundant zincophilic sites and induce homogeneous deposition of Zn²⁺, as well as the hydrophobic alkyl and carbon skeleton in PFA-COOH-CNT SEI film can isolate the direct contact of H₂O with Zn anode, and inhibit the occurrence of hydrogen evolution reaction (HER). Accordingly, the Zn anode with PFA-COOH-CNT layer can attain an ultra-long cycle life of 2200 h at 1 mA·cm⁻², 1 mAh·cm⁻². Simultaneously, the assembled PFA-COOH-CNT@Zn||V₂O₅ full cell can also achieve a high reversible capacity of up to 150.2 mAh·g⁻¹ at 1 A·g⁻¹ after 400 cycles, with a high average coulombic efficiency (CE) of 98.8 %. The designed PFA-COOH-CNT artificial SEI film provides a broad prospect for highly stable zinc anode, and can also be extended to other energy storage systems based on metal anodes.