Tailored Porous ZnCo2O4 Nanofibrous Electrocatalysts for Lithium-Oxygen Batteries

Abstract

Lithium-oxygen batteries are considered a next-generation technology owing to their extremely high theoretical energy density despite many challenges such as low round-trip efficiency and poor cyclability. The air-cathode structure and pore properties play a key role in solving these problems. In this study, we fabricate ZnCo2O4 nanofibers and design a porous nanostructure using a facile electrospinning process and selective etching of ZnO as the cathode material in lithium-oxygen batteries. First, non-porous ZnCo2O4 nanofiber electrodes accomplish high catalytic activity and good cycling stability during 116 cycles with a limited capacity of 1000 mA h g(-1) at a current density of 500 mA g(-1). For enhanced catalytic activity and cyclability, ZnO included ZnCo2O4 nanofibers are prepared using a Zn-excess electrospun solution and porous ZnCo2O4 nanofibers are fabricated via selective etching of ZnO. Porous ZnCo2O4 nanofiber electrodes exhibit excellent electrocatalytic activity and cyclability for 226 cycles with a limited capacity of 1000 mA h g(-1) at a current density of 500 mA g(-1). The exceptional catalytic properties explain the synergistic effect of the one-dimensional nanostructure and porous structure with an appropriate pore diameter, providing a large active site and an efficient electron pathway during the Li2O2 formation/decomposition process.