Atomic-scale investigation of the reversible α- to ω-phase lithium ion charge – discharge characteristics of electrodeposited vanadium pentoxide nanobelts. Issue 15 (18th March 2022) - Hussein, Haytham E. M.
Abstract : Electrodeposition is used to produce α-V2 O5 nanobelts on a boron doped diamond electrode. The nanoscale dimensions facilitate accommodation of three Li + ions during discharge resulting in ω-Li3 V2 O5, which is reversible over at least one cycle. Abstract : Using an electrochemical potential pulse methodology in a mixed solvent system, electrochemical deposition of amorphous vanadium pentoxide (V2 O5 ) 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 V2 O5 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-Li3 V2 O5 formation. Aberration corrected scanning TEM confirm the formation of ω-Li3 V2 O5 across the entirety of a nanobelt during discharge and also the reversible formation of the α-V2 O5 phase upon full charge. Preliminary second cycle studies reveal reformation of the ω-Li3 V2 O5, accompanied with a morphological change in the nanobelt dimensions. Achieving α-V2 O5 to ω-Li3 V2 O5 to α-V2 O5 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 V2 O5 materials and never before with electrodeposited material.