Monodentate Acetate Anion Enhanced Hydrogel Electrolyte for Long-Term Lifespan Zn-Air Batteries

Flexible Zn-air batteries (FZABs) hold significant promise in diverse application scenarios with high safety and compatibility yet are still impeded by byproduct formation and poor water retention. Here, the neutral hydrogel electrolyte GAHE is engineered by in situ polymerizing acrylamide (AM) in a solution composed of cationic guar gum (CGG) and acetate salts to conquer the above challenges. The acetate anions (OAc^-) exert a pH near 7 to effectively inhibit the side reactions triggered by H⁺. Meanwhile, the monodentate OAc^- ions in LiOAc have fast ion diffusion kinetics and form hydrogen bonds between the released carbonyl groups and H₂O to further suppress water activity for great side reaction prevention and water retention. Additionally, the in situ polymerization strategy realizes a polymer with high mechanical properties and great electrochemical interfacial stability and further improves the water retention property with hydrophilic groups. Consequently, GAHE gives the FZABs a lifespan of 2050 h at room temperature and 2940 h at -35 °C. This work provides concepts for electrolyte design for water retention and side reaction inhibition properties of aqueous devices.