A Polyanionic Hydrogel Electrolyte with Ion Selective Permeability for Building Ultra‐Stable Zn/I₂ Batteries with 100 °C Wide Temperature Range

AbstractThe practical applications of aqueous Zn/I2 batteries (AZIBs) operating within a wide temperature range are severely hindered by the uncontrolled shutting of polyiodide ions (I3−/ I5−) and rampant side reactions. In this study, a wide temperature tolerant polyanionic hydrogel (borax‐bacteria cellulose / p(AMPS‐AM)) with ion selective permeability is designed for inhibiting shutting effect and side reactions under extreme temperatures range from −50 to 50 °C. The zincophilic R−SO3− significantly enhances the transport of Zn2+ cations and promotes uniform growth of Zn metal along the (002) plane. Moreover, the abundant hydrophilic groups in hydrogels effectively suppress both the hydrogen evolution reaction and the formation of by‐products by reducing the water reactivity. Furthermore, theoretical calculations, visualization experiment and in situ Raman spectroscopy confirm that R−SO3− group effectively hinders the shuttle process of I3−/I5− anions through electrostatic repulsion. Consequently, this gel electrolyte facilitates the ultra‐stable Zn/I2 full cell at a low current density of 2 C over a wide temperature range of 100 °C. A Zn/I2 pouch cell with a low negative/positive capacity ratio of 3.3 exhibits a stable performance over 350 cycles with an impressive high‐areal capacity of 2.03 mA h cm−2, thereby establishing a solid foundation for its practical applications.