Asymmetric supercapacitors based on functional electrospun carbon nanofiber/manganese oxide electrodes with high power density and energy density

Abstract Carbon nanofibers modified with carboxyl groups (CNF-COOH) possessing good wettability and high porosity are homogeneously deposited with amorphous manganese dioxide (amorphous MnO 2 ) by potentiodynamic deposition for asymmetric super-capacitors (ASCs). The potential-cycling in 1 M H 2 SO 4 successfully enhances the hydrophilicity of carbonized polymer nanofibers and facilitates the access of electrolytes within the CNF-COOH matrix. This modification favors the deposition of amorphous MnO 2 and improves its electrochemical utilization. In this composite, MnO 2 homogeneously dispersed onto CNF-COOH provides desirable pseudocapacitance and the CNF-COOH network works as the electron conductor. The composite of CNF-COOH@MnO 2 -20 shows a high specific capacitance of 415 F g −1 at 5 mV s −1 . The capacitance retention of this composite is 94% in a 10,000-cycle test. An ASC cell consisting of this composite and activated carbon as positive and negative electrodes can be reversibly charged/discharged to a cell voltage of 2.0 V in 1 M Na 2 SO 4 and 4 mM NaHCO 3 with specific energy and power of 36.7 Wh kg −1 and 354.9 W kg −1 , respectively. This ASC also shows excellent cell capacitance retention (8% decay) in the 2V, 10,000-cycle stability test, revealing superior performance.