Materials Chemistry

Atomic-Scale Investigation of the Reversible alpha to omega-Phase Lithium Ion Charge – Discharge Characteristics of Electrodeposited Vanadium Pentoxide Nanobelts

Authors

Abstract

Using an electrochemical potential pulse methodology in a mixed solvent system, electrochemical deposition of amorphous vanadium pentoxide (V2O5) nanobelts is possible. Crystallisation of the material is achieved using in air annealing with the temperature of crystallisation identified using in-situ heating transmission electron microscopy (TEM). The resulting alpha-phase V2O5 nanobelts have typical thicknesses of 10-20 nm, widths and lengths in the range 5-37 nm (mean 9 nm) and 15 - 221 nm (mean 134 nm), respectively. One-cycle reversibility studies for lithium intercalation (discharge) and de-intercalation (discharge) reveal a maximum specific capacity associated with three lithium ions incorporated per unit cell, indicative of omega-Li3V2O5 formation. Aberration corrected scanning TEM confirm the formation of omega-Li3V2O5 across the entirety of a nanobelt during discharge and also the reversible formation of the alpha-V2O5 phase upon full charge. Preliminary second cycle studies reveal reformation of the omega-Li3V2O5, accompanied with a morphological change in the nanobelt dimensions. Achieving alpha-V2O5 to omega-Li3V2O5 phase reversibility is extremely challenging given the large structural rearrangements required. This phenomenon has only been seen before in a very limited number of studies also employing nanosized V2O5 materials and never before with electrodeposited nanocrystals.

Content

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Supplementary material

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Supporting Information
1.Experimental set-up for electrodeposition and Li intercalation using the BDD-TEM electrode 2. Illustration of the in-situ TEM heating set-up, 3. Chronoamperometric response of vanadium sulphate solution in a water-DMF mixed solvent 4.In-situ TEM thermal annealing of V2O5 from amorphous to crystalline 5.Statistical analysis of the V2O5 NBs dimensions and size 6.XPS survey spectrum of the crystalline V2O5 NBs 7. Unknown vanadium oxide polymorphs 8.The crystalline structure of α-V2O5 9. Electron dose and additional observations of VO surface layers 10. CV data of the first discharge/charge cycle in a solution of 1 M LiCl, XPS and XRD of the V2O5 structure post Li intercalation (Li insertion), 11. XPS and XRD of the V2O5 structure post Li deintercalation (Li removal) 12. Electrochemical response during the second discharge and charge cycle and the formation of ordered Li3V2O5 structure. 13. Low magnification STEM images of V2O5 structures after lithiation and delithiation cycles, and References