Concurrently Suppressing Side Reaction and Freezing in Flexible Zinc–Air Batteries with a Robust Eutectogel Electrolyte

Flexible zinc-air batteries (FZABs) represent an emerging energy storage technology, yet their development is hindered by the limitations of conventional hydrogel electrolytes, including poor water retention, low ionic conductivity, undesirable side reactions, and poor low-temperature applicability. Herein, a series of deep eutectic solvent (DES)-based eutectogel electrolytes are developed by dissolving polyvinyl alcohol in DESs composed of ethylene glycol and amides with varying carbon chain lengths. The formamide-derived eutectogel (FEP) exhibits superior hydrogen bonding strength and denser cross-linked network, enhancing mechanical robustness, ionic conductivity (184 mS cm^-1), and liquid retention (90.01% after 96 h in air). The synergistic effect of ─C═O and -NH₂ groups in formamide promotes the conversion of free water to bound water and restricts Zn(OH)₄ ^2- diffusion, which suppresses hydrogen evolution, corrosion, dendrite, and passivation. Moreover, CoFe alloy encapsulated in carbon nanotubes (CoFe-CNT), synthesized using formamide, serves as an efficient oxygen reduction catalyst. The assembled FEP-based FZAB achieves a peak power density of 121.1 mW cm^-2, a specific capacity of 800 mAh g_Zn ^-1, and stable operation across an ultra-wide temperature range from -115°C to 70°C. This work advances eutectogel technology and offers novel approaches to designing gel electrolytes with a wide operating temperature range and excellent electrochemical performance.