Construction Of A Novel Spherical-Filament Binary Carbon Nanofibers Electrode And Its Application In Vanadium Redox Flow Battery

Along with the increasing improvement of environmental consciousness,clean energy has increasingly flourished.As one of the most preferable technologies for large-scale energy storage,vanadium redox flow battery(VRFB)shows a lot of advantages.As the place of electrochemical reaction in a vanadium redox battery,the electrode property has an important impact on the battery performance.Therefore,it is an effective way to enhance the power density and to reduce the energy storage cost by improving the electrode property,so as to promote the industrialization of vanadium redox flow battery.Electrospinning technology possess the advantages of controllability and flexibility.Herein,electrospinning and green hydrothermal synthesis are combined,and a novel spherical-filament binary carbon nanofibers electrode(ECNFs-SCMS)is constructed,which exhibit excellent mass transfer performance and electrochemical activity.As a result,the power density and energy conversion efficiency of VRFB are increased effectively by optimizing the electrode structure.Suitable pre-oxidation temperature is a necessary condition for preparing carbon nanofiber materials with stable structure and excellent activity.In the second chapter,the pre-oxidation temperature of electrospun nanofibers is optimized.The polyacrylonitrile based nanofibers are pre-oxidized in the temperature range of240 ??320 ?.The effects of pre-oxidation temperature on the morphology,structure and composition of carbon nanofiber materials are investigated by SEM and XPS.The influence mechanism of pre-oxidation temperature on the electrochemical performance of the prepared carbon nanofiber electrode is analyzed by CV and EIS.With the continuous research and optimization of electrode surface/interface resistance of vanadium battery,the electrochemical polarization and ohmic polarization of vanadium battery have been significantly improved,the concentration polarization is the main limiting factor of the power density in a VRFB.In order to improve the mass transfer performance of carbon nanofiber electrode,in the third chapter,hydrothermally synthesized carbon microspheres(SCMS)with suitable size are introduced into electrospinning precursor solution to prepare the ECNFs-SCMS with large pores.The structure and surface characteristics of the binary electrode are investigated by SEM,XPS,contact angle test,BET and Raman.The electrochemical performance and mass transfer performance of the electrode are studied by CV,EIS and LSV.Finally,the single VRFBs are assembled and the charge-discharge and discharge polarization tests are carried out to study the influence mechanism of the new structural electrode on the battery performance.Considering that high mass transfer carbon nanofiber materials are further endowed with certain functions,in this chapter,on the basis of the above work,tin-based catalysts with excellent catalytic activity are introduced into the surface of carbon microspheres by hydrothermal method.the ternary ball wire porous electrode material with high activity was obtained,which effectively improved the utilization efficiency of the catalyst.The surface morphology and structural characteristics of ternary composite porous carbon nanofibers are studied by SEM,XRD and contact angle tests.The electrochemical properties of the materials are investigated by CV,EIS and potentiostatic step.Finally,the battery performance are systematically investigated by using the ternary composite material as the negative electrode of VRFB.