Vanadium Sulfide Research Articles

Synergistic engineering of heteroatomic N-doping and PPy modification in flower-like vanadium sulfide anode enables stable sodium storage

Vanadium sulfide, an appealing anode candidate for sodium ion batteries (SIBs), still encounters considerable volume fluctuation and sluggish Na+ diffusion kinetics, which inevitably gives rise to unsatisfactory rate capability and severe capacity decay. Herein, we successfully designed and constructed an outstanding sodium-storage feature and exceedingly stable anode for SIBs in the form of three-dimensional flower-like architecture composing of phosphorus doped VS2 wrapped by conductive elastic polypyrrole (PPy) layer (i.e., P-VS2@PPy). Through leveraging the multifunctional synergistic effect of composition and structure, involving enhanced electronic conductivity, reduced volumetric fluctuation, accelerated charge/ion transfer efficiency, and remarkable surface-capacitive behaviors can guarantee significantly enhanced electrochemical sodium-storage ability of P-VS2@PPy composites. As a consequence,such P-VS2@PPy is endowed with desirable rate characteristic accompanied with long-period cyclic lifespan (436.7 mAh/g at 20.0 A/g after 2600 cycles), which far outperform contrastive P-VS2 and pure VS2 samples. Meticulous kinetic analysis combined with theoretical simulations conclude that phosphorus doping and PPy coating have substantial effects on strengthening ionic and electron diffusion kinetics. Thorough examination and analysis of the insertion and conversion mechanisms of P-VS2@PPy was conducted through ex situ tests, revealing superior reversible phase transformation between original VS2, intermediate NaVS2, and final Na2S/V. Additionally, a practical application test demonstrates that sodium ion full-cell and hybrid capacitor based on P-VS2@PPy anode showcase significant capacity contribution and outstanding specific energy output, capable of effortlessly lighting up a LED screen.

Rational Fabrication of Nickel Vanadium Sulfide Encapsulated on Graphene as an Advanced Electrode for High-Performance Supercapacitors.

Supercapacitors (SCs) are widely recognized as competitive power sources for energy storage. The hierarchical structure of nickel vanadium sulfide nanoparticles encapsulated on graphene nanosheets (NVS/G) was fabricated using a cost-effective and scalable solvothermal process. The reaction contents of the composites were explored and optimized. TEM images displayed the nickel vanadium sulfide nanoparticles (NVS NPs) with 20-30 nm average size anchored to graphene nanosheets. The interconnection of graphene nanosheets encapsulating NVS nanoparticles effectively reduces the ion diffusion path between the electrode and electrolyte, thereby enhancing electrochemical performance. The NVS/G composite demonstrated improved electrochemical performance, achieving a maximum of 1437 F g-1 specific capacitance at 1 A g-1, remarkable rate capability retaining of 1050 F g-1 at 20 A g-1, and exceptional cycle stability with 91.2% capacitance retention following 10,000 cycles. The NVS/G composite was employed as a cathode, and reduced graphene oxide (rGO) was used as an anode material to assemble a device. Importantly, asymmetric SCs using NVS/G//rGO achieved 74.7 W h kg-1 energy density at 0.8 kW kg-1 power density, along with outstanding stability with 88.2% capacitance retention following 10,000 cycles. These superior properties of the NVS/G electrode highlight its significant potential in energy storage applications.

Vanadium sulfide decorated at carbon matrix as anode materials for “fast-charging” lithium-ion batteries

Vanadium sulfide is considered a promising electrode material for achieving rapid lithium storage ascribing to its high specific capacity, unique crystal structure, and abundant valence states. Unfortunately, the structural collapse induced by volume expansion during charging and discharging is the key factor affecting rapid lithium storage. This article prepares composite materials with different morphologies through a strategy of decorating vanadium sulfide at carbon matrix. Among them, graphene oxide modified vanadium tetrasulfide composite materials with three-dimensional conductive networks exhibit excellent electrochemical performance. When the current density is 50 mA g−1, the discharging specific capacity reaches 1, 560 mAh g−1. After 2, 500 cycles at a high current density of 10, 000 mA g−1, the specific capacity is about 188 mAh g−1 with charging time of approximately 70 s. GITT testing indicates that the order of magnitude of the logarithm of the initial diffusion coefficient is 10−11 cm2 s−1 owing to the three-dimensional porous conductive network, which not only shortens ion diffusion path but also provides more active sites for lithium-ion storage, rendering it a promising anode material for “fast-charging” lithium-ion batteries.

Cobalt-Doped Vanadium Sulfide Nanorods Anchored on Graphene for High-Performance Supercapacitors

Cobalt-Doped Vanadium Sulfide Nanorods Anchored on Graphene for High-Performance Supercapacitors

Nanotubes and other nanostructures of VS2, WS2, and MoS2: Structural effects on the hydrogen evolution reaction

Vanadium sulfide (VS2) is a layered transition metal dichalcogenide (TMD), comparable in crystal structure to the well-known MoS2 and WS2. Theoretical predictions attribute much potential to VS2, since it is metallic-like and has an active basal plane, essential for catalytic performance. However, it is much less studied than other members of the TMD family due to the difficulties in synthesizing specific structures with controlled properties. Here we present unique structures of VS2 nanotubes and conduct a comparative study with other well-known inorganic nanotubes and nanostructures of MoS2 and WS2. We evaluate the effect of the curvature and strain, the abundance of surface defects, and the availability of surface sites in various structures by electrochemical methods. We show that MoS2 has the best intrinsic activity, which is enhanced by an extensive electrochemical surface area. The woven-like structure of the MoS2 nanotube walls provides a combined effect of strain, crystallinity, and defects. For WS2 structures, the strained surface of the nanotubes results in sites with higher intrinsic activity than the edge sites, but structures such as the nano-triangles, which provide a higher number of edge sites, exhibit competing activity. As for the VS2 structures, although theoretical calculations predict optimal active sites for the hydrogen evolution reaction (HER), they are extremely sensitive to stoichiometry variations that hamper their catalytic activity. Our findings contribute insights to the improvement and design of VS2–based nanocatalysts for the HER and shed light on the general factors that govern the activity in the unique TMD nanotubes family.

Structure-modulation of flower-like VS2 via ammonium ion intercalation for high performance potassium-ion batteries

Transition vanadium sulfide is a promising anode material for potassium-ion batteries (PIBs), but the volume variation during charge-discharge cycling and low electric conductivity seriously hinder its applications. Herein, we designed a multilayer lamellar self-assembled flower-like vanadium sulfide with ammonium ion intercalation (VS2–NF) by a facile and inexpensive hydrothermal method to improve its electrochemical potassium ion storage performance. By introducing ammonia during the hydrothermal synthesis process, the structures of vanadium sulfide transformed to nanoflowers composed by ultrathin nanosheets from the initial nanosphere structures. The intercalation of ammonium ion enlarges the lattice fringes and induces anisotropic growth of vanadium sulfide, resulting in a large number of mesopores and increased specific surface area as well as the reactive sites of vanadium sulfide, which contribute to the enhanced potassium ion storage performance. Consequently, the structure-modulated VS2–NF exhibits a high specific capacity of 507 mAh g−1 after 50 cycles at a current density of 100 mA g−1. This approach provides a new routine for the modification of other transition metal disulfides as anode materials for PIBs.

Europium-Based Coordination Polymer-Modified Vanadium Sulfide Nanocomposite with High Photothermal Conversion Efficiency as a Powerful Photothermal and Four-Mode Imaging Technique

Europium-Based Coordination Polymer-Modified Vanadium Sulfide Nanocomposite with High Photothermal Conversion Efficiency as a Powerful Photothermal and Four-Mode Imaging Technique

2D Vanadium Sulfides: Synthesis, Atomic Structure Engineering, and Charge Density Waves.

Two ultimately thin vanadium-rich 2D materials based on VS2 are created via molecular beam epitaxy and investigated using scanning tunneling microscopy, X-ray photoemission spectroscopy, and density functional theory (DFT) calculations. The controlled synthesis of stoichiometric single-layer VS2 or either of the two vanadium-rich materials is achieved by varying the sample coverage and sulfur pressure during annealing. Through annealing of small stoichiometric single-layer VS2 islands without S pressure, S-vacancies spontaneously order in 1D arrays, giving rise to patterned adsorption. Via the comparison of DFT calculations with scanning tunneling microscopy data, the atomic structure of the S-depleted phase, with a stoichiometry of V4S7, is determined. By depositing larger amounts of vanadium and sulfur, which are subsequently annealed in a S-rich atmosphere, self-intercalated ultimately thin V5S8-derived layers are obtained, which host 2 × 2 V-layers between sheets of VS2. We provide atomic models for the thinnest V5S8-derived structures. Finally, we use scanning tunneling spectroscopy to investigate the charge density wave observed in the 2D V5S8-derived islands.

Unlocking highly stable and reversible in-situ integration of defect-rich 2D vanadium sulfide with Ti3C2Tx MXene heterostructures: Boosting asymmetric supercapacitor performance

To broaden the functionalities of transition metal dichalcogenides and two-dimensional transition metal carbides such as MXenes (Ti3C2Tx-MX), it is necessary to appropriately integrate them with each other to form heterostructures. The integrated heterostructures should maintain functionality through strong covalent interaction and offer excellent electrochemical properties. The requirement for developing appropriately integrated heterostructures is the control of nucleation and growth by governing the reaction kinetics. However, developing heterostructures over MXenes on a large scale is extremely challenging. Herein, we propose an investigation to elucidate the formation of defect-rich conductive heterostructures by in-situ integration of vanadium sulfide (VS2) on the surface of Ti3C2Tx-MX (VS2–Ti3C2Tx-MX) via controlled nucleation and growth in a facile hydrothermal process. The scrutinized binder-free flexible fabric-based VS2–Ti3C2Tx-MX0.25 electrode exhibits an excellent specific capacitance of 750 F g−1 and long-term stability (∼93 % retention after 10000 cycles). Moreover, these defect-rich and interlayer-expanded integrated heterostructures showed exceptional cycling stability and an impressive energy density of 52.08 Wh kg−1 at a power density of 750 W kg−1 when employed as fabric-based asymmetric supercapacitor (ASC) devices with VS2–Ti3C2Tx-MX0.25//Ti3C2Tx-MX configuration. We anticipate that the approach presented in this work will promote the development of various MXene-based heterostructures for manipulating the versatile properties of MXenes and VS2 in energy storage applications.

MXene-Stabilized VS2 Nanostructures for High-Performance Aqueous Zinc Ion Storage.

Aqueous zinc-ion batteries (AZIBs) based on vanadium oxides or sulfides are promising candidates for large-scale rechargeable energy storage due to their ease of fabrication, low cost, and high safety. However, the commercial application of vanadium-based electrode materials has been hindered by challenging problems such as poor cyclability and low-rate performance. To this regard, sophisticated nanostructure engineering technology is used to adeptly incorporate VS2 nanosheets into the MXene interlayers to create a stable 2D heterogeneous layered structure. The MXene nanosheets exhibit stable interactions with VS2 nanosheets, while intercalation between nanosheets effectively increases the interlayer spacing, further enhancing their stability in AZIBs. Benefiting from the heterogeneous layered structure with high conductivity, excellent electron/ion transport, and abundant reactive sites, the free-standing VS2/Ti3C2Tz composite film can be used as both the cathode and the anode of AZIBs. Specifically, the VS2/Ti3C2Tz cathode presents a high specific capacity of 285 mAh g-1 at 0.2 A g-1. Furthermore, the flexible Zn-metal free in-plane VS2/Ti3C2Tz//MnO2/CNT AZIBs deliver high operation voltage (2.0 V) and impressive long-term cycling stability (with a capacity retention of 97% after 5000 cycles) which outperforms almost all reported Vanadium-based electrodes for AZIBs. The effective modulation of the material structure through nanocomposite engineering effectively enhances the stability of VS2, which shows great potential in Zn2+ storage. This work will hasten and stimulate further development of such composite material in the direction of energy storage.

Advanced V-based materials for multivalent-ion storage applications

Multivalent-ion batteries, as promising alternative or supplementary technologies to lithium-ion batteries, have increasingly attracted attention recently. Various advanced materials have been presented to pursue potential breakthroughs in energy and power. Among them, vanadium (V)-based materials benefiting from abundant resources, various polymorphs and valences, especially most with large interlayer spacings, are good candidates for multivalent-ion storage. However, limited by multiple inherent issues, e.g., strong electrostatic interactions, poor electronic conductivity, structure collapse or materials dissolution under battery operation, etc. , various strategies have sprung many advanced materials and applications and also brought about new challenges that are in urgent need to clarify and summarize. Hence, advanced V-based compounds developed for multivalent-ion storage in the past few years are selectively summarized and systematically analyzed, including vanadium oxides and sulfides, vanadates, and V-based MXenes and phosphates. Not only crystal structures and electrochemical properties but also mainstream ion storage mechanisms are critically reviewed. Through analyzing the challenges accompanying multivalent-ion storage, potential opportunities are anticipated.

Microwave-induced defect-rich vanadium sulfide cathodes for highly reversible electrochemical magnesium storage

Vanadium sulfide (VS4) demonstrates the most prospect as the cathode materials for rechargeable magnesium battery due to its special one-dimensional linear crystal structure. However, VS4 cathode still suffers from sluggish kinetics, irreversible structural change, short cycle life, and low capacity. Herein, a microwave-induced synthesis method is presented to fabricate VS4 nanosheets with rich sulfur vacancies and high V3+/V4+ ratio. When serviced as the cathode material for rechargeable magnesium battery, the VS4 nanosheets display excellent electrochemical performances with large specific capacity of 701 mAh/g at 200 mA g−1 current density. In addition, the VS4 nanosheets cathodes also show long-term operating stability over 600 cycles at 1.0 A/g current density with only 0.3 % capacity decay per cycle. Our experimental results show that the improved electrochemical reaction kinetics is ascribed to the defect-rich structure and the reversible anionic redox reactions between S2−/S22− of the VS4 nanosheets. This work offers a meaningful way to design high-performance Mg2+ ion storage cathode materials with favorable diffusion kinetics.

Low‐Temperature Atomic Layer Deposition Synthesis of Vanadium Sulfide (Ultra)Thin Films for Nanotubular Supercapacitors

Herein, the synthesis of vanadium sulfide (VxSy) by atomic layer deposition (ALD) based on the use of tetrakis(dimethylamino) vanadium (IV) and hydrogen sulfide is presented for the first time. The (ultra)thin films VxSy are synthesized in a wide range of temperatures (100–225 °C) and extensively characterized by different methods. The chemical composition of the VxSy (ultra)thin films reveals different vanadium oxidation states and sulfur‐based species. Extensive X‐ray photoelectron spectroscopy analysis studies the effect of different ALD parameters on the VxSy chemical composition. Encouraged by the rich chemistry properties of vanadium‐based compounds and based on the variable valences of vanadium, the electrochemical properties of ALD VxSy (ultra)thin films as electrode material for supercapacitors are further explored. Thereby, nanotubular composites are fabricated by coating TiO2 nanotube layers (TNTs) with different numbers of VxSy ALD cycles at low temperature (100 °C). Long‐term cycling tests reveal a gradual decline of electrochemical performance due to the progressive VxSy thin films dissolution under the experimental conditions. Nevertheless, VxSy‐coated TNTs exhibit significantly superior capacitance properties as compared to the blank counterparts. The enhanced capacitance properties exhibited are derived from the presence of chemically stable and electrochemically active S‐based species on the TNTs surface.

1T-VS2@V2O3 Synergistic Nanoarchitecture-Based Lamellar Clusters as the High Conductivity Cathodes of Thermal Batteries.

Thermal batteries are solid-state, thermally activated batteries with long storage times and high reliability. FeS2 is used as a cathode material commonly, but the high internal resistance and low voltage platform limit the improvement of battery performance. Herein, the 1T-phase vanadium disulfide (VS2) is prepared via the scalable hydrothermal method and applied to thermal battery cathode materials for the first time. 1T-VS2 lamellar flower clusters have high electronic conductivity (1.583 S cm-1) at room temperature, which is 75 times higher than FeS2 (0.021 S cm-1). Mechanism analysis shows that 1T-VS2@V2O3 can be formed based on the part of 1T-VS2 being oxidized to V2O3 at the discharge temperature. Benefiting from the synergistic effect of vanadium sulfide and vanadium oxide as a cathode for thermal batteries enhanced specific capacity (292.4 mA h g-1) and mass energy density (572.5 W h kg-1) when cutoff voltage is 1 V. Additionally, the discharge results indicate that the cells utilizing 1T-VS2 cathodes provided a higher voltage platform of 2.11 V than 1.84 V for FeS2. This impressive work can offer a good strategy for boosting cathode materials for a high-performance thermal battery.

Mitigating Interfacial Capacity Fading in Vanadium Pentoxide by Sacrificial Vanadium Sulfide Encapsulation for Rechargeable Mg-Ion Batteries.

Rechargeable Mg-ion Batteries (RMB) containing a Mg metal anode offer the promise of higher specific volumetric capacity, energy density, safety, and economic viability than lithium-ion battery technology, but their realization is challenging. The limited availability of suitable inorganic cathodes compatible with electrolytes relevant to Mg metal anode restricts the development of RMBs. Despite the promising capability of some oxides to reversibly intercalate Mg+2 ions at high potential, its lack of stability in chloride-containing ethereal electrolytes, relevant to Mg metal anode hinders the realization of a full practical RMB. Here the successful in situ encapsulation of monodispersed spherical V2O5 (≈200nm) is demonstrated by a thin layer of VS2 (≈12nm) through a facile surface reduction route. The VS2 layer protects the surface of V2O5 particles in RMB electrolyte solution (MgCl2 + MgTFSI in DME). Both V2O5 and V2O5@VS2 particles demonstrate high initial discharge capacity. However, only the V2O5@VS2 material demonstrates superior rate performance, Coulombic efficiency (100%), and stability (138mAhg-1 discharge capacity after 100 cycles), signifying the ability of the thin VS2 layer to protect the V2O5 cathode and facilitate the Mg+2 ion intercalation/deintercalation into V2O5.

Solid–gas synthesis of stable V3S4 nanoflakes: electrochemical characterization as a Li-ion battery anode

Low temperature synthesis of V3S4 nanoflakes using a unique gas–solid reaction route.

Copper Vanadium Sulfide as an Anode Material in Sodium-Ion Batteries

As the modern world is moving from non-renewable energy sources to renewable sources, such as wind and solar, energy storage devices are necessary in more than just portable electronics. Large-scale, stationary energy storage is required to combat the intermittent supply of renewable energy. Li-ion batteries, which are the current state of art in energy storage devices, will not be viable in the long term for such an application as it requires a large quantity of scarce raw materials (e.g. Li, Co). To reduce the cost and increase the long-term sustainability of batteries, more abundant energy storage materials are required. Sodium is the 6th most abundant element in the earth, making it significantly more abundant than Li. Na shares a similar chemistry to Li, helping advance research into sodium-ion batteries (SIBs). However, there are many challenges associated with SIBs, such as slower diffusion kinetics and reduced cycling stability due to the larger iconic radius of Na ions (1.02 Å (Na+) vs 0.76Å (Li+)) (1). This issue leads to incompatibility of most current anode materials used in LIBs, necessitating the identification of alternative materials (2). Transition metal sulfides (TMS) have great potential as anode materials for SIBs due to their high theoretical capacities as a result of conversion-based reactions occuring during cycling (3). However, conversion-based materials suffer from volume expansion during the sodiation and desodation process (4). CuS (covellite) has attracted a lot of attention and has a theoretical capacity of 560mA.h/g and electrical conductivity of ∼10−3Scm−1 (2,5). Unfortunately, CuS requires significant modifications to enhance its structural stability such as the formation of rGO composites or intricate morphological alteration to mitigate volume expansion during cycling. Herein, we address the addition of a second transition metal, vanadium, to form a ternary material (Cu3VS4) that enables cycling stability. Cu3VS4 is produced via a colloidal hot injection method to allow for high precision control over the morphology and phase purity. Factors such as ligand exchange, voltage profile, electrolyte selection, phase transformation (via in-situ and ex-situ studies), and SEI layer formation are also investigated to understand their contributions to the long-term stability of the cell. This study provides a mechanistic insight into the factors that affect the long-term stability of the material, taking a step closer to the production of sustainable materials for energy storage devices.

NiAs-type vanadium sulfides: Topological surface and abundant electroactivity as a bi-functional material in Mg/Li batteries

Rechargeable Mg battery (RMB) is a new type of next-generation secondary battery. The unique NiAs-type V3S4 is capable of achieving high electrochemical performance due to its bi-functional effect of electroactive and anchoring ability to the discharge products of polysulfides. Herein, the first-principles calculations were conducted to explore the electronic properties, dynamic and absorption behavior of Mg/Li-ions in the bulk and crystal plane of V3S4 to reveal the bi-functional mechanism in Mg/Li batteries. First, the stable surface adsorption and rapid diffusion kinetics of Mg/Li ions render the high-rate capability for V3S4. Second, the Mg/Li polysulfides could effectively anchor on the V3S4 (111) plane and retain their structural stability during the discharge–charge process for Mg/Li batteries. Even after Li2Sn/MgSn adsorption, the metallic property of V3S4 is still preserved to realize the redox electrochemistry of Li2Sn/MgSn and ameliorates the effect of the insulated low-order polysulfides. Meanwhile, the low Gibbs energy differences for Mg and Li polysulfides on V3S4 (111) plane gives the evidence of electrocatalytic property. As bi-functional material, the V3S4 has striking characteristics of low diffusion barrier, benificial adsorption and preeminent electrocatalytic ability of Li/Mg species, which can be leveraged for designing vanadium sulfides as high-conductivity cathode materials for RMBs.

Highly efficient and stable vanadium-based electrocatalysts: Stoichiometric iron vanadium sulfides for water-oxidation at large current densities

Rational design of inexpensive electrocatalysts with high activity towards oxygen evolution reaction (OER) consisting of a complex four-electron process is of great importance for developing renewable energies in the form of hydrogen fuel from water electrolysis. Herein, we develop an exceptionally active and stable OER electrocatalyst, stoichiometric iron vanadium sulfide (Fe1.94V1.06S4) grown on nickel foam (NF). This electrocatalyst affords current densities of 100 and 1500 mA cm−2 at low overpotentials of 193 and 253 mV, respectively, and has stable operation time of exceeding 150 h in alkaline electrolyte, which dramatically outperforms most of the recently reported electrocatalysts (typically, the state-of-the-art NiFe-based electrocatalysts). Systematic investigations on the effects of vanadium and its valence state demonstrate that Fe3+ coupled with V2+ in Fe1.94V1.06S4 endows a larger benefit on the OER than the counterparts in FeV2S4 and vanadium-doped pyrrhotite (Fe7−xVxS8). Density functional theory (DFT) simulations reveal the highly conductive stoichiometric iron vanadium sulfides and favored binding energetics of the OER intermediates on them with a derived amorphous Fe–V oxyhydroxide overlayer due to the synergistically optimized the electronic structure. Thus, a novel bimetallic system containing low-valent vanadium is anticipated to work effectively to enable the communities to scrutinize and exploit new electrocatalysts for water splitting.

Extraction of Vanadium from the Spent Residuum Catalysts by Fenton-like Reaction Followed with Alkaline Leaching

Spent residuum hydroprocessing (RHDP) catalysts are hazardous waste bearing high-content vanadium and large amounts of oily pollutants. In this paper, a process featuring a Fenton-like reaction and alkaline leaching was proposed to recover vanadium from spent RHDP catalysts. In the first step, a Fenton-like reaction using peroxide was conducted to degrade the oily pollutants and make the surface of the spent catalyst becomes hydrophilic. In the second step, the vanadium-containing deposit on the catalyst was leached with 0.5 M Na2S2O8 at 70 °C for transforming vanadium sulfide to oxide in 5 h. In the last step, alkaline leaching was employed to dissolve vanadium from the oxidizing residue at 80 °C for 1 h. It was found that the accumulated leaching efficiency of vanadium can reach up to 90.92%, and only a small part of aluminum and sulfur was dissolved. These results indicated that this combined process can extract vanadium selectively from spent residuum hydroprocessing catalysts under a relatively mild condition.