The Electrochemical Performance Of Nitrogen Doped Carbon Nanofibers Prepared By Electrospinning

Electrospinning can prepare cont in uous polymer fiber simp ly a nd convenie nt ly, after furt her pre- oxidat ion a nd the high- temperature carbonizatio n, carbon nano fiber film can be obtained. We can fabricate carbon na nofiber films w ith d ifferent microstruct ure by us ing different carbon sources, controlling the cond it ions of the pre- oxidatio n, adding d ifferent porogen, us ing different carbonizat ion te mperature. Carbon na nofiber film t hat support metal oxide pa rtic les can be fabricated by the polymer so lut io n added meta l co mpounds. It can be direct ly used as the e lectrodes of supercapac itor. Supercapacitor has the advantages of high power dens it y, long cyc le life and excelle nt rate capabilit y, but the electrode materia l is the key to improve its perfor mance. There fore, the ma in work of this thes is is the preparation o f nitro gen doped porous carbon nano fiber film and its metal oxide composite w ith high specific surface area and good sur face wetting, w hich can be use for b inder- free supercapaci tors. The specific contents are as follows:(1)The nitro gen doped prous carbon nanofiber film was be fabricated based on electrospinning fro m a polyacr ylonitr ile(PAN) solut ion conta ining a llyl polyethylene(APEG), followed by the pre- oxidation a nd carbonizat io n, and its supercapacitor perfor mance was study. The results show that : APEG actsas the porogen,whic h influe nces the spec ific s ur face and e lectroche mica l properties of t he carbon nano fiber film. When t he adding we ight of APEG is 50% of the we ight of PAN, the specific surface up to 753 m2/g, the N content is 5.44%. When used as the b inder- free electrode for s upercap acitor, the obtained nano fiber film can e xhibit a specifitors capacitance of up to 302 F/g at the current dens ity o f 0.2 A/g. Though t he current dens it y increases by 200 times, the capacita nce only decreases by 50%. The capacitance losses only 5.6% after 2000 cycles at 10 A/g.(2)Polyvinylpyrro lidone(PVP) nanofiber film was prepared by electrospinning, after mult i- step pre- oxidation and carbonizat ion it trans formed to the nitro gen doped porous carbon nanofiber film. B y compar ion, it is fo und that whe n the qualit y percentage of PVP is 8%, the specific sur face area of the carbon nano fiber film carboned at 850?(PVP8- 850) is up to 680 m2/g, and XPS shows that the N content of the obta ined nano fiber film is 6.13%. When used as a binder- free electrode of supercapac itance, the nitrogen doped porous carbon nano fiber film can exhibit a specific capacitance of up to 290 F/g at t he current dens ity o f 0.2 A/g, it specific capacitance rema ins 167.3 F/g at the current dens ity of 50 A/g. The capacitance losses only 6.2% after 2000 cycles at 10 A/g.(3) PVP/coba lt acetate precursor fiber s were synt hes ized by electrospinning. They trans formed to C o3O4 /C nano fibers after the pre-oxidat ion and carbonizat ion. We stud ied the three electrode electrochemica l propert ies of the C o3O4 /C nano fibers and the perfor mance of asymmetr ic surpercapacitor which used the Co3 O4 /C nano fibers as an ode and carbon na nofibers as cathode. The d iffractio n peaks of X RD and XPS prove the existe nce of Co3 O4. The specific capacitance of the three electrodes reaches 314 F/g at 0.2 A/g. When the current dens it y increase s to 10 A/g, the specific capacitance rema ins 52.3%. The asymmetr ic capacitor in the vo ltage window of 1.4 V can work steadily, its specific capacita nce up to 251 F/g at the current dens ity o f 0.2 A/g, t he specific capacitance only re ma ins 34% as the current dens it y increases to 20 A/g. A fter 1000 cyc les, the capacit y retent ion rate is still 87%.