Li-ion battery electrolyte vaporisation model: An experimental and computational fluid dynamics approach

Electrolyte leakage from a battery cell can lead to the formation of a dangerous atmosphere in poorly ventilated and enclosed environments due to the high volatility, flammability and toxicity of common electrolyte solvents like dimethyl carbonate (DMC) and diethyl carbonate (DEC). To limit human exposure, the design of detection and warning systems is necessary. To this end, a computational fluid dynamics approach was used to create a vaporisation model to predict the evaporation rate of DMC and DEC, supported by experimental data of the evaporating solvents. All experiments were performed in an enclosed environment with no induced flow. The evaporation flux of DMC and DEC in a fully convective and diffusive environment was 0.70 and 0.15 mg/(cm2 min) at room temperature, respectively. An LES-CFD vaporisation model with a novel liquid-vapour modelling approach was used for the simulation of the evaporated liquids, demonstrating good agreement with the experimental data. The presented model iterated on previous efforts of simulating the evaporation of liquids by accounting for the changes of the evaporation rate brought on by temperature and vapour accumulation around the source, which was done by coupling evaporation, temperature and dispersion modelling dynamically. Results show that DMC was significantly affected by the changes in liquid temperature during the evaporation, highlighting the importance on modelling the local energy balance of the evaporating solvent. The dispersion model showcased good qualitative agreement with the behaviour of heavy gasses, underlining that most of the dispersion of the vapours generated by DMC and DEC is buoyancy-based.