Effect of Thermal Abuse Conditions on Thermal Runaway of NCA 18650 Cylindrical Lithium-Ion Battery

Abstract

In energy storage systems and electric vehicles utilizing lithium-ion batteries, an internal short circuit or a thermal runaway (TR) may result in fire-related accidents. Particularly, under non-oxygenated conditions, a fire can spread as a result of TR. In this study, a TR experiment was performed on a nickel–cobalt–aluminum 18650 cylindrical lithium-ion battery via thermal conduction. The time required to attain TR (temperature range: 250–500 °C) was drastically reduced from approximately 1200 s to 1 s. The chemical reaction rate of thermal runaway was classified according to temperature into two global mechanisms and applied to the Arrhenius equation, thereby yielding a correlation between plate temperature (TP) and time difference of TR times ∆t (i.e., t1−t0 or t2−t0). As a result, activation energy for the overall reaction of the TR was estimated to be 39.9 kJ/mol. Furthermore, the safety guarantee time mandated by the safety regulation for vehicle batteries is 5 min; an analysis of the experiment results reveals that the following conditions can be satisfied: TP = 308.4 °C, Δtt1−t0 = 5 min; TP = 326.2 °C, Δtt2−t0 = 5 min. The experiment results offer a scientific basis for predicting the time of occurrence of TR and establishing safety standards.