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[Display omitted] • 1D skin-core multilayer structure was fabricated by a facile template method. • Bicontinuous electron/ion transport during the charge/discharge process. • The large specific surface area and hollow hierarchical porous structure. • Adjusting active layers or sites can obviously improve the capacitive properties. • The maximum energy density of 8.77 Wh kg−1 at a power density of 0.25 kW kg−1. The fast transport of electrons and ions within electrodes is crucial to the final electrochemical properties. Herein, we have developed a unique ultra-long one-dimensional (1D) skin-core multilayer structure based on electrospun carbon nanofibers mainly through a facile Stöber method combined with resorcinol–formaldehyde resin, which not only achieves bicontinuous electron/ion transport during the charge/discharge process, but also provides large surface area for ion adsorption. Particularly, controlling the number of active layers as well as regulating the active sites in layer both can obviously improve capacitive properties. Benefiting from the synergistic effects of the desirable architecture, such the rational-designed skin-core structural carbon nanofibers as supercapacitor electrode can deliver a high specific capacitance up to 255 F g−1 at 0.5 A g−1, favorable rate capability with 89% capacitance retention of initial capacitance at 8 A g−1, and excellent cycling stability with nearly 93% capacity retention after 10,000 cycles at 2 A g−1. Furthermore, the as-assembled symmetric supercapacitor devices also present a maximum energy density of 8.77 Wh kg−1 at 0.25 kW kg−1 and a maximum power density of 3.70 kW kg−1 at 6.74 Wh kg−1. Such skin-core carbon nanofibers provide an effective strategy to design high-performance supercapacitor electrode for the next-generation energy storage devices. [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]

N/P dual-doped three-dimensional porous carbon was synthesized via nano-CaCO 3 template-assistant carbonization of intumescent flame retardants (IFRs) precursor. [Display omitted] Heteroatom-doped three-dimensional (3D) porous carbons possess great potential as promising electrodes for high-performance supercapacitors. Inspired by the inherent features of intumescent flame retardants (IFRs) with universal availability, rich heteroatoms and easy thermal-carbonization to form porous carbons, herein we proposed a self-assembling and template self-activation strategy to produce N/P dual-doped 3D porous carbons by nano-CaCO 3 template-assistant carbonization of IFRs. The IFRs-derived carbon exhibited large specific surface area, well-balanced hierarchical porosity, high N/P contents and interconnected 3D skeleton. Benefitting from these predominant characteristics on structure and composition, the assembled supercapacitive electrodes exhibited outstanding electrochemical performances. In three-electrode 6 M KOH system, it delivered high specific capacitances of 407 F g−1 at 0.5 A g−1, and good rate capability of 61.2% capacitance retention at 20 A g−1. In two-electrode organic EMIMBF 4 /PC system, its displayed high energy density of 62.8 Wh kg−1 at a power density of 748.4 W kg−1, meanwhile it had excellent cycling stability with 84.7% capacitance retention after 10,000 cycles. To our best knowledge, it is the first example to synthesize porous carbon from IFRs precursor. Thus, the current work paved a novel and low-cost way for the production of high-valued carbon material, and expanded its application for high-performance energy storage devices. [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]

• 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]

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]

We report the microstructure, electrical and electrochemical properties of hybrid nanofibers composed of polyacrylonitrile (PAN)/lignin-derived carbon nanofibers and LaMnO3-based inorganic nanofibers for advanced applications as free-standing and binder-free electrode materials of energy storage devices. For this purpose, hybrid nanofibers are fabricated via dual-electrospinning technique and following heat-treatment at different temperatures of 700–1000 °C for simultaneous carbonization and calcination. The SEM, EDS, and XPS analyses reveal that the carbon content in the hybrid nanofibers increases with increasing the heat-treatment temperature and that La and Mn elements are dispersed uniformly over the hybrid nanofibers. The hybrid nanofibers heat-treated at 900 and 1000 °C have a high electrical conductivity of ~ 0.22 S/cm and ~ 0.35 S/cm, respectively. Accordingly, a symmetric two-electrode supercapacitor based on hybrid nanofibers heat-treated at 1000 °C is characterized to have excellent electrochemical performance such as specific capacitance of ~ 95.2 F/g at 1 A/g, power density of 667 W/kg, energy density of 17.6 Wh/kg, and capacitance retention of ~ 97% after 2000 cycles. The results denote that PAN/lignin and LaMnO3-based hybrid nanofibers can be utilized as self-supporting high-performance electrode materials for advanced energy storage devices. [ABSTRACT FROM AUTHOR]

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

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]

Carbon nanofiber (CNF)‐based supercapacitors have promising applications in the field of energy storage. It is desirable, but remains challenging, to develop CNF electrode materials with large specific surface area (SSA), high specific capacitance (SC), and high power density, as well as excellent cycling stability and high reliability. Herein, acrylonitrile–acrylic acid copolymer P(AN‐co‐AA) was synthesized for the preparation of nitrogen‐doped microporous CNFs. Thermal degradation of the AA segment leads to the formation of micropores that are distributed not only on the CNF surface, but also inside the material. The microporous structure and nitrogen content can be manipulated at the molecular level by adjusting the weight ratio between AN and AA, and the SSA and SC could reach as high as 1099 m2 g−1 and 156 F g−1, respectively. After KOH activation, the activated CNFs have an extremely high SSA of 2117 m2 g−1 and SC of 320 F g−1, which are among the highest values ever reported for electric double‐layer supercapacitors with an alkaline electrolyte. Furthermore, the capacitance retention, which can be maintained at 99 % even after 16 000 cyclic tests, reveals outstanding durability and repeatability. [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]

[Display omitted] • In-situ incorporation of MnO in the CNF matrix using unique two-step carbonization. • MnO dispersed CNFs show high specific capacitance of 246F g−1 at 0.5 A g−1. • High power density of 5000 W kg−1 (8.7 W h kg−1) was achieved with 97.5 % capacitance retention after 10,000 cycles. Manganese oxides have attracted great interest as promising pseudocapacitive materials due to its low cost, variable oxidation states, and high theoretical capacitance. In this work, we report the in-situ synthesis of MnO-dispersed carbon nanofibers (CNFs) using electrospinning and a unique two-step carbonization technique. While the single-step carbonization resulted in mixed Mn x O y forms, however, by employing a suitable and optimized two-step carbonization, we were able to obtain CNFs assimilated with MnO nanoparticles (MnO-CNFs). The synthesized MnO-CNF electrodes achieved a high specific capacitance of 246 F g−1 at 0.5 A g−1 in a three-electrode system. A symmetric supercapacitor device assembled with these electrodes exhibited remarkable electrochemical performance with a maximum power density of 5000 W kg−1, maximum energy density of 14 W h kg−1, and an excellent cycling stability (97.5% retention after 10,000 cycles). The exceptional electrochemical performance of MnO-CNFs makes them promising electrode materials for practical energy storage applications. [ABSTRACT FROM AUTHOR]

A green electrode material with dual conductive networks via electrospinning with carbonization and co-precipitation method is constructed. Nitrogen-based carbon nanofiber network (CCP-N) is used as the inner-conductive, electrochemical-active substrate and flexible skeleton. The Co Ni layered double hydroxide (Co Ni LDH) nanosheets and flower-like nanospheres, which randomly and closely covering the surface of CCP-N, respectively, just as the fungus grow on trunks in nature, is regarded as outer-conductive and active substance collector in order to provide abundant active centers, sufficient reaction interface to advance fast electrolyte ions diffusion and electrons transport. Furthermore, the growth process of Co Ni LDH on CCP-N is observed by controlling growth time and the Co/Ni ratio of the precursor solution. It is found that the optimal Co/Ni ratio was 2:1, while that optimal growth time is 12 h. The specific capacitance of Co Ni LDH@CCP-N electrode reaches 1319.4 F g-1 at 1 A g-1. The assembled asymmetric supercapacitor device (CCP-N @ Co Ni LDH//CCP-N) possesses a high energy density of 48.1 W h kg-1 at power density of 576.8 W kg-1, excellent cycling stability of 82.2% retention after 10,000 cycles. The results clearly indicate the Co Ni LDH@CCP-N materials have enormously potential in energy storage. This work puts forward a novel strategy for the design and fabrication of green and advanced supercapacitors materials with high power density and energy density. [Display omitted] • A dual conductive network is established by electrospinning and co-precipitation. • CCP-N is the inner-conductive and Co Ni LDH nanosheets is the outer-conductive. • The CCP-N @ Co Ni LDH exists multifunctional charge storage principles. • The CCP-N @ Co Ni LDH possesses abundant active sites and high specific surface area. • The CCP-N @ Co Ni LDH//CCP-N delivers excellent energy density and power density. [ABSTRACT FROM AUTHOR]

Carbon nanomaterials such as carbon nanotubes, carbon nanofibers, and graphene are exploited extensively due to their unique electrical, mechanical, and thermal properties and recently investigated for energy storage application (supercapacitor) due to additional high specific surface area and chemical inertness properties. The supercapacitor is an energy storage device which, in addition to long cycle life (one million), can give energy density higher than parallel plate capacitor and power density higher than battery. In this paper, carbon nanomaterials and their composites are reviewed for prospective use as electrodes for supercapacitor. Moreover, different physical and chemical treatments on these nanomaterials which can potentially enhance the capacitance are also reviewed. [ABSTRACT FROM AUTHOR]

• Hierarchical porous carbon (HPC) is obtained with three-dimensional (3D) structure. • The HPC with highly fluffy 3D continuous network is found as an ideal support. • HPC-supported MnO 2 nanofibers composite is achieved as a supercapacitor material. • The as-prepared MnO 2 @HPC composite has 3D interpenetrating network structure. • The MnO 2 @HPC composite presents excellent electrochemical performance. For improving the conductivity of porous carbon and the utilizations of its pore structures, a hierarchical porous carbon (HPC) had been developed with highly fluffy three-dimensional (3D) continuous network structure. Using the HPC as a support, a novel MnO 2 @HPC composite with 3D interpenetrating network structure was prepared as electrode material of supercapacitor via simple hydrothermal method. When the hydrothermal reaction temperature was 100°C, the MnO 2 nanofibers (∼5 nm) were uniformly grown on and within the fluffy 3D porous network of the HPC, forming a composite with interpenetrating network structure. The as-prepared composite (MnO 2 @HPC-100) exhibited the characteristics of both electric double-layer capacitance and pseudo-capacitance, which had a high specific capacity of 368 F g−1 at a current density of 0.5 A g−1 and 186 F g−1 at 10 A g−1 (50.5% retention). In addition, the asymmetric supercapacitor device was assembled with a relatively high energy density of 88.2 Wh Kg−1 at a power density of 162 W Kg−1. The device had a high capacity retention rate of 95% after 10000 cycles, and the coulomb efficiency was stable at 99.7%, showing the excellent stability of the composite. Therefore, the MnO 2 @HPC-100 composite has great application prospects in energy storage. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The fancy carbon nanofibers (CNFs) were prepared via coaxial electrospinning and carbonization. • The CNFs featured hollow and hierarchical porous structure. • The bridging structure formed by the carbon nanotubes (CNTs) endowed the CNFs with outstanding flexibility. • The CNFs decorated with polyaniline showed good electrochemical performance. • The assembled device could successfully power the electronics. Supercapacitors are considered to be the next generation of wearable energy storage devices because of reliable safety, high power density, and long cycle life, but the flexibility and energy density limit their practical applications. Herein, the flexible hollow hierarchical porous carbon nanofibers bridged by carbon nanotubes (HPCNFs@CNTs) are designed and constructed, followed by polyaniline (PANI) decorating to fabricate PANI@HPCNFs@CNTs. The synergistic effect of the hollow structure, hierarchical pores, in-situ nitrogen doping, and the bridging structure endows the HPCNFs@CNTs with a high specific capacitance of 461.0F g−1 (207.4 mF cm−2) while maintaining glorious flexibility under various deformation states. Besides, PANI@HPCNFs@CNTs possesses a high specific capacitance of 629.1F g−1 (405.2 mF cm−2) and remarkable cycle stability with 88.5 % capacitance retention after 5000 charging-discharging cycles. The device assembled by PANI@HPCNFs@CNTs renders an ultra-high energy density of 23.3 Wh kg−1 at a power density of 202.7 W kg−1. Furthermore, the device provides remarkable cycle stability and high-rate capability with a capacity retention of 91.3 % after 5000 cycles at 5 A g−1 and 76.7 % at 10 A g−1, respectively, demonstrating a tremendous potential to construct high-performance flexible energy storage devices. [ABSTRACT FROM AUTHOR]

• Sandwich-structured C/Mn/C with a triple layer were fabricated by electrospinning. • Well-preserved MnO 2 NPs in the interlayer are utilized as electroactive sites. • Hollow core present in the interlayer serves as an excellent conductive network. • Symmetric C/Mn(10)/C electrode showed high specific capacitance and long cycle life. • Asymmetric C/Mn(10)/C offers high energy density in a high potential window. Sandwich-structured carbon nanofiber/MnO 2 /carbon nanofiber composites with a triple layer are fabricated by electrospinning. The optimized sandwich-structured composite electrodes exhibit the maximum specific capacitance of 220 F/g at 1 mA/cm2, a high energy density of 24.63 Wh/kg at a power density of 400 W/kg, and an excellent retention rate of 94% after 10,000 cycles. The stable spatial distribution of MnO 2 nanoparticles between the upper and lower carbon nanofiber webs allowed full use of the well-preserved MnO 2 nanoparticles in the interlayer as electroactive sites, providing better electrochemical performance. Furthermore, the hollow core present in the interlayer serves as an excellent conducting network, providing a short ion diffusion path for both ions and electrons. In addition, the asymmetric supercapacitor shows excellent cycling behavior between 0 and 1.4 V and a large energy density of 44.3 Wh/kg at a power density of 400 W/kg, showing great potential in the development of energy storage devices with high energy density for practical applications. [ABSTRACT FROM AUTHOR]

Nitrogen-enriched carbon nanofibers carried Sn and Zn bimetallic composites with outstanding storage capacity and superior mechanical strength were facilely fabricated by electrospinning technology, amidoximation reaction modified polymer fiber, ion coordination technique introduced Zn2+ and carbonization of composite nanofibers. The introduction of amidoxime groups not only enhanced the coordination ability with Zn2+, but also increased the content of nitrogen element. In addition, due to the different thermal stability of amidoxime groups, the regulation of different types of nitrogen content can be achieved by changing the carbonization temperature, and the influence of nitrogen on the electrochemical performance was explained. At the same time, due to the role of carbothermal reduction, tin in different valence ratios was obtained and its contribution to the energy storage performance of supercapacitors was explored. Benefiting from high nitrogen-enriched level, mutation between Sn2+ and Sn4+ oxidation state and synergistic mechanism of ZnO-SnO x bimetal, the prepared composite had a high specific capacitance of 810.89 F g−1 at a current density of 0.5 A g−1, outstanding cycling stability of 119% over 5000 cycles in 4 M KOH electrolyte. What's more, we conducted a two-electrode test with the energy density of 50 Wh kg−1 at a power density of 374 W kg−1. In consequence, this novel design is believed to have great potential in high energy and power density of energy storage devices in the future. Image 1 • Nitrogen-enriched carbon nanofibers carried Sn and Zn bimetallic composites with outstanding storage capacity and superior mechanical strength were successfully prepared. • The sample showed good results due to the built-in electric field formed between different semiconductors, the introduction of hetero atom N increases the conductivity and the synergy between the bimetals. [ABSTRACT FROM AUTHOR]

The lignin-based multi-channels carbon nanofibers (MCNFs) @ SnO 2 nanocomposites with various microstructures are synthesized via co-electrospinning by regarding Poly (vinyl pyrrolidone) (PVP)–SnCl 2 ·2H 2 O as shell materials and lignin-Poly (methyl methacrylate) (PMMA) at different mass ratios as core materials, followed by heat treatment and acid treatment. The experimental results show that when the mass ration of lignin to PMMA in the core region is 5:5, the obtained nanocomposites possess hierarchical internal channels, porous surface, and high specific surface area. This optimized nanocomposite as supercapacitor electrode shows high specific capacitance of 406 F g−1 at current density of 0.5 A g−1. In addition, the electrode exhibits unexceptionable cycling stability with only 5% capacitance decay over 10 000 cycles at 10 A g−1. Furthermore, the symmetric supercapacitor using the optimized nanocomposites as electrodes possesses remarkable power and energy densities. The superior electrochemical performance of nanocomposites is benefited from the hierarchical structures of MCNFs, faradaic pseudocapacitance of SnO 2 , and pore-forming effect of SnCl 2 ·2H 2 O. The unique hierarchical nanocomposites show great potential in future development of lignin-based low-cost, non-toxic and eco-friendly carbon materials for high-performance energy storage devices. [ABSTRACT FROM AUTHOR]

Carbon nanofibers (CNFs) have been continuously studied as a high performance electrode material due to their versatility in energy storage/conversion systems. The main concern of fabricating CNFs as electrode materials is to endow pristine carbon materials with adequate pore structure and active surface functional groups. Herein, we have fabricated porous hollow carbon nanofibers (PHCNF) with high nitrogen contents (13.4%) via co-axial electrospinning and subsequent phase separation process by using poly(styrene-co-acrylonitrile) (SAN) as core and polyacrylonitrile (PAN)/polyvinylpyrrolidone (PVP) mixture as shell. Simple etching process prior to carbonization has a significant effect on making hierarchical pore structure. Moreover, hollow characteristics allow efficient heat treatment for making high crystalline structure and favorable nitrogen functional group. Such an optimized structural and surface functional properties result in a remarkable supercapacitor performance. The designed structure achieves an energy density of 4.12 Wh kg−1 at power density of 15 kW kg−1, and a 92.33% retention rate in 10,000 charge/discharge cycles. The results offer a new strategy for developing advanced carbon material based electrode for high performance storage devices such as supercapacitors, lithium-ion batteries, and sensors. Porous hollow carbon nanofibers (PHCNFs), which have a textural surface and a high amount of nitrogen species, have been successfully developed via free-standing coaxial electrospinning and phase separation processes. PHCNFs show high specific capacitance and energy density at high power density due to its optimized physicochemical properties. Image 1 [ABSTRACT FROM AUTHOR]