Chaotropic Urea-Regulated PAM-Agar Hydrogel Electrolytes for Flexible Zn-Air Batteries

Abstract

Hydrogel electrolytes are central to flexible Zn-air batteries (FZABs) because they determine the ion transport and interface chemistry of the cathode and anode. However, the dense hydrogel networks restrict ion migration and lead to an increased level of polarization during battery operation. Herein, a facile additive strategy is developed by introducing urea, a chaotropic agent, into a dual-network polyacrylamide (PAM)-agar hydrogel. The dual-network hydrogel ensures mechanical robustness, while the urea untangles the polymer network and generates a porous structure with more ion-transport channels. The optimized PAM-agar hydrogel with 2 M urea delivers an 11.2% higher ionic conductivity than the urea-free counterpart and improves water retention ability. As a result, the assembled FZAB exhibits an open-circuit voltage of 1.408 V, a peak power density of 80.0 mW cm^–2, stable discharge for 130 h, and 320 charge–discharge cycles. This work demonstrates that chaotropic additive engineering is an effective route to regulate hydrogel ion transport microenvironments for durable FZABs.