Synthesis And Electrochemical Performance Of NiCo₂O₄ And Their Carbon Nanotube Composites

Supercapacitors are focused favored by researchers because of their high specific capacity,long cycle life,and fast charging/discharging performance.The use of single electrode material is limited by its physical and chemical properties,and it is difficult to meet the actual application for supercapacitors.We can use composite materials as electrode materials to improve the electrochemical performance.The composite material can effectively combine the physical and chemical properties of the two materials and significantly improve the electrochemical perfprmance of electrode materials electrochemical performance.In this paper,a composite of nickel cobaltate and their carbon nanotube composites was prepared by hydrothermal method and annealing method.The morphology,structure and electrochemical performance of the material were studied.NiCo₂O₄ material was synthesized by hydrothermal method together with annealing treatment.The effecting factors of reaction were studied by orthogonal experiments.The optimum conditions is:hydrothermal temperature 120℃,The volume of absolute ethanol is 20mL,the molar ratio of cobalt salt and nickel salt is 2:1 and the hydrothermal time is 5h.The microstructure of obtained sample is sea urchin-like.At the current density is 1A·g^-1,the specific capacity of the NiCo₂O₄material is 696F·g^-1.5000 charge-discharge cycles at a current density of 10A·g^-1 with a capacitance retention of 96.2%.To improve the electrochemical performance of nickel cobalt oxide metal oxides,carbon nanotubes were added to the aqueous solution of metal ions,and a nickel cobalt oxide and carbon nanotube（CNT-NiCo₂O₄）composite material was synthesized by a hydrothermal method.The influencing factors of reaction were studied by orthogonal experiments.The optimum conditions is:hydrothermal temperature 150℃,the molar quantity of SDS is 2.5mmol,the molar ratio of cobalt salt and nickel salt is 2:1,the concentration of carbon nanotubes is 0.5mg·m L^-1 and the hydrothermal time is 5h.The composite materials prepared by the optimum conditions were characterized.XRD test analysis showed that the materials were composites of nickel cobaltate and carbon nanotubes,XPS test results demonstrated that the valence state of nickel in the composite materials was Ni²⁺and Ni³⁺,the cobalt valence state is Co²⁺and Co³⁺and the various valence state can store more energy for the material by the redox reaction.The SEM results observed that the CNT were anchored by NiCo₂O₄nanoparticles.The composite form a network structure.Electrochemical testing of the CNT-NiCo₂O₄composite material shows ultra-high electrochemical performance.At a current density of 1A·g^-1,the specific capacity of the CNT-NiCo₂O₄composite electrode is 1055F·g^-1,6500 cycles at a current density of 20A·g^-1 with a capacitance retention of 99.8%.