Search

Waste orychophragmus violaceus was used to prepare a novel 3D self‐doped (N/O) porous carbon (OPC). The aim was to expand the application and increase the value of waste orychophragmus violaceus. In order to improve its specific capacitance, composites OPC@MnO2x of OPC and MnO2 were prepared by simple hydrothermal method. In 6 M KOH, specific capacitance obtained by OPC at 1 A g−1 is 268 F g−1, surprisingly, specific capacitance of OPC@MnO232 can be up to 419 F g−1 at 1 A g−1 and its capacitance retention rate is as high as 83.62 % after 10000 cycles (20 A g−1). The energy density of OPC@MnO232//OPC asymmetric supercapacitor in 1 M Na2SO4 can even reach 14.22 Wh kg−1 at 400 W kg−1, besides, it showed good cycling stability after 10000 cycles (20 A g−1), with capacitance retention rate of up to 86.64 %. Finally, the device is tested in an application. Connecting two identical asymmetric supercapacitors in series enables red LED to emit greater than 90 s. Overall, this study confirms that the waste orychophragmus violaceus derived porous carbon can reduce the wastage of waste resource, additionally, the composite material prepared is an electrode material for high‐performance supercapacitors with broad prospects. [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]

Highly graphitic porous carbon was derived from kelp biomass and prepared using KOH as the main activating agent with K2FeO4 as the assisting activated agent for supercapacitor applications. The optimum K2FeO4 mass in the total activating agent and temperature were investigated. The characterization results showed porous sheet carbon with a high specific surface area of 2868 m2 g−1 and a low ID/IG of 0.909. It delivered an excellent specific capacitance of 438 F g−1 at 0.5 A g−1. In addition, the assembled supercapacitor device reached the highest energy density of 19.9 W h kg−1 with a power density of 398 W kg−1. [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]

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]

Thin carbon nanofibers (TCNFs) hanging on branched carbon nanofibers (3D TCNF/CNF) with an N-doping level up to 8.7 at% for high-performance supercapacitors are designed and synthesized. TCNF/CNF shows a 3D hierarchical porous structure, a large surface area, abundant ionic-channels, and a great number of electrochemically active sites by N-doping. Because of the multiple synergistic effects of these features, the supercapacitors (SCs) based on TCNF/CNF show a remarkably excellent electrochemical behavior with a high specific capacitance of 224 F g−1. After 50 000 cycles of charge/discharge, 92% of the initial capacitance value is retained in 1.0 M H2SO4 electrolyte. Moreover, the TCNF/CNF-based SCs show low internal resistance, leading to a high power density with a relatively high energy density. [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]

The N‐doped porous carbon (NPC) /carbon micro‐nanotubes (CMNT) /NixCoyOz nanosheets with rich mesopores and 1.37 wt% nitrogen doping are successfully synthesized by a pyrolysis‐ionization‐precipitation combination process, using coal‐based polyaniline and nickelocene as original materials. Therein, most of the CMNT are upright CMTs and worm‐like curved CNTs, and a few are bamboo‐like tubes or carbon nanofibers. Moreover, many flower‐like aggregates assembled by spinel NiCo2O4 nanosheets are anchored on the surface of the NPC and CMNT. The NPC/CMNT/NixCoyOz exhibits a high specific capacitance and cycling stability, attributed to the large BET specific surface area (485 m2/g), suitable BET average pore size (2.3 nm), good hydrophilicity and wettability, and synergistic effects among three components. The assembled NPC/CMNT/NixCoyOz//AC asymmetric supercapacitor also demonstres a high specific capacitance of 120 F g−1 at a current density of 1 A g−1 and a high energy density of 16.7 Wh kg−1 at a power density of 500 W kg−1. [ABSTRACT FROM AUTHOR]

Herein, this paper reports a facile method to prepare electrospun carbon nanofiber mats (ECNFMs) with high specific surface area and interconnected structure using polyacrylonitrile (PAN) as a precursor and novolac resin (NOC) as a polymer sacrificial pore‐making agent. Without additional treatment, the prepared ECNFMs have a highly porous structure because NOC decomposes in a wider temperature range than most polymer activators. The NOC content in the PAN nanofibers shows important effects on porosity. The BET specific surface area of ECNFMs reaches a maximum of 1468 m2 g−1 when the precursor nanofibers contained 30 wt% NOC (ECNFM‐3) after carbonization at 1000 °C. The supercapacitor device from ECNFM‐3 electrode and all‐solid‐state electrolyte shows excellent cycling durability and high specific capacitance: ≈99.72% capacitance retention after 10 000 charge/discharge cycles and ≈320 mF cm−2 at 0.25 mA cm−2. Furthermore, it shows a large energy density of ≈11.1 μWh cm−2 under the power density of 500 mW m−2. Activation of carbon nanofibers simply by the addition of NOC into precursor nanofibers can offer a handy way to prepare ECNFMs for high‐performance all‐solid‐state supercapacitors and other potential applications. [ABSTRACT FROM AUTHOR]

In view of the problems surrounding the research and application of carbon materials, the process of choosing a carbon source is still not perfect. There are few studies concentrating on the establishment of structure–property relationships based on the choice of carbon source. In this regard, our present work contributes the design of an organic precursor that is expected to allow the controllable construction of the carbon material, thus regulating its functionality. A highly π-conjugated Schiff base moiety with alternating imine groups (C＝N) and benzene rings was incorporated into the main chain of a mesoporous polymer. For comparison, a bisphenol-A-type moiety was employed in the main chain of another mesoporous polymer. Using the mesoporous polymers as organic precursors for porous carbon sources, the formation of mesoporous carbon can be attributed to the presence of the highly π-conjugated Schiff base moiety due to its self-supporting effect and char-forming ability, which are absent in the bisphenol-A-type moiety. However, we are not only concerned with the contribution from the chemical structure of the designed precursor to the controllable construction of mesoporous carbon, but also concerned with its regulation of the electrochemical performance of the resulting material. Through characterization using cyclic voltammetry (CV), galvanostatic charge–discharge profiles, and electrochemical impedance spectroscopy (EIS), this kind of mesoporous carbon has been found to have excellent charge storage and transportation abilities and shows potential for application in the electrodes of electrochemical capacitors. [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]

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]

Honeycomb-like nitrogen-doped carbon/polyaniline (HNC/PANI) composite is prepared by a facile two steps method. The honeycomb-like nitrogen-doped carbon skeleton, with uniform pore sizes and three-dimensionally ordered structure, is obtained via the sacrificial template method and polyaniline is served as the N and C source during this progress. The specific surface area is 1056 m2 g−1, which is much higher than that of the disordered nitrogen-doped carbon (named NDC) and pure PANI. The subsequent polyaniline nanofibers with different concentrations are in-situ polymerization on carbon skeleton. The as-prepared HNC/PANI shows excellent performance of supercapacitors is demonstrated by the electrochemical evaluation, which specific capacitance is as high as 686 F g−1 at 1 A g−1 along with the good rate performance and superior cyclic stability (87.8% after 5000 cycles at 10 A g−1, which is superior to the NDC/PANI and pure PANI electrode). Perhaps this work offers a novel approach to improve the specific capacitance and cycle stability of supercapacitors via the ordered honeycomb-like carbon framework. Unlabelled Image • The honeycomb-like nitrogen-doped carbon/PANI composite is fabricated. • The 3D networks of the interconnected of carbon skeleton shortens the electrolyte ion diffusion paths. • The composite with 3D lawn-like structure reveals excellent electro-chemical properties. [ABSTRACT FROM AUTHOR]

Abstract This paper starts with a review on challenges and need of improved supercapacitor application, which is then followed by advantages of biomass compared with other materials for use in supercapacitor application. The conversion of biomass into carbon nanofiber using different techniques was extensively reviewed for its advantages and limitations. It was revealed that the materials currently used are yet to be fully sustainable or feasible for energy storage application. In contrast, biomass represents a widely available and sustainable material to be converted into carbon nanofiber for energy storage application. Different techniques were employed for carbon nanofiber production to achieve different objectives, comprising high product yield, feasible diameter adjustment, low electric consumption, and shorter production time. Nevertheless, it was revealed that many key properties of the biomass-derived carbon nanofiber have yet to be fully investigated, as there are still knowledge gaps to be filled for each technique. Thus, more studies are needed to broaden the existing understanding in the key parameters of different techniques in order to develop a highly desirable carbon nanofiber from biomass for sustainable energy storage application. Graphical abstract Image 1 Highlights • Challenges and use of biomass in supercapacitor application are reviewed. • Techniques to convert biomass into carbon nanofiber are reviewed. • Biomass is a promising carbon nanofiber material for energy storage application. • Different techniques are used for high product yield and low production cost. • Limited study on many key properties of biomass-derived carbon nanofiber. [ABSTRACT FROM AUTHOR]

Asymmetric supercapacitors usually possess higher energy density than symmetric supercapacitors. It's still a big challenge to synthesize low-cost and high-performance negative electrode active materials for the practical production of asymmetric supercapacitors. In this research, ginkgo leaf derived nitrogen-doped carbon was prepared and investigated as an electrode active material for the utilization in supercapacitors. Due to the hierarchical porous architecture, high N content, and ultrahigh ratio (86.5%) of pyridinic plus pyrrolic N species, the ginkgo leaf derived nitrogen-doped carbon material delivered a better specific capacitance (345 F g −1 at 0.2 A g −1 ) compared to pristine ginkgo leaf derived carbon and KOH-activated carbon without N-doping. Moreover, an asymmetric supercapacitor with this nitrogen-doped carbon as the negative electrode material also displayed an excellent energy density (42.2 Wh kg −1 at 700 W kg −1 ) and satisfactory electrochemical cycling reliability. In addition, these performances are also superior to those of some similar carbon materials, manifesting a good potential of this nitrogen-doped carbon to fabricate high-performance asymmetric supercapacitors. [ABSTRACT FROM AUTHOR]

Low-cost, high-performance electrodes are highly attractive for practical supercapacitor applications. MnO 2 -deposited carbon nanofiber mats (MnO 2 -CNFMs) are prepared for use as binder-free supercapacitor electrodes. MnO 2 is deposited on the mats in situ by hydrothermally decomposing aqueous KMnO 4 , leading to the formation of nanocrystals of MnO 2 . The MnO 2 -CNFM electrode produced with 38.0 μmol KMnO 4 (this electrode) shows a high specific capacitance of ~171.6 F·g −1 at a scan rate of 5 mV·s −1 . Moreover, a symmetric supercapacitor with the electrode exhibits a specific capacitance of 67.0 F·g −1 , an energy density of 6.0 Wh·kg −1 and a power density of 160 W·kg −1 at a special current of 0.1 A·g −1 . Further, the symmetric supercapacitor displays excellent cycling stability, retains approximately 99% of the capacitance after 1000 cycles. The simplicity and ease of preparation of the MnO 2 -CNFMs as well as their suitability for use in coin-type supercapacitor cells make them ideal for application in cost-effective and high-performance electrodes for supercapacitors. [ABSTRACT FROM AUTHOR]

Interest in the direct growth of carbon nanostructures on metal substrates is growing, especially in the field of supercapacitors, fuel cells, batteries and sensors. This paper presents results on the growth of carbon nanofibers (CNF) without the requirement of an external catalyst directly on nickel foam (Ni-foam) at a relatively low temperature of 400 °C. Etching of Ni-foam leads to the growth of CNF forests covering entirely the internal surfaces of the Ni-foam, with CNF diameters that can be tuned between 78 ± 32 nm and 375 ± 35 nm through a change in the growth temperature between 400 and 700 °C. Etching was found to be important to obtain a uniform surface CNF coverage and growth, particularly at higher temperatures. These CNF/Ni-foam composites yield 3D nano-scale internal forest structures in good contact with the micro-scale porosity of the metallic foam electrode. This work provides a foundation to use binderless CNF composite electrodes to obtain higher capacitance. [ABSTRACT FROM AUTHOR]

Fifteen microporous carbons with variable nanotextural characteristics were prepared by KOH activation through tuning the KOH/carbon ratio and activation temperature. The prepared porous carbons have a high ratio of micropores and specific surface area up to 95% and 1410 m2 g−1, respectively. Combining the pore-structure analyzes and electrochemical measurements in aqueous KOH and H 2 SO 4 electrolytes, it is shown that the complexity of the pore structure has a significant effect on the electrochemical performance. The solvated/naked K + can penetrate across the narrow pore entrance of the microporous carbons with an average pore size smaller than 0.6 nm and form electric double-layer (EDL) capacitance, while solvated/naked SO 4 2− cannot due to its larger ionic size. However, the penetration of SO 4 2− followed by hydrated H + become available when the average pore size is larger than 0.6 nm. With the combination of pseudocapacitance and EDL capacitance, microporous carbon shows a much higher supercapacitive performance in H 2 SO 4 than that in KOH electrolyte. This work on pore-structure dependence of supercapacitive performance paves a guide for tailoring pore-structure suitable for aqueous KOH and H 2 SO 4 electrolytes. [ABSTRACT FROM AUTHOR]

Carbon-based supercapacitors with outstanding electrochemical performances are strongly desired for the development of portable and wearable electronics. From the free radical engineering point of view, this study innovatively developed carbon/carbon gradient-structured microspheres (CCGMs) by the strategy of "third-order graduation polymerization" and "dynamic radical oxidation". Compared to conventional hybrid materials, for the first time, the gradient structure is proved to be extremely beneficial for improving the capacitive performance. Benefiting its gradient-structured advantages, the CCGMs exhibited "three-ultrahigh" performance with gravimetric, volumetric, and areal capacitances of 408.23 F g−1, 741.11 F cm−3, and 4390 μF cm−2, respectively. In addition, the assembled all-solids-state micro-supercapacitors delivered superior volumetric and areal specific capacitances (7.704 F cm−3 and 9.245 mF cm−2 at 5 μA cm−2), excellent life-span (100% after 12000 cycles), excellent volumetric and areal energy densities (1070 mWh cm−3 and 1284 μWh cm−2). This work paves a new way to develop unique carbon composites for high‐performance energy storage devices. • A third-order graduation polymerization method was developed. • The dynamic radical oxidation method was used for ultramicroporous-confined defects. • The gradient structure could improve the "three-ultrahigh" performance of carbons. [ABSTRACT FROM AUTHOR]

• The 3D honeycomb-like carbons (3DHCs) constructed by interconnected carbon nanosheets were prepared. • The 3DHCs present high specific surface area and 3D honeycomb-like structures. • The 3DHCs display high capacitance, high energy density and excellent cycle stability. Herein, the 3D honeycomb-like carbons constructed by interconnected carbon nanosheets (3DHCs) were prepared by salt template strategy. The 3DHCs present high specific surface area, honeycomb-like structures and 3D interconnected sheet-like network. As a result, the 3DHC displays high gravimetric capacitance of 326.5F g−1 at 0.05 A g−1, excellent rate capability of 246.3F g−1 at 50 A g−1 and high energy density of 11.3 Wh kg−1 when used as electrode for supercapacitor. Impressively, the capacitance of 3DHC 850 -based supercapacitor only decays 0.2% after 15,000 cycles. This work offers a low-cost, environmental-friendly method for the design of electrode materials for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

• Flexible carbon nanobelt webs with hierarchical pores and N/O groups are fabricated. • Humidity is revealed to be the key to prepare the nanobelts. • Magnesium nitrate helps to inhibit inter-nanobelt adhesions and warping of nanobelts. • Reducing warping improves the conductivity and bulk density of carbon nanobelt webs. • Face-to-face inter-belt connection triggers higher volumetric capacitance. Flexible carbon nanobelt webs (CNBWs) with a hierarchical porous structure, considerable N- and/or O-containing surface functionalities were fabricated by electrospinning of phenolic resin/PVP/magnesium nitrate (MNH) solution, followed by curing, thermal treatment and picking. The effect of spinning humidity on the morphology of cured fibers was investigated. The results showed that low humidity was required for successful spinning and collection of the nanobelts. The addition of MNH played a crucial role in inhibiting inter-nanobelt adhesions and warping of nanobelts during thermal treatment and producing hierarchical porous structure. The increase in MNH content resulted in an enhancement in the specific surface area (SSA), micropore volume, and mesoporosity of the CNBWs. The achieved CNBWs displayed the maximum SSA of 779 m2 g−1 and a mesoporosity of 82%. The reduction in the number of warping endowed the CNBWs with face-to-face inter-nanobelt connection, then brought about a significant enhancement in conductivity and packing density of the CNBWs, which ultimately improved the rate performance and volumetric capacitance. The work proposed a feasible route for improving the conductivity and volumetric capacity of electrospun carbon nanofiber webs as the electrode for supercapacitors or batteries. [ABSTRACT FROM AUTHOR]

Lithium sulfide (Li 2 S) cathode can pair with metallic-Li-free high-capacity anodes to avoid the notorious lithium dendrite growth and resulting serious safety hazards. However, its high sensitivity to moisture and oxygen makes time-consuming slurry-casting process not appropriate for Li 2 S cathode production. Herein, interconnected carbon nanofibers (CNFs) and porous carbon (PC) inlaid with Li 2 S (Li 2 S@PC@CNF) has been fabricated via a carbothermal reduction strategy by selecting a cost-effective and environmentally friendly precursor, i.e., bacterial cellulose (BC) hydrogel filled with glucose and Li 2 SO 4. Self-supporting Li 2 S@PC@CNF could be directly applied as the cathode, thereby detouring the routinely needed slurry-casting procedure. CNFs serve as a network for electron transport and meanwhile a skeleton to support the free-standing Li 2 S@PC@CNF electrode, while PC seamlessly connects CNFs due to the initial hydrogen bonding between glucose and cellulose, providing physical confinement for lithium polysulfides and large interface area for electrochemical reaction. Thereby, due to its unique ferroconcrete-like architecture, Li 2 S@PC@CNF based LSBs delivers a high initial specific capacity of 700 mA h g−1 with 500 mA h g−1 retained after 400 cycles, and presents promising rate capability of 450 mA h g−1 at 2 C. Image 1 • A facile and economical method to fabricate self-supporting Li 2 S cathodes was demonstrated. • The mechanism for the formation of the self-supporting Li 2 S cathodes has been elucidated. • The Li 2 S cathodes presented excellent electrochemical performance. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon nanofibers (NCNFs) are important electrode materials that have received tremendous attention in terms of their capacity to store energy. At present, it is still desirable to fabricate high-performance NCNFs for supercapacitors. Here, for the first time, polyacrylonitrile@branched polyethylenimine (PAN@bPEI) composite nanofibers are proposed as precursors to prepare freestanding NCNFs, which can then be used directly in flexible supercapacitors. The single electrode based on the resultant NCNFs with unique chemical composition exhibits electrochemical properties that are superior to those of the polyacrylonitrile-derived CNFs electrode. In addition, a quasi-solid-state symmetric supercapacitor assembled without the use of any adhesive or conductive agent also shows a comparable energy density, favorable cycling durability, and mechanical stability, indicating that bPEI is an effective nitrogen source with which to construct nitrogen-doped carbon fibers for energy storage applications. • The freestanding nitrogen-doped carbon nanofibers (NCNFs) were prepared. • Polyacrylonitrile@branched polyethylenimine nanofibers are proposed as precursors. • The obtained NCNFs exhibited excellent supercapacitive performance and flexibility. [ABSTRACT FROM AUTHOR]

Persuing both high energy and power density in one supercapacitor at low cost is very challenging to date. Here, we report the fabrication of nitorgen and Sulphur co-doped graphene (GN) modified lignin/polyacrylonitrile (PAN)-based carbon nanofiber (ACNFs) from mainly the biomass of lignin following a process of electrospinning, carbonization and activation. GN is used as nitrogen/sulphur immobilization agent to successfully capture HCN, NH 3 and SO 2 released from lignin and PAN during carbonization, and thus the content of heteroatoms of N and S in ACNFs is increased. The resulting ACNF with 0.30 wt% GN content possesses the maximum specific surface area of 2439 m2 g−1. It shows a typical three-dimensional porous network structures with the highest heteroatom doping content and high degree of crystallinity. The assembled supercapacitor exhibits superior electrochemical performance with ultra-high specific capacitance of 267.32 F g−1, low equivalent series resistance of 5.67 Ω, and outstanding cycling stability of 96.7% capacitance retention after 5000 cycles of charge/discharge in a two-electrode system with 6 mol L−1 KOH as electrolyte. Most importantly, the assembled symmetric supercapacitor shows that ACNFs doping with GNs increases the energy density from 4.12 to 9.28 Wh kg−1 and at the same time with barely reduced power density. • Using GNs as an adsorbent to capture HCN, NH 3 , SO 2 released in carbonization. • Proposing the water wetting behaviour to evaluation the supercapacitor performance. • Elucidated the mechanism between heteroatom doping and electrochemical properties. [ABSTRACT FROM AUTHOR]

Polyaniline has been widely used in high-performance pseudocapacitors, due to its low cost, easy synthesis, and high theoretical specific capacitance. However, the poor mechanical properties of polyaniline restrict its further development. Compared with polyaniline, functionalized carbon materials have excellent physical and chemical properties, such as porous structures, excellent specific surface area, good conductivity, and accessibility to active sites. However, it should not be neglected that the specific capacity of carbon materials is usually unsatisfactory. There is an effective strategy to combine carbon materials with polyaniline by a hybridization approach to achieve a positive synergistic effect. After that, the energy storage performance of carbon/polyaniline hybridization material has been significantly improved, making it a promising and important electrode material for supercapacitors. To date, significant progress has been made in the synthesis of various carbon/polyaniline binary composite electrode materials. In this review, the corresponding properties and applications of polyaniline and carbon hybrid materials in the energy storage field are briefly reviewed. According to the classification of different types of functionalized carbon materials, this article focuses on the recent progress in carbon/polyaniline hybrid materials, and further analyzes their corresponding properties to provide guidance for the design, synthesis, and component optimization for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]