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A novel in situ cell for Raman diagnostics of working lithium-ion batteries is described. The design closely mimics that of standard battery testing cells and therefore allows to obtain Raman spectra under representative electrochemical conditions. Both cathode and anode materials can be studied. First results on the intercalation of a Li1-xCoO2 cathode material demonstrate the potential of the experimental approach for structural studies and underline the importance of studying lithium-ion batteries at work.

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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.