Crashworthiness Models for Automotive Batteries

Turner, John A.; Kalnaus, Sergiy; Wang, Hsin; Simunovic, Srdjan; Kumar, Abhishek; Gorti, Sarma; Allu, Srikanth · 2019 · ROSA P / United States. Department of Transportation. National Highway Traffic Safety Administration

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Summary

This report addresses the critical safety challenge of internal short circuits and thermal runaway in large-format lithium-ion battery packs used in electric vehicles (EVs). While existing safety standards focus on passive measures, the specific mechanical mechanisms leading to catastrophic failure during crash-induced deformation remain poorly understood. The authors argue that traditional single-cell indentation tests on rigid supports do not accurately replicate the complex stress fields and strain distributions found within multi-cell battery modules. Consequently, the study aims to develop experimental methods and finite element (FE) models that better simulate realistic crash conditions to identify critical deformation thresholds for failure. To achieve this, researchers at Oak Ridge National Laboratory conducted mechanical tests on large-format pouch cells from Ford Focus EV and Nissan Leaf battery packs. They developed a novel experimental setup using a compliant backing made of ballistic clay to simulate the support provided by adjacent cells in a module, contrasting this with tests on rigidly supported 10-cell stacks. Additionally, biaxial deformation tests were performed on battery separators (Celgard 2325 and 2075) to determine critical failure strains. These experimental findings were complemented by FE simulations using LS-DYNA, which modeled the layered structure of battery cells and the anisotropic mechanical properties of separators to predict strain distribution and failure modes. The results demonstrated that the compliant backing setup more accurately reflects the mechanical response of cells within a module compared to rigid support tests. In both the 10-cell stacks and the single-cell-on-clay configurations, internal short circuits were identified by potential drops that coincided with subtle changes in stiffness rather than the significant load drops observed in rigid support tests. The critical indentation displacement for failure was approximately 10 mm for the 10-cell stack and 14.4 mm for the cell on clay. Separator testing revealed that failure occurs via cracks oriented along the machine direction, with critical principal strains of 0.34 for the triple-layer Celgard 2325 and 0.43 for the single-layer Celgard 2075. FE simulations successfully replicated the experimental strain distributions in separators, validating the use of anisotropic material models, though discrepancies in force predictions for full modules highlighted the need for improved electrode material models. The significance of this work lies in its provision of a more realistic framework for evaluating EV battery crashworthiness. By demonstrating that compliant backing setups reduce the severity of thermal runaway events while capturing relevant failure mechanics, the study offers a safer and more accurate alternative to destructive whole-module testing. Furthermore, the identification of specific critical strains for separator failure provides essential data for developing predictive models and design criteria to prevent catastrophic battery failures in future EV applications.

Key finding

Internal short circuits in pouch cells occur at critical displacements of approximately 10 mm in stacked configurations and 14.4 mm in compliant backing setups, driven by separator failure strains of 0.34 to 0.43.

Methodology

lab_experiment

Provenance

The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via bulk_ingest_rosap on 2026-05-23 (6 acquisition events logged).

Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• naturalistic crash near crash