Enabling high-performance Zn-I ₂ batteries with a solvation-regulating, ion-selective, and flexible sulfonic acid-water reducer gel electrolyte

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 an ion-selective, solvation-regulating, and flexible sulfonic acid-based water reducer gel electrolyte (PAM-FDN-CCS/ZSO) is designed in this work. This electrolyte features a 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 9,000 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.