Revitalizing Saturated ZnSO4 Electrolyte via Hydrogen-Bond Mediated Anionic Engineering for Durable Aqueous Zinc Metal Batteries

Abstract

Aqueous zinc metal batteries (AZMBs) based on ZnSO4 electrolytes are cost-effective and environmentally friendly, yet plagued by severe dendrite growth and side reactions. While increasing zinc salt concentration generally improves anode reversibility, this approach is hardly applicable to ZnSO4 due to its intrinsic solubility limit (~3.5 m in water), which prevents further optimization of key electrolyte properties for saturated ZnSO4 electrolytes. Here, we report a hydrogen-bond-mediated anionic engineering strategy to revitalize saturated ZnSO4 electrolyte by zinc amidosulfate. The exceptional co-solubility of zinc amidosulfate arises from the anion functioning as a molecular “hydrogen-bond wedge”. The dual-functional groups (−SO3⁻ and −NH2) synergistically interact with the water network, thereby disrupting the original solvation structure and regulating the interfacial electrochemistry at the zinc anode. This tailored electrolyte (3.5 m ZnSO4 with 0.5 m zinc amidosulfate) facilitated highly reversible Zn plating/stripping, enabling exceptional long-term cycling stability in both symmetric Zn||Zn cells (>3300 h at 10 mA cm−2) and Zn||CaV6O16·2.7H2O full cells (> 4500 cycles at 0.5 A g−1). This strategy successfully overcomes the solubility limit of conventional electrolytes and concurrently paves the way for durable AZMBs.