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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]

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]

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]

Highly flexible freestanding carbon nanofibers were electroplated with silver for use in supercapacitor applications. The brittle carbon nanofibers were encased within bendable silver shells to provide superior flexibility and resilience of the supercapacitors. The enhanced electrical conductivity derived from the silver shell structure dramatically increased the capacitance of the supercapacitor. The silver shell also conferred structural stability to the carbon core, thus furnishing stable, long-term electrode performance. Nearly 100% of the specific capacitance was retained after N  = 10,000 galvanostatic charge-discharge cycles. The mechanical endurance or stability of the fabricated electrode was evaluated using 1,000 bending cycles, demonstrating that the electrode performance remained unchanged. Cyclic voltammetry and galvanostatic discharge curves were measured at various scan rates and current densities. The fabricated electrodes were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy, which clearly illustrated the carbon-core and silver-shell structure. [ABSTRACT FROM AUTHOR]

Iron oxide particle-decorated, hollow, carbon nanofibers (HCNFs), with poly(styrene-co-acrylonitrile) solution as the core and acetic acid lignin as the shell, were manufactured using a coaxial electrospinning technique, using iron(III) acetylacetonate as the iron oxide-precursor additive in the shell. The fabricated HCNFs exhibited a high specific capacitance of 121 F·g −1 at 0.5 A·g −1 , which was 2.18-fold that of solid electrospun nanofibers under the same conditions. The samples also possessed a superior cycling life, with a 90% retention rate after 1000 cycles in 1 M sodium sulfite. In this system, HCNFs exhibited high surface areas, as the result of hollow structures and producing capacitance improvement, while iron oxide particles enhanced electrochemical properties via reversible redox reactions. The attractive performances exhibited by these supercapacitors yielded them potentially promising candidates for future energy storage systems. [ABSTRACT FROM AUTHOR]

Abstract Potassium-pre-intercalated δ-phase MnO 2 is uniformly grown on carbon nanofibers for the positive electrode of asymmetric supercapacitors. An electrospun CNF is chemically activated with KOH at 800 °C for the negative electrode, showing ideal capacitive behavior. The crystallinity of MnO 2 is significantly reduced by the pre-intercalation of K ions into its layered structure. This textural characteristic is beneficial to the K+ diffusion into/out the interlayer structure, leading to effective utilization of the electroactive material of K x MnO 2. This unique composite electrode provides both ideal pseudo-capacitive behavior from K x MnO 2 and excellent electric conductivity from the CNF network, exhibiting a fairly high specific capacitance value of 279 F g-1 at 1 A g−1 with ca. 82.3% capacitance retention from 1 to 32 A g−1. A flexible ASC consisting of the positive K x MnO 2 @CNF electrode, a paper separator, and the negative ACNF electrode is successfully assembled. This cell shows superior ASC performances: a high cell voltage between 0 and 2 V, excellent capacitance retention (10,000 cycles with 10% decay), and simultaneously reaching high specific energy and power of 21.1 Wh kg−1 and 9.5 kW kg−1. The charge storage behavior of this cell without bending and with a bending angle of 90° shows no apparent difference, demonstrating its potential in the next-generation flexible energy storage devices. Highlights • K-preintercalation favors the K+ diffusion into the interlayer structure of δ-MnO 2. • K-preintercalation enhances the pseudocapacitance utilization of δ-MnO 2. • K-preintercalated δ-MnO 2 is uniformly grown on CNF with ideal behavior for flexible ASCs. • This ASC shows excellent cell capacitance retention and flexibility. [ABSTRACT FROM AUTHOR]

For the first time, a bottom-up approach was adopted to prepare free-standing orthorhombic Nb 2 O 5 -anchored carbon nanofibers (Nb 2 O 5 @CNFs) hybrid paper via in-situ solvothermal synthesis of Nb-metal organic framework@CNFs hybrid and subsequent pyrolysis process. The nanocrystalline Nb 2 O 5 decorated on the CNF surfaces improved the charge storage performance through synergistic effect between porous CNFs (EDLC) and Nb 2 O 5 (pseudocapacitance). Moreover, the high surface area and core-shell structure of Nb 2 O 5 @CNF hybrid reduce diffusion limitations and facilitate ionic transport. The Nb 2 O 5 @CNF hybrid paper as a binder-free electrode delivered greater specific capacitance of 633.6 F/g (975.7 F/cm3) in 1 M H 2 SO 4 , compared to Li 2 SO 4 electrolyte (524.3 F/g) at 0.5 A/g. However, the Nb 2 O 5 @CNF electrode showed better cycling stability in neutral Li 2 SO 4 electrolyte than in acidic H 2 SO 4 electrolyte. The solid-state asymmetric supercapacitor (ASC) based on Nb 2 O 5 @CNF paper and activated carbon (AC) electrodes delivered higher energy density of 62.1 Wh kg−1 at 292.7 W kg−1 in Li 2 SO 4 electrolyte due to a wider working potential window (0–1.5 V), compared to H 2 SO 4 electrolyte (55 Wh kg−1). The Li 2 SO 4 -based ASC cell is also capable of producing an energy density of up to 45.6 Wh kg−1, even at a high-power density of up to 5853.6 W kg−1. The as-assembled ASC demonstrated low self-discharge rate as well as excellent bending stability, indicating its excellent prospects in real-life applications. • Flexible Nb 2 O 5 nanoparticles-anchored CNF hybrid paper fabricated form Nb-MOF@CNF for supercapacitor. • Salf-standing Nb 2 O 5 @CNF electrode achieved a high specific capacitance of 633.6 F/g (975.7 F/cm3) at 0.5 A/g. • Nb 2 O 5 @CNF//AC asymmetric device delivers a high energy density of 62.1 Wh kg−1 and excellent power of 5854 W kg-1 in 1 M Li 2 SO 4. • ASC device demonstrated excellent bending stability and low self-discharge rate. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ti 3 C 2 T x MXene integrated hollow carbon nanofiber coated with outside inside polypyrrole layers (PPy@MXHCNF) is designed. • ZnCoMOF grown over PPy@MXHCNF is used to develop freestanding cathode (ZCO@PPy@MXHCNF) and anode (NPC@MXHCNF) materials. • ZCO@PPy@MXHCNF and NPC@MXHCNF exhibit specific capacitance of 1567.5 F g−1 and 477.21F g−1, respectively. • The assembled flexible ASC device delivers an energy density of 61.3 Wh kg−1 at 796.8 W kg−1. Effective customization of Ti 3 C 2 T x MXenes by electrospinning technique is crucial for the preparation of freestanding/flexible electrodes exhibiting enhanced performance in supercapacitors. Herein, we prepared MXenes containing hollow carbon nanofibers (MXHCNF) by co-axial electrospinning, and the inside-out of MXHCNF is decorated with polypyrrole layers (PPy@MXHCNF), which is sufficiently flexible, conductive, and highly functionalized with a unique trilayer morphology. Using the self-designed electroactive PPy@MXHCNF, a ZnCoMOF is homogeneously grown. The as-prepared bimetallic MOF on PPy@MXHCNF is used as a common precursor with which to fabricate the positive (ZCO@PPy@MXHCNF) and negative (NPC@MXHCNF) electrodes by a controlled heat treatment process using a "two from one" strategy. The freestanding positive and negative electrodes provide specific capacitances of 1567.5 F g−1 and 477.2 F g−1 at 1 A g−1, respectively, with high capacitance retention, cyclic stability, and coulombic efficiency. A flexible asymmetric device (ZCO@PPy@MXHCNF//NPC@MXHCNF) is assembled, and it exhibits an energy density of 61.3 Wh kg−1 at a power density of 796.8 W kg−1 and 92.8% capacitance retention after 10,000 GCD cycles. This work provides a unique approach involving MXene modification, polypyrrole decorated electrospun MXHCNFs as efficient substrates for freestanding electrodes, and the use of bimetallic MOF as a common strategic route for both positive and negative electrodes in flexible asymmetric supercapacitors. [ABSTRACT FROM AUTHOR]

With increasing demand for sustainable energy, it is essential to develop low cost, high performance, and environment-friendly materials for energy storage application. Metal oxides and sulfides are mostly being used as electrode materials for energy storage devices. However, their wide applications are precluded due to their higher cost, low stability, and adverse effect on the environment. Therefore, development of environment-friendly supercapacitors with low cost, high performance, and stable performance is a big challenge. Here, we report surface engineered carbon nanofibers for durable and high-performance supercapacitor. Surface engineered carbon nanofibers showed the highest specific capacitance of 277 F/g (at 1 mV/s), along with superior flexibility and cyclic stability. Moreover, they showed high energy and power density of 30.5 Wh/kg and 8.3 kW/kg, respectively. The cyclic stability showed almost 100% retention in charge storage capacity up to 5000 cycles. Electrochemical properties of a fabricated symmetrical supercapacitor device using these carbon nanofibers showed improved charge storage capacity at elevated temperatures. The charge storage capacity improved by over 150% by increasing temperature from 10 to 60 °C. Our results suggest that surface engineered carbon nanofibers could be a potential candidate for higher performance and durable 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]

The composites of transition metal oxide and carbon nanofibers (CNF) are promising electrode materials for supercapacitors in alkali solutions. However, the weak binding and unsatisfactory rate performance limit their application. To improve the weak binding, this study prepared the SiO 2 -modified carbon nanofibers (Si 1 -C) via electrospinning. Then the fully encapsulated CoO-NiO (NiCo@Si 1 -C) was fabricated on Si 1 -C by solvent-thermal and calcination. As is revealed, CNF containing SiO 2 is conducive to forming a full coverage of CoO-NiO coating with a stacked petal structure. More importantly, nano-SiO 2 plays the anchoring role of NiO-CoO and CNF, making the combination more firmly. The NiCo@Si 1 -C delivers a specific capacitance of 518.1 F g−1 at 0.5 A g−1, almost 2.25 times that of NiCo@Si 0 -C (229.9 F g−1 at 0.5 A g−1). When the current density increases to 50 A g−1, it is only 3.9 % lower than the capacitance (497.9 F g−1), which means a high rate performance. Moreover, asymmetric supercapacitor devices are assembled with activated carbon (NiCo@Si 1 -C//AC) with an energy density of 11.7 Wh kg−1, even at a high power density of 14,000.7 W kg−1. [Display omitted] • Nano-SiO 2 plays the anchoring role of NiO-CoO and CNF, making the combination more firmly. • The NiCo@Si 1 -C has a unique all-encapsulated CoO-NiO with a stacked petals structure. • The NiCo@Si 1 -C has ultra-high rate performance. [ABSTRACT FROM AUTHOR]

Carbon nanofibers modified with carboxyl groups (CNF-COOH) possessing good wettability and high porosity are homogeneously deposited with amorphous manganese dioxide (amorphous MnO 2 ) by potentiodynamic deposition for asymmetric super-capacitors (ASCs). The potential-cycling in 1 M H 2 SO 4 successfully enhances the hydrophilicity of carbonized polymer nanofibers and facilitates the access of electrolytes within the CNF-COOH matrix. This modification favors the deposition of amorphous MnO 2 and improves its electrochemical utilization. In this composite, MnO 2 homogeneously dispersed onto CNF-COOH provides desirable pseudocapacitance and the CNF-COOH network works as the electron conductor. The composite of CNF-COOH@MnO 2 -20 shows a high specific capacitance of 415 F g −1 at 5 mV s −1 . The capacitance retention of this composite is 94% in a 10,000-cycle test. An ASC cell consisting of this composite and activated carbon as positive and negative electrodes can be reversibly charged/discharged to a cell voltage of 2.0 V in 1 M Na 2 SO 4 and 4 mM NaHCO 3 with specific energy and power of 36.7 Wh kg −1 and 354.9 W kg −1 , respectively. This ASC also shows excellent cell capacitance retention (8% decay) in the 2V, 10,000-cycle stability test, revealing superior performance. [ABSTRACT FROM AUTHOR]

Bacterial cellulose (BC), a typical biomass prepared from the microbial fermentation process, has been proved that it can be an ideal platform for design of three-dimensional (3D) multifunctional nanomaterials in energy storage and conversion field. Here we developed a simple and general silica-assisted strategy for fabrication of interconnected 3D meso-microporous carbon nanofiber networks by confine nanospace pyrolysis of sustainable BC, which can be used as binder-free electrodes for high-performance supercapacitors. The synthesized carbon nanofibers exhibited the features of interconnected 3D networks architecture, large surface area (624 m 2 g −1 ), mesopores-dominated hierarchical porosity, and high graphitization degree. The as-prepared electrode (CN-BC) displayed a maximum specific capacitance of 302 F g −1 at a current density of 0.5 A g −1 , high-rate capability and good cyclicity in 6 M KOH electrolyte. This work, together with cost-effective preparation strategy to make high-value utilization of cheap biomass, should have significant implications in the green and mass-producible energy storage. [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]

Self-supported porous carbon nanofibers (CNFs) network has been prepared by electrospinning technology assisted with template method. The as-prepared material is rich in sub-nanoscale pores and nitrogen and oxygen functional groups, which can serve as a fast conductive network with abundant electrochemical active sites and greatly facilitates the transport of electrons and ions. When the porous CNFs network is used as an electrode for supercapacitor in a three electrode system, it displays a high capacitance of 233.1 F/g at 0.2 A/g, and a capacitance of 130.2 F/g even at 14 A/g. It maintains a capacitance of 154.0 F/g with 90.17% retention after 4000 cycles at 2 A/g. Moreover, the assembled symmetric supercapacitor not only exhibits excellent rate capability and cycle performance, but also delivers an energy density of 4.17 Wh/kg and a power density of 2500 W/kg. The experimental results demonstrate that the prepared N, O co-doped carbon nanofibers with rich sub-nanoscale pores are a promising electrode material for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Free-standing carbon nanofibrous membranes are prepared by carbonization and H 2 O 2 activation of electrospun polyimide nanofibrous membranes. The green and facile H 2 O 2 activation method not only regulates the pore structure of carbon nanofibers but also introduces rich oxygen species, rendering a hierarchically porous and heteroatom-doped carbon electrode for supercapacitors. The optimal electrode (PI800-8) shows a high specific capacitance of 339.9 F g−1 (0.5 A g−1, 6 M KOH electrolyte) and excellent cycle durability with a capacitance retention of 98.4 % after 50,000 cycles (5 A g−1). Particularly, a non-aqueous symmetric supercapacitor assembled with 1 M Et 4 NBF 4 electrolyte shows a high operating voltage of 2.8 V, and delivers the maximum energy/power density of 37.3 Wh kg−1 and 28.0 kW kg−1, respectively. The H 2 O 2 activation method provides a green, efficient, and versatile strategy to improve the pore properties and chemical compositions of porous carbon materials towards energy applications. [Display omitted] • The N/O-codoped carbon nanofibrous membranes were prepared by commercial electrospun polyimide nanofibrous membranes. • The green H 2 O 2 activation was proposed to ameliorate the pore and chemical properties of carbon nanofibrous membranes. • Excellent comprehensive performance was presented for both aqueous/non-aqueous symmetric supercapacitor. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon nanofiber (NDCN) was synthesized via carbonization of polypyrrole (PPy) coated bacterial cellulose (BC) composites, where BC serves as templates as well as precursor, and PPy serves as the nitrogen source. The synthesized NDCN was employed as electrode for both supercapacitors and Li-ion batteries. The large surface area exposed to electrolyte resulting from the 3D carbon networks leads to sufficient electrode/electrolyte interface and creates shorter transport paths of electrolyte ions and Li + ion. Besides, the three types of N dopants in NDCN improve the electronic conductivity, as well as superior electrochemical performance. [ABSTRACT FROM AUTHOR]

In this work, a free-standing, flexible and highly conductive vanadium-carbon nanofiber composite has been fabricated as electrode for Supercapacitors. Vanadium monoxide (VO) coupled with amorphous vanadium covalent bonds (VO x ) are successfully incorporated into carbon nanofibers (VO/VO x /CNF) by electrospinning and heat treatment. A theoretical explanation is proposed for the formation of VO/VO x in CNF composites. The VO and VO x are respectively reduced and formed from vanadium precursors of vanadium dioxide (VO 2 ) and vanadyl (IV) acetylacetonate (VOA) by means of self-reduction method, in which carbon precursors (polyacrylonitrile and polyvinylpyrrolidone), small evolved gas molecules (CO, H 2 , HCN) and graphitized carbon act as self-reductants. No additional reductants is needed before or after heat treatment, avoiding the secondary contamination. The VO/VO x /CNF electrode has a specific capacitance of 325.7 F g −1 at a current density of 1 A g −1 and is capable of reserving 92% of its initial capacitance after 5000 cycles operating at a current density of 4 A g −1 in a symmetric two-electrode capacitor using 6 M KOH as an electrolyte. The superior electrochemical performance of VO/VO x /CNF may be attributed to two advantages. The first is the enhanced conductivity brought upon the incorporation of quasi-metallic VO (∼ 10 2 Ω −1 cm −1 ) and the network of nanowire, and the second is the rapid ion transfer rate caused by the rich vanadium redox couples VO/VO x and the well-developed pore structure. Notably, this work has also provided a facile method to obtain varaible low valence states from vanadium oxides through self-reduction, which may also be applied to synthesize other metal oxides-carbon nanofiber composites. [ABSTRACT FROM AUTHOR]

This study investigates the use of graphene oxides (GOs) and carbon nanotubes (CNTs) embedded in polyacrylonitrile-based carbon nanofibers (GO–CNT/CNF) as electrodes for the supercapacitor. GO–CNT/CNF was prepared by electrospinning, and was subsequently stabilized and activated. The specific capacitance of GO–CNT/CNF is 120.5 F g −1 in 0.5 M Na 2 SO 4 electrolyte, which is higher than or comparable to the specific capacitances of carbon-based materials in neutral aqueous electrolyte, as prepared in this study. GO–CNT/CNF also exhibits a superior cycling stability, and 109% of the initial specific capacitance after 5000 cycles. The high capacitance of GO–CNT/CNF could be attributed to the edge planes and the functional groups of GO, the highly electrical conductivity of CNT, and the network structure of the electrode. [ABSTRACT FROM AUTHOR]

Flexible composites with manganese oxides (MnO x ) nanocrystals encapsulated in electropun carbon nanofibers were successfully fabricated via a simple and practical combination of electrospinning and carbonization process. The as-formed MnO x /carbon nanofibers composites have a rough surface with MnO x nanoparticles well embedded in the carbon nanofibers backbones. When used as electrodes for supercapacitor, the resulting MnO x /carbon nanofiber composites exhibit good electrochemical performance with a specific capacitance of 174.8 F g −1 at 2 mV s −1 in 0.5 M Na 2 SO 4 electrolyte, a good rate capability at high current density and long-term cycling stability. It is expected that such freestanding composites could be promising electrodes for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

The demand for high-performance energy storage devices such as supercapacitors and lithium-ion batteries has been increasing to meet the application requirements of renewable energy systems. Here, high energy density aqueous asymmetric supercapacitor (ASC) is assembled based on carbon nanofibers (CNF) network positive electrode and tungsten trioxide (WO 3 ) nanorod bundles negative electrode. Polyaniline-based CNF are prepared by direct carbonization of polyaniline nanofibers. WO 3 nanorod bundles are synthesized via a simple sodium chloride assisted hydrothermal process. The CNF//WO 3 ASC device operates with a voltage of 1.6 V and achieved a high energy density of 35.3 Wh kg −1 at a power density of 314 W kg −1 . Furthermore, the device shows an excellent cycling performance with capacitance retention of 88% after 1000 cycles. [ABSTRACT FROM AUTHOR]

• Co-MOF structures were anchored on the flexible MX-CNF. • Co-PC@MX-CNF and MnO 2 @Co 3 O 4 -PC@MX-CNF electrodes were derived from Co-MOF@MX-CNF. • A flexible and wearable hybrid supercapacitor was assembled using these electrodes. • The device shows an energy density of 72.5 Wh kg−1 at 832.4 W kg−1. Freestanding and flexible electrodes are crucial for advancing flexible and wearable energy storage devices (FW-ESD). However, the significant trade-off between mechanical flexibility and electrochemical performance of electrodes limits the development of high-performance FW-ESD. Therefore, flexible and freestanding multi-component hybrid electrodes with improved electrochemical properties are in high demand. This work reports a rational design of cobalt-metal organic framework (Co-MOF) structures on a highly flexible and electroconductive MXene-carbon nanofiber mat (MX-CNF). Further, the Co-MOF@MX-CNF was used as a starting material to derive capacitive-type Co-PC@MX-CNF and battery-type MnO 2 @Co 3 O 4 -PC@MX-CNF functional multi-component electrodes for a high-performance flexible wearable hybrid supercapacitor (FW-HSC). Owing to their high specific surface area (SSA), wettability, conductivity, and abundant active sites, Co-PC@MX-CNF and MnO 2 @Co 3 O 4 -PC@MX-CNF exhibited a specific capacitance of 426.7 F g−1 and a specific capacity of 475.4 mAh g−1 at 1 A g−1, respectively, with excellent mechanical flexibility. Moreover, the two electrodes were used to fabricate an FW-HSC with an operating voltage window of 1.5 V, delivering an energy density of 72.5 Wh kg−1 at a power density of 832.4 W kg−1 with long-term stability (90.36 % capacitance retention). Furthermore, a series connection of two identical FW-HSC devices could power a digital clock and light up a green LED, demonstrating its potential as a power source for various wearable devices. [ABSTRACT FROM AUTHOR]

• The review focuses on potential of flexible, freestanding binder-free nanofiber electrodes for real time applications. • The advancement of the hollow/porous composite nanofibers, and process parameters are presented. • Morphology engineering over composite nanofibers for enhancing electrochemical performance is reviewed. • Current challenges and future prospect of binder free composite nanofibers for flexible SCs are suggested. The versatile electrospinning technique is scalable and suitable to fabricate highly conducting freestanding carbon nanofiber composite electrodes for energy storage devices. Freestanding/flexible electrodes hold enormous potential for use in wearable electronic devices. Carbon-yielding polymers and the optimal use of sacrificial polymers, metal oxides, and sulfides retain the flexibility and enhance the surface area and pseudocapacitance of electrodes. Both as-prepared electrospun fibers and carbonized nanofibers are compatible with surface decoration via various chemical and electrochemical routes. Metal oxides/sulfides with various morphologies, such as nanocones and nanosheets, can be grown on the carbon nanofibers or on the as-prepared electrospun fibers using chemical synthesis methods such as electrodeposition, hydrothermal processes, and chemical impregnation to enhance the pseudocapacitance of the electrodes. Similarly, the deposition of metal organic frameworks on as-prepared electrospun fibers embellishes these fibers with nanostructures of specific morphologies such as dodecahedral and spindle-shaped structures. Under optimal conditions, these morphologies do not hamper the flexibility of the fibers, and binders are not required to retain them or maintain the electrode integrity. The engineering of electrodes with various morphologies and process parameters is presented systematically. Electrospinning-derived electrodes that have demonstrated significant electrochemical performance are highlighted and critically analyzed, and the energy storage mechanisms of these supercapacitors are described in detail. [ABSTRACT FROM AUTHOR]

Highlights: [•] Porous carbon nanofiber paper was prepared by surface chemical etching. [•] Specific surface area and surface functionality were greatly increased. [•] Carbon nanofiber paper had high specific capacitance of 362Fg− 1. [•] High power density, energy density and good cycling stability were combined. [•] The carbon paper can find applications in desalination, absorption and catalysis. [ABSTRACT FROM AUTHOR]

In this work, we prepared MnO 2 electrodes by ultrasonic-assisted electrodeposition to study the influence of current density on the surface morphology and electrochemical performances of the MnO 2 , as well as the electrochemical performances of MnO 2 electrodes of supercapacitors and lithium-ion batteries. The prepared MnO 2 electrodes showed nanorod morphology, and the grain size changeed and presented a different distribution at different current densities. The electrochemical performances of as-prepared electrodes under a current density of 7 mA cm−2 shows a high mass specific capacitance of 415.4 F g−1 at the current density of 1 A g−1 in supercapacitors and 818.1 mA h·g−1 at 1 A g−1 after 200 cycles in lithium-ion batteries. • The effect of current density on the morphology and electrochemical properties was studied. • The electrochemical properties of MnO 2 used as electrode material of LIBs and supercapacitors were studied. • Adopting ultrasonic-assisted electrode-deposition makes the film uniform and stable. • MnO 2 for SCs shows 415.4 F g−1 at the current density of 1 A g−1. • MnO 2 for LIBs shows 818.1 mA h·g−1 after 200 cycles at 1 A g−1. [ABSTRACT FROM AUTHOR]

Abstract: This paper studies the synthesis and electrochemical characterization of novel graphene-beaded carbon nanofibers (G/CNFs) as electrode material for use in supercapacitor. The porous G/CNF films were prepared by electrospinning polyacrylonitrile (PAN)/N,N-dimethylformamide (DMF) solution dispersed with oxidized graphene nanosheets, followed by carbonization at 800 °C in a tubular quartz furnace. The morphology and chemical structure of the porous G/CNF films were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The electrochemical behavior of the synthesized G/CNF films as supercapacitor electrodes was characterized by means of cyclic voltammetry (CV), galvanotactic charge/discharge, and electrochemical impedance test in a 6 m KOH aqueous electrolyte. Electrochemical measurements revealed that the maximum specific capacitance of the porous G/CNF electrodes reached up to 263.7 F g− 1 at a discharge current density 100 mA g− 1. Furthermore, the supercapacitor exhibited very good cycling stability of energy storage with the retention ratio of 86.9% after 2000 cycles. The high electrochemical performance of the G/CNF electrodes was attributed to the unique nanostructural configuration, high electrical conductivity, and large specific surface area of the graphene nanosheets. [Copyright &y& Elsevier]

Abstract: The vanadium pentoxide (V2O5)/carbon nanofiber composites (CNFCs) were prepared from polyacrylonitrile/V2O5 in N,N-dimethylformamide by a simple electrospinning method, and their electrochemical properties as supercapacitor electrodes were investigated. Different loadings of V2O5, the microstructures of the CNFCs (e.g., nanometer-size diameters, high specific surface areas, narrow pore size distributions, and tunable porosities) were changed, and the textural parameters significantly affected the electrochemical properties of the composites. The CNFC capacitors delivered the high specific capacitances of 150.0Fg−1 for the CNFCs in an aqueous, with promising energy densities of 18.8Whkg−1, over a power density range of 400–20,000Wkg−1. The CNFCs simultaneously exhibited excellent capacity retention. [Copyright &y& Elsevier]

Abstract: In this work, poly(amide imide) solutions in dimethylformamide were electrospun into webs consisting of 350nm ultrafine nanofibers. These nanofiber webs were used to produce activated carbon nanofibers (ACNFs), through stabilization and carbonisation–activation processes. Experimental results indicated that ACNFs activated at 800°C afforded the highest specific surface area but low mesopore volume. The high specific surface area, mainly due to the micropores, introduced maximum specific capacitance at low current density (150Fg−1 at 10mAg−1). Elevating the volume fraction of mesopores gave maximum specific capacitance at high current density (100Fg−1 at 1000mAg−1), which could be explained on the basis of ion mobility in the pores. Thus, the capacitance of the supercapacitors was strongly dependent on the specific surface area and micro- or mesopore volume of the ACNFs. [Copyright &y& Elsevier]

Achieving high specific surface area and ion accessibility in graphene-based electrodes with a high mass loading for supercapacitors poses a significant challenge because strong π-π stacking of graphene sheets often blocks the access of electrolyte ions to active sites. Herein, we report a novel protocol to prepare free-standing laminated graphene/carbon nanofiber films as high areal mass-loading electrodes through a layer-by-layer electrospinning technique. The unique laminated structure of graphene/carbon nanofiber thin films can enhance electrolyte penetration and increase transportations of ions/electrons. The symmetric supercapacitors (SCs) using the as-obtained graphene/carbon nanofiber films as electrodes reach areal specific capacitance of 1536 mF cm−2 at a current density of 1 mA cm−2. Most importantly, the areal energy density of the SCs can reach 0.22 mWh cm−2 at a power density of 1 mW cm−2 with a high areal mass loading of 24 mg cm−2. The exceptional electrochemical properties of the laminated graphene/carbon nanofiber films render them promising materials for electrodes in SCs. [Display omitted] • Laminated graphene/CNFs were prepared via layer-by-layer electrospinning. • The unique laminated structure enhances ions accessibility at high mass loading. • The assembled symmetric supercapacitor exhibits high areal specific capacitance. [ABSTRACT FROM AUTHOR]

To enhance the electrochemical energy storage property of the carbon cloth (CC)-based supercapacitors, high-crystalline tetraaniline (cTA) nanofibers were deposited onto the oxidized carbon cloth (OCC) here, via a facile post-synthetic solution-based self-assembly method. With the optimized depositing condition, the flexible free-standing cTA/OCC-5 electrode was obtained with much higher specific capacitance of 2119.2 mF/cm2 at 1.0 mA/cm2 in comparison with the OCC of 1501.8 mF/cm2 and the tetraaniline impregnated OCC (TA/OCC) of 1623.1 mF/cm2, which was prepared by the solvent evaporation method with the same TA content as the cTA/OCC-5. To further improve the cyclic life of the cTA/OCC-5 electrode in symmetric solid-state supercapacitors, 0.01 M Na 2 SO 4 was added in the H 2 SO 4 /PVA gel electrolyte. With the similar energy density and power density, the H 2 SO 4 /Na 2 SO 4 /PVA gel-based device possessed higher cyclic stability with retention of 99.97% after 10,000 cycles than the H 2 SO 4 /PVA gel-based device of 90.58%. [Display omitted] • cTA/OCC was designed via post-synthetic solution-based self-assembly. • It possessed higher capacitance than the TA/OCC via solvent evaporation. • H 2 SO 4 /Na 2 SO 4 /PVA gel could enhance the cyclic stability of the flexible devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • An eco-friendly yet facile approach is proposed to fabricate nano porous fibers. • The porous carbon fibers exhibit satisfactory electrochemical performance. • A high-performance supercapacitor is constructed. Recently, tremendous attention has been paid to carbon-based fibers, particularly porous carbon fibers (PCFs), because of their great potential as electrodes for advanced supercapacitors (SCs). However, the relatively complex preparation and monotonous pore structure are still the most important challenge that PCFs needs to counter. In this work, an eco-friendly yet facile approach has been applied to synthesis PCFs with tunable multi-level pores and satisfactory electrochemical performance. By using the combinations of electrospinning technology, hard-template method and carbonization process, nanofibers with interconnected multi-level pores can be achieved. It is demonstrated that the pore engineered PCF possesses enhanced electrochemical performance. For instance, the PCF electrode possesses a high capacitance of 211 F g−1 in 6 mol L−1 KOH at a density of 0.5 A g−1 together with excellent rate capability. Meanwhile, a high areal capacitance of 1.2 F cm−2 also can be achieved at a mass loading of 10 mg cm−2. Additionally, symmetrical supercapacitor assembled by PCF electrodes exhibits good capacitance of 101.9 F g−1 at the current density of 0.5 A g−1, such device also can deliver an energy density up to 60.1 Wh kg−1 with ionic liquid electrolyte. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nickel sulfide sheet-like nanoarray (NiS) electrode was formed on carbon cloth. • Controllable secondary nanoflakes vertically grew on primary NiS nanosheets. • High energy storage ability was achieved in the assembled NiS hybrid battery. To produce three-dimensional (3D) low-inner-resistance electrode, nickel sulfide sheet-like nanoarray (NiS) with secondary nanoflakes vertically grown on primary nanosheets is fabricated via sulfurization of hierarchical structured Ni(OH) 2 supported on carbon cloth substrate. Due to profuse exposed-edge planes, the obtained electrode exhibits remarkable hybrid properties with a highly specific capacity of 361 μA h cm−2 at 2 mA cm−2 in 3 M KOH medium, and excellent cycling stability (85 % capacitance retention after 5000 cycles). Further, the fabricated flexible and lightweight electrode is used to evaluate its performance in a solid-state flexible hybrid battery. The assembled flexible hybrid battery exhibits a high energy density of 10.97 Wh kg−1 with a power density of 54.86 W kg−1 at an operating voltage of 1.6 V. Thus, the designed NiS nanosheet arrays are considered as remarkable electrode material for energy storage applications. [ABSTRACT FROM AUTHOR]

• SiC nanofibers with various secondary nanonetworks were fabricated. • Formation mechanism of secondary nanostructure of SiC nanofiber was proposed. • Integration of developed micropores, nanosized microporous domains and suitable mesopores. • Hierachical porous structure and diameter of microporous domains were regulated. • An excellent specific capacitance of 186 F g−1 was achieved at 100 A g−1. Carbon nanofiber has been one of the promising electrode materials for supercapacitors. It is desirable but still challenging to optimize meso-/micro-pore ratio and configuration while achieving a high specific surface area in carbon nanofibers. Here, we present the design and preparation of carbon nanofiber mats with both high specific surface area and rational meso-/micropore configuration by electrospinning tetraethyl orthosilicate (TEOS)/phenolic resin (PR)/polyvinylpyrrolidone (PVP)/F127 blend solution, followed by carbothermal reduction, removal of carbon and chlorination. Silicon carbide nanofibers constructed by regulatable secondary nanostructure were achieved by adjusting TEOS content in the spinning solution, derived from which microporous carbon nanofibers with considerable mesopores (60–70% in mesoporosity), diverse secondary nanostructure (24–44 nm), and high specific surface area (1765–1890 m2 g−1) were prepared. The formation mechanism of the diverse secondary nanostructure in carbon nanofiber was proposed. The carbide-derived carbon nanofibers showed an excellent specific capacitance (316 F g−1 at 0.1 A g−1) and high-rate capability (186 F g−1 at 100 A g−1) due to the enhanced ion transportation, which was achieved by shortening micropore channels and offering convenient mesoporous channel towards microporous domains. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni doped CNFs were prepared by a controlled electrospinning method. • Small Ni particles were homogenously decorated over CNFs. • Prepared Ni-CNFs was used as electro-active materials for the fabrication of electrochemical supercapacitors. • A moderately good specific capacitance of ∼ 347.5 Fg−1 achieved by Ni-CNFs electrode. Highly uniform nickel (Ni) doped carbon nanofibers (CNFs) were manufactured by a controlled electrospinning process using polyacrylonitrile as-carbon source and nickel acetate as Ni-source. The structural and morphological properties of Ni-CNFs evidenced the defined and smooth fibers with the average diameter of 200−300 nm. The Ni-doping on CNFs considerably improved the surface defects and structural properties of CNFs. For electrochemical supercapacitor application, the prepared Ni-CNFs was applied as electro-active electrode and capacitive properties were studied by measuring the cyclicvoltammetry (CV) in aqueous 1 M Na 2 SO 4 electrolyte. A reasonable specific capacitance of 347.5 Fg−1 was achieved by Ni-CNFs electrode which was 2 folds larger than that of pure CNFs electrode, suggesting the role of Ni doping into CNFs on the electrochemical performance. Ni-CNFs electrode showed the excellent capacity retention by 91 % over all cycle numbers in Na 2 SO 4 electrolyte. Thus, this work supplies a new route for preparation of high-quality metal doped CNFs via electrospinning method. [ABSTRACT FROM AUTHOR]

A flexible membrane electrode by embedding vanadium/cobalt oxides on carbon nanofibers is purposely designed and fabricated by electrospinning and controllable post-calcination, which can be directly used as the binder-free non-polarity electrodes for the assembly of asymmetric solid-state supercapacitor with extraordinarily high areal metrics. • Vanadium/cobalt oxides embedded on carbon nanofibers (VCO/CNFs) are fabricated. • The integration of V promotes the formation of CoO and boosts electroactivity. • VCO/CNFs can be used as binder-free non-polarity membrane electrodes. • VCO/CNFs yield superior areal metrics and flexibility as supercapacitor electrodes. For flexible capacitive energy storage units in wearable devices, areal metrics, such as areal capacitance and energy density, are exceptionally important, because of limitations on device volume and weight. One-dimensional carbon nanofibers composited with active metal oxides, such as cobalt monoxide (CoO), possess extraordinary electrochemical properties. However, low areal metrics and the polarity in the flexible asymmetric supercapacitor device are two crucial challenges. Herein, vanadium/cobalt oxides on carbon nanofibers (VCO/CNFs) are purposely designed and fabricated by electrospinning and controllable post-calcination, which can be used as a binder-free non-polarity membrane electrode for the assembly of high-performance flexible supercapacitor (FSC). Importantly, the rational incorporation of vanadium with varying valence states helps promote the formation of CoO phase, enriches the reaction sites and enhances the capability of local electron transport. As expected, the single electrode of VCO/CNFs yields an extraordinarily high areal capacitance of 1.83 F cm−2 at the current density of 8 mA cm−2. The as-obtained FSC with VCO/CNFs as both anode and cathode delivers an excellent areal energy density of 44.2 μWh cm−2 at a power density of 2.8 mW cm−2, a long-term cycling stability (retention rate of 95.2% over 10,000 cycles), and a good flexibility under even various bending conditions. To our best knowledge, these areal metrics are among the superior values reported. [ABSTRACT FROM AUTHOR]

Bimetallic carbides have aroused wide attention for energy-storage applications recently. In this work, one-dimensional Fe 2 MoC/CNFs (Fe 2 MoC/C nanofibers) are successfully synthesized via a facile electrospinning method for the first time. To obtain the most integrated structure between the Fe 2 MoC nanoparticles and carbon nanofibers, we explore the optimal heating rate during the carbonization treatment. Fe 2 MoC/CNFs exhibits an integrated one-dimensional structure under 800 °C with a heating rate of 5 °C/min. As revealed in the experimental results, Fe 2 MoC/CNFs possesses a high specific surface area of 196.9 m2/g, a high specific capacitance of 347.8 F/g at the current density of 1 A/g, an excellent rate capability of 91% capacitance retention from 1 A/g to 40 A/g, and shows superior cycling stability with the capacitance retention of about 85.6% and Coulombic efficiency of about 100% after 5000 cycles. An asymmetric supercapacitor coin-cell device using Fe 2 MoC/CNFs as the positive electrode displays an energy density of 14.5 Wh/kg at a power density of 300 W/kg and an outstanding cycling life of 93% retention after 5000 cycles. The impressive electrochemical performance indicates that the Fe 2 MoC/CNFs composite is a promising material for efficient supercapacitors. Image 1 • Fe 2 MoC nanofibers can be prepared via a facile electrospinning method. • Fe 2 MoC/CNFs-5 exhibits a superior rate capability and cycle stability. • ASC coin-cell device shows a promising energy and power density. [ABSTRACT FROM AUTHOR]

A novel facile and scalable strategy is developed to prepare a hierarchical porous nonwoven of hollow N-doped carbon nanofibers embedded with graphene nanosheets (HN-CNFs/GNs) as an integrated electrode for flexible all-solid-state supercapacitors. It was found that graphene nanosheets (GNs) were curled inside the electrospun fibers, but freely expanded and connected adjacent CNFs in the form of nanosheets after carbonization, thereby increasing the electrochemical capacitance interface and conductivity as well. When the weight ratio of GNs is 2 wt%, the HN-CNFs/GNs delivers high capacitance of 249 F g − 1 at 1 A g − 1 in a three-electrode configuration. A two-electrode symmetrical cell delivers extraordinary cycling stability with no capacitance degradation after 5000 cycles. The symmetric all-solid-state supercapacitor provides a remarkable cycling stability with a capacity retention of 90% after 2000 cycles and high rate capacity. The device also displays outstanding flexibility with no obvious capacitance decay even when bent to 180°. This research proves the potential application of the nonwoven of HN-CNFs/GNs in high efficient, wearable and flexible energy storage devices. Image 1 • A hierarchical porous nonwoven of hollow N-doped carbon nanofibers embedded with graphene nanosheets (HN-CNFs/GNs) was sythesized by a one-step method. • Graphene nanosheets (GNs) were found to be curled inside the electrospun fibers, but freely expanded and connected adjacent CNFs in the form of nanosheets after carbonization, thereby increasing the electrochemical capacitance interface. • The particular characteristics of the HN-CNFs/GNs, such as N-doping, hierarchical porosity and hollow fibers, providing a high specific capacitance (249 F g − 1 at a current density of 1 A g − 1 in three-electrode system), excellent cycle stability (99% retention of 5000 cycles in symmetric two-electrode system) and outstanding flexibility (no obvious decay when bending to 180° in all-solid-state device) when the adding ratio of GNs is 2 wt%. [ABSTRACT FROM AUTHOR]

• NPCNFs/PANI with Integrated architecture has been well designed. • 3D continuous and conductive network can reduce internal resistance effectively. • Large surface areas and hierarchical porosity decrease the ion diffusion length. • The all-solid-state flexible device exhibits desirable electrochemical properties. Electrode materials with rationally designed architecture are crucial to achieve high-performance supercapacitors. However, there is still a great challenge for integrating the features of large accessible surface areas, fast electron/ion transport kinetics and favorable mechanical flexibility within a single electrode. Herein, we propose a facile approach to fabricate high-performance freestanding carbon-based electrode of polyaniline modified nitrogen-doped hierarchical porous carbon nanofibers, which effectively combine the merits of highly conductive electrospun carbon nanofibers with hierarchical porous structure, suitable nitrogen content as well as pseudocapacitive materials. Benefiting from the well-designed architecture, the as-assembled symmetric all-solid-state flexible device exhibits a high specific capacitance of 260 F g−1 at 0.5 A g−1 and high rate capability with a capacitance retention of 60% at 16 A g−1. Furthermore, the device also displays a desirable energy density of 8.9 Wh kg−1 with power density of 0.27 kW kg−1 and excellent cycling stability with 80.1% capacitance retention after 10,000 charge-discharge cycles at 2 A g−1. Eventually, the as-designed composite electrodes open up new avenues for facile construction of high-performance supercapacitor electrodes. [ABSTRACT FROM AUTHOR]

The present work reports an organic molecule electrode (OME) based on the graphene and graphene nanomesh (GNM) hydrogel non-covalently functionalized by caffeic acid (CFA) molecules (denoted as G&GMH-CFA). In such electrode system, the three-dimensional conductive network has a cross-linking channel constructed by means of the in-plane pores on the graphene nanomesh, which is benefit for exposing more active sites accessible to electrolyte and accordingly enhancing supercapacitive behaviors of the OME. The G&GMH-CFA delivers a specific capacitance of 482.6 F g−1 at current density of 1 A g−1. And it is noted that the Faraday current response peaks are located in the positive potential range of 0.6 V, which is superior to the organic molecules electrode reported in the correlative works. In addition, the density functional theory (DFT) calculations are used to illuminate the core issue of charge storage mechanism and binding interactions between CFA and graphene. To match with the resultant positive electrode, AQ functionalize graphene-like nanoflower (CNF-AQ) was prepared as counterpart (negative) electrode. The assembled asymmetric supercapacitors (ASC) CNF-AQ//G&GMH-CFA2 could exhaustively release the supercapacitive performance due to match and self-coordination based on the reasonable matching of two electrodes in structure, charge quantity and kinetics during the electrochemical energy storage process. The CNF-AQ//G&GMH-CFA2 delivered energy density of 26.4 Wh kg−1 at the power density of 0.7 kW kg−1. Two tandem CNF-AQ//G&GMH-CFA2 devices could easily light 88 LEDs. The organic molecule electrode is fabricated by the CFA functionalized graphene hydrogel with plentiful transport channels inside of the conductive skeleton, matching with CNF-AQ to assemble full-carbon ASC could easily light 88 LEDs. Image 1 [ABSTRACT FROM AUTHOR]