A fish-gelatin-modified multifunctional hydrogel with “salt-in-water” for dendrite-free flexible zinc-ion batteries

Aqueous zinc-ion batteries (ZIBs) have emerged as promising next-generation energy storage solutions due to their high safety. Hydrogel electrolytes have garnered intensive interest for their applications in flexible ZIBs, combining mechanical flexibility with dendrite-suppression capabilities. However, conventional hydrogels suffer from three critical limitations: insufficient mechanical robustness, interfacial instability, and excessive salt dependence. Herein, we report a novel fish gelatin (FG)-modified polyacrylamide (PAM) hydrogel electrolyte fabricated via a facile protein chain network repair strategy. The optimized FG/PAM hydrogel electrolyte with 1 M ZnSO 4 exhibits superior mechanical properties, enabling ZIBs with flexible dendrite-free and prolonged lifespan. Specifically, the FG-modified hydrogel achieved a compressive strength exceeding 1078 kPa under 90 % compression and showed strong adhesion to diverse substrates. Electrochemically, the FG/PAM electrolyte exhibits excellent corrosion resistance and zinc-nucleation regulation capabilities, delivering a stable coulombic efficiency (CE) of 99.26 % and cycling stability over 2238 h. These results highlight the FG/PAM hydrogel in addressing mechanical integrity, interfacial compatibility, and long-term cyclability, providing a viable pathway for advanced flexible energy storage devices.