Zinc Pyrovanadate Research Articles

Structural and optoelectronic properties of three different phases of Zn2V2O7 compound under pressure: FP-LAPW approach

The structural, electronic, and optical properties of the zinc pyrovanadate (Zn2V2O7) under hydrostatic pressure are investigated using the first-principle calculations. The Kohn–Sham equations are solved by the full potential linearized augmented plane wave approach. We have chosen the Perdew-Burke-Ernzerhof generalized gradient approximation for calculation of the exchange-correlation potentials. By the structural optimization, it is found that α-Zn2V2O7 has higher stability than β - and γ-Zn2V2O7. Calculated density of states spectra show that the hydrostatic pressure has a considerable effect on the O-p, Zn-d and V-d states on the top of valence band. By increasing pressure, the band gap value increases from α to β phase, then decrease at γ phase. By pressure, the absorption spectra are shifted towards high energies as the blue shift. The metallic character of α and β− Zn2V2O7 is observed at 5–10 eV. The plasmon energies increase from α to β phase, with pressure. There is a close agreement between the calculated absorption spectra and the experiment. The high plasmon energy and the wide absorption energy range makes this compound suitable for the optoelectronic devices.

Coupling of V2O5 structural design and electrolyte modulation toward stable zinc-ion battery

Layered vanadium oxides possess abundant crystal structures and multiple redox states, which account for excellent specific capacity for zinc ion batteries (ZIBs). However, vanadium-based cathodes typically suffer from structural instability and component dissolution, leading to inferior cyclic stability and rate performance. Herein, porous V2O5 slender leaf-like nanostructure anchored on carbon cloth (CC) is synthesized via electrodeposition and subsequent calcination. Taking advantage of the distinctive hierarchical structure and the introduction of propylene carbonate (PC) electrolyte additives, the free-standing VO-C2PC electrode provides a maximum reversible capacity of 555 mA h g−1 at 0.3 A g−1, and high capacity retention of 180 mA h g−1 after 5000 cycles at 10 A g−1. Even at a high mass loading, the VO-C2PC exhibits excellent Zn storage capability and stability. Furthermore, the Zn2+ storage mechanism reveals the gradual transformation of V2O5 into stable zinc pyrovanadate (ZVO) phase, which improves the stable Zn2+ storage capability. This study provides valuable insights into the construction of advanced electrodes and the design of novel electrolytes for high-performance ZIBs.

Electrolyte pH and operating potential: critical factors regulating the anodic oxidation and zinc storage mechanisms in aqueous zinc ion battery

The complicated multi-electron reactions and electrochemical/chemical evolution of vanadium oxides in zinc ion batteries make the detailed reaction mechanism difficult to understand. Here, we show that these reactions can be easily interpreted from the reliable potential–V-species (electrochemical) and pH–V-species (chemical) relationships. A systematic investigation of several low-valence vanadium oxides (V6O13, VO2, and V2O3) is conducted to study the detailed reaction mechanisms upon the anodic oxidation and routine zinc storage process. Vanadium oxides are thermodynamically converted to layered zinc pyrovanadate Zn3V2O7(OH)2·2H2O (ZVOH) in a certain range of pH (4.0–8.5) and operating potential following the VOx oxidation →V-species dissolution →ZVOH precipitation processes. The establishment of pH–V-species and potential–V-species relationships can well explain the reaction mechanisms not only in anodic oxidation but also in routine zinc insertion/extraction processes with the combination of electrochemical and chemical reactions. Moreover, due to the favorable open and stable crystal framework and unique Zn2+ storage mechanism, the obtained ZVOH exhibits a highly improved capacity of 492.7 mAh/g within the voltage window of 0.3–1.4 V. Our work highlights the critical roles of operating potential and electrolyte pH in zinc ion battery and offers new knowledge and practices for its commercialization.

Zinc pyrovanadate nanorods with excellent peroxidase-like activity at physiological pH for the colorimetric assay of H2O2 and epinephrine.

Exploring highly active peroxidase mimics at physiological pH is important for the construction of efficient and convenient colorimetric sensing platforms for detecting small biomolecules. In this work, prepared zinc pyrovanadate (Zn3V2O7(OH)2·2H2O) nanorods exhibit excellent peroxidase-like activity, which is verified by the fast oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) into a blue product (oxTMB) by H2O2 at physiological pH (pH = 7) in 2 min. In addition, the catalytic behaviors of Zn3V2O7(OH)2·2H2O as a peroxidase-like nanozyme conform to the Michaelis-Menten equation. Scavenger experiments prove that the catalytic activity of Zn3V2O7(OH)2·2H2O is ascribed to ˙O2- radicals generated in the process of catalysis. Based on the peroxidase-like activity of the Zn3V2O7(OH)2·2H2O nanozyme, a fast and convenient colorimetric sensor has been constructed to detect H2O2 and epinephrine (EP) under physiological pH. The detection limit of EP is as low as 0.26 μM. In addition, the feasibility of the proposed sensor has been validated to detect H2O2 in milk and EP in serum.

Regulating Zn Ion Desolvation and Deposition Chemistry Toward Durable and Fast Rechargeable Zn Metal Batteries.

The high Zn ion desolvation energy, sluggish Zn deposition kinetics, and top Zn plating pattern are the key challenges toward practical Zn anodes. Herein, these key issues are addressed by introducing zinc pyrovanadate (ZVO) as a solid zinc-ion conductor interface to induce smooth and fast Zn deposition underneath the layer. Electrochemical studies, computational analysis, and in situ observations reveal the boosted desolvation and deposition kinetics, and uniformity by ZVO interface. In addition, the anti-corrosion ability of Zn anodes is improved, resulting in high Zn stripping/plating reversibility. Consequently, the ZVO layer renders fast rechargeability and durable life in both Zn symmetric cells (1050h at 10mA cm-2 , 1 mAh cm-2 ) and Zn/V2 O5 batteries (79.1% capacity retention after 1000 cycles at 2 A g-1 ) with low electrode polarization. This work provides insights into the design of solid zinc-ion conductor interface to enhance the interface stability and kinetics of Zn metal anodes.

Vanadium Oxide-Poly(3,4-ethylenedioxythiophene) Nanocomposite as High-Performance Cathode for Aqueous Zn-Ion Batteries: The Structural and Electrochemical Characterization

In this work the nanocomposite of vanadium oxide with conducting polymer poly(3,4-ethylenedioxythiophene) (VO@PEDOT) was obtained by microwave-assisted hydrothermal synthesis. The detailed study of its structural and electrochemical properties as cathode of aqueous zinc-ion battery was performed by scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction analysis, X-ray photoelectron spectroscopy, thermogravimetric analysis, cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The initial VO@PEDOT composite has layered nanosheets structure with thickness of about 30-80 nm, which are assembled into wavy agglomerated thicker layers of up to 0.3-0.6 μm. The phase composition of the samples was determined by XRD analysis which confirmed lamellar structure of vanadium oxide V10O24∙12H2O with interlayer distance of about 13.6 Å. The VO@PEDOT composite demonstrates excellent electrochemical performance, reaching specific capacities of up to 390 mA∙h∙g-1 at 0.3 A∙g-1. Moreover, the electrodes retain specific capacity of 100 mA∙h∙g-1 at a high current density of 20 A∙g-1. The phase transformations of VO@PEDOT electrodes during the cycling were studied at different degrees of charge/discharge by using ex situ XRD measurements. The results of ex situ XRD allow us to conclude that the reversible zinc ion intercalation occurs in stable zinc pyrovanadate structures formed during discharge.

In-situ electrochemical conversion of Na5V12O32@graphene for enhanced cycle stability in aqueous zinc ion batteries

HypothesisNa5V12O32 (NVO) is a potential cathode for aqueous zinc ion batteries (AZIBs). However, it suffers severe capacity decay due to the dissolution of the active material. The structural design may be an effective solution to the problem. ExperimentsHerein, we construct a typical two-dimensional hierarchical structure of Na5V12O32@graphene (NVO@G) via a facile molten salt method. FindingsThe capacity fading problem is solved by the in-situ conversion of NVO@G to a more stable hierarchical system during cycling. The in-situ formed zinc pyrovanadate (Zn3V2O7(OH)2·2H2O, ZVO) nanosheets on the surface of graphene exhibits excellent zinc-ion storage stability. The presence of graphene induces the growth of NVO nanobelts to construct the typical two-dimensional hierarchical structure. Additionally, the in-situ conversion makes the formed ZVO nanosheets contact with graphene better. Benefitting from the hierarchical nanostructure and in-situ phase conversion, the NVO@G electrode shows excellent long-term stability (96.4% retention after 340 cycles at 0.3 A g−1, 85.7% retention after 4400 cycles at 5 A g−1) and high zinc ion storage capacity (220 mAh g−1 at 0.3 A g−1), which is superior to those of most electrode materials previously reported.

Corrosion as the origin of limited lifetime of vanadium oxide-based aqueous zinc ion batteries

Aqueous zinc ion batteries are receiving increasing attention for large-scale energy storage systems owing to their attractive features with respect to safety, cost, and scalability. Although vanadium oxides with various compositions have been demonstrated to store zinc ions reversibly, their limited cyclability especially at low current densities and their poor calendar life impede their widespread practical adoption. Herein, we reveal that the electrochemically inactive zinc pyrovanadate (ZVO) phase formed on the cathode surface is the main cause of the limited sustainability. Moreover, the formation of ZVO is closely related to the corrosion of the zinc metal counter electrode by perturbing the pH of the electrolyte. Thus, the dissolution of VO2(OH)2−, the source of the vanadium in the ZVO, is no longer prevented. The proposed amalgamated Zn anode improves the cyclability drastically by blocking the corrosion at the anode, verifying the importance of pH control and the interplay between both electrodes.

Electrochemically induced phase transition in a nanoflower vanadium tetrasulfide cathode for high-performance zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) are promising contenders for large-scale energy storage with the merits of their low cost, high safety, environmental friendliness, and competitive gravimetric energy density. Nevertheless, suitable cathode materials with long cycle life and adequate capacity are still rare. Herein, we report a nanoflower vanadium tetrasulfide/carbon nanotubes (VS4/CNTs) cathode with high Zn-storage performance. We propose a phase transition reaction mechanism from VS4 to zinc pyrovanadate in the initial cycles and a reversible intercalation mechanism for Zn2+ in zinc pyrovanadate during subsequent cycles. As a result, the cathode delivers a high discharge capacity of 265 mAh g−1 at 0.25 A g−1 and 182 mAh g−1 at 7 A g−1. In addition, the cathode exhibits a long-term cyclability with 93% capacity retention over 1200 cycles at 5 A g−1. VS4/CNTs with superior electrochemical performance is a hopeful cathode material in AZIBs.

An aqueous zinc pyrovanadate nanowire cathode doped by nitrogen-doped carbon from PANI calcination for capacity and stability enhancement

An aqueous zinc pyrovanadate nanowire cathode doped by nitrogen-doped carbon from PANI calcination for capacity and stability enhancement

Orientation effect of zinc vanadate cathode on zinc ion storage performance

Rechargeable aqueous zinc-ion battery (ZIB) is considered as a promising energy storage device due to the low cost, high obtainable output voltage, non-toxicity, and environmental friendliness. To achieve an excellent energy storage performance, morphology engineering of cathode materials for aqueous ZIBs is regarded as an important strategy. The impact of dimension and orientation of the cathode material on the electrochemical performance are, however, less studied. Herein, we compare two types of zinc pyrovanadate (Zn3V2O7(OH)2•2H2O, ZnVO) in nanowires and nanoflakes with the same crystal type but different orientations. ZnVO nanowires expose mostly the (001) plane lattice, in contrast to (020) and (110) lattice for ZnVO flakes. Interestingly, nanowires exhibit an excellent specific discharge capacity of 108 mAh g−1 after 700 cycles at 2 A g−1, contributed from Faradic and diffusion-controlled capacity. In contrast, nanoflakes deliver a very poor capacity of 1.5 mAh g−1 after 700 cycles at 0.1 A g−1 with only diffusion-controlled capacity. Density functional theory (DFT) reveals significantly different Zn2+ ion diffusion rates in ZnVO along different orientations.

A porous puckered V2O5 polymorph as new high performance cathode material for aqueous rechargeable zinc batteries

Aqueous rechargeable zinc batteries are getting increasing attention for large-scale energy storage owing to their advantages in terms of cost, environmental friendliness and safety. Here, the layered puckered γ′-V2O5 polymorph with a porous morphology is firstly introduced as cathode for an aqueous zinc battery system in a binary Zn2+/Li+ electrolyte. The Zn|| γ′-V2O5 cell delivers high capacities of 240 and 190 mAh g−1 at current densities of 29 and 147 mA g−1, respectively, and remarkable cycling stability in the 1.6 V–0.7 V voltage window (97% retention after 100 cycles at 0.15 A g−1). The detailed structural evolution during first discharge-charge and subsequent cycling is investigated using X-ray diffraction and Raman spectroscopy. We demonstrate a reaction mechanism based on a selective Li insertion in the 1.6 V–1.0 V voltage range. It involves a reversible exchange of 0.8 Li+ in γ′-V2O5 and the same structural response as the one reported in lithiated organic electrolyte. However, in the extended 1.6 V–0.7 V voltage range, this work puts forward a concomitant and gradual phase transformation from γ′-V2O5 to zinc pyrovanadate Zn3V2O7(OH)2.2H2O (ZVO) during cycling. Such mechanism involving the in-situ formation of ZVO, known as an efficient Zn and Li intercalation material, explains the high electrochemical performance here reported for the Zn|| γ′-V2O5 cell. This work highlights the peculiar layered-puckered γ′-V2O5 polymorph outperforms the conventional α-V2O5 with a huge improvement of capacity of 240 mAh g−1 vs 80 mAh g−1 in the same electrolyte and voltage window.

Density-functional study of pressure-induced phase transitions and electronic properties of Zn2V2O7.

We report a study of the high-pressure behavior of the structural and electronic properties of Zn2V2O7 by means of first-principle calculations using the CRYSTAL code. Three different approaches have been used, finding that the Becke–Lee–Yang–Parr functional is the one that best describes Zn2V2O7. The reported calculations contribute to the understanding of previous published experiments. They support the existence of three phase transitions for pressures smaller than 6 GPa. The crystal structure of the different high-pressure phases is reported. We have also made a systematic study of the electronic band-structure, determining the band-gap and its pressure dependence for the different polymorphs. The reported results are compared to previous experimental studies. All the polymorphs of Zn2V2O7 have been found to have a wide band gap, with band-gap energies in the near-ultraviolet region of the electromagnetic spectrum.

Fast Zn2+ kinetics of vanadium oxide nanotubes in high-performance rechargeable zinc-ion batteries

Mild aqueous rechargeable Zn-ion batteries emerge as potential grid energy storage devices due to excellent cycling stability, high Coulombic efficiency and low cost. However, reliable cathodes with high rate capability still need to be optimized. Previous vanadium oxide cathodes generally show the mechanism of Zn2+ intercalation into crystal layers, during which the lattice structure of active materials keeps stable. Different from this intercalation mechanism, here, we report a special conversion mechanism of Zn2+ storage. Vanadium oxide nanotubes with interlaminar dodecylamine are employed as the cathode. During the initial activation process, the cathode is fully converted to layered zinc pyrovanadate with amorphous zones induced by protonated dodecylamine, while the discharge process results in reversible formation of an amorphous-phase product during cycling. Layered zinc pyrovanadate can be electrochemically recovered from the amorphous phase after the Zn2+ de-intercalation. Despite an armorphous phase as the discharge product, this active material shows high cycling stability and fast Zn2+ kinetics. In addition, this cathode displays a specific energy density of ~242.5 Wh kg−1 and shows capacity retention of 80.5% after 950 cycles at 2.4 A g−1. Even at a high current density of 9.6 A g−1, the cathode delivers a specific energy of ~50 Wh kg−1 (5460 W kg−1) in 33 s. Although vanadium oxide nanotubes with interlaminar dodecylamine ions show little success in Li/Na-ion batteries with non-aqueous electrolytes, a mild aqueous Zn-ion system rejuvenates this material.

Stitching of Zn3(OH)2V2O7·2H2O 2D Nanosheets by 1D Carbon Nanotubes Boosts Ultrahigh Rate for Wearable Quasi-Solid-State Zinc-Ion Batteries.

Several layer-structured vanadates of two-dimensional (2D) nanosheet morphologies have been investigated recently for flexible quasi-solid-state aqueous zinc-ion batteries (ZIBs), where one of the challenging issues is the poor electronic conductivity and mechanical stability especially in the cross-2D nanosheet direction, leading to insufficient rate capability and mechanical stability and shortened cycle life. Herein, we have devised a strategy of using one-dimensional (1D) carbon nanotubes (CNTs) to stitch zinc pyrovanadate (Zn3(OH)2V2O7·2H2O, CNT-stitched ZVO) 2D nanosheets that are directly grown on oxidized CNT fiber (CNT-stitched ZVO NSs@OCNT fiber). With the CNT-stitched 2D nanosheet structure, the open frameworks of ZVO provide required spacing for reversible Zn2+ (de)intercalation, and the stitching CNTs offer the desperately needed electronic conductivity and mechanical robustness across the ZVO 2D nanosheets. As a result, the fiber-shaped quasi-solid-state ZIB, assembled using the CNT-stitched ZVO NSs@OCNT as the cathode and Zn NSs@CNT fiber (electrodeposited zinc nanosheets on CNT fiber) as the anode, demonstrates an ultrahigh rate capability (69.7% retention after a 100-fold increase in current density), an impressively stack volumetric energy density of 71.6 mWh cm-3, together with a long-term stability (88.6% retention after 2000 cycles). The present work proves the proof-of-concept of developing 2D nanosheets purposely stitched together by 1D conducting nanotubes/nanowires as a class of advanced cathodes for quasi-solid-state ZIBs in future portable electronics.

Fabrication of Zinc pyrovanadate (Zn3(OH)2V2O7·2H2O) nanosheet spheres as an ethanol gas sensor

It is necessary to conveniently and quickly detect the concentrations of ethanol in different environments. A new type of zinc pyrovanadate (Zn3(OH)2V2O7·2H2O) nanosheet spheres is obtained by a convenient single cation-exchange process using sodium vanadate (Na5V12O32) nanowires as precursor, without introducing any surfactant as a catalyst or structure-directing agent. During the exchange of Zn2+ and Na + ions, the Na5V12O32 nanowires gradually transfer to Zn3(OH)2V2O7·2H2O nanosheet spheres along with dissolution of the precursor and precipitation of new nanosheets. The synthetic mechanism of Zn3(OH)2V2O7·2H2O nanosheet spheres is studied by examining the changes of morphological properties of intermediate products at different times. Gas sensors based on these Zn3(OH)2V2O7·2H2O nanosheet spheres are tested. The sensor displays a response value of 1.68–100 ppm concentration of ethanol gas, and reveals a relatively high sensitivity at a relatively low optimal operating temperature of 300 °C, as well as relatively good stability.

Porous V2O5 nanofibers as cathode materials for rechargeable aqueous zinc-ion batteries

Abstract Rechargeable aqueous zinc-ion batteries are recently gaining incremental attention because of low cost and material abundance, but their development is plagued by limited choice of cathode materials with satisfactory cycling performance. Here, we report a porous V2O5 nanofibers cathode with high Zn-storage performance in an aqueous Zn(CF3SO3)2 electrolyte. We propose a reaction mechanism based on phase transition from orthorhombic V2O5 to zinc pyrovanadate on first discharging and reversible Zn2+ (de)intercalation in the open-structured hosts during subsequent cycling. This open and stable architecture enables a high reversible capacity of 319 mAh g−1 at 20 mA g−1 and a capacity retention of 81% over 500 cycles. The remarkable electrochemical performance makes V2O5 a promising cathode for aqueous zinc-ion batteries.

Rechargeable Aqueous Zinc-Ion Battery Based on Porous Framework Zinc Pyrovanadate Intercalation Cathode.

In this work, a microwave approach is developed to rapidly synthesize ultralong zinc pyrovanadate (Zn3 V2 O7 (OH)2 ·2H2 O, ZVO) nanowires with a porous crystal framework. It is shown that our synthesis strategy can easily be extended to fabricate other metal pyrovanadate compounds. The zinc pyrovanadate nanowires show significantly improved electrochemical performance when used as intercalation cathode for aqueous zinc-ion battery. Specifically, the ZVO cathode delivers high capacities of 213 and 76 mA h g-1 at current densities of 50 and 3000 mA g-1 , respectively. Furthermore, the Zn//ZVO cells show good cycling stability up to 300 cycles. The estimated energy density of this Zn cell is ≈214Wh kg-1 , which is much higher than commercial lead-acid batteries. Significant insight into the Zn-storage mechanism in the pyrovanadate cathodes is presented using multiple analytical methods. In addition, it is shown that our prototype device can power a 1.5 V temperature sensor for at least 24 h.

Mechanism of thermal expansion of structural modifications of zinc pyrovanadate

Crystal chemical characteristics of the α and β modifications of Zn2V2O7 are calculated based on in situ high-temperature X-ray measurements. The expansion of the structure is found to be strongly anisotropic up to the negative volumetric thermal expansion of the α-Zn2V2O7 unit cell in the temperature range of 300–600°С, α V =–17.94 × 10–6 1/K. The transformations of the “hard” and “soft” sublattices with an increase temperature and at the phase transition are considered in detail. It is shown that the negative volumetric thermal expansion of α-Zn2V2O7 is due to the degeneracy of the zigzag-like shape of zinc–oxygen columns at constant distances between their vertices.

Stabilizing the associated non-autonomous phase upon thermal expansion of Zn2V2O7

The previously unknown effect of emergence of an associated non-autonomous phase upon heating of zinc pyrovanadate Zn2V2O7 within the region of negative volume expansion is detected. Comparison of the data of high-temperature X-ray diffraction of the Zn2V2O7 samples synthesized via solution and solid-phase routes shows that the grain size affects the stabilization of the non-autonomous phase. The presence of a non-autonomous phase results in self-dispersion of the substance upon phase transition in heating–cooling cycles.