Influence of Cathode Materials on the Characteristics of Lithium-Ion Battery Gas Generation During Thermal Runaway

Gas generation of Lithium-ion batteries(LIB) during the process of thermal runaway (TR), is the key factor that causes battery fire and explosion. Thus, the TR experiments of two types of 18,650 LIB using LiFePO4 (LFP) and LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) as cathode materials with was carried out with different state of charging (SOC) of 0%, 50% and 100%.The temporal variation of battery vent gas (BVG) during the TR process by a multi-component gas measuring instrument and a gas chromatograph. Results showed that both the BVG compositions of LFP battery and NCM622 battery were CO₂, H₂, CO and alkane. The evolution process of BVG in TR can be divided into four stages: gas gestation stage, safety valve opening, accelerated jet and jet termination.The main combustible gases appeared in the order of H₂ > CH₄ > VOC > CO. The order of gas concentrations were CH₄ > H₂ > VOC > CO. For LFP batteries, the concentrations of CH₄, H₂, VOC and CO increase with SOC, and no combustion behaviors were observed during the three cases of SOC is 0%, 50% and 100%. While for NCM622 batteries, fire occurred at the case of 100% SOC, and the jet sparks brought a sharp rise of the concentrations of H₂, VOC and CO in BVG. The results of battery gas production provide a basis for battery safety monitoring and a new idea for the analysis of battery TR ignition behavior.