Tensile Separator Film Testing for Electric Vehicle Batteries

Why does a separation film appear in electric vehicle batteries?

The presence of a membrane between the cathode and anode in electric vehicle batteries is called a separator for the purpose of preventing short circuits.
These separators must be able to withstand extreme conditions from the manufacturing process to the environmental conditions.
An important part of Li-ion batteries or other types of liquid electrolyte batteries, the separators between the two terminals in the battery are membranes, which are usually made of polymers and must be mechanically strong enough to withstand the operation of the battery. coil during battery assembly.
The important mechanical properties that the supplier must control are:
- Tensile
- Elongation
- Resistance to puncture.

To ensure the above characteristics, we offer a solution to test the tensile strength of the separator film in electric vehicle batteries according to ASTM D882 standard as follows:
- ASTM D882 outlines the tensile test of thin plastic films, suitable for testing polymeric separator films in batteries. Instron offers products with outstanding accuracy and throughputs suitable for laboratories.
- The test according to this standard requires the preparation of samples with a thickness of less than 1mm, which is carried out on a universal compression machine with constant speed such as the 3400 and 6800 series compressors.

During the test, the specimen is stretched until it breaks. The initial strain rate depends on the maximum elongation of the specimen at break.
An important factor in ASTM D882 testing is the use of proper preload. Thin film test pieces are normally relaxed and unstretched when inserted into the clamp for testing. Preload, easily configurable in Bluehill Universal testing software, eliminates any slack in the sample before data is recorded during testing, ensuring that results are accurate and reproducible again.

Since the samples are polymer thin films, the selection of the clamp is also an important issue to be addressed. For this electric vehicle battery separator membrane test, the pneumatic clamp is an optimal choice, providing a pressure head that helps the clamp hold the sample firmly during the test.

With Extensometers Instron prefers to use non-contact video extensometers, which are the best solution for thin film testing, as clip-on extensometers weigh down the sample, while the knife edges are likely to tear the sample during inspection. Instron's AVE2 video extensometer can measure tension down to one micrometer without the need for physical contact with the specimen.


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