Influence of Mg-deficiency on the functional properties of magnesium ferrite anode material

Abstract

Non-stoichiometric magnesium ferrites (MgxFe2O4) with different deficiency values (x = 0.5, 0.95 and 1) have been prepared applying the sol gel method. The resulting samples have been investigated using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The influence of Mg-deficiency on the electrochemical properties of magnesium ferrites has been explored. Rietveld analysis of XRD indicated that Mg deficiency causes a redistribution of cations among the tetrahedral and octahedral sites associated with the existence of vacancies and a reduction in both lattice parameter and grain size. XPS analysis has revealed the existence of iron ions (Fe3+) only and confirmed the existence of deficiency of both magnesium Mg2+ and oxygen O2– ions. The electrochemical measurements indicated improved performance; Mg-deficiency yields better cyclic performance during the first 50 cycles, however, the specific discharge capacity of Mg0.5Fe2O4 cell is dramatically decreased during the subsequent 50 cycles.