Well-dispersed NiFe nanoalloy embedded on N-doped carbon nanofibers as free-standing air cathode for all-solid-state flexible zinc-air battery

Flexible zinc-air battery (ZAB) is a viable candidate for energy storage in upcoming flexible-wearable technologies. Non-noble transition metal alloys are used to synthesize oxygen evolution reaction (OER) catalysts to facilitate this development. However, inhibiting self-aggregation and promoting high OER activity in alloy nanoparticles is still challenging. Anchoring metal alloys to carbon support materials may produce a strong metal alloy‑carbon support couple, thereby preventing nanoparticle aggregation. Here, the combination of polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), pyrrole, and Ni/Fe salts resulted in homogeneously NiFe nanoparticles embedded in the free-standing nitrogen-doped‑carbon nanofiber (NiFe-N@CNF), produced via electrospinning and followed by carbonization. The NiFe-N@CNF shows a high OER activity with an overpotential of 351 mV. Importantly, good structural stability of NiFe-N@CNF results in superior OER stability with no voltage change after 14 h of chronopotentiometry stability test. The constructed rechargeable aqueous ZAB with NiFe-N@CNF as the air–cathode displays high peak power density (179 mW cm−2) and high stability up to 500 h. With its flexible properties, free-standing NiFe-N@CNF is also used as all-solid-state ZAB cathode, exhibiting stable performance under both flat and bending conditions, proving the promising application of NiFe-N@CNF for flexible-wearable technologies.