Hierarchical Graphene-Containing Carbon Nanofibers for Lithium-Ion Battery Anodes

MoS2-Decorated Graphene@porous Carbon Nanofiber Anodes via Centrifugal Spinning

Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries as green energy storage devices because of their similar working principles and the abundance of low-cost sodium resources. Nanostructured carbon materials are attracting great interest as high-performance anodes for SIBs. Herein, a simple and fast technique to prepare carbon nanofibers (CNFs) is presented, and the effects of carbonization conditions on the morphology and electrochemical properties of CNF anodes in Li- and Na-ion batteries are investigated. Porous CNFs containing graphene were fabricated via centrifugal spinning, and MoS₂ were decorated on graphene-included porous CNFs via hydrothermal synthesis. The effect of MoS₂ on the morphology and the electrode performance was examined in detail. The results showed that the combination of centrifugal spinning, hydrothermal synthesis, and heat treatment is an efficient way to fabricate high-performance electrodes for rechargeable batteries. Furthermore, CNFs fabricated at a carbonization temperature of 800 °C delivered the highest capacity, and the addition of MoS₂ improved the reversible capacity up to 860 mAh/g and 455 mAh/g for Li- and Na-ion batteries, respectively. A specific capacity of over 380 mAh/g was observed even at a high current density of 1 A/g. Centrifugal spinning and hydrothermal synthesis allowed for the fabrication of high-performance electrodes for sodium ion batteries.

Cu-supported nitrogen-doped carbon nanofibers with hierarchical three-dimensional net structure as binder-free anodes for enhanced lithium-ion batteries

Cu-supported nitrogen-doped carbon nanofibers (NCNFs) were fabricated via electrospinning and subsequent activation treatment with poly vinylpyrrolidone as both carbon and nitrogen sources. The NCNFs are firmly adhered to Cu foil without any additional binder and form a hierarchical three-dimensional net structure, which could effectively shorten the diffusion paths for electrons and lithium ions, thus resulting in lower impedance and superior electrochemical properties. Additionally, NCNFs feature a amorphous carbon structure, N-rich carbon lattice and wide pore distribution, not only ensuring fast ions/electrons transport, but also giving rise to the higher energy density. When directly used as a binder-free electrode, NCNFs deliver a high reversible capacity of 617.8 mAh g^-1 at 200 mA g^-1 after 100 cycles and maintain a superior capacity of 274.1 mAh g^-1 at 1.44 A g^-1 even after 500 cycles. Besides, the reversible capacity up to 216.5 mAh g^-1 can be still obtained at a high current density of 6 A g^-1, demonstrating the excellent high-rate cyclability. The facile synthesis approach and superior electrochemical properties make NCNFs electrodes an alternative anode candidate for lithium-ion batteries.

Electrospun Nanomaterials for Energy Applications: Recent Advances

Electrospinning is a simple, versatile, cost-effective, and scalable technique for the growth of highly porous nanofibers. These nanostructures, featured by high aspect ratio, may exhibit a large variety of different sizes, morphologies, composition, and physicochemical properties. By proper post-spinning heat treatment(s), self-standing fibrous mats can also be produced. Large surface area and high porosity make electrospun nanomaterials (both fibers and three-dimensional fiber networks) particularly suitable to numerous energy-related applications. Relevant results and recent advances achieved by their use in rechargeable lithium- and sodium-ion batteries, redox flow batteries, metal-air batteries, supercapacitors, reactors for water desalination via capacitive deionization and for hydrogen production by water splitting, as well as nanogenerators for energy harvesting, and textiles for energy saving will be presented and the future prospects for the large-scale application of electrospun nanomaterials will be discussed.

Reduced Graphene Oxide-Incorporated SnSb@CNF Composites as Anodes for High-Performance Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries because of the low cost and natural abundance of sodium resources. Nevertheless, low energy density and poor cycling stability of current SIBs unfavorably hinder their practical implementation for the smart power grid and stationary storage applications. Antimony tin (SnSb) is one of the most promising anode materials for next-generation SIBs attributing to its high capacity, high abundance, and low toxicity. However, the practical application of SnSb anodes in SIBs is currently restricted because of their large volume changes during cycling, which result in serious pulverization and loss of electrical contact between the active material and the carbon conductor. Herein, we apply reduced graphene oxide (rGO)-incorporated SnSb@carbon nanofiber (SnSb@rGO@CNF) composite anodes in SIBs that can sustain their structural stability during prolonged charge-discharge cycles. Electrochemical performance results shed light on that the combination of rGO, CNF, and SnSb alloy led to a high-capacity anode (capacity of 490 mAh g^-1  at the 10th cycle) with a high capacity retention of 87.2% and a large Coulombic efficiency of 97.9% at the 200th cycle. This work demonstrates that the SnSb@rGO@CNF composite is a potential and attractive anode material for next-generation, high-energy SIBs.

Nanostructured Electrospun Hybrid Graphene/Polyacrylonitrile Yarns

Novel nanostructured hybrid electrospun polyacrylonitrile (PAN) yarns with different graphene ratios were prepared using liquid crystal graphene oxide (LCGO) and PAN. It was found that the well-dispersed LCGO were oriented along the fiber axis in an electrified thin liquid jet during electrospinning. The graphene oxide sheets were well dispersed in the polar organic solvent, forming nematic liquid crystals upon increasing concentration. Twisted nanofibers were produced from aligned nanofibrous mats prepared by conventional electrospinning. It was found that the mechanical properties of the twisted nanofiber yarns increased even at very low LCGO loading. This research offers a new approach for the fabrication of continuous, strong, and uniform twisted nanofibers which could show promise in developing a novel carbon fiber precursor.

Vertically Aligned and Interconnected Boron Nitride Nanosheets for Advanced Flexible Nanocomposite Thermal Interface Materials

The continuous evolution toward semiconductor technology in the "more-than-Moore" era and rapidly increasing power density of modern electronic devices call for advanced thermal interface materials (TIMs). Here, we report a novel strategy to construct flexible polymer nanocomposite TIMs for advanced thermal management applications. First, aligned polyvinyl alcohol (PVA) supported and interconnected 2D boron nitride nanosheets (BNNSs) composite fiber membranes were fabricated by electrospinning. Then, the nanocomposite TIMs were constructed by rolling the PVA/BNNS composite fiber membranes to form cylinders and subsequently vacuum-assisted impregnation of polydimethylsiloxane (PDMS) into the porous cylinders. The nanocomposite TIMs not only exhibit a superhigh through-plane thermal conductivity enhancement of about 10 times at a low BNNS loading of 15.6 vol % in comparison with the pristine PDMS but also show excellent electrical insulating property (i.e., high volume electrical resistivity). The outstanding thermal management capability of the nanocomposite TIMs was practically confirmed by capturing the surface temperature variations of a working LED chip integrated with the nanocomposite TIMs.

Effects of composition and structure on the performance of tin/graphene-containing carbon nanofibers for Li-ion anodes

We use structure–composition relationships to engineer tin-containing nanofibers for Li-ion anodes that retain their capacities over 900 cycles.

Graphene-based materials for tissue engineering

Graphene and its chemical derivatives have been a pivotal new class of nanomaterials and a model system for quantum behavior. The material's excellent electrical conductivity, biocompatibility, surface area and thermal properties are of much interest to the scientific community. Two-dimensional graphene materials have been widely used in various biomedical research areas such as bioelectronics, imaging, drug delivery, and tissue engineering. In this review, we will highlight the recent applications of graphene-based materials in tissue engineering and regenerative medicine. In particular, we will discuss the application of graphene-based materials in cardiac, neural, bone, cartilage, skeletal muscle, and skin/adipose tissue engineering. We will also discuss the potential risk factors of graphene-based materials in tissue engineering. In conclusion, we will outline the opportunities in the usage of graphene-based materials for clinical applications.

Flexible hierarchical membranes of WS2 nanosheets grown on graphene-wrapped electrospun carbon nanofibers as advanced anodes for highly reversible lithium storage

It is still very challenging to achieve effective combination of carbon nanofibers and graphene sheets. In this study, a novel and facile method is developed to prepare flexible graphene/carbon nanofiber (GCNF) membranes with every carbon nanofiber wrapped by conductive graphene sheets, resulting in a remarkable improvement of their electrical conductivity. This method only entails a moderate process of soaking the pre-oxidized electrospun polyacrylonitrile (oPAN) nanofiber membranes in graphene oxide (GO) aqueous dispersion, and subsequent carbonization of the GO/oPAN hybrid membranes. By using the highly conductive GCNF membrane as a template, hierarchical WS₂/GCNF hybrid membranes with few-layer WS₂ nanosheets uniformly grown on GCNF nanofibers were fabricated as high-performance anodes for lithium ion batteries. Benefiting from the synergistic effects of GCNF nanofibers and WS₂ nanosheets, the resulting WS₂/GCNF hybrid membranes possessed a porous structure, large specific surface area, high electrical conductivity and good structural integrity, which are favorable for the rapid diffusion of lithium ions, fast transfer of electrons and overall electrochemical stability. As a result, the optimized WS₂/GCNF hybrid membrane exhibited a high initial charge capacity of 1128.2 mA h g^-1 at a current density of 0.1 A g^-1 and outstanding cycling stability with 95% capacity retention after 100 cycles.