Reprotonation Kinetics Engineering of Aramid Nanofiber Hydrogel Electrolytes for Aqueous Zinc-Ion Batteries

Abstract

Aqueous zinc-ion batteries are promising next-generation energy-storage systems owing to their intrinsic safety and cost-effectiveness. However, dendrite formation and parasitic reactions at Zn metal anodes limit long-term cycling stability. Here, aramid nanofiber (ANF) hydrogel electrolytes are engineered by controlling the acid identity and solution pH during reprotonation. These variables regulate reprotonation kinetics, thereby shaping hydrogen-bond formation, molecular ordering, and the through-thickness morphology of the ANF network. The selected ANF hydrogel electrolyte exhibits a Young’s modulus of 1.1 MPa while maintaining an ionic conductivity of 30.8 mS cm–1. Its mechanically robust and ionically conductive network promotes compact Zn deposition and resists dendrite penetration. Consequently, Zn||Zn symmetric cells sustain stable plating/stripping for over 2000 h at 1.0 mA cm–2 with an areal capacity of 1.0 mAh cm–2. Compared with conventional glass-fiber-based cells, Zn||hydrated vanadium oxide full cells also exhibit improved high-rate capacity retention and retain over 88% of their initial capacity after 2000 cycles at 1.0 A g–1. These findings establish reprotonation kinetics as a practical design parameter for balancing mechanical robustness, ion transport, and interfacial stability in hydrogel electrolytes for durable aqueous zinc-ion batteries.