Fabrication And Electrochemical Performance Researching Of NiCo₂O₄ And NiCo₂O₄/CNTs Nanocomposite Film Electrodes

Available high-performance electrode materials obtained from simple synthesis methods at a reasonable cost can be the key to drive the practical application of supercapacitors forward.Binary oxide NiCo₂O₄,has recently been investigated as a high-performance electrode material for energy storage systems because of its environmental benignity,abundance,low cost and great flexibility in structure and morphology.In our paper,firstly,the triblock copolymer-P123 was used as growth director to study the effects of its content and the reaction condition on the morphology and the electrochemical performance of NiCo₂O₄.The experiment found that the content of P123 have had great influence on the morphology of NiCo₂O₄,especially in water bath reaction.When the condition of P123 reached 5%,we got circle-like and nearly transparent NiCo₂O₄ nanosheet.Its specific capacitance could reach 623 F/g at a current density of 1 A/g,and remained 60% when the current density increased to 10 A/g.However,in hydrothermal treatment,where the ability of crystal growth strengthened,the effect of P123 on the morphology had a competition with the influence of stronger reaction condition on the crystal growth of NiCo₂O₄.In this condition,the urchin-like NiCo₂O₄ without any addition of P123 in reaction got the best electrochemical performance: the specific capacitance at 1 A/g current density reached 740 AF/g,and retained 59% at 10 A/g.Then,in order to improve the rate performance of NiCo₂O₄ electrode,as well as to avoid introducing polymer binder during conventional thin film electrode preparation,we prepared NiCo₂O₄/CNT self-standing electrode by combining continuous self-supported carbon nanotube film with NiCo₂O₄.The as-prepared core-shell structured NiCo₂O₄/CNT nanocomposite film reserved the CNT's flexibility,porous structure and high conductivity.And the carbon nanotube prevented aggregation of NiCo₂O₄ particles effectively,as well.In the experiment,it was found that both the loading of NiCo₂O₄ and the time of acid treatment with CNT had effects on structure and performance of the composite.Scanning electrical microscopy?SEM?and transmission electronic microscopy?TEM?observation showed that the web-like structure of the film were still reserved and each carbon nanotubes in the film were uniformly wrapped by ball-like nanoparticles?ca.5 nm?in the best performanced NiCo₂O₄/CNT core-shell structure.The three-pole measurements illustrated that the composite films possessed a capacitance of 828 F/g at 1 A/g,and remained nearly 80% at a current density of 20 A/g,revealing good high-rate performance.Moreover,the composite showed amazing cycling life by keeping more than 99% of its capacitance after 3000 cycles of charge/discharge at 5 A/g.On the other hand,in order to further evaluate the NiCo₂O₄/CNT composite film for real device application,asymmetric capacitors was fabricated and tested in two-electrode test system by using NiCo₂O₄/CNT and commercially available activated carbon as positive and negative electrodes?NiCo₂O₄/CNTs//AC?,respectively.The measurement testing results gave an energy density of 28.58 W h/kg at a power density of 0.7 kW/kg,and 14.18 Wh/kg when the power density was 14.18 k W/kg.