Berlin 2024 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 40: Focus Session: Battery Materials – Experimental Characterisation and Safety Testing (joint session KFM/MM)

MM 40.2: Talk

Wednesday, March 20, 2024, 15:30–15:50, EMH 225

Temperature dependency of the heat capacity of Lithium-ion batteries during Heat-Wait-Seek Tests in Accelerating Rate Calorimetry — •Philipp Finster, Hans J. Seifert, and Carlos Ziebert — Karlsruhe Institute of Technology (KIT), Institute of Applied Materials - Applied Materials Physics (IAM-AWP), Eggenstein-Leopoldshafen, Germany)

The Heat-Wait-Seek test in Accelerating Rate Calorimeter (ARC) can be used to estimate the safety performance of Lithium-ion cells by extracting parameters such as critical temperatures or generated heat. To calculate the generated heat, it is essential to know the heat capacity of the cell as a function of temperature.

In this study we show an accurate way to calculate the heat capacity of the cell, based on its individual components with respect to temperature. Additionally, we will discuss time dependency of the heat capacity, for instance while melting of the separator or venting. Using this dependence of temperature results in a significant difference in the calculated heat capacity of about 15 % in the temperature range from 298 K to 498 K. In this work the approach is applied to commercial type 21700 cells. The cells were measured in an ES-ARC from Thermal Hazard Technology, UK. The generated heat was compared for either fresh cells or cells after cyclic aging.

With this approach the generated heat in abuse tests can be predicted more accurately to simulate the propagation of heat during a single cell failure in a pack or to calculate the appropriate thickness of a heat barrier for safer battery packs.

Keywords: calorimetry; Accelerating Rate Calorimetry; Lithium-ion battery; heat capacity; battery safety