The demand for more powerful lithium-ion cells necessitates new active materials and electrode formulations with higher specific capacities. Silicon and lithium metal are promising candidates for enhancing anodes, but their integration presents challenges, particularly related to significant volume changes—silicon can expand by about 300% during lithiation, and lithium’s deposition can be extensive. Understanding the mechanical behavior of electrodes is crucial for developing future cell generations, necessitating the examination of both reversible and irreversible expansion mechanisms.
To effectively incorporate mechanical behavior into cell design, numerical simulations are invaluable, allowing for early predictions and informed design decisions. Capturing the complexity of battery cells requires precise modeling of individual dimensions and their interconnections.
In preliminary modeling using COMSOL, a 2D coupled mechanical-electrochemical model was created based on the “FFB High-Power” cells. This model accounts for changes in thickness due to lithiation-induced expansion and contraction. It builds on a previously validated electrochemical model and can represent mechanical stress arising from varying charge states, revealing that the separator undergoes the most deformation. The model also demonstrates how changes in geometry affect electrochemical responses, such as increased diffusion resistance through the separator, which alters the open-circuit voltage curve. This integrated approach is essential for optimizing the performance and lifespan of future lithium-ion cells.