Nanowire Cathode Research Articles

Substrate-Assisted Self-Organization of Radial β-AgVO3Nanowire Clusters for High Rate Rechargeable Lithium Batteries

Rational assembly of unique complex nanostructures is one of the facile techniques to improve the electrochemical performance of electrode materials. Here, a substrate-assisted hydrothermal method was designed and applied in synthesizing moundlily like radial β-AgVO(3) nanowire clusters. Gravitation and F(-) ions have been demonstrated to play important roles in the growth of β-AgVO(3) nanowires (NWs) on substrates. The results of cyclic voltammetry (CV) measurement and X-ray diffraction (XRD) characterization proved the phase transformation from β-AgVO(3) to Ag(1.92)V(4)O(11) during the redox reaction. Further electrochemical investigation showed that the moundlily like β-AgVO(3) nanowire cathode has a high discharge capacity and excellent cycling performance, mainly due to the reduced self-aggregation. The capacity fading per cycle from 3rd to 51st is 0.17% under the current density of 500 mA/g, which is much better than 1.46% under that of 20 mA/g. This phenomenon may be related to the Li(+) diffusion and related kinetics of the electrode. This method is shown to be an effective and facile technique for improving the electrochemical performance for applications in rechargeable Li batteries or Li ion batteries.

Zinc Oxide Nanowire As an Electron-Extraction Layer for Broadband Polymer Photodetectors with an Inverted Device Structure

We report the fabrication of high-performance broadband polymer photodetectors based on narrow bandgap conjugated polymers with an inverted device structure, where electrons and holes are collected on indium tin oxide and metal contact with high work function. High-quality wide bandgap vertically aligned ZnO nanowire array offers an enhanced surface area and is used as the cathode buffer layer in this device for effectively extracting electrons and blocking holes from the active polymer layer. The room-temperature detectivity of polymer photodetectors with such an inverted device structure is greater than 1010 Jones with the spectral response from 400 to 1450 nm. Our results define a promising pathway for fabrication of high-sensitivity polymer photodetectors with an inverted device structure using ZnO nanowire array cathode buffer layer for a wide range of applications.

Topotactically synthesized ultralong LiV3O8 nanowire cathode materials for high-rate and long-life rechargeable lithium batteries

High-power applications at fast charge and discharge rates are still great challenges in the development of rechargeable lithium batteries. Here, we demonstrate that ultralong LiV3O8 nanowire cathode materials synthesized by topotactic Li intercalation present excellent high-rate and long-life performance. At the current density of 2000, mA g−1, the initial and the six-hundredth discharge capacities can reach 137 and 120 mAh g−1, respectively, corresponding to a capacity fading of only 0.022% per cycle. Such performance indicates that the topotactically synthesized ultralong LiV3O8 nanowires are promising cathode materials for high-rate and long-life rechargeable lithium batteries.

Study of the Influence of Transverse Velocity on the Design of Cold Cathode-Based Electron Guns for Terahertz Devices

This paper presents the design of an electron gun for terahertz vacuum tubes realized with a nanowire or nanotube cold cathode. This technology is particularly interesting in this field since it allows the reduction of gun dimensions and of power consumption with respect to the thermionic guns. We found that focusing is a rather critical aspect since cold cathodes show a relevant transverse velocity, which increases the divergence of the beam and typically induces high current losses on the anode. An analysis of the parameters that influence the transverse velocity has been performed together with the identification of a proper design procedure that reduces the transverse velocity effects. Different electron guns have been designed that deliver a circular beam in the range of 1–4 mA with a radius in the range of 30 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> .

High-Performance Li-ion Batteries and Supercapacitors Base on 1-D Nanomaterials in Prospect

One-dimensional (1-D) nanomaterials with superior specific capacity, higher rate capability, better cycling peroperties have demonstrated significant advantages for high-performance Li-ion batteries and supercapacitors. This review describes some recent developments on the rechargeable electrodes by using 1-D nanomaterials (such as LiMn2O4 nanowires, carbon nanofibers, NiMoO4 · nH2O nanorods, V2O5 nanoribbons, carbon nanotubes, etc.). New preparation methods and superior electrochemical properties of the 1-D nanomaterials including carbon nanotube (CNT), some oxides, transition metal compounds and polymers, and their composites are emphatically introduced. The VGCF/LiFePO4/C triaxial nanowire cathodes for Li-ion battery present a positive cycling performance without any degradation in almost theoretical capacity (160 mAh/g). The Si nanowire anodes for Li-ion battery show the highest known theoretical charge capacity (4277 mAh/g), that is about 11 times lager than that of the commercial graphite (∼372 mAh/g). The SWCNT/Ni foam electrodes for supercapacitor display small equivalent series resistance (ESR, 52 mΩ) and impressive high power density (20 kW/kg). The advantages and challenges associated with the application of these materials for energy conversion and storage devices are highlighted.

High-Performance Li-ion Batteries and Supercapacitors Based on Prospective 1-D Nanomaterials

Abstract One-dimensional (1-D) nanomaterials with superior specific capacity, higher rate capability, better cycling peroperties have demonstrated significant advantages for high-performance Li-ion batteries and supercapacitors. This review describes some recent developments on the rechargeable electrodes by using 1-D nanomaterials (such as LiMn2O4 nanowires, carbon nanofibers, NiMoO4 · nH2O nanorods, V2O5 nanoribbons, carbon nanotubes, etc.). New preparation methods and superior electrochemical properties of the 1-D nanomaterials including carbon nanotube (CNT), some oxides, transition metal compounds and polymers, and their composites are emphatically introduced. The VGCF/LiFePO4/C triaxial nanowire cathodes for Li-ion battery present a positive cycling performance without any degradation in almost theoretical capacity (160 mAh/g). The Si nanowire anodes for Li-ion battery show the highest known theoretical charge capacity (4277 mAh/g), that is about 11 times lager than that of the commercial graphite (∼372 mAh/g). The SWCNT/Ni foam electrodes for supercapacitor display small equivalent series resistance (ESR, 52 mΩ) and impressive high power density (20 kW/kg). The advantages and challenges associated with the application of these materials for energy conversion and storage devices are highlighted.

The rechargeable aluminum-ion battery

We report a novel aluminium-ion rechargeable battery comprised of an electrolyte containing AlCl(3) in the ionic liquid, 1-ethyl-3-methylimidazolium chloride, and a V(2)O(5) nano-wire cathode against an aluminium metal anode. The battery delivered a discharge capacity of 305 mAh g(-1) in the first cycle and 273 mAh g(-1) after 20 cycles, with very stable electrochemical behaviour.

Electrospun Ultralong Hierarchical Vanadium Oxide Nanowires with High Performance for Lithium Ion Batteries

Ultralong hierarchical vanadium oxide nanowires with diameter of 100-200 nm and length up to several millimeters were synthesized using the low-cost starting materials by electrospinning combined with annealing. The hierarchical nanowires were constructed from attached vanadium oxide nanorods of diameter around 50 nm and length of 100 nm. The initial and 50th discharge capacities of the ultralong hierarchical vanadium oxide nanowire cathodes are up to 390 and 201 mAh/g when the lithium ion battery cycled between 1.75 and 4.0 V. When the battery was cycled between 2.0 and 4.0 V, the initial and 50th discharge capacities of the nanowire cathodes are 275 and 187 mAh/g. Compared with self-aggregated short nanorods synthesized by hydrothermal method, the ultralong hierarchical vanadium oxide nanowires exhibit much higher capacity. This is due to the fact that self-aggregation of the unique nanorod-in-nanowire structures have been greatly reduced because of the attachment of nanorods in the ultralong nanowires, which can keep the effective contact areas of active materials, conductive additives, and electrolyte large and fully realize the advantage of nanomaterial-based cathodes. This demonstrates that ultralong hierarchical vanadium oxide nanowire is one of the most favorable nanostructures as cathodes for improving cycling performance of lithium ion batteries.

Direct growth of high-rate capability and high capacity copper sulfide nanowire array cathodes for lithium-ion batteries

A general solution method for the growth of highly ordered large-scale Cu2S nanowire arrays onto the copper metal current collector substrates has been developed. The electrochemical behaviors of Cu2S nanowire array cathodes for lithium-ion battery applications reveal that they exhibit stable lithium-ion insertion/extraction reversibility, high reversible lithium storage capacity, long cycle life and outstanding rate capability. The superb electrochemical performance can be attributed to the nanowire arrays having increased reaction sites, improved cycle life in the face of mechanical strain and efficient charge transport. With the simplicity of fabrication and good electrochemical properties, the Cu2S nanowire arrays are promising cathode materials for the practical use in the next generation lithium-ion batteries.

Efficient field emission from structured gold nanowire cathodes

Regular patch arrays of random gold nanostructures were fabricated by electrochemical deposition of nanowires in ion track-etched templates. During ion irradiation with GeV ions of fluence 10 6 , 10 7 , or 10 8 cm −2 , a shadow mask was used resulting in templates structured with square arrays of 50 μ m holes and 100 or 150 μ m pitch. The Au nanowires grown in the track-etched pores had a length of 7–28 μ m and a diameter of ~300 nm, and were either solitary or clustered after template dissolution. The structured wire ensembles were systematically investigated with scanning electron and field emission scanning microscopy. Field emission with about 90% efficiency was achieved for wide-spaced patch arrays with medium and high number of Au nanowires at 1500 V for 20 μ m anode distance. The current carrying capability of the patches strongly varied between 40 nA and 90 μ A. The corresponding processing effects are correlated to adsorbates and nanostructural changes of the wires which give suitable hints for the optimization of structured Au nanowire cathodes.

Synthesis of Nanowire and Hollow LiFePO4 Cathodes for High-Performance Lithium Batteries

The synthesis of nanowire and hollow LiFePO4 cathodes using the hard templates KIT-6 and SBA-15 is reported for high-performance lithium batteries. The two-dimensional hexagonal SBA-15 silica template with P6mm symmetry is used for the template that contains parallel cylindrical pores arranged with hexagonal symmetry, which serves to organize the wires into parallel bundles. On the other hand, three-dimensional cubic arrangement of pores in KIT-6 silica with Ia3d symmetry yields hollow morphology with mesopores. After impregnation of the template into a solution or after coating on the template with a solution consisting of LiFePO4 precursors, the silica template is removed and is subsequently fired at 700 °C. Electrochemical cycling of both the nanowire and hollow LiFePO4 cathodes demonstrates excellent rate capability even above 10C rate, showing >89% capacity retention of the initial capacity. Among them, the rate capability of the hollow cathode at 15C is higher than that of the nanowire cathode, show...

Transparent metallic Sb-doped SnO2 nanowires

The authors report the growth and characterization of single-crystalline, degenerately Sb-doped SnO2 (SnO2:Sb) nanowires. The in situ doped SnO2:Sb nanowires are transparent conductors with resistivities down to 4.1×10−4Ωcm and failure-current densities up to 2.1×107A∕cm2. High carrier concentrations (&amp;gt;1020cm−3) and minimal environmental effects were also observed and attributed to effective Sb doping. The SnO2:Sb nanowires can be obtained at large quantities using a low-cost vapor transport method and may provide a suitable alternative to indium tin oxide as transparent conducting oxide materials. Field emission devices with SnO2:Sb nanowire cathodes and anodes exhibited an ultralow turn-on voltage of 2V.