Effects of Mg-doping on distorted structure and enhanced electrochemical performance of V1-Mg O2 nanorods

Abstract

In this work, a series of V1-xMgxO2 samples (x = 0–0.030) were synthesized by hydrothermal method. The corresponding laws of Mg2+ doping concentration on the microstructures and electrochemical performance of V1-xMgxO2 were studied in detail. The XRD results indicated that the prepared V1-xMgxO2 samples showed monoclinic crystal phase and Mg2+ doping caused lattice distortion in the experimental doping range. The SEM and TEM results showed that all the V1-xMgxO2 samples were nanorods and well-crystallized. The positron lifetime spectra showed that the main defects in the V1-xMgxO2 samples were vacancy clusters. The concentration and size of the defects were affected by the combined action of ion radius and valence state of doped Mg2+. The electrochemical results revealed that the samples showed better electrochemical properties when the Mg2+ doping concentration x is 0.015. The high discharge capacitance of the x = 0.015 sample reached 140.6 F/g and the capacitor retention of this sample was still about 90 % after 1000 cycles.