| Autor: |
Augustsson, A., Schmitt, T., Duda, L.-C., Nordgren, J., Nordlinder, S., Edström, K., Gustafsson, T., Guo, J.-H. |
| Předmět: |
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| Zdroj: |
Journal of Applied Physics; 10/15/2003, Vol. 94 Issue 8, p5083, 5p, 1 Chart, 4 Graphs |
| Abstrakt: |
The effect of lithium insertion (lithiation) in electrodes of vanadium oxide nanotubes has been studied using resonant soft-x-ray emission spectroscopy (RSXES) and soft x-ray absorption spectroscopy (SXAS). Spectra at the V L edges were recorded ex-situ on a series of cycled electrodes that had been discharged to different potentials (3.0, 2.5, 2.0, and 1.8 V). Different chemical states upon discharge effectively correspond to different doping levels: the lower the cell potential, the higher the lithiation. The RSXES and SXAS spectra reflect the occupied and unoccupied electronic states, respectively. Spectral changes are observed as a function of the reduction process of vanadium by the electrochemical process. Lithiation induces a gradual enhancement of features attributed to occupied V 3d states in the RSXES spectra, indicating that the intercalated charges occupy bands of V 3d. Both SXAS and RSXES results suggest a partial reduction to V[sup 3+] at potentials below 2.0 V and the presence of a mixture of three different oxidation states. RSXES spectra also reveal the low energy-loss feature of 1 eV, suggesting strong correlation of the V 3d orbitals. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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