Cation and anion co-modulated electrolytes enable highly textured and reversible zinc anodes for durable aqueous batteries

Abstract

Dendrite formation and side reactions, which originate from uncontrolled zinc (Zn) nucleation and growth and high water activity, remain the two critical challenges that hinder the practical implementation of Zn anodes for rechargeable aqueous batteries. In this work, we propose a cation and anion co-modulation strategy to realize highly textured and durable Zn anodes. As a proof of concept, 1-ethyl-1-methylpyrrolidinium bromide (MEPBr) is selected as a versatile additive to regulate Zn deposition. Specifically, MEP+ cations with preferential adsorption on tips/edges first promote uniform primary Zn nucleation on the substrate, followed by dynamic “edge shielding” of existing deposits to guide highly oriented Zn growth. Meanwhile, the incorporation of Br− anions promotes the enrichment of Zn2+ at the electrode–electrolyte interface (EEI), thereby facilitating Zn deposition kinetics. In addition, both the preferentially adsorbed MEP+ cations and Br− anions create a water-poor EEI while the two ionic species disrupt the original hydrogen bond network and reduce water within the solvation structure in the bulk electrolyte through ion-water interactions, thus dramatically reducing water-induced side reactions. As a result, the Zn//Zn symmetric battery with the MEPBr-modulated electrolyte exhibits a remarkable lifespan of over 4000 h at 2 mA cm−2 and 1 mA h cm−2. More excitingly, the newly designed electrolyte enables a Zn//NaV3O8·1.5H2O full battery with a thin Zn anode (50 μm) and a high mass-loading cathode (∼10 mg cm−2) to operate normally for over 300 cycles with remarkable capacity retention, showcasing its great potential for practical applications.