High capacity and enhanced structural reversibility of β-LixV2O5 nanorods as the lithium battery cathode

LixV2O5 (x similar to 0.42) nanorods, an overdoped beta-phase vanadium oxide bronze with a rigid three-dimensional framework, have been fabricated for the first time via a simple two-step synthetic method. It is found that the delta-type structure of the as-prepared hydrated nanobelts through the hydrothermal route is converted into the tunnel beta geometry upon annealing-induced dehydration. After annealing at 600 degrees C, the beta-LixV2O5 nanorods exhibit the desired electrochemical properties: an initial gravimetric discharge capacity of 388.4 mA h g(-1) (corresponding to an uptake of ca. 2.68 lithium per cell unit) and a specific energy density of 1039.6 W h kg(-1) are achieved within a 2.0 V cut-off voltage at C/20, which decreased to 295.3 mA h g(-1) (ca. 2.04 Li/V2O5) and 789.0 W h kg(-1) after 50 cycles, respectively. The irreversible formation of omega-LixV2O5 for layered V2O5 cathodes upon deep lithiation is not presented during cell operation, and such improved structural reversibility is attributed to the highly retrievable host framework of the beta-Li bronze, as well as further strain relaxation facilitated by the one-dimensional nanostructures. Based on the distinctive crystallographic structure and superior electrochemical properties, this beta-lithium vanadium bronze has shown promising potential as a cathode material for secondary lithium-based batteries.