Facile microwave-assisted hydrothermal synthesis and improved electrochemical performance of micro rhombus ZnMn2O4 anodes for Li-ion batteries

Abstract

• Rhombus ZnMn 2 O 4 micro sheets are synthesized by microwave-assisted hydrothermal route. • The micro sheet composed of primary nanoparticles can inhibit the volume change. • The synthesis conditions of ZnMn2O4 were optimized by orthogonal experiment. Spinel structure ZnMn 2 O 4 anode materials were synthesized via an inexpensive microwave-assisted hydrothermally route from metal acetate raw material in an aqueous solution. The effects of reaction temperature and time, compactness, and pH on the synthesis conditions were systematically studied by designing four-factor and three-level orthogonal test method. The reaction temperature has the most significant influence on the experiment. X-ray diffraction structure study shows that all nine groups of ZnMn 2 O 4 contain different contents of ZnO impurities. Rhombus-type ZnMn 2 O 4 micro sheets were identified by scanning electron microscopy. Among them, the Li/ZnMn 2 O 4 cells delivered an initial discharge capacity of 1057.3 mAh·g −1 and the capacity of 337.3 mAh·g −1 remains after 40 cycles for the as-synthesized sample under the optimized conditions of the reaction temperature at 200 ℃, the compactness of 60 vol%, the reaction time of 35 min and the pH value of 10. It is surprising to note that ZnMn 2 O 4 prepared under this condition exhibits more stable and superior cyclic performance than other samples, which is due to its unique morphology. Finally, the reaction mechanism of ZnMn 2 O 4 electrode material was studied by electrochemical test combined with the capacity differential curve. This research makes a step forward to the zinc manganese spinel oxide and shows that ZnMn 2 O 4 is a promising anode material for lithium-ion batteries.