In Situ Induced Core–Shell Carbon-Encapsulated Amorphous Vanadium Oxide for Ultra-Long Cycle Life Aqueous Zinc-Ion Batteries

Inevitable dissolution in aqueous electrolytes, intrinsically low electrical conductivity, and sluggish reaction kinetics have significantly hampered the zinc storage performance of vanadium oxide-based cathode materials. Herein, core–shell N-doped carbon-encapsulated amorphous vanadium oxide arrays, prepared via a one-step nitridation process followed by in situ electrochemical induction, as a highly stable and efficient cathode material for aqueous zinc-ion batteries (AZIBs) are reported. In this design, the amorphous vanadium oxide core provides unobstructed ions diffusion routes and abundant active sites, while the N-doped carbon shell can ensure efficient electron transfer and greatly stabilize the vanadium oxide core. The assembled AZIBs exhibit remarkable discharge capacity (0.92 mAh cm⁻² at 0.5 mA cm⁻²), superior rate capability (0.51 mAh cm⁻² at 20 mA cm⁻²), and ultra-long cycling stability (≈100% capacity retention after 500 cycles at 0.5 mA cm⁻² and 97% capacity retention after 10 000 cycles at 20 mA cm⁻²). The working mechanism is further validated by in situ X-ray diffraction combined with ex situ tests. Moreover, the fabricated cathode is highly flexible, and the assembled quasi-solid-state AZIBs present stable electrochemical performance under large deformations. This work offers insights into the development of high-performance amorphous vanadium oxide-based cathodes for AZIBs.     

Bilayered VOPO4⋅2H2O Nanosheets with High-Concentration Oxygen Vacancies for High-Performance Aqueous Zinc-Ion Batteries

2D materials with atomically precise thickness and tunable chemical composition hold promise for potential applications in nanoenergy. Herein, a bilayer-structured VOPO₄⋅2H₂O (bilayer-VOP) nanosheet is developed with high-concentration oxygen vacancies ([Vo˙˙]) via a facile liquid-exfoliation strategy. Galvanostatic intermittent titration technique study indicates a 6 orders of magnitude higher zinc-ion coefficient in bilayer-VOP nanosheets (4.6 × 10⁻⁷ cm⁻² s⁻¹) compared to the bulk counterpart. Assistant density functional theory (DFT) simulation indicates a remarkably enhanced electron conductivity with a reduced bandgap of ≈ 0.2 eV (bulk sample: 1.5 eV) along with an ultralow diffusion barrier of ≈ 0.08 eV (bulk sample: 0.13 eV) in bilayer-VOP nanosheets, thus leading to superior diffusion kinetics and electrochemical performance. Mott–Schottky (impedance potential) measurement also demonstrates a great increase in electronic conductivity with ≈ 57-fold increased carrier concentration owing to its high concentration [Vo˙˙]. Benefited by these unique features, the rechargeable zinc-ion battery composed of bilayer-VOP nanosheets cathode exhibits a remarkable capacity of 313.6 mAh g⁻¹ (0.1 A g⁻¹), an energy density of 301.4 Wh kg⁻¹, and a prominent rate capability (168.7 mAh g⁻¹ at 10 A g⁻¹).     

Ultra-High Capacity and Cyclability of β-phase Ca0.14V2O5 as a Promising Cathode in Calcium-Ion Batteries

Crystalline water-free β-phase Ca_0.14V₂O₅ is reported for the first time as a viable cathode material for calcium-ion batteries (CIBs). In contrast to layered α-V₂O₅ and δ-Ca_xV₂O₅·nH₂O, which have limited capacity, the β-phase delivers a reversible capacity of ≈247 mAh g⁻¹, which corresponds to the insertion/extraction of Ca²⁺ between Ca_0.14V₂O₅ and Ca_1.0V₂O₅. The process of Ca²⁺ insertion process and the accompanying structural relaxation are theoretically and experimentally verified. The initial insertion of Ca²⁺ into Ca_0.14V₂O₅ causes a slight shift of oxygen atoms surrounding hepta-coordination sites, creating penta-coordinated sites that are then partially filled up to Ca_0.33V₂O₅. Further insertion occurs through the stepwise occupation of up to 50% of neighboring hexa- and tetra-coordination sites to form Ca_0.67V₂O₅ and Ca_1.0V₂O₅, respectively. The rearrangement of oxygen atoms in Ca_0.14V₂O₅ also minimizes dimensional changes, leading to high cyclic stability during repeated charge/discharge cycles. The remarkable electrochemical performance of full cells containing a Ca_0.14V₂O₅ cathode and a K metal anode in Ca²⁺/K⁺ hybrid electrolytes, is also demonstrated, thanks to the inertness of K⁺ insertion into Ca_0.14V₂O₅ and the absence of calcium plating/stripping. The cyclic stability and high capacity of Ca_0.14V₂O₅ is not compromised in hybrid electrolytes, making it a viable CIB cathode.     

Organic Molecular Intercalated V3O7·H2O with High Operating Voltage for Long Cycle Life Aqueous Zn-Ion Batteries

V₃O₇·H₂O (VO) is an attractive cathode material for high-capacity aqueous Zn-ion batteries (AZIBs), but it is limited by slow ion mobility and low working platform voltage. Here, a 1,3-propane diamine (DP)-intercalated VO with nanoribbon-assembled thorn flower-like structure is fabricated by a facile hydrothermal method, noted as VO-DP. The study shows that the zinc ion diffusion coefficient in VO-DP (3.1 × 10⁻⁸ cm⁻² s⁻¹) is five orders of magnitude higher than that of a pure VO counterpart. Auxiliary density functional theory simulation shows that the embedded energy of zinc ions in VO-DP significantly decreases from 0.24 to −2.5 eV, thus leading to excellent diffusion kinetics and superior rate performance. Benefiting from these unique properties, AZIBs composed of VO-DP cathodes exhibit high operating voltage (0.89 V), remarkable capacities of 473 mA h g⁻¹ at 0.05 A g⁻¹, excellent rate capability (144 mA h g⁻¹ at 10 A g⁻¹) and long-term cycling performance (73% capacity retention over 15 000 cycles at 10 A g⁻¹).     

Structural and dielectric properties of ZrO2–TiO2–V2O5 nanocomposite prepared by CO-precipitation calcination method

Nanocrystalline ZrO₂–V₂O₅–TiO₂ composite was synthesized by co-precipitation method and calcined at 500 and 700 °C. The formation of the composite material has been confirmed by X-ray diffraction analysis. The surface morphology was determined by SEM and HRTEM and it was seen that increase in calcination temperature increases the grain size. EDX analysis confirms the presence of zirconium, titanium and vanadium in the lattice. Optical absorption studies reveal a very low absorption in the visible region for both the samples. The dielectric constant, loss and ac conductivity of the pelletized samples have been examined at different temperatures as functions of frequency and the activation energies were calculated. The results indicated that the dielectric constant increases with calcination temperature. It was seen that the dielectric constant increases on the addition of Vanadia to zirconia–titania composite making it ideal for use as a gate dielectric material.     

Aging characteristics of ZnO–V2O5-based varistors for surge protection reliability

The effect of sintering temperature on clamping characteristics and pulse aging behavior of V₂O₅/MnO₂/Nb₂O₅ co-doped zinc oxide varistors was systematically investigated at 875–950 °C. Experimental results related to varistor effect showed that the breakdown field decreased dramatically from 6830 to 968 V/cm with the increase in the sintering temperature and the non-ohmic coefficient exhibited a maximum (49.5) at 900 °C in the sintering temperature. Varistors sintered at 900 °C exhibited the best clamp characteristics for the pulse current of 1–100 A, with the clamp voltage ratio of K = 1.86–2.77. Varistors sintered at 875 °C exhibited the strongest stability; variation rates for the breakdown field, for the non-ohmic coefficient, and for the leakage current density were −14.2%, −63.6%, and 59.0%, respectively, after application of a multi-pulse current of 100 A.     

Line positions and intensities in theν 2 band of D2O improvied pumped D2O laser frequencies

Using high resolution Fourier transform spectra, thev ₂ band of D₂O has been analysed leading to an extensive and precise set of rotational energy levels of the (0 1 0) vibrational state. These levels are reproduced very satisfactorily with a Watson type Hamiltonian and precise rotational constants as well as the band centerv ₂ = 1178.3789 ± 0.0005 cm^-1 are determined. A total of 61 line intensities were measured, much attention being paid to a possible contamination of the D₂O sample by HDO. A least squares fit of the intensity data has provided us with an expansion of the transition moment operator of thev ₂ band from which the first derivative \(\left( {\frac{{\partial ^x \mu }}{{\partial q_2 }}} \right)_e \) = 0.1690 ± 0.0030 D has been deduced. Finally the complete synthetic spectrum of this band has been computed. All these results have been used to derive improved frequencies for the known pumped and far-infrared laser lines of D₂O and to predict new possible coincidences with the available CO₂ laser lines.     

Oxygen Defects Engineering of VO2·xH2O Nanosheets via In Situ Polypyrrole Polymerization for Efficient Aqueous Zinc Ion Storage

What has been a crucial demand is that designing mighty cathode materials for aqueous zinc−ion batteries (AZIBs), which are vigorous alternative devices for large−scale energy storage by means of their high safety and low cost. Herein, a facile strategy is designed that combines oxygen defect engineering with polymer coating in a synergistic action. As an example, the oxygen−deficient hydrate vanadium dioxide with polypyrrole coating (O_d−HVO@PPy) is synthesized via a one-step hydrothermal method in which introducing oxygen vacancy in HVO is simultaneously realized during the in situ polymerization. Such a desirable material adjusts the surface adsorption and internal diffusion of Zn²⁺ demonstrated by electrochemical characterization and theoretical calculation results. Moreover, it also utilizes conductive polymer coating to improve electrical conductivity and suppress cathode dissolution. Therefore, the O_d−HVO@PPy electrode delivers a preferable reversible capacity (337 mAh g⁻¹ at 0.2 A g⁻¹) with an impressive energy density of 228 Wh kg⁻¹ and stable long cycle life. This enlightened design opens up a new modus operandi toward superior cathode materials for advanced AZIBs.     

Effect of annealing and electrochemical properties of sol–gel dip coated nanocrystalline V2O5 thin films

Nanocrystalline vanadium pentoxide (V₂O₅) thin films were deposited on glass substrates by a simple and cost effective sol–gel dip coating method. The effect of annealing on microstructure and optical properties of V₂O₅ thin films were investigated. Formation of nanorods with the average diameter of 500–750 nm after annealing is observed by scanning electron microscopy. X-ray diffractometry indicates that an orthorhombic structured thin film is transformed to β-V₂O₅ nanorods by subsequent annealing at 500 °C. It was also confirmed that the growth of nanorods strongly correlates with annealing conditions; nanorod formation can be explained by surface diffusion phenomenon. The electrochemical performance of the V₂O₅ nanorods was investigated by cyclic voltammetry.     

Excitation-Dependent Emission Color Tuning of 0D Cs2InBr5·H2O at High Pressure

Self-trapped exciton (STE) emission of low-dimensional metal halides has witnessed explosive developments in both display and illumination, due to its intriguing photoluminescence properties. As one typical feature, STE emission energy is commonly independent of excitation wavelength. Herein, a rare phenomenon of inverse excitation-dependent dual-band emission is achieved on 0D Cs₂InBr₅·H₂O. Under initial compression, the contraction of inhomogeneously coordinated InBr₅O octahedra gives rise to blue-shifted STE emission with the decreased Stokes shift. As the phase transition occurs under higher pressure, considerable octahedral distortions generate a new defect-related localized exciton emission. Notably, the high-energy emission from the intrinsic STE state is only observed under the low-energy excitation, which is believed to originate from the excitation-dependent multiple excited states in high-pressure Cs₂InBr₅·H₂O.     

Influence of Yb2O3 on the 1.53 μm spectroscopic properties in Er3+/Ce3+ co-doped TeO2-WO3-Na2O-Nb2O5 glasses

The Yb2O3 component was introduced into the Er3+/Ce3+ co-doped tellurite glasses with the composition of TeO2-WO3-Na2O-Nb2O5 to study the effect of Yb3+ on the 1.53 μm spectroscopic properties of Er3+. The X-ray diffraction (XRD) curve and Raman spectrum were measured to investigate the structure nature of synthesized tellurite glasses. The absorption spectrum, upconversion emission spectrum and fluorescence spectrum were measured to evaluate the improved effect of Yb3+ concentration on the 1.53 µm band fluorescence of Er3+. Results of the measured 1.53 µm band fluorescence intensity show a significant improvement with the increase of Yb3+ concentration, while the total quantum efficiency reveals a similar increasing trend. The results of the present work indicate that Er3+/Ce3+/Yb3+ tri-doped tellurite glass has good prospect as a promising gain medium applied for the 1.53 µm broadband amplifier.     

Effect of Annealing on the Dark and Illuminated I(V ) Characterization of a ZnO:Ga|Cu2O Hetero-Junction Prepared by Ultrasonic Spray System

Semiconductors - This paper presents the Ultrasonic Spray Pyrolysis system fabrication of gallium-doped zinc oxide (ZnO:Ga)|cuprous oxide (Cu2O) thin film hetero-junction. The deposition parameters...     

Investigation of the Current–Voltage Characteristics of New MnO2/GaAs(100) and V2O5/GaAs(100) Heterostructures Subjected to Heat Treatment

Semiconductors - Complex oxide films with a thickness of about 200 nm are formed during the thermal oxidation of GaAs with magnetron-deposited V2O5 and MnO2 nanolayers. The electrical parameters of...     

Sensor Performance of Nanostructured TiO2–Cr2O3 Thin Films Derived by a Particulate Sol–Gel Route with Various Cr:Ti Molar Ratios

Nanocrystalline and nanostructured TiO₂–Cr₂O₃ thin films and powders were prepared by a facile and straightforward aqueous particulate sol–gel route at low temperature of 400°C. The prepared sols showed a narrow particle size distribution with hydrodynamic diameter in the range of 17.7 nm to 19.0 nm. Moreover, the sols were stable over 4 months, with constant zeta potential measured during this period. The effect of the Cr:Ti molar ratio on the crystallization behavior of the products was studied. X-ray diffraction (XRD) analysis revealed that the powders crystallized at low temperature of 400°C, containing anatase-TiO₂, rutile-TiO₂, and Cr₂O₃ phases, depending on the annealing temperature and Cr:Ti molar ratio. Furthermore, it was found that Cr₂O₃ retarded the anatase to rutile transformation up to 800°C. The activation energy of crystallite growth was calculated to be in the range of 1.3 kJ/mol to 2.9 kJ/mol. Transmission electron microscopy (TEM) imaging showed that one of the smallest crystallite sizes was obtained for TiO₂–Cr₂O₃ binary mixed oxide, being 5 nm at 500°C. Field-emission scanning electron microscopy (FESEM) analysis revealed that the deposited thin films had nanostructured morphology with average grain size in the range of 20 nm to 40 nm at 500°C. Thin films produced under optimized conditions showed excellent microstructural properties for gas sensing applications. They exhibited a remarkable response towards low concentrations of NO₂ gas at low operating temperature of 200°C, resulting in increased thermal stability of sensing films as well as a decrease in their power consumption. Furthermore, calibration curves revealed that TiO₂–Cr₂O₃ sensors followed the power law \({S = A[\mathrm{gas}]^{B}}\) (where S is the sensor response, the coefficients A and B are constants, and [gas] is the gas concentration) for two types of gas, exhibiting excellent capability for detection of low gas concentrations.     

Anisotropical electro-polarization effects induced in C2−O bonds present around the α-helixes of silk fibroin

Under the influence of perpendicularly applied positive electro-static field less than ≈10³V/cm to silk fibron textiles, at the high frequency side of the C₂?O bending reflection band (≈450～350 cm^?1), effect of step creation and step annihilation of the C₂?O pseudo dending bands was induced in three stages at ≈600～450 cm^?1 region IR spectroscopically relating to the stepnized statistical transfer of the unbonded 2P₂, π electrons in carbon which present with density of ≈4.0×10¹⁴/cm² in the surface mono-layer of silk fibroin from the states formed in (?C₁?C₂?N?)_m spiral chains upto the pseudo-bending states formed in C₂?O bondings. Fine ≈90 steps measured overlapping on these four types of C₂?O reflection bands were analysed as to consist four step series and they were shown as,y = A·J^m + B cm^?1 with A=20, B=521, m=0.55 and J=1, 2...18 for the B-series. And with A=39, B=283, m=0.63 and J=1, 2 ...17 for the C-series.y _J = A·J + B cm^?1 with A=11.42, B=201 and J=1, 2...13, for the D-series. And, stepnized C₂?O bending bands including that of permanent oscillators and pseudo-bending oscillators induced by the effect of transfer of the unbonded 2P₂ electrons in carbon atoms were shown as, E_N=A·N²+B·N+C (eV) with A=?1.50×10^?3, B=1.65×10^?2 and C=2.4×10^?2.     

Probing giant reduction of Tc in the Li(Ti1−xVx)2O4 spinel system

The doping effect of Vanadium in polycrystalline LiTi₂O₄ material is carefully analysed. We report on the detailed electrical and magnetic properties of Li(Ti_1−xV_x)₂O₄ system for 0⩽x⩽0.05 with an emphasis on the low Vanadium concentration. We have an interesting finding to report in that the doping of Vanadium in LiTi₂O₄, leads to a giant T_c reduction. The localized magnetic moments induced by the Vanadium doping seem to be responsible for the reduction in T_c.     

Synthesis of ZnO and Fe2O3 nanoparticles by sol–gel method and their application in dye-sensitized solar cells

ZnO and Fe₂O₃ nanoparticles have been formed in a silica matrix, through the sol–gel method and were used as a photoanode to fabricate dye-sensitized solar cells (DSCs). The obtained oxides were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscope and UV–visible absorption spectroscopy. The results indicate that ZnO and Fe₂O₃ prepared by this method may be used as photoanodes in photo-electro-chemical energy conversion systems. DSSCs have been built using eosin Y as photosensitizer and their photocurrent, open-circuit voltage, fill factor and efficiency have been measured under direct sunlight illumination (1000 Wcm^?2). A ZnO-film solar cell had the best performance with an open-circuit voltage of V_oc=0.7 V and short-circuit current density of I_sc=490 μA/cm². This was attributed to high optical gap energy and transparency of ZnO compared to Fe₂O₃. The effects of annealing temperature and concentration of Fe₂O₃ on conversion efficiency of the Fe₂O₃ based solar cell were also studied.     

Synchrotron study of the formation of nanoclusters in Al2O3/SiO x /Al2O3/SiO x /…/Si(100) multilayer nanostructures

Al₂O₃/SiO _x /Al₂O₃/SiO _x /…/Si(100) multilayer nanoperiodic structures (MNS) are studied by X-ray absorption near-edge structure spectroscopy (XANES). Experimental XANES spectroscopy spectra are obtained using synchrotron radiation. The formation of Si nanoclusters in the surface layers of the structures during their high-temperature annealing is observed. The structures featured intense size-dependent photoluminescence in the wavelength region near 800 nm. At the same time, it is shown that the formation of aluminum silicates is possible. The inversion effect of the intensity of the XANES spectra during the interaction of synchrotron radiation with MNSs is revealed.     

Silane-Mediated Expansion of Domains in Si-Doped κ-Ga2O3 Epitaxy and its Impact on the In-Plane Electronic Conduction

Unintentionally doped (001)-oriented orthorhombic κ-Ga₂O₃ epitaxial films on c-plane sapphire substrates are characterized by the presence of ≈ 10 nm wide columnar rotational domains that can severely inhibit in-plane electronic conduction. Comparing the in- and out-of-plane resistance on well-defined sample geometries, it is experimentally proved that the in-plane resistivity is at least ten times higher than the out-of-plane one. The introduction of silane during metal-organic vapor phase epitaxial growth not only allows for n-type Si extrinsic doping, but also results in the increase of more than one order of magnitude in the domain size (up to ≈ 300 nm) and mobility (highest µ ≈ 10 cm²V⁻¹s⁻¹, with corresponding lowest ρ ≈ 0.2 Ωcm). To qualitatively compare the mean domain dimension in κ-Ga₂O₃ epitaxial films, non-destructive experimental procedures are provided based on X-ray diffraction and Raman spectroscopy. The results of this study pave the way to significantly improved in-plane conduction in κ-Ga₂O₃ and its possible breakthrough in new generation electronics. The set of cross-linked experimental techniques and corresponding interpretation here proposed can apply to a wide range of material systems that suffer/benefit from domain-related functional properties.