Pressure evolution and gas solubility of Li-ion battery electrolytes during thermal abuse conditions

Understanding and controlling the evolution of pressure during thermal events of Li-ion batteries is a key aspect when assessing the safety of Li-ion batteries. In this study we evaluate the impact of solvent composition, gas solubility, and conductive salts on the pressure build-up during the exposure of the Li-ion battery electrolytes to high temperatures.
We employ a vapour–liquid equilibrium model based on the statistical associating fluid theory (SAFT)-
Mie equation of state, extended to include an ion-pairing model to account for low degrees of salt dissociation in solvents with a low dielectric constant, such as linear carbonates. The effect of the degradation gases is accounted for by implementing a gas source mimicking a CO2 evolving reaction.
We find that argon or nitrogen are good choices as inert gases during solvent storage and cell assembly, as they only gas out slightly during heating, i.e., they cause a negligible increase in pressure. Moreover, linear carbonates are found to be preferable over their cyclic counterparts regarding battery safety, as the higher solubility of degradation gases such as CO2 in the electrolytes will mitigate pressure evolution during a thermal event. ... mehrThe presence of the conductive salt is found not to have a substantial effect on the pressure evolution.
The insights into the sensitivities of the pressure evolution presented here will allow to precisely tailor the composition of an electrolyte mixture to mitigate safety-critical gas evolution during a thermal event in Li-ion batteries.