A Robust Biopolymer Network Binder for High‐Loading Iodine Cathodes in Zinc‐Iodine Batteries

Abstract

ABSTRACT High energy density and long cycle life are critical for practical aqueous zinc‐iodine batteries (AZIBs). However, the development of high‐mass‐loading iodine cathodes faces bottlenecks, such as structural instability, severe polyiodide shuttling, and sluggish charge transfer kinetics. Herein, a robust biopolymer network (XGP) binder is developed, featuring a 3D network structure with dense hydrogen bonding that provides strong adhesion and good mechanical strength for high‐mass‐loading active carbon (AC)@I 2 cathodes. Using a scalable slurry‐drawing method, the obtained thick AC@I 2 electrodes exhibit a porous architecture with high porosity (47.6%), facilitating rapid Zn 2 + diffusion (up to 10 −9 cm 2 s −1 ) and fast electrochemical kinetics. Furthermore, diverse oxygen functional groups in the XGP binder provide strong chemical anchoring sites, effectively suppressing polyiodide shuttling. Consequently, XGP‐based cathodes with an ultrahigh iodine loading (82 mg cm −2 , ∼960 µm) achieve an areal capacity of 15.3 mAh cm −2 . Zn‐I 2 pouch cells deliver a capacity of 1744 mAh over 600 cycles, yielding a remarkable energy density of 55.0 Wh L −1 at the cell level. This work solves key challenges in thick iodine electrodes through integrated design of the biopolymer binder and electrode engineering, paving the way for practical AZIBs.