Stable Four‐Electron Zinc‐Iodine Battery Realized by Polyacrylamide as Catalytic Binder

Abstract Realizing stable four‐electron reactions () is the key to boosting the energy density of aqueous zinc‐iodine batteries (ZIBs). In most of the traditional studies, the four‐electron reactions are realized by catalytic halogen ions as electrolyte additives. Herein, we utilize commercial polyacrylamide (PAM) powder as a cost‐friendly electrode binder to catalyze the stable interconversion between I 0 and I + , enabling a four‐electron reaction in the absence of halogen ions. We show that PAM obtained from various suppliers can serve as a catalytic binder and induce the 4e reactions due to the presence of a large amount of nucleophilic −CONH 2 group, which strongly binds with I + . Furthermore, PAM also exhibits a strong affinity to polyiodide species, which suppresses the polyiodide shuttling and thus mitigates the anode side reactions between polyiodide and Zn. As a result of the above two beneficial effects, the Zn‐I 2 battery demonstrates a high capacity of 416 mAh g −1 (calculated from available iodine mass in electrolyte) and an extended cycle life of over 10 000 cycles at 5 A g −1 . This low‐cost and fluorine‐free commercial binder for four‐electron iodine reaction will boost the progress of high‐energy‐density aqueous Zn batteries.