Electrical Interactions in Lithium-Ion Battery Packs during Thermal Runaway

Unofficial AI-generated summary based on the public title and abstract. Not an official translation.

🔬研究者:Battery safety researchers can use the experimental methodology and model to further investigate electrical failure propagation.

🏢実務担当者:EV battery pack designers should incorporate electrical interactions into their safety simulations and testing protocols.

With the growing adoption of electric vehicles, lithium-ion batteries have become a central technology for the decarbonization of the transport sector [1]. Sustaining this development requires continuous advances in battery system performance, cost-effectiveness, and, above all, safety. While compromises between performance and cost are often unavoidable [2], safety is non-negotiable due to stringent regulatory requirements and its essential role in vehicle homologation [3, 4]. In this context, the prevention of thermal propagation in lithium-ion battery packs is a key safety requirement for electric vehicles [5, 6]. While pack-level mitigation concepts mainly target thermal and mechanical coupling [7], the electrical interaction between cells during thermal runaway has received far less attention. In particular, the influence of parallel cell interconnections on current redistribution and the resulting Joule heat generation under abusive conditions remains insufficiently understood. This work investigates the electrical response of an automotive-style battery pack containing cylindrical 21700 cells with nickel-rich oxide cathodes during the thermal runaway of a single cell under representative pack integration conditions. For this purpose, pack-level propagation tests (Figure 1a–c), dedicated single-cell nail-penetration experiments, and post-mortem X-ray computed tomography were carried out, while a simplified electrical pack model was implemented to analyze single-cell behavior within the interconnected battery pack. The pack experiments show that thermal runaway of one cell triggers substantial internally driven short-circuit currents that redistribute through the parallel network. The resulting voltage response demonstrates that this redistribution can locally overcharge cells in series-connected modules, causing transient cell voltages to significantly exceed the normal operating window. These observations indicate that pack topology alone can create additional electrical loading during a cell failure and thus promote further damage beyond the initial thermal event. Subsequent single-cell abuse tests constrain the internal short-circuit resistance of the trigger cell to approximately 5–300 mΩ, implying a wide range of possible short-circuit currents and pack-level electrical stresses. Post-mortem computed tomography further identifies the cell-cap sealing region as a potential weak point for low-ohmic internal shorts (Figure 1d,e). This finding highlights the relevance of cell design and manufacturing quality for electrically driven failure severity. The simplified electrical model reproduces the experimentally observed redistribution trends and provides insight into the governing parameters of the pack response. In particular, the simulations show that very low short-circuit resistances lead to extremely high short-circuit currents and pronounced overcharge of neighboring cells. In addition, the location of the failing cell within the pack influences the magnitude of the induced voltage disturbance. Thus, the worst-case electrical conditions at pack level are jointly determined by the internal short-circuit resistance and the spatial position of the failing cell. Overall, the results demonstrate that battery safety assessment and pack design must explicitly account for electrical effects during thermal runaway, including inter-cell current transfer, topology-dependent discharge, localized overcharge, and associated Joule heating. Under unfavorable combinations of short-circuit resistance, cell location, and pack topology, electrically induced overcharge may become an additional heat source that can contribute to thermal propagation. The presented methodology provides an experimentally grounded basis for identifying electrically critical pack configurations and for improving the design of robust battery systems for automotive applications. References [1] Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg, Data Service Renewable Energies - Global EV registrations. [2] Schmuch, R.; Wagner, R.; Hörpel, G.; Placke, T.; Winter, M., Performance and cost of materials for lithium-based rechargeable automotive batteries. Nature Energy 2018, 3, (4), 267-278. [3] Kampker, A.; Heimes, H.; Frieges, M.; Kisseler, N., Battery Testing in Accordance with UN Regulation 100 REV. 3. 2024 . [4] Lin, C.; Burggräf, P.; Liu, L.; Adlon, T.; Mueller, K.; Beyer, M.; Xu, T.; Kammerer, V.; Hu, J.; Liu, S.; Wang, F., “Deep-Dive analysis of the latest Lithium-Ion battery safety testing standards and regulations in Germany and China”. Renewable and Sustainable Energy Reviews 2023, 173, 113077. [5] Nationals Standard of the People's Republic of China (GB), GB38031-2025: Electric Vehicles Traction Battery Safety requirements 2025 , Issued by: State Administration for Market Regulation-National Standardization Administration. [6] United Nations, Addendum 99: Regulation no. 100-revision 3: Uniform provisions concerning the approval of vehicles with regard to specific requirements for the electric power train. 2022 , Issued by: United Nations. [7] Wang, Q.; Mao, B.; Stoliarov, S. I.; Sun, J., A review of lithium ion battery failure mechanisms and fire prevention strategies. Progress in Energy and Combustion Science 2019, 73, 95-131. Figure 1

• semanticscholar https://doi.org/10.1149/ma2026-0172880mtgabsfirst seen 2026-07-20 05:14:13