Lithium-induced defect centers in nanorod-shaped zinc oxide for supercapacitor applications

Abstract

Lithium (Li) doped ZnO nanorods were synthesized in this work using the hydrothermal method by varying the Li ions concentration. The synthesized material was used as an electrode material for supercapacitor application, and the effect of the Li ions on the electrochemical properties was reported. The Li-doped ZnO nanorods were characterized using X-ray diffraction, electron microscopy, and Raman spectroscopy to obtain information on the structural and morphological environment. Electron paramagnetic resonance, Raman, and photoluminescence spectroscopy gave information on the defect environment of the materials, which plays a vital role in this work as a change in the defect structure directly influences the electrochemical properties. Finally, the electrochemical performance of the electrode materials was tested by assembling all-in-one supercapacitor devices using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic cycling with potential limitations as testing techniques. The result obtained showed extremely positive trends for this type of electrode material. The maximum specific capacitance was achieved for the 0.5% Li-doped ZnO, which showed a value of 700 F/g at 1 mV/s with an impressive energy density of 56 Wh/kg and excellent cyclic stability.