Thermal-Runaway Propagation over a Linear Cylindrical Battery Module

Thermal-runaway propagation in battery systems can escalate the battery fire hazard and pose a severe threat to global users. In this work, the thermal-runaway propagation over 18650 cylindrical lithium-ion battery was tested in the linear-arranged module with a 3-mm gap. State of charge (SOCs) from 30% to 100%, ambient temperatures from 20°C to 70°C, and three tab-connection methods were investigated. Results indicate that the battery thermal-runaway propagation speed was about 0.35 ± 0.15 #/min, which increased with SOC and ambient temperature. The critical surface temperature of thermal runaway ranged from 209°C to 245°C, which increased with ambient temperature while decreased with SOC. Compared to the open-circuit module, the flat tab connection could cause an external short circuit to accelerate the thermal-runaway propagation, and the non-flat tab connection was more likely to trigger an explosion. A heat transfer analysis was proposed to qualitatively explain the speed and limiting conditions of thermal-runaway propagation, as well as the influence of SOC, ambient temperature, and tab connection. This work reveals the thermal-runaway propagation characteristics under well-controlled environments, which could provide scientific guidelines to improve the safety of the battery module and reduce battery fire hazards.