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 (LiFePO4) 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.
