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

Using an electrochemical potential pulse methodology in a mixed solvent system, electrochemical deposition of amorphous vanadium pentoxide (V 2 O 5 ) 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 V 2 O 5 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-Li 3 V 2 O 5 formation. Aberration corrected scanning TEM confirm the formation of ω-Li 3 V 2 O 5 across the entirety of a nanobelt during discharge and also the reversible formation of the α-V 2 O 5 phase upon full charge. Preliminary second cycle studies reveal reformation of the ω-Li 3 V 2 O 5 , accompanied with a morphological change in the nanobelt dimensions. Achieving α-V 2 O 5 to ω-Li 3 V 2 O 5 to α-V 2 O 5 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 V 2 O 5 materials and never before with electrodeposited material. Figure 1