Experimental and Numerical Insights on Battery Venting during Thermal Runaway

Lithium-ion batteries have a well-documented failure tendency under abuse conditions with a significant release of gases and heat. This failure originated from the decomposition reactions within the battery’s electrochemical components, resulting in gas generation and increased internal pressure. To optimize battery safety, it is crucial to understand their behaviors when subjected to abuse conditions. The 18650 format cell incorporates a vent mechanism within a crimped cap to relieve pressure and mitigate the risk of rupture. However, cell venting introduces additional safety concerns associated with flammable gases and liquid electrolyte that flow into the environment. Experiments were performed with two venting caps with well-known geometries to quantify key parameters in describing the external dynamic flow of battery venting and to validate a CFD model. Thus, the jet of pure CO₂ was measured on a dedicated experimental bench using Schlieren’s optical technique and the jet shape and penetration were calculated. The CFD model was validated by comparing the experimental results with those obtained from the CFD model. Furthermore, emissions data from two different cathode chemistries, LFP and NCA, for three distinct SOC´s were collected from the literature [1,2] and simulated using the two venting caps to obtain insights on the spatial and temporal species (CO, CH₄, H₂) distribution. Considering results, species distribution was more dependent on the design of the venting cap, but also on the SOC of the battery.