Thermal runaway features of large-format power lithium-ion cells under various thermal abuse patterns and capacities

Herein, a comprehensive investigation is performed to research the thermal runaway features of large-format power lithium-ion cells under various heating patterns (2 kW electric heating oven and 600 W electric heating plate) and capacities (60, 150, and 180 Ah). Although the electric heating plate induces the cell to encounter thermal runaway earlier in comparison with the electric heating oven, the combustion does not appear for the former case since the compact stacking of the electric heating plate restrains the heat release of the heater such that the surrounding temperature is too low to induce the ignition of the thermal runaway combustibles. Besides that, it is interesting to find that the color of the ejected products under the electric heating plate condition becomes shallower as the thermal runaway proceeds, which implies that the ejecta in the initial of thermal runaway is mixed with quantities of solid particles and the proportion would gradually decrease. With the increase of the cell capacity, thermal runaway emerges later as a result of the greater cell height which delays the cell temperature rise, when exposed to an electric heating oven. In addition, the cell with a larger capacity demonstrates a lower peak temperature, a lower maximum temperature rise rate, a shorter combustion, a lower flame temperature, and a weaker radiation heat strength during thermal runaway; that is, less heat is released due to its violent thermal runaway behaviour. Finally, the severe explosion risk for the larger-capacity cell should be especially noted considering the larger amount of explosive gases released.