Fractional Thermal Runaway Calorimetry

Advancements in technology have made lithium-ion (Li-ion) batteries an increasingly prevalent energy storage solution in many industries. Li-ion batteries are well known for their high energy density, making them a preferred choice in powering a wide range of applications from small devices, such as wearables and mobile consumer electronics, to large devices, such as backup power supplies. Although Li-ion batteries enjoy high popularity and widespread use, a drawback of this energy storage solution is its potential to undergo thermal runaway, where the battery cell undergoes uncontrolled self-heating and can vent flammable gases, high temperatures, and fire. Active and passive components of thermal management systems in battery-powered consumer electronics are designed to mitigate the effects of thermal runaway events and prevent cell-to-cell propagation. Designing safe products requires an understanding of how a cell or a pack will behave undergoing thermal runaway, including critical data such as total energy yielded and rate of energy generation, as well as venting patterns and directions. Details such as thermal runaway energy fractions associated with cell casing and vent gas and ejecta can be used to inform and optimize the thermal design of consumer electronics devices and wearables. One such technology that has been developed for this very purpose is the National Aeronautics and Space Administration (NASA) Fractional Thermal Runaway Calorimeter (FTRC). In this work, the FTRC technology is reviewed along with examples of experimental data sets collected using this methodology.