Quantification of lithium in LIB electrodes with glow discharge optical emission spectroscopy (GD-OES)

Abstract Glow discharge optical emission spectroscopy (GD-OES) was applied to quantification of Li in both positive and negative electrodes. Depth profiles of Li 1.03 Ni 0.32 Co 0.33 Mn 0.32 O 2 (NCM) and hard carbon based electrodes in the range of state of charge (SOC) 0–100% were measured throughout from the surface to the current collector within a few hours. The flat crater shapes, although slightly concave at the edge for NCM, suggested a good depth resolution in the profiles. The sample surfaces sputtered during the GD-OES measurement were smooth in SEM observation, suggesting that remarkable preferential sputtering of the composite materials did not occur. The Li intensities obtained from GD-OES were correlated with the Li components determined using ICP-MS for both positive and negative electrode samples. The correlation coefficients of the linear relationship were improved by considering intensity ratio of Li to the matrix element, Li/Co and Li/C for NCM and hard carbon electrodes, respectively, to correct the sputtering rate variation of samples. These results confirm that GD-OES is a potential technique for quantitative analysis of Li in the electrodes.