*Article* **Comprehensive Hazard Analysis of Failing Automotive Lithium-Ion Batteries in Overtemperature Experiments**

#### **Christiane Essl 1,\*, Andrey W. Golubkov 1, Eva Gasser 1, Manfred Nachtnebel 2, Armin Zankel 2,3, Eduard Ewert 4 and Anton Fuchs 1**


Received: 6 April 2020; Accepted: 4 May 2020; Published: 18 May 2020

**Abstract:** Lithium-ion batteries (LIBs) are gaining importance in the automotive sector because of the potential of electric vehicles (EVs) to reduce greenhouse gas emissions and air pollution. However, there are serious hazards resulting from failing battery cells leading to exothermic chemical reactions inside the cell, called thermal runaway (TR). Literature of quantifying the failing behavior of modern automotive high capacity cells is rare and focusing on single hazard categories such as heat generation. Thus, the aim of this study is to quantify several hazard relevant parameters of a failing currently used battery cell extracted from a modern mass-produced EV: the temperature response of the cell, the maximum reached cell surface temperature, the amount of produced vent gas, the gas venting rate, the composition of the produced gases including electrolyte vapor and the size and composition of the produced particles at TR. For this purpose, overtemperature experiments with fresh 41 Ah automotive lithium NMC/LMO—graphite pouch cells at di fferent state-of-charge (SOC) 100%, 30% and 0% are performed. The results are valuable for firefighters, battery pack designers, cell recyclers, cell transportation and all who deal with batteries.

**Keywords:** battery safety; hazard analysis; gas analysis; lithium-ion; thermal runaway; vent particle analysis; vent gas emission
