CFD Modeling of 18650 Lithium-Ion Cell to Predict Cell Gas Venting and Gas Phase Reactions during Thermal Runaway Event

<div class="section abstract"><div class="htmlview paragraph">To understand effect of thermal hazards of LIBs during TR event, it is important to study flame propagation behaviour of LIBs during storage and transport applications. The process of flame propagation involves complex phenomena of gas phase behavior of LIBs. Present paper attempts a numerical investigation to portray this complex phenomenon. This paper investigates 18650 lithium cell considering two different chemistries NMC and LFP.</div><div class="htmlview paragraph">A 3D numerical CFD model has been constructed to predict the gas phase behavior, threshold internal pressure, and cell gas venting of an 18650-lithium cell under thermal runaway conditions. The gas phase processes are modelled using the 4-equation thermal abuse model, while the cell's venting mechanism is modelled using Darcy's equation. Present work is divided into two parts: 1) Venting gas Internal pressure prediction 2) modeling thermal runaway event. Both procedures are implemented on two different cell chemistries to understand and evaluate following parameters: Vent gas internal pressure, Flame propagation during thermal runaway, flame length comparison, total heat prediction and temperature of flame during thermal runaway event. Cells with NMC and LFP chemistries are modeled and compared at 100% SOC condition. The comparison of the above numerical output parameters for both chemistries reveals that, in contrast to 18650 NMC cell, the flame length of the LFP cell after a thermal runaway event is 74% lower. According to the study, the threshold internal pressure at the valve opening of the LFP cell is 68% lower than that of the NMC cell. Thus, researchers and industry professionals can comprehend the 3D nature of flame propagation as well as the mechanics of cell venting thanks to this precise 3D modelling method. The numerical model uses commercial 3D ANSYS FLUENT code to adapt the well-known RANS technique for modelling the thermal runaway event.</div></div>