Separator finite-element modelling for a better prediction quality of short circuits within Li-ion cells caused by mechanical loads

To increase the current quality of mechanical simulation results and the virtual short-circuit prediction of battery cells, detailed simulation models for cell components are necessary.
In order to avoid internal short circuits, the electrodes are electrically and spatially separated from each other by using a separator which occupies a key safety-relevant position. The separator failure is assumed to be an important indicator of an internal short circuit. Therefore, the shown research activity focuses on the improvement of mechanical separator modelling.
By using a meso-mechanical modelling approach the simulation model can predict mechanically induced short circuits within the cell components based on physical parameters. This model scale describes the material behavior of the battery components on homogenized single layer levels. To generate the input parameters for such material models the cell components go through various mechanical tests (e.g. tensile and compression tests) with different boundary conditions. By direction-dependent testing of dry or wet-produced separators at different speed it is possible to differentiate between their orthotropic or isotropic mechanical behavior. Depending on the production process and separator type anisotropy can be weaker or stronger.
By varying the separator type or even single parameters (thickness, etc.) in the meso-mechanical cell model influences on the mechanical behavior – especially the mechanically induced short circuit behavior – can be easily investigated. This model can be used for decision support in early design stages based on the cells field of application and can help to reduce expensive prototyping and testing. Another possible usage of the separator model is to use it for component or cell production simulation purposes.