Ultra-long Na2V6O16·xH2O nanowires: large-scale synthesis and application in binder-free flexible cathodes for lithium ion batteries

Large-scale synthesis and application of ultra-long Na₂V₆O₁₆·xH₂O nanowires as binder-free flexible cathodes for high performance LIBs are demonstrated.

Structure and properties of vanadium(V)-doped hexagonal turbostratic birnessite and its enhanced scavenging of Pb²⁺ from solutions

Vanadium(V)-doped hexagonal turbostratic birnessites were synthesized and characterized by multiple techniques and were used to remove Pb(2+) from aqueous solutions. With increasing V content, the V(V)-doped birnessites have significantly decreased crystallinity, i.e., the thickness of crystals in the c axis decreases from 9.8 nm to ∼0.7 nm, and the amount of vacancies slightly increases from 0.063 to 0.089. The specific surface areas of these samples increase after doping while the Mn average oxidation sates are almost constant. V has a valence of +5 and tetrahedral symmetry, and exists as oxyanions, including V₆O₁₆(2-), and VO4(3-) on birnessite edge sites by forming monodentate corning-sharing complexes. Pb LIII-edge extended X-ray absorption fine structure (EXAFS) spectra analysis shows that, at low V contents (V/Mn≤0.07) Pb(2+) mainly binds with birnessite on octahedral vacancy and especially edge sites whereas at higher V contents (V/Mn>0.07) more Pb(2+) associates with V oxyanions and form vanadinite [Pb₅(VO₄)₃Cl]-like precipitates. With increasing V(V) content, the Pb(2+) binding affinity on the V-doped birnessites significantly increases, ascribing to both the formation of the vanadinite precipitates and decreased particle sizes of birnessite. These results are useful to design environmentally benign materials for treatment of metal-polluted water.

Novel aligned sodium vanadate nanowire arrays for high-performance lithium-ion battery electrodes

One-dimensional (1D) Na₅V₁₅O₃₂ nanowire arrays have been fabricated which exhibit remarkable electrochemical performances in secondary organic lithium batteries.

Na₂V₆O₁₆·xH₂O nanoribbons: large-scale synthesis and visible-light photocatalytic activity of CO₂ into solar fuels

An ultra-thin and super-long Na₂V₆O₁₆·xH₂O nanoribbon of ∼5 nm thickness and ∼500 μm length was synthesized by a hydrothermal method, using a freshly prepared V(3+) species precursor solution by directly dissolving a vanadium metal thread in a NaNO₃ solution using a solid-liquid phase arc discharge (SLPAD) technique. Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques were used to characterize the structure, morphology, and chemical composition. The super-long and ultra-thin geometry of the Na₂V₆O₁₆·xH₂O nanoribbons is proven to greatly promote the photocatalytic activity toward reduction of CO₂ into renewable hydrocarbon fuel (CH₄) in the presence of water vapor under visible-light irradiation.

Synthesis of Na(1.25)V(3)O(8) nanobelts with excellent long-term stability for rechargeable lithium-ion batteries

Sodium vanadium oxide (Na1.25V3O8) nanobelts have been successfully prepared by a facile sol-gel route with subsequent calcination. The morphologies and the crystallinity of the as-prepared Na1.25V3O8 nanobelts can be easily controlled by the calcination temperatures. As cathode materials for lithium ion batteries, the Na1.25V3O8 nanobelts synthesized at 400 °C exhibit a relatively high specific discharge capacity of 225 mA h g(-1) and excellent stability at 100 mA g(-1). The nanobelt-structured electrode can retain 94% of the initial capacity even after 450 cycles at the current density of 200 mA g(-1). The good electrochemical performance is attributed to their nanosized thickness and good crystallinity. The superior electrochemical performance demonstrates the Na1.25V3O8 nanobelts are promising cathode materials for secondary lithium batteries.