First Experimental Assessment of All-Solid-State Battery Thermal Runaway Propagation in a Battery Pack

All-solid-state-battery (ASSB) safety has rarely been studied at the cell scale. The first results underline that safety is improbable and should be investigated further. To the best of our knowledge, the propagation of thermal runaway (TRP) has never been investigated and characterized experimentally at the battery pack scale. A setup was specially designed to contain two thermal runaways and to be representative of a battery pack configuration. Three key steps of TRP were characterized by high-speed X-ray radiography and heat flow measurements: ignition, propagation and ending. Several tests were carried out to assess and compare the TRP risk between a lithium-ion battery (LIB) pack and a reconstituted ASSB (RASSB) pack. TRP in an RASSB pack occurred and was faster and more brutal than that in an LIB pack. The TRP was triggered at 91 ms in an RASSB pack and at 507 ms in a LIB pack. High-speed X-ray radiography highlighted that event propagation was 5 times shorter for an RASSB pack. This study shows that the heat flow measured from the ejecta (hot gases, flames, and incandescent particles) greatly influenced the propagation time of the TRP. This parameter from the reconstituted ASSB trigger cell reached a magnitude 10-fold higher than that of the LIB trigger cell during its thermal runaway. The generated heat flow reached 1828 kW at the peak from RASSB and 176 kW from LIB. Consequently, TRP kinetics is faster for this cell type and can significantly affect pack integrity.