X-ray Absorption Spectroscopy Study of Cu0.25V2O5 and Zn0.25V2O5 Aerogel-Like Cathodes for Lithium Batteries

Vanadium pentoxide materials prepared through sol-gel processes (xerogel, aerogel, and aerogel-like) act as excellent intercalation hosts for lithium as well as polyvalent cations. The large lithium insertion capacity of these materials makes them attractive for use as cathodes in high-capacity lithium batteries. The local structural modifications resulting from low dopant concentration (copper and zinc) in V2O5 aerogel-like material have been investigated by X-ray absorption spectroscopy (XAS). To study the structural sites of the polyvalent ions, extended X-ray absorption fine structure (EXAFS) spectra have been recorded at the vanadium, zinc, and copper K edges. The EXAFS analysis shows that the vanadium atomic environment is almost the same for Cu0.25V2O5 and Zn0.25V2O5. Furthermore, the doping metals (Cu and Zn) are found to be in the same site. Copper and zinc are 4-fold coordinated by almost-coplanar oxygens. This suggests a preferred site for the doping metal (M) and the same interaction between the vanadium and the doping metals. M-O first-shell distances are shorter for the copper compared to those for the zinc, and we have found higher disorder in the Zn0.25V2O5 compound compared to that in Cu0.25V2O5. No interactions between metal-metal sites were found because the metal doping level was too small.