Engineering Anion-Diluent Matrix for Ion-Decoupled Localized High-Concentration Electrolytes toward Highly Stable Aqueous Zinc Ion Batteries

Abstract

Aqueous zinc-ion batteries suffer from electrolyte-induced degradation despite their inherent safety advantages. While localized high-concentration electrolytes (LHCEs) mitigate interfacial instability, the excessive cation–anion association elevate ionic transport barriers, resulting in sluggish migration kinetics. Herein, ion-decoupled LHCE (ID-LHCE) are proposed using amphiphilic 2,2,3,3-tetrafluoro-1-propanol (TFP) as anion-affinity diluent. The TFP-mediated anion-diluent matrix (ADM) liberates anion OTF⁻ from Zn²⁺ solvation sheaths, which maintains Zn²⁺-enriched nanodomains while significantly reducing ionic transport barriers with an elevated Zn²⁺ transference number of 0.72. ADM decouples aqueous networks into biphasic H₂O-rich/poor nanodomains, establishing a localized environment with attenuated water activity that suppresses hydrogen evolution reaction. Concurrently generated water-deficient interfaces and dehydrated OTF⁻ coordination environment synergistically facilitate the construction of dense gradient heterogeneous SEI: an inner ZnF₂-ZnS inorganic layer and an outer oligomer layer, enabling dendrite-free zinc deposition with ultralong cyclability (3,000 h at 1 mA cm⁻²) and 99.88% coulombic efficiency. Full cells paired with NaV₃O₈·1.5H₂O cathodes retain 72.5% capacity retention after 2,000 cycles at 0.5 A g⁻¹. Practical viability is demonstrated by the stable operation of high mass loading ampere-hour-level pouch cells (1.04 Ah). By correlating molecular interactions, nanoscale phase separation, and macroscopic ion migration, this work establishes a multiscale design paradigm for electrolyte nanostructure.