Synthesis of a metastable vanadium pentoxide as a cathode material for ion batteries
A highly scalable process has been developed for stabilizing large quantities of the zeta-polymorph of V 2 O 5 , a metastable kinetically trapped phase, with high compositional and phase purity. The process utilizes a beta-Cux V 2 O 5 precursor which is synthetized from solution using all-soluble precursors. The copper can be leached from this structure by a room temperature post-synthetic route to stabilize an empty tunnel framework entirely devoid of intercalating cations. The metastable ζ-V 2 O 5 thus stabilized can be used as a monovalent-(Li, Na) or multivalent-(Mg, Ca, Al) ion battery cathode material.
1. A method of making ζ-V 2 O 5 nanowires comprising:
hydrothermally reacting soluble vanadium source, wherein the vanadium is 4+, 5+, or a combination thereof, and a copper source, wherein copper is 1+ or 2+, in the presence of a reducing agent to provide β-Cu x V 2 O 5 (0.33<x<0.66) nanowires; and
reacting the β-Cu x V 2 O 5 nanowires in solution containing an oxidizing agent, thereby topochemically leaching Cu ions from the β-Cu x V 2 O 5 nanowires to provide ζ-V 2 O 5 nanowires, said ζ-V 2 O 5 nanowires showing no copper signal when analyzed by energy dispersive X-ray spectroscopy.
2. The method of claim 1 , wherein a molar ratio between the vanadium source and the copper source is between 6:1 and 3:1.
3. The method of claim 1 , further comprising intercalating one or more ions selected from the group consisting of Li + ions, Na + ions, Al 3+ ions, Y 3+ ions, Ca 2+ ions, Mg 2+ ions, Zn 2+ ions, and combinations thereof.
4. The method of claim 1 , wherein said solution contains a oxidizing agent selected from Na 2 S 2 O 8 , Bra, 12 , and NOBF 4 .
5. A method of making intercalated metastable ζ-V 2 O 5 nanowires comprising intercalating one or more ions selected from the group consisting of Li + ions, Na+ ions, Al 3+ ions, Y 3+ ions, Ca 2+ ions, Zn 2+ ions, Mg 2+ ions and combinations thereof into ζ-V 2 O 5 nanowires, said ζ-V 2 O 5 nanowires comprising ζ-V 2 O 5 nanowires having the formula ζ-(Cu x )V 2 O 5 wherein x is between about 0.006 and 0.33 .
6. The method of claim 5 , wherein said intercalated metastable ζ-V 2 O 5 nanowires are magnesiated, said method comprising contacting the ζ-V 2 O 5 nanowires with an organic solution of alkyl-Mg.
7. The method of claim 5 , wherein ζ-V 2 O 5 nanowires are contacted with a Mg-ion electrolyte or a Li-ion electrolyte and a voltage is applied thereby inserting Mg 2+ ions or Li + ions into the ζ-V 2 O 5 nanowires.
8. The method of claim 7 , wherein the Mg-ion electrolyte includes a solution of a Mg complex dissolved in a solvent or a Mg complex dispersed within a conductive polymer.
9. The method of claim 5 , wherein the ζ-V 2 O 5 nanowires include metastable ζ-V 2 O 5 nanowires.
10. The method of claim 5 , wherein the magnesiated metastable ζ-V 2 O 5 nanowires have lattice constants comprising: a =15.25±0.4 Å, b=3.60±0.02 Å, and c=10.10±0.03 Å.
11. The method of claim 5 , wherein the magnesiated metastable ζ-V 2 O 5 nanowires have a unit cell angle, β, between about 109.1° and about 110.9°.