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 Fe³ ⁺ 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 CO₂ 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.