Question: What do shopping for a new suit and battery manufacturing have in common? Answer: You can have a standard version that’s nice and (relatively) inexpensive. Or one that fits you perfectly but comes at a price. Or at least that’s how it used to be – until researchers at the Karlsruhe Institute of Technology (KIT) found a solution to make battery cell manufacturing not just more flexible but also more efficient. From coil to stack
The new process, called “Coil2Stack,” is designed to address a specific challenge within battery cell manufacturing: There is a growing demand for highly individual cell formats that fit the target application – say, a smartphone or an electric car battery – perfectly. Yet these cells are currently produced by rigidly linked production lines that are neither highly economical nor flexible. How to resolve this? By developing a process for flexible cell stack formation that enables individual cell formats. How does it work? For an explanation, we must look at how battery cells are currently made.
Unwinding of a process
Battery cells consist of an anode, a cathode (the electrodes), and a separator. To achieve a high cell density, these components are wound into a tight coil around a mandrel. This is a critical process, as winding can cause stress in the materials and lead to premature aging or defects in the cell. The Coil2Stack process, in contrast, uses a precision machine that can convey the electrodes and the separator, cut and handle the electrode and separator sheets, and neatly place them in a stack. This way, there is no winding stress or damage. Plus, because the machine has several movable axes, it can do so for a wide range of different sizes, and the position of the individual sheets can be varied during the stacking process. This makes the process uniquely versatile – and significantly simplifies manufacturing.
What’s in a toolbox
But why are we so excited about this development? Well, first of all, this process will help battery manufacturers make more individual cells with higher precision and quality, as well as helping increase battery performance in terms of capacity and longevity. Second, this new process was developed here in Germany, using the manufacturing and technology expertise that we consider to be a trademark of German engineering. And finally, we supported this project with a dedicated control and drive solution based on our standard automation portfolio. In order to combine the handling, cutting, and stacking process into a single machine, the project team needed a highly flexible and high-precision solution that would be able to both control the unwinding of the components with minimum stress and accurately handle the stacking process within a broad format range. For this purpose, we provided a solution based on our SIMATIC S7-1500 TCPU, SINAMICS drives, and 1FK2 motors. The entire application was engineered using the Converting Toolbox, a library that comprises standard functions for production machines that process continuous material webs (such as the components of battery cells). We also supported the commissioning of the new machine.
A change of direction
With the new machine, battery cells can be essentially made to measure with minimal changeover times – allowing for individual formats without the restrictions of today’s rigid, high-volume production lines. Now, formats can be changed in a continuous process by modifying parameters, which “enables the efficient, precise, and flexible production of cell stacks. We accelerate the production process and at the same time make the production line independent of formats,” says Prof. Dr.-Ing. Jürgen Fleischer, director at the wbk Institute of Production Science at KIT. We congratulate our colleagues in Karlsruhe on this achievement – and feel very much honored to have been part of this ingenious solution.
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