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

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 α-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 (charge) reveal a maximum specific capacity associated with three lithium ions incorporated per unit cell, indicative of ω-Li3V2O5 formation. Aberration corrected scanning TEM confirm the formation of ω-Li3V2O5 across the entirety of a nanobelt during discharge and also the reversible formation of the α-V2O5 phase upon full charge. Preliminary second cycle studies reveal reformation of the ω-Li3V2O5, accompanied with a morphological change in the nanobelt dimensions. Achieving α-V2O5 to ω-Li3V2O5 to α-V2O5 reversibility is extremely challenging given the large structural rearrangements required. This phenomenon has only been seen before in a very limited number of studies, mostly employing nanosized V2O5 materials and never before with electrodeposited material. Figure 1