A novel Mn3O4/MnO nano spherical transition metal compound prepared by vacuum direct current arc method as bi-functional catalyst for lithium-oxygen battery with excellent electrochemical performances

In this paper, a novel Mn3O4/MnO nano spherical transition metal compound as bi-functional catalyst for air electrode of lithium-oxygen battery is prepared by vacuum direct current arc method. Through physical property characterization, it shows that the Mn3O4/MnO particle size can be controlled between 40 and 60 nm and evenly distributed inside the carbon material. In addition, photoluminescence test result indicates that this material has better electronic conductivity and catalytic activity than traditional MnO2 catalyst owing to some defects in the crystal structure. The cyclic voltammetry results display that the oxidation and reduction reactions are both very obvious even at high scanning rate, although only one kind of catalyst is employed in the air electrode. This proves that the Mn3O4/MnO nano spherical transition metal compound can be as a bi-functional catalytic material. Electrochemical impedance spectroscopy also displays that the charge transfer resistance of Mn3O4/MnO catalyst is smaller and the ion diffusion speed is faster. Through charge and discharge test, it can be concluded that the voltage platform of the lithium-oxygen battery with Mn3O4/MnO as bi-functional catalyst is flat and the discharge voltage can reach 2.7 V. The specific energy can reach 7102 Wh.kg(-1) at 0.025 mA cm(-2) current density and a capacity limit of 1000 mAh.g(-1), it can carry out the 31 non capacity decay charge and discharge cycles. (C) 2018 Elsevier B.V. All rights reserved.