Constructing a Flexible-Rigid Integrated Network within Hydrogel Electrolyte to Achieve High-Stability Zinc-Iodine Batteries

Abstract Aqueous Zn||I2 batteries combine intrinsic safety and affordability, positioning them as strong contenders for large-scale energy storage, yet their practical use is hampered by uncontrolled zinc dendrites on the negative electrode and the polyiodide shuttling from the positive electrode. To resolve both challenges at once, an organic−inorganic hybrid hydrogel electrolyte with a flexible-rigid integrated network is rationally designed. This hydrogel electrolyte is constructed by introducing silane into a polysaccharide matrix, forming a covalently crosslinked Si−O−Si/Si−O−C hybrid framework with zincophilic and negatively charged characteristic. Owing to the cooperative contribution of the rigid siloxane framework and the flexible polysaccharide matrix, the composite hydrogel electrolyte achieves superior mechanical robustness, featuring a fracture stress of 2.58 MPa and an elastic modulus of 242.3 MPa, together with fast ion conduction (28.2 mS cm−1) and Zn2+-dominated ion-transport pathways. The hybrid framework also effectively modulates Zn2+ solvation sheath, facilitates interfacial ion transfer, promotes lateral zinc deposition, inhibits hydrogen evolution, and significantly retards polyiodide migration. Consequently, the zinc symmetric cell sustains steady-state operation over 1000 h (10 mA cm−2, 5 mAh cm−2). After undergoing 32,000 cycles, the full Zn‖I2 battery preserves 83.3% of the original capacity. Moreover, flexible Zn‖I2 pouch cells integrated with the composite hydrogel electrolyte display reliable behaviors when subjected to various mechanical distortions. Even under scenarios of ultra-high iodine loading and elevated anode utilization efficiency, the pouch cells still retain superior cyclability. This research proposes an efficient and scalable approach for the deliberate engineering of advanced zinc-based batteries.