A ‘Microscopic’ Structural Mechanics FE Model of a Lithium-Ion Pouch Cell for Quasi-Static Load Cases

This study deals with the experimental investigation of the mechanical properties of a lithium-ion pouch cell and its modelling in an explicit finite element simulation code. One can distinguish between ‘macroscopic’ and ‘microscopic’ modelling approaches. In the ‘macroscopic’ approach, one material model approximates the behaviour of multiple inner cell layers. In the ‘microscopic’ approach, which is used in the present study, all layers and their interactions are modelled separately.
The cell under study is a pouch-type lithium-ion cell with a liquid electrolyte. With its cell chemistry, design, size and capacity it is usable for automotive applications and can be assembled into traction batteries.
One cell sample was fully discharged and disassembled, and its components (anode, cathode, separator and pouch) were examined and measured by electron microscopy. Components were also tensile tested. In this way, each component was fully characterised with respect to the properties needed for explicit finite element models.
Multiple quasi-static mechanical tests at different state of charge (SOC) levels under various load cases were conducted. Test results were used to validate the numerical cell model.
Simulation of the mechanical behaviour of individual cell layers and the entire cell showed a very reasonable correlation with experimental testing. The developed structural mechanics model for quasi-static load cases is a solid starting point for future analyses, and opens the possibility to predict cell damages with explicit finite element simulations.