Detecting oversized particles in battery materials

Battery cathode and anode materials are typically manufactured with a narrow particle size distribution. However, during the materials processing, fines, agglomerates, or contaminants may be as well. While fines might enhance packing density and often desirable, large agglomerates and contaminants pose serious risks - causing local hotspots that degrade performance, shorten battery life, and compromise safety. Detecting these oversized particles is of great interest, but at the same time challenging as well, due to their low abundance in the electrode materials.

Laser diffraction is the industry standard for measuring particle size in battery materials. However, traditional systems often miss the presence of few large particles as their scattering signal is masked by the bulk population.

To address this, we explored the enhanced capabilities of the Mastersizer 3000+, which integrates adaptive laser diffraction (Size Sure) and dynamic imaging (Hydro Insight) to improve detection sensitivity and enable imaging of individual particles.

Adaptive laser diffraction (Size Sure) on the Mastersizer 3000+ separates the overall diffraction signal into steady and transient states. While the steady state reflects the bulk material, transient events—caused by anomalous large particles—are independently recorded and analysed. This is made possible through the Size Sure technology, which captures 10,000 diffraction frames per second, offering unmatched temporal resolution.

Dynamic imaging (Hydro Insight) complements Size Sure by visually confirming the presence of large particles. The Hydro Insight accessory on Mastersizer 3000+ enables the capture of high-resolution images of individual particles for independent verification and classification (e.g. agglomerates vs. true contaminants).

Case Study: Contamination Detection in LNCA Cathode Material

In this case study, we tested pure Lithium Nickel Cobalt Aluminium Oxide (LNCA) cathode material and five samples spiked with increasing concentrations of 42.7 µm spherical glass particles, named LNCA +G1 to LNCA + G5. All specimens were analysed on Mastersizer 3000+ platform using:

• Dynamic Imaging (Hydro Insight)
• Classical Laser Diffraction, and 
• Adaptive Diffraction (Size Sure)

Samples were dispersed in water (with a small amount of IGEPAL CO-630 surfactant) using the Hydro MV dispersion unit.

1. Instrument Setup

The experimental setup (Figure 1) included:

• Mastersizer 3000+
• Hydro MV (automated dispersion unit with stirring, ultrasonication, and degassing) – minimizes bubbles that may interfere with large particles diffraction signal.
• Hydro Insight (Dynamic imaging with standard resolution lens for analysing 1–300 µm size range)

2. Results

2.1 Dynamic Imaging with Hydro Insight:

500,000 particles were imaged per sample in ~20 minutes each. In pure LNCA, the software identified three particle populations: fines, regular particles, and agglomerates (Figure 2), with a Dv50 of 6.7 µm (Figure 3). 

Spiked samples (LNCA+G1 to LNCA+G5) revealed the presence of between 2 to 100 distinct glass particles per 500,000 particles (image of first 2 samples is shown in Figure 4), equating to 4 to 200 Particles per Million (PPM) detection.     

2.2 Classical Diffraction:

Five replicate measurements of pure LNCA showed consistent results (Dv10 = 3.61 µm, Dv50 = 6.69 µm and Dv90 = 11.6 µm) as shown in Figure 5 and summarised in Table 1. These measurements also reveal the presence of fines at mean diameter of ~1µm, in addition to the regular particles with mode around 7 µm. 

In the spiked samples, glass particles were detectable only in LNCA+G4 and LNCA+G5, where concentrations exceeded ~100 PPM (Figure 6). Lower concentration samples showed no glass particle peak.

2.3 Adaptive Diffraction (Size Sure):

Size Sure maintained identical steady-state results to classical measurements but uniquely revealed transient signals from large particles even in low concentration samples. 

Steady and transient state data of 5 repeat measurements on pure LNCA sample is shown in Figure 7. The steady state data shows similar particle size distribution as in the classical measurement, including a small peak of fines.  The transient state data do not show any additional features in this sample.  Results of these measurements are summarized in Table 2.

In the spiked specimens, the steady state data showed glass particle peaks only in samples LNCA +G4 and LNCA +G5 (Figure 8), just like the classical laser diffraction data with sensitivity ~ 100 PPM. 

However, the transient state data showed glass particle peaks also in samples LNCA +G2 and LNCA +G3 (Figure 9), which had much lower glass particle concentrations, down to ~10 PPM.

Table 3 summarizes the results of all measurements in relation to detection sensitivity of contaminant glass particles. While Classical diffraction can detect 100 PPM and beyond, Size Sure adaptive diffraction could detect down to 10 PMM. Hydro Insight can in principle detect down to 1 PPM, albeit with longer measurement time.

3. Conclusion

The Mastersizer 3000+ with Size Sure and Hydro Insight features significantly enhance detection of low-abundance, oversized particles in battery materials:

• Classical Laser Diffraction: Detection limit ~100 PPM (~ 2-minute measurement)
• Size Sure: Detection limit ~10 PPM (~2-minute measurement)
• Hydro Insight Dynamic Imaging: Detection limit ~1 PPM, but longer measurement time (~40 minutes for 1 million particles)

This powerful combination enables advanced QA/QC with large particle detection, improving battery safety, yield, lifetime, and performance.