Experimental and simulation study on internal thermal runaway development drives venting and flammable gas risk evaluate of Lithium-ion battery

Abstract

Heat generation and gas venting are the primary characteristics of thermal runaway in lithium-ion batteries. The convective and diffusive properties of the venting gas pose significant challenges for hazard analysis and safety assessment of thermal runaway venting. Quantifying the potential combustion risk associated with the vented flammable gases is crucial for ensuring battery safety. In this study, we investigated the thermal runaway venting behavior of Li(Ni_0.8Co_0.1Mn_0.1)O₂ prismatic cells through experimental and simulation methods. The results indicate that the battery has discharged 4.83 mol of combustible gas. The gas composition mainly consists of H₂ (20.5 %), C₂H₄ (12.5 %), CH₄ (5.5 %), CO (27.9 %), and CO₂ (28.6 %). Gas combustion account for 19.6 % of the total venting time. We propose an internal thermal runaway progression-driven venting and flammable gas risk evaluation model. This model assesses the combustion risk of flammable gases during the venting process and identifies high-risk areas where gas combustion may occur, specifically the area 1 m above the safety valve, which exhibits the highest risk for flammable gas combustion and possesses the greatest explosive power. This research is poised to make a significant contribution to the safe design of battery pack systems.