Battery manufacturing: Reliable, adaptable particle sizing using the Mastersizer 3000+

Introduction

Ensuring that the particles used in battery materials are correctly sized is essential for problem-free manufacturing and optimized battery performance. Building on the success of our Mastersizer 3000 laser diffraction instrument, we introduce here the new Mastersizer 3000+ and describe how, with its added features, it’s sure to be the instrument you rely on in your battery research and production operations, time after time.

Particle sizing using laser diffraction

Whatever materials you employ in your batteries, particle size must be tightly controlled to avoid processing problems during manufacturing and ensure that battery performance meets the desired standard.

There are a variety of methods of determining particle sizes, but laser diffraction is widely regarded as the ‘gold standard’ technique because of its speed, accuracy and repeatability. Since its launch in 2012, the Mastersizer series of laser diffraction instruments have gained a well-deserved reputation in battery research and manufacturing as the best-performing and most reliable instruments on the market.

The Mastersizer 3000+ now builds on this success and our decades of technical knowledge and experience, with three new software features to enhance your particle-sizing capabilities still further:

• Size Sure for improved confidence in routine measurements and method development
• Data Quality Guidance for helping you to make independent decisions on real-world samples
• SOP Architect for standardized, streamlined method development for wet samples

When you add to these features the flexibility and ease of use of the Mastersizer 3000+, and other platforms like Smart Manager for optimizing uptime and usage, what do you get? A system that truly becomes the top choice for particle sizing in your battery research and production – and we’ll demonstrate this below by explaining how Mastersizer 3000+ can help you tackle everyday challenges in battery material analysis.

Ensuring high instrument-to-instrument consistency during method transfer

Many battery manufacturers use multiple laser diffraction instruments at different points in their workflow – and you need to be sure that methods run on one instrument can be reliably transferred to another instrument.

In another scenario, laser diffraction is used to monitor the size evolution of precursor particles as they nucleate, grow and agglomerate, which demands an instrument that gives confidence in results over a period of time.

In both situations, you can rely on the Mastersizer 3000+, with its unsurpassed reproducibility and repeatability eliminating worries over instrument-to-instrument variability or measurement drift over time. And with the new Data Quality Guidance tool on-hand, any discrepancies arising as measurements are performed are immediately flagged up, enabling you to take remedial action more quickly and avoid making important decisions off the back of imperfect data.

Mastersizer 3000+ meets the highest standards in that regard, with its instrument-to-instrument reproducibility typically being better than 1% for polydisperse samples, which exceeds ISO 13320:2020 recommendations. 

Malvern Panalytical has developed a Quality Audit Standard (QAS), which is a polydisperse standard of glass beads, to meet all the requirements of ISO 13320 for a certified reference material. Glass beads are an appropriate reference material for laser diffraction as they are spherical particles with well-known optical properties. When this material was tested on 50 different Mastersizer 3000+ systems with a Hydro MV dispersion accessory, the %RSD for the Dv50 was calculated to be 0.4% (Figure 1). 

Figure 1: Reproducibility scatter plot of 50 QAS measurements on the Mastersizer 3000+

Excellent method repeatability for anode and cathode battery materials is also achieved. Measurements of a cathode material (carbon-coated LiFePO₄, Figure 2 left) and an anode material (graphite, Figure 2 right) gave %RSD values for Dv10, Dv50, and Dv90 of less than 1%, which again exceed the ISO 13320:2020 recommendations. 

Figure 2 left: PSDs obtained for a sample of carbon-coated LiFePO4 tested with a Mastersizer 3000+ Ultra instrument, showing very good instrument repeatability (n=5, Dv10: 0.5% RSD; Dv50: 0.7% RSD; Dv90: 0.3% RSD). Right: PSDs obtained for a sample of graphite tested with a Mastersizer 3000+ Ultra instrument, showing very good instrument repeatability (n=5, Dv10: 0.3% RSD; Dv50: 0.2% RSD; Dv90: 0.5% RSD).

Detecting large size agglomerates in electrode slurries

The presence of oversize particles in cathode slurries raises the risk of short-circuiting the anode and cathode, and so must be avoided. Mastersizer 3000+ is an excellent choice for identifying coarse particles and aggregates, with an upper measurement limit of 3500 μm.

This capability is now extended, thanks to Size Sure – a feature that separates the steady-state and transient-state data. Rather than filtering or discarding data, Size Sure instead generates two particle size distributions (PSDs), allowing you to clearly distinguish between the parts of the size distribution profile due to transients (such as unexpected contaminants), from the steady state (i.e. your sample).

Therefore, when a quality issue arises – as illustrated in Figure 3 – running a sample on the Mastersizer 3000+ with Size Sure gives a clear insight into your sample, and so reduces the amount of time you spend troubleshooting.

Figure 3: Using Size Sure to detect the presence of agglomerates present in sample of LiFePO4. The transient-state data (dotted line) shows the presence of agglomerates at sizes >100 µm, which are not obvious from the classic result. The segments of scattering data which do reflect the presence of these agglomerates are few in number relative to the segments that do not. As such, the averaging process used to generate the classic result means these agglomerates are not obvious in the resulting classic PSD. However, this is not the case when Size Sure is applied; the segments which reflect the presence of agglomerates are much more common within the transient state.

Reliably identifying oversize particles

Prior to coating onto the current collector, slurries may contain a variety of materials with a very wide range of particle sizes including some undesired ghost (impurity) particles and agglomerates. Checking particle size distributions in slurry is important to ensure that you’re going to get the optimum coat quality in the dried slurry. However, can you rely on your laser diffraction instrument to handle such complex mixtures?

The answer with Mastersizer 3000+ is emphatically yes, thanks to its wide measurement range (10 nm to 3500 μm), and its ability to handle complex multi-modal distributions. In addition, we offer the Hydro and Aero accessories for accurate and reliable preparation of wet and dry dispersions respectively.  In the example shown in Figure 4 an agglomerated LiFePO₄ sample spiked with ghost particles (a small fraction of glass beads) was measured with Mastersizer 3000+ system and analyzed in classical and Size Sure modes. In the classical mode, there are two peaks representing large size particles at 40 µm and 1500 µm. It is difficult to tell whether these represent agglomeration or ghost particles. The Size Sure mode, on the other hand, clearly resolves the transient coming from ghost particles (1500 µm) and the sample with stable 40 µm size agglomerates. 

Figure 4: PSDs of a sample of agglomerated LiFePO4 spiked with a small fraction of glass beads (simulated multi-modal system with ghost impurity particles) measured on a Mastersizer 3000+ system. The Size Sure mode clearly resolved the transient peak (dotted line) at ~1500 µm belonging to the ghost particles from the bulk of the sample. The peak at 40 µm represents the agglomeration of the sample particles.

Adapting quickly to new battery materials

Investigating new materials – for example, anodes containing a proportion of silicon to boost energy density is an integral part of the operations of many battery manufacturers. And when competitors are snapping at your heels, you need to be able to move quickly to develop new sizing procedures for modified materials and particle types. 

In this situation, Mastersizer 3000+ is what you need. Our Hydro wet dispersion accessories handle an extended range of sample volumes and a wide variety of dispersants, while our Aero dry dispersion accessory ensures rapid, reproducible powder dispersions, even for more fragile materials. And of course, switching between any of them is quick, easy, and convenient.

Figure 5 is an example of a pure graphite, and a mixed graphite + silicon anode material, measured with Mastersizer 3000+. Shoulder peaks on the left of PSD coming from silicon are clearly visible.

Figure 5: PSD obtained using Mastersizer 3000+ for a pure graphite (top left), pure silicon (top right), and a 90:10 graphite–silicon mix (bottom) typical of that used in battery anodes.

Simplifying the learning curve for staff

As laser diffraction becomes more widely used in the manufacturing sector, it’s increasingly the case that those using the equipment have to deal with a variety of instruments. However, an approach that works on an instrument from one manufacturer may not work on another, running the risk of unsuitable settings being used.

In addition, we all know how samples can throw up unexpected problems from time to time – but if you’re new to the technique, you may not always have an experienced colleague on-call when you need them.

And finally, the particle sizing results are only as useful as the reports used to present them. So, when important decisions need to be made quickly, you want to be able to provide your data in a clear format that focuses on the key points.

All of these challenges are resolved with the Mastersizer 3000+ using the intuitive Data Quality Guidance and innovative SOP architecture. The SOP Architect (Figure 6) makes it easy to generate standard operating procedures even if you’re not familiar with preparing them, while the Data Quality Guidance feature offers expert-curated advice about suspect measurements. Finally, the flexible reporting capabilities mean that you can generate tailored reports in exactly the format required by your organization.

Figure 6: Example screenshot of SOP Architect during measurement acquisition, showing the various pieces of information about the sample being generated.

Conclusion

The highly competitive and ever-changing world of batteries means that manufacturers need to stay at the top of their game – and that affects every aspect of R&D and production, including the performance-critical aspect of particle sizing.

And with emerging materials such as silicon/graphite anodes and dry-coating powders now being investigated, there’ll continue to be pressure to get the most out of laser diffraction systems. Thousands of companies and research institutes across the world already rely on Mastersizer for their laser diffraction measurements – and with the added benefits of the Mastersizer 3000+, making your next instrument decision just became even easier. 

Advanced features like SOP Architect, Data Quality Guidance and Size Sure allows anyone to create perfect methods and analyze samples quickly and with confidence. And when the time comes to transfer those methods to production, the instrument-to-instrument reproducibility of Mastersizer 3000+ means that you won’t have to deal with discrepancies in size distributions, as might happen if you’re using instruments from a different manufacturer for the QC stage.