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In this study, an electrospinning method was used to produce highly conductive freestanding carbon nanofibers (CNFs). The freestanding CNFs are compatible with hierarchical growth techniques, such as hydrothermal processes, for the nanostructure engineering of supercapacitor electrodes with enhanced electrochemically active sites. Therefore, the flower-like FeMoO 4 @CNF nanosheets were investigated to improve the electrochemical performance using aqueous and neutral electrolytes (Na 2 SO 4 and K 2 SO 4). The optimized FeMoO 4 @CNF electrode exhibits areal capacitances of 252 and 220 mF·cm−2 at a high current density of 2.5 mA·cm−2 with Na 2 SO 4 and K 2 SO 4 electrolytes, respectively. The wide potential window (1.6 V) of the symmetric supercapacitor delivered maximum energy densities of 22.4 and 19.6 μWh·cm−2 at a power density of 2 mW·cm−2 for Na 2 SO 4 and K 2 SO 4 electrolytes, respectively. [ABSTRACT FROM AUTHOR]

To overcome the drawback of carbon nanofibers (CNFs) such as the low energy density and low specific capacitance as electrode for supercapacitors, SiO 2 /PANI@CNFs composite was prepared by layer-by-layer (LbL) assembly technique, in which the SiO 2 served as a component for improving capacitive behavior. Polyaniline (PANI) is used as nucleation site for synthesizing SiO 2 particles as well as active material for improving capacitance. In this study, SiO 2 particles were synthesized using biosilicification process as a bioinspired, rapid, and facile synthetic route for SiO 2 particles at ambient temperature and pressure, etc. To elucidate effect of SiO 2 on the electrochemical properties, SiO 2 /PANI@CNFs samples were prepared by varying concentration ratio of tetraethyl orthosilicate (TEOS) to CNFs. It was observed that the specific surface area and the capacitance are highly dependent on the TEOS concentration. The capacitance of the composite prepared at the TEOS concentration of 0.19 mmol reaches 412 F g−1 at the current density of 1 A g−1. These results are attributed to increased specific surface area from interstitial voids between SiO 2 particles and hydrophilic nature of SiO 2 particles, which offers sufficient channels for rapid ion diffusion and leads easy accessibility to the active sites for the electrochemical reaction between electrode and aqueous electrolyte. Due to its excellent electrochemical and biocompatible properties, bioinspired SiO 2 inorganic material will promote the development of energy storage devices in biomedical and environmental electronics. [ABSTRACT FROM AUTHOR]

Enhancing the electrochemical performance while maintaining excellent mechanical properties of carbon nanofiber-based flexible electrodes remains a significant challenge, which blocks their potential application in advanced energy storage and conversion. Herein, taking advantage of the thermal stability difference between polyacrylonitrile and polypyrrolidone, we report a simple strategy to fabricate N-doped porous carbon nanofiber membranes with inter-fiber cross-linked structures via eccentric coaxial electrospinning combined with carbonization processes. During carbonization processes, the obstacles of large contact resistance are removed and sufficient contacts among electrospun nanofibers are formed, endowing the carbon nanofiber membranes with outstanding electrical conductivity (25.4 S cm−1) and flexibility in various forms. Further, NiCo 2 O 4 nanoneedles are in-situ decorated onto the prepared carbon nanofiber membranes to construct hybrid electrodes for improving capacitance. The hybrid electrodes (NiCo 2 O 4 @NPCNFs) achieve a competitive specific capacitance (capacity) of 1474.2 F g−1 (245.4 mAh g−1) at the current density of 0.5 A g−1, as well as good rate performance (78.0% capacitance retention at a current density of 10 A g−1). In addition, the assembled asymmetric supercapacitors exhibit a high energy density of 53.0 Wh kg−1. This study paves a promising way toward carbon nanofiber-based electrodes for application in energy storage systems. [Display omitted] • According to the different thermal stabilities of the polymers, cross-linked electrospun carbon nanofibers are prepared. • Design eccentric core-shell nanofibers to facilitate the outflow of the melting core to form abundant crosslinking points. • The novel carbon nanofiber membranes render robust flexibility and high electrical conductivity. • The assembled flexible supercapacitor can supply power stably and continuously even under severe bending states. [ABSTRACT FROM AUTHOR]

The development of advanced coal-based functional nanomaterials is of great significance for clean and effective utilization of coal resources. Herein, we report novel coal-based ultra-fine carbon nanosheets (UCNSs) prepared by chemical oxidation of bituminous coal with a high yield of 40.0 wt%. UCNSs show a lamellar size of 10–20 nm, mainly composed of 63.5 at.% carbon, 5.1 at.% nitrogen, and 31.4 at.% oxygen. The structural merits of suitable size distribution, enriched functional groups, and highly conjugated core enable the UCNSs showing a tri-functional reinforcement for carbon nanofibers prepared by electrospinning and carbonization. Thanks to the strong cross-linking effect and formation of entire conductive networks, the UCNS-embedded carbon nanofiber fabrics show 32.6 and 1.5 times improved mechanical strength and electrical conductivity, respectively, than the one without UCNSs. What's more, the exposed edges of UCNSs act as active sites for ultrafast capacitive energy storage, leading to the free-standing fabric with significantly improved capacitance and rate performance (191.2 F g−1 at 1 A g−1, 113.5 F g−1 at 50 A g−1) for aqueous supercapacitors. This work may provide a new thought for high-efficient and high-value-added utilization of coal resources. Ultra-fine carbon nanosheets with a high yield of 40.0 wt% were prepared through liquid-phase oxidation of bituminous coal, showing tri-functional (mechanical/electrical/electrochemical) reinforcement for carbon nanofiber fabrics. [Display omitted] • Ultra-fine carbon nanosheets with a high yield of 40 wt% were prepared from coal. • The inlaid UCNSs show tri-functional reinforcement for carbon nanofiber fabrics. • Exposed edges enable an ultra-fast pseudocapacitive energy storage ability. [ABSTRACT FROM AUTHOR]

The logical design and engineering of bimetallic oxide nanomaterials with porous carbon materials have had a significant impact on the development of high-performance electrode materials for energy storage devices in recent years. The vertical and uniform building of porous multimetal nanomaterials on the surface of nanoscale carbon fibers is difficult but not impossible. We present a self-templated metal-organic framework (MOF)-based strategy for the synthesis and assembly of bimetallic oxides/nanoporous carbon nanostructures (Ni–Fe–O/NPC) on porous carbon nanofibers (PCNFs). The vertical alignment of Ni–Fe–O/NPC at PCNFs favors a fast redox reaction by shortening the ion/electrode diffusion path at the electrode-electrolyte interface and helps enhance the overall electrochemical performance. As a freestanding electrode for supercapacitors, it has a high specific capacitance of 1419 F g−1 at 1 A g−1 and good cycling life with capacitance retention of approximately 88.5% after 10,000 cycles. The Ni–Fe–O/NPC@PCNFs-400//Fe 2 O 3 /NPC@PCNFs asymmetric supercapacitor (ASC) achieves a high energy density of 41.3 Wh kg−1 at a power density of 892.2 W kg−1 with a long cycle of life (20,000 cycles) and a high rate capability (78.6%), indicating its potential applications. [Display omitted] • MOF-derived metallic oxides on PCNFs as free-standing electrode materials for ASC. • Tetragonal rodlike Ni–Fe–O/NPC@PCNFs is successfully grown using Ni–Fe-MOF@PCNFs. • Vertical alignment of Ni–Fe–O/NPC at PCNFs provides sufficient redox-active sites. • The assembly of Ni–Fe–O/NPC@PCNFs//Fe 2 O 3 /NPC@PCNFs as an ASC delivers high energy density. [ABSTRACT FROM AUTHOR]

Triple-layered boron-containing carbon nanofibers (CNFs) with hollow channels (PPMPB) are fabricated via step-by-step electrospinning for high-performance freestanding supercapacitors. Polyacrylonitrile (PAN)-based CNFs in the first layer are chosen as the support layer material because of their excellent chemical stability and electrospinnability. The well-developed hollow channels provided fast ion diffusion in the second layer of PAN/poly(methyl methacrylate) (PMMA)-based CNFs. The surface boron functional groups constituting the third layer contribute to the pseudo-capacitance. The symmetric supercapacitor of the PPMPB electrodes delivers a maximum specific capacitance of 180 Fg−1 at 1 mAcm−2, a high energy density of 22.38 Whkg−1 at a power density of 400 Wkg−1, and an excellent retention rate of 96% after 10,000 cycles in aqueous solution. The excellent electrochemical performance is attributed to the unique sandwich nanostructure with a three-layer structure, in which the factors representing the electrochemical properties of each layer do not interfere with each other. Therefore, a moderate amount of boron and the high surface area of the triple-layer structured PPMPB can be fully utilized as an excellent conductive network and electroactive sites, which is expected in a high-performance supercapacitor electrode. [Display omitted] • Triple-layered boron-containing CNFs were fabricated by step-by-step electrospinning. • The CNFs in the first layer provide active adsorption sites for EDLC. • Hollow core present in the interlayer serves as an excellent conductive network. • A moderate amount of boron in the third layer is utilized as the electroactive site. • Symmetric PPMPB(20) electrode showed good rate capability and long cycle life. [ABSTRACT FROM AUTHOR]

Designing SnO 2 /carbon composites is an effective strategy to improve the conductivity and buffer the volume expansion of SnO 2. However, it remains a challenge to combine SnO 2 and carbon materials tightly as a stable integration. Herein, a facile and versatile strategy of Sn/SnO 2 nanodots anchored tightly into carbon nanofibers (CNFs) with the decoration of graphene quantum dots (GQDs) for high performance supercapacitor is reported. Through a simple electrospinning and carbonization reduction process, a novel multidimensional carbon skeleton of GQD/CNF effectively improves the conductivity, and importantly, abundant Sn–O–C covalent bonds are constructed to anchor SnO 2 nanodots tightly into GQD/CNF, suppressing SnO 2 aggregation and facilitating electron/ion transfer kinetics. Consequently, as self-supporting and binder-free electrode material, Sn/SnO 2 /GQD/CNF displays high specific capacitance of 168.6 mA h g−1 (1349 F g−1) at 1 A g−1 with excellent rate capability (88.9% retention at 20 A g−1). Furthermore, a flexible solid-state asymmetric supercapacitor based on Sn/SnO 2 /GQD/CNF and GQD/CNF achieves a high energy density of 32.3 W h kg−1 at a power density of 800 W kg−1 with remarkable flexibility and cycling stability (86.1% retention after 5000 cycles). The excellent electrochemical performances demonstrate that this novel carbon skeleton anchored active materials shows great potential for electrochemical energy storage applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Nickel cobalt phosphide/carbon nanofibers (NiCoP/C) with an average diameter of approximate 200 nm are prepared by electrospinning combined with calcinations. Carbon nanofibers with an average pore size of 10.77 nm as conductive skeletons support the dispersed NiCoP nanoparticles with the size ranging from 20 to 80 nm, providing abundant reactive sites and facilitating the electrochemical reactions. The specific capacitance of NiCoP/C reaches 478 F g−1 at 2 A g−1 in a 3 M KOH electrolyte, showing superior electrochemical properties compared to its counterparts. After 5000 charge/discharge cycles at 10 A g−1, 99.99 % of initial specific capacitance is retained. In addition, an asymmetric supercapacitor assembled using NiCoP/C as positive electrode and activated carbon as negative electrode exhibits an energy density of 16.72 Wh kg−1 at a high-power density of 7250 W kg−1. Furthermore, the capacitance loss of the supercapacitor is only 0.04 % after 5000 cycles at 10 A g−1, which is mainly attributed to the enhanced stability of NiCoP nanoparticles owing to the assistance of carbon nanofibers as the skeleton. The synergistic effects of NiCoP nanoparticles and carbon nanofibers result in the boosted electrochemical performances. This study demonstrates the potential application of carbon nanofibers as conductive skeletons for nanostructured electrodes. • NiCoP/C nanofibers were prepared by electrospinning without the emission of PH 3. • Carbon nanofibers acted as skeletons and conductive channels for NiCoP. • Assembled NiCoP/C//AC supercapacitor achieved 16.72 Wh kg−1 at 7250 W kg−1. [ABSTRACT FROM AUTHOR]

Exploring energy storage devices and hydrogen evolution reaction electrode materials with high efficiency electrocatalytic activity, high energy density and low cost has broad prospects, but there are still huge challenges. Compared with traditional energy storage devices, supercapacitors (SCs) are a new type of energy storage device with broad development prospects. However, their practical application is significantly limited by the energy density of electrode materials. The practical application of hydrogen evolution reaction (HER) is limited by the high cost and scarcity of Pt-based precious metal catalysts. It is essential to develop materials with stable structure, low cost and abundant reserves. Here, in this paper, CoS 2 and CoSe 2 composites embedded in carbon nanofibers (CNFs) (expressed as CoS 2 -CoSe 2 /CNFs) were synthesized by electrospinning combined with in-situ growth Zeolite Imidazolate Framework-67 strategy, carbonization and subsequent selenium sulfide process. When employed as the positive material in supercapacitors, a specific capacitance of 292.2 F g−1 is achieved at a current density of 1 A g−1. The specific capacitance of asymmetric supercapacitors (ASCs) assembled with CoS 2 -CoSe 2 /CNFs-5 as positive materials remains stable with no significant change observed in specific capacitance even after undergoing 10,000 cycles. At the same time, when a current density of 10 mA cm−2 is applied in a 0.5 M H 2 SO 4 electrolyte solution, an overpotential reading of 189 mV is observed. The evidence mentioned above showcases the significant capacity of this substance for application in electrochemical energy storage and conversion. • The synergy of different components regulates the electronic structure. • The as-obtained materials exhibited a good energy storage and conversion performance. • The retention of the ZIF-67 skeleton structure can increases the number of active sites. [ABSTRACT FROM AUTHOR]

[Display omitted] • The vacancy-defective graphene sheets are constructed successfully through polyacrylonitrile thermally mediated. • Vacancy defects on graphene sheets can enhance electrons/ions transport kinetics • The assembled aqueous zinc-ion hybrid supercapacitors exhibit a high energy density and outstanding cycling stability. The electrochemical behavior of graphene sheets in energy storage system is closely related to its electronic structures. Specifically, structural vacancy defects can expose more active sites and enhance the electrochemical performance. However, it is still a challenging problem to realize valid defect regulation on improving the reaction kinetics of electrode materials. Herein, vacancy-defective graphene sheets were constructed through the thermal mediated method via intercalation of polyacrylonitrile nanofibers. The vacancy defects were generated from the NH 3 gas resulting from polymer decomposition at gradient carbonization temperature. The obtained composites of the graphene sheets and carbon nanofibers demonstrate that the vacancy defects benefit to charge transport, allowing more electrons to pass through the interlayered structure, and enhance the adsorption capacitance during the reversible electrochemical process. In addition, the as-assembled Zn ion hybrid supercapacitors exhibit a high energy density of 129.9 Wh kg−1 and outstanding cyclic stability (99.8 % after 10,000 cycling). The confined polymer-mediated thermal modification strategy can afford abundant vacancy defective sites and exhibit promising outlook for constructing high-performance graphene-based electrode materials for Zn ion hybrid supercapacitors. [ABSTRACT FROM AUTHOR]

Schematic illustration of the preparation of porous carbons. [Display omitted] • The porous carbons with controllable architecture were fabricated by a dual-role KCl-assisted activation method. • KCl not only serves as an auxiliary template but also contributes to an enhancement in the melting of K 2 CO 3. • The prepared porous carbons possess well-developed pore structure and excellent electrochemical performance. • This work paves a path to prepare porous carbons via an environment-friendly and cost-effective route for supercapacitors. Preparation of high-performance electrode materials in a low-cost and simple way is of great significance for the application and development of supercapacitors. Herein, a dual-role KCl-assisted KOH activation method with low KOH consumption was employed to fabricate porous carbons with controllable architecture, using the coal liquefaction residue (CLR) as the raw material. It is indicated that KCl not only serves as an auxiliary template for pore-forming but also contributes to an enhancement in the melting of K 2 CO 3 , an intermediate of KOH activation, resulting in an improvement in the efficiency of KOH activation. As a consequence, the prepared samples possess highly developed pore structure even at a low KOH consumption, which endow them with excellent capacitive performance. The as-fabricated optimal porous carbon (LR-KPC-4) displays a maximum specific capacitance of 375 F g−1 at 0.5 A/g and superior rate capacity, which are much better than those of the porous carbon prepared without KCl. The fabricated symmetric supercapacitor shows a high specific capacitance of 256 F g−1 at 0.5 A/g, energy density of 8.9 Wh kg−1 at 125 W kg−1 and great cycling stability. This work demonstrates a facile strategy to efficiently convert CLR into porous carbons for high-performance supercapacitors. Meanwhile, it paves a promising way for value-added utilization of CLR. [ABSTRACT FROM AUTHOR]

Vanadium Nitride (VN) is attractive for energy storage due to its high conductivity (1.6 × 106 S/m) and specific capacitance (1350 F/g) but limited to alkaline electrolytes for redox. In contrast, V 2 O 3 is redox active but not very conductive. In these hybrids a mixture of VN and vanadium oxide (V 2 O 3) were encapsulated in electrospun carbon-nanofibers. A combination of VN and V 2 O 3 takes advantage of the high conductivity from VN and the redox activity from V 2 O 3. Additionally, having the vanadium encapsulated within the carbon can help with the stability as the electrolyte will not have direct interaction with the surface. These hybrids were made by in-situ nitridation of the encapsulated V 2 O 5 followed by ex-situ activation with carbon dioxide. The hybrids were characterized by XPS and Raman spectroscopy. Hybrids of VN/V 2 O 3 -CNF showed increased capacitance of 245 Fg−1 with energy and power densities of 70.2 Wh kg−1 and 1751 W kg−1 in ionic liquid electrolyte. The devices showed good cycle stability with ∼90 % retention after 10,000 cycles at a current density of 1 Ag−1. These findings highlight the potential of VN/V 2 O 3 -CNF hybrids as high-performance supercapacitor electrodes. The combination of high conductivity and redox activity, along with encapsulation within CNFs, opens promising avenues for advanced energy storage. [ABSTRACT FROM AUTHOR]

Developing high-performing and scalable electrode materials for supercapacitors and batteries has been of tremendous interest for the world's forthcoming clean and renewable energy transition. As a versatile material, Two-dimensional graphitic carbon nitride (g-CN) has been utilized in electrochemical energy storage (EES) applications due to its nitrogen-rich adsorption sites, cost-effective production, and tunable electronic structure. The electrochemical performance of pristine g-CN has been boosted by forming hybrid architectures with highly conductive carbon-based materials, such as graphene, reduced graphene oxide, carbon nanofibers, carbon nanotubes, and beyond (e.g., MXene). Using such heterogeneous compositions for EES applications has significantly increased in recent years. This study reviews the g-CN/carbon nanomaterial (CNM) hybrids, considering the dimensionality in nanomaterials, and underscores the influence of the material's dimensionality and the synthesis/fabrication routes. The effect of structural and physicochemical changes on the electrode's electrochemical performance after hybridization is presented comparatively. Besides, the comprehensive review outlines challenges and future improvements in g-CN/CNM hybrid materials for outstanding developments in energy storage systems. [Display omitted] • Graphitic carbon nitride (g-CN)/carbon nanomaterial (CNM) hybrids are reviewed for supercapacitor and battery applications. • The impact of the CNM-type on the hybrid electrode's performance is examined through a chemical and physical perspective. • An overview of how hybrid electrode synthesis affects ion/electron transport, surface area, and porosity is provided. • Design-oriented control of the physicochemical properties for enhanced electrochemical performance is exemplified. • g-CN/CNM nanoarchitectures are emphasized as electrode materials with the potential for easy scalability. [ABSTRACT FROM AUTHOR]

The synthesis of Laser-Induced Graphene (LIG) through the laser ablation process of carbon-containing materials is a rapid and scalable process which enables the production of graphene in a cost-effective manner. In recent years, metal oxide – graphene composite electrodes have gained a lot of importance due to their use in various Energy Storage Devices (ESDs). In our investigation, we manufacture composite electrodes of manganese dioxide (MnO 2) and LIG through a hydrothermal process and use it as electrodes in Flexible Supercapacitors. This method deviates from traditional procedures as it eliminates the requirement for binders in creating composite electrodes, given that MnO 2 can be directly deposited onto the LIG electrodes. The assembled all-Flexible Supercapacitor (FSC), featuring unique LIG-MnO 2 composite electrodes, showcased a remarkable areal capacitance of 66.5 mF cm−2 at 5 mV s−1 scan rate. The device also exhibited a very high areal energy density (2.3 mWh cm−2) and power density (19.7 mW cm−2) at 0.2 mA cm−2 current density. Also, 82 % capacitance retention was observed at the end of 2000 cycles and the device also exhibited a good flexibility during bending tests, as evidenced by an 80 % capacitance retention after 100 bending cycles. [ABSTRACT FROM AUTHOR]

This paper proposes a simple and rapid microwave-assisted phosphorus-oxygen doped porous carbon (P/O-PC) preparation strategy is proposed using potassium citrate, Phytic acid (PA), and ethanol under air atmosphere. PA can be used as both a phosphorus source and a microwave absorbing agent. The P/O-PC500–0.75 has a large specific surface area of 905 cm2/g. P/O doping introduces defects into the carbon structure, which enhances the capacitance of the porous carbon. The P/O-PC500–0.75 demonstrates excellent capacitance values of 330 F/g and 389.4 F/g in 6.0 M KOH and 1.0 M H 2 SO 4 , respectively (1 A/g). In addition, the symmetrical supercapacitors assembled with the P/O-PC500–0.75 exhibit good electrochemical stability over 5000 cycles at 5 A/g, with a capacitance loss of only 3.6%. This microwave-assisted strategy offers simplicity in operation and low energy consumption, providing a new and efficient pathway to prepare carbon materials in a fast and simple manner. [Display omitted] [ABSTRACT FROM AUTHOR]

Using renewable biomass precursors to develop high-performance carbon electrodes is a promising approach for the advancement of supercapacitors. This work proposes a feasible strategy to prepare self-supporting flexible porous carbon nanofibers by electrospinning and carbonizing the mixture of cuttlefish ink, polyacrylonitrile (PAN) and polymethyl methacrylate (PMMA). The impacts of cuttlefish ink precursor on the structure, elemental composition, and capacitance properties of carbon nanofibers have been studied. Herein, the unique structural advantage of cuttlefish ink can significantly optimize the porous structure of carbon nanofibers. Due to the hierarchical porous structure, large specific surface area, hollow channels and high nitrogen content, the carbon nanofibers offer a high specific capacitance of 364.8 F g−1 at 0.5 A g−1 current density, alongside desirable rate performance and cycle life. Furthermore, the carbon nanofiber electrode performs good mechanical flexibility. The flexible solid-state supercapacitor based on this electrode exhibits 14.1 Wh kg−1 energy density at 0.4 kW kg−1 power density, and 97.8% capacitance retention after 5000 cycles. The favorable capacitive properties make this carbon nanofiber material a potential candidate for supercapacitor electrodes. [Display omitted] • Electrospun porous carbon nanofibers (CPP–CNF) were prepared from cuttlefish ink. • CPP-CNF features hierarchical pores and hollow channels. • CPP-CNF is mechanically flexible with superior capacitive performance. • The flexible supercapacitor achieves high energy density and cycling stability. [ABSTRACT FROM AUTHOR]

Although high-rate, long-cycle energy storage devices play a crucial role in the field of energy storage, they are relatively under-reported. This work reports the preparation of fibrous porous carbons ultra-high specific surface area of 3384 m2g-1 derived from medical waste degreased cotto. As electrode material for supercapacitors, the resulted porous carbons demonstrate an ultra-high specific capacitance of 505.5 F g−1 at 0.5 A g−1 in a three-electrode system with 6 M KOH as electrolyte. Assembled symmetric supercapacitors show a specific capacitance of 403.84 F g−1 at 0.5 A g−1 and 294.95 F g−1 at 20 A g−1, with a capacity retention rate of 73.62 %, impressively retaining 82.66 % of the capacity after 300000 cycles at 10 A g−1. The average capacity loss is minimal, at 0.000557 % per cycle. The as-assembled zinc-ion hybrid capacitors (ZIHCs) demonstrate a high energy density of 69.33 Wh kg−1 at 2400 W kg−1 in 2 M ZnSO 4 electrolyte and retain 99.3 % capacity after 120000 cycles at 7 A g−1, suggesting the excellent long cycling stability. These outstanding performances demonstrate a promising solution for recycling and utilizing medical waste-degreased cotton in energy storage devices, also addressing the research gap in high-rate, long-cycle applications. • Medical decreased waste cotton is efficiently transformed into porous carbons. • Porous carbons exhibit an ultra-high specific surface area of 3384 m2g-1. • As For supercapacitors (SCs), it exhibits high capacitance of 505.5 F g−1. • After 300000 cycles, SCs maintain a high-capacity retention rate of 82.66 %. • After 120000 cycles, the ZIHCs maintain a high-capacity retention rate of 99.3 %. [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]

[Display omitted] • Self-O-doped Alpinia galanga stem-based carbon nanofiber succesfully synthesis. • The hierarchical porous carbon exhibit high specific surface area of 1065.58 m2/g. • The porous carbon was performed in solid-free binder form. • In 2-electrode system, supercapacitor possessed specific capacitance of 226F g−1. In this study, activated carbon with hierarchical pores and a nanofiber structure doped with oxygen was prepared using a pure biomass-based sustainable strategy involving integrated chemical impregnation and pyrolysis. Alpinia galangal stem was chosen as it functions as fast conductive network with abundant electrochemical active sites for high-grade electrode materials. The optimal precursor exhibited self-doping of oxygen ranging from 6.15 to 15.69 % with 1065.58 m2/g, which contributed to the redox reaction of the electrode material. When tested in a 2-electrode system, the porous carbon nanofibers showed a high specific capacitance of 226F g−1 at 1 A g−1 in 1 M H 2 SO 4 electrolyte, producing an energy density of 9.3483 Wh kg−1 with a coulombic efficiency of 89.01 %. The results showed that oxygen-doped hierarchical porous carbon nanofibers produced from Alpinia galangal stem biomass and designed to be solid-free of binders are highly promising as high-quality electrode materials that can improve sustainable supercapacitor performance. [ABSTRACT FROM AUTHOR]

Herein, a kind of hydroxyl and sulfonyl-containing diamine 2,2-bis[4-(3-hydroxy-4-aminophenoxy)phenyl]sulfone (BHAPS) was first synthesized and polymerized with pyromellitic dianhydride (PMDA) to obtain poly(amic acid) (PAA) solution. Then, the PAA nanofibers were fabricated by electrospinning technology, which were further thermally treated at 300 °C for imidization, 450 °C for rearrangement and a certain final temperature for carbonization to obtain carbon nanofibers (CNFs). The PAA concentration, carbonization temperature and thermal rearrangement time were separately optimized, and the HPI-CNF-20-2-800 exhibited better electrochemical properties. Next, the HPI-CNF-20-2-800 was chemically activated with KOH to enhance specific surface area. The preferred A-HPI–CNF–1/3 demonstrated a specific capacitance maximum of 335.0 F g−1 at 0.5 A g−1, with a 73 % capacitance retention at 10 A g−1. Furthermore , the SC device was symmetrically assembled with self-supporting A-HPI–CNF–1/3 membranes, which showed a maximum energy density of 10.42 Wh kg−1 at a power density of 250.0 W kg−1. In addition, the capacitance retention rate of the SC reached 99.94 % even after 50,000 charge/discharge cycles at a current density of 1 A g−1. Thus, this work reports a new precursor to prepare N, O, S co-doped active CNFs with better electrochemical performance, which will provide a reference for the preparation of co-doped self-supporting SC electrodes. • A new kind of diamine monomer containing hydroxyl and sulfonyl was synthesized. • The N, O, S co-doped activated carbon nanofibers were prepared. • The capacitive performance of self-supporting electrode was effectively boosted. [ABSTRACT FROM AUTHOR]

[Display omitted] • PVP/ZIF-7/PAN nanofibers carbonized at 900 °C yielded flexible ZnO P /C. • A capacitance of 382.5 mF cm−2 was obtained at a current density of 1 mA cm−2. • ZnO P /C demonstrated a capacitance retention of ∼ 101 % over 10,000 cycles. • ZnO P /C delivered an energy density of 49 μWh cm−2 at a power density of 2 mW cm−2. This study investigates the carbonization of electrospun fibers derived from zeolitic imidazolate framework (ZIF)-7/polyacrylonitrile solutions containing urea or polyvinylpyrrolidone (PVP). The carbonization yields highly flexible composites comprising nitrogen-doped carbon nanofibers and ZnO. Notably, using PVP as a nitrogen source generates a composite exhibiting excellent electrochemical performance. Specifically, it delivers a high capacitance of 382.5 mF cm−2 at a current density of 1 mA cm−2. Furthermore, this composite demonstrates capacitance retentions of approximately 101 % and 80 % after 10,000 cycles and a 90° bending test, respectively. The charge-storage capability of the PVP-based ZnO P /C composite surpasses that obtained without PVP by 1.4 times. Additionally, a composite fiber mat of ZnO P /C obtained via one-step electrospinning exhibits exceptional electrical conductivity and an energy density of 49 μWh cm−2 at a power density of 2 mW cm−2. These findings highlight the potential of this material as an electrode for supercapacitors. [ABSTRACT FROM AUTHOR]

It is difficult for green sustainable lignin-based materials to simultaneously obtain efficient electromagnetic wave absorption (EMWA) and supercapacitive energy storage (SCES), which has not yet been reported. Herein, the light-weight lignin-based carbon nanofibers (LCNFs) with proper pore size, well graphitization degree, and heteroatom doping were tailored through electrospinning and carbonization processes. Interestingly, the graphitization degree and porous structure of LCNFs could be easily adjusted by changing the activating temperature, and the higher conductivity was achieved for preparing LCNFs at higher activating temperature due to the differences in the crystal size and activating degree of LCNFs. As a result, in the field of EMWA, the LCNFs-950 exhibited the minimum reflection loss (RL) value was −41.4 dB and the absorbing frequency was 9.05 GHz at 2.5 mm thickness, which meant this absorbent could absorb and/or dissipate more than 99.9% of incident electromagnetic wave (EMW). Furthermore, the LCNFs-950 also exhibited excellent SCES ability. In two-electrode system, the optimal LCNFs-950 symmetric supercapacitor specific capacitance reached 139.4 F/g at a current density of 0.5 A/g, meanwhile, the energy density was 41.4 Wh/kg at a power density of 3500 W/Kg. These multifunctional features of LCNFs will be highly promising for the next-generation environmental remediating materials. [Display omitted] • Increasing the activating temperature was an effective strategy for preparing renewable and low-cost multifunction LCNFs. • Multifunction LCNFs in both electromagnetic wave absorption and electrochemical energy storage were fabricated. • The minimum reflection loss was −41.4 dB and the absorbing frequency was 9.05 GHz at 2.5 mm thickness. • The specific capacitance, energy density and power density were up to 139.4 F/g, 41.4 Wh/kg and 3500 W/Kg, respectively. [ABSTRACT FROM AUTHOR]

Prussian blue analogs, as a pseudo-capacitor electrode materials hold great potential due to their unique framework structure, excellent electrochemical activity and high specific capacity. Herein, a versatile method for the growth of series of metal hexacyanoferrates (MHCF) on carbon nanofiber with high conductivity and flexibility was proposed. By controlling the releasing rate of metal ions through acid modulation of solution, the series of MHCF nanocubes were successfully embedded on the carbon nanofibers with super stability. Different MHCF presented various loading density. Among the MHCFs, nickel hexacyanoferrate (NiHCF) is the most easily formed with high density and uniform distribution. The obtained self-supporting NiHCF@CNF, as a representative electrode, exhibited high specific capacitance (507 F g−1, 1 A g−1) and remarkable rate performance (67% retention at 10 A g−1). Moreover, the NiHCF@CNF-based hybrid supercapacitor cell delivered a high energy density of 60 Wh kg−1 at the power density of 810 W kg−1. Meanwhile, the capacitor showed extremely high stability due to tight anchoring of NiHCF on CNFs. This work provides a simple and versatile method to produce self-supporting MHCF@CNF composites for constructing high performance supercapacitor. [Display omitted] • A versatile method to produce various MHCF@CNF is demonstrated. • The self-supporting MHCF@CNF are extremely stable with excellent flexibility. • The MHCFs particles with small size and uniform distribution promote the charge transfer. • A super high specific capacitance of 507 F g−1 (1 A g−1) is achieved on NiHCF@CNF. • NiHCF@CNF//PCNF delivers energy density of 60 Wh kg−1 at a power density of 810 W kg−1 [ABSTRACT FROM AUTHOR]

Recently, the high-value utilization of food wastes has attracted great interest in sustainable development. Focusing on the major application of electrochemical energy storage (ECES), light-weight lignin-based carbon nanofibers (LCNFs) were controllably fabricated as supercapacitors from melon seed shells (MSS) and peanut shells (PS) through electrospinning and carbonizing processes. As a result, the optimal specific capacitance of 533.7 F/g in three-electrode system, energy density of 69.7 Wh/kg and power density of 780 W/Kg in two-electrode system were achieved. Surprisingly, the LCNFs also presented a satisfied electromagnetic absorption property: The minimum reflection loss (RL) value reached −37.2 dB at an absorbing frequency of 7.98 GHz with an effective frequency (RL < 10 dB) of 2.24 GHz (6.88 to 9.12 GHz) at a thickness of 3.0 mm. These features make the multifunctional LCNFs highly attractive for light-weight supercapacitor electrodes and electromagnetic wave absorbers applications. [Display omitted] [ABSTRACT FROM AUTHOR]

The hydroxyl-functionalized poly (amic acid) (PAA) is first synthesized from 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (6FAP) and 4,4-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), and electrospun into nanofibers. Then, the PAA nanofibers are thermally imidized at 300 °C and rearranged at 450 °C, followed by an ultimate carbonization to obtain hydroxyl-functionalized polyimide (HPI) based carbon nanofibers (CNFs). When the PAA concentration and carbonization temperature are respectively optimized as 28 % and 800 °C, the obtained CNF specimen HPI(6FAP-6FDA)-28-800 exhibits a better electrochemical performance, with a specific capacitance of 226.3 F g−1 at 0.5 A g−1. Subsequently, the HPI(6FAP-6FDA)-28-800 is subjected to KOH activation treatment. When the CNF/KOH mass ratio is 1/3, the activated sample CNF(6FAP-6FDA)-1/3 displays a maximum specific capacitance of 354.0 F g−1, coupled with a high rate-performance of 75 % (10 A g−1). Furthermore, a button-type supercapacitor (SC) assembled by two pieces of self-supporting CNF(6FAP-6FDA)-1/3 membrane attains an energy density maximum of 11.39 W h kg−1 at a power density of 250 W kg−1. Under 10,000 cycles of charging-discharging, the SC demonstrates an outstanding working stability. In brief, this study reports a novel polymer precursor for the preparation of N, O co-doped active CNFs, and provides an insight into the relationship between the chemical structure, microstructure and electrochemical performance for self-supporting SC electrodes. • The N, O co-doped activated carbon nanofibers were prepared. • The o -hydroxyl polyimides containing rich –C(CF 3) 2 - structures were used as precursors. • The self-supporting electrodes exhibited superior capacitive performances. [ABSTRACT FROM AUTHOR]

MXene-integrated N-doped cavity-interconnected porous carbon nanofibers flexible film with excellent energy storage performance was prepared by a non-pre-oxidation synthesis strategy combining electrospinning and metal–organic framework derivatization. [Display omitted] • The flexible carbon film is constructed by MXene-integrated N-doped cavity-interconnected porous carbon nanofibers. • The non-preoxidation synthesis strategy overcomes the MXene oxidation and active site loss caused by the flexible carbon film during the preparation process. • The flexible carbon film exhibits a high energy density of 26.2 Wh kg−1 at 500 W kg−1 and good capacitance retention (96.3 %) after 10,000 charge–discharge cycles. • This study develops an effective general strategy for the preparation of embedded carbon nanofiber flexible film. Although the flexible carbon film integrated with MXene has been proven to be a new generation of supercapacitor material with good energy storage prospects, the MXene oxidation and the lack of active sites during the preparation of the carbon film can lead to irreversible capacity loss. Herein, a flexible carbon film constructed by MXene-integrated N-doped cavity-interconnected porous carbon nanofibers was prepared by a non-pre-oxidation synthesis strategy combining electrospinning and metal–organic framework derivatization. This flexible carbon film overcomes the oxidation problem of MXene during the stabilization of polyacrylonitrile, and the derived porous structure of cavity interconnection exposes more active sites. Due to its unique structural characteristics and ideal chemical composition, this independent flexible carbon film exhibits significantly enhanced electrochemical performance as an electrode material for supercapacitors. It exhibits an energy density of 26.2 Wh kg−1 at a power density of 500 W kg−1, and a capacitance retention rate of 96.3 % after 10,000 charge–discharge cycles. This study provides a unique strategy for the preparation of high-performance flexible carbon films, and this technology can also be extended to other integrated CNF composites for the design of high-performance supercapacitor electrodes. [ABSTRACT FROM AUTHOR]

Developing a simple and effective method for optimizing lignin structure is a key challenge for the application of biomass-based carbon nanofibers in energy storage and moisture-enabled electricity generation fields. In this work, an effective strategy is designed to prepare novel biomass-based carbon nanofibers. Carbon quantum dots (CQDs) are introduced as functional components into biomass-based carbon nanofibers to optimize the inherent structural defects of lignin. The introduction of CQDs effectively reduces the interaction between lignin macromolecules, thereby increasing the flexibility of lignin macromolecule chain segments. The obtained biomass-based carbon nanofibers exhibit excellent microfiber morphologies and a high degree of graphitization. The specific capacitance and energy density for biomass-based carbon nanofibers as the energy storage device reach 294.4 F/g and 28.3 W h/kg, respectively. Furthermore, the biomass-based moist-electric generator shows high power generation efficiency, the output voltage and output current of a single device reach 0.75 V and 1.8 μA, respectively. Notably, as the number of biomass-based moist-electric generators in series or parallel increases, the overall output efficiency of the device system has a linear relationship, which means that a sufficient number of biomass-based moist-electric generator devices can meet the power supply requirements of larger power systems. This work puts forward a promising strategy to prepare low-consumption, high-performance, and environmentally friendly biomass-based carbon nanofibers for the supercapacitors and moist-electric generators. [Display omitted] • The introduction of CQDs optimize the inherent structural defects of lignin. • CQDs improve the fiber morphology and graphitization degree of carbon nanofibers. • Biomass-based carbon nanofibers exhibit excellent electrochemical performance. • Biomass-based carbon nanofibers can be used for a novel moist-electric generator. • The preparation of novel biomass-based carbon nanofibers was proposed. [ABSTRACT FROM AUTHOR]

Manifold graphene-based supercapacitor (GSC) electrodes have been extensively studied recently. Numerous studies have aimed to improve the performance of GSCs by amending the surface using various treatments or by incorporating diverse materials. However, few studies have been conducted on the treatments for the back electrodes which support the active material in the GSCs. Herein, the activation of carbon nanofibers (CNFs) back electrodes was achieved through simple thermal activation using potassium hydroxide (KOH) as an activating agent to enhance the electrochemical performance of GSC electrodes. The optimized sample exhibited a specific capacitance (C sp) of 210 F/g at 100 mV/s without adversely affecting the self-discharge behavior of the electrodes. Compared to the reference electrodes formed on the nonactivated CNFs, the C sp at high rate operations of the GSC electrodes was markedly increased by 1.6 times. Morphological, elemental, and electrochemical analyses were conducted to study the effects of KOH activation on the performance enhancement of GSC electrodes. Our results present a novel research approach for enhancing GSC performance. [Display omitted] • KOH thermal activation for carbon nanofiber back electrodes was conducted. • An optimum temperature for the activation was found to be 800 °C. • The activation increased the specific capacitance for graphene supercapacitors. • The self-discharging did not worsen, indicating the practicality of this discovery. [ABSTRACT FROM AUTHOR]

[Display omitted] • The NB-PCNF and MnO 2 /Co 3 O 4 /NB-PCNF were successfully fabricated via needleless electrospinning. • The co-doping of multiple non-metallic atoms enhances the electrochemical capability of carbon nanofibers. • The heterogeneous structure in MnO 2 /Co 3 O 4 /NB-PCNF can effectively improve the electrical conductivity. • A flexible asymmetric solid-state supercapacitor (FASS-SC) exhibits excellent electrochemical performance. Rational design of an electrode material with high flexibility and electrochemical performance is the key to wearable energy storage devices. Herein, a facile and productive needleless electrospinning method was introduced to prepare self-supported and flexible nanofibrous electrode materials for asymmetric capacitor. The MnO 2 nanoclusters and ZIF67-derived Co 3 O 4 nano-sheets were sequentially deposited on the surface of N, B-doped carbon nanofibers (hetero-junction MnO 2 /Co 3 O 4 /NB-PCNF). Attributing to the constructed multi-pathway for redox reactions on electrode, the specific capacitance of NB-PCNF and MnO 2 /Co 3 O 4 /NB-PCNF can reach up to 204.2F/g and 141.43F/g at a small current density of 0.1 A/g, respectively. In long-term cycling tests, the electrode materials exhibited excellent cycling stability and good rate capability. The electrodes were assembled with Potassium-ion hydrogel electrolyte to form a flexible asymmetric solid-state supercapacitor (FASS-SC). FASS-SC can reach a voltage window of 1.6 V. It provided 28.2 W h/kg at an energy density of 600 W/kg and a specific capacitance retention of 94.18 % after 10,000 cycles. The FASS-SC offers new research ideas for future flexible devices and wearable technologies. [ABSTRACT FROM AUTHOR]

The increasing commercialization of flexible electronic products has sparked a rising interest in flexible wearable energy storage devices. Supercapacitors are positioned as one of the systems with the most potential due to their distinctive advantages: high power density, rapid charge and discharge rates, and long cycle life. However, electrode materials face challenges in providing excellent mechanical strength while ensuring sufficient energy density. This study presents a method for constructing a flexible composite electrode material with high capacitance and mechanical performance by electrochemically depositing high-quality manganese dioxide (MnO 2) onto the surface of a nanocellulose (CNF) and carbon nanotube (CNT) conductive film. In this electrode material, the CNF/CNT composite film serves as a flexible conductive substrate, offering excellent mechanical properties (modulus of 3.3 GPa), conductivity (55 S/cm), and numerous active sites. Furthermore, at the interface between MnO 2 and the CNF/CNT substrate, C-O-Mn bonds are formed, promoting a tight connection between the composite materials. The assembled symmetric flexible supercapacitor (FSC) demonstrates impressive performance, with an areal specific capacitance of 934 mF/cm2, an energy density of 43.10 Wh/kg, a power density of 166.67 W/kg and a long cycle life (85 % Capacitance retention after 10,000 cycles), suggesting that they hold promise for FSC applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Nowadays, great effort has been devoted to designing biomass-derived nanoscale carbon fibers with controllable fibrous morphology, high conductivity, big specific surface area and multifunctional characteristics. Herein, a green and renewable strategy is performed to prepare the biomass-based nanoscale carbon fibers for fire warning sensor, supercapacitor and moist-electric generator. This preparation strategy thoroughly gets over the dependence of petroleum-based polymeride, and effectually improves the energy storage capacity, sensing sensitivity, humidity power generation efficiency of the obtaining biomass-based carbon nanofibers. Without the introduction of any active components or pseudocapacitive materials, the specific capacitance and energy density for biomass-based nanoscale carbon fibers achieve 143.58 F/g and 19.9 Wh/kg, severally. The biomass-based fire sensor displays excellent fire resistance, stability, and flame sensitivity with a response time of 2 s. Furthermore, the biomass-based moist-electric generator shows high power generation efficiency. The output voltage and current of five series connected and parallel-connected biomass-based moist-electric generators reaches 4.30 V and 43 μA, respectively. Notably, as the number of biomass-based moist-electric generators in series or parallel increases, the overall output voltage and current of the device system have a linear relationship. This work proposes a self-powered fire prediction system based on nanoscale carbon fibers that integrates sensing, power generation, and energy storage functions. [ABSTRACT FROM AUTHOR]

Lignin is recommended to a tempting alternative precursor of petroleum for fabricating carbon nanofibers (CNFs) due to its high carbon content, low-cost and renewable resources. However, the property of lignin-based carbon nanofibers (LCNFs) is inferior owing to the heterogeneity and 3D-network structure of lignin, which hinders its application in supercapacitors. The latest developments in fractionation technology have shown great potential for overcoming the aforementioned shortcomings. However, most of fractionation methods mainly rely on expensive chemicals and complex reaction process, such as enzymes, multiple solvents, membranes, and dialysis tubes. Herein, we proposed a controllable and effective strategy to fractionate lignin by only changing the ratio of ethanol/water (V/V) as mixture solvent. This gradient extraction method effectively removed the part of lignin with small molecular and branching structure, thus selectively getting the fractionated lignin with high molecular weight, narrow polydispersity index, and good linear structure. Fortunately, when the ratio of ethanol/water was 6:4, the corresponding LCNFs (LCNFs-L60) was obtained with large specific surface area, independent filamentous morphology networks and excellent electrochemical property. Its specific capacitance was up to 405.8 F/g. This way features controllable and sustainable for preparing high-quality LCNFs supercapacitors. [Display omitted] • The high linear structure of sugarcane bagasse lignin was obtained through different solvent ratio fractionation way. • The heterogeneity of fractionated lignin was decreased by screening large molecular weight sugarcane bagasse lignin. • L60 with more β-O-4 structural units and smaller homogeneity was more suitable for fabricating high performance LCNFs. • The LCNFs-L60 showed independent morphology, uniform diameter, large surface area and excellent power storage capacity. • This method was an effective strategy for preparing low-cost and high-quality LCNFs supercapacitors electrodes. [ABSTRACT FROM AUTHOR]

Lithium-ion supercapacitors (LICs) have received widespread interests because of their high power density, high energy and long life characteristics. The electrodes for LICs play a significant role in enhancing their performance. Therefore, it is of great significance to design and develop high-performance electrode materials for LIC through integrating various materials to make up for each other's disadvantages. Herein, a bimetallic composite nanomaterial with hierarchical structures (CoSn X /CNFM) and a porous carbon nanomaterial with high specific surface area (PCNFM) were obtained through combining electrospinning, anion exchange or alkali etching and subsequent high-temperature carbonization, respectively. The LIC assembled with the pre-lithiated CoSn X /CNFM as anode and the PCNFM as cathode exhibited a high energy density of 41.48 Wh/kg at a power density of 1500 W/kg, and still had an energy density of 28.13 Wh/kg at a high power density of 7500 W/kg, illustrating its high power density and high energy density. Thus, this paper proposes an effective method for designing and manufacturing high-performance LICs. • Nanofibers with uniformly distributed ZIF-67 NPs were prepared in batches by EMAI. • Hierarchical-structured CoSn X /CNFM was prepared by anion exchange and carbonization. • PCNFM with high specific surface area was prepared by etching and carbonization. • A LIC with pre-lithiated CoSn X /CNFM as anode and PCNFM as cathode was assembled. • The assembled LIC had high power density and high energy density. [ABSTRACT FROM AUTHOR]

In order to enhance the electrochemical efficiency of supercapacitors, novel active electrode materials are being developed. This study provides a unique method to synthesize an integrated structure consisting of a nickel-cobalt metal-organic framework (NiCo-MOF) on functionalized carbon nanofiber (f-CNF) utilizing a single-step solvothermal method. Physicochemical characterization confirmed the successful synthesis of the integrated system of NiCo-MOF@f-CNF. This novel structure has the potential to significantly improve the electrochemical properties of the initially prepared material for use in supercapacitors. The synthesized electrode has a higher specific capacitance/capacity value of 788 F g−1 (315.2 C g−1) at 1 A g−1 and high cycling stability. The developed hybrid device exhibited a promising specific energy of 8.6 Wh kg−1 and a high specific power of 1147 W kg−1, demonstrating potential for practical applications. The current study suggests that the proposed material can be a viable electrode for high-efficiency supercapacitors. • An integrated structure of NiCo-MOF@f-CNF nanocomposite was prepared and used as an efficient electrode in supercapacitors. • Electrical conductivity, mechanical properties, and surface accessibility were enhanced when f-CNF joined NiCo-MOF. • NiCo-MOF@f-CNF hierarchical structure exhibits a specific capacitance of 788 F g−1 at a current density of 1 A g−1. • NiCo-MOF@f-CNF//AC hybrid supercapacitor shows a specific energy of 8.6 Wh kg−1 at a specific power of 1.147 kW kg−1. [ABSTRACT FROM AUTHOR]

Iron selenide (FeSe 2), a p-type narrow band gap (1.0 eV) semiconductor, has been considered as a potential electrode material for electrochemical energy storage owing to its many benefits, including quick electron transfer, excellent electrical conductivity and exceptional theoretical specific capacity. Nevertheless, the volumetric expansion, agglomeration, low ion-diffusion capacity and other inadequacies in the process of discharging and charging. Therefore, FeSe 2 is far short of high initial coulomb efficiency, long-cycle stability, and excellent rate performance. The greatest obstacle to the practical use of energy storage systems is these drawbacks. Herein, the electrospinning and a thermally-induced selenization route are adopted to encapsulate the FeSe 2 hollow nanospheres into the intertwined Se, N co-doped carbon nanofibers (Se, N-FeSe 2 CNFs). Density functional theory calculation delivers that Se, N-FeSe 2 CNFs nanocomposite presents extremely low bandgap and high density of states at the Femi level, demonstrating significantly increased conductivity. When assembling into the all-solid-state symmetric supercapacitors (ASSSCs), the Se, N-FeSe 2 CNFs ASSSCs provide a remarkable specific capacity of 330.2 F g−1 and maintain 92.0% after 5000 cycles at 2 A g−1. Meanwhile, the resistance of charge transfer decreases from 0.73 Ω (FeSe 2) to 0.28 Ω (Se, N-FeSe 2 CNFs). Moreover, the Se, N-FeSe 2 CNFs ASSSCs deliver 128.6 Wh kg−1 (energy density) at about 800 W kg−1 (power density). Additionally, the Se, N-FeSe 2 CNFs anodes also have outstanding reversible capacity (549.5 mAh g−1 at 0.1 A g−1) and stability of long-circulation (481.3 mAh g−1 after 100 circles and 480.9 mAh g−1 after 200 circles at 0.1 A g−1) for sodium-ion batteries (SIBs). The superb property of energy storage can be due to the encapsulated structure that can maintain the integrity of structures for electrodes during electrochemical reactions and the Se, N heteroatoms doped CNFs that can conducive to ions/charges transport and storage. The designed encapsulated structure and synthesis approach have broad application prospects in electrochemical energy storage. [Display omitted] • The hollow FeSe 2 nanospheres are encapsulated in the N,Se co-doped carbon nanofibers. • The encapsulated structure can availably ameliorate the volume effect of FeSe 2 and raise the stability of electrodes. • The Se, N-FeSe 2 CNFs electrodes show outstanding electrochemical properties in supercapacitors and sodium-ion batteries. • According to density functional (DFT), the Se, N-FeSe 2 CNFs have narrow band structure and high density of states. [ABSTRACT FROM AUTHOR]

• A facile method was reported by us to sustainably obtain 3D and defective nanocarbon from waste RS residue. • The key role of bacterial played in the formation of RS residue with unque structure and composition was revealed. • The underlying pyrolysis mechanism of RS residue is explored. • The obtained bio-char was demonstrated as a promising candidate for supercapacitor. Defective carbon nanomaterials with three-dimensional (3D) structure are showing great potential for advanced electrochemical storage and conversion devices, but its application is restricted by the synthesis, which is usually involved with complicate and energy-intensive processes. Herein, pyrolysis of rice straw (RS) residue, of which is collected from the bacterial assisted hydrolysis, is proposed by us here, and the obtained bio-char is defective with 3D structure and rich in oxygen-containing functional groups. Compared to the pristine one, specific surface area of the representative RS carbon (RSC2) was increased from 428.8 to 1131.7 m2 g−1. The assembled supercapacitor with RSC2 showed a high specific capacitance of 331F g−1 at a charge–discharge current density of 0.5 A g−1, and a capacity retention of 97.6% was maintained at 5 A g−1 even after 10,000 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • ● A dual network organohydrogel based asymmetric supercapacitor exhibits temperature tolerance from −20 to 80 °C. • ● High operation voltage of 1.7 V and a high energy density of 51.1Wh kg−1 is obtained with the supercapacitor. • ● Over the repeated cycles of heating and cooling between –20 and 80 °C, 94% of the initial capacitance is retained. • ● The supercapacitor exhibits mechanical stability over bending regardless of the temperature. It is highly desirable for supercapacitors to achieve mechanical flexibility and temperature tolerance, as well as high energy density, to fully utilize their superior characteristics of high-power density and long cycle stability to realize their potential as practical wearable energy storage devices. We devise a novel strategy to fabricate a flexible asymmetric supercapacitor based on dual network organohydrogel, exhibiting high energy density and electrochemical stability over a wide temperature range spanning 100 ℃. A three-dimensional core–shell NiCo 2 O 4 @MnO 2 nanostructure is selected as the positive electrode to supply multiple ion diffusion channels through its mesoporous structure, and nano structured N-doped carbon nanofibers as the negative electrode to increase the contact area with electrolyte, and 6 M KOH based organohydrogel as electrolyte. The resulting supercapacitor exhibits high electrochemical performance including a high operation voltage of 1.7 V and high energy density of 51.1 Wh kg−1 at a power density of 850 W kg−1 and is stable over temperature changes between –20 and 80 ℃. This work demonstrates a high-performance supercapacitor designed with 3D asymmetric electrodes and a dual network organohydrogel, suitable as a practical energy storage device, requiring mechanical stability and stability against temperature change. [ABSTRACT FROM AUTHOR]

SnS is an ideal material for supercapacitors because of its unique layered structure and excellent electrochemical performance, but the research of SnS based electrode materials of flexible self-supporting supercapacitors has been rarely exploited. In this study, microsphere like Co doped SnS grown on carbon nanofibers (Co-SnS@CNF) was prepared by electrospinning, hydrothermal method and annealing treatment. Co-SnS@CNF has great flexibility, high specific capacitance, excellent rate performance and cycle stability. Specifically, the specific capacitance is 750 F g−1 at the current density of 1 A g−1. The special microsphere structure with more electrochemical active sites and lower resistance of ion and charge transfer by Co doping are responsible for the superior electrochemical performances. Furthermore, when assembled Co-SnS@CNF as the symmetrical supercapacitor device, the energy density of 20.89 Wh Kg−1 and the power density of 376 W Kg−1 are achieved at the current density of 1 A g−1, while showing ultra-high cycle stability. Therefore, the Co-SnS@CNF offers excellent application potential for flexible self-supporting supercapacitors. • Revealing reasons for the high-performance of the microspherical Co-doped SnS. • The specific capacitance is 750 F g−1 at the current density of 1 A g−1. • The assembled symmetrical device exhibits the ultra-high cycle stability. [ABSTRACT FROM AUTHOR]

Wearable electronic devices using energy device-based smart fibers have brought changes in Internet of Things (IoT) technology paradigms. Since electric power is essential to drive all current electronic devices, a flexible energy device is essential to construct a wearable energy systems. Herein, two different types of the fiber-based energy devices were manufactured using ZIF-67, which can improve catalytic properties. First of all, it was confirmed that ZIF-67 was adsorbed on the electrodes of the solid-state fiber-shaped supercapacitor (SS-FSC) and the catalytic property was enhanced, thereby improving the specific capacitance. Second, it was verified that ZIF-67 was adsorbed on the surface of Pt wire, which is the counter electrode (CE) of the solid-state fiber dye-sensitized solar cell (SS-FDSSC), to improve the catalytic properties, resulting in the improvement of the power conversion efficiency (PCE) of the SS-FDSSCs. The optimized SS-FDSSC demonstrated enhanced electrocatalytic activity, with a PCE of up to 7.03%, which is about 40% greater than that of the pristine Pt wire electrode (5.02%). Therefore, the fiber-based energy devices functionalized with ZIF-67 with excellent catalytic properties and high surface area have been identified as having great potential for producing novel and efficient power sources for wearable electronic devices to be utilized in IoT applications. • Incorporating zeolite imidazole frameworks (ZIF-67) on the electrode of fiber-shaped energy devices. • Excellent electrocatalytic activity of ZIF-67 enhanced electrode. • ZIF-67-integrated Solid-State Fiber-shaped Super Capacitors (SS-FSCs). • ZIF-67-integrated stable Solid-State Fiber-shaped Dye-Sensitized Solar Cells (SS-FDSSCs). • Flexible/wearable energy devices with good stability after repeated bending and washing. [ABSTRACT FROM AUTHOR]

The development of multifunctional composites is a challenging but necessary path for the miniaturization and integration of electronic products. Herein, versatile bimetal hydroxide (NiCo 2 (OH) 6) nanowires coated on TiO 2 modified lignin based carbon nanofibers (CNFs/TiO 2 @NiCo 2 (OH) 6) have been prepared successfully by the method of electrospinning followed by hydrothermal treatment. The loading of NiCo 2 (OH) 6 , the doping of N, and the modification of TiO 2 endow the CNFs/TiO 2 @NiCo 2 (OH) 6 with multifunctional application in energy storage and microwave absorption (MA). The abundant pores and active sites result in an excellent electrochemical performance with a high specific capacitance of 752.47 F g−1 at 1 A g−1. More importantly, the assembled supercapacitor exhibits a maximum energy density of 60.64 Wh kg−1 and a superior stability of 90.2 % even after 4000 cycles at the current density of 10 A g−1. Moreover, considering the unique porous layered-structure as well as eminent electromagnetic matching properties, as-prepared composites display an excellent MA property, which possesses a minimum reflection loss (RL min) of −46.48 dB and a maximum effective absorption bandwidth (EAB, RL < 10 dB) of 2 GHz (covering 47.62 % of X-band frequency). This work simultaneously delivers the potential application in the field of energy storage and MA. [Display omitted] • Bimetal hydroxide nanowires are grown on TiO 2 modified lignin based CNFs. • TiO 2 doping can enhance the MA properties of composites by improving the permittivity. • The doped TiO 2 generates more micro-defects and oxygen vacancies in CNFs. • The proposed design endows the versatile composites with excellent performance. • Providing a promising approach for the high-value utilization of lignin [ABSTRACT FROM AUTHOR]

[Display omitted] • MXene nanosheets incorporated hollow carbon nanofibers (MX/HCFs) are designed. • Flexible and conductive MX/HCFs are used to develop vanadium-doped CoP nanorods as a freestanding positrode for supercapacitors. • MOF-derived Co-CNT@CNF negatrode is prepared by a facile heat treatment method. • V-CoP@MX/HCF and Co-CNT@CNF present specific capacitances of 1896.8F g−1 and 405.5F g−1, respectively, at 1 A g−1. • V-CoP@MX/HCF//Co-CNT@CNF flexible ASC device achieves an energy density of 72.4 Wh kg−1 at a power density of 800.12 W kg−1. Novel architectural electrode materials that are freestanding and exhibit improved electrochemical performances in flexible asymmetric supercapacitors are urgently needed; however, designing these materials is challenging. Herein, a Ti 3 C 2 T X MXene-aligned hollow carbon fiber (MX/HCF) is engineered and vanadium-doped cobalt phosphide nanorod arrays are grown on it (V-CoP@MX/HCF) and applied for supercapacitor positrode. V doping modulates the surface structure and electronic environment of CoP nanorods grown over conductive and flexible MX/HCFs. As expected, the optimized V-CoP@MX/HCF exhibits a better electrochemical performance (1896.8 F g−1) than that of CoP@MX/HCF and CoP@HCF. For the negative electrode, zeolitic imidazolate framework-67 (ZIF-67) grown on electrospun polyacrylonitrile (PAN) fibers is converted to cobalt nanoparticle-encapsulated nitrogen-doped carbon nanotubes at carbon nanofibers (Co-CNT@CNF) by a simple heat treatment without the burden of external catalysts and reducing gases. The as-designed freestanding Co-CNT@CNF delivers a specific capacitance of 405.5 F g−1 with superior cycling stability. A flexible asymmetric supercapacitor (V-CoP@MX/HCF//Co-CNT@CNF) is designed that unveil remarkable electrochemical properties, such as a high energy density of 72.4 Wh kg−1 at 800.12 W kg−1 and good capacitance retention (91.4 %) after 10,000 charge/discharge cycles. Furthermore, the device can maintain a consistent performance regardless of the bending degree. More importantly, this work provides new opportunities to rationally design novel freestanding cathodes and anodes for high-performance flexible asymmetric supercapacitors. [ABSTRACT FROM AUTHOR]

The dramatic development of wearable electronics has led to extensive research into flexible supercapacitors as wearable energy storage devices. The practical application of supercapacitors to wearable electronics requires improved temperature tolerance and high energy density. Herein, we report the fabrication of a high-voltage flexible aqueous supercapacitor featuring high energy density and a wide operating temperature range. This is achieved by the strategy of simultaneously utilizing asymmetric electrodes and water-in-salt gel electrolyte (WISGE). Using NaClO 4 -based WISGE and asymmetric electrodes consisting of Na-inserted MnO 2 and N-doped carbon nanofibers, we obtain excellent electrochemical performance, including a gravimetric capacitance of 97.2 F g−1, energy density of 90 Wh kg−1, power density of 28.1 kW kg−1, operation voltage window of 2.6 V, and capacitance retention of 85.2% over 10,000 charge/discharge cycles. The fabricated flexible supercapacitor is stable under repeated temperature changes between − 20 and 80 °C, regardless of bending deformation. After three cycles of cooling and heating, the initial capacitance at room temperature is 95.1% recovered. This study demonstrates the potential application of our high-performance flexible aqueous supercapacitors to wearable devices, given their resistance to changes in environmental temperature and mechanical deformation. [Display omitted] • Supercapacitor consists of the asymmetric electrode and water-in-salt gel electrolyte. • Supercapacitor exhibits wide voltage window (2.6 V) and temperature range (−20 to 80 ℃). • The initial performance was maintained even after repeated temperature changes. • Performance is stable under repeated bending deformation over wide temperature ranges. [ABSTRACT FROM AUTHOR]

Nowadays, materials that possess high activity and natural oxygen vacancy have garnered significant attention as potential electrode materials for supercapacitors. In this study, we successfully prepared the Hf 6 Ta 2 O 17 (HTO) nanofibres (NFs) with an orthorhombic superlattice structure using the electrospinning technique and sintering process. The characterization results indicate that the HTO NFs synthesized at 750 °C show good micro nanostructures and outstanding electrochemical properties. To enhance its energy storage performance, additional oxygen vacancies (OVs) were introduced through a carbothermal treatment under an Ar atmosphere. Although longer reduction reaction times can produce more OVs, the integration of grain boundaries and the growth of grain size caused by large annealing times may limit its electrochemical performance. Therefore, the HTO NFs treated for 1 h (HTO/C-1) exhibited the maximum C s of 925 F·g−1 at 1 A·g−1 with a larger voltage window of 2.1 V. Furthermore, a symmetric supercapacitor fabricated by two reduced HTO NFs electrodes and 1 M Na 2 SO 4 solution, recorded as r-HTO NFs//r-HTO NFs. The device demonstrated excellent energy density of 73.3 Wh·kg−1 (at power density of 1050 W·kg−1) and a long cycling life (81.8% retained after 5000 cycles). These results suggest that the optimized reduction process can provide appropriate oxygen vacancies in HTO NFs, thereby effectively enhancing its performance. [Display omitted] • The Hf 6 Ta 2 O 17 (HTO) nanofibres (NFs) are synthesized by electrospinning method. • The micro nanostructures and electrochemical property of HTO NFs can be designed by controlling the synthesis temperature. • The carbothermal treatment carried under Ar atmosphere is used to improve the amount of oxygen vacancies of HTO NFs. • The HTO NFs treated of 1 h (HTO/C-1) presents excellent capacitance of 925 F·g−1 at 1 A·g−1. • The r-HTO NFs//r-HTO NFs device shows high energy density of 73.3 Wh·kg−1 at power density of 1050 W·kg−1. [ABSTRACT FROM AUTHOR]

The rapid development of consumer electronics, electric vehicles, and smart meters demands high-performance energy storage devices. By now, supercapacitors are expected to become one of the most promising energy devices for future energy technology. In this work, NiO nanoparticles supported on activated carbon nanofibers (NiO/ACNFs) have been synthesized by atomic layer deposition technique, which is directly used as self-supporting binder-free electrodes for supercapacitors. Scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman results show that NiO nanoparticles (3.1 nm) are uniformly coated on ACNFs. The NiO/ACNFs-600 electrodes demonstrate a specific capacitance of 870 F·g−1 (1 A·g−1) and good rate capability (remain 67% at 10 A·g−1). The asymmetric supercapacitor devices with NiO/ACNFs-600//ACNFs electrodes yield a fairly high energy density of 39.85 Wh·kg−1 at 2000 W·kg−1 and excellent capacitance retention of 87% after 10,000 cycles. The excellent electrochemical capacitance performance for NiO/ACNFs is attributed to the high conductivity and large specific surface area of ACNFs, high capacity, small size, and even dispersion of NiO as well as the synergistic effect between them. These results demonstrate that NiO/ACNFs can serve as excellent electrode materials for high-performance asymmetric supercapacitors. [Display omitted] • NiO is dispersed evenly on lignin-derived ACNFs by ALD for the first time. • The oxygen-containing functional groups of ACNFs provide the active site for the anchoring of NiO. • Combined advantages of porous ACNFs and highly dispersed NiO nanoparticles. • NiO/ACNFs-600 electrode exhibits excellent specific capacitance of 870 F·g−1 (1 A·g−1). • NiO/ACNFs-600//ACNFs device yields outstanding energy density of 39.85 Wh·kg−1 at 2000 W·kg−1. [ABSTRACT FROM AUTHOR]

ZIF derived selenides have become a promising battery-type electrode material, but pure ZIF derived materials tend to agglomerate, averting active sites from full exposure. Herein, a hierarchical Co doped Ni 3 Se 4 on carbon nanofibers modified by ZIF-67 was fabricated by co-electrospinning, calcination and solvothermal synthesis, whose mass ratio of ZIF-67 to PAN and the type of chalcogenides were regulated. Among them, CNF-Co(1:1)@NiSe, with the feature of battery-type materials, displayed the large specific capacitance of 749.27 F g−1 at 0.5 A g−1 and superb rate performance when the current density increased from 0.5 to 10 A g−1, owing to its unique hierarchical structure along with synergistic effect of Co-doped Ni 3 Se 4 , Co-N-C, and CNF. Notably, a solid-state hybrid supercapacitor (CNF-Co(1:1)@NiSe//active carbon) was build, and delivered the maximum energy density of 32.36 Wh kg−1 at 1 A g−1 along with the maximum power density of 7999.99 W kg−1 at 10 A g−1. In addition, the supercapacitor exhibited excellent cycle stability during 5000 cycles and was successfully used for the luminescence of LED, revealing a good application prospect for CNF-Co(1:1)@NiSe. [ABSTRACT FROM AUTHOR]

• Series of Cu x NiCo 2−x O 4 synthesized by Microwave hydrothermal method. • The average grain size is in the range of 30–55 nm. • Highest Specific capacitance, C sp = 250.66 Fg−1 is observed for x = 0.06 sample. • Highest E = 22.22 Whkg−1 and P = 757.80 Wkg−1 were observed for x = 0.06 sample. A series of NiCu x Co 2-x O 4 with x = 0, 0.02, 0.04, 0.06, 0.08 and 0.10 samples were synthesized using microwave hydrothermal method (MH). The structural, microstructural, and spectroscopic characterizations were carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). All the samples are in Cubic phase with space group Fd3m. The samples x ≥ 0.08 shows some impurity phases. The average grain size for all the samples is in the range of 30–55 nm. The specific capacitance (C sp) 250.66 Fg−1, energy density (E) 22.22 Whkg−1 and power density (P) 757.80 Wkg−1 was observed for x = 0.06 with a mass loading of 7 mgcm−2 and in 2 M aqueous KOH electrolyte solution at a current density of 1 Ag−1. Therefore, the Cu doping with x = 0.06 shows good redox activities and hence can be used in electric batteries and supercapacitors. [ABSTRACT FROM AUTHOR]

A facile esterification and electrospinning method is utilized to convert the waste lignin into nitrogen-oxygen co-doped esterified lignin/polyacrylonitrile based carbon nanofibers (E-CNFs). The analysis of FTIR and H1-NMR shows that the esterification reaction occurs between the hydroxyl group and the anhydride group and the ester bond is established in precursor. The lignin after esterification has lower glass transition temperature (Tg), and hence the obtained E-CNFs exhibit inter-fiber bonding structure, higher heteroatom content, and better wettability, rendering an efficient electron transport network and contributing pseudo capacitance. Such unique structure and morphology endow E-CNFs electrode with ultra-high specific capacitance of 320 F g−1 at 1 A g−1 and 200.4 F g−1 at 20 A g−1 with 6 M KOH aqueous as electrolyte, revealing outstanding rate capability. Moreover, the assembled E-CNFs//E-CNFs symmetric supercapacitors using 1 M Na 2 SO 4 aqueous as electrolyte deliver a high coulombic efficiency of 112.5% at the current density 1 A g−1, a remarkable energy density of 17.92 Wh kg−1 at the power density of 800 W kg−1, and excellent cycling stability (∼5.5% loss after 5000 cycles). This inter-fiber bonding structure control strategy provides a perspective and avenue for the further development of high-performance electrode material for supercapacitors applications. High performance supercapacitors are fabricated by carbon nanofibers with inter-fiber bonding structure as electrode materials using a facile esterification and electrospinning method. Image 1 • By change the molecular microstructure to control macroscopic properties. • Building inter-fiber bonding structure to reduce resistance of electrode materials. • Elucidated the mechanism between micromorphology and electrochemical properties. [ABSTRACT FROM AUTHOR]

This work demonstrates hierarchical 3D nitrogen-doped carbon nanotube-carbon fibre (N-CNT@CF) networks obtained via a two-step synthetic technique: electrospinning and chemical vapour deposition (CVD) methods. Scanning Electron Microscopy (SEM) and Transmission Electron Microscope (TEM) reveal randomly entangled networks structure. Raman spectroscopy show structural defects, X-ray Diffraction spectroscopy (XRD) confirm the purity of the materials, while BET analysis show increase in surface area after nitrogen doping. Electrochemistry reveals that nitrogen-doping transforms surface-confined to diffusion-confined energy-storage mechanism (i.e., high power) even at low cycling rate, significantly increasing the specific capacitance of the symmetric device (155 F/g), specific energy (5.5 Whkg−1), specific power (254 W kg−1) and capacitance retention of 93% even after 10,000 cycles at 10 Ag−1. The N-CNT@CF-based symmetric cell exhibits higher f o value (ca. 82 Hz, response time, τ , of 12 ms) than the CNT@CF-based cell (ca. 25.1 Hz, 40 ms). The excellent performance of N-CNT@CF hybrid material is attributed to the Faradaic charge contribution arising from synergistic interaction between the nitrogen-doped carbon nanotubes and carbon nanofibers, high conductivity, high surface area coupled with enough accessible active sites for electrochemical reactions. This work underscores the importance of defect engineering and decoration of the vacant sites by nitrogen for enhanced supercapacitance. Image 1 [ABSTRACT FROM AUTHOR]

The aim of this study is to develop the templateless fabrication of hierarchical porous carbon nanofiber (CNF)/MnO 2 composites (PMnCD) derived from polyacrylonitrile (PAN)/cyclodextrin (CD) and investigate their morphological and electrochemical properties to determine the different capabilities of inclusion complexes (ICs) formed by α-CD, β-CD and γ-CD. Among the three CD phases, the PMnCD(β) composite using β-CD exhibits a hierarchical porous structure with large specific surface area of 499 m2g-1, and total pore volume of 0.32 cm3g-1, which helps with adsorption efficiency and accumulation of hydrated molecules for double-layer formation. In addition, the numerous mesopores and nitrogen functionalities of the PMnCD(β) composite provide fast diffusion channels for electrolyte ions and higher attractive interactions with electrolyte ions through the pseudocapacitive character. As a result, the PMnCD(β) electrode has a high specific capacitance of 228 Fg-1 at 1 mAcm−2, maximum energy density of 25.3–16.0 Whkg−1 in the power density range of 400-10,000 Wkg-1, and excellent cycling stability of more than 94% after 10000 cycles in aqueous solution, thereby offering potential applications for supercapacitors. Image 1 • Hierarchical porous PMnCD is fabricated by electrospinning without a template. • β-CD stabilizes and encapsulates MnCl 2 through the good size match of β-CD and MnCl 2. • PMnCD(β) shows a large specific surface area for accumulation of ions. • Many mesopores and nitrogen groups of PMnCD(β) provide fast ion diffusion. • Hierarchical porous PMnCD(β) is applied to high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

The preparation of electrode materials with superior electrochemical performance and excellent mechanical properties are essential for the fabrication of flexible supercapacitors. However, the compatibility of the porosity and flexibility for the electrode materials remains challenging. Herein, free-standing porous coaxial carbon nanofiber (PCCNF) membranes with large specific surface area (648 m2 g−1) and suitable pore size distribution were fabricated by a facile coaxial electrospinning technique and template method. PCCNF possesses superb capacitance of 261 and 48 F g−1 (1 A g−1) in three-electrode and two-electrode system, respectively, result in remarkable energy density (48.6 ± 3 Wh kg−1) and power density (67.5 ± 1 Wh kg−1). Moreover, supercapacitor devices based on PCCNF show superb flexibility as well as excellent electrochemical and mechanical stability. PCCNF-based high performance supercapacitors may be suitable for flexible electronic energy storage devices. Porous coaxial carbon nanofibers (PCCNF) with large specific surface area, well-balanced pore size distribution, and remarkable flexibility are fabricated by a facile coaxial electrospinning technique and template method. Flexible supercapacitors fabricated with the as-prepared PCCNF display superb electrochemical and mechanical stability. This work provides exciting opportunities for the preparation and application of flexible energy storage devices. Image 1 [ABSTRACT FROM AUTHOR]