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Pyrite iron sulfide (FeS 2) is a fascinating electrode material for energy reserve devices because of its high theoretical capacity, non-polluting nature and abundant resources. However, the practical application has been extremely inhibited owing to its poor rate capacity and short cyclability caused by volume change during charge/discharge processes. In this article, a novel nanocomposite that is hollow FeS 2 nanospheres encapsulated in N/S co-doped carbon nanofibers (FeS 2 CNFs) was synthesized through electrostatic spinning. The FeS 2 CNFs nanocomposite demonstrates a terrific specific capacity of 511 F g−1 at 1 A g−1 for all-solid-state supercapacitors. The FeS 2 CNFs as electrode material for sodium-ion batteries (SIB) displays a specific capacity of 827.7 mAh g−1 and possesses a capacity of 490.6 mAh g−1 at 0.05 A g−1 after 200 cycles. The results indicate that this encapsulated structure can guarantee the integrity of electrode materials. And the abundant defects in carbon nanofibers caused by N/S co-doping may increase electrochemical reaction sites to facilitate charge transfer. The N/S co-doped FeS 2 CNFs nanocomposite exhibits a great potential for applying in SIB and supercapacitors. • Hollow FeS 2 nanospheres are encapsulated in carbon nanofibers by electrostatic spinning. • In-situ S-doping can increase the electrochemical active sites. • The incorporation of carbon nanofibers can prevent the structure collapse of FeS 2. [ABSTRACT FROM AUTHOR]

High intrinsic ionic conductivity and a theoretical capacity of MoS 2 is well appreciated and gathered great attention for an electrode asset for energy storage applications. The MoS 2 layers inter connected with one-dimensional carbon nanofibers (CNFs) are successfully prepared to give a conductive three-dimensional network for the robust charge transfer kinetics. The MoS 2 nanosheets adhered together to form micro flowers accomplished by a simple hydrothermal process. Further, the nanosheets are allowed to grow over the electrospun CNFs directly. The structural, functional, and morphological characterizations unanimously revealed the nanocomposite formation. Also, the surface area has been determined by BET analysis and subjected to electrochemical studies as an electrode for supercapacitors. The nanocomposite deposited on the graphite sheet (1 × 1 cm2) displays the high capacitance counterparts of 903.9 Fg-1 achieved by a lower current density of 1 Ag-1 and maintained 94% efficiency even 5000 cycles after a charge-discharge process. This process was examined with the potential range of 0.8 V (−0.4 to +0.4 V) in 1 M KCl electrolyte. These results confirms the prepared nanocomposite can be used as a proficient electrode for the creation of high capacitance supercapacitors with good cyclability. Image 1 • Direct growth of MoS 2 on carbon nanofibers attained by facile hydrothermal process. • FESEM and XRD results confirms the MoS 2 encapsulated CNFs with hexagonal phase. • CV were employed with different electrolytes to evaluate the influence of ion size. • The prepared MoS 2 /CNF exhibits the specific capacitance of 903.9 Fg-1 at a current density 1 Ag-1. • It maintains 94% efficiency even after 5000 cycles. [ABSTRACT FROM AUTHOR]

Porous carbon nanofibers (CNFs) with high energy storage performance were fabricated with a single precursor polymer, 6FDA-TFMB, without the use of any pore-generating materials. 6FDA-TFMB was synthesized, electrospun, and thermally treated to produce binder-free CNF electrodes for electrochemical double-layer capacitors (EDLCs). Highly porous CNFs with a surface area of 2213 m2 g−1 were prepared by steam-activation. CNFs derived from 6FDA-TFMB showed rectangular cyclic voltammograms with a specific capacitance of 292.3 F g−1 at 10 mV s−1. It was also seen that CNFs exhibit a maximum energy density of 13.1 Wh kg−1 at 0.5 A g−1 and power density of 1.7 kW kg−1 at 5 A g−1, which is significantly higher than those from the common precursor polymer, polyacrylonitrile (PAN). [ABSTRACT FROM AUTHOR]

Tailoring the chemical structures of a precursor polymer for carbon nanofibers (CNFs) produced by thermal treatment of electrospun nanofibers was studied to prepare the electrodes for electrochemical double layer capacitors (EDLCs). To improve energy storage performance of CNF electrodes, 6FDA-durene nanofibers were crosslinked by a vapor crosslinking method, and subsequently carbonized. Chemical modification via crosslinking was confirmed by FTIR spectra while the conversion of crosslinked 6FDA-durene into carbon was done by Raman spectroscopy. Electrochemical performance of these CNF electrodes was evaluated by assembling coin cells, and the CNFs derived from crosslinked 6FDA-durene nanofibers showed higher specific capacitances, energy densities and cycling stability than those from non-crosslinked ones. It was also shown that CNFs prepared using 1 min crosslinking exhibit the highest energy storage performances, a specific capacitance of 301 F g−1 (at 10 mV s−1), and the maximum energy density of 11.1 Wh kg−1 (at 0.5 A g−1) and power density of 1.8 kW kg−1 (at 6 A g−1). Surface area and porosity of CNFs, which is critical for the performance of EDLC electrodes, were studied by nitrogen adsorption/desorption measurements, and it was clearly seen that surface crosslinking of precursor polymers improved surface properties of the resultant CNFs. [ABSTRACT FROM AUTHOR]