Polycation-regulated hydrogel electrolytes with nanoscale hydrophobic confinement inducing Zn(002) deposition for highly reversible zinc anodes†

Abstract

Aqueous zinc-ion batteries (AZIBs) are regarded as one of the most promising candidates for flexible energy storage applications. However, they suffer from notorious issues such as dendrite formation, corrosion and inferior coulombic efficiency (CE). Herein, a polycation-regulated, amphiphilic hydrogel electrolyte with remarkable mechanical toughness and impressive self-healing properties is introduced to improve the electrochemical performance of Zn anodes. The hydrogel electrolytes containing positively charged macromolecular chains effectively regulate the interfacial electric field, trap anionic SO₄²⁻, enhance Zn²⁺ migration kinetics, reduce the tip effect and guide the preferential growth of the Zn(002) plane. Besides, the presence of long hydrophobic alkyl chains in the amphiphilic hydrogel electrolyte facilitates the creation of a nanoscale H₂O-deficient environment at the interface and effectively confines the activity of free water. Consequently, an impressively high average CE of 99.8% for Zn//Cu cells with an ultralong lifespan of 4928 h is achieved. Additionally, the assembled Zn//Zn symmetric cells exhibit a long cycling lifespan of 2400 h at 2 mA cm⁻² and 840 h at 10 mA cm⁻². Even under high capacity and high depth of discharge (15 mA h cm⁻², 51%), the Zn//Zn cell still demonstrates stable reversibility. Considering the above properties, the assembled AZIBs perform better in terms of capacity, lifespan and prominent applications in harsh environments. This work provides a molecular strategy for polycation-regulated hydrogel electrolytes with hydrophobic confinement, allowing for oriented Zn(002) deposition and a comprehensive AZIB resistant to mechanical operations.