No abstract

Nonaqueous Li−O 2 batteries have remarkable potential for use in future-generation sustainable green energy storage systems. Perovskites of the type ABO 3 provide bifunctional electrocatalytic activity superior to that of dual mixed-metal oxides due to the presence of crystallographic defects and oxygen vacancies, arising from the multivalency of the A and B cations. In this study, we used a facile hydrothermal method with an ammonia solution to modify coralline-like ZrO 2 with Fe 0.5 Mn 0.5 O 3 (FeMnO 3 ) and graphene nanosheets (GNSs). The porous structure of the resulting ZrO 2 @FeMnO 3 /GNS system featured a high surface area and large volume, thereby exposing a great number of active sites. X-ray photoelectron spectroscopy revealed that the surface of the as-synthesized FeMnO 3 @ZrO 2 /GNS cathode material was rich with oxygen vacancies (i.e., a huge quantity of defects). This coralline-like bifunctional electrocatalyst possessed effective redox capability between Li 2 O 2 and O 2 as a result of its excellent catalytic activity in the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). We examined the charge/ discharge behavior of corresponding electrodes (EL-cell type for Li−O 2 battery) in the voltage range of 2.0−4.5 V (vs Li/Li + ). The synergistic effects of the high catalytic ability and coralline-like microstructure of our ZrO 2 @FeMnO 3 /GNS catalyst for Li−O 2 batteries resulted in its superior rate capability and excellent long-term cyclability, sustaining 100 cycles at 100 mA g −1 with a limited capacity of 1000 mAh g −1 . The cell overpotential was ∼0.14 V when adding LiI as a redox mediator, resulting in a more practical Li− O 2 battery with the ZrO 2 @FeMnO 3 /GNS catalyst. Therefore, ZrO 2 @FeMnO 3 /GNS catalysts having distinctive coralline-like structures can display outstanding bifunctional catalytic activity and electrical conductivity, suggesting great potential for enhanced Li−O 2 battery applications.