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Mechanical Testing of Separator Materials for Lithium-ion Batteries

Latest updated: Dec 14, 2023

Mechanical Testing of Separator Materials for Lithium-ion Batteries


The separator is a critical component of lithium-ion batteries, playing a role in isolating electrons while allowing the passage of ions. Throughout the manufacturing process of lithium-ion batteries, including winding, stacking, assembly, and repeated applications in real-life scenarios, the separator must possess certain mechanical strength and durability. This is crucial to prevent damage caused by physical actions. Therefore, a series of mechanical tests is required when applying separators to batteries.

 

1. Tensile Test:

A certain level of mechanical strength ensures that the separator does not rupture under battery deformation conditions, reducing the risk of battery short circuits. This enhances the yield, improves the safety performance of the battery, and extends its service life. Typically, transverse and longitudinal tensile tests are conducted according to standards such as GB/T 1040.3, ISO 527-3, and ASTM D882 to obtain tensile strength and elongation at break results, meeting research and quality control requirements.

 

2. Puncture Test:

Due to the pressure exerted by dendrites formed during the charging and discharging process, the separator must resist dendritic penetration to avoid internal short circuits in the battery, ensuring battery lifespan and safety. For this application, standards such as GB/T 36363, EN 14477, and ASTM F1306 are typically referenced to test and obtain puncture strength. It is crucial to ensure proper sample tension and alignment of the load chain.

 

3. Friction Test:

During the battery manufacturing process, there is mechanical loading and interaction between the separator and the electrode. Excessive mechanical stress and friction can cause damage and detachment of the electrode's active material. Therefore, friction between the separator and the electrode is measured to avoid adverse effects on the electrode and the battery.

 

4. Impact Test:

Resistance to puncture in impact events is a crucial mechanical property of the separator and can be used to assess and select materials with optimal performance. According to standards such as ASTM D3763, ISO 6603, or UL2591, tests can be conducted using Instron's 9450 falling dart impact equipment. This not only provides data on puncture resistance but also offers information on the maximum force and deformation that the material can withstand.




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