Hollow structure engineering of FeCo alloy nanoparticles electrospun in nitrogen-doped carbon enables high performance flexible all-solid-state zinc-air batteries

Hollow-structuring of active components is among the most effective strategies for improving the kinetics of oxygen electrode catalysts, benefiting from the much-improved active surface area, enhanced accessible active sites, and formation of the desired defects on the exposed surface. Integration of active hollow nanostructures with functionalized carbon nanofibers synergizes the electrochemical performance and mechanical flexibility, which are particularly of interest for all-solid-state zinc-air batteries (FASS ZABs). In the present work, we demonstrate that the electrospinning of Prussian blue analogs can give rise to hollow FeCo alloy nanoparticles assembled in nitrogen-doped carbon nanofibers (h-FeCo alloy/N-CNFs). The h-FeCo alloy/N-CNFs thus derived exhibit superior bifunctional activities for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), and impressive performance in rechargeable Zn-air batteries. When integrated into a rechargeable FASS ZAB, they exhibit a high open circuit voltage of 1.335 V and a stable discharge-charge plateau around 1.1 V to 2.0 V, together with a large voltage efficiency of 63.5%, under bending conditions.