It represents combined in-plane biaxial tension and out-of-plane compression. A punch test with a small radius punch head is one of the standard abuse tests for lithium-ion battery separators. It is performed with a punch of 3.2 mm in diameter according to ASTM F1306-90, and usually referred to as a puncture test 25.
Biaxial punch tests were performed with punch sizes of 1/8 to 1 inch. The punch heads were machined from teflon bulk to minimize the contact friction. The specimens were cut by a hammer driven hole punch with a diameter of 45 mm. The sample test diameter (see Figure A1 b) was 32 mm. Each type of separator was tested with four different punch heads.
In punch test of the whole battery cells, due to the friction from cathode and anode particles, the separator is mostly expected to fail in Mode A, and not to reach Mode B. With the start of thinning and appearance of transparent section, friction would lead to instant localization.
Scientific Reports 6, Article number: 32578 (2016) Cite this article Separator integrity is an important factor in preventing internal short circuit in lithium-ion batteries.
Sahraei, E., Bosco, E., Dixon, B. & Lai, B. Microscale failure mechanisms leading to internal short circuit in Li-ion batteries under complex loading scenarios. J. Power Sources 319, 56–65 (2016). Feng, X. et al. Characterization of penetration induced thermal runaway propagation process within a large format lithium ion battery module. J.
While peak force and displacements to failure usually followed a linear trend with punch size, they observed that in a conical punch (smallest punch) test of a large pouch cell, the peak values were much beyond what was expected for that punch size.