Freestanding composite electrodes of MnO_xembedded carbon nanofibers for high-performance supercapacitors

Abstract

Manganese oxide/carbon nanofiber (MnO x /CNF) composites were successfully fabricated as freestanding electrodes through incorporating different manganese sources of nanostructured MnO 2 or Mn(CH 3 COO) 2 $4H 2 O into polyacrylonitrile (PAN) solution by electrospinning and a subsequent carbonization method. The MnO 2 with a rod-like hierarchical core-corona nanostructure was selfprepared by a hydrothermal method using polyvinylpyrrolidone (PVP) to control the size and morphology of nanoparticles. The morphologies and structures of the MnO x /CNF composites were characterized by means of field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. MnO x /CNFs produced from Mn(CH 3 COO) 2 $4H 2 O exhibited good flexibility with uniform dispersion of small MnO x particles in the loose structures of the CNFs. In contrast, MnO x /CNFs derived from MnO 2 displayed relative brittle mechanical properties. The electrochemical performances of the two composites were investigated by cyclic voltammetry, galvanostatic charging/discharging and impedance measurement techniques. The resulting MnO x /CNFs demonstrated excellent electrochemical performance with great rate capability, low internal resistance and long-term cycling stability. Composites produced from Mn(CH 3 COO) 2 $4H 2 O delivered a specific capacitance of 211 F g À1 at 0.25A g À1 in 0.5 M Na 2 SO 4 electrolyte These results suggest that such freestanding MnO x /CNF composites would be promising electrodes for highperformance supercapacitors.

Achieving highly practical capacitance of MnO2 by using chain-like CoB alloy as support

“…Electrochemical capacitors (ECs) have attracted great interest in the energy storage sector owing to their high energy capability, reversibility, reliability and long cycling stability 1, 2 . In an EC, the type of electrode material plays a key role for its performance and thus strenuous endeavor has been devoted to exploring various electrode materials.…”

Cage-like MnO 2 -Mn 2 O 3 hollow spheres with high specific capacitance and high rate capability as supercapacitor material

“…The higher CMHS value coincides with its higher BET value, which is in accordance with theory [37][38][39][40] . In addition, the specific balance of mixed phases in CMHS may be another factor contributing to its higher observed specific capacitance, resulting from possibly improved surface conductivity [26][27][28][29] . To determine the electrochemical performance of CMHS and MHS under galvanostatic cycling conditions, cycling was carried out over a 0.05 A g -1 to 5 A g -1 current range (Fig.…”

Facile Synthesis of Single‐ and Multi‐Layer Graphene/Mn3O4 Integrated 3D Urchin‐Shaped Hybrid Composite Electrodes by Core‐Shell Electrospinning

“…However, in the case of PANI@Mn 3 O 4 /TEGO−CF electrode, there is a serious drop in the calculated specific capacitance based on the discharging time (Table S2) while there is a nonlinearity with longer charging time rather than discharging time which is similar to a quasi‐reversible electrode behavior . During charging process, the irreversible electrochemical polarization fasten the faradaic reduction of manganese oxide into soluble manganese ions in electrolyte and thus decrease the discharging time . The cycling stability of the samples was carried out under a current density of 1 A/g for 1000 cycles of charging‐discharging shown in Figure c.…”

“…[31] During charging process, the irreversible electrochemical polarization fasten the faradaic reduction of manganese oxide into soluble manganese ions in electrolyte and thus decrease the discharging time. [34] The cycling stability of the samples was carried out under a current density of 1 A/g for 1000 cycles of chargingdischarging shown in Figure 9c. PANI@Mn 3 O 4 /TEGOÀ CF and PANI@Mn 3 O 4 /GLSÀ CF exhibited 66% and 89% retention of capacitance.…”