Metal-organic frameworks derived spinel NiCo_2O_4/graphene nanosheets composite as a bi-functional cathode for high energy density Li-O_2 battery applications

摘要

Electrode materials having a combined heterostructure morphology can boost the electrochemical performance of energy conversion and storage applications. In this paper, we prepared three-dimensional (3D) porous NiCo2O4 dodecahedron nanosheets (NCO) from a metaleorganic framework template (ZIF-67) and incorporated them with two-dimensional (2D) multilayer graphene nanosheets (GNS) through a simple and rapid ultrasonication process. The combination of these 3D/2D nanostructures created effective interfaces between the NCO and GNS components that enhanced the intrinsic electronic properties and increased the number of active catalytic sites on the NCO@GNS surfaces. Accordingly, the NCO@GNS electrocatalyst displayed superior kinetics for both the oxygen reduction and evolution reactions in both aqueous and non-aqueous electrolytes and could be fabricated into an air-cathode for Li-O-2 battery applications. The NCO@GNS air-cathode delivered a specific storage capacity (7201 mA h g(-1)) higher than those of the NCO and commercial carbon black electrodes. We tested the durability of the Li-O-2 battery featuring the NCO@GNS cathode in a new PAT-cell configuration; it exhibited long-term cyclability for 200 cycles with a limited capacity of 500 mA h g(-1) at a current density of 100 mA g(-1). This cathode design featuring meso- and micropores shortened the pathways for Li+ ion diffusion and ensured rapid electron and oxygen transfer, thereby increasing the lifetime of its corresponding Li-O-2 battery. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.