Abstract
A physical phenomenon encompassing the transitions of open circuit voltage (OCV), internal resistance, temperature, pressure, and auto-ignition near crucial point is identified. This study has demonstrated the distinctive feature to be very similar among pouch NMC532, pouch LCO and cylindrical 21700 NCA batteries. For the pouch NMC battery, the observed transient sequence less than 1.07 s and in the temperature range of 0.9 ℃ is ranked as follow: pressure transition (TP) → gas eruption associated with ejecta (Teruption) → resistance/OCV change (TR3/TV2) → auto-ignition (Tig) associated with a blue-purple flame. A unique Tcr has been captured earlier or later than pressure behaviors related to TP, Teruption, and Pcr. These results provide a new perspective for the understanding of intrinsic safety design and the mechanism of thermal runaway.