Development of a method for direct elemental analysis of lithium ion battery degradation products by means of total reflection X-ray fluorescence

• Development of a TXRF method for analysis of energy storage materials
• Determination of transition metals without microwave digestion
• Assessment and comparison of the developed method with ICP-OES and ICP-MS
• Investigation on the NCM degradation mechanisms

A new method using the total reflection X-ray fluorescence (TXRF) technique for the elemental analysis of lithium ion battery (LIB) degradation products is presented. Here we investigate transition metals that have electro-deposited on a graphite electrode, which is the typical LIB anode. For this, the developed non-digestive method is validated against the common methods in elemental analysis of battery degradation, i.e., inductively coupled plasma-optical emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS). The results obtained with the TXRF method are compared with those of the standard method with respect to their recovery rate and detection limits.The TXRF is a well-known quantitative and qualitative analysis technique with very low detection limits and therefore suitable for the adaption in the field of battery aging products.By avoiding the time consuming dissolution of the solid battery components — performed via microwave assisted acid digestion — recovery rates of 90 to 110% could be observed, thus showing the great applicability of the alternative TXRF method. Furthermore, it could be shown that elevating the C-discharge rates of the cathode material as well as elevating the charging cut-off voltages increases the transition metal deposition on the graphite anode and even at low contents of transition metals, the TXRF delivers excellent results.