What distinguishes our composite bipolar plates from existing bipolar plate technologies?

Anna Grevé: Our composite bipolar plates have a number of unique features. First of all, they offer a significantly thinner plate geometry than conventional composite plates. For fuel cell applications, we are targeting a material thickness of 300 µm per half-shell – referring to the unstructured base material. This is made possible by a foil-based approach that allows forming similar to that of metal plates – for example, by roll embossing. Conventional processes such as injection molding or milling often reach their limits here.

Michael Joemann: Another advantage is the manufacturing process. It allows us to achieve very high fill levels, which has a positive effect on the conductivity of the plates. Even high contents of fine fractions such as carbon black can be processed, as the calendering process handles the resulting viscosity better than, for example, injection molding or plate extrusion.

The process also ensures that the thermoplastic properties of the binder polymer are retained. This enables continuous production by calendering and allows us to manufacture large-area bipolar plates economically and reproducibly.

Furthermore, these materials also open up possibilities for repairability, weldability and potential recyclability. Among other things, this means new degrees of freedom in the design, integration and scaling of fuel cells thanks to a seal-free and fully weldable stack design.

 

In which industries do you see the greatest potential for the use of composite bipolar plates?

Michael Joemann: We see the greatest potential for the use of our composite bipolar plates in the hydrogen economy. In particular, in the field of mobile fuel cell systems in commercial vehicles, maritime applications or trains. Where chemical resistance, durability and weight play a role, metal plates reach their limits due to corrosion or complex coatings. We also score highly with low material costs, durability and adaptability in stationary systems for emergency power or backup power solutions.

Anna Grevé: We also see growing application potential in electrochemical compressors or CO₂ conversion processes – both systems with high requirements for chemical stability and material design. Another trend we are observing is the transition to larger cell areas in stack designs – especially in the heavy-duty sector, where products, devices or applications are designed for particularly demanding or stressful conditions.

 

What challenges need to be considered when developing bipolar plates for fuel cells?

Michael Joemann: When developing bipolar plates – especially in the field of fuel cells – a multitude of technical requirements come together, some of which influence or contradict each other. A bipolar plate must be electrically conductive, gas-tight, mechanically stable and corrosion-resistant at the same time – and this over many thousands of operating hours, under changing temperatures, humidity conditions and media.

In the case of composite materials, these properties do not come from a single material, but must be achieved through the targeted combination of conductive fillers, polymer binders and suitable process parameters. Finding the optimal compromise between electrical conductivity, gas tightness, mechanical stability and processability is one of the central development tasks.

In our projects, we have learned that material development and cell and stack development must be closely interlinked and optimized together in order to exploit the full potential of the material. The US Department of Energy has defined ambitious criteria for bipolar plates, which are often regarded as the benchmark in the industry. The requirements are technically demanding, so we are all the more pleased that we are now able to meet all the target values. It has been an intensive journey over several years, with many development steps. Looking back, we are very proud of what we have achieved over the past five years.

Anna Grevé: Another critical aspect is series production. From raw material availability and reproducible shaping – e.g., using calender, press or injection molding processes – to integration into existing stack designs, all manufacturing steps must be process-reliable, cost-efficient and scalable. The development of bipolar plates is therefore a classic system task: Materials, geometry and manufacturing must be considered in close interaction and tailored to the respective application.

 

How can Fraunhofer UMSICHT help to master these challenges?

Anna Grevé: We take a systemic approach to the development of bipolar plates. This means that we combine materials science expertise with process development and a clear focus on the requirements of industry. This starts with the selection of suitable raw materials, continues with the formulation and processing of the composite materials, and ends with their integration into real cell and stack environments.

A key contribution is that we can analyze and optimize the interaction between material, structure, surface and process in a holistic manner. For our industry partners, this means that they do not receive a laboratory solution, but rather application-oriented, scalable technology tailored to their specific requirements.

Michael Joemann: Perhaps a few examples to illustrate our portfolio more concretely: In materials development, we focus on selecting and formulating suitable polymer-filler combinations that are adapted to the electrical, thermal and mechanical requirements for fuel cells. In the field of surface and interface design, we develop processes for the targeted adjustment of contact resistance, hydrophilicity or hydrophobicity, and adhesion – for example, through laser processes (in cooperation with Fraunhofer ILT) or functional additives.

In addition, we are involved in process engineering: We are establishing continuous manufacturing steps such as calendering technology (foil production, roll embossing and laser ablation) to ensure the cost-effective production of thin bipolar plates.

Finally, we support our partners through all stages of technology development with validation and testing. This starts with plate testing, which covers aspects such as conductivity, gas tightness and mechanical stability.

Anna Grevé: In summary, we see ourselves as a development partner with a strong focus on materials, processes and plate concepts. We bring new solutions to the industrial discussion and translate research results into technology-based approaches.

 

What role does sustainability play in the production of our bipolar plates?

Michael Joemann: Sustainability plays a central role for us – both now and with regard to the future direction of our developments. On the one hand, our materials have the potential to be recycled. In addition, systematic life cycle assessments (LCA) are already an integral part of our ongoing projects “HyCoFC – Long-term stable fuel cell technology through innovative hybrid compound bipolar plates” and “BiFoilStack – Development of stack designs for NT-PEM fuel cells with novel compound bipolar foils.” We use these to evaluate the ecological footprint of our bipolar plates. Initial results show, for example, that our solution has up to 68 percent lower global warming potential (GWP) than metallic bipolar plates – with comparable functionality.

 

How do we ensure that our solutions meet industry requirements and are marketable?

Anna Grevé: Our aim is to develop technologies that not only work in the laboratory, but are also close to series production, process-reliable, and economically attractive. To achieve this, we closely follow the requirements of industry in all phases of development – both technically and economically.

A central component is our continuously designed process line for the production of composite bipolar plates: From the formulation of the raw materials to the calendering process and the precise roller embossing of flow structures, we develop and test our solutions under realistic conditions.

In addition, we are in close contact with industry partners in the fields of stack development, system integration, and plant engineering. This dialogue is essential for identifying requirements at an early stage, incorporating feedback directly into development, and ensuring technological compatibility.

 

What opportunities are there for collaborating with Fraunhofer UMSICHT?

Michael Joemann: Collaboration with Fraunhofer UMSICHT can be structured in various ways to optimally meet specific requirements. One option is for customers to commission us directly to develop solutions for bipolar plate issues. In an initial meeting, we clarify the framework conditions and work out how we can successfully support the company with our expertise and infrastructure. We then prepare a quote and move on to iterative material development, including characterization.

Another option is collaboration within joint projects. Here, we can work on solutions together with several partners – often with public funding. We draw on an extensive network from industry, research and society, as well as on the resources of the Fraunhofer Institutes. We are experienced in selecting suitable funding programs and applying for projects, and we bring innovative ideas to the table. The subsequent transfer to the market is then carried out together with our partners.

Anna Grevé: We also offer licensing options. Licenses for our intellectual property rights can be granted in various ways and are tailored to individual needs. We discuss the appropriate steps in personal meetings and agree on the framework conditions for the respective business model and company.

 

How did the research into bipolar plates begin at Fraunhofer UMSICHT?

Anna Grevé: Our work in the field of bipolar plates originally began in the context of stationary energy storage systems – specifically vanadium redox flow batteries. The aim was to develop a bipolar foil that would allow a seal-free and fully weldable stack design. The decisive impetus came during a visit to our plastics technology center in Willich, where we noticed that the calender line there could be promising for continuous plate production. This led to the development of a novel manufacturing process, which we were able to patent and which was further developed for continuous production in the KontiFlex project together with an industrial partner.

The technology for redox flow applications was later licensed to the spin-off Volterion. At the same time, we began further developing the underlying material and process technology at the institute to meet the requirements of fuel cells. Since around 2020, we have been working specifically on this transfer, focusing on mobile applications that place particularly high demands on service life and power density.

 

Were there any other important milestones? And what direction will you be taking in the future?

Michael Joemann: At the project level, the joint project BiFoilStack, funded by the German Federal Ministry for Economic Affairs and Climate Action, is particularly significant: It shows how our technology also has great potential in the mobile fuel cell sector – especially where weight, volume and durability are decisive criteria. HyCoFC is also making a significant contribution to gaining new insights – for example, into process integration and the handling of different substrate materials. The project focuses on developing a cost-effective and scalable manufacturing method for hybrid compound bipolar plates (Hy-Co-BPP) and a customized fuel cell stack concept. The main goal is to increase the performance and long-term stability of fuel cells. The Hy-Co-BPP consists of a metallic carrier foil (material thickness approx. 100 µm) and a conductive compound foil (material thickness approx. 150 µm), with the compound foil serving as a corrosion-resistant coating and the metallic carrier foil providing mechanical stability.

In the coming months, we would like to focus in particular on further developing roll embossing and working on improving the mechanical properties. In the PolyFoleR project, we have identified promising approaches to fiber reinforcement and radiation-induced cross-linking, which we now intend to pursue further. From spring 2026, we will have a new high-temperature rolling mill at our disposal, which we can use to test how technical polymers such as PPS can be processed using the powder-to-roll process.

Anna Grevé: In the future, we want to further industrialize these developments and tailor them specifically to applications where the advantages of composite solutions are particularly evident – e.g., in fuel cell systems for commercial vehicles or maritime applications. We are also looking into their use in electrolysis stacks. This is because carbon-based bipolar plates are a more cost-efficient and scalable alternative to bipolar plates made of titanium.

We also see potential for added value through integration into existing plastics processing chains – for example, in combination with thermoforming or welding processes. The link with other UMSICHT competencies – for example in the areas of digitalization, sustainable materials or CO₂ reduction – will also play a greater role in the future. Our goal is clear: technologies with industrial connectivity that prove themselves in real-world applications and make a measurable contribution to the transformation of energy systems.