An Ultrahigh-Modulus Hydrogel Electrolyte for Dendrite-Free Zinc Ion Batteries.

Quasi-solid-state aqueous zinc ion batteries suffer from anodic zinc dendrite growth during plating/stripping processes, impeding their commercial application. The inhibition of zinc dendrites by high-modulus electrolytes has been proven to be effective. However, hydrogel electrolytes are difficult to achieve high modulus owing to their inherent high water contents. This work reports a hydrogel electrolyte with ultrahigh modulus that can overcome the growth stress of zinc dendrites through mechanical suppression effect. By combining wet-annealing, solvent-exchange, and salting-out processes and tuning the hydrophobic and crystalline domains, a hydrogel electrolyte is obtained with substantial water content (≈70%), high modulus (198.5 MPa), high toughness (274.3 MJ m^-3), and high zinc-ion conductivity (28.9 mS cm^-1), which significantly outperforms the previously reported poly(vinyl alcohol)-based hydrogels. As a result, the hydrogel electrolyte exhibits excellent dendrite-suppression effect and achieves stable performance in Zn||Zn symmetric batteries (1800 h of cycle life at 1 mA cm^-2). Moreover, the Zn||V₂O₅ pouch batteries display excellent cycling life and operate stably even under extreme conditions, such as large bending angle (180°) and automotive crushing. This work provides a promising approach for designing mechanically reliable hydrogel electrolytes for advanced aqueous zinc ion batteries.