Determination of Mn, Co, Ni in Ternary Cathode Materials With
Homologous Correction EDXRF Analysis
LIN Hong-jian1, ZHAI Juan1*, LAI Wan-chang1, ZENG Chen-hao1, 2, ZHAO Zi-qi1, SHI Jie1, ZHOU Jin-ge1
1. The College of Nuclear Technology and Automation Engineering, Chengdu University of Technology, Chengdu 610059, China
2. Department of Military Installation, Army Logistical University of PLA, Chongqing 401311, China
Abstract：Lithium-ion batteries play an important role in developing and applying new energy. The composition ratio of ternary cathode materials has a major impact on the performance and quality of lithium-ion battery products, and production control requires timely and accurate control of composition changes in the mix. Energy dispersive X-ray fluorescence (EDXRF) technology has a good prospect for rapid analysis in this area, but the analytical accuracy of commercial instruments cannot currently meet production requirements. To solve the technical problem of high-precision EDXRF analysis of ternary cathode material composition Mn, Co, Ni, a self-calibrating formal EDXRF analysis technology based on homologous excitation is proposed in this paper, which uses a tungsten target X-ray tube (25 kV/400 μA) and two electrically cooled SDD detectors with the energy resolution of 135 eV (@5.9 keV) to form a two-channel synchronous X-ray fluorescence excitation and detection device. After splitting the primary X-rays emitted by the X-ray tube by the dual channel collimator, the calibration sample and the sample to be measured are excited. The two detectors simultaneously measure the fluorescence counts of the two samples and use the energy spectrum data of the standard sample to perform “normalization” processing to achieve synchronous correction of the energy spectrum data of the sample to be tested, thus reducing the influence of X-ray tube instability in the analytical instrument. The stability instrument was analyzed regarding the count decay rate, count variation, and overall effect through 140 repeatability tests in 8 hours and compared with that of the single optical path. The relative standard deviation and maximum relative deviation were used as evaluation indices to assess the stability instrument. The counting attenuation rate decreased from -0.049 3%·h-1 of the single optical path to 0.001 0%. For 11 data points with large fluctuations, the relative standard deviation decreased from 0.151 4% to 0.032 6% of the single optical path, indicating that the self-calibrating formal EDXRF analysis technology of homologous excitation can effectively reduce the effects of counting attenuation and primary X-ray energy spectrum fluctuations. From the perspective of comprehensive effect, the relative standard deviation and maximum relative deviation of Mn, Co, and Ni are 0.076% and 0.170%, respectively, after the correction of synchronous data, which is twice as stable as that of the single optical path. The paper establishes a mathematical model for quantitative analysis based on dual optical path EDXRF analysis. Through experimental verification, the absolute errors of Mn (17.361%~20.016%), Co (12.991%~14.965%), Ni (29.653%~33.065%) in powder compacted samples are not more than -0.072%, -0.061%, 0.098%, respectively, and the analysis time of single sample is 200 s, indicating that the self-calibration formal EDXRF analysis technology with homologous excitation can effectively improve the instrument analysis accuracy, and achieve fast accurate testing requirements.
Key words：Ternary cathode materials; Energy dispersive X-ray fluorescence analysis; Energy spectrum stability correction; Quantitative analysis
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