Quantitative lithium mapping of lithium-ion battery cathode using laser-induced breakdown spectroscopy

A method to obtain the quantitative lithium distribution of a lithium-ion battery cathode using laser-induced breakdown spectroscopy (LIBS) measurements is proposed. We perform LIBS measurements in a reduced argon atmosphere of 1000 Pa and use a calibration curve obtained by measuring the emission intensities at 610.4 nm of standard samples, whose atomic ratios of lithium to cobalt are 0, 0.10, 0.30, 0.51, 0.62, 0.80, and 0.99. The lithium distributions of cycled cathodes, which contain LiCoO₂ as an active material, obtained by this method are relatively consistent with the Co(III) distributions obtained by X-ray absorption spectroscopy (XAS). XAS is the conventional method to quantitatively display the reaction distribution of a cathode material used in a lithium-ion battery. Additionally, LIBS can detect the precipitating decomposition products of the electrolyte, LiF, on the cathode. However, the precision of the lithium ratio using LIBS is not as good as that achieved for the Co(III) ratio obtained using XAS. Therefore, LIBS is suitable to obtain a semi-quantitative lithium distribution in a cathode of a lithium-ion battery through a much simpler procedure than XAS. Furthermore, LIBS has an advantage to detect the decomposition product of the electrolyte using laboratory-scale measurements.