Interfacial modulation via cationic electrostatic shielding effect for reversible and durable Zn anodes in hydrogel electrolytes

Although metallic Zn has been considered as a promising anode material in aqueous energy storage systems owing to its high theoretical capacity and intrinsic security, its practical applications are limited by dendrite growth and side reactions at the interface. To address these challenges, here we propose a cationic electrostatic shieling strategy by incorporating choline (Ch+) cations in hydrogel electrolyte (denoted as gel-ChCl electrolyte) to optimize the electrolyte-electrode interface. Theoretical and experimental findings reveal that the Ch+ cations preferentially adsorb on the Zn surface to create an electrostatic shielding layer, which functions dual effects, i.e., redistributing interfacial Zn2+ ions for the uniform deposition and fabricating water-poor interface for the inhibited side reactions. With this strategy, dendrite-free Zn anodes with high plating/stripping reversibility are realized in Zn//Zn and Zn//Cu cells for long-term lifespan and high average coulombic efficiency, respectively. More impressively, the Zn-ion hybrid capacitors (ZHCs) optimized by the gel-ChCl electrolyte deliver favorable flexibility, excellent cyclability (82.6% capacity retention after 40,000 cycles), and energy-storage applications. This work proposes a facile cationic electrostatic shielding strategy to modulate the electrolyte-electrode interface for reaching dendrite-free Zn anodes, which is favorable for advanced flexible ZHCs and beyond.