A biphasic hydrogel electrolyte with multi-scale stress deconcentration and dual-field regulation for highly reversible aqueous Zn ion batteries

Aqueous zinc ion batteries (AZIBs) utilizing hydrogel electrolytes have emerged as promising sustainable solutions for flexible energy storages owing to their intrinsic safety and mechanical stability. However, the inherent poor toughness, low Zn 2+ transference number, and lacking electron field regulation capability in conventional hydrogel electrolytes exacerbate uncontrolled Zn dendrite growth and side reactions, posing a substantial challenge to interfacial stability between the Zn anode and the hydrogel electrolyte. To address this, here we present a novel biphasic hydrogel electrolyte capable of both multi-scale stress deconcentration and dual-field regulation via polymerization followed by salting-out and coordination strategy. The well-designed hydrogel electrolyte demonstrates high toughness of 17.5 kJ m −2 , an ionic conductivity of 60.6 mS cm −1 and a Zn 2+ transference number of 0.753, collectively achieving highly reversible Zn plating/stripping and exceptional interfacial stability. Consequently, the Zn||NaV 3 O 8 ·1.5H 2 O (NVO) full cells equipped with this hydrogel electrolyte show remarkable electrochemical performance, including high capacity (375.4 mAh g −1 at 0.5 A g −1 ), outstanding rate capability (188.9 mAh g −1 at 8 A g −1 ) and long-term cycling stability (91.6 % capacity retention after 3000 cycles), with sustained performance under harsh conditions such as high temperature, high humidity, and low temperatures (−30 °C). Furthermore, the assembled flexible pouch cells demonstrate exceptional mechanical and environmental adaptability, reliably powering a circular lamp even under severe bending at both room and −30 °C. This work provides fundamental insights into Zn anodic chemistry in multifunctional hydrogel electrolyte and offers practical guidelines for constructing advanced zinc-based energy storage devices.