In situ Raman spectroscopic study of thin-film Li1−xMn2O4 electrodes

In order to investigate structural changes in lithium manganese oxide during the insertion and extraction of lithium ions, Raman spectra of thin films of Li1−xMn2O4 produced by electrostatic spray deposition (ESD) were recorded in situ during a voltammetric scan in 1 M LiClO4 in propylene carbonate (PD)/ethylene carbonate (EC) solutions. Five Raman-active bands, as predicted by the theory, were observed for the Li1−xMn2O4 compound. The λ-MnO2 phase has a distinct band at 592 cm−1 and therefore can be clearly recognized from Raman spectra. The changes observed in Raman lines of Li1−xMn2O4 were ascribed to the occurrence of the phase transition of Li1−xMn2O4 electrodes. From the energy-dependence of Raman spectra, it is suggested that each value of x in Li1−xMn2O4 possesses its own electronic band structure.