What is the testing principle of 18650 lithium 3.7 battery separator technology? What are its detection methods?

　　18650 lithium 3.7 battery separator technology testing principle

　　The principle of online detection of diaphragm thickness is mainly to convert the attenuation of rays after passing through the diaphragm into diaphragm thickness. This means that the accuracy and stability of the detection must be ensured during the detection process.

　　As the energy density of lithium batteries increases, the separator of the battery becomes thinner and thinner, and the measurement accuracy is also required to be higher and higher. Generally, enterprises use micrometers for measurement, and there are also GB/T6672-2001 Plastic Film and Sheet Thickness Determination_Mechanical Measurement Method. A standard measurement method, there are also corresponding international standards for measurement, but these standards are not formulated for diaphragms, so there are problems such as wide test range and low accuracy. Therefore, companies that require accuracy generally use precision thickness gauges for measurement.

　　What are the testing methods for 18650 lithium 3.7 battery separator technology?

　　1.Thickness

　　There are two main online control technologies for 18650 lithium 3.7 battery separator thickness, one is MD (vertical) control and CD (transverse) control; the other is separator online machine vision inspection technology. The so-called MD control and CD control refer to the closed-loop thickness control in the MD direction by controlling the feeding screw speed or traction speed; and the data measurement through the scanning frame, and finally the closed-loop data control in the CD direction.

　　2. Curvature

　　Some companies also call it camber, which refers to the arc produced after slitting the 18650 lithium 3.7 battery separator. When the arc is obvious, it will cause the laminations to be uneven, and create a vortex during winding, causing the pole pieces to be exposed and cause short circuits. The test method is to lay the diaphragm strip flat on the table and compare the parallelism with the edge of the steel ruler to get the curvature of the diaphragm.

　　3. Breathability

　　The time required for a certain volume of air to pass through the diaphragm under certain conditions is also called the Gurley value. Its size has a certain impact on the performance of lithium batteries. The ASTM test method is generally used.

　　4.Porosity

　　The volume of the void accounts for the proportion of the entire volume. The test methods include the liquid absorption calculation method and the test method. The liquid absorption calculation method is to immerse the 18650 lithium 3.7 battery separator in a known solvent, and calculate the amount of the separator occupied by the liquid by measuring the mass difference before and after the separator is infiltrated. Void volume, mercury intrusion testing method uses external force to apply pressure on the diaphragm to press mercury into the pores of the diaphragm, and then calculates the porosity of the diaphragm by measuring the volume of mercury pressed into the diaphragm. After multiple measurements, the average value is taken.

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