Controllable preparation of flowered Cu-doped Zn1-xCuxMn2O4 spinel and its application in electrode materials for supercapacitors

Abstract

The design of high-performance electrode materials is a hot topic in supercapacitor research. A novel series of flowered Cu-doped Zn_1-xCu_xMn₂O₄ spinel prepared by a simple hydrothermal method is used as the high-performance supercapacitor electrode materials. The morphology and the structure of Cu-doped Zn_1-xCu_xMn₂O₄ spinel are characterized and analyzed by X-Ray Diffraction (XRD), Field-Emission Scanning Electron Microscope (FE-SEM), Fourier Transform Infrared Spectrometer (FT-IR), and X-ray Photoelectron Spectroscopy (XPS). The results indicate that Cu²⁺ ions successfully replace Zn²⁺ ions into the crystal lattices of Zn_1-xCu_xMn₂O₄ spinel and keep a similar flowered morphology with ZnMn₂O₄. However, the incorporation of Cu²⁺ ions in the spinel crystal lattices leads to little microstructure change in samples. Flowered ZnMn₂O₄ is self-assembled from fluffy-tipped micron rods. Flowered Zn_1-xCu_xMn₂O₄ spinel is self-assembled from smooth diamond-shaped nanostructures. The possible morphology formation mechanism of the flowered ZnMn₂O₄ might be the micelle formation of the structure-directing agent of sodium citrate in solution. Introducing Cu²⁺ ions into the spinel crystal lattices effectively contributes to the improvement of the capacitance and the cyclability of Cu-doped Zn_1-xCu_xMn₂O₄ spinel. Among them, Zn_0.7Cu_0.3Mn₂O₄ shows the highest specific capacitance with 281 F/g at a current density of 1 A/g and better cyclic performance with a capacitance retention rate of 77.4% after 1000 cycles.