Production Processes

Coating processes play a crucial role in the manufacture of membrane electrode assemblies (MEAs) and metallic bipolar plates. High-precision application technologies ensure homogeneous material distribution and optimise the electrochemical performance of the fuel cell.

An important approach is the production of catalyst-coated membranes (CCM) using iCCM (indirect CCM) and dCCM (direct CCM). While in the iCCM process the catalyst is first applied to a carrier material and then transferred to the membrane, in the dCCM process it is applied directly to the membrane. Both methods require high-precision coating processes to ensure uniform catalyst distribution and minimise material loss.

In addition to CCM production, the coating of metallic bipolar plates also plays a central role. These coatings improve electrical conductivity, increase corrosion resistance and reduce contact resistance between components. The choice of coating process depends on the specific requirements of the application, with PVD (physical vapour deposition), ALD (atomic layer deposition) and electroplating being widely used.

Continuous optimisation of these processes is essential to further increase the performance and service life of fuel cell systems and to make their industrial production efficient.

The development and manufacture of tailor-made catalyst and functional layers for fuel cells requires precisely formulated dispersion production. Active materials, binders and solvents are mixed in a targeted manner to produce a homogeneous suspension with optimum properties for the coating process. The choice of components has a significant influence on the electrochemical activity, mechanical stability and durability of the layers.

A key aspect is the adaptation of the dispersion to the coating process. Different application techniques such as slot die, spray or squeegee coating require specific viscosities and particle size distributions to ensure uniform layer formation and optimum adhesion.

In addition, the integration of functional layers plays an important role. Reinforcement layers increase mechanical stability, while recombination layers contribute specifically to reducing gas transmission. The combination of different material layers enables targeted performance enhancement and adaptation to different operating conditions.

The close integration of material development, process technology and quality assurance enables the realisation of optimised coating systems that are suitable for industrial applications as well as for scaling up to mass production.

The manufacture of complex fuel cell components requires precise manufacturing technologies that guarantee high quality, dimensional accuracy and repeatability.

• Injection moulding technology for the production of compound bipolar plates is established and mature. It is used to manufacture bipolar plates from polymer-based composite materials (compound BPP). Conductive fillers are embedded in a thermoplastic matrix and injected into a mould under high pressure. The material composition is crucial for the electrical conductivity, mechanical stability and chemical resistance of the bipolar plates.
• However, simpler, faster and more cost-effective processes are needed for the upcoming mass production. That is why we are currently focusing on the further development of promising continuous processes in order to meet the high production requirements.
• Dispensing technology has become the standard for the fast and efficient application of seals to bipolar plates. This involves precisely dosing highly viscous materials to ensure reliable sealing and long-term stability of the fuel cell.

The assembly of membrane electrode assemblies (MEAs) in a multi-layer process is an essential step in the manufacture of fuel cells. This involves precisely layering several layers – including the membrane, electrode and catalyst layers – on top of each other to ensure high efficiency and stability. The multi-layer process achieves an even distribution of the active layers, which is crucial for the electrochemical reactions in the fuel cell.

This process requires high precision in alignment and layer thickness control to maximise the performance and durability of the fuel cells. The integration of the MEA into the stack must also be carried out under optimised conditions to ensure tightness and energy flow between the layers.

End plates are an indispensable component in the assembly of fuel cell stacks, as they are responsible for the mechanical stability and electrical connection between the cells. Various end plate concepts are used to ensure even pressure distribution, which is crucial for optimising the performance of the entire stack.

Clamping technologies that connect the end plates to the individual cells play a key role in preventing leaks and maintaining constant pressure. Special techniques are used to connect the cells efficiently and stably without impairing their function. Careful selection of the clamping technology is necessary to ensure the mechanical load and longevity of the fuel cell stack.

Quality assurance (QA) for components such as cathode current collectors (KS), catalytic layers (CCM) and membrane electrode assemblies (MEA) is crucial to guarantee the performance and reliability of fuel cells. QS procedures include both material testing and process controls to ensure consistent quality across all manufacturing phases.

For MEA and CCM, tests are carried out on mechanical properties, chemical resistance and conductivity, among other things. Precise testing methods are equally important to ensure the homogeneity of coatings and layer thicknesses. These measures ensure that all components function optimally under real operating conditions.

Quality assurance for bipolar plates (BPP) and seals plays a central role in the longevity and efficiency of fuel cells. Bipolar plates must be tested in particular with regard to their electrical conductivity and corrosion resistance. This is done by means of specified corrosion tests in which the plates are tested under realistic operating conditions for their resistance to electrochemical reactions.

The seals responsible for sealing the fuel cells must also undergo strict QA processes. The focus here is on resistance to various media and long-term stability. Regular tests ensure that the seals meet the necessary requirements for tightness and durability.

End-of-line testing (EOL testing) is a critical quality measure at the end of the production chain for fuel cell components. All manufactured components undergo a final test to ensure their functionality and performance before they are put into service. For fuel cell stacks, this includes, for example, checking the electrical properties, tightness and mechanical stability of the entire unit.

EOL testing makes it possible to identify and eliminate defective parts at an early stage, thereby optimising the overall quality of the end product and reducing the likelihood of failures during operation. This final test phase is therefore crucial to ensuring the quality and reliability of fuel cells throughout their entire life cycle.