Mixing of battery slurry A proven concept for a complex process

The mixing of battery slurry is one of the first steps in the complex production of lithum-ion based batteries. The plants and technologies of Zeppeling Systems ensure highest safety in handling hazardous materials, and they deliver outstanding product quality and productivity in this crucial process.

Battery production:

Who will build the „gigafactories“ that are needed to fulfil the battery demand of electromobility? In Europa alone, about 20 of these factories – each of them a billion-Euro-investment – will be producing the batteries for electric cars in 2025, according to forecasts (Ann.). At that point, batteries for eight million electric vehicles per year will be manufactured in Europe alone. And there are more battery factories to come, including pilot plants and smaller factories for new battery technologies and, of course gigafactories in Asia and America.

The question has been risen whether the machine manufacturers are well prepared and able to fulfil this demand. For the first step of battery cell production, the mixing of slurry for the coating of anode and cathode material, this question can clearly be answered with a “Yes”. The obvious obstacles and hazards of this process can definitely be mastered.

Handling of hazardous, highly viscous and shear-sensitive materials

The first challenge in this process is the handling of hazardous material. Especially some of the materials for the cathode side are toxic and small enough to pass the alveoli and enter the blood circulation. Another part of the mixture – the binder material – is highly viscous which makes conveying and weighing difficult. Furthermore, there is a third fraction – the CMC – which is shear-sensitive. So, the systems for conveying and storing these materials as well as for mixing them have to be engineered with utmost care and a deep understanding of the materials and processed involved.

This where Zeppelin Systems comes into play. The company has a proven track as an expert in handling bulk materials and offers plant engineering solutions for storing, conveying and mixing the (powderous or viscous) ingredients for slurries – from food industry and chemical production to performance materials.

As a pioneer in battery slurry production, the Zeppelin Systems engineers have already gathered comprehensive experience in this first and important process of battery production (Lithium-Nickel-Cobalt-Aluminium/ NCA and Lithium-Nickel-Mangan-Cobalt/ NMC) . The following passages describe a typical slurry production unit.

Handling and intermediate storage of ingredients

The slurry production units start with the handling of the ingredients, mostly, of powderours consistency and delivered in bags or big bags. Depending on the hazardousness of the materials, Zeppelin Systems inserts glove boxes or automatic filling stations in its plants. They prevent dust from entering the production environment and ensure that neither people nor the environment are affected by toxic dust particles. All ingredients – also the wet and viscous ones, i.e. the binder material – are stored intermediately in tanks.

Conveying, dosing and mixing

Pneumatic conveying systems are used for transporting the powderous ingredients into the dosing or weighing units. A careful transport is of highest necessity to keep up the properties of the products. Otherwise, the quality of the battery cells could be affected. This is why, in this application, Zeppelin Systems optionally makes use of the unique Intraflow system which successfully avoids clogging within the pneumatic conveyors. Two special bypass systems (Overflow and Airfloat) allow the use of product-saving dense phase conveying also for powders. The bypass systems, in which secondary air is selectively introduced into the conveying line via valves at precisely defined intervals, enable trouble-free dense phase conveying, which is used in particular for pearl carbon black or silica due to the low particle size destruction.

The viscous and wet materials are conveyed by pumps. Integrated weighing systems supply the quantitites of the materials according to the recipe. The mixing itself has to ensure a very precise homogenization – a quality that the mixers of Zeppelin Systems are well-known for. Furthermore, the smaller particles of the active material (graphite) completely enclose the carrier substances within the battery cell. The engineers of Zeppelin Systems select the mixing equipment according to the individual requirements – from the own portfolio or in co-operation with other established manufacturers of mixing machines.

Due to the complex processes of dosing and mixing, the current plants are producing the battery slurry batch-wise. There are, though, first continuous production plants which might gain a bigger footprint in high-scale production.

Conclusion: A new yet proven process

Battery slurry production of lithium-ion based batteriy cells is a comparatively new process, and the operators of the gigafactories have to face challenges including the handling and mixing of hazardous, viscous and shearing-sensitive materials. But Zeppelin Systems offers proven concepts and established technologies for this task. The company´s project engineers are also prepared to adapt the existing concept of battery slurry production (for pilot plants and mass production in the gigafactories) to new materials and battery cell systems like Lithium-Ferrum-Phosphate, Lithium-Sulphur oder Lithium-Air.

Annotation

“Strategic Transformation: From Giga-Factory to Giga-Business.” Porsche Con-sulting Magazine, June 2021,

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