Thermal Runaway of Large Format Pouch Lithium Ion Cell with Internal Temperature Detection Using Extended Volume Accelerating Rate Calorimetry

Abstract

Extended volume accelerating rate calorimetry(EV-ARC) has been widely used to judge the thermal runaway(TR) behaviors of large format lithium ion cells in adiabatic atmosphere[1].Generally, when temperature reaches the onset temperature(approximately 90℃)，self heating of the cell begins due to the solid electrolyte interface(SEI) decomposition. And other exothermic chemical reactions start when temperature reaches their onset temperature. These reactions will heat the cell and at last lead to thermal runaway of the cell. The onset temperature, triggering temperature and maximum temperature are important factors to judge hazardous during TR. When testing TR of pouch cells using EV-ARC, the thermal couple is always placed between two side by side cells[2]. However, temperature detected between two cells is not the real temperature inside battery. In this work, the thermal couple is inserted into the cell directly to detect the inside temperature of cell(see Figure1). The capacities of fresh cell and operated cell are almost the same. Then, the EV-ARC tests of both cells are conducted and compared. In the result, the onset temperature of both cells are almost the same. The triggering temperature of cell with thermal couple inside is about twenty degree higher than that detected between two cells. And the maximum temperature of cell with thermal couple inside is also dozens of degree higher than that with traditional test method. Figure 1