Robust and Highly Active FeNi@NCNT Nanowire Arrays as Integrated Air Electrode for Flexible Solid‐State Rechargeable Zn‐Air Batteries

The most challenging issue in flexible/portable energy storage devices, such as metal‐air batteries, is the insufficient electrocatalytic performance of the air‐electrode for oxygen reduction/evolution reactions due to low activity and decomposition of the electrocatalyst from the electrode's surface. In an effort to overcome these barriers, robust and highly active FeNi@NCNTs nanowire arrays are rationally synthesized on carbon cloth which directly serves as an integrated air‐electrode for zinc‐air batteries. FeNi@NCNTs/CC shows excellent bifunctional electrochemical performances toward oxygen reduction reaction (onset potential = 0.95 V, half‐wave potential = 0.77 V vs RHE) and oxygen evolution reaction (η = 252 mV@10 mA cm −2 ), and exhibits excellent stability after being tested for more than 720 hours. More importantly, flexible solid‐state rechargeable Zn‐air batteries directly equipped with the FeNi@NCNTs/CC air‐cathode are demonstrated to exhibit a high discharge voltage (≈1.0 V@2 mA cm −2 ) and a low charge voltage (≈1.65 V@2 mA cm −2 ), along with an excellent mechanical and cycling stability (voltage gap increased ≈0.03 V after 200 cycles). The novel designed air‐cathode and simple methodology for flexible solid‐state rechargeable Zn‐air batteries contribute valuable enlightenment toward the development of emerging portable electronics in practice.