Controlled Synthesis of Bifunctional NiCo2O4@FeNi LDH Core–Shell Nanoarray Air Electrodes for Rechargeable Zinc–Air Batteries

To boost the practical applications of rechargeable Zn–air batteries (ZABs), there is a need to design and synthesize bifunctional air electrodes with high catalytic activity and low cost used in self-supported electrodes. Herein, NiCo2O4 nanocones@FeNi layered double-hydroxide (LDH) nanosheets with a core–shell hierarchical architecture are prepared by a facile hydrothermal approach and fast electrochemical deposition. The NiCo2O4 nanocones act as scaffolds that provide more reaction sites and accelerate charge transfer to the FeNi LDH nanosheets. Specifically, the modification of the FeNi LDHs at the surface of NiCo2O4 nanocones modulates the chemical valences of Ni, Fe, and Co species and is controlled by the electrodeposition time, finally achieving the optimal bifunctional electrocatalytic activity. Primary ZABs manufactured by NiCo2O4@FeNi LDH have a peak power density (130 mW cm–2), open-circuit potential (OCV) (1.40 V), and great discharge stability. The rechargeable ZABs assembled with this bifunctional air electrode have a narrow discharge/charge gap of 0.65 V, high energy efficiency of 65.7% at 10 mA cm–2, and operate stably for >80 h.