Abstract
Safe performance of advanced Li-ion batteries relies on integrity of the separator membrane which prevents contact between electrodes of opposite polarity. Current work provides detailed study of mechanical behavior of such membrane. Temperature and strain rate sensitivity of the triple-layer polypropylene (PP)/polyethylene (PE)/polypropylene (PP) porous separator for Li-ion batteries was studied experimentally under controlled temperatures of up to 120° (393 K), and strain rates (from 1⋅10−4s−1 to 0.1s−1). Digital image correlation was used to study strain localization in separator under load. The results show significant dependence of mechanical properties on temperature, with the yield stress decreasing by 30% and elastic modulus decreasing by a factor of two when the temperature is increased from 20 °C to 50 °C. The strain rate strengthening also decreased with higher temperatures while the temperature softening remained independent of the applied strain rate. Application of temperature creates long lasting changes in mechanical behavior of separator as was revealed by performing experiments after the annealing. Such delayed effect of temperature application appears to have directional dependence. The results demonstrate complex behavior of polymer separator which needs to be considered in proper safety assessments of Li-ion batteries.
Original language | English |
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Pages (from-to) | 73-80 |
Number of pages | 8 |
Journal | Extreme Mechanics Letters |
Volume | 20 |
DOIs | |
State | Published - Apr 2018 |
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 and by the National Highway Traffic Safety Administration. Rick R. Lowden is acknowledged for his assistance and expertise in setting up the experiments.
Keywords
- Energy storage
- Li-ion
- Mechanical
- Safety
- Separator