Ionic Selective Separator Design Enables Long-Life Zinc-Iodine Batteries via Synergistic Anode Stabilization and Polyiodide Shuttle Suppression

Aqueous zinc-iodine batteries show immense potential in the electrochemical energy storage field due to their intrinsic safety and cost-effectiveness. However, the rampant dendritic growth and continuous side reactions on the zinc anode, coupled with the shuttling phenomenon of polyiodides, severely affect their cyclic life. In response, this study utilizes a carboxyl-functionalized metal-organic framework UiO-66-(COOH)2 (UC) to modify commercial glass fiber (GF) to develop a novel ionic selective separator (UC/GF). This separator exhibits cation exchange ability for Zn2+ and polyiodides, thereby simultaneously stabilizing the zinc anode and inhibiting the shuttle effect of polyiodides. Enhanced by the abundant polar carboxyl groups, the UC/GF separator can effectively facilitate Zn2+ ion transport and accelerate the desolvation of hydrated zinc ions by its zincophilicity and hydrophilicity, while significantly hindering the transfer of polyiodides via electrostatic repulsion. Consequently, the Zn|UC/GF|Zn symmetric battery enables a long lifespan of over 3400 h at a current density of 5.0 mA cm-2, while the Zn|UC/GF|I2 exhibits an exceptional discharge capacity of 103.8 mAh g-1 after 35 000 cycles at 10 C with a capacity decay rate of only 0.0013% per cycle. This separator modification strategy that synergistically optimizes anode and cathode performance provides unique insights into the commercialization of zinc-iodine batteries. An ionic selective separator is prepared to achieve long-lifespan zinc-iodine batteries. This separator can stabilize the zinc anode and suppress the shuttle effect of polyiodides simultaneously. Consequently, the symmetric battery enables a long lifespan of over 3400 h, while the full battery exhibits remarkable cycle stability of over 35 000 cycles. image