An integrated flexible zinc-air battery with sensing and controlled release: A lignin-containing nanocellulose hydrogel electrolyte design

L -CNF-reinforced hydrogel electrolyte achieves 336 mS cm −1 conductivity and 320% stretchability. • Flexible Zn-air battery delivers 50.5 mW cm −2 power density and 33 h cycling stability. • Integrated system enables on-demand drug release and wearable sensing, expanding biomass applications. Conductive hydrogels with high ionic conductivity, excellent mechanical properties and excellent water retention are still widely concerned in the field of flexible electronics. In this study, a low-cost, green and simple modification strategy was used to prepare a double-crosslinked alkaline hydrogel electrolyte composed of lignin-containing cellulose nanofibrils ( L -CNF), polyvinyl alcohol (PVA) and polyacrylamide (PAM) to improve the performance of flexible zinc-air batteries (FZABs). The mechanical properties of the hydrogel, ionic conductivity, and water retention capacity were optimized through varying the additive amounts of L -CNF. The findings indicate that the composite hydrogel electrolyte exhibits optimal performance at an L -CNF content of 0.15 g，exhibiting an ionic conductivity as high as 336.42 mS cm −1 , water retention of 52% after 10 days, and tensile strain of 320% under 70 kPa stress. The FZABs based on this hydrogel electrolyte achieved a peak power density of 50.5 mW cm −2 , demonstrated stable discharge for 689 min at 2.0 mA cm −2 , and displayed cycling stability over 33 h. The hydrogel electrolyte has excellent flexible sensing performance with a gauge factor of 3.10. In this work, green and low-cost biomass L -CNF is used as a functional modification filler, which provides a new design idea for the multifunctional integration of biomass resources in flexible energy devices.