Experimental Analysis of Thermal Runaway Energy Release of an Automotive Li-Ion Battery Cell

Abstract

Thermal runaway (TR) reactions of lithium ion cells pose a particular risk to the safety of battery systems. Beside the energy remaining in the cell body, particles and gases exiting the cell during the venting process cause major thermal load for adjacent cells and further system components [1]. In addition, high energy particles can act as an ignition source in the presence of ignitable venting gases and oxygen [2]. Therefore, measurements minimizing the risk of thermal propagation (TP) caused by venting ejecta material and the ignition of combustible gases are introduced on system level. For the dimensioning of the measures, the energy transported by venting particles and gases is identified as a crucial parameter. Depending on the amount of transported energy, the gas cooling distance as well as the complexity of the particle separation structure differ. Simulation methods are used to evaluate the effectiveness of such system measures. More information is needed regarding energy release to accurately predict the system behavior in simulations and to use them as a tool for design.Introducing a novel approach for TR tests enables the determination of the energy remaining in the cell body, separated from the energy transported by venting ejecta. The test setup combines a calorimeter combined with a cyclone separator placed inside an autoclave reactor. The TR energy release of 156 Ah prismatic lithium ion cells have been analyzed using the setup. Venting particles and gases transported a main part of the released energy out of the cell during the TR. Using an analytical approach, the energy transferred to the calorimeter is calculated. The obtained data can be used for validating simulation models for predicting the impact of venting reactions on TP.