The GB/T 36363-2018 standard has developed a systematic testing plan for the physical properties of polyolefin separators used in lithium-ion batteries, covering core indicators such as thickness, mechanical properties, breathability, thermal stability, and puncture strength. The following is an introduction from four dimensions: testing items, methods, instruments, and significance:

1、 Testing items and core requirements

1. thickness detection

• requirementThickness deviation should be controlled within ± 1 μ m, and lateral uniformity is particularly important.

• meaningThickness uniformity directly affects electrolyte wettability, ion transport efficiency, and battery assembly consistency. Thin areas can easily cause local short circuits, while thick areas may sacrifice energy density.

2. Mechanical performance testing

• requirementPuncture strength ≥ 300gf (3N) to prevent lithium dendrites from piercing the diaphragm and causing short circuits.

• meaningSimulate the scenario of electrode particles or lithium dendrites piercing the membrane to evaluate its puncture resistance.

• requirementDry process diaphragm tensile strength ≥ 80MPa, wet process diaphragm ≥ 100MPa (longitudinal/transverse); The elongation at break is ≤ 30% in the longitudinal direction and ≤ 80% in the transverse direction.

• meaningEvaluate the tensile resistance of the diaphragm during assembly and use to avoid breakage caused by mechanical stress.

• Tensile strength and elongation at break：

• puncture strength：

3. Breathability testing

• requirementThe air permeability (Gurley value) should be within the range of 200-500s/100mL, balancing ion conductivity and mechanical strength.

• meaningLow breathability may affect mechanical strength, while high breathability can hinder ion transport and reduce battery charging and discharging efficiency.

2、 Testing methods and operating procedures

1. thickness detection

• Sampling rulesSelect 3 test points equidistant along the transverse direction of the diaphragm as a group, and test a group every 200mm longitudinally, for a total of 5 groups (15 points).

• measurement conditionsUsing contact mechanical measurement method, with a pressure of 17.5 ± 1kPa and a contact area of 50mm ², to avoid material deformation interference.

• data processingAutomatically calculate the average valuebigGenerate a thickness distribution map based on small values and deviations.

2. Tensile strength and elongation at break testing

• sample preparationCut a type 2 specimen with a width of 15mm and a length of 150mm, and the fixture spacing is 100mm.

• test conditionsSpeed 250mm/min, temperature 23 ± 2 ℃, humidity 50 ± 10% RH.

• data collectionRecord the force displacement curve and automatically calculate the tensile strength and elongation at break.

3. Breathability testing

• Test PrincipleMeasure the time for 100mL of air to pass through a 6.45cm ² diaphragm at a pressure of 1.21kPa.

• operating procedureCut a 100mm × 100mm sample, seal it in the testing chamber, activate the pneumatic clamping device, and automatically record the average value of three tests.

4. Puncture intensity testing

• Sample fixationSpread the diaphragm flat in the fixture of the tensile testing machine, with an inner diameter of 10mm.

• Puncture testPuncture with a 1.0mm ball needle at a speed of 100mm/min and record the force value.

3、 Selection of Testing Instruments and Equipment

1. thickness detection：

• instrumentHigh precision thickness gauge (such as Jinan Zhongce)THK-02 thickness gauge）The resolution is 0.1 μ m.

• advantageStrictly designed according to the standard contact area and measurement pressure, the measuring head automatically lifts and lowers, effectively avoiding system errors caused by human factors. The measuring head automatically lifts and lowers, effectively avoiding system errors caused by human factors.

  
  

2. Tensile strength and elongation at break testing：

• instrumentIntelligent electronic tensile testing machine (such as Jinan Zhongce)TST-02H Intelligent Tensile Testing Machine）Using a 0.1 level precision force sensor, the displacement resolution reaches 0.1mm.

• advantageSupport multi-mode testing such as stretching, peeling, and puncture to meet diverse testing needs.

  
  

3. Breathability testing：

• instrumentBreathability tester (such as Zhongce Electromechanical)BTY-G3 Battery Diaphragm Breathability Tester）Using Gray's method and Wang Yan's method, high-precision electronic airflow and pressure sensors ensure the accuracy of test data, with pressure accuracy better than 0.01kPa.

• advantage：Three independent testing chambers can simultaneously test three identical or different samples.

  
  

  
  

4. Puncture intensity testing：

• instrumentBattery separator puncture force tester (such as Jinan Zhongce)MCT-08 Battery Diaphragm Puncture Force Tester）Equipped with a 0.01N resolution sensor, it supports automatic calculation of puncture intensity.

• advantageThe needle body diameter is 1mm, and the spherical diameter of the needle tip is 0.5mm. It is easy to operate and has accurate data, suitable for research and quality inspection scenarios.

4、 Significance of Detection and Industry Impact

The GB/T 36363-2018 standard quantifies diaphragm performance to micrometer level accuracy through systematic testing methods, providing a unified technical benchmark for the industry. The application of high-precision detection instruments not only reduces research and quality control costs, but also accelerates the marketization process of high-quality products.