Synthesis And Study On Graphene And Co₃O₄/Graphene Composite About The Characteristics Of Electrochemistry

Graphene, a two-dimensional single layer of carbon atoms, has become a rapidly rising star on the horizon of materials science and condensed-matter physics. It has attracted trem-endous attention because of its larger surface area, good electrical and thermal conductivity properties and potential applications in energy storage materials.In this paper, graphene,Co3O4 and Co3CO4/graphene composite were synthesized using a solution-based synthetic route, respectively, and characterized by X-diffraction spectroscopy (XRD),transmission electron microscopy (TEM) and scanning electron microscopy(SEM) measurement. XRD pattern indicated that the structure of the nanoparticles are spinel Co3O4. TEM characterization show that Co3O4/graphene composites are made up of cobalt oxide nano particles with diameters of 10 nm and the graphene layers. Respectively, graphene pure Co3O4 and Co3O4/graphene composites using for lithium-ion battery have been studied. The results show that the graphene and Co3O4 have a high specific capacity for the first discharge. But the Co3O4/graphene composite show that the discharge and charge capacity is about 786.08 mAh-g-1 and 758.98 mAh-g-1, and a columbic efficiency of 96.55%. After 103 cycles, the discharge and charge capacity are 1005 mAh·g-1 and 975 mAh-g-1. These results demonstrated that the Co3O4/graphene composite electrode has remarkably good performance and reversibility.In order to investigate the different loads of Co3O4 on Co3O4/graphene composite influencing storage properties of lithium, we prepared four samples of Co3O4 in content of 27.39%,43.00%,60.14% and 69.35%. The study results show that the increasing of the content of Co3O4 lead to the specific capacity increase, but the charge-discharge testing results show that Co3O4 in content of 43.00% has good performance and reversibility. When the charge and discharge current was increased to 1860 mA-g-1, the specific capacity stabilized at 515 mAh-g-1We choosed the Co3O4/graphene composite in content of 43.00%, the results show that the composite has the faradic and the double-layer capacitance properties in the 6 mol·L-1 solution of KOH. The initial charge capacitance is 441 F·g-1, the discharge specific capacitance is 363 F·g-1. Its specific capaeitance maintaine 190 F·g-1 after 500 cycles, and it has good stability. The coulomb efficiency is above 96%, showing a good cycle performance and stability.