Experimental study on thermal runaway and flame eruption characteristics of NCM523 lithium-ion battery induced by the coupling stimulations of overcharge-penetration

The thermal runaway of lithium-ion batteries under extreme coupled abuse conditions has seriously hindered the sustainable development of lithium-ion new energy vehicles. To reveal the complex thermal runaway behavior mechanism of overcharged lithium-ion batteries induced and by nail penetration, In this paper, a coupled stimulated thermal runaway experimental platform was built, and experimental studies of overcharge-penetration coupled stimulated thermal runaway and flame eruption dynamics were carried out on 18650-type NCM523 lithium-ion batteries from macro and minutiae viewpoints, in which the states of charge (SOC) of the overcharged batteries were 100 %, 105 %, 110 %, 115 %, 120 %, 125 %, 130 %, 135 %, 140 %, 145 % and 150 %. The results showed that the maximum battery surface temperature during overcharging increased from 32.7°C at 100 % SOC to 66.1°C at 150 % SOC, an improvement of 102 %. The thermal runaway battery temperature increased from 529.0°C at 100 % SOC to 657.1°C at 150 % SOC, an increase of 24.2 %. The thermal runaway maximum flame temperature increases from 485.5°C at 100 % SOC to 983.9°C at 150 % SOC, an improvement of 102.6 %. The flame area of medium overcharged> high-level overcharged> low-level overcharged batteries and the flame area of thermal runaway increased by 22213.95 cm2 compared to the maximum of 100 % SOC, and the flame propagation speed of the batteries after thermal runaway showed that the greater the SOC, the stronger the intensity of the flame. The higher the degree of overcharging, the higher the danger of thermal runaway on the side of the battery and near the positive electrode, and the danger of thermal runaway in overcharged lithium-ion batteries increases with the increase of SOC.