Innovations in Battery Material Quality Control: Microwave-Induced Atmospheric-Pressure Plasma Optical Emission Spectrometry (MICAP-OES) for Elemental Analysis

Abstract

The analysis of both, major elements (Li, Ni, Co, Mn) and impurities (e.g., Ca, Cd, Cr, Cu, Fe, Na, Pb) in final cathodes and especially in raw materials is essential for quality control in Li-based batteries industry. In recent years, Microwave-Induced Atmospheric-Pressure Plasma Optical Emission Spectrometry (MICAP OES) has emerged as a robust analytical technique for trace element determination, even in complex matrices with high concentration of total dissolved solids. Thus, the aim of this study is to evaluate the analytical capabilities of MICAP OES for quality control purposes (major and impurities determination) in different materials used in Li-based battery industry (i.e., raw materials, binary and ternary cathodes). The evaluation was conducted in accordance with the only existing regulations, which have been issued by China. Despite the complexity of the samples, no significant spectral interferences were detected for the most sensitive wavelength of the analytes, with the exception of lead (Pb), which showed interference in Mn-containing matrices. Regarding non-spectral interferences, although the method is still susceptible to matrix effects caused by sample concomitants (mainly Li), these can be effectively corrected using matrix-matched calibration standards. Furthermore, with the appropriate selection of operating conditions and the calibration strategies, both major elements and impurities can be determined simultaneously. The detection limits achieved are comparable to those afforded by ICP OES, and allow the analysis of impurities according to the Chinese standard protocols. Finally, the proposed methodology was satisfactorily validated through the analysis of a cathode reference material (NMC 111 BAM S014), 5 commercial raw materials and 9 cathode samples with different composition.