Testing and simplified modelling of deformation behaviour of battery cells

The deformation and failure behaviour of cylindrical, prismatic and pouch cells were characterized under different load situations like compression, bending and indentation. A special testing method with measurement of force, displacement, cell voltage and temperature was used to determine the relationship between mechanical responses and internal short-circuit. It was found that in many load cases the short circuit takes place just after a mechanical instability, which can be determined from the recorded force vs. displacement curve. A great challenge for modeling battery behavior in crash simulation is the development of an efficient method which enables a reliable prediction of battery deformation with indicators for short circuits by using a reasonable calculation expense. Based on experimental results a simplified model was developed to capture the essential deformation character of a pouch cell under different loadings. Instead simulating the complex cell layer structure a homogenized model was suggested and applied to simulate cell tests under compression in different cell orientations. Shell and solid elements in conjunction with compressible plasticity model were used to take into account the orientation dependence of the mechanical behavior and the volume change of the pouch cells.