N/P/Si Tri-Doped Polyacrylonitrile-Based Carbon Nanofiber As Electrode Materials For Supercapacitors

Electrode material is an important component that can influences the performance of supercapacitors. The most of commercial supercapacitors are carbon based supercapacitors which store energy by electrostatic attraction. Supercapacitors shows many advantages such as high power density, and execelent cycle performance, high reliability, excellent cycle performance. However their energy density is comparatively low which may hinders their practical applications.In this paper, nitrogen/phosphorus co-doped porous carbons and N/P/Si tri-doped nonporous carbon were prepared and their electrical performance were investigated; the mechanism of nitrogen/phosphorus/silicon tri-doped carbon in enhancing the capacitance of carbons was also discussed.（1） The N/P/Si-CNFs were fabricated by introducting varied small amounts of TEOS in the precursor solution of polyacrylonitrile in DMF wih 20wt% H₃PO₄, Liquid nitrogen isothermal adsorption curve, SEM, XPS were used to analysis the specific surface area, morphology and chemical valence of doping elementments. The results shows that the N/P/Si-CNFs are nonporous with very low specific surface area.The addition of TEOS to the PAN solution with H₃PO₄ will change the valence state of N in the PAN-derived CNFs. P-doping and Si-doping plays a synergistic role in improving the capacitance of N/P/Si-CNFs electrodes.（2） Nitrogen and phosphorus co-doped porous carbon nanofibers were fabricated by introducing large amounts of TEOS to PAN/DMF solutions with 20% percent of H₃PO₄, and subsequent carbonization and etching process by 1 mol/L NaOH sulutions. The results show that the capacitance is increased up to 320F/g in 1M H₂PO₄ due to the porous structure and doping effects. However the introduction of lots of pore structure give rise to the poor influence on rate performance because of poor electrical conoductivity of porous carbons.