Battery Thermal Runaway Preventive Time Delay Strategy Using Different Melting Point Phase Change Materials

Abstract

<div>The production of alternative clean energy vehicles provides a sustainable solution for the transportation industry. An effective battery cooling system is required for the safe operation of electric vehicles throughout their lifetime. However, in the pursuit of this technological change, issues of battery overheating leading to thermal runaways (TRs) are seen as major concerns. For example, lithium (Li)-ion batteries of electric vehicles can lose thermal stability owing to electrochemical damage due to overheating of the core. In this study, we look at how a different melting point phase change material (PCM) can be used to delay the TR trigger point of a high-energy density lithium-iron phosphate (LiFePO<sub>4</sub>) chemistry 86 Amp-hour (Ah) battery. The battery is investigated under thermal abuse conditions by wrapping heater foil and operating it at 500-W constant heat conditions until the battery runs in an abuse scenario. A comparative time delay methodology is developed to understand the TR trigger points under a timescale factor for different ambient conditions such as 25°C, 35°C, and 45°C. In the present study, two different types of PCMs are selected, that is, paraffin wax which melts at 45°C and Organic Axiotherm (ATP-78) which melts at 78°C. Modeling results suggest that the TR trigger point and peak onset temperature are greatly influenced by the battery operating temperature. The concluded results indicate that by submerging the battery in PCM, the TR trigger point can be greatly delayed, providing additional time for the driver and passenger to evacuate the vehicle. However, the present findings also reflect that fire propagation cannot be completely extinguished due to the volatile hydrocarbon content in the PCM. Hence from this study, it is recommended that whenever using a PCM-equipped passive cooling strategy, thermal insulation should be provided at the wall of the PCM to delay the TR propagation from one battery to another at pack-level configuration.</div>