Numerical Study on Energy Density and Thermal Runaway According to the Size of Lithium-ion Batteries

In this study, the energy density and thermal runaway phenomenon of the NCM811 lithium-ion battery according to the 21700/46800 two sizes were analyzed numerically. The 46800 battery cell had a five times higher energy density than the 21700 battery cell, and when placed on the same battery platform, the total energy capacity was approximately 88,800 Wh and the energy density averaged 315 Wh/kg, which is approximately the energy capacity of the 21700 battery pack. 18.3%, the energy density is predicted to be about doubling. If the weight of the 46800 battery cell is reduced and the efficiency of the cell to pack technology that composes the pack without a module is improved, the energy density will be higher. As a result of analyzing the thermal runaway phenomenon of the 21700/46800 battery cells with a 2D model, the 46800 battery cells showed a thermal runaway phenomenon about 853 seconds later compared to the 21700 battery cells at an external temperature of 150℃. Through this, it was found that, if a fire occurs in a product using a lithium secondary battery, the maximum temperature between battery cells does not differ significantly, but 46800 battery cell is relatively high in terms of stability to secure escape time from the fire area.