Battery cell production at high speed Innovative high-speed stacking for lithium-ion battery cells

Lithium-ion battery cells largely consist of electrodes that have to lie neatly on top of each other. In industrial production, building up this stack of electrodes has been a particularly demanding process, both technically and in terms of the time required. Many successive handling steps and quality controls slow down the stack build-up, but are necessary for precise and damage-free positioning and fixing of the electrodes in the stack. Due to the challenging positioning and fixing, the stack formation to date is the major bottleneck in battery cell production and thus prevents cost-effective and high-throughput series production. In order to significantly increase the speed and at the same time avoid damage in the stack formation, an innovative process was developed at Technische Universität Braunschweig.

In the process that has been developed, the electrodes are positioned and fixed in the stack at high speed. In order to do this, an electromagnetic field is generated that triggers eddy currents in the electrodes to be stacked. These eddy currents in turn form their own electromagnetic fields, which are directed in the opposite direction to the generating field. The interaction of all electromagnetic fields results in forces that precisely position and securely fix the electrodes on the stack. The forces act immediately and without contact, so that the process time of stack formation is minimised and damage to the electrodes is prevented.

Another advantage of the process: it requires neither compressed air or other process media, nor the use of motors or moving components, and is thus superior to the previously established positioning and fixing in stack formation.

Flexibly deployable for a wide variety of existing and future electrode materials and sizes

A prototype was built for testing at the Institute for Machine Tools and Production Technology. Using this, the significant improvements compared to the previous stack formation could be demonstrated in various experiments. The experiments and further simulations also show that the high-speed stack formation achieved can be used flexibly for a wide range of existing and future electrode materials and is scalable to the large electrode formats used in industry. As a result, the developed process increases both the speed and the quality of stack formation and is thus a key technology for economically efficient battery cell production.

Technische Universität Braunschweig has filed a patent application for the described high-speed stack formation based on electromagnetic fields and is aiming for industrial utilisation in national and European battery cell production.