A Cost-Effective Alternative to Accelerated Rate Calorimetry: Analyzing Thermal Runaways of Li-Ion Battery Through Thermocouples

Abstract

To facilitate electrification of heavy-duty vehicles, large format batteries with high energy densities is generally desired. The increasing application of such batteries has caused safety concerns regarding possible thermal runaway (TR). In order to facilitate the safety of heavy-duty batteries, approaches for studying TR need to be developed. So far, these have relied on accelerated rate calorimetry (ARC) as a standard technique. This method, however, is costly, generally has size limitations, and is therefore of limited use. In this study, we examined the TR behavior in a thermal propagation test employing 157 Ah battery cells, using simple thermocouples. Parameters such as onset temperature, maximum temperature, heat release, and trigger time were comprehensively evaluated and compared. Using this method, an onset temperature for TR at around 144 °C could be determined, and the maximum temperature from 757 °C to 863 °C through propagation. Heat release was evaluated as 1.59 MJ per battery cell, deviating within 1% compared to nail penetration tests using cells of the same specification. 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 with ARC measurements, but considerably easier to employ.

Keywords: lithium-ion battery, battery safety, thermal runaway