Bifunctional nickel ferrite-decorated carbon nanotube arrays as free-standing air electrode for rechargeable Zn–air batteries

Abstract

The rational design of cost-effective bifunctional air electrodes is of great significance to advance the practical application of rechargeable metal–air batteries. Herein, we report a three-dimensional, vertically aligned carbon nanotube array-supported nickel ferrite hybrid (NiFeO_x@VACNTs) as a large free-standing air electrode for rechargeable Zn–air batteries. As expected, the designed electrode exhibits exceptional catalytic activity and stability for oxygen electrochemical reactions. The rechargeable Zn–air battery using this integrated air electrode delivers a large peak power density of 194 mW cm⁻², along with ultrastable cyclability of over 1500 h at 5 mA cm⁻². Furthermore, the flexible solid-state Zn–air battery with free-standing oxygen electrode exhibits a stable discharge voltage even under bending condition, with a high discharge power density of 143 mW cm⁻². This work paves a valuable way for designing cost-effective, free-standing integrated air cathodes for Zn–air batteries and related energy conversion and storage technologies.