In the project, which was financed within the framework of BMBF’s KMU-NetC funding initiative, it was possible to demonstrate the basics of a new innovative hot pressing process using a tool made of ultra-high-performance concrete (UHPC) for the production of graphite bipolar plates for HT-PEM fuel cells, as well as its suitability. The application suitability of a pressing tool made of UHPC was tested and after iterative optimisation of the UHPC mixture the target values such as compressive strength of 200 MPa, high temperature resistance up to 330°C, low shrinkage and a self-compacting consistency could be achieved! The temperature control of the UHPC mould for the production of graphite bipolar plates was achieved by induction.
The process control (time, power) and the inductive heatability of different graphite PPS compounds was investigated at the ZBT and an optimal compound formulation was determined in close cooperation with the project partner Eisenhuth. The design and simulation of the induction coil geometry was carried out at the project partner IKFF at the University of Stuttgart. After setting up an isostatic press suitable for the application at the project partner Boyke, various test series were carried out with two-part pure concrete tools and three-part superstructures with an additional steel insert. The three-part press tool turned out to be more suitable due to the adjustable and achieved process parameters. With the selected tool design, the production of hot-pressed bipolar plates could be realised within a few minutes.
The characteristic material parameters tested at the ZBT, such as permeability to hydrogen, electrical conductivity and mechanical parameters of the bipolar plates, correspond to the specifications of the Department of Energy and are comparable with references established on the market. Thus, the basic usability of the technology for the production of semi-finished products and in future also structured bipolar plates for PEM fuel cells, also in the technically more demanding high-temperature PEM variant, or also redox flow batteries, was proven.
The technology offers a considerable reduction in cycle time compared to conventional hot pressing processes of these bipolar plates. The results of the project project offer great potential for a considerable reduction in the costs of fuel cells and electrochemical converters as well as the energy consumption required to manufacture the BPP. Boyke Press Technology GmbH