Microstructural changes of amorphous V_(2)O_(5) films with lithium intercalation are studied using Raman-scattering measurements. The Raman spectra of as-deposited films show two broad peaks around at 520 and 650 cm~(-1), due to the stretching modes of the V_(3)-O and V_(2)-O bonds, respectively, and a relatively sharp peak at 1027 cm~(-1) due to the V~(5+)=O stretching mode of terminal oxygen atoms. In addition, there is a peak at 932 cm~(-1) that we attribute to the V~(4+)=O bonds. Comparison of the Raman spectra of V_(2)O_(5) films with different oxygen deficiencies confirms this assignment. This Raman peak due to the stretching mode of the V~(4+)=O bonds develops and shifts toward lower frequencies with increasing lithium concentration. Comparison to results from gasochromic hydrogen insertion indicates that the 932 cm~(-1) Raman peak is not a result of vibrations which involve Li or H atoms. We propose that the V~(4+)=O bonds are created by two different mechanisms: a direct conversion from V~(5+)=O bonds and the breaking of the single oxygen bonds involving V~(4+) ions.
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