Interview with Jonas Gorsch, RWTH Aachen University
“The cell-to-pack (CTP) approach is gaining traction”
Gorsch's core expertise includes the design and simulation of advanced lithium-ion battery cells, with a particular focus on electro-thermal behaviour, high C-rate performance, and mechanical optimisation. He has led multiple development projects, including early-stage design of prismatic and cylindrical cell formats.
PEM
Tesla and BYD set the pace in cell innovation. In this interview, Jonas Gorsch – a speaker at the Automotive Battery Conference 2025 – reveals what European developers must learn to scale next-gen battery production.
Jonas Gorsch, M.Sc., is Lead for Cell Engineering and Research Associate in the Battery Engineering and Safety group at PEM, RWTH Aachen University. He holds a Master of Science degree in Mechanical Engineering and has several years of project experience across the battery value chain — from concept design to production process evaluation.
Currently, Gorsch heads the cell thermal simulation work package within the Fraunhofer Research Factory for Battery Cells (FFB) in Münster. As part of his PhD research, he is developing a methodology to predict full-cell thermal behaviour based on small-scale cell tests, aiming to improve thermal alignment between system and cell design.
ADT: What are the most significant trade-offs in cell design choices between the leading EV manufacturers?
Gorsch: From a holistic perspective in automotive engineering, the primary trade-offs in lithium-ion battery cell design are between energy density/range, fast-charging capability, and cost. These are further complemented by requirements such as safety, sustainability, and lifetime. All this leads to inherently conflicting objectives, requiring compromises and optimisation for a specific application during cell design. A good example on the material level is the choice between lithium iron phosphate (LFP) and nickel manganese cobalt oxide (NMC) chemistries. LFP cells offer high thermal stability, excellent cycle life, and lower material cost, alongside good fast-charging performance. However, they suffer from lower energy density, which limits vehicle range. In contrast, NMC cells deliver superior energy density and thereby extended range, but they come with increased material cost and more complex thermal management needs due to reduced stability and higher specific heating at the electrode level.
Are these trade-offs apparent for all specific cell design choices?
They are apparent for almost every specific cell design choice. For example, the addition of carbon black as a conductive additive in the electrode matrix can enhance electronic conductivity and thus improve power performance and charge rates. However, it also leads to increased cost and reduced volumetric energy density due to inactive material content. Ultimately, EV manufacturers must optimise these parameters based on targeted vehicle applications and market positioning - balancing performance, range, and economics through tailored cell design.
How do format and architecture impact scalability and system integration in large-scale EV production?
The choice of cell format and size plays a pivotal role in both the scalability of cell production and the integration into the battery systems. Pouch cells, for instance, offer significant advantages in terms of manufacturability. From a pure cell assembly perspective, they are the easiest to scale due to their comparatively simple design structure. However, they present considerable challenges at system level, including more complex handling due to flexible current collectors, the need for effective degassing and safety strategies, and precise pressure management during integration. Another critical design factor is the electrode configuration. Rolled (jelly roll) electrodes enable higher production throughput and easier control of tolerances for anode-to-cathode alignment, making them favourable for high-speed manufacturing. In contrast, stacked electrodes typically offer energy density benefits but complicate the production process and increase manufacturing complexity. Cell size is another key parameter. Larger format cells, such as the 4680 cylindrical cell, reduce the number of individual units required per pack to achieve a specific energy output of the factory.
Can you give an example?
For example, to achieve the same energy output, a factory producing “21700” cells must manufacture approximately five times more cells than one producing “4680” cells. This also significantly simplifies pack assembly, as fewer cells need to be handled, electrically connected, and managed thermally, while in cell production, the cycle time per cell during cell assembly can be increased - for example, it is easier to do one longer weld on a larger cell than to do five smaller welds on smaller cells.
Why is the cell-to-pack approach gaining importance?
At system integration level, reducing complexity and the number of manufacturing steps is crucial. The cell-to-pack (CTP) approach is gaining traction for its ability to eliminate intermediate module structures, thereby improving packaging efficiency and reducing cost, while also reducing the number of parts and assembly steps needed. Pioneered by companies like BYD with its blade batteries and Tesla with its structural packs, CTP has proven to be viable across fundamentally different cell formats. Overall, the optimisation of these trade-offs must be closely aligned with the requirements of the specific vehicle application, while always keeping scalability in mind. This balance is perhaps the most pressing challenge facing European cell manufacturers such as PowerCo, ACC, and Verkor, who are still in the process of demonstrating that they can scale their technologies effectively. Northolt’s recent setbacks in scaling highlight just how difficult this transition from pilot to gigafactory scale can be. Here, a key factor is also to focus on clear design formats for scaling and not try to scale different cell format technologies at the same time without prior experience.
What can European cell developers learn from the approaches of Tesla and BYD?
One of the most important lessons from the success of Tesla and BYD is the critical importance of detailed design decisions - even at the smallest design features - for the scalability of battery cell production. Scalability is not simply about capacity expansion. It is fundamentally shaped by the robustness and manufacturability of the cell design and process technology choices. Both Tesla and BYD have demonstrated the value of maintaining a sharp focus on a well-optimized cell format. Tesla has concentrated its development and manufacturing efforts on the cylindrical 4680 cell, while BYD has centered its strategy around prismatic blade cells. This focus enables vertical integration, process optimization, and efficient scaling. At the moment, they also have a clear focus on a singular cathode chemistry, which in turn is also crucial, as the details of the process parameters for high-speed production of electrodes with these materials are more material-specific and challenging.
Can you give a practical example?
As a design choice example, Tesla eliminated the traditional electrode tabs used in its “21700” cells, which were welded on uncoated electrode areas. This innovation allows for continuous electrode coating, which is essential for implementing dry electrode processing, as dry coating is even more challenging if attempted in a discontinuous manner. On the other hand, BYD’s Z-folding and separator lamination strategy for its blade cells represents a clever mechanical solution to a scaling problem. By laminating the separator edges to form a kind of “pouch” around the stacked electrodes, BYD achieves stable fixation of large electrode assemblies, minimising misalignment and handling issues during high-speed automated production. A key takeaway here is that even seemingly minor design choices, such as electrode separator edge fixation, can have major implications. Poorly optimised details can result in significant cost overruns or yield losses when scaling from pilot lines to gigafactory-level production. Therefore, European cell developers must take a “design for scalability” approach from the outset, integrating lessons from the scale-up successes - and failures - of global leaders and their own pilot lines. Ultimately, robust industrialisation strategies, including a clear commitment to process simplicity and manufacturability, are essential. This is particularly relevant for emerging European players, who face the dual challenge of developing competitive technology and proving they can scale it reliably.
