Metal-organic frameworks derived spinel NiCo2O4/graphene nanosheets composite as a bi-functional cathode for high energy density LieO2 battery applications

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.

Automated summary

This study demonstrated the synthesis of 3D porous NiCo2O4 dodecahedron nanosheets combined with 2D multilayer graphene nanosheets, enhancing electrocatalytic performance for oxygen reduction and evolution reactions. The NCO@GNS cathode in Li-O-2 batteries exhibited superior specific storage capacity and long-term cycling stability, highlighting the potential for practical energy conversion and storage applications.