Gas Formation in Lithium-Ion Batteries – Modeling Study on Thermal Decomposition

An electrochemical pseudo-twodimensional battery cell model is extended by gas species balances to simulate gas formation following SEI and electrolyte decomposition. A degradation mechanism from literature is applied and validated with experimental data. The extended cell model is embedded into a 3D module model. This multi-scale multi-domain approach is used to investigate the causal interaction between module cooling and cell degradation on electrode level. Comparison simulations illuminate SEI degradation and gas formation at different cooling modes during repeated charge/discharge cycles and for different charging strategies following real life driving loads. The simulation results reveal the onset of SEI degradation at elevated temperatures leading to a noticeable formation of CO2 and C2H4. Long time aging simulations over 130h real driving loads expose only slight impacts of degradation.