Integrated Thick Flexible Iodine Electrode with Polyiodide Immobilization Hydrogelation Interphase for Practical...

Aqueous zinc-iodine batteries are promising candidates for grid-scale energy storage, but their practical application is hindered by low areal-capacity and shuttling of polar polyiodides on positive-electrode side. Herein, a high-areal-capacity iodine electrode (up to 14 mAh cm^-2) with mechanical flexibility is developed through an integrated thick electrode processing technology, which synergistically combines enhanced ion transport with a polyiodide-immobilization hydrogelation interphase. A viscoelastic polyamide thermoplastic elastomer network is in situ formed throughout electrode bulk via a rapid phase inversion method, acting as structural skeleton to preserve transient slurry-level uniformity, concurrently ensuring interconnected ion transport network and mechanical robustness even under high thickness (>2 mm). Moreover, the polyamide interphase, rich in functional amide groups, demonstrates strong binding affinity for polyiodides, effectively immobilizing them within the hydrogelation layer and facilitating their reutilization during redox cycling. Consequently, the high-loading flexible electrode (70 mg cm^-2) delivers an average areal-capacity of 11.5 mAh cm^-2 at 0.62 A g^-1 with over 1600 cycles. Notably, the integrated electrode can be directly used to assemble Ah-level single-layer pouch cells (~1.6 Ah), demonstrating stable operation over 1200 cycles and validating practical applications in powering wearable electronics and high-power devices, thereby paving the way toward high-energy-density zinc-iodine batteries.