Experimental Investigation of the Thermal Runaway Propagation Characteristics and Thermal Failure Prediction Parameters of Six-Cell Lithium-Ion Battery Modules

Abstract

Efforts to meet regulations ensuring the safety of lithium-ion battery (LIB) modules in electric vehicles are currently limited in their ability to provide sufficient safe escape times in the event of thermal runaway (TR). Thermal runaway occurs when the heat generation of a battery module exceeds its heat removal capacity, leading to a rapid increase in temperature and uncontrolled heat release. To address this issue, this study focuses on evaluating the cascading thermal failure characteristics of six-cell LIB modules under an air environment in an experimental combustion chamber. Sensors are strategically placed at advantageous locations to capture changes in various characteristic parameters, including LIB temperature, module voltage, module mass, and the concentrations of venting gases in the combustion chamber. Analysis of the variations in these characteristic parameters over time aims to identify effective signals that can predict thermal failure conditions with a maximum warning time. The results demonstrate that monitoring LIB temperature provides the shortest advance warning of TR propagation within the module. However, module voltage measurements offer a warning that is approximately 2% earlier on average. On the other hand, measurements of the module mass and concentrations of venting gases in the combustion chamber allow for warnings of thermal failure that are, on average, approximately 2 min earlier than those based solely on LIB temperature. These findings can serve as guidance for improving the safety of LIBs, enhancing the reliability of fault detection systems, and exceeding the safe escape time requirements set by current global regulations.