How XRF calibration helps improve NMC battery production

von Umesh Tiwari, Friday, 26th July 2024

With their high energy density, nickel-manganese-cobalt (NMC) batteries are widely used in electric vehicles and mobile devices that require power for extended periods of time. However, the the process of precursor synthesis can lead to variability in the chemical composition of these batteries. So how can battery manufacturers achieve accurate elemental composition of these materials to ensure consistency in quality control?

What are NMC batteries?

NMC batteries are one of the most common types of lithium-ion (Li-ion) batteries, where the cathode is composed of a mixture of nickel, manganese, cobalt, and Lithium. Nickel extends the range of electric vehicles (EVs), while Mn contributes to the thermal stability of NMC batteries, reducing the risk of overheating during charging and discharging; and cobalt suppresses structure defects by reducing Li/Ni disorder in Ni-rich compositions and helps achieving a well-crystallized layered structure.

NMC batteries are so common that when people talk about lithium-ion batteries, they usually mean batteries with the NMC cathodes. They boast high energy density, improved stability, and established industrial-scale production. But that doesn’t mean NMC battery makers can rest on their laurels: A precise control over their production process is necessary to minimize the waste and control the production costs.

What are the challenges in NMC battery production?

Despite having the advantage of higher energy density, high Nickel NMC batteries have yet to compete with lithium iron phosphate (LFP) batteries, which have a higher discharge rate than NMC batteries. LFP batteries can go through tens of thousands of cycles without degradation, whereas NMC batteries typically start to fail after a few thousand cycles. Lithium-iron phosphate batteries are also less prone to thermal runaway. Most disadvantageous for the NMC batteries is, however, their higher production costs and the volatility in the prices of Nickel and Cobalt.

How can NMC battery production be improved?

One way to reduce the production cost to compete with LFP chemistry is to optimize the production process using fast and reliable analytical methods. This is where an accurate elemental composition analysis allows them to control the amount of material used with absolute precision, maximizing efficiency while ensuring the best possible performance.

X-ray fluorescence (XRF) spectrometry and inductively coupled plasma (ICP) spectroscopy are the two most commonly used analytical techniques for elemental composition analysis. Compared with ICP spectroscopy, XRF spectrometers allow for simpler and faster analysis while providing highly precise and accurate results. This makes XRF a practical solution for process and quality control in battery cathode and precursor production and battery recycling.

How does XRF work?

When X-rays strike atoms, the atoms reflect fluorescent ‘fingerprints’, whose number and strength vary according to their number of electrons. By measuring the number and strength of these fingerprints, an XRF instrument can quickly and reliably determine not only which elements are present in a sample, but in what proportions, from ppm to 100% levels, without any need for dilution.

XRF can analyze elemental composition in two ways. The first is the standardless screening of input materials, which detects and semiquantitatively estimates elemental composition. However, this doesn’t provide the accuracy needed for cathode material production and quality control. As a result the second method must be used, which involves calibration using certified reference materials (CRMs).

How are XRF instruments calibrated?

To calibrate an XRF, one needs a set of reference standards whose chemical composition is similar to that of actual material, and which cover a range of elemental composition for all the elements of interest. However, there has been a clear lack of commercially available calibration standards for battery cathode materials.

Malvern Panalytical has therefore developed and produced a set of NMC CRMs for XRF calibration. When used in conjunction with our sample preparation systems and expertise, these CRMs can provide highly accurate and reliable results for NMC cathode materials. The NMC CRM package includes 12 synthetic reference standards specifically designed for preparing XRF fused bead samples, as well as a fusion recipe and an XRF application method template.

Analyzing NMC batteries and beyond

Equipped with the Malvern Panalytical NMC CRM package, Eagon 2^® fusion machine, and Zetium XRF spectrometer, manufacturers can obtain highly accurate and precise elemental analysis results for their NCM batteries. The package is also suitable for other cathode chemistries such as lithium nickel cobalt aluminum oxide, lithium cobalt oxide, lithium manganese oxide, their precursors, and recycles black mass analysis.

This turnkey solution enables high-throughput and seamless elemental analysis. As such, it eliminates the need for extensive sample preparation, specialized analytical skills, and the use of strong acid chemicals typically required for ICP analysis. By working with stakeholders such as battery researchers, manufacturers, and standards committees, we ensure that our users can get the most out of their analysis for years to come.

Want to see what XRF calibration looks like in practice? Read the application note to learn more!

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