Carboxymethyl Chitosan‐Modified Zinc Anode for High‐Performance Zinc–Iodine Battery with Narrow Operating Voltage

Reasonable regulation of iodine redox has gradually shown potential as a desirable cathodic reaction in zinc‐based batteries, but suffers from poor cyclic reversibility caused by uncontrollable side reactions. Also, the irregular growth of dendrites and unavoidable occurrences of hydrogen evolution reaction in H 2 O‐rich environment have become permanent topics in anodic zinc. Herein, a cross‐linked gel based on carboxymethyl chitosan is proposed and serves as an artificial electrolyte interphase for zinc anode (marked as Zn‐CMCS). Such a coating formed by crosslinking among a monodentate carboxyl group, a hydroxyl, an amino, and Zn 2+ from adding solution closely adheres on the surface of the zinc foil with toughness, ductility, and ideal electrochemical kinetics. Additionally, its homogenized surface charge distribution provides a “flexible” substrate for zinc plating/stripping, resulting in a flat real‐time interface. While introducing I − /I 0 conversion by matching adsorptive activated carbon on carbon fiber cloth (AC‐CFC) as cathode, the internal space restricted by CMCS gel enables the assembled Zn‐CMCS/AC‐CFC battery to exhibit a greatly improved reversibility under long‐cycling condition within 28 000 cycles (measured for more than 2 years) in a narrow operating voltage range of 0.23 V.