Thermal runaway characteristics of 18650 lithium-ion batteries in various states of charge

The lithium-ion battery (LIB) is a significantly and broadly used power storage system known for its high energy density and extended lifespan. However, it is vital to continue examining and addressing potential safety concerns that require further exploration and discussion. This study employed a pseudo-adiabatic calorimeter, vent sizing package 2, to assess the thermal runaway behaviour exhibited by 18650 LIBs under diverse charging conditions. Through calorimetric experimental trials, the charge levels of the batteries at 0%, 30%, 50%, 80%, and 100% were assessed. This allowed us to identify and evaluate the thermal characteristics that pose potential hazards or risks, such as apparent exothermic onset temperature ( T 0 ), self-heating rate (d T /d t ), pressure rise rate (d P /d t ), maximum temperature ( T max ), maximum pressure ( P max ), and pressure–temperature-time profiles. When a fully charged LIB experienced thermal runaway, it reached a T max of 902.9 ℃ and a P max of 1985.2 psig. These experimental findings can be utilised to estimate uncontrolled thermal behaviours and thermokinetic parameters across different charge states of the 18650 LIB. These results demonstrate practical applications as well as implications in designing batteries with proactive safety measures and can provide essential parameters for ensuring the process safety of commercial batteries, thereby preventing thermal damage. Based on the adiabatic temperature rise (∆ T ad ) and P max , the venting gas molar amount was also calculated through the ideal gas equation, and the generation of flammable gases was considered a significant factor in the uncontrolled combustion of LIBs.