Enhanced electrochemical performance of MgFe2O4/SrTiO3 and MgFe2O4/SiO2 nanocomposite structures

MgFe2O4/SrTiO3 and MgFe2O4/SiO2 nanocomposites were prepared via a modified sol-gel auto combustion method. X-ray diffraction (XRD) patterns confirmed the formation of both MgFe2O4/SrTiO3 and MgFe2O4/SiO2 nanocomposite structures. Williamson-Hall analyses showed that MgFe2O4/SrTiO3 had a crystallite size of 18 nm, while it was 17 nm for MgFe2O4/SiO2. It was found that the lattice constant for MgFe2O4/SiO2 was longer than that for MgFe2O4/SrTiO3; thus, the cell volume was larger for MgFe2O4/SiO2 nanocomposite. Fourier transform infrared (FTIR) spectra for MgFe2O4/SrTiO3 and MgFe2O4/SiO2 nanocomposites revealed absorption bands corresponding to bending vibrations of the TiO6 octahedron and Si―O―Si with symmetric and antisymmetric stretching vibrations. The electrochemical characteristics showed that MgFe2O4/SrTiO3 and MgFe2O4/SiO2 nanocomposites exhibited similar initial discharge capacity values, while MgFe2O4/SrTiO3 had a higher coulombic efficiency of 64.1%. After 100 cycles, MgFe2O4/SrTiO3 delivered a discharge capacity of 311 mAh g−1, larger than MgFe2O4/SiO2. Furthermore, MgFe2O4/SrTiO3 nanocomposite demonstrated significantly improved high rate capability, with a capacity of 330 mAh g−1 and 65% retention of the 2nd cycle, compared to MgFe2O4/SiO2 (with a capacity of 252 mAh g−1 and 42% retention of the 2nd cycle) after the current density was returned to 100 mA g−1.