A promising approach to prepare gel electrolyte and electrocatalyst derived from natural long-staple cotton for high-performance flexible Zn-air battery

Due to the high energy density and risk-free operation, flexible zinc–air batteries (ZABs) have the potential to be energy sources for wearable electronic devices. Nonetheless, the performance of quasi-solid-state gel electrolytes diminishes progressively throughout the ion-exchange process, primarily due to water evaporation on the exposed cathode side, which shortens the useful lifetime of ZABs. Herein, we propose a distinctive gel polymer electrolyte membrane comprising cotton fiber (CF) from natural long-staple cotton and polyvinyl acetate (PVA) to effectively extend the battery lifespan, which is due to that the addition of CF improves surface wettability , liquid absorption and retention, and ionic conductivity (1.53 × 10 −2 S cm −1 ) compared with single PVA electrolyte membrane. We also prepare a composite electrocatalyst (Co-N-C@GCF-950) by pyrolyzing the precursor of ZIF-67 in situ grown on the cotton fiber at 950 ℃. The flexible ZAB assembled with Co-N-C@GCF-950 as the cathode electrocatalyst and the CF-PVA membrane as the gel electrolyte shows a high open-circuit voltage of 1.5 V, and a stable charge-discharge voltage gap of 0.8 V for 11-h lifespan at a current density of 2 mA cm −2 under various bending conditions, which guides the future way of the application potential of environmental cotton fibers in the multiaspects for flexible metal-air batteries.