Session: 08-05-06: Energy-Related Multidisciplinary VI

Paper Number: 149646

149646 - Validation of the Mechanical Behaviour of Lithium-Ion Battery Separators Under Different Loading Conditions With Openradioss 

The increasing need to reduce the climate-damaging exhaust gases in the automotive industry leads to an increasing usage of electric powered drive systems using Lithium-ion (Li-ion) batteries. For the safety and crashworthiness investigations, a deeper understanding of the mechanical behavior under high and dynamic loads is needed. In order to prevent internal short circuits and thermal runaways within a Li-ion battery, the separator plays a crucial role. The mechanical properties of a dry-processed separators (polyethylene (PE) by Boston Powers and polypropylene (PP) by Celgard H2010 Trilayer and polypropylene (PP) by Celgard Q20S1HX Ceramic-Coated Trilayer) are investigated in terms of deformation and failure limits. The focus is set on the investigation of the anisotropic, and viscose mechanical behavior of these materials. The uniaxial tests were carried out along the machine direction (MD), transverse direction (TD), and diagonal direction (DD). Based on uniaxial tensile tests with local strain measurement, a novel failure criterion for finite element analysis (FEA), using the explicit FEA solver OpenRadioss and Altair Radioss, has been developed to predict the limits of high mechanical loads with respect to triaxiality, large plastic strain and orthotropy. The proposed failure model is developed as an additional failure criterion and can be combined with other constitutive material laws. It considers the state of stress (triaxiality), large plastic strains and orthotropy. A regularization table can also be used. Finally, a simulation model of a PE separator was developed combining the novel failure criterion with Hill’s yield surface and a Swift–Voce and G'Sell hardening rule. A FE simulation model of the separator material is performed, using the results of different tensile tests conducted at three different velocities, 0.1 mm/s, 1.0 mm/s and 10.0 mm/s and different orientations of the specimen. The purpose is to predict the anisotropic, rate-dependent stiffness behavior of separator materials in order to improve FE simulations of the mechanical behavior of batteries and therefore reduce the development time of electrically powered vehicles and consumer goods. In order to generate a state of in-plane biaxial tension, a pneumatic bulge test setup was prioritized over the commonly performed punch test in an attempt to eliminate the effects of contact friction. The biaxial flow stress–strain behavior of the membranes was deduced via the Panknin–Kruglov method coupled with a 3D Digital Image Correlation (DIC) technique. Derived from experimentally calibrated constitutive models, the finite element model was validated using the explicit solver OpenRadioss. The model succeeded in predicting anisotropic, visco-elastic orthotropic and visco-plastic orthotropic stiffness behavior up to failure. The mechanical integrity of commercially available Li-ion battery separators was investigated under uniaxial and biaxial loading conditions. As conclusions, the investigated separators displaced a notable anisotropy. The ceramic coating was found to negatively affect the mechanical performance of the trilayer microporous separator, compromising its strength and stretchability, while preserving its failure mode. The resilience of H2010 mitigates the risk of internal short circuits between electrodes, thereby improving battery safety and longevity. While surface coating polyolefin separators with ceramic material (Q20S1HX) provides the benefits of enhanced wettability and thermal stability, it appears to compromise, to a degree, the mechanical performance. However, both separators demonstrated a comparable failure mode in the form of thinning and semi-transparent zones running along the machine direction, as confirmed via DIC analysis. Lastly, a preliminary finite element model of the biaxial tests was developed in OpenRadioss. The numerical model was able to capture the pressure–displacement behavior of the separators fairly well concerning the experimental findings. Advanced numerical modeling is ongoing to better simulate the failure behavior of entire batteries.

Presenting Author: Marian Bulla Altair Inc.

Presenting Author Biography: Career – No more than 200 words summarizing past achievements and present responsibilities:
1992-1997: Engineering studies at university of Iserlohn (Germany)
1998-2000: Fraunhofer Institute for Laser-Technique ILT Aachen
2000-2003: Testing- and Simulation Engineer at Research Society for Automotive industry Aachen
Since 2003: Lecturer at the University of applied sciences in Aachen
2003-2005: Simulation Engineer at PuZ Engineering Cologne (Germany)
2005-2008: Simulation Engineer at Imperia GmbH Aachen (Germany)
Since 2008: Product specialist for Crash&Safety at ALTAIR Engineering
Since 2014: Member at Development and Validation Team
2016-2019: Research fellow at MIT (Massachusetts Institute of Technology)
2017-2021: Program Manager – Material Data at ALTAIR Engineering
Since 2021: Director – OpenRadioss Community at ALTAIR Engineering

ASME Membership Grade:

Honors received – awards, citations, etc. Please include sources and dates:
https://scholar.google.de/citations?view_op=list_works&hl=de&user=SXR8L5QAAAAJ

ASME activities: 2 presentations at the IMECE 2023 conference in New Orleans

Membership in other professional and scientific societies: DACHEMA GAK (expert network for chemical engineering and biotechnology)

Authors:

Marian Bulla Altair Inc.
Stefan Kolling TH Mittelhessen University of Applied Sciences
Elham Sahraei Temple University
Sahand Shamchi TH Mittelhessen University of Applied Sciences