Abstract
Anisotropic mechanical properties were experimentally determined and compared for three types of commercially available Li-ion battery separators: Celgard 2325, Celgard PP2075 dry-processed polymer separators, and DreamWeaver Gold 40 non-woven separator. Significant amount of anisotropy of properties was determined, with the Young's modulus being different by up to a factor of 5 and ultimate strength being different by a factor of 10 between orthogonal directions within a polymer separator layer. Strain rate sensitivity was investigated by applying strain rates ranging from 1⋅10−4 s−1 to 0.1 s−1. Significant strengthening was observed and the strain rate strengthening coefficients were determined for both elastic modulus and yield stress in case of polymer separators. Digital image correlation technique was used to measure and map the strains over the specimen's gage section. Significant strain concentration in bands running perpendicular to the tensile axis was observed in polymer separator samples oriented in transverse direction. Such localized necking allows for extremely high strains close to 300% to develop in the material. The failure mode was remarkably different for all three types of separators which adds additional variable in safe design of Li-ion batteries for prevention of internal short circuits.
Original language | English |
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Pages (from-to) | 255-263 |
Number of pages | 9 |
Journal | Journal of Power Sources |
Volume | 348 |
DOIs | |
State | Published - 2017 |
Funding
This research at Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725, was sponsored by the Vehicle Technologies Program for the Office of Energy Efficiency and Renewable Energy. Rick R. Lowden is acknowledged for his assistance and expertise in setting up the experiments.
Funders | Funder number |
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U.S. Department of Energy | DE-AC05-00OR22725 |
Oak Ridge National Laboratory | |
Office of Energy Efficiency and Renewable Energy |
Keywords
- Lithium-ion
- Mechanical
- Polymer
- Rate sensitivity
- Safety
- Separator