Unidirectional growth of single crystalline beta-Na0.33V2O5 and alpha-V2O5 nanowires driven by controlling the pH of aqueous solution and their electrochemical performances for Na-ion batteries

Abstract

We describe a novel synthetic route of highly single crystalline sodium vanadate (beta-Na0.33V2O5) and vanadium pentoxide (alpha-V2O5) nanowires via a simple thermal annealing process followed by the formation of amorphous nanoparticles of V(OH)(3) and Na-containing V(OH)(3) precursors prepared by controlling the pH of precursor solutions. The distinct crystal growth process suggests that the intercalation of Na ions is governed by the pH of the aqueous solution. In addition, the binding nature to the amorphous V(OH)(3) nanoparticle precursors could be a key factor in determining the unidirectional growth of highly single crystalline beta-Na0.33V2O5 and alpha-V2O5 nanowires. The obtained single crystalline beta-Na0.33V2O5 nanowire shows promising electrode performance for sodium-ion batteries (SIB) with greater discharge capacity and better rate characteristics compared with those of the alpha-V2O5 nanowire. The superior electrode functionality of beta-Na0.33V2O5 over alpha-V2O5 is attributable to its better charge transfer kinetics and its higher structural and morphological stability.