Experimental and simulated study of thermal runaway characteristics of 16Ah nickel-cobalt-manganese (523) square soft-pack lithium-ion battery

The characteristics of 16Ah nickel-cobalt-manganese (523) square soft-pack lithium-ion battery (16Ah NCM523) during typical thermal runaway (TR) process under abusive conditions including heat, overcharge, and mechanical stress were studied. The heat TR experiment of lithium battery with heating plate as heat source shows that the temperature of 16Ah NCM523 escalates from 19.9 ℃ to 62 ℃. The TR of 16Ah NCM523 occurs violently, and the temperature of the soft package burst is 96.4 ℃. And the voltage sag time during this TR of 16Ah NCM523 obviously laged behind the heat production characteristics of the battery. The results of overcharged TR of 16Ah NCM523 shows that the temperature of 16Ah NCM523 rises andante with a rate not higher than 1℃/s and then reaches 98.5 ℃. Following, the temperature of battery increases rapidly to 481.2 ℃. During overcharged TR of 16Ah NCM523, the voltage begins to drop rapidly 2 s earlier than temperature change, which means that voltage and temperature can be used as early warning signals of overcharged TR. For the nail penetration TR of 16Ah NCM523, at the moment of mechanical abuse, the battery bulges and erupts gas. At the same time, the voltage of 16Ah NCM523 drops to zero in a very short time (<5s), and the temperature rises rapidly to 477.5 ℃, which means voltage, temperature and gas can be used as early warning signals when machinery is abused, but the reserved response time is short. Simulation approaches are employed to analyze the thermal runaway phenomena. The simulation results show good agreement with the experimental results. Among the abuse conditions, it is observed that nail penetration leads to the fastest TR, followed by heating, and finally overcharged. The heat inside the 16Ah NCM523 mainly comes from the reaction heat Qneg of negative active material and electrolyte, the decomposition reaction heat Qsei of SEI film, the reaction heat Qpos of positive active material and electrolyte, and the decomposition reaction Qele of electrolyte. The main inducing factors of internal thermal reaction of 16Ah NCM523 are different with different thermal runaway.