| With the increasing demand for miniaturization and convenience of electronic products,miniaturization of electronic components is the general trend.As the most commercial capacitors in the market,aluminum electrolytic capacitors(AEC)are used in AC filtering circuit.However,AEC in the production process often through winding column to increase its capacity.Meanwhile,large volume,low capacity of the characteristics of greatly restricted the development of AEC in the electronic components.As new energy storage devices,Supercapacitors(SCs)have the characteristics of high specific capacity and small volume occupancy compared with AEC.However,traditional electrochemical capacitors can not meet the requirements of fast ion diffusion and frequency response,which limits their applications in AC filtering field.At the same time,after the current research in this field,the SCs which can be charged and discharged quickly at high scan rate,and has excellent ion diffusion and high-rate performance still has research value.Therefore,it is urgent to develop SCs which can be applied in the field of AC filtering.Carbon Nano-Onions(CNOs)is a quasi-zero-dimensional carbon nano-material,whose structure is a spherical structure wrapped by concentric graphite layers.It has great research significance because of its potential application in the field of high frequency AC filtering.In this paper,CNOs precursors with size of 5.6/9.9/12.6 nm were prepared by thermal decomposition method,and then ordered interconnected mesoporous CNOs with controllable graphite layer thickness were prepared by carbonization,acid treatment and high temperature graphitization,the graphite layers are 4-5,7-8 and 10-11,respectively.Then CNOs particles were deposited on the surface of the metal current collector by electrophoretic deposition.The binder adhered CNOs to the surface of the metal current collector,and because the metal current collector and the highly graphitized CNOs had good electrical conductivity and interconnecting mesoporous structure,the charge transfer hindrance caused by the high interface resistance was effectively reduced.The optimal conditions of electrophoretic deposition were obtained by EIS analysis of SCs prepared under different deposition conditions.It was found that CNOs-5.6 with 5.6 nm CNOs precursor has the best electrochemical performance as the active material by analyzing the different sizes of CNOs in the assembled symmetric SCs,this is due to the larger specific surface area,the thinner graphite layer and the larger positive curvature of the outer surface of CNOs-5.6.The higher curvature of the outer surface facilitates the adsorption/desorption of electrolyte ions on the surface of the material.The equivalent series resistance based on CNOs-5.6 is 0.6?;at 120 Hz,it has 326.4 m F cm-2 area specific capacity and-79.7°impedance phase angle and RC time constant is 0.26 ms;at 2000 V s-1 scan rate,it can still be charged and discharged rapidly,which shows it has fast response ability,and its capacity can reach 0.94 m F cm-2 at current density of 0.1 m A cm-2,the capacity retention rate can reach 89.4%at current density of 0.7 m A cm-2.After 50,000 cycles at 0.2 m A cm-2 current density,99%capacitor retention and 100%coulomb efficiency can be achieved,all showing good energy storage performance.At the end of this paper,the practical test of CNOs-based supercapacitor in AC filtering application is presented.The results show that it can filter 60 Hz AC signal into DC signal.The experimental results show the feasibility of interconnecting ordered mesoporous carbon nano-onion structure in AC filtering and its excellent electrochemical performance.Carbon nano-onions played a certain role in promoting the application of AC filtering. |
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