PhD in Mechanical Engineering: 3D modeling of the ejection and combustion of vented gases during the thermal runaway of Lithium-ion battery cells

The rapid growth in the use of electric vehicles has led to a strong demand for batteries. Lithium-Ion batteries are currently the dominant technology, as they offer good performance, in particular high energy density. Nevertheless, these batteries can be subject to thermal runaway, potentially leading to the destruction of the
vehicle. It is therefore important to develop adequate numerical tools to predict and prevent this type of accident. Many existing numerical models allow to simulate internal chemical reactions in a battery cell undergoing thermal runaway and the thermal conduction within the surrounding cells. However, gases are ejected during the runaway process and can even ignite. The impact of these hot gases and their combustion on the cell temperature and therefore on the propagation of the thermal runaway within a battery pack is currently poorly understood and modeled. The use of multi-dimensional calculations (2D and more particularly 3D) is necessary to correctly predict these effects. The challenge is then to: (i) predict the gas composition and velocity at the cell exit; (ii) predict the gas combustion in the external environment of the battery. The objective of this thesis is to develop a coupled 3D model, which considers the thermal runaway inside the cell, the thermal conduction, the dynamics and the combustion of the gases generated by the reactions inside the cell, and the convective heat transfer induced by these gases on the cell. The results will be compared with experimental measurements currently carried out at IFPEN. The thesis will proceed according to the following milestones: (i) Implementation in the CFD solver of the thermal runaway model of the battery using IFPEN know-how; (ii) Implementation of a model predicting the venting of gases from the cell; (iii) Coupled simulation with combustion of an isolated cell and confrontation with the experiment; (iv) Simulation of thermal runaway propagation in an industrial battery pack.

Keywords: Li-ion batteries, combustion, thermal runaway, 3D simulations, heat transfer, gas venting

Academic supervisor: Pr. Ronan VICQUELIN, CentraleSupelec, ORCID 0000-0002-2055-5244

Doctoral School: ED579 SMEMAG

IFPEN supervisor: Dr. Cédric MEHL, ORCID 0000-0003-2293-9281