Super stretchability and satisfactory water retention capacity via a dual-crosslinked hydrogel electrolyte for wide-temperature flexible zinc-air batteries

Rechargeable flexible zinc-air batteries (FZABs) are promising alternatives to lithium-ion batteries for portable and wearable devices. A critical component of FZABs is the gel polymer electrolyte (GPE), which faces challenges such as water loss and poor tensile flexibility under extreme conditions. These issues must be addressed to ensure high utilization of the Zn anode and air catalyst and to meet the demands of harsh environments. This study presents a dual-network GPE leveraging the physical crosslinking between polyacrylic acid (PAA) and κ-carrageenan (KC) for FZABs. The polar –COO- groups in PAA and the hydroxyl and glycosidic groups in KC form strong hydrogen bonds with H₂O molecules, achieving high water retention and strong adhesion to the electrode surface. Additionally, the dual-network structure and ionic bonds between the −OSO₃⁻ groups in KC and Na⁺ cations dissipate energy during stretching, enhancing tensile flexibility. Compared to PAA GPE, the PAA-KC GPE showed remarkable improvements, with maximum elongation increasing by 745 % to 710 %. The water retention rate of PAA-KC GPE exceeded 60 % after 107 h of air exposure. The cycle life of PAA-KC GPE-based FZABs (63 h at 2 mA cm⁻²) was 1.86 times longer than that of PAA GPE-based FZABs. Even under extreme temperatures (−20 °C∼80 °C), PAA-KC GPE-based FZABs demonstrated excellent stability. The developed PAA-KC dual-network GPE shows great potential for flexible energy storage under extreme deformation and temperature conditions.