Scenario-based prediction of Li-ion batteries fire-induced toxicity

• Combustion tests of 1.3 Ah based LiFSI and LiPF6 cells using Tewarson apparatus.
• Data processing of ‘source terms’ for thermal and toxicity impact assessment.
• Analysis of a 100 cells – 6.5 Ah module fire scenario in a 30 m3 ventilated enclosure.
• Comparative fire induced toxicity as differentiated from the salt viewpoint.

The development of high energy Li-ion batteries with improved durability and increased safety mostly relies on the use of newly developed electrolytes. A detailed appraisal of fire-induced thermal and chemical threats on LiPF6- and LiFSI-based electrolytes by means of the so-called “fire propagation apparatus” had highlighted that the salt anion was responsible for the emission of a non negligible content of irritant gas as HF (PF6−) or HF and SO2 (FSI−). A more thorough comparative investigation of the toxicity threat in the case of larger-size 0.4 kWh Li-ion modules was thus undertaken.A modeling approach that consists in extrapolating the experimental data obtained from 1.3Ah LiFePO4/graphite pouch cells under fire conditions and in using the state-of-the-art fire safety international standards for the evaluation of fire toxicity was applied under two different real-scale simulating scenarios. The obtained results reveal that critical thresholds are highly dependent on the nature of the salt, LiPF6 or LiFSI, and on the cells state of charge. Hence, this approach can help define appropriate fire safety engineering measures for a given technology (different chemistry) or application (fully charged backup batteries or batteries subjected to deep discharge).