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 Li1.03Ni0.32Co0.33Mn0.32O2 (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.