Multifunctional Energy Storage System using Electrospun Nanofiber Structure with Carbon Nanotube

Abstract

In this study, carbon nanofibers containing carbon nanotubes(CNTs) was fabricated using electrospinning process and the multifunctional structures which have a large capacity for energy storage was made with electrospun carbon nanofibers. Polyacrylonitrile (PAN) polymer nanofibers containing multi-wall carbon nanotubes (MWCNTs) were fabricated by electrospinning technique, and it was converted to carbon nanofibers through the stabilization and carbonization process using the heat treatment process. In addition, the activation process was performed to further improve the specific surface area of carbon nanofibers. Through this process, the specific surface area could be improved about several thousand times.<br/> A multifunctional supercapacitor was fabricated by vacuum bag molding process with carbon fiber fabrics and carbon nanofibers made by electrospinning. When carbon nanofiber was used as electrodes for structural supercapacitors, specific capacitance was increased about 4 times, and when activated carbon nanofiber electrodes was used, it was increased about 36 times. Although the MWCNT could not affect the specific capacitance for carbon nanofiber (CNF) specimens, the specific capacitance of activated carbon nanofiber-MWCNT (ACNF-MWCNT) was improved about 3-4 times than that of activated carbon nanofiber (ACNF) electrodes. Also, various kinds of separators were used to measure the specific capacitances of multifunctional energy storage systems.<br/> In order to evaluate mechanical properties of structural supercapacitors, tensile tests and interlaminar property experiments were conducted. Although the carbon nanofibers could not affect the tensile strength of the structural supercapacitors, the interlaminar fracture toughness of the structural supercapacitors with electrospun carbon nanofibers was improved about 20%. The electrospun carbon nanofibers inserted in the interfaces of carbon fabrics acted as velcro.<br/> Multifunctionality was calculated based on the structural efficiency and energy storage efficiency. As a result, it was found that the multifunctionality with activated carbon nanofibers electrodes containing MWCNT was the highest. Multifunctionality was calculated differently depending on the criteria of the structural and energy storage efficiency.