A cost-effective alternative to accelerating rate calorimetry: Analyzing thermal runaways of lithium-ion batteries through thermocouples

Abstract

In order to facilitate safety of heavy-duty batteries, approaches for studying thermal runaway (TR) need to be developed. So far, these have relied on accelerating rate calorimetry as a standard technique. This method, however, is costly, generally has size limitations, and is therefore of limited use for large format batteries. In this study, we examined the TR behavior of battery cells through a thermal propagation test at module level employing 157 Ah battery cells, using simple thermocouples. This constitutes one of the largest prismatic cell format analyzed to date, while the utilization of thermocouples enables a cost-effective method to study its TR. Parameters such as TR onset temperature, maximum temperature, heat release, and trigger time of the cells were comprehensively evaluated and compared, using this method. An onset temperature for TR at around 144 °C and a maximum temperature from 757 °C to 863 °C were observed. Heat release was estimated as 1.59 MJ per battery cell, deviating within ∼1 % compared to nail penetration tests. Moreover, six distinct stages during TR could be observed, in accordance with literature. This shows that the thermal propagation test using thermocouples is able to align well with other methods such as accelerating rate calorimetry, but is considerably easier to employ.