Facile synthesis of hierarchical networks composed of highly interconnected V2O5 nanosheets assembled on carbon nanotubes and their superior lithium storage properties

2D/1D V2O5 Nanoplates Anchored Carbon Nanofibers as Efficient Separator Interlayer for Highly Stable Lithium-Sulfur Battery

Quick capacity loss due to the polysulfide shuttle effects is a critical challenge for high-performance lithium-sulfur (Li-S) batteries. Herein, a novel 2D/1D V2O5 nanoplates anchored carbon nanofiber (V-CF) interlayer coated on standard polypropylene (PP) separator is constructed, and a stabilization mechanism derived from a quasi-confined cushion space (QCCS) that can flexibly accommodate the polysulfide utilization is demonstrated. The incorporation of the V-CF interlayer ensures stable electron and ion pathway, and significantly enhanced long-term cycling performances are obtained. A Li-S battery assembled with the V-CF membrane exhibited a high initial capacity of 1140.8 mAh·g-1 and a reversed capacitance of 1110.2 mAh·g-1 after 100 cycles at 0.2 C. A high reversible capacity of 887.2 mAh·g-1 is also maintained after 500 cycles at 1 C, reaching an ultra-low decay rate of 0.0093% per cycle. The excellent electrochemical properties, especially the long-term cycling stability, can offer a promising designer protocol for developing highly stable Li-S batteries by introducing well-designed fine architectures to the separator.

3D Interconnected V6O13 Nanosheets Grown on Carbonized Textile via a Seed-Assisted Hydrothermal Process as High-Performance Flexible Cathodes for Lithium-Ion Batteries

Three-dimensional (3D) free-standing nanostructured materials have been proven to be one of the most promising electrodes for energy storage due to their enhanced electrochemical performance. And they are also widely studied for the wearable energy storage systems. In this work, interconnected V₆O₁₃ nanosheets were grown on the flexible carbonized textile (c-textile) via a seed-assisted hydrothermal method to form a 3D free-standing electrode for lithium-ion batteries (LIBs). The electrode exhibited a specific capacity of 170 mA h g^-1 at a specific current of 300 mA g^-1. With carbon nanotube (CNT) coating, its specific capacities further increased 12-40% at the various current rates. It could retain a reversible capacity of 130 mA h g^-1, 74% of the initial capacity after 300 cycles at the specific current of 300 mA g^-1. It outperformed most of the mixed-valence vanadium oxides. The improved electrochemical performance was ascribed to the synergistic effect of the 3D nanostructure of V₆O₁₃ for feasible Li⁺ diffusion and transport and highly conductive hierarchical conductive network formed by CNT and carbon fiber in c-textile.

Hierarchically Nanostructured Transition Metal Oxides for Lithium-Ion Batteries

Lithium-ion batteries (LIBs) have been widely used in the field of portable electric devices because of their high energy density and long cycling life. To further improve the performance of LIBs, it is of great importance to develop new electrode materials. Various transition metal oxides (TMOs) have been extensively investigated as electrode materials for LIBs. According to the reaction mechanism, there are mainly two kinds of TMOs, one is based on conversion reaction and the other is based on intercalation/deintercalation reaction. Recently, hierarchically nanostructured TMOs have become a hot research area in the field of LIBs. Hierarchical architecture can provide numerous accessible electroactive sites for redox reactions, shorten the diffusion distance of Li-ion during the reaction, and accommodate volume expansion during cycling. With rapid research progress in this field, a timely account of this advanced technology is highly necessary. Here, the research progress on the synthesis methods, morphological characteristics, and electrochemical performances of hierarchically nanostructured TMOs for LIBs is summarized and discussed. Some relevant prospects are also proposed.

V2O5-Based nanomaterials: synthesis and their applications

Comprehensive depiction the phase-pure V₂O₅ with unique 1D, 2D, and 3D nanostructures. Illustrate the development of carbonaceous materials into the V₂O₅ electrodes. Introduce the cation doped V₂O₅ samples as the cathode material.

Preparation of Lithium Titanate/Reduced Graphene Oxide Composites with Three-Dimensional "Fishnet-Like" Conductive Structure via a Gas-Foaming Method for High-Rate Lithium-Ion Batteries

With use of ammonium chloride (NH₄Cl) as the pore-forming agent, three-dimensional (3D) "fishnet-like" lithium titanate/reduced graphene oxide (LTO/G) composites with hierarchical porous structure are prepared via a gas-foaming method. Scanning electron microscopy and transmission electron microscopy images show that, in the composite prepared with the NH₄Cl concentration of 1 mg mL^-1 (1-LTO/G), LTO particles with sizes of 50-100 nm disperse homogeneously on the 3D "fishnet-like" graphene. The nitrogen-sorption analyses reveal the existence of micro-/mesopores, which is attributed to the introduction of NH₄Cl into the gap between the graphene sheets that further decomposes into gases and produces hierarchical pores during the thermal treatment process. The loose and porous structure of 1-LTO/G composites enables the better penetration of electrolytes, providing more rapid diffusion channels for lithium ion. As a result, the 1-LTO/G electrode delivers an ultrahigh specific capacity of 176.6 mA h g^-1 at a rate of 1 C. Even at 3 and 10 C, the specific capacity can reach 167.5 and 142.9 mA h g^-1, respectively. Moreover, the 1-LTO/G electrode shows excellent cycle performance with 95.4% capacity retention at 10 C after 100 cycles. The results demonstrate that the LTO/G composite with these properties is one of the most promising anode materials for lithium-ion batteries.

CTAB-Aided Synthesis of Stacked V2O5 Nanosheets: Morphology, Electrochemical Features and Asymmetric Device Performance

To accomplish superior performance in supercapacitors, a fresh class of electrode materials with advantageous structures is essential. Owing to its rich electrochemical activity, vanadium oxides are considered to be an attractive electrode material for energy storing devices. In this work, vanadium pentoxide (V2O[Formula: see text] nanostructures were prepared using surfactant (CTAB)-assisted hydrothermal route. Stacked V2O5 sheets enable additional channels for electrolyte ion intercalation. These stacked V2O5 nanosheets show highest specific capacitance of 466[Formula: see text]Fg[Formula: see text] at 0.5[Formula: see text]Ag[Formula: see text]. In addition, it exhibits good rate capacity, lower value of charge transfer resistance and good stability when used as an electrode material for supercapacitors. Further, an asymmetric supercapacitor device was assembled utilizing the stacked V2O5 sheets and activated carbon as electrodes. The electrochemical features of the device are also discussed.

Strategies for improving the lithium-storage performance of 2D nanomaterials

2D nanomaterials, including graphene, transition metal oxide (TMO) nanosheets, transition metal dichalcogenide (TMD) nanosheets, etc., have offered an appealing and unprecedented opportunity for the development of high-performance electrode materials for lithium-ion batteries (LIBs). Although significant progress has been made on 2D nanomaterials for LIB applications in the recent years, some major challenges still exist for the direct use of these sheet-like nanomaterials, such as their serious self-agglomerating tendency during electrode fabrication and low conductivity as well as the large volume changes over repeated charging–discharging cycles for most TMOs/TMDs, which have resulted in large irreversible capacity, low initial Coulombic efficiency and fast capacity fading. To address these issues, considerable progress has been made in the exploitation of 2D nanosheets for enhanced lithium storage. In this review, we intend to summarize the recent progress on the strategies for enhancing the lithium-storage performance of 2D nanomaterials, including hybridization with conductive materials, surface/edge functionalization and structural optimization. These strategies for manipulating the structures and properties of 2D nanomaterials are expected to meet the grand challenges for advanced nanomaterials in clean energy applications and thus provide access to exciting materials for achieving high-performance next-generation energy-storage devices.

Solution-phase synthesis of transition metal oxide nanocrystals: Morphologies, formulae, and mechanisms

In this review, we provide a broad overview of solution-phase synthesis of transition metal oxide nanocrystals (NCs), including a substantial catalog of published methods, and a unifying classification and discussion. Prevalent subcategories of solution-phase synthesis are delineated and general features are summarized. The diverse morphologies achievable by solution-phase synthesis are defined and exemplified. This is followed by sequential consideration of the solution-phase synthesis of first-row transition metal oxides. The common oxides of Ti, V, Mn, Fe, Co, Ni, Cu, and Zn are introduced; major crystal lattices are presented and illustrated; representative examples are explained; and numerous synthesis formulae are tabulated. Following this presentation of experimental studies, we present an introduction to theories of NC nucleation and growth. Various models of NC nucleation and growth are addressed, and important concepts determining the growth and structure of colloidal NCs are explained. Overall, this review provides an entry into systematic understanding of solution-phase synthesis of nanocrystals, with a reasonably comprehensive survey of results for the important category of transition metal oxide NCs.

Low-Cost and Facile Synthesis of the Vanadium Oxides V2O3, VO2, and V2O5 and Their Magnetic, Thermochromic and Electrochromic Properties

In this study, vanadium sesquioxide (V₂O₃), dioxide (VO₂), and pentoxide (V₂O₅) were all synthesized from a single polyol route through the precipitation of an intermediate precursor: vanadium ethylene glycolate (VEG). Various annealing treatments of the VEG precursor, under controlled atmosphere and temperature, led to the successful synthesis of the three pure oxides, with sub-micrometer crystallite size. To the best of our knowledge, the synthesis of the three oxides V₂O₅, VO₂, and V₂O₃ from a single polyol batch has never been reported in the literature. In a second part of the study, the potentialities brought about by the successful preparation of sub-micrometer V₂O₅, VO₂, and V₂O₃ are illustrated by the characterization of the electrochromic properties of V₂O₅ films, a discussion about the metal to insulator transition of VO₂ on the basis of in situ measurements versus temperature of its electrical and optical properties, and the characterization of the magnetic transition of V₂O₃ powder from SQUID measurements. For the latter compound, the influence of the crystallite size on the magnetic properties is discussed.

A V2O5 nanorod decorated graphene/polypyrrole hybrid electrode: a potential candidate for supercapacitors

Electron hopping conduction of V₂O₅ nanorod draped graphene/polypyrrole hybrid electrode materials for supercapacitor applications.

Controllable Preparation of V2O5/Graphene Nanocomposites as Cathode Materials for Lithium-Ion Batteries

Transition metal oxides and graphene composites have been widely reported in energy storage and conversion systems. However, the controllable synthesis of graphene-based nanocomposites with tunable morphologies is far less reported. In this work, we report the fabrication of V₂O₅ and reduced graphene oxide composites with nanosheet or nanoparticle-assembled subunits by adjusting the solvothermal solution. As cathode materials for lithium-ion batteries, the nanosheet-assembled V₂O₅/graphene composite exhibits better rate capability and long-term cycling stability. The V₂O₅/graphene composites can deliver discharge capacities of 133, 131, and 122 mAh g^-1 at 16 C, 32 C, and 64 C, respectively, in the voltage range of 2.5-4.0 V vs. Li/Li⁺. Moreover, the electrodes can retain 85% of their original capacity at 1C rate after 500 cycles. The superior electrochemical performances are attributed to the porous structures created by the connected V₂O₅ nanosheets and the electron conductivity improvement by graphene.

Carbon-Encapsulated Hollow Porous Vanadium-Oxide Nanofibers for Improved Lithium Storage Properties

Carbon-encapsulated hollow porous vanadium-oxide (C/HPV2O5) nanofibers have been fabricated using electrospinning and postcalcination. By optimized postcalcination of vanadium-nitride and carbon-nanofiber composites at 400 °C for 30 min, we synthesized a unique architecture electrode with interior void spaces and well-defined pores as well as a uniform carbon layer on the V2O5 nanofiber surface. The optimized C/HPV2O5 electrode postcalcined at 400 °C for 30 min showed improved lithium storage properties with high specific discharge capacities, excellent cycling durability (241 mA h g(-1) at 100 cycles), and improved high-rate performance (155 mA h g(-1) at 1000 mA g(-1)), which is the highest performance in comparison with previously reported V2O5-based cathode materials. The improved electrochemical feature is due to the attractive properties of the carbon-encapsulated hollow porous structure: (I) excellent cycling durability with high specific capacity relative to the adoption of carbon encapsulation as a physical buffer layer and the effective accommodation of volume changes due to the hollow porous structure, (II) improved high-rate performance because of a shorter Li-ion diffusion pathway resulting from interior void spaces and well-defined pores at the surface. This unique electrode structure can potentially provide new cathode materials for high-performance lithium-ion batteries.

Structural and toxic effect investigation of vanadium pentoxide

A facile inorganic complex synthesis route has been developed to synthesis V2O5 nanostructures. The effects of varying incubation time on the crystallinity and morphology of the V2O5 phase has been investigated. The obtained XRD result clearly revealed the pure orthorhombic V2O5 crystalline phase. Raman antiphase bridging VO and chaining VO stretching modes peaks at 686 and 521cm(-1) attributed orthorhombic V2O5 characteristics. The V2p3/2 peak at the binding energies of 517eV and V2p1/2 peak at 524eV assigned to V(5+) oxidation state. Bioinspired V2O5 nanostructures as a biocompatible material for anticancer agents show excellent cytotoxicity at higher V2O5 concentration.

Correlating Lithium Hydroxyl Accumulation with Capacity Retention in V2O5 Aerogel Cathodes

V2O5 aerogels are capable of reversibly intercalating more than 5 Li(+)/V2O5 but suffer from lifetime issues due to their poor capacity retention upon cycling. We employed a range of material characterization and electrochemical techniques along with atomic pair distribution function, X-ray photoelectron spectroscopy, and density functional theory to determine the origin of the capacity fading in V2O5 aerogel cathodes. In addition to the expected vanadium redox due to intercalation, we observed LiOH species that formed upon discharge and were only partially removed after charging, resulting in an accumulation of electrochemically inactive LiOH over each cycle. Our results indicate that the tightly bound water that is necessary for maintaining the aerogel structure is also inherently responsible for the capacity fade.

Lattice Breathing Inhibited Layered Vanadium Oxide Ultrathin Nanobelts for Enhanced Sodium Storage

Operating as the "rocking-chair" battery, sodium ion battery (SIB) with acceptable high capacity is a very promising energy storage technology. Layered vanadium oxide xerogel exhibits high sodium storage capacity. But it undergoes large lattice breathing during sodiation/desodiation, resulting in fast capacity fading. Herein, we develop a facile hydrothermal method to synthesize iron preintercalated vanadium oxide ultrathin nanobelts (Fe-VOx) with constricted interlayer spacing. Using the Fe-VOx as cathode for SIB, the lattice breathing during sodiation/desodiation is largely inhibited and the interlayer spacing is stabilized for reversible and rapid Na(+) insertion/extraction, displaying enhanced cycling and rate performance. This work presents a new strategy to reduce the lattice breathing of layered materials for enhanced sodium storage through interlayer spacing engineering.

Synergetic effects of Al3+ doping and graphene modification on the electrochemical performance of V2O5 cathode materials

A series of V2O5-based cathode materials that include V2O5 and Al0.14 V2O5 nanoparticles, V2O5/reduced graphene oxide (RGO), and Al0.16 V2O5/RGO nanocomposites are prepared by a simple soft chemical method. XRD and Raman scattering show that the Al ions reside in the interlayer space of the materials. These doping ions strengthen the V−O bonds of the [VO5] unit and enhance the linkage of the [VO5] layers, which thus increases the structural stability of V2O5. SEM and TEM images show that the V2O5 nanoparticles construct a hybrid structure with RGO that enables fast electron transport in the electrode matrix. The electrochemical properties of the materials are studied by charge-discharge cycling, cyclic voltammetry, and electrochemical impedance spectroscopy. Of all the materials tested, the one that contained both Al ions and RGO (Al0.16 V2O5/RGO) exhibited the highest discharge capacity, the best rate capability, and excellent capacity retention. The superior electrochemical performance is attributed to the synergetic effects of Al(3+) doping and RGO modification, which not only increase the structural stability of the V2O5 lattice but also improve the electrochemical kinetics of the material.

Interpenetrating network V2O5 nanosheets/carbon nanotubes nanocomposite for fast lithium storage

An interpenetrating V₂O₅ nanosheets/CNTs nanocomposite was fabricated by a freeze-drying method. The nanocomposite has excellent electrochemical properties for fast lithium storage.

A Bowknot-like RuO2 quantum dots@V2O5 cathode with largely improved electrochemical performance

A Bowknot-like RuO₂ quantum dots@V₂O₅ cathode exhibits superior rate capability and cycling stability.

Carbon nanotube-penetrated mesoporous V2O5 microspheres as high-performance cathode materials for lithium-ion batteries

A three-dimensional nanoarchitecture consisting of mesoporous V₂O₅ and penetrating CNTs was synthesized for high-performance lithium-ion batteries.