Binary Electrolyte Additive-Reinforced Interfacial Molecule Adsorption Layer for Ultra-Stable Zinc Metal Anodes

Abstract

Aqueous zinc ion batteries (AZIBs) face challenges due to the limited interface stability of Zn anode, which includes uncontrolled hydrogen evolution reaction (HER) and excessive dendrite growth. In this study, a natural binary additive composed of saponin and anisaldehyde is introduced to create a stable interfacial adsorption layer for Zn protection via reshaping the electric double layer (EDL) structure. Saponin with rich hydroxyl and carboxyl groups serves as “anchor points”, promoting the adsorption of anisaldehyde through intermolecular hydrogen bonding. Meanwhile, anisaldehyde, with a unique aldehyde group, enhances HER suppression by preferentially facilitating electrocatalytic coupling with H^* in the EDL, leading to the formation of a robust inorganic solid electrolyte interphase that prevents dendrite formation, and structural evolution of anisaldehyde during Zn deposition process is verified. As a result, the Zn||Zn symmetric cells present an ultra-long cycling lifespan of 3 400 h at 1 mA cm⁻² and 1 700 h at 10 mA cm⁻². Even at the current density of 20 mA cm⁻², the cells demonstrate reversible operations for 450 h. Furthermore, Zn-ion hybrid capacitors exhibit a remarkable lifespan of 100 000 cycles. This work presents a simple synergetic strategy to enhance anode/electrolyte interfacial stability, highlighting its potential for Zn anode protection in high-performance AZIBs.