Zwitterionic hydrogels with high interfacial affinity for zinc metal batteries

Zinc metal batteries are expected to be the next generation of energy storage devices due to their high safety, but their application is hampered by irreversible hydrogen evolution reaction and surface side reactions of zinc anodes. Here, a zwitterionic hydrogel electrolyte is reported based on polymerization of acrylamide and 1-(3-Sulfopropyl)-2-Vinylpyridinium betaine, and it exhibits the following advantages: the sulfonic acid group of 1-(3-Sulfopropyl)-2-Vinylpyridinium betaine can be preferentially adsorbed on metal Zinc to avoid side reactions and refine the affinity at the zinc-electrolyte interface; and the coordination of the negatively charged sulfonic acid group with Zn 2+ alters the solvation structure of Zn 2+ , which further improves the restriction ability of side reactions. Consequently, Zn||Zn symmetric batteries can be stabilized for 1, 200 h of plating stripping at 1 mA cm −2 . Zn||Cu batteries exhibit an impressive average coulombic efficiency of 99.8 % over a remarkable span of 1, 800 cycles at a current density of 15 mA cm −2 . Furthermore, the Zn||MnO 2 /Carbon nanotube batteries have been cycled more than 2, 000 cycles at a current density of 0.5 A g −1 , and the zinc hybrid capacitors for more than 18, 000 cycles at 1 A g −1 . And an ionic skin (i-skin) based on acrylamide and 1-(3-Sulfopropyl)-2-Vinylpyridinium betaine of polymer hydrogel electrolyte is assembled and it can stably detect physiological signals.