Modulating Anion-Enriched Zn2+ Solvation Structure via Dual-Weak-Interaction for Stable Zinc-Metal Batteries

Abstract

Aqueous zinc-ion battery (AZIB) exhibits significant potential for large-scale energy storage due to their high specific capacity, high safety and cost-effectiveness. However, the interficial issues including severe side reactions, metal self-corrosion and dendrite growth, result in the decline in overall battery performance and hinder the practical application. Herein, a hydrated electrolyte with a weakened Zn2+ solvation structure of [Zn(DMI)3(OTf)2(H2O)] composed of salt anion, water, and 1,3-dimethyl-2-imidazolidinone (DMI) is reported to stabilize the Zn anode. The presence of a small amount of water in this electrolyte enhances ionic conductivity and lowers the activation energy (Ea), facilitating the rapid desolvation kinetic of Zn2+, and DMI can form new hydrogen bonds with H2O, effectively reducing the activity of water. The anions and DMI within the solvation structure can induce the in-situ formation of organic/inorganic hybrid solid-electrolyte interphase (SEI) layer on the Zn anode, significantly suppressing water-related side reactions and inhibiting Zn dendrite growth. Ultimately, the Zn//Cu asymmetric cell achieves a high average Coulombic efficiency of 99.72%, and the Zn//Zn symmetric cell with optimized electrolyte demonstrates a stable cycling life exceeding 4500 h at 1 mA cm⁻2 and 0.5 mAh cm⁻2, exhibiting highly reversible Zn plating/stripping. Meanwhile, the Zn//PANI full battery exhibited ~100% capacity retention for 2700 cycles at a current density of 1 A g−1, significantly outperforming Zn(OTf)2 aqueous electrolytes. This work provides a novel strategy for optimizing interfacial chemistry by designing weakly coordinating-intervention Zn2+ solvation structures within the electrolyte.