Electrochemical performance of the graphene/Y2O3/LiMn2O4 hybrid as cathode for lithium-ion battery

The graphene/Y2O3/LiMn2O4 hybrid wrapped the Y2O3 coated LiMn2O4 microsphere with graphene nanosheet was firstly synthesized. The structure and performance of the pristine LiMn2O4, Y2O3/LiMn2O4, graphene/LiMn2O4 and graphene/Y2O3/LiMn2O4 composites had been characterized by powder X-ray diffraction (XRD), energy dispersive analysis spectroscopy (EDAS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), galvanostatic charge-discharge, cyclic voltammetry (CV) and impedance spectroscopy (EIS). The results exhibited that the addition of graphene and Y2O3 did not change the bulk structure of LiMn2O4. The graphene/Y2O3/LiMn2O4 hybrid showed an initial discharge capacity of 129.3 mAh g−1, and the excellent capacity retention was still as high as 89.3% even after 500 cycles at a rate of 1 C and at an elevated temperature 55 °C. Meanwhile, it delivered a high capacity of 90.0 mA h g−1 even at 30 C. These remarkable enhancements indicated that coating Y2O3 and then wrapping graphene on the quasi-spherical surface of LiMn2O4 was an effective way to simultaneously improve the cycling stability and the rate performance of LiMn2O4. The Y2O3 coating could be accounted for the improved cycling performance by suppressing Mn3+ dissolution, and the graphene could enhance the conductivity of LiMn2O4 and thus improved the high rate capability.