Modulating an anion-enriched Zn2+ solvation structure via a dual weak interaction for stable zinc–metal batteries†

Abstract

Aqueous zinc-ion batteries exhibit significant potential for large-scale energy storage due to their high specific capacity, high safety and cost-effectiveness. However, the interfacial issues including severe side reactions, metal self-corrosion and dendrite growth result in a decline in overall battery performance and hinder their practical application. Herein, a hydrated electrolyte with a dual weakened Zn²⁺ solvation structure of [Zn(DMI)₃(OTf)₂(H₂O)] 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 (E_a), facilitating the rapid desolvation kinetics of Zn²⁺. Moreover, DMI can form new hydrogen bonds with H₂O and effectively reduce the activity of water. The anions and DMI within the solvation structure can induce the in situ formation of an organic/inorganic hybrid solid–electrolyte interphase layer on the Zn anode, significantly suppressing water-related side reactions and inhibiting Zn dendrite growth. Ultimately, a Zn//Cu asymmetric cell achieves a high average coulombic efficiency of 99.72%, and a Zn//Zn symmetric cell with the 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, a Zn//PANI full battery exhibits ∼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.