V2O5 Layer Research Articles

V2O5 Polysulfide Anion Barrier for Long-Lived Li–S Batteries

We describe a V2O5 polysulfide anion barrier for a Li–S battery containing a Li metal anode, an organic solvent-based electrolyte, and a nanostructured carbon–sulfur composite cathode that cycles without degradation from dissolution of soluble polysulfide anions. Degradation is prevented by the micrometer-scale V2O5 layer that physically isolates the anode and cathode electrolytes, thus blocking diffusion of dissolved polysulfide anions while permitting solid-state transport of Li+ cations. This divided cell architecture eliminates the interaction of soluble polysulfide with the Li anode. Mechanical integrity of the thin V2O5 layer is achieved by depositing the layer on a commercial polymeric battery separator. In addition, the isolated cathode electrolyte is optimized by the intentional addition of Li2S8, which suppresses redistribution of sulfur within the nanostructured carbon–sulfur composite cathode. A 5 mA h pouch cell of this design has been cycled >300 times over ∼1 year without noticeable degrada...

Surface Modification of Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 by V2O5- Coating

Abstract We presented a method to improve the first discharge capacity and the cycling performance of Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 which was synthesized by a coprecipitation-hydrothermal-calcinations method and coated by a V2O5 layer on the surface of Li1.6(Fe0.2Ni0.2Mn0.6)O2.6. The crystal structure and the charge/discharge performance of Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), inductively coupled plasma (ICP) and electrochemical performance measurement. Results show that V2O5 exists only on the surface, and has no effect on the crystal structure; the Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 coated with V2O5 exhibits better first discharge capacity than the bared Li1.6(Fe0.2Ni0.2Mn0.6)O2.6. The electrochemical tests demonstrate that Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 coated with 3 wt% V2O5 shows the best electrochemical performance with the discharge capacity 200.3 mAh/g after 50 cycles, while the bared sample has 194.0 mAh/g only. CV results indicate that the V2O5 coating can suppress the phase transitions and prevent the surface of cathode materials from the direct contact with the electrolyte.

Role of Vanadium Pentoxide Hole‐Extracting Nanolayer in Rubrene/C70‐Based Small Molecule Organic Solar Cells

Vanadium pentoxide (V2O5) was inserted between the donor layer and the anode as a hole‐extracting nanolayer. Compared with devices without a hole‐extracting layer, short‐circuit current density (JSC), open‐circuit voltage (VOC), fill factor (FF), and power conversion efficiency (PCE) of rubrene/C70‐based heterojunction solar cells with 3 nm V2O5 nanolayer are enhanced by 99%, 73%, 20%, and 310%, respectively. We found that V2O5 interlayer can effectively suppress the contact resistance and increase the hole transport capability. The dependence of the device performance on V2O5 layer thickness as well as fill factor on exciton dissociation and charge transport was also investigated in detail.

Gradient V2O5 surface-coated LiMn2O4 cathode towards enhanced performance in Li-ion battery applications

The spinel LiMn2O4 was recognized as an appealing candidate cathode material for high rate Li-ion battery, but it suffers from severe capacity fading, especially at a high temperature. In order to solve this problem, we prepared V2O5 coated LiMn2O4 (LiMn2O4@V2O5) samples in this work and its structure and morphology were characterized by powder X-ray diffraction, scanning electron microscope, and transmission electron microscope. The LiMn2O4@V2O5 material delivers an excellent cycling ability and rate capability in lithium batteries, while sustaining a capacity of 75.5 mAh g−1 after 200 cycles at 2C with a high operating temperature (328K). This performance are much better than that of LiMn2O4 (35.4 mAh g−1) without V2O5 coating, the capacity of which faded seriously. These results indicated that the surface modification of V2O5, which possess a relative lower operating potential (≤ 3.7V, LixV2-x/5O5) compare to the LiMn2O4 (∼ 3.9 and 4.1V), can improve the electrochemical properties of LiMn2O4 by endowing a fast lithium diffusion and reasonable electronic conductivity which facilitates the transformation of the electrons and ions. In addition, the acidic and isolated protective layer of V2O5 can work as a HF inhibitor and/or HF scavenger and suppress the dissolution of manganese into electrolyte. Thus, we believe that such a LiMn2O4@V2O5 composite can be an economical and viable candidate cathode material for Li-ion batteries.

An efficient organic inverted solar cell with AnE-PVstat:PCBM active layer and V2O5/Al anode layer

An inverted organic solar cell, which is based on anthcene-containing poly (p-phenylene-ethynylene)-alt-poly(p-phenylene-vinylene) (PPE-PPV) polymer (AnE-PVstat) and phenyl C61 butyric acid methyl ester (PCBM), was fabricated with Titanium dioxide (TiO2) electron transport layer and V2O5/Al anode layer. In this study, we have investigated the effect of V2O5 thickness on solar cell efficiency. Power conversion efficiency of 3.26% has been achieved for 15nm V2O5 layer. The lifetime of the cell was investigated using ISOS-L-1. The test indicated that the durability of the solar cell, which is designed in ITO/TiO2/AnE-PVstat:PCBM/V2O5 (15nm)/Al configuration, is 99% under standard solar irradiation of 100mW/cm2 (AM 1.5G) at ambient conditions for 24h.

Role of V2O5 coating on LiNiO2-based materials for lithium ion battery

X-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive spectrometer (EDX) and X-ray photoelectron spectroscopy (XPS) are used to demonstrate that V2O5 is successfully coated on LiNiO2-based materials. The V2O5 layer will react with Li impurities on surface, which will reduce the pH value and rapid moisture uptake ability of LiNiO2-based materials. Cells tests indicate that V2O5-coating layer works as HF inhibitor and/or HF scavenger, which contributes a significant improvement in cycling performance and storage characteristics in electrolyte. In the mean time, V2O5 acts as isolating layer when cathode material contacts with electrolyte especially cycling at high voltage. Structural analysis shows that V2O5-coating layer has more advantage over other oxide coating in delaying Ni3+/Ni2+ transformation and lithium extraction from bulk surface, which benefits from the properties of V2O5 reacting with LiOH/Li2CO3 impurities on surface.

Efficient Charge Injection in p-Type Polymer Field-Effect Transistors with Low-Cost Molybdenum Electrodes through V2O5 Interlayer

Here we report high-performance polymer OFETs with a low-cost Mo source/drain electrode by efficient charge injection through the formation of a thermally deposited V2O5 thin film interlayer. A thermally deposited V2O5 interlayer is formed between a regioregular poly(3-hexylthiophene) (rr-P3HT) or a p-type polymer semiconductor containing dodecyl-substituted thienylenevinylene (TV) and dodecylthiophene (PC12TV12T) and the Mo source/drain electrode. The P3HT or PC12TV12T OFETs with the bare Mo electrode exhibited lower charge carrier mobility than those with Au owing to a large barrier height for hole injection (0.5-1.0 eV). By forming the V2O5 layer, the P3HT or PC12TV12T OFETs with V2O5 on the Mo electrode exhibited charge carrier mobility comparable to that of a pristine Au electrode. Best P3HT or PC12TV12T OFETs with 5 nm thick V2O5 on Mo electrode show the charge carrier mobility of 0.12 and 0.38 cm(2)/(V s), respectively. Ultraviolet photoelectron spectroscopy results exhibited the work-function of the Mo electrode progressively changed from 4.3 to 4.9 eV with an increase in V2O5 thickness from 0 to 5 nm, respectively. Interestingly, the V2O5-deposited Mo exhibits comparable Rc to Au, which mainly results from the decreased barrier height for hole carrier injection from the low-cost metal electrode to the frontier molecular orbital of the p-type polymer semiconductor after the incorporation of the transition metal oxide hole injection layer, such as V2O5. This enables the development of large-area, low-cost electronics with the Mo electrodes and V2O5 interlayer.

Orthorhombic phase formation in electrochemically grown vanadium oxide (V2O5) nanofibers

The inner structure of V2O5 nanofibers synthesized by electrochemical deposition has been investigated by transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The experimental results demonstrate that the fibers are formed by 2D orthorhombic layers of V2O5. The layers are formed along the plane ab stacked in the crystallographic direction c. Additionally the diffraction results indicate that the fibers grow preferentially along the (100) crystallographic plane with surface dominated by the plane (001). The formation of fibers is discussed in terms of the preferential growth along specific orientations in order to minimize the surface energy of the nanostructures.

Enhanced electrochemical properties of lithium-reactive V2O5coated on the LiNi0.8Co0.1Mn0.1O2cathode material for lithium ion batteries at 60 °C

The cycling performance of a lithium-reactive V2O5 coated LiNi0.8Co0.1Mn0.1O2 material at 60 °C is substantially improved by a wet-coating process. The V2O5-coated materials are obtained from drying a mixture consisting of NH4VO3 and LiNi0.8Co0.1Mn0.1O2 powders dispersed in ethanol at 85 °C followed by firing at 300 °C for 5 h. The morphology of the V2O5-coated LiNi0.8Co0.1Mn0.1O2 particle synthesized by this coating process is characterized by SEM, TEM and EDX analysis. The V2O5 layer is homogeneously coated onto the particle and the coating thickness was found to be approximately 10–30 nm. The capacity improvement at 60 °C is related to the fact that the highly distributed V2O5 near the surface diminishes the side reactions between the cathode and electrolyte. Moreover, the improvements may also benefit from the unique structure and properties of V2O5.

Improved performances in organic and polymer light‐emitting diodes using solution‐processed vanadium pentoxide as a hole injection layer

AbstractWe report that a solution‐processed vanadium pentoxide (V2O5) layer can be utilized as an effective and stable hole injection layer in organic light‐emitting diodes and polymer light‐emitting diodes instead of polyethylene dioxythiophene : polystyrenesulfonate (PEDOT : PSS). The organic light‐emitting diode and polymer light‐emitting diode with the V2O5 layer have driving voltages that are 2.2 and 0.3 V lower for 1000 cd/m2, respectively, than the devices with PEDOT : PSS. In addition, the devices with the V2O5 layer show improved operational stability compared with the devices with PEDOT : PSS. Therefore, a solution‐processed V2O5 layer can be utilized as an effective and stable hole injection layer instead of PEDOT : PSS.

Improvement of electrochemical properties of LiNi1/3Co1/3Mn1/3O2 by coating with V2O5 layer

The capacity fading and lower rate of layered cathode materials prohibited widely applications in lithium ion batteries. In this paper, V2O5 was coated on the surface of LiNi1/3Co1/3Mn1/3O2 to enhance its electrochemical performance at a voltage range of 2.8–4.5V. The prepared materials were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM). The capacity retention at the 100th cycle have been increased from 62% to over 80% for the 3wt.% V2O5 coated sample. The rate performance has been improved by V2O5 coating which mainly because of the coating layer enhance the surface electronic/ionic transport. Cyclic voltammetry (CV) showed that the redox properties of the pristine sample have a more obvirous changes after charge–discharge cycles compared with the coated samples. Electrochemical impedance spectroscopy (EIS) results suggest that the V2O5 coating layer play an important role in suppressing the increase of cell impedance with cycling especially for the increase of charge-transfer resistance (Rct).

Zn3(VO4)2 prepared by magnetron sputtering: microstructure and optical property

Zinc vanadium oxide Zn3(VO4)2 has been prepared by means of DC magnetron sputtering and subsequent post heat treatment. The samples were synthesized via two routes: dual-target co-sputtering of ZnO and V2O5 or the ordinal deposition of V2O5 and ZnO thin layers. The obtained precursors were then annealed in oxygen atmosphere from 500 to 550 °C to form the Zn3(VO4)2 compound. Morphology and composition of the samples have been investigated by means of scanning electron microscope and energy-dispersive X-ray spectroscopy. X-ray diffraction pattern shows the presence of α-Zn3(VO4)2, ZnO and vanadium oxide in the annealed ZnO–V2O5 samples. Pure V2O5 with two distinct phases, β and γ phases, is found for the samples annealed at 500 °C. Room temperature photoluminescence properties have been studied, and the annealed samples exhibit excellent light emission in the visible region centred at 528 nm from Zn3(VO4)2 compound. The light emission from Zn3(VO4)2 is discussed based on charge transfer and Frank–Condon principles.

Oxide Sandwiched Metal Thin‐Film Electrodes for Long‐Term Stable Organic Solar Cells

AbstractOxide/silver/oxide multilayers as semitransparent top electrode for small molecule organic solar cells (OSCs) are presented. It is shown that two oxide layers sandwiching a central metal layer greatly improve the stability and lifetime of the organic solar cell. Thermally evaporated MoO3, WO3, or V2O5 layers are employed as an interlayer for subsequent silver deposition and significantly change the morphology of the ultrathin silver layer, improving charge extraction and electrodes series resistance. The transmittance of the electrode is increased by introducing oxide or oxide and organic multilayers as capping layer, which leads to higher photocurrent generation in the absorber layer. Application of 1 nm MoO3/11 nm Ag/10 nm MoO3/50 nm Alq3 multilayer electrodes in OSCs lead to an efficiency of 2.6% for a standard ZnPc:C60 cell, showing superior performance compared to devices with pure silver top contacts. The device lifetime is also strongly increased. MoO3 layers can saturate and stabilize the inner and outer metal surface, passivating it against most of the degradation mechanisms. With such an oxide/silver/oxide multilayer electrode, the time until the glass encapsulated OSC is degraded to 80% of its starting efficiency is enhanced from 86 h to approximately 4500 h compared to an OSC without an oxide interlayer.

Electrochemical performance of the nanostructured biotemplated V2O5 cathode for lithium-ion batteries

We report for the first time fabrication of nanostructured V2O5 thin film cathodes for lithium-ion batteries using Tobacco mosaic virus (TMV) particles as biological templates. TMV-templated V2O5 electrodes showed enhanced electrochemical performance compared to electrodes with a planar configuration demonstrating high specific capacity, excellent rate capability and cycling stability. A specific capacity of 12μAhcm−2 was achieved for the TMV-templated electrode with a V2O5 layer thickness of ∼30nm, which is 7–8 times higher than the specific capacity of planar V2O5 electrodes of the same thickness. Higher areal specific capacities are achievable by increasing active battery material loading: electrodes with twice higher V2O5 loading delivered capacities of ∼25μAhcm−2. Development of the cathode is an important step towards the fabrication of rechargeable lithium-ion batteries with superior virus-templated electrodes for high performance electrochemical energy storage.

Highly entangled K0.5V2O5 superlong nanobelt membranes for flexible nonvolatile memory devices

Flexible electronics has been an intensively pursued hot topic in recent years, and flexible nonvolatile memory devices (NVMs) are also an important concept in modern electronics due to the advantages of retaining stored information even when not powered, with great portability and high deformability. In this study, we report that δ-K0.5V2O5 bronze with sandwiched potassium atoms in the V–O framework has been found to be a new promising material platform for intriguing nonvolatile memory applications. The bronze structure with the sandwiched alkali metal atoms between the two V2O5 layers ensures the promising NVM effect by changing the electronic properties under an applied electric field. The δ-K0.5V2O5 bronze entangled superlong nanobelt networks, which are established via the “solid–solution–solid” (SSS) mechanism and a hydrogen-bond-assisted entangling process, bring the synergic advantages of excellent mechanical and electrical properties. Spin polarized GGA+U density functional theory calculations elucidate well the nature of bronze-based NVM, in which the overall effect of applying an electric field is to reduce the energy gap, no matter what the direction of the electric field is; the effects of electric field and ion shift would follow the same trend, the non-linear band gap changes would lead to resistance changes of this material. The NVMs based on the entangled superlong nanobelt membrane possess the advantages of not only low cost and very simple device structure, but also a reversible and noticeable nonlinear hysteresis, low consumption, stable WRER cycles, and a long retention time over 1000 s, showing promise for next-generation flexible NVMs.

The influence of modified electrodes by V2O5 film on the performance of ambipolar organic field-effect transistors based on C60/Pentacene

C60/Pentacene-based ambipolar organic heterostructure field-effect transistors (AOFETs) with Al source-drain (S/D) electrodes modified by inserting a transition metal oxide (V2O5) layer are fabricated. Compared with the device without V2O5 modified layer, the modified device shows good ambipolar characteristics with a hole mobility of 8.6× 10-2 cm2/V·s-1 and an electron mobility of 6.4× 10-2 cm2/V·s-1, and threshold voltages of 25 and -25 V, respectively. These performance improvements are ascribed to the presence of V2O5 layer at the Pentacene/Al interface which significantly reduces the source/drain contact resistance, increases the holes injection and makes electronic and hole injection close to balance. This result indicates that modified electrodes by V2O5 film is an effective approach to fabricating low cost and high performance AOFETs for realizing commercial applications.

Improved Performance of Pentacene Organic Field-Effect Transistors by Inserting a V2O5 Metal Oxide Layer

We fabricate pentacene-based organic field effect transistors (OFETs), inserting a transition metal oxide (V2O5) layer between the pentacene and Al source-drain (S/D) electrodes. The performance of the devices with V2O5/Al S/D electrodes is considerably improved compared to the pentacene-based OFET with only Al S/D electrodes. After the 10-nm V2O5 layer modification, the effective field-effect mobility of the devices increases from 2.7 × 10−3 cm2 /V·s to 8.93× 10−1 cm2/V·s. Owing to the change of the injection property, the effective threshold voltage (Vth) is changed from −7.5 V to −5 V and the on/off ratio shifts from 102 to 104. Moreover, the dispersion of sub-threshold current in the devices disappears. These performance improvements are ascribed to the low carrier injection barrier and the reduction of contact resistance. It is indicated that V2O5 layer modification is an effective approach to improve pentacene-based OFET performance.

Inverted Organic Solar Cells with Sol–Gel Processed High Work‐Function Vanadium Oxide Hole‐Extraction Layers

AbstractFor large‐scale and high‐throughput production of organic solar cells (OSCs), liquid processing of the functional layers is desired. We demonstrate inverted bulk‐heterojunction organic solar cells (OSCs) with a sol–gel derived V2O5 hole‐extraction‐layer on top of the active organic layer. The V2O5 layers are prepared in ambient air using Vanadium(V)‐oxitriisopropoxide as precursor. Without any post‐annealing or plasma treatment, a high work function of the V2O5 layers is confirmed by both Kelvin probe analysis and ultraviolet photoelectron spectroscopy (UPS). Using UPS and inverse photoelectron spectroscopy (IPES), we show that the electronic structure of the solution processed V2O5 layers is similar to that of thermally evaporated V2O5 layers which have been exposed to ambient air. Optimization of the sol gel process leads to inverted OSCs with solution based V2O5 layers that show power conversion efficiencies similar to that of control devices with V2O5 layers prepared in high‐vacuum.

CO Oxidation by Lattice Oxygen on V2O5 Nanotubes

Density-functional theory calculations were performed to investigate CO adsorption and oxidation on V2O5 nanotubes formed by rolling V2O5 (010) layers. CO adsorbs on both the inside and outside walls of V2O5 nanotubes by physisorption and chemisorption modes. The bidentate carbonate can form from CO chemisorption and decompose to CO2 on V2O5 nanotubes. CO oxidation into CO2 by the lattice oxygen, i.e., decomposition of carbonate, on the inside wall of V2O5 nanotubes requires less (0.21 vs 0.40 and 0.43 eV) and releases more energy (−0.17 vs −0.02 and −0.03 eV) than that on the V2O5 (010) single layer and the outside wall of V2O5 nanotubes. Our study shows that lattice oxygen of V2O5 participates in CO oxidation, and the confined environment is beneficial to CO2 formation.

Electrochemical oscillations and bistability during anodic dissolution of vanadium electrode in acidic media—part II. The model

Following our experimental results on the oscillatory and bistable vanadium electrooxidation in phosphoric acid medium (Gorzkowski et al., 2011), we constructed a theoretical model of the V/H3PO4 passivation/dissolution system which allowed us to reproduce the basic dynamic instabilities observed. In this model, the formation of the negative resistance (N-NDR) region was ascribed to the potential-dependent formation/destruction of the inhibitive V2O5 layer on the electrode surface. The dynamic system was defined in terms of two variables: electrode potential and surface concentration of VO 2 + species. Both relaxation oscillations and bistability for conditions similar to the experimental ones were obtained in numerical calculations and a theoretical bifurcation diagram was constructed. The analysis of the system’s dynamics in terms of nullclines allowed us to detect directly unattainable unstable steady states associated with both the oscillatory and bistable regimes.