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• 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]

Lithium-ion battery (LIBs) applications using antimony (Sb) based anodes with high specific capacity and suitable operating voltage have showed tremendous potential. However, the large volume variation during electrochemical cycling limits their application. In this paper, M-Sb (M=Co, Ni) nanoparticles embedded in nitrogen doped carbon nanofibers have been prepared by an electrospinning method, 3D interconnected M-Sb@CN (NiSb@CN and Sb/CoSb 2 @CN) fiber composites are obtained finally. M-Sb nanoparticles are uniformly distributed in N-doped carbon nanofibers, which can prevent their direct exposure to the electrolyte. Compared with bare Sb-M and Sb-C binary electrodes, the M-Sb-C three-component composite electrodes show smaller volume change and stronger charge transport ability. The introduction of the transition metal (Co, Ni) not only serves as buffer substrate for volume change, but also regulates the properties of carbon fibers as a catalyst. High reversible capacities of 647.4 and 620.2 mA h g−1 of NiSb@CN and Sb/CoSb 2 @CN fiber composites can be maintained after 600 cycles at a current rate of 500 mA g−1. First principles calculation demonstrates that N-doping and the incorporation of transition metal M have favorable effect on the improved Li binding energy, offering a possibility for the material design of the high-performance LIBs. [ABSTRACT FROM AUTHOR]

Porous graphene-doped copper indium disulfide/carbon (p-GN@CuInS 2 /C) composite nanofibers were fabricated via electrospinning, in situ synthesis, and carbonization. A polyacrylonitrile (PAN) solution containing graphene oxide nanosheets, copper dichloride (CuCl 2 ), indium trichloride (InCl 3 ), and thiourea (Tu.) in a mixed solvent of N,N-dimethylformamide/trichloromethane (DMF/CF) was used as the precursor solution for electrospinning. The resulting porous GN@CuInS 2 /C nanofibers were 107 ± 24 nm in diameter, and graphene nanosheets anchored with chalcopyrite CuInS 2 nanocrystals 7–12 nm in diameter were overlapped and embedded in the carbon matrix, aligning along the fiber axial direction. The Brunauer–Emmett–Teller (BET) surface area of the p-GN@CuInS 2 /C composite nanofibers was 795 m 2 /g, with a total pore volume of 0.71 cm 3 /g. These values were significantly larger than those of the sample without graphene and CuInS 2 /C nanofibers. A dye-sensitized solar cell (DSSC) assembled using the p-GN@CuInS 2 /C nanofibers as the counter electrode (CE) delivered a photoelectric conversion efficiency of 7.23%, which was higher than the efficiencies of DSSCs assembled using the samples without graphene (6.48%) and with the CuInS 2 /C nanofibers (5.45%). It was also much higher than that of the DSSC with a Pt CE (6.34%). The excellent photoelectric performance of the p-GN@CuInS 2 /C CE was attributed to its special hierarchical porous structure, which facilitated permeation of the liquid electrolytes and provided additional active catalytic sites for the oxidation reaction of the electrolytic (I − /I 3 − ). The doping of reduced graphene oxide (RGO) resulted in the well-dispersed growth of CuInS 2 nanocrystals in the carbon nanofibers, which further increased the number of active catalytic sites and promoted electron and ion transfer. [ABSTRACT FROM AUTHOR]

Nanostructural carbon nanofibers are prepared through electrospinning in a precursor solution composed of polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and N,N-dimethylformamide. We investigate the effect of PMMA molecular weight on the morphology and electrochemical performance of the nanofibers. During pyrolysis, PMMA decomposition causes the nanofibers to develop from a porous structure into a hollow structure with increased PMMA molecular weight. The removal of PMMA also substantially increases the specific surface area and the pore volume of the carbon nanofibers. Electrochemical measurements reveal that the specific capacitance of the PAN/PMMA-derived carbon nanofibers with a low-molecular-weight PMMA exhibits a specific capacitance of 210 F/g, which is approximately 38% higher than that of the neat PAN-derived carbon nanofibers. Additionally, the fibers exhibit favorable cycling stability with a retention ratio of almost 100% after 2000 cycles. [ABSTRACT FROM AUTHOR]

The poor conductivity of anodic carbon materials at low temperature hampers their high-level applications in Li ion batteries (LIBs). Introducing some reliable metals with good electrical conductivity into anodes could alleviate these problems. In this work, the novel composites of Fe-added Fe 3 C carbon nanofibers (Fe/Fe 3 C CNFs) were synthesized via facile electrospinning method and used as anode materials for LIBs. The resulting anodes with Fe/Fe 3 C CNF materials exhibited a high reversible capacity of 500 mAh g −1 tested at 200 mA g −1 even after 70 cycles and excellent performance at room temperature. Importantly, it delivered a high capacity of 250 mAh g −1 at 400 mA g −1 even after 55 cycles at a low temperature of −15 °C. The superior low-temperature electrochemical performance of the Fe/Fe 3 C CNF anodes is associated with an improved effect of the highly conducting Fe at low temperature. [ABSTRACT FROM AUTHOR]

The excellent electrochemical performance of indium sulfide (In 2 S 3) in lithium ion batteries (LIBs) and sodium ion batteries (SIBs) prompted us to explore its energy storage mechanism in potassium ion batteries (PIBs). In this work, In 2 S 3 /C nanofibers are successfully synthesized by simple electrospinning and subsequent vulcanization. In K half cells, compared to commercial In 2 S 3 electrodes, In 2 S 3 /C nanofibers as anode materials for PIBs show outstanding electrochemical performance, which can deliver reversible capacities of 397.6 (25), 366.2 (50), 335.2 (100), 307.8 (200), 260.4 (500) and 212.2 mAh g−1 (1000 mA g−1), respectively. In K full cells, In 2 S 3 /C nanofibers can also show good potassium storage performance and can light up 15 light emitting diodes (LEDs). The superb electrochemical performance of In 2 S 3 /C nanofibers is due to the in-situ composite with self-nitrogen-doped carbon matrix and the nanoization of In 2 S 3 particles, which buffers the volume effect and improves the conductivity of the material during the potassium storage process. In addition, the mechanism of potassium storage of In 2 S 3 /C nanofibers was systematically studied by cyclic voltammetry (CV), ex-situ XRD, TEM and XPS methods. The mechanism of In 2 S 3 for K-ion storage can be described as the conversion reaction: In 2 S 3 + 6K+ + 6e− ⇌ In + 3K 2 S. [Display omitted] [ABSTRACT FROM AUTHOR]

A highly performance binder-free and freestanding cathode for Li-O 2 battery (LOB) receives much attention to solve the major obstacles including sluggish oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) kinetics, unstable cathode, and irrational architecture design. Herein, we develop an effectively electrospinning to embed the oxygen vacancy-containing Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) particles into carbon nanofibers (BSCF@C nanofibers) towards the self-assembly cathode with high ORR and OER performance. Predictably, the BSCF@C nanofibers successfully prevent the BSCF particles from aggregation, facilitate O 2 adsorption and diffusion, enhance the electron transfer, accelerate the Li 2 O 2 nucleation/decomposition, and enhance the stability of cathode. Different from the conventional cathode, the LOBs with the BSCF@C nanofibers cathode perform an outstanding electrochemical performance, which providing a high discharge specific capacity of 11976 mAh g−1 and ultralong cycling stability of 98 times at the current density of 400 mA g−1. Notably, this work opens up an opportunity for the perovskite oxides with high crystallization temperature for high-performance energy storage systems at ambient temperature. [Display omitted] [ABSTRACT FROM AUTHOR]

One dimensional SiO 2 /C composite nanofibers were successfully synthesized from precursor solutions with polyvinylpyrrolidone (PVP) as a carbon source by electrospinning with two-step heat treatment, comprising preoxidation at 280 °C in the air followed by annealing at 700 °C for 1 h in a reduced atmosphere. The effects of the preoxidation treatment on the morphology, chemical structure, and electrochemical properties of the synthesized materials were studied by scanning electron microscopy, X-ray diffraction analysis, Fourier transform infrared spectroscopy, and solid-state nuclear magnetic resonance spectroscopy. The two-step heat treatment had strong positive impacts not only on the morphology but also on the structure and electrochemical performance of the materials. Furthermore, free-standing SiO 2 /C composite nanofiber mats (FS–SiO 2 /C-CNFMs) were prepared from precursor solutions with different PVP concentrations by electrospinning with the two-step heat treatment. The FS-SiO 2 /C-CNFM obtained from the precursor solution with 5 wt.% PVP had a geometric mean diameter of 79 nm and a specific surface area of 642 m2 g−1. It exhibited high initial discharge and charge capacities of 1800 and 984 mA h (SiO 2 -g)−1, respectively, and finally retained a charge capacity of 754 mA h (SiO 2 -g)−1 after 200 cycles with 100% Coulombic efficiency. [ABSTRACT FROM AUTHOR]