Thermal runaway hazards investigation on 18650 lithium-ion battery using extended volume accelerating rate calorimeter

With the increase of lithium-ion batteries energy density and capacity, the thermal runaway (TR) is becoming a significant issue that can't be ignored. In this work, one kind of commercial 18650 lithium-ion battery with different states of charge (SOCs) and cycling times is used to evaluate the TR hazards by a ramp heating method in an extended volume accelerating rate calorimeter. Some thermal characteristic parameters are selected and analyzed from the experiment trails, such as the cell surface temperature, temperature rise rate, canister internal pressure and average canister surface temperature. The experiment results show that the maximum surface temperature of the battery and the maximum canister internal pressure increase with the increase of SOC when the TR occurs. The thermal energy released from the battery during TR is calculated using the initial and the maximum temperature on the battery and the canister surface. A fully charged fresh battery can release 61.72 kJ energy when it gets into TR, which could be converted to an explosion equivalent of 5.57 g TNT-equivalent. Compared with fresh batteries, aged batteries are more prone to get into TR and the TR hazards increase.