A Unified Polymer Hydrogel Electrolyte Integrating Robust Adhesion, Self‐Healing, and Oxygen Permeability in Flexible Neutral Zn‐Air Batteries

ABSTRACT Polymer hydrogel electrolytes hold significant promise for Zn–air batteries due to their excellent flexibility, non‐flammability, and leak resistance. However, their practical application remains constrained by zinc dendrite growth and intrinsic trade‐offs among ionic conductivity, oxygen permeability, mechanical strength, and both interfacial and environmental stability. Herein, we report a neutral, 3D physically cross‐linked PFCD hydrogel engineered via the synergistic combination of a tight coordination network of small Fe 3 + ions and a broader hydrogen‐bonding network of β‐cyclodextrin, with in situ incorporated N‐carboxyethyl chitosan. This hierarchical architecture endows the PFCD hydrogel with high adhesion (50 kPa), superior ionic conductivity (113.2 mS cm − 1 ), and significant oxygen permeability (4.1 Barrer). Additionally, the hydrogel exhibits autonomous self‐healing (99% efficiency in 3 h), exceptional stretchability (1600% elongation), and robust interfacial contact (withstanding 1000 folding/stretching cycles), while effectively suppressing zinc dendrite growth and resisting CO 2 degradation. Assembled flexible neutral Zn–air batteries (FNZABs) achieve high power density (59 mW cm − 2 ) with stable operation over 3000 cycles. Furthermore, the fabrication of leakage‐free, closed‐system FNZABs demonstrates the hydrogel's dual role as both an electrolyte and an oxygen‐permeable encapsulation membrane. This integrated strategy effectively addresses critical interfacial and stability challenges essential for advanced flexible energy storage systems development.