Biodegradable Starch/Gelatin/PAM Hydrogel Electrolyte for Wide-Temperature Flexible Zinc-Ion Batteries

The booming development of flexible wearable electronics requires safe, deformable, and sustainable aqueous zinc-ion batteries (AZIBs). Liquid electrolytes suffer leakage, zinc corrosion, and dendrite growth, while the recently reported hydrogel electrolytes fail to balance biodegradability and mechanical stretchability. Herein, we developed a fully biodegradable biomass dual-network hydrogel electrolyte fabricated via free-radical copolymerization of starch, gelatin, and acrylamide (AM) with ZnSO4 salts. Benefiting from abundant hydrogen-bond networks formed by renewable biomass skeletons, the tailored hydrogel effectively immobilizes free water to construct a water-poor interfacial microenvironment, simultaneously suppressing dendrite proliferation and electrolyte leakage. The hydrogel delivers an outstanding low-temperature tolerance and favorable ionic conductivity of 23.76 mS cm-1 (-20 °C) and contributes to accelerating redox reaction kinetics and improving the reversibility of the Zn plating/stripping process. Therefore, the assembled Zn||sodium vanadate battery delivers a high capacity of 350 mAh g-1 at 1.0 A g-1 with 100% Coulombic efficiency and 83% capacity retention over 700 cycles. Impressively, within a broad temperature window of 0-55 °C, the pouch cell could work under repeated bending states, and the hydrogel is fundamentally degraded within 20 days in natural soil. It provides a facile strategy for flexible and sustainable AZIBs with high performance.