Preparation And Electrochemical Performance Of Flexible And Porous TaC/CNF Composites

With the increasing depletion of fossil fuel resources and emphasis on environmental protection,the development of alternative energy storage and conversion devices with high energy density and high power has attracted people,s attention.Because of its high power density,long cycle life,wide working potential and wide range of temperature range,the supercapacitor has been widely concerned in the research of energy storage device.Electrode materials have been widely studied as a key factor in supercapacitors,and carbon materials have been widely used in electrode materials due to their excellent electrical conductivity,large surface area and good chemical stability.The porous carbides derived carbon material has higher porosity and better conductivity than conventional porous carbon materials.Porous carbide-derived carbon,which is reported in the literature,is present in the form of powders,coatings and films,and can not be used as an electrode material independently.When used as an electrode material,the complete electrode must be prepared using polymer binder,which thus greatly reduces the electrochemical performance of the entire device.In the preparation of self-supporting electrode materials,electrospinning has become a mature preparation technology.In this paper,flexible,refractory and conductive tantalum carbide/carbon composite nanofibers(TaC/CNFs)film were prepared by electrospinning with a carbothermal reduction.In addition,a series of flexible porous tantalum carbide/carbon composite nanofibers(P-TaC/CNFs)film were synthesized by electrospinning,high temperature carbonation and metal ion etching.The porous TaC/CNFs film were used to prepare a series of flexible supercapacitors,and the electrochemical performances of these flexible supercapacitors were systematically studied.This paper is divided into the following two parts:The flexible,refractory and conductive TaC/CNFs film were prepared by using electrospinning with a carbothermal reduction.By changing the TaCl5 and PAN raw material ratio,a series of TaC/CNF films were obtained with different TaC contents.The TaC nanoparticles were homogeneously dispersed in the CNFs matrix observed by using TEM.Atomic Force Spectroscopy indicates that the single TaC/CNF has a high Young's modulus(up to 502 GPa).Electrochemical tests show that TaC/CNF has good conductivity.The study also found that TaC/CNFs film has excellent flexibility,no obvious damage was observed even after bending for 180 cycles and the corresponding electric conductivity still possesses 55% retention compared to no bending.In addition,the TGA study shows that the TaC/CNFs film has a refractory up to 1000 °C in Ar.Secondly,nickel nitrate hexahydrate were,in different proportions,added into the mixed solution of tantalum pentachloride(TaCl5),polyacrylonitrile(PAN)and N,N-dimethylformamide(DMF),followed by electrospinning,thermal reduction,and metal ion-assisted acid etching processes.Thus,a series of flexible P-TaC/CNFs film were obtained.The testing results show that TaC was successfully embedded into the PAN-based carbon nanofibers,and a large number of mesoporous structures were formed in the PAN-based TaC/C composite nanofibers.The specific surface area of the composite nanofibers was greatly improved.The high specific surface area isbeneficial to the diffusion of electrolytes,thus improving the electrochemical performance of the composite nanofibers.The P-TaC/CNFs-2 with the highest degree of graphitization and lowest charge transfer resistance shows the highest capacitance of 210 F/g at 0.75 A/g,a good cycle stability with capacitance retention of 95.4% after 10000 cycles,and a high energy density of 10.1 Wh/kg at power density of 1000 W/kg.