Fabrication of porous carbon nanofibers and their application as anode materials for rechargeable lithium-ion batteries

A Recent Review of Electrospun Porous Carbon Nanofiber Mats for Energy Storage and Generation Applications

Electrospun porous carbon nanofiber mats have excellent properties, such as a large surface area, tunable porosity, and excellent electrical conductivity, and have attracted great attention in energy storage and power generation applications. Moreover, due to their exceptional properties, they can be used in dye-sensitized solar cells (DSSCs), membrane electrodes for fuel cells, catalytic applications such as oxygen reduction reactions (ORRs), hydrogen evolution reactions (HERs), and oxygen evolution reactions (OERs), and sensing applications such as biosensors, electrochemical sensors, and chemical sensors, providing a comprehensive insight into energy storage development and applications. This study focuses on the role of electrospun porous carbon nanofiber mats in improving energy storage and generation and contributes to a better understanding of the fabrication process of electrospun porous carbon nanofiber mats. In addition, a comprehensive review of various alternative preparation methods covering a wide range from natural polymers to synthetic carbon-rich materials is provided, along with insights into the current literature.

Role of Nanofibers in Encapsulation of the Whole Cell

In the field of biomaterial research, the electrospinning device is now used to manufacture nanofibers that can be used to encapsulate whole microorganisms such as bacterial cells, funguses, viruses, and even spores. The nanofiber encapsulated cells will have greater significance in the coming future because of their wide variety of applications in various fields. Nanofibers act as microorganism reservoir systems that enhance their properties such as viability, controlled release of products, biomedical applications, and bioremediation. The effect of electrostatic forces on a droplet of liquid polymer or polymer solution is based on electrospinning. Electrospun nanofibers act as ideal native extracellular matrices for microorganisms and have also had a tremendous advantage in drug delivery systems where modern research is still underway. During electrospinning, nearly all microorganisms may be inserted into a polymer matrix that forms a composite nanofiber. The evolution in electrospinning technique over the past few decades has become promising. New ideas have been generated to enhance the techniques and improve the overall applications and properties of nanofibers. This technique has been transformed by the advent of the electrospinning machine. The electrospun nanofibers can be chemically characterized by a wide variety of procedures such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). Electrospinning has various applications, for example, in wastewater treatment, tissue engineering, food industry, drug delivery, agriculture, and cosmetics. Nanofiber encapsulation of microorganisms increased the shelf life of the microorganisms; the cells remain viable for months. It also helps in the control release of bacterial products. The present review demonstrates the role of nanofiber in the encapsulation of the whole cell.

Enhancing capacity and transport kinetics of C@TiO2core-shell composite anode by phase interface engineering

In nanocomposite electrodes, besides the synergistic effect that takes advantage of the merits of each component, phase interfaces between the components would contribute significantly to the overall electrochemical properties. However, the knowledge of such effects is far from being well developed up to now. The present work aims at a mechanistic understanding of the phase interface effect in C@TiO₂core-shell nanocomposite anode which is both scientifically and industrially important. Firstly, amorphous C, anatase TiO₂and C@anatse-TiO₂electrodes are compared. The C@anatase-TiO₂shows an obvious higher specific capacity (316.5 mAh g^-1at a current density of 37 mA g^-1after 100 cycles) and Li-ion diffusion coefficient (4.0 × 10^-14cm²s^-1) than the amorphous C (178 mAh g^-1and 2.9 × 10^-15cm²s^-1) and anatase TiO₂(120 mAh g^-1and 1.6 × 10^-15cm²s^-1) owing to the C/TiO₂phase interface effect. Then, C@anatase/rutile-TiO₂is obtained by a heat treatment of the C@anatase-TiO₂. Due to an anatase-to-rutile phase transformation and diffusion of C along the anatase/rutile phase interface, additional abundant C/TiO₂phase interfaces are created. This endows the C@anatase/rutile-TiO₂with further boosted specific capacity (409.4 mAh g^-1at 37 mA g^-1after 100 cycles) and Li-ion diffusion coefficient (3.2 × 10^-13cm²s^-1), and excellent rate capability (368.6 mAh g^-1at 444 mA g^-1). These greatly enhanced electrochemical properties explicitly reveal phase interface engineering as a feasible way to boost the electrochemical performance of nanocomposite anodes for Li-ion batteries.

Preparation of Porous Carbon Nanofiber Electrodes Derived from 6FDA-Durene/PVDF Blends and Their Electrochemical Properties

Highly porous carbon electrodes for supercapacitors with high energy storage performance were prepared by using a new precursor blend of aromatic polyimide (PI) and polyvinylidene fluoride (PVDF). Supercapacitor electrodes were prepared through the electrospinning and thermal treatment of the precursor blends of aromatic PI and PVDF. Microstructures of the carbonized PI/PVDF nanofibers were studied using Raman spectroscopy. Nitrogen adsorption/desorption measurements confirmed their high surface area and porosity, which is critical for supercapacitor performance. Energy storage performance was investigated and carbonized PI/PVDF showed a high specific capacitance of 283 F/g at 10 mV/s (37% higher than that of PI) and an energy density of 11.3 Wh/kg at 0.5 A/g (27% higher than that of PI) with high cycling stability.

Carbon materials for ion-intercalation involved rechargeable battery technologies

The development of carbon electrode materials for rechargeable batteries is reviewed from the perspective of structural features, electrochemistry, and devices.

Structure and electrochemical performance of electrospun-ordered porous carbon/graphene composite nanofibers

Ordered carbon/graphene composite nanofibers (CGCNFs) with different porous configurations were used as a material to fabricate supercapacitor electrodes. These nanofibers were synthesized by applying a modified parallel electrode to the electrospinning method (MPEM) in order to generate electrospun polyacrylonitrile (PAN) nanofibers containing graphene. After synthesis, these fibers were submitted to carbonization under a N2 atmosphere at 1100 °C. The influence of the ordering and porosity of CGCNFs on their electrochemical performance was studied. The results showed that by adding deionized water to the spinning solution one could increase the number of mesopores and the specific surface area of CGCNFs, thereby significantly increasing their specific capacitance. In addition, the ordering of CGCNFs within the electrode improved the electron transfer efficiency, resulting in a higher specific capacitance.

Bio-derived Carbon Nanofibres from Lignin as High-Performance Li-Ion Anode Materials

Development of cost-effective and increasingly efficient sustainable materials for energy-storage devices, such Li-ion batteries, is of crucial future importance. Herein, the preparation of carbon nanofibres from biopolymer blends of lignin (byproduct from the paper and pulp industry) and polylactic acid (PLA) or a thermoplastic elastomeric polyurethane (TPU) is described. SEM analysis shows the evolving microstructural morphology after each processing step (electrospinning, stabilisation and carbonisation). Importantly, it is possible to tailor the nanofibre porosity by utilising miscibility/immiscibility rules between lignin and the polymer additive (PLA/TPU). PLA blends (immiscible) generate porous structures whereas miscible lignin/TPU blends are solid when carbonised. Electrodes produced from 50 % PLA blends have capacity values of 611 mAh g^-1 after 500 charge/discharge cycles, the highest reported to date for sustainable electrodes for Li-ion batteries. Thus, this work will promote the development of lignocellulose waste materials as high-performance energy-storage materials.

High Capacity Nano-Sized Carbon Spheres for Lithium-Ion Battery Anode Materials

A one-step hydrothermal method is reported for synthesizing carbon spheres (Cs) with sucrose as the carbon resource for the anode materials in lithium-ion batteries (LIBs). Firstly, the influences of synthesis temperature and time on particle size and the morphology of the Cs were researched. Then, modified carbon spheres (MCs) were synthesized with some surfactants, such as hexadecyl trimethyl ammonium bromide (CTAB) and polyvinyl alcohol (PVA). Finally, nano-sized MCs with an average diameter of 70 nm, owning the smooth surface and uniform spherical morphology systematically investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). The outstanding performances of nano-sized MCs synthesized with PVA were demonstrated as anode materials in LIBs. The higher initial discharge capacity of 1180 mAhg^-1 and the excellent discharge capacity of 470 mAhg^-1 were obtained respectively at 100 mAg^-1 (0.27 C) over 50 cycles. The nano-sized MCs has also shown remarkable performance of rate capability of 284.6 mAhg^-1 at 1.5 C. In addition, the cycling reversibility of the nano-sized MCs is more stable than that of the sub-micron sized MCs modified with CTAB and no surfactant respectively.

Cut-Price Fabrication of Free-standing Porous Carbon Nanofibers Film Electrode for Lithium-ion Batteries

Freestanding thin film electrodes are competitive candidate materials for high-performance energy stockpile equipment due to their self-supporting structure and because they lack any polymer binder or conductive additive. In our work, a porous carbon nanofiber film (PCNF) electrode has been synthesized via a convenient and low-cost electrospinning approach and the following carbonization and air etching process. The obtained PCNF electrode sample shows a high reversible capacity (1138 mAh g−1 at 0.1 C), remarkable rate capacity (101.2 mAh g−1 at 15 C), and superior cycling stability with a lower capacity decay rate of ~0.013% each cycle upon 1000 cycles (278 mAh g−1 at 5 C). The prominent electrochemical performance of PCNF can be put down to the stable self-supporting conductive structure and the porous feature in each carbon nanofiber, which will significantly promote the transfer tempo of Li-ion and electron and relieve the large volume change during inserting lithium ion. More interestingly, this work exhibits a low-cost and primitive strategy to fabricate thin film anode for lithium-ion batteries.

Strategies to Hierarchical Porosity in Carbon Nanofiber Webs for Electrochemical Applications

Morphology and porosity are crucial aspects for designing electrodes with facile transport of electrons, ions and matter, which is a key parameter for electrochemical energy storage and conversion. Carbon nanofibers (CNFs) prepared by electrospinning are attractive for their high aspect ratio, inter-fiber macroporosity and their use as self-standing electrodes. The present work compares several strategies to induce intra-fiber micro-mesoporosity in self-standing CNF webs prepared by electrospinning polyacrylonitrile (PAN). Two main strategies were investigated, namely i) a templating method based on the addition of a porogen (polymethyl methacrylate, polyvinylpyrrolidone, Nafion® or ZnCl2) in the electrospinning solution of PAN, or ii) the activation in ammonia of previously formed CNF webs. The key result of this study is that open intra-fiber porosity could be achieved only when the strategies i) and ii) were combined. When each approach was applied separately, only closed intra-fiber porosity or no intra-fiber porosity was observed. In contrast, when both strategies were used in combination all CNF webs showed high mass-specific areas in the range of 325 to 1083 m2·g−1. Selected webs were also characterized for their carbon structure and electrical conductivity. The best compromise between high porosity and high electrical conductivity was identified as the fibrous web electrospun from PAN and polyvinylpyrrolidone.

Nitrogen-Doped Multi-Scale Porous Carbon for High Voltage Aqueous Supercapacitors

Recently, "Water-in-salt" electrolyte has been reported to extend the working voltage of aqueous supercapacitor. However, this electrolyte needs the electrode materials possess some good features such as proper pore structure, high electron and ion conductivity. Herein, we fabricated the nitrogen-doped multi-scale porous carbon (NMC) by the simple enriching melamine-resorcinol-formaldehyde xerogels method with integrating triblock copolymer for micro-pores formation. All the results confirmed that our NMC is provided with a very high specific surface area (3,170 m2 g-1) and its monoliths are composed of multi-scale porous structure. By employing the nanostructured NMC as electrode materials, we have investigated the capability for high-voltage aqueous supercapacitor applications. The superconcentrated "Water-in-salt" electrolyte expand stability operating potential window of aqueous symmetric supercapacitor up to 2.4 V with a high energy density of 33 Wh kg-1 at power density of 0.3 kW kg-1. Our studies indicate that the NMC is potential materials for high performance over wider voltage range.

Design and synthesis of interconnected hierarchically porous anatase titanium dioxide nanofibers as high-rate and long-cycle-life anodes for lithium-ion batteries

We suggest an efficient and simple synthetic strategy to prepare interconnected hierarchically porous anatase TiO2 (IHP-A-TiO2) nanofibers by two synergetic effects: phase separation between polymers and relative humidity control during electrospinning. The macro channels formed by polystyrene decomposition were interconnected by numerous mesopores that were formed by evaporation of infiltrated water vapor in the structure. The resulting IHP-A-TiO2 nanofibers showed better Li+ ion storage performances than the TiO2 materials reported in the literature. The discharge capacity of IHP-A-TiO2 nanofibers for the 3000th cycle at 1.0 A g-1 and corresponding coulombic efficiency from the 20th cycle onward were 142 mA h g-1 and >99.0%, respectively. Well-interconnected, ultrafine TiO2 nanocrystals within the nanofiber showed structural stability during cycling and facilitated facile charge transfer at the electrode-electrolyte interface.

Electrochemical energy storage performance of carbon nanofiber electrodes derived from 6FDA-durene

Carbon nanofibers (CNFs) are promising electrode materials for electrochemical double layer capacitors due to their high porosity and electrical conductivity. CNFs were prepared by electrospinning and subsequent thermal treatment of a new precursor polymer, 6FDA-durene, without the addition of pore generating agents. The conversion of precursor nanofibers into CNFs was confirmed using Raman spectroscopy. CNFs were activated and annealed, and nitrogen adsorption/desorption measurements were conducted to determine surface area and porosity. These activated/annealed CNFs were used as binderless electrodes in coin cells with an ionic liquid electrolyte. The devices displayed a specific capacitance of 128 F g^-1, an energy density of 63.4 Wh kg^-1 (at 1 A g^-1), and a power density of 11.0 KW kg^-1 (at 7 A g^-1).

Electrospun Conjugated Polymer/Fullerene Hybrid Fibers: Photoactive Blends, Conductivity through Tunneling-AFM, Light Scattering, and Perspective for Their Use in Bulk-Heterojunction Organic Solar Cells

Hybrid conjugated polymer/fullerene filaments based on MEH-PPV/PVP/PCBM were prepared by electrospinning, and their properties were assessed by scanning electron, atomic and lateral-force, tunneling, and confocal microscopies, as well as by attenuated-total-reflection Fourier transform infrared spectroscopy, photoluminescence quantum yield, and spatially resolved fluorescence. Highlighted features include the ribbon shape of the realized fibers and the persistence of a network serving as a template for heterogeneous active layers in solar cell devices. A set of favorable characteristics is evidenced in this way in terms of homogeneous charge-transport behavior and formation of effective interfaces for diffusion and dissociation of photogenerated excitons. The interaction of the organic filaments with light, exhibiting specific light-scattering properties of the nanofibrous mat, might also contribute to spreading incident radiation across the active layers, thus potentially enhancing photovoltaic performance. This method might be applied to other electron donor-electron acceptor material systems for the fabrication of solar cell devices enhanced by nanofibrillar morphologies embedding conjugated polymers and fullerene compounds.

Carbon Paper with a High Surface Area Prepared from Carbon Nanofibers Obtained through the Liquid Pulse Injection Technique

To improve the performance of carbon paper used for applications such as electrodes for electrochemical devices and air filters, two types of long carbon nanofibers (CNFs) with average diameters of 20 and 49 nm were prepared by the liquid pulse injection (LPI) technique by adjusting reaction conditions. Carbon paper was made from the CNFs through a simple filtration process. The paper prepared from the CNFs with an average diameter of 20 nm (LPI-CNF(20) paper) was firm and flexible even though it was prepared without using any binders. LPI-CNF(20) paper also had a high surface area and showed a high electrical conductivity and a moderate gas permeability according to its void size. These properties are required for cathodes in the latest battery systems such as lithium-air batteries. In electrochemical experiments conducted to evaluate the performance of LPI-CNF(20) paper as a cathode, the paper showed a larger discharge capacity on the basis of the cathode weight than a conventional cathode (a commercially available carbon paper combined with a porous carbon), which indicated that it has a high potential to be used as a cathode in lithium-air batteries.

Synergism of Rare Earth Trihydrides and Graphite in Lithium Storage: Evidence of Hydrogen-Enhanced Lithiation

The lithium storage capacity of graphite can be significantly promoted by rare earth trihydrides (REH₃ , RE = Y, La, and Gd) through a synergetic mechanism. High reversible capacity of 720 mA h g^-1 after 250 cycles is achieved in YH₃ -graphite nanocomposite, far exceeding the total contribution from the individual components and the effect of ball milling. Comparative study on LaH₃ -graphite and GdH₃ -graphite composites suggests that the enhancement factor is 3.1-3.4 Li per active H in REH₃ , almost independent of the RE metal, which is evident of a hydrogen-enhanced lithium storage mechanism. Theoretical calculation suggests that the active H from REH₃ can enhance the Li⁺ binding to the graphene layer by introducing negatively charged sites, leading to energetically favorable lithiation up to a composition Li₅ C₁₆ H instead of LiC₆ for conventional graphite anode.

Metal-Organic Framework-Derived Materials for Sodium Energy Storage

Recently, sodium-ion batteries (SIBs) are extensively explored and are regarded as one of the most promising alternatives to lithium-ion batteries for electrochemical energy conversion and storage, owing to the abundant raw material resources, low cost, and similar electrochemical behavior of elemental sodium compared to lithium. Metal-organic frameworks (MOFs) have attracted enormous attention due to their high surface areas, tunable structures, and diverse applications in drug delivery, gas storage, and catalysis. Recently, there has been an escalating interest in exploiting MOF-derived materials as anodes for sodium energy storage due to their fast mass transport resulting from their highly porous structures and relatively simple preparation methods originating from in situ thermal treatment processes. In this Review, the recent progress of the sodium-ion storage performances of MOF-derived materials, including MOF-derived porous carbons, metal oxides, metal oxide/carbon nanocomposites, and other materials (e.g., metal phosphides, metal sulfides, and metal selenides), as SIB anodes is systematically and completely presented and discussed. Moreover, the current challenges and perspectives of MOF-derived materials in electrochemical energy storage are discussed.

Energy Device Applications of Synthesized 1D Polymer Nanomaterials

1D polymer nanomaterials as emerging materials, such as nanowires, nanotubes, and nanopillars, have attracted extensive attention in academia and industry. The distinctive, various, and tunable structures in the nanoscale of 1D polymer nanomaterials present nanointerfaces, high surface-to-volume ratio, and large surface area, which can improve the performance of energy devices. In this review, representative fabrication techniques of 1D polymer nanomaterials are summarized, including electrospinning, template-assisted, template-free, and inductively coupled plasma methods. The recent advancements of 1D polymer nanomaterials in energy device applications are demonstrated. Lastly, existing challenges and prospects of 1D polymer nanomaterials for energy device applications are presented.

Binder-Free N- and O-Rich Carbon Nanofiber Anodes for Long Cycle Life K-Ion Batteries

Carbon nanofibers produced by electrospinning of polyacrylonitrile polymer and subsequent carbonization were tested as freestanding potassium-ion anodes. The effect of oxygen functionalization on K-ion carbon anode performance was tested for the first time via plasma oxidation of prepared carbon nanofibers. The produced materials exhibited exceptional cycling stability through the amorphous carbon structuring and one-dimensional architecture accommodating significant material expansion upon K⁺ intercalation, resulting in a stable capacity of 170 mAh g^-1 after 1900 cycles at 1C rate for N-rich carbon nanofibers. Excellent rate performance of 110 mAh g^-1 at 10C rate, as compared to 230 mAh g^-1 at C/10 rate, resulted from the K-ion surface storage mechanism and the increased K⁺ solid diffusion coefficient in carbon nanofibers as compared to graphite. Plasma oxidation treatment augmented surface storage of K⁺ by oxygen functionalities but increased material charge transfer resistance as compared to N-rich carbon fibers. Ex situ characterization revealed that the one-dimensional structure was maintained throughout cycling, despite the increase in graphitic interlattice spacing from 0.37 to 0.46 nm. The carbon nanofibers demonstrate great potential as an anode material for potassium-ion batteries with superior cycling stability and rate capability over previously reported carbon materials.

Liquefied walnut shell-derived carbon nanofibrous mats as highly efficient anode materials for lithium ion batteries

Mechanically flexible walnut shell-derived carbon nanofibers (CNFs) of 175 nm diameter were fabricated from a liquefied walnut shell—polyvinyl alcohol (PVA) hybrid solutionviaconventional electrospinning followed by one-step carbonization.

Preparation of porous carbon nanofibers derived from PBI/PLLA for supercapacitor electrodes

Porous carbon nanofibers were prepared by electrospinning blend solutions of polybenzimidazole/poly-L-lactic acid (PBI/PLLA) and carbonization. During thermal treatment, PLLA was decomposed, resulting in the creation of pores in the carbon nanofibers. From SEM images, it is shown that carbon nanofibers had diameters in the range of 100-200 nm. The conversion of PBI to carbon was confirmed by Raman spectroscopy, and the surface area and pore volume of carbon nanofibers were determined using nitrogen adsorption/desorption analyses. To investigate electrochemical performances, coin-type cells were assembled using free-standing carbon nanofiber electrodes and ionic liquid electrolyte. cyclic voltammetry studies show that the PBI/PLLA-derived porous carbon nanofiber electrodes have higher capacitance due to lower electrochemical impedance compared to carbon nanofiber electrode from PBI only. These porous carbon nanofibers were activated using ammonia for further porosity improvement and annealed to remove the surface functional groups to better match the polarity of electrode and electrolyte. Ragone plots, correlating energy density with power density calculated from galvanostatic charge-discharge curves, reveal that activation/annealing further improves energy and power densities.

Carbon Nanomaterials Interfacing with Neurons: An In vivo Perspective

Developing new tools that outperform current state of the art technologies for imaging, drug delivery or electrical sensing in neuronal tissues is one of the great challenges in neurosciences. Investigations into the potential use of carbon nanomaterials for such applications started about two decades ago. Since then, numerous in vitro studies have examined interactions between these nanomaterials and neurons, either by evaluating their compatibility, as vectors for drug delivery, or for their potential use in electric activity sensing and manipulation. The results obtained indicate that carbon nanomaterials may be suitable for medical therapies. However, a relatively small number of in vivo studies have been carried out to date. In order to facilitate the transformation of carbon nanomaterial into practical neurobiomedical applications, it is essential to identify and highlight in the existing literature the strengths and weakness that different carbon nanomaterials have displayed when probed in vivo. Unfortunately the current literature is sometimes sparse and confusing. To offer a clearer picture of the in vivo studies on carbon nanomaterials in the central nervous system, we provide a systematic and critical review. Hereby we identify properties and behavior of carbon nanomaterials in vivo inside the neural tissues, and we examine key achievements and potentially problematic toxicological issues.

Graphitized porous carbon nanofibers prepared by electrospinning as anode materials for lithium ion batteries

Graphitized porous carbon nanofibers were prepared by electrospinning and subsequent calcining, exhibiting high capacity and good cycling stability.

Carbon nano-onions: large-scale preparation, functionalization and their application as anode material for rechargeable lithium ion batteries

Carbon nano-onions (CNOs) are one of the most promising anode materials for lithium ion batteries (LIBs) because of their outstanding physicochemical properties.

Carbon-Based Materials for Lithium-Ion Batteries, Electrochemical Capacitors, and Their Hybrid Devices

A rapidly developing market for portable electronic devices and hybrid electrical vehicles requires an urgent supply of mature energy-storage systems. As a result, lithium-ion batteries and electrochemical capacitors have lately attracted broad attention. Nevertheless, it is well known that both devices have their own drawbacks. With the fast development of nanoscience and nanotechnology, various structures and materials have been proposed to overcome the deficiencies of both devices to improve their electrochemical performance further. In this Review, electrochemical storage mechanisms based on carbon materials for both lithium-ion batteries and electrochemical capacitors are introduced. Non-faradic processes (electric double-layer capacitance) and faradic reactions (pseudocapacitance and intercalation) are generally explained. Electrochemical performance based on different types of electrolytes is briefly reviewed. Furthermore, impedance behavior based on Nyquist plots is discussed. We demonstrate the influence of cell conductivity, electrode/electrolyte interface, and ion diffusion on impedance performance. We illustrate that relaxation time, which is closely related to ion diffusion, can be extracted from Nyquist plots and compared between lithium-ion batteries and electrochemical capacitors. Finally, recent progress in the design of anodes for lithium-ion batteries, electrochemical capacitors, and their hybrid devices based on carbonaceous materials are reviewed. Challenges and future perspectives are further discussed.

Free-standing porous carbon nanofiber/ultrathin graphite hybrid for flexible solid-state supercapacitors

A micrometer-thin solid-state supercapacitor (SC) was assembled using two pieces of porous carbon nanofibers/ultrathin graphite (pCNFs/G) hybrid films, which were one-step synthesized by chemical vapor deposition using copper foil supported Co catalyst. The continuously ultrathin graphite sheet (∼ 25 nm) is mechanically compliant to support the pCNFs even after etching the copper foil and thus can work as both current collector and support directly with nearly ignorable fraction in a SC stack. The pCNFs are seamlessly grown on the graphite sheet with an ohmic contact between the pCNFs and the graphite sheet. Thus, the accumulated electrons/ions can duly transport from the pCNFs to graphite (current collector), which results in a high rate performance. The maximum energy density and power density based on the whole device are up to 2.4 mWh cm(-3) and 23 W cm(-3), which are even orders higher than those of the most reported electric double-layer capacitors and pseudocapacitors. Moreover, the specific capacitance of the device has 96% retention after 5000 cycles and is nearly constant at various curvatures, suggesting its wide application potential in powering wearable/miniaturized electronics.

Template-assisted synthesis of multi-shelled carbon hollow spheres with an ultralarge pore volume as anode materials in Li-ion batteries

Double/quadruple shells carbon hollow spheres can be obtained under the assistance of permeably mesoporous silica hollow spheres, which exhibit superior electrochemical performance.

Phenolic resin-grafted reduced graphene oxide as a highly stable anode material for lithium ion batteries

Preparation of phenol formaldehyde resin grafted reduced graphite oxide as an electrode material with highly enhanced electrochemical properties.

A Fe/Fe3O4/N-carbon composite with hierarchical porous structure and in situ formed N-doped graphene-like layers for high-performance lithium ion batteries

A Fe/Fe₃O₄/N-carbon composite consisting of a porous carbon matrix containing a highly conductive N-doped graphene-like network and Fe/Fe₃O₄ nanoparticles was prepared.

New electrospinning nozzle to reduce jet instability and its application to manufacture of multi-layered nanofibers

A new nozzle system for the efficient production of multi-layered nanofibers through electrospinning is reported. Developed a decade ago, the commonly used coaxial nozzle system consisting of two concentric cylindrical needles has remained unchanged, despite recent advances in multi-layered, multi-functional nanofibers. Here, we demonstrate a core-cut nozzle system, in which the exit pipe of the core nozzle is removed such that the core fluid can form an envelope inside the shell solution. This configuration effectively improves the coaxial electrospinning behavior of two fluids and significantly reduces the jet instability, which was proved by finite element simulation. The proposed electrospinning nozzle system was then used to fabricate bi- and tri-layered carbon nanofibers.