Spatially-Resolved In Situ Raman Analysis of LiCoO2 Electrodes

The potential of Raman diagnostics for spatially-resolved in situ diagnostics of LiCoO2 electrodes for lithium-ion batteries is demonstrated. In situ Raman spectra of LiCoO2 composite electrodes are characterized by LiCoO2 phonon bands as well as carbon- and electrolyte-related features. Spatially-resolved Raman analysis, i.e. Raman mapping prior electrochemical cycling reveals a variation of chemical composition across the electrode surface. Comparison of in situ spectra prior and after electrochemical cycling shows a spatially-dependent redistribution of composition as derived from changes in the LiCoO2-carbon peak ratios. The results of the in situ mapping experiments are dicussed in the context of degradation of lithium-ion batteries.