应用同源自校正EDXRF分析法测定三元正极材料中Mn、Co、Ni的含量

Determination of Mn,Co,Ni in Ternary Cathode Materials With Homologous Correction EDXRF Analysis

锂离子电池在新能源开发与应用中具有重要作用。三元正极材料成分配比对锂离子电池产品性能与质量产生很大影响,生产控制需要及时、精确地掌握混料的成分变化。能量色散型X射线荧光(EDXRF)技术在该领域的快速分析中具有较好的应用前景,但目前商品仪器的分析精度尚不能满足生产需求。为了解决三元正极材料成分Mn、Co、Ni的高精度EDXRF分析的技术难题,提出了一种基于同源激发的自校正式EDXRF分析技术,采用钨靶X射线管(25 kV/400μA)和两个能量分辨率均为135 eV(@5.9 keV)的电致冷SDD探测器组成双路X荧光同步激发-探测装置,将X射线管发射的原级X射线经双路准直器分束后,分别激发校准样品和待测样品,两个探测器同时测量两个样品的荧光计数,采用标准样品的能谱数据对待测样品的能谱数据进行“归一化”处理实现同步校正,从而降低分析仪器中X射线管不稳定性的影响。通过8小时内的140次重复性测试,从计数衰减率、计数波动和整体效果等方面分析了该装置的稳定性,并与单光路的稳定性进行比较,以相对标准偏差和最大相对偏差作为评价指标来评估该装置的稳定性。计数衰减率从单光路的-0.0493%·h^(-1)降低到0.0010%·h^(-1),对于11个波动较大的数据点,相对标准偏差从单光路的0.1514%降到0.0326%,表明同源激发的自校正式EDXRF分析技术可有效降低计数衰减、初级X射线能谱波动的影响。从综合效果来看,经同步数据校正后,Mn、Co、Ni的相对标准偏差和最大相对偏差分别为0.076%、0.170%,稳定性较单光路提高了1倍。建立了基于双光路EDXRF分析的定量分析数学模型,经实验检验,分析粉末压样品中Mn(17.361%~20.016%)、Co(12.991%~14.965%)、Ni(29.653%~33.065%)的绝对误差分别不超过-0.072%、-0.061%、0.098%,单样品的分析时间为200 s,表明采用同源激发的自校正式EDXRF分析技术能有效改善仪器分析精度,实现快速、准确的测量要求。

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/400μA)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-0.0493%·h^(-1) of the single optical path to 0.0010%.For 11 data points with large fluctuations,the relative standard deviation decreased from 0.1514%to 0.0326%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.