Recently, owing to the high energy density and excellent security, wearable Zn-air batteries (ZABs) have been known as one of the most prominent wearable energy storage devices. However, sluggish oxygen reaction kinetics of oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in the air-breathe cathode seriously has limited further practical applications. In this work, we synthesize a NiCo2O4 nanocrystal/MXene hybrid with strong Ni/Co-F bonds. The prepared MXene-based hybrid composites show remarkable ORR and OER electrocatalytic activity, which results in the fabricated solid-state ZAB device to achieve an open-circuit voltage of 1.40 V, peak power density of 55.1 mW cm-2, and energy efficiency of 66.1% at 1.0 mA cm-2; to the best of our knowledge, this is the record performance among all reported flexible ZABs with MXene-based air cathodes and comparable with some noble metal catalysts. Moreover, even after cutting and suturing, our flexible solid-state ZAB devices are tailorable with high rate of performance.
Keywords: MXenes; NiCo2O4 nanocrystal; Zn−air batteries; bifunctional electrocatalyst; wearable batteries.