Pilot trials are the central intermediate step between laboratory and production scale for recognising scaling risks in battery material mixtures at an early stage. They supply data on mixing behaviour, dispersion quality, rheology, temperature development and process stability and thereby create the basis for a robust scale-up.

1. Transfer not only geometry, but examine process function

Geometric enlargement alone is not sufficient for a scale-up. More important is whether the mixing principle fulfils the same function at the larger scale, that is, whether agglomerates are reliably dissolved, solids distributed evenly and rheological target values achieved reproducibly.

Characteristic values such as the Reynolds number, Froude number, specific energy input and circumferential speed can be helpful, but they only make sense where they suit the respective mixing system. In many battery processes the local shear stress is more important than a purely formal similarity of the numerical values.

The Froude number relates to rotating free-fall, drum and throw mixers as well as to systems with a horizontally mounted mixing tool. In vertical mixers with forced restratification it is not a design or scale-up criterion. What is decisive there is that the mixing principle remains the same across all sizes and that the restratification covers the entire mixing chamber independently of the fill level; transferability is secured in the pilot plant with the original product.

2. Secure the process window with DoE

A pilot programme should be built up with a structured design of experiments. Critical parameters are typically solids content, order of dosing, mixing duration, rotational speed, temperature, vacuum or inerting and residence time.

The aim is not a single "optimal point", but a robust range in which viscosity, homogeneity, particle distribution and agglomerate content remain stable. Fluctuations in raw materials or plant operation can thereby be absorbed better later on.

3. Test rheology and dispersion realistically

With battery mixtures, the quality of the dispersion is often just as important as homogeneity alone. Pilot batches should therefore not be assessed merely visually or via simple mixing samples, but with rheometry, particle size analysis, microscopy and suitable process samples.

What is decisive is the correlation between slurry properties and later performance, such as coating quality, adhesion, drying behaviour and electrochemical cell performance. Without this connection, the scale-up remains analytically clean but uncertain in process engineering terms.

4. Recognise energy input and shear hotspots

Pilot trials help above all to avoid under- and over-dispersion. Too little energy leads to residual agglomerates; too much energy can cause a rise in temperature, structural changes or unnecessary wear.

It is therefore important to consider the energy input not only as a total value, but also its distribution within the mixing chamber. With highly viscous or sensitive slurries in particular, local shear hotspots can occur at large scale that were not visible in the laboratory.

5. Assess batch and continuous processes separately

If a change from batch to semi-continuous or continuous operation is planned later, this must be investigated separately at pilot scale. Residence time distribution, back-mixing, start-up and shut-down behaviour and the stability of steady-state operation are then decisive.

A successful laboratory batch says nothing about this. Only pilot data show whether the later production conditions permit the same consistency of quality.

6. Represent real conditions in the pilot

Battery materials react sensitively to moisture, oxygen, temperature and cleaning conditions. Pilot trials should therefore take place under conditions as close to industrial as possible, for example with controlled dew point, inerting or realistic material batches.

The measurement systems should also be designed at pilot stage so that they can be used later in production. Otherwise additional uncertainties arise during ramp-up through non-transferable data or inadequate process monitoring.

7. Secure data for series release

Pilot trials serve not only technical optimisation, but also the assurance of process capability, specification windows and start-up strategies. This includes robust mass data, repeat trials, balances and documented deviations.

The better the pilot phase is documented, the lower the risk of scrap, rework and long ramp-up times in series production.