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The combination of multiple electrode materials and their reasonable structural design are conducive to the preparation of composite electrodes with excellent performance. In this study, based on carbon nanofibers grown with Ni(OH)2 and NiO (CHO) prepared by electrospinning, hydrothermal growth, and low-temperature carbonization, five transition metal sulfides (MnS, CoS, FeS, CuS, and NiS) were hydrothermally grown on their surfaces, exhibiting that CHO/NiS had the optimal electrochemical properties. Subsequently, the effect of hydrothermal growth time on CHO/NiS revealed that the electrochemical performance of CHO/NiS-3h was optimal, with a specific capacitance of up to 1717 F g−1 (1 A g−1), due to its multistage core–shell structure. Moreover, the diffusion-controlled process of CHO/NiS-3h dominated its charge energy storage mechanism. Finally, the asymmetric supercapacitor assembled with CHO/NiS-3h as the positive electrode demonstrated an energy density of 27.76 Wh kg−1 at a maximum power density of 4000 W kg−1, and it still maintained a power density of 800 W kg−1 at a maximum energy density of 37.97 Wh kg−1, exhibiting the potential application of multistage core–shell composite materials in high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

• MnO 2 /CNF/Ag nanofabric electrodes are developed for flexible supercapacitors. • The brittle issue in the CNF electrode is greatly improved by an Ag incorporation. • The optimized MnO 2 /CNF/Ag electrode has a specific capacitance of 184 F/g at 1 A/g. • An energy density of 16.3 Wh/kg and a power density of 400 W/kg was achieved. • A capacitance retention rate of 87 % was demonstrated when subjected to bending. Flexible supercapacitors are gaining increasing popularity due to their potential in powering portable, wearable, and lightweight electronic devices. In this study, we have successfully developed a high-performance flexible electrode for quasi-solid-state supercapacitors by incorporating Ag into carbon nanofibers (CNF) through electrospinning, and growing MnO 2 as an active material on the electrode using an in-situ redox method. The Ag and MnO 2 co-decorated CNF electrode offers several advantages over conventional CNF electrodes, including an enlarged reaction area, higher charge storage capacity, and improved resistance to brittleness issues. Among all the quasi-solid-state supercapacitors tested, the MnO 2 -decorated electrode with an optimized Ag incorporation exhibited the highest specific capacitance of 184 F/g at a current density of 1 A/g, representing a remarkable 17-fold increase compared to the reference CNF electrode. Furthermore, the Ag and MnO 2 co-decorated electrode demonstrated an energy density of 16.3 Wh/kg and a power density of 400 W/kg at the same current density. Notably, the electrode exhibited excellent flexibility, with a capacitance retention rate of 87 % when subjected to bending with a curvature ranging from 5 to 1.25 cm. Our results suggest that the Ag and MnO 2 co-decorated CNF electrode holds great promise for flexible energy storage applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Summary: The design of inexpensive, binder‐free electrodes with high energy densities from naturally occurring compounds poses an interesting challenge for the construction of high‐performance supercapacitors. In particular, the synthesis of highly conductive carbon electrodes starting from miscanthus‐derived (silver grass) lignin with inorganic active sites is of interest for hybrid supercapacitors. In this work, Ni‐Mn sulfide nanograin networks are embedded on lignin‐derived carbon nanofibers (LCNFs) by electrospinning, followed by either direct vapor‐phase sulfidation or peroxidation‐induced sulfidation in an inert atmosphere. After either of the two different sulfidation processes, the direct transformation of Ni‐Mn sulfide on carbon nanofibers results in highly mechanically flexible freestanding electrodes, with a good specific capacity of 652.3 C g−1 at 1 A g−1, excellent current rate properties (73.6% capacity retention at 20 times the initial current density), and a cycling stability of 91.3% after 5000 cycles, even at the high current density of 10 A g−1. These outstanding properties are attributed to the rational design of surface‐embedded Ni‐Mn sulfide nanograins on the 3D LCNFs and the fascinating synergetic and graphitic nature of the fibrous web, which increases conductivity, influences the interfacial contact, and promotes highly electrochemically active sites on the electrode surface. Furthermore, an aqueous hybrid supercapacitor assembly of LCNFs‐NiMnS//activated carbon (AC) is demonstrated, with a maximum energy density of 52.4 W h kg−1 at a power density of 800 W kg−1, as well as 92.3% capacitance retention even after 10 000 cycles. This work not only establishes a high‐capacity anode but also provides an ideal strategy for designing flexible and conductive heterostructure network for various energy storage applications. [ABSTRACT FROM AUTHOR]

In this paper, we proposed the synthesis of CoFe nanoparticles (NPs) which have been deposited on carbon nanofibers (CNFs) with a facile electrospinning route followed by thermal reduction. The performance of obtained CNF supercapacitors are improved from 51 to 190 F/g (247 mF/cm2) at 0.5 A/g with the combination of CoFe NPs and graphitized carbon layers The device possessed an energy and power density of 6.6 Wh/kg and 125 W/kg, respectively. Furthermore, the capacitance retention can still maintain about 96.6% after 10,000 cycle test and it is worth noting that the cycling stability is ultrahigh. This research proves that bimetallic nanoparticles embedded in CNFs can elucidate new insights into the development new nanofiber electrode materials for the next generation of symmetric supercapacitors. [ABSTRACT FROM AUTHOR]

Highly porous carbon electrodes for supercapacitors with high energy storage performance were prepared by using a new precursor blend of aromatic polyimide (PI) and polyvinylidene fluoride (PVDF). Supercapacitor electrodes were prepared through the electrospinning and thermal treatment of the precursor blends of aromatic PI and PVDF. Microstructures of the carbonized PI/PVDF nanofibers were studied using Raman spectroscopy. Nitrogen adsorption/desorption measurements confirmed their high surface area and porosity, which is critical for supercapacitor performance. Energy storage performance was investigated and carbonized PI/PVDF showed a high specific capacitance of 283 F/g at 10 mV/s (37% higher than that of PI) and an energy density of 11.3 Wh/kg at 0.5 A/g (27% higher than that of PI) with high cycling stability. [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]