Standardless FP XRF Analysis for Lithium Ion Battery Electrode Materials

Standardless FP XRF calculates elemental concentrations using theoretical physical models rather than calibration curves created from reference standards. The calculations account for matrix effects, fluorescence yields, absorption, enhancement effects, and instrument geometry. This eliminates the need to prepare composition-specific standards for every new material, making the method especially useful for research, development, and failure analysis where sample compositions vary frequently.

For major transition metal components in Ni-rich and NCM cathode materials, standardless FP XRF can achieve agreement with ICP measurements within approximately 5% relative error. Validation studies also indicate that many major elements present above 0.1 mass% can be quantified with relative errors around 10%, while light elements and lower-concentration species generally have somewhat larger uncertainties.

Yes. The technique can identify and quantify numerous impurity elements, including sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, potassium, calcium, iron, strontium, zirconium, and tungsten. Concentrations ranging from roughly 10 ppm up to 0.1 mass% can be measured, although the lowest concentrations should generally be considered semi-quantitative because analytical uncertainty increases as concentration decreases.

WDXRF provides higher spectral resolution than energy-dispersive XRF, allowing overlapping emission lines to be separated more effectively. This is particularly valuable for nickel-manganese-cobalt cathodes, where manganese Kβ emissions overlap with iron Kα emissions. Improved peak separation enables reliable detection of trace iron contamination that may otherwise be difficult to measure.

Although lithium itself cannot be measured by conventional XRF, WDXRF can analyze other light elements such as carbon and oxygen. By including these elements in the FP calculation, the technique can estimate the silicon-to-oxygen ratio in silicon oxide materials and determine the amount of carbon coating applied to anode particles, providing important information about material composition and processing.

Accuracy depends on how well the theoretical sample model represents the actual specimen. Important factors include whether the sample is treated as a bulk material or thin film, the presence of organic binders or polymers, sample homogeneity, particle size effects, and accurate modeling of non-measured components. Using a small number of known reference samples to refine instrument sensitivity can further improve quantitative performance.

The technique provides rapid, non-destructive elemental analysis without requiring extensive calibration development. It can simultaneously quantify major elements, evaluate stoichiometry, estimate carbon coatings, and detect trace contaminants within a single measurement. This combination of speed, flexibility, and broad elemental coverage makes it well suited for material development, process optimization, impurity screening, and quality assessment of both cathode and anode materials.