Synthesis of mesoporous β-Na0.33V2O5 with enhanced electrochemical performance for lithium ion batteries

Sodium-Vanadium Bronze Na9V14O35: An Electrode Material for Na-Ion Batteries

Na₉V₁₄O₃₅ (η-Na_xV₂O₅) has been synthesized via solid-state reaction in an evacuated sealed silica ampoule and tested as electroactive material for Na-ion batteries. According to powder X-ray diffraction, electron diffraction and atomic resolution scanning transmission electron microscopy, Na₉V₁₄O₃₅ adopts a monoclinic structure consisting of layers of corner- and edge-sharing VO₅ tetragonal pyramids and VO₄ tetrahedra with Na cations positioned between the layers, and can be considered as sodium vanadium(IV,V) oxovanadate Na₉V₁₀^4.1+O₁₉(V⁵⁺O₄)₄. Behavior of Na₉V₁₄O₃₅ as a positive and negative electrode in Na half-cells was investigated by galvanostatic cycling against metallic Na, synchrotron powder X-ray diffraction and electron energy loss spectroscopy. Being charged to 4.6 V vs. Na⁺/Na, almost 3 Na can be extracted per Na₉V₁₄O₃₅ formula, resulting in electrochemical capacity of ~60 mAh g⁻¹. Upon discharge below 1 V, Na₉V₁₄O₃₅ uptakes sodium up to Na:V = 1:1 ratio that is accompanied by drastic elongation of the separation between the layers of the VO₄ tetrahedra and VO₅ tetragonal pyramids and volume increase of about 31%. Below 0.25 V, the ordered layered Na₉V₁₄O₃₅ structure transforms into a rock-salt type disordered structure and ultimately into amorphous products of a conversion reaction at 0.1 V. The discharge capacity of 490 mAh g⁻¹ delivered at first cycle due to the conversion reaction fades with the number of charge-discharge cycles.

Uniform β-Na0.33V2O5 nanorod cathode providing superior rate capability for lithium ion batteries

A vanadium bronze nanomaterial, β-Na_0.33V₂O₅, was synthesized using a facile sol-gel method followed by annealing at high temperature. The morphology of the sample was observed using a scanning electron microscope (SEM) and a transmission electron microscope (TEM), and the crystal phase was determined by x-ray diffraction (XRD) spectroscopy. The as-prepared sample displays a morphology of nanorods, and has a pure phase with a high crystallinity. When used as the cathode material for rechargeable lithium batteries, the β-Na_0.33V₂O₅ nanorods fired at 400 °C exhibit better electrochemical properties at a 2.0 V cutoff voltage than those at a 1.5 V cutoff voltage. Over the voltage range of 2.0-4.0 V, they can deliver an initial capacity of 221 mAh g^-1 at a 0.5 C rate, and retain 212 mAh g^-1 after 200 cycles, accounting for a capacity fading of only 0.02% per cycle. At a 5 C rate, the discharge capacity still reaches 146 mAh g^-1, displaying an outstanding rate capability. Control of the electrochemical window is proved to be an effective strategy in boosting the cycling stability of the β-Na_0.33V₂O₅ cathode in this work in spite of a discounted capacity. Results suggest the as-prepared β-Na_0.33V₂O₅ nanorods are promising for use as high-performance cathode materials for rechargeable lithium batteries.

Electrochemical Properties of Na0.66V4O10 Nanostructures as Cathode Material in Rechargeable Batteries for Energy Storage Applications

We report the electrochemical performance of nanostructures of Na0.66V4O10 as cathode material for rechargeable batteries. The Rietveld refinement of room-temperature X-ray diffraction pattern shows the monoclinic phase with C2/m space group. The cyclic voltammetry curves of prepared half-cells exhibit redox peaks at 3.1 and 2.6 V, which are due to two-phase transition reaction between V5+/4+ and can be assigned to the single-step deintercalation/intercalation of Na ion. We observe a good cycling stability with specific discharge capacity (measured vs Na+/Na) between 80 (±2) and 30 (±2) mAh g-1 at current densities of 3 and 50 mA g-1, respectively. The electrochemical performance of Na0.66V4O10 electrode was also tested with Li anode, which showed higher capacity but decayed faster than Na. Using density functional theory, we calculate the Na vacancy formation energies: 3.37 eV in the bulk of the material and 2.52 eV on the (100) surface, which underlines the importance of nanostructures.

Synthesis and electrochemical performance of NaV3O8 nanobelts for Li/Na-ion batteries and aqueous zinc-ion batteries

NaV₃O₈ nanobelts were successfully synthesized for Li/Na-ion batteries and rechargeable aqueous zinc-ion batteries (ZIBs) by a facile hydrothermal reaction and subsequent thermal transformation. Compared to the electrochemical performance of LIBs and NIBs, NaV₃O₈ nanobelt cathode materials in ZIBs have shown excellent electrochemical performance, including high specific capacity of 421 mA h g⁻¹ at 100 mA g⁻¹ and good cycle stability with a capacity retention of 94% over 500 cycles at 5 A g⁻¹. The good diffusion coefficients and high surface capacity of NaV₃O₈ nanobelts in ZIBs were in favor of fast Zn²⁺ intercalation and long-term cycle stability.

Compared to the electrochemical performance for LIBs and NIBs, NaV₃O₈ nanobelts electrode for ZIBs shows excellent electrochemical performance, including high specific capacity of 421 mA h g⁻¹ at 100 mA g⁻¹, good rate performance and cycle performance.

Electrospun Single Crystalline Fork-Like K2V8O21 as High-Performance Cathode Materials for Lithium-Ion Batteries

Single crystalline fork-like potassium vanadate (K₂V₈O₂₁) has been successfully prepared by electrospinning method with a subsequent annealing process. The as-obtained K₂V₈O₂₁ forks show a unique layer-by-layer stacked structure. When used as cathode materials for lithium-ion batteries, the as-prepared fork-like materials exhibit high specific discharge capacity and excellent cyclic stability. High specific discharge capacities of 200.2 and 131.5 mA h g⁻¹ can be delivered at the current densities of 50 and 500 mA g⁻¹, respectively. Furthermore, the K₂V₈O₂₁ electrode exhibits excellent long-term cycling stability which maintains a capacity of 108.3 mA h g⁻¹ after 300 cycles at 500 mA g⁻¹ with a fading rate of only 0.043% per cycle. The results demonstrate their potential applications in next-generation high-performance lithium-ion batteries.

Synthesis and electrochemical performance of NaV6O15 microflowers for lithium and sodium ion batteries

High first discharge capacity of 255 mA h g⁻¹ (vs. Li⁺/Li) and 130 mA h g⁻¹ (vs. Na⁺/Na) were observed in NaV₆O₁₅ microflowers and the capacity retention reaches 105% and 64% after 50 cycles at the current density of 100 mA g⁻¹ and 50 mA g⁻¹, respectively.

Template-free synthesis of highly porous V2O5 cuboids with enhanced performance for lithium ion batteries

Highly porous hierarchical V2O5 cuboids have been synthesized by a template-free PVP-assisted polyxol method and the formation mechanism is studied. The cuboids are assembled from numerous mesoporous nanoplates and the preferred orientation of each single nanoplate exposes the 〈110〉 facets, facilitating lithium-ion diffusion by offering a prior channel. This material exhibits a high capacity of 143 mA h g(-1), high rate capacity of 10 C and long life cycling performance up to 1000 cycles. The excellent electrochemical performance of V2O5 cuboid electrodes is due to its unique porous cuboid morphology and optimized structural stability upon cycling. This research provides an effective route to the construction of complex porous architectures assembled from nanocrystals through a surfactant-assisted synthesis method.

Flexible additive free H2V3O8nanowire membrane as cathode for sodium ion batteries

A flexible additive free H₂V₃O₈nanowire membrane is presented as a promising sodium-ion battery cathode.

In situ soft-chemistry synthesis of β-Na0.33V2O5 nanorods as high-performance cathode for lithium-ion batteries

β-Na_0.33V₂O₅ nanorods were prepared via a facile soft-chemistry strategy using Na⁺ intercalated (NH₄)_0.5V₂O₅ nanosheets as precursor.

Facile Synthesis of Na0.33V2O5 Nanosheet-Graphene Hybrids as Ultrahigh Performance Cathode Materials for Lithium Ion Batteries

Na0.33V2O5 nanosheet-graphene hybrids were successfully fabricated for the first time via a two-step route involving a novel hydrothermal method and a freeze-drying technique. Uniform Na0.33V2O5 nanosheets with a thickness of about 30 nm are well-dispersed between graphene layers. The special sandwich-like nanostructures endow the hybrids with high discharge capacity, good cycling stability, and superior rate performance as cathodes for lithium storage. Desirable discharge capacities of 313, 232, 159, and 108 mA·h·g(-1) can be delivered at 0.3, 3, 6, and 9 A·g(-1), respectively. Moreover, the Na0.33V2O5-graphene hybrids can maintain a high discharge capacity of 199 mA·h·g(-1) after 400 cycles even at an extremely high current density of 4.5 A·g(-1), with an average fading rate of 0.03% per cycle.

New chemical route for the synthesis of β-Na(0.33)V₂O₅ and its fully reversible Li intercalation

To obtain good electrochemical performance and thermal stability of rechargeable batteries, various cathode materials have been explored including NaVS2, β-Na(0.33)V2O5, and Li(x)V2O5. In particular, Li(x)V2O5 has attracted attention as a cathode material in Li-ion batteries owing to its large theoretical capacity, but its stable electrochemical cycling (i.e., reversibility) still remains as a challenge and strongly depends on its synthesis methods. In this study, we prepared the Li(x)V2O5 from electrochemical ion exchange of β-Na(0.33)V2O5, which is obtained by chemical conversion of NaVS2 in air at high temperatures. Crystal structure and particle morphology of β-Na(0.33)V2O5 are characterized by using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy techniques. Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy, in combination with electrochemical data, suggest that Na ions are extracted from β-Na(0.33)V2O5 without irreversible structural collapse and replaced with Li ions during the following intercalation (i.e., charging) process. The thus obtained Li(x)V2O5 delivers a high discharge capacity of 295 mAh g(-1), which corresponds to x = 2, with crystal structural stability in the voltage range of 1.5-4.0 V versus. Li, as evidenced by its good cycling performance and high Coulombic efficiency (under 0.1 mA cm(-2)) at room temperature. Furthermore, the ion-exchanged Li(x)V2O5 from β-Na(0.33)V2O5 shows stable electrochemical behavior without structural collapse, even at a case of deep discharge to 1.5 V versus Li.

Synthesis of novel ammonium vanadium bronze (NH4)0.6V2O5 and its application in Li-ion battery

A novel ammonium vanadium bronze (NH₄)_0.6V₂O₅ has been successfully synthesized via a simple hydrothermal treatment and its electrochemical performance is investigated.

Template-free synthesis of β-Na0.33V2O5microspheres as cathode materials for lithium-ion batteries

Hierarchical nanosheet-assembled β-Na_0.33V₂O₅microspheres have been fabricated by a solvothermal method with subsequent calcination in air, and exhibit high specific capacity and good rate capability.