Nanocrystallites of vanadium pentoxide were synthesized by the hydrothermal treatment of electrospun composite nanofibers. Each crystallite of dimension ⩽100 nm was found to be a single crystal of δ-phase HxV4O10 · nH2O. The crystallinity and morphology was maintained on heating to 500 °C when V2O5 was formed. The electrochemical capacity of the nano-V2O5 in a lithium cell was found to be above 350 mAh/g. The columbic efficiency is close to 100% when small amounts of lithium bis(oxalato)borate is added to the LiPF6 electrolyte.