Preparation of MgCo2O4/graphite composites as cathode materials for magnesium-ion batteries

Magnesium-ion batteries are fabricated with MgCo2O4/graphite composites as the cathode material. MgCo2O4 nanoparticles are prepared using a co-precipitation method. A three-dimensional mixing process is utilized to mechanically decorate MgCo2O4 nanoparticles on graphite particles. The MgCo2O4 spinel crystals of size ranging from 20 to 70nm on micrometer-sized graphite chunks are analyzed by using X-ray diffraction and scanning electron microscopy. The electrochemical properties of the as-prepared composites are well characterized by cyclic voltammetry, charge and discharge cycling, and electrochemical impedance spectroscopy (EIS). Surprisingly, the MgCo2O4/graphite composite with a relatively low proportion of MgCo2O4, compared with the other as-prepared composites, achieves the highest specific capacity of 180mAhg(-1) at a C rate of 0.05C. EIS results suggest that the electrical conductivity of the composite material is an increasing function of the graphite proportion. The superior performance of the MgCo2O4/graphite composite could be ascribed to the decoration of nanosized MgCo2O4 particles as well as to the increased conductivity provided by graphite.