Gas-Evolution Induced Volume Fraction Changes and Their Effect on the Performance Degradation of Li-Ion Batteries

Li-ion batteries swell due to gas evolution that results from decomposition of the electrolyte and from reaction with impurities. To study dimensional changes in Li battery cells, we derive a model for gas-evolution induced volume fraction changes in both electrolyte and inert material phases in composite Li-ion electrodes. The nonlinear increase in cell resistance is explained using volume fraction changes within the context of physics-based modeling. The simulation results given here are also used to map the effects of volume fraction changes on the discharge curve and on heat generation.