Fish-Gill-Inspired Underwater Self-Breathing Zinc–Air Batteries

Compared with the rapidly developing lithium- and sodium-ion batteries, zinc-air batteries (ZABs) offer the advantages of safety and high energy density. Nevertheless, their applications in underwater conditions are currently limited due to the low oxygen levels in such environments. Drawing inspiration from fish gills, we have successfully constructed a self-breathing zinc-air battery (ZAB) that can extract dissolved oxygen from water and convert it to electrical energy. By utilizing a Co2Fe-NC catalyst and a large-window cathode, the ZAB demonstrates a continuous discharge duration of 68.6 h in the underwater condition, thanks to its well-engineered architecture, optimized catalyst, and gas diffusion layer. Meanwhile, the underwater ZAB outperforms fish gills as it also operates efficiently in air, exhibiting a high capacity of 740 mA h g–1 and a high power density of 320 mW cm–2. Additionally, prolonged cycling tests indicate the ZAB's capability for stable charging and discharging with minimal potential variation. This study introduces an innovative approach to the development of breathable underwater metal–air batteries.