Processing And Electrochemical Properties Of Carbon Nanofibers Prepared By Pressurized Centrifugal Spinning

The key to improve the performance of supercapacitors is the development of electrode materials with excellent electrochemical properties.Carbon fibers have low density,high conductivity and good chemical stability,processability and loadability.Thus they are excellent electrodes materials for electric double layer capacitors.Moreover,carbon nanofibers with finer diameter have more excellent electrochemical performance than traditional carbon fibers.In this thesis,carbon nanofibers were prepared by using pressurized centrifugal spinning and subsequent carbonization with polyacrylonitrile,and N-N dimethylformamide as the main raw material,as well dimethyl sulfone,polymethyl methacrylate and multi-walled carbon nanotubes as pore-forming agent and additive respectively.Compared with the conventional centrifugal spinning method,this method can produce fibers with finer diameter and higher yield at the same time.To improve the electrochemical performance of carbon nanofibers,several pore forming agents or additives were added to the precursor solutions.This study focus on the relationship between the ratio of raw materials,processing parameters,and the microstructure as well the electrochemical properties of carbon nanofibers.The optimized spinning parameters are as follows:spinning speed 8000rpm,receiving distance 15cm,spinning pressure 0.2MPa.The results of X-ray diffraction,infrared spectroscopy and scanning electron microscopy showed that the prepared polyacrylonitrile based carbon nanofibers were amorphous structures,and the diameter distribution of carbon nanofibers was near normal distribution with average diameter about between 400nm to 600nm.When the spinning pressure was increased,the fiber diameter decreased to a certain extent,with the lowest average diameter of430nm.Furthermore,the electrochemical performance of electrode with the prepared nanofibers was tested by an electrochemical workstation.The results showed that the electrochemical properties of the carbon nanofibers were improved when the porous agent or additive was introduced,and the cyclic performance of the carbon fiber was good.Compared with methyl-sulfonyl-methane,polymethyl methacrylate as a pore forming agent has better pore forming effect,and the specific surface area of carbon nanofibers reaches 617m~2/g.At the same time,Faraday pseudopotential is introduced to increase the specific capacitance to 134F/g.However,when the methyl-sulfonyl-methane was used as the pore forming agent,the specific capacitance of the carbon nanofibers was 89F/g,and the specific capacitance increased significantly with increasing the spinning pressure.Furthermore,the spinning nanofiber presents a network structure with good electrical conductivity in case of multi wall carbon nanotubes as additives,and the increase of the additive content can increase the specific capacitance effectively which reached the maximum of 79F/g.