Atomically dispersed Fe-N-S-C anchored on pomegranate-shaped carbon spheres for oxygen reduction reaction and all-solid-state zinc-air battery

Flexible Zn-air battery (ZAB) plays a pivotal role in the eventual realization of wearable/portable electronic devices such as hearing aids and electronic wristwatches owing to its high energy density and stable working voltage. However, the efficiency and long-term durability are still inevitably limited by the sluggish kinetics of oxygen reduction reaction (ORR) in air electrode. Herein, we fabricated a planar all-solid-state rechargeable ZAB with excellent scalability by integrating atomically dispersed FeN_x anchored on nitrogen-sulfur dual-doped porous carbon spheres and a highly conductive poly (acrylamide-co-acrylic acid) solid polymer alkaline electrolyte. Owing to the introduction of sulfur in carbon substrate, the catalyst exhibits superior ORR performance over 20% commercial Pt/C. Specially, it also displays outstanding all-solid-state ZAB capacity with a maximum power density of 85.5 mW/cm², as well as ultralong cycle life for more than 40 h, which outperforms that of most conventional polyvinyl alcohol alkaline gel electrolyte-based flexible quasi-solid-state or all-solid-state ZAB. Density functional theory results reveal that the dopants N and S play a synergetic interplay in modulating the electronic structure of atomically dispersed FeN_x species and provide a fast electron transfer path for ORR.