Improving diffusion kinetics of zinc ions/stabilizing zinc anode by molecular slip mechanism and anchoring effect in supramolecular zwitterionic hydrogels.

The severe hydrogen evolution reaction and parasitic side reaction on Zn anode are the key issues which hinder the development of aqueous Zn-based energy storage devices. Herein, a polyacrylamide/carboxylated cellulose nanofibers/betaine citrate supramolecular zwitterionic hydrogels with molecular slip effects are proposed for enhancing Zn diffusion and protecting Zn anodes. Non-covalent interactions within supramolecular hydrogels forms the skeleton for molecular slip and the strong coordination of carboxyl and amino groups with Zn further facilitates the rapid Zn transfer. Additionally, anchoring carboxyl and amino groups at the anode promotes the uniform deposition of Znand protects Zn anode. On the basis of molecular slip mechanism and anchoring effect in the supramolecular zwitterionic hydrogels, Zn||Zn symmetric batteries undergo 800 h of stable electroplating stripping at a depth of discharge of 80 %. Zn||Cu asymmetric batteries exhibit an impressive average coulombic efficiency of 99.4 % over a remarkable span of 900 cycles at a current density of 15 mA cm. Furthermore, Zn||NHVO batteries successfully undergo over 1,000 cycles at a current density of 0.5 A g. Intrinsic ion diffusion mechanism of supramolecular hydrogel electrolytes provides an original strategy for the application of high-performance Zn-based energy storage devices.