Synthesis And Electrochemical Performance Of Graphene/Metal Oxide Nanocomposite Materials For Lithium-ion Batteries

In this paper, nickle oxide and zinc oxide were synthesized using graphene as conductive matrix, aming to improve their electronic conductivity and cycling performance as the anode materials of lithium ion battery. The compositon, structure and morphology of the obtained products were characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA), Raman, scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). And the electrochemical property of the products were investigated by cyclic voltammetry (CV), galvanostatic charge/discharge (CD) and electrochemical impedance spectroscopy (EIS). The main contents are presented as follows:NiO-graphene (NiO-G) composites were fabricated by a hydrothermal-thermal decomposition method. The effect of hydrothermal temperature and time, and the use of reducing agent on material peoperties were studied. The NiO-graphene composites showed a specific capacity of713.6mAh/g after50cycles at the current density of100mA/g, accouting for98.6%of the theoretical capacity. When the current density was increased to1000mA/g, it still remained a discharge capacity of303.5mAh/g, The EIS showed the lower charge transfer impedance for NiO-graphene composites, compared to that of graphene and pure NiO.1D nanotubes (CNTs) were used to reduce the restacking of graphene nanosheets in NiO-graphene composites, thus the NiO-graphene-CNTs (NiO-G-CNTs) hybrids with a distinctive structure were fabricated. NiO nanoparticles with the paticle size of20-80nm were uniformly distributed on the3D network provided by graphene and CNTs. When tested as anode in lithium ion batteries, the hybrids delivered the first discharge capacity of1515.1mAh/g at the current density of100mA/g, and the capacity remained858.1mAh/g over50cycles. The specific capacity was up to675.4mAh/g at the current density of1000mA/g. When the current density was back to100mA/g, the capacity rapidly returned to its initial capacity at the current density of100mA/g at the first10cycles.Al-doped ZnO(AZO)/reduced graphene oxide(rGO) composites were prepared via a sol-gel method. Al was doped into the crystal ZnO, granular ZnO nanoparticles (60～150nm) were uniformly distributed on the reduced graphene oxide nanosheets. When charge-discharged at a current density of100mA/g, the initial discharge capacity of AZO/rGO composite was836.6mAh/g, the specific capacity was462.8mAh/g at the30th cycle.