A highly durable zinc-air battery from a directly integrated FexNC@NiFe(OH)x bifunctional catalyst

Abstract

Rechargeable zinc-air batteries (ZABs) hold great promise for energy storage and conversion due to their high theoretical energy density, cost-effectiveness, and inherent safety. However, progress is constrained by sluggish oxygen electrocatalysis and instability at the air cathode. To address such issues, we resort to a directly integrated pseudo-3D composite electrocatalyst based on carbon cloth, on which Fe/Fe₃C- and N- co-doped carbon nanotubes are directly induced and then used to further intercalate NiFe hydroxide clusters, Fe_xNC@NiFe(OH)_x. This hierarchical electrocatalyst shows enhanced oxygen electrocatalysis (ΔE is 636 mV), rendering high efficiency and durability of ZABs. Such improvement can be attributed to the rationally integrated pseudo-3D structure with high conductivity, high density of active sites, interconnected porosity, and well-bonded components for accelerating electron transfer and ion diffusion while ensuring structural integrity. Moreover, the hierarchical structure increases the electrochemical surface area with superior surface hydrophilicity. As a result, the composite electrocatalyst shows great potential as a binder-free air electrode, as demonstrated in a rechargeable ZAB of a high power density of 85.1 mW cm⁻² and a long period of operation beyond 2000 cycles (350 h) without notable degradation, outperforming noble metal electrodes.