Within the framework of the AIF-funded research project "FSWBatt" an alternative process for welding carrier foils made of copper and aluminum in battery production is investigated. The application of Friction Stir Welding (FSW) is expected to reduce the high costs due to the rejection of defective welds in cell production in the long-term. At the same time, the maximum number of weldable foils may be increased to improve the performance of the batteries.
Currently, the importance of alternative drive concepts is increasing. In particular, a change from vehicles with conventional combustion engines to electric vehicles has taken place in the last few years. Energy storage systems play a key role in this development. Due to their high energy density, lithium-ion batteries are the primary power source in electric vehicles. One major challenge for the manufacturing process is the qualification of a production system that meets the high quality requirements.
During cell assembly, stacked foils, each individually several micrometers thick, are welded together to ensure the internal contact of the cell. The weld needs to meet various quality requirements: low electrical resistance, minimal temperature input and sufficient strength. Currently used joining methods, like ultrasonic welding, have some limitations, for example, a lack of robustness.
The scope of the research project is to qualify FSW as a joining process for internal cell contacts. Concepts for a suitable application will be developed. Besides, a framework for selecting a suitable joining process for internal cell contacting will be provided.
In addition to process development this work includes a concept validation and an analysis of process potential. First, clamping and tooling concepts are developed and manufactured. These will be tested in statistically-planned welding experiments. The tests are used to identify a parameter window for friction stir welding of foil stacks. In order to evaluate the suitability of the FSW for internal contacting, an analysis of process potential based on a comparison with alternative joining methods (laser and ultrasonic welding) is planned.
Within the scope of the research project, basic findings for a process and tool design for contacting foils using FSW are obtained. The small and medium-sized enterprises (SMEs) from the plant engineering sector will thus be given the tools to develop suitable equipment for the internal cell contacting.
The IGF project 00.048 EWN of the German Welding Society e.V. is funded by the AiF within the framework of the program for the promotion of industrial joint research (IGF) and the Federal Ministry for Economic Affairs and Energy on the basis of a decision by the German Bundestag.