Cell Connection Technologies for Battery Modules

Battery storage systems for solar and wind power, as well as for mobile applications, consist of individual battery cells. The way in which individual cells are connected to form battery modules plays a decisive role in determining the reliability and efficiency of a battery storage system. At Fraunhofer ISE, we develop and analyze suitable topologies, technologies, and processes to connect battery cells electrically and mechanically via cell contacting systems. To this end, we use industrial and flexible systems for resistance and laser welding processes.

Practical development is supported by the simulation of welding processes using the finite element method (FEM). This enables precise predictions to be made regarding process parameters and the design of cell contacting systems.

Electrothermal simulations of battery modules in operation, as well as the influence of contact resistances and cell positions on cell behavior and aging processes, are also taken into account.

Our R&D Services on the Topic  "Cell Connection Technologies for Battery Modules" Include:

• Design of Battery Modules
• Manufacturing of Battery Modules
• Process Development for Innovative Interconnection Concepts
• Characterization of Welding Processes
• Microstructural Analysis of Joints
• Non-Destructive Characterization
• Analysis of Long-Term Stability

In collaboration with Battery Engineering, we offer the design of innovative battery modules. To achieve this, we use FEM simulations and customized joining processes to ensure the most homogeneous current distribution possible for battery cells connected in parallel. This homogenization is crucial for increasing service life and efficiency of battery modules. The intelligent interconnection of battery cells reduces the load on the battery management system: microcycles between cells are reduced, and battery control is simplified. This leads to improved performance and a longer service life for the battery modules.

In addition, we offer the design of cell contacting systems. Based on electrical and thermal modeling, we optimize the design for optimal current flow and maximum material savings.

Together with our Battery Prototyping and Manufacturing team, we support you in the production of battery modules. You have access to our expertise in connection and system technology. Don’t want to interrupt your production line or benefit from our extensive knowledge in process development? Would you like to test new connection technologies or module concepts on prototypes or pilot production runs? We are happy to implement innovative interconnection topologies for you, such as single-sided contacting, position-dependent joining processes, and the use of cell contacting systems made of aluminum or copper. This allows us to help you increase the energy density and longevity of your products.

Do you want to test individual battery cells in accordance with standards or beyond? We also offer the service of electrically contacting battery cells for testing.

Take advantage of our expertise in implementing innovative and novel interconnection concepts for battery modules. We use precise FEM process simulations to predict optimal welding parameters and to design gap structures and projections. Benefit from our capabilities in resistance spot welding, as well as laser welding and laser bonding. With our expertise, we implement innovations in process control for single-sided interconnections or short-time resistance projection welding for various cell types and formats. Rely on our capabilities to develop the next generation of your battery modules without interrupting series production.

Intelligent process development is inconceivable without detailed process characterization. We analyze welding process data and monitor the welding processes in detail. To this end, we also measure the resulting electrical and mechanical properties of the joints and draw conclusions about the process conditions.

Are you a system manufacturer and want to know how your designs affect the welding process? Using high-frequency infrared and contact temperature measurement technology, we monitor the welding processes and determine their homogeneity.

With the correct process control for interconnecting the battery cells, we lay the foundation for high safety and uniform aging of the battery cells within the battery module.

Would you like to determine the influence of the composition of cell contacting systems or coatings on welding processes, joints, or their long-term stability? Would you like to determine the penetration depth and ensure that the battery cells are not damaged during welding? Using microstructural analysis, we can help you find answers to these questions and analyze details of the microstructure that would otherwise be inaccessible. We use methods of materialography and microscopy to detect heat-affected zones, process control, absence of damage, and grain structures, as well as for surface analysis. For dissimilar joints, we use scanning electron microscopy and energy-dispersive X-ray analysis to identify microstructural changes, phase formation, and diffusion zones. We determine hardness and brittleness via nanoindentation. To do this, we draw on the Fraunhofer ISE’s many years of experience in joining technology and its excellent laboratory equipment.

Are you looking to reduce production scrap? Would you like to evaluate fast, in-line, non-destructive quality control methods or innovative characterization techniques? We offer various methods for the non-destructive analysis of battery cell joints. Using scanning acoustic microscopy, micro-computed tomography, and X-ray inspection, we assess the quality of welded battery cells. This allows us to identify the bonding surface or any anomalies.

In addition, we are testing innovative methods such as the optical microphone and further developing them with our partners to enable correlations between the quality of the joints and the analysis data, as well as insights into the process parameters.

Would you like to test the long-term stability of your battery modules or joints? Do you join dissimilar metals – such as aluminum and copper – and want to understand how these joints affect your battery modules? Would you like to age your battery systems as a whole? We offer various methods to improve the quality of your products and quickly identify failure mechanisms. We use accelerated thermal cycling tests or thermal aging to trigger the growth of (intermetallic) phases or electromigration, shaker and vibration tests, and much more. The subsequent microstructural analysis allows us to gain deep insight into the causes of aging effects compared to the initial state. Benefit from our many years of expertise.

Are you interested in the aging of battery cells? Our post-mortem analysis examines failures in individual components.