ASTM D1894-14 Coefficient of Friction of Plastic Film

Separator Film Testing for Electric Vehicle Batteries

  

Separator films are used in EV battery production to separate the anode and cathode in lithium-ion and other liquid electrolyte batteries. These films are required in high volumes and are extremely critical to product safety. Because testing standards specific to EV batteries have not yet been established, ASTM D1894 is commonly used as a proxy standard to characterize their frictional properties. The most common material used for separator film is polyolefin, a polymer film that is strong enough to withstand the winding operation during assembly as well as uneven plating of lithium on the anode due to extensive use. Safer and stronger separator material more effectively prevents contact between the anode and cathode, while thinner material helps reduce the weight of each battery and improve energy density. Understanding the frictional properties of this polymer film can help ensure the material is being wound properly during assembly and will behave as expected under extensive use.

When testing thin films to ASTM D1894 it is important to use a test machine with a high data capture rate. Because test events can happen quickly, a machine with a low data capture rate may miss key peaks and troughs in the data, leading to an inaccurate average strength value. Instron’s 6800 series test frames are capable of data capture up to 5 kHz to ensure that all test events are captured. For ASTM D1894 testing we recommend a 6800 series single column frame equipped with a low force (5 – 100 N) 2530 series load cell (depending on the expected frictional forces).

• Instron’s 2530 series load cells can maintain accuracy down to 1/500th of the cell’s capacity when used on a 6800 Series universal testing system. The lowest capacity 2530 series load cell is 5 N, meaning it can maintain 1% accuracy from 0.02 N to 5 N. Forces beneath the lower limits can be measured, but Instron cannot guarantee stated accuracy.

• Instron's Bluehill Universal testing software has advance pre-built methods available for ASTM D1894 to ensure that your test speeds and calculations are compliant.