Preparation And Electrochemical Performance Of Co-Ni Bimetallic Oxide And Their Composites

Supercapacitors have drawn worldwide attention of researchers for their fast charging/discharging process,moderate energy density,longer lifespan and environmental friendliness.The use of a single species of electrode material is under various restrictions for its own weakness.We can use composite materials as electrode materials to improve the electrochemical performance.Co-Ni bimetallic oxide and their graphene composites have been synthesized by a mild hydrothermal method combined with a simple annealing treatment.The morphology,structure and performance Co-Ni bimetallic oxide and their graphene composites was studied by the related tests.The as-prepared Co-Ni bimetallic oxide with different morpholgies and properties can be obtained by controlling the reaction conditions.The optimum conditions is:hydrothermal temperature at 120?,the molar quantity of SDS is 1mmol,the molar ratio of cobalt salt and nickel salt is 2:1 and the hydrothe rmal time is15 h.The obtained sample is the flower-like NiCo₂O₄ microspheres constructed by interconnected nanosheets These results has been confirmed by XRD,SEM,TEM and other realted tests.The NiCo₂O₄ microspheres exhibit a high specific capacitance of1737 F/g at 1 A/g.The graphene composites have also been synthesized by a mild hydrothermal method combined with a simple annealing treatment.The as-prepared samples with different morpholgies and properties can be obtained by controlling the reaction conditions.The optimum conditions is:hydrothermal temperature at 140?,the molar quantity of SDS is 1.5 mmol,the molar ratio of cobalt salt and nickel salt is 2:1,the hydrothermal time is 9 h and the mass of the added graphite oxide is 40 mg.The obtained sample is NiCo₂O₄/rGO by XRD.SEM and TEM images show thatt graphene is covered with three-dimensional structure constructed by interconnected NiCo₂O₄ nanosheets.When the current density is 1 A/g,the specific capacity of the NiCo₂O₄/rGO composites can reach 2121 F/g.The specific capacity retention of NiCo₂O₄/rGO composites can reach 97.3%after 2500 times of charge and discharge cycles,which is better than 92.3%of pure NiCo₂O₄.This is mainly due to the synergistic effect between NiCo₂O₄ and rGO.