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With a theoretically high capacity and suitable discharge/charge plateaus, lithium vanadates (such as Li 0.04 V 2 O 5 ) can be used as cathode material for lithium ion batteries. Herein, Li 0.04 V 2 O 5 nanowires are densely anchored onto reduced graphene oxide (rGO) nanosheets to form a Li 0.04 V 2 O 5 @rGO nanocomposite by a hydrothermal method with subsequent thermal treatment. Due to this unique structure, the Li 0.04 V 2 O 5 @rGO exhibits remarkable rate performance and excellent cycling stability. Specifically, it delivers a reversible discharge capacity of 738.09 mA h g −1 at a current density of 100 mA g −1 in the voltage range of 2.0–4.0 V. After 500 cycles, it still maintains a high capacity of 731.70 mA h g −1 , which represents 95.01% retention of the original reversible capacity. These results indicate that the Li 0.04 V 2 O 5 @rGO could be a promising candidate as cathode active material for long-term cycling performance in lithium-ion batteries. [ABSTRACT FROM AUTHOR]

A facile and scalable strategy, based on a hydrothermal route, has been applied to fabricate potassium vanadate (KVO) nanowires on Ti fabric. The morphology, crystal structure, chemical composition of the prepared sample are tested and presented in detail. When tested as cathode materials for lithium-ion batteries, the flexible KVO electrode has a high reversible capacity of 270 mAh g −1 at a current density of 100 mA g −1 after 300 cycles. Furthermore, the KVO delivers outstanding rate behavior, even at 960 mA g −1 , a reversible capacity as high as 214.1 mAh g −1 can be retained. The superior electrochemical performance suggests that the KVO nanowires on Ti fabric can be as a potential cathode candidate for flexible rechargeable lithium-ion batteries. [ABSTRACT FROM AUTHOR]

• Metallic Co nanoparticles are in-situ deposited into the discharged TiO 2 nanotube array. • After calcination, the resulting TiO 2 @Co composite has excellent ferromagnetic properties. • The maximum saturation magnetization of TiO 2 @Co composite is 15.85 emu/g. Titanium oxide (TiO 2) nanotube array is prepared by an anodization method, and the TiO 2 nanotube array and a lithium foil are used as working and counter electrodes, respectively, to assemble a lithium-ion battery. After discharge to 0.01 V, the TiO 2 nanotube array is reducible. Metallic Co nanoparticles are in-situ deposited into the discharged TiO 2 nanotube array in saturated cobalt acetate in N-N dimethylformamide solution for the first time. The sample exhibits enhanced magnetic properties after calcination at 500 °C in a reducing agent. The morphology, structure and magnetic properties of the samples are characterized and analyzed in detail. This work provides a new method for the synthesis of one-dimensional functional materials by using TiO 2 nanotube array template. [ABSTRACT FROM AUTHOR]

Abstract Manganese vanadate (Mn 2 V 2 O 7) nanosheets on titanium (Ti) foil are synthesized by a cation-exchange method using sodium vanadate nanowires as the precursor. By varying the cation-exchange time in manganese acetate (Mn(CH 3 COO) 2) aqueous solution, the tunable morphologies and chemical components of the samples are tested, compared and presented in detail. The evolution process contains cation-exchange of Mn2+ and Na+, newly generated H+ to dissolve vanadate, and precipitation manganese vanadate nanosheets on the original sodium vanadate nanowire surface. Furthermore, the thermal and crystal properties of the as-prepared nanosheets are evaluated by calcinations at different temperatures. The Mn 2 V 2 O 7 nanosheets obtained at 250 °C, which are used as electrode of lithium-ion battery, have the first discharge capacity of 1048.0 mAh g−1 at 50 mA g−1. After 100 cycles, the residual capacity is more than 800 mAh g−1. Graphical abstract Manganese vanadate nanosheets on titanium foil are successfully assembled using a cation-exchange method for the first time. As an electrode material, it presents good cyclic performance and high charge-discharge capacity. Image 1 Highlights • Manganese vanadate nanosheets are successfully prepared using a cation-exchange method. • Manganese vanadate nanosheets on titanium foil present a high electrochemical performance for lithium ion battery. • The evolution in this work opens a new way to fabricate inorganic vanadates. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Iron vanadate nanowires were firstly synthesized by a cation-exchange routine. • Well-dispersed porous iron vanadate nanowires firmly anchored on Ti foil. • The iron vanadate nanowires exhibit superior lithium storage capability. • The charge-discharge process prefers to pseudocapacitive-controlled behavior. Abstract The nanostructuring of materials can solve the problem of low conductivity of the vanadate electrode, thereby increasing the potential for lithium storage performance. The traditional battery is prepared by coating active materials on current collector, which produces large contact resistance between the current collector and the electrodes, impeding the overall electrochemical performances of the battery. In this work, we propose and verify a scheme for directly loading porous iron vanadate nanowire array electrode on titanium foil. The resultant electrode (the as-prepared iron vanadate annealed at 300 °C) exhibits an enhanced lithium storage performance, the discharge capacity after 100 cycles is 1041.10 mAh·g−1 at a current density of 300 mA·g−1. The iron vanadate nanowire electrode is fabricated by a simple and scalable cation-exchange method, which can be provided for the separate and integrated large-scale industrialization of vanadate electrode materials. [ABSTRACT FROM AUTHOR]

Highlights • The β-Na 0.33 V 2 O 5 nanowires were obtained by an electrodeposited-hydrothermal method. • We have synthesized β-Na 0.33 V 2 O 5 nanowire film with high tap density. • The thickness of the β-Na 0.33 V 2 O 5 nanowires is ∼10.5 μm at 5 h, 2.5 V, 90 °C. • The β-Na 0.33 V 2 O 5 @PPy maintains a capacity of 241.7 mAh g−1 after 50 circulations. Abstract A novel electrodeposited-hydrothermal method has been developed to fabricate high-density β-Na 0.33 V 2 O 5 nanowire film on a metal current collector (Ti foil). The morphology, crystal structure, and the effects of deposition voltage, temperature and time on the prepared samples were tested and presented in detail. The thickness of the β-Na 0.33 V 2 O 5 nanowire film was ∼10.5 μm under experimental conditions of 5 h time, 2.5 V voltage, and 90 °C temperature. When the β-Na 0.33 V 2 O 5 nanowire film was coated with polypyrrole and served as a cathode of lithium-ion battery, it exhibited a high reversible discharge capacity of 269.9 mAh g−1 at a current density of 50 mA g−1. By contrast, the cycling behavior of this material is proved to be much better than the bare β-Na 0.33 V 2 O 5 nanowire film. This research provides a new pathway to explore high tap density cathode materials for lithium-ion battery with enhanced electrochemical performance. [ABSTRACT FROM AUTHOR]

Abstract Silver vanadate (Ag 4 V 2 O 7) nanowires are synthesized through a simple and facile cation exchange method, and the silver vanadate/silver (Ag/Ag 0.68 V 2 O 5) nanowires are obtained through calcination of Ag 4 V 2 O 7 nanowires at 250-500 °C. By varying the reaction time, the progression of the cation exchange process is captured, and tunable morphologies, crystal structures and chemical components (Ag, V, Na and O) of the samples are achieved and analyzed using scanning electron microscope, transmission electron microscope, X-ray diffraction and X-ray photoelectron spectroscopy, respectively. Also, as an electrode of lithium-ion battery, the Ag/Ag 0.68 V 2 O 5 nanowires exhibit specific discharge capacities of 179.5 mAh g−1 in the first cycle and 152.6 mAh g−1 at the 150th cycle at a current density of 30 mA g−1. Good lithium-ion storage performance of the electrode mainly due its nanowire structure directly grown on titanium foil and good electron transportation caused by the high conductivity of the silver nanoparticles in the nanowires. Graphical abstract Unlabelled Image Highlights • The Ag/Ag 0.68 V 2 O 5 nanowires are fabricated via a cation-exchange reaction. • The silver particles on the nanowires improve the conductivity of the whole electrode. • The Ag/Ag 0.68 V 2 O 5 nanowires maintain a capacity of 146.1 mAh g−1 after 100 cycles. [ABSTRACT FROM AUTHOR]

Polyaniline (PANI) nanowire arrays have been prepared for the first time using Na5V12O32 nanowires as a sacrificial template. Fourier-transformed infrared spectroscopy and energy-dispersive X-ray spectroscopy were used to characterize the as-prepared PANI nanowire arrays. Further, the electrochemical properties of the PANI nanowire arrays for lithium-ion batteries were investigated with cyclic voltammetry, galvanostatic charge-discharge experiment, and rate performance. It delivered a high discharge capacity of 119.79 mA h g−1 after 100 cycles between 2.0 and 4.0 V at 30 mA g−1. [ABSTRACT FROM AUTHOR]

Lithium vanadate nanowires have been electrodeposited onto a titanium (Ti) foil by a direct current electrodeposition without template. The morphology, crystal structure, and the effects of deposition voltage, temperature and time on the prepared samples were tested and presented. The as-prepared lithium vanadate nanowires/Ti composite can be used as electrode for lithium-ion battery. Electrochemical measurements showed that the electrode displayed a specific discharge capacitance as high as 235.1 mAh g −1 after 100 cycles at a current density of 30 mA g −1 . This research provides a new pathway to explore high tap density vanadates nanowires on metals with enhanced electrochemical performance. [ABSTRACT FROM AUTHOR]

This paper reports a study on the electrochemical performance of vanadium trioxide (V 2 O 3 ) nanowire arrays as a cathode material for Li-ion battery. V 2 O 3 nanowire arrays are formed via thermal treatment of ammonium vanadium bronze (NH 4 V 4 O 10 ) nanowires in a 5% H 2 and 95% Ar atmosphere. X-ray diffraction confirms the thermal reduction. The V 2 O 3 nanowire arrays as an electrode of lithium-ion battery exhibit high reversible capacity and excellent long-term cycling stability. The discharge capacity increases from 243 to 428 mA h g −1 at the first 20 cycles. After 100 cycles, a stable capacity of 444 mA h g −1 is retained at a current density of 30 mA g −1 . [ABSTRACT FROM AUTHOR]

Design and fabrication of novel optimized electrode materials are important for the development of new batteries for energy storage applications. Herein, we report on a hierarchical bulk electrode material with a tailored nanostructure that which consists of three components: a NH 4 V 4 O 10 nanowire as an active skeleton, an intermediate polymer layer (polypyrrole, PPy), and a metal oxide layer (MnO 2 ) as the outside shell. The NH 4 V 4 O 10 -PPy-MnO 2 nanowires exhibit present higher capacitance than that of the simple NH 4 V 4 O 10 -PPy core@shell or NH 4 V 4 O 10 nanowires. The structure of double shells of combined PPy and MnO 2 is a key factor in enhancing their electrochemical performance including high specific capacitance and excellent cycling stability. Our V-based core@shell@shell structure can serve as freestanding, compressible electrodes for various energy devices. [ABSTRACT FROM AUTHOR]

Ammonium vanadate (NH 4 V 4 O 10 ) nanowire flowers and nanowires on titanium (Ti) foils are synthesized by hexamethylenetetramine (HMTA)-assisted hydrothermal reactions as a cathode material for lithium-ion battery. The as-prepared NH 4 V 4 O 10 nanowires are about 50 nm in diameter and several micrometers in length. The effects of reaction time, temperature and additive concentration on the resulting morphology are investigated. Reversible lithium intercalation behavior of the nanowires has been evaluated by cyclic voltammetry and galvanostatic discharge–charge cycling. The NH 4 V 4 O 10 nanowires on Ti foil deliver a high discharge capacity of 168.5 mA h g −1 after 100 cycles between 2.0 and 4.0 V at 50 mA g −1 . A high rate capability is obtained with a remaining discharge capacity of about 182.6 mA h g −1 after 35 cycles at various rates. Further, the NH 4 V 4 O 10 nanowires on Ti foil have a higher discharge capacity of 330.5 mA h g −1 after 100 cycles at 0.8–4.0 V at 50 mA g −1 . [ABSTRACT FROM AUTHOR]

BiVO 4 nanowire array is fabricated by a hydrothermal method, and the nanowire array and a lithium foil are used as working and counter electrodes, respectively, to assemble a lithium-ion battery. After charging to 4 V, the BiVO 4 nanowire array has a strong oxidizing property. The pyrrole can be in-situ polymerized on the surface of the charged BiVO 4 nanowire array to form a polypyrrole coating layer in pyrrole solution. The morphology and structure properties of the samples are characterized and analyzed in detail. The lithium storage performances of the samples are also measured and compared. The obtained BiVO 4 -PPy nanowires have stable cycle performance and a discharge capacity of more than 400 mAh g−1 after 50 cycles. This work provides a new method for synthesizing conductive polymers on charged electrodes. • A novel in-situ coating polypyrrole (PPy) on charged BiVO 4 nanowires method is used to improve the cycle performance of the electrode. • The obtained BiVO 4 -PPy nanowires have a capacity of more than 400 mAh g−1 at a current density of 100 mA g−1 after 50 cycles in 1–4 V. [ABSTRACT FROM AUTHOR]

In order to improve lithium storage capacity and cycle stability of the electrode materials, the combination of the active material and graphene is an effective way. Reduced graphene oxide (rGO) film on Ti substrate is obtained in an aqueous graphene oxide solution using a two-electrode constant voltage electrodeposition system. Then the rGO film on Ti substrate is used as working electrode to assemble lithium-ion batteries and discharged to 0.01 V. The discharged rGO film further reacts with cobalt ions in the cobalt acetate aqueous solution to fabricate the cobalt oxide (CoO)/rGO-precursor, and subsequently the CoO/rGO-700 composite is obtained by calcining the precursor at 700 °C under N 2. Different measurements are conducted to evaluate the samples. The CoO/rGO-700 composites are further used as electrode material of lithium-ion batteries, which deliver an initial capacity of 1290.6 mAh·g−1 at 100 mA·g−1. For the first time, the synthetic method reported in this work can be extended to the synthesis of other metal or oxide/rGO composites. Unlabelled Image • rGO film is successfully prepared by an electrodeposition method. • CoO nanoparticles are anchored on the discharged-graphene film successfully. • The CoO/rGO-700 composites deliver a reversible capacity of 1290.6 mAh·g−1 at 100 mA·g−1. [ABSTRACT FROM AUTHOR]