Fraunhofer Institute for Laser Technology ILT
Fraunhofer Institute for Laser Technology ILT

Hydrogen technology

© Fraunhofer ILT, Aachen.

Green hydrogen is the energy source of the future. Potential areas of application include mobility and the supply of domestic energy based on fuel cells. In addition to technological advancements, broad market penetration will primarily require a significant reduction in costs along the value chains of electrolyzers, fuel cells and their components. Highly productive laser processes play a decisive role in scaling manufacturing processes to reach such reductions.

Laser welding of bipolar plates

One of the core elements of a fuel cell is the bipolar plate, which, as a metallic variant, usually consists of two thin-walled stainless steel or nickel sheets. These are joined in a hydrogen-tight and reproducible manner by laser welding. Process errors can be avoided and the thermal distortion of the plates can be kept to a minimum by developing modular clamping devices and adapting the welding geometries in terms of arrangement and sequence.

By adapting the wavelengths and beam modulations, Fraunhofer ILT has achieved feed rates of more than 1 m/s. In combination with inline process control, laser beam welding is an efficient and safe manufacturing process for producing metallic bipolar plates quickly.

© Fraunhofer ILT, Aachen.

Coating, repair and additive manufacturing

Laser cladding can apply metal tracks between 0.01 and 2 mm thick with high precision to almost any metallic base material in a very short time. By superimposing several weld beads, flat coatings can be produced for manufacturing bipolar plates or functional layers on electrolyzers.

If several layers are welded on top of each other, the process can also be used flexibly for repair and additive manufacturing.

Reducing contact resistances

The contact resistance between the bipolar plate and the gas transport layer is one of the main reasons PEM (proton-exchange membrane) fuel cells suffer from efficiency losses. Especially with graphite-filled thermoplastic compound materials, an insulating plastic film forms on the surface, which prevents the electrical connection to the gas transport layer.

Lasers remove this film and expose the conductive graphite filler material in the contact area with the gas transport layer. Unlike mechanical grinding processes, ultrashort pulsed laser radiation can selectively remove the plastic without damaging the filling material. The contact resistance of metallic bipolar plates can also be reduced by selectively introducing microstructures.

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© Fraunhofer ILT, Aachen

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