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Battery Diaphragm Permeability Test August 17,2022.
The main function of the diaphragm is to separate the positive and negative electrode pieces to prevent short circuit of the battery, but also to ensure the normal passage of ions during charging and discharging. So, what is the impact of diaphragm permeability on the performance of lithium batteries?
(1) the impact on the voltage
Diaphragm thickness is thinner, the lithium ion migration channel is shorter, the polarization phenomenon will be smaller, and the low-temperature voltage platform of lithium batteries is relatively high. In addition, the diaphragm aperture will accelerate the self-discharge rate of lithium batteries, thereby reducing the voltage consistency of the battery. Diaphragm pore size is generally in the 0.03-0.12um.
(2) the impact on safety
Thickness of the diaphragm in the lithium battery by the impact of foreign objects, to better protect the internal isolation of the positive and negative electrodes, so that the thicker diaphragm also means that the battery is safer. The thickness uniformity of the diaphragm includes longitudinal thickness uniformity and lateral thickness uniformity, of which lateral thickness uniformity is particularly important, generally required to control within ± 1 micron.
Since the temperature of lithium batteries rises during continuous use, the diaphragm generally has an additional feature of thermal shutdown. When the internal resistance of the lithium battery increases by three orders of magnitude, the thermal shutdown function of the diaphragm will be enabled.
(3) The effect on the internal resistance
The permeability of the diaphragm is proportional to the internal resistance of the lithium battery, i.e., the higher the permeability of the diaphragm, the higher the internal resistance of the battery will be.

In addition, whether the diaphragm can be completely infiltrated by the electrolyte will also affect the internal resistance of the battery. The wettability of the electrolyte is related to the diaphragm material itself and its internal microstructure. Better wettability is conducive to improving the affinity between the diaphragm and the electrolyte, expanding the contact surface between the diaphragm and the electrolyte, thus increasing the ionic conductivity and improving the charge and discharge performance and capacity of the battery.

Battery diaphragm permeability tester N600


Principle of operation Gehrig's method: Determination of the time taken to pass 100 ml of gas at a constant differential pressure of 1.23 kPa. Schauberger method: The gas flow through the specimen is measured by the test volume at a constant differential pressure of 1.00 kPa ± 0.01 kPa or 2.50 ± 0.01 kPa, and a suitable test duration is selected. Bengtsson method: The air flow rate through the test surface is recorded after 5 s of clamping at a constant differential pressure of 1.47 kPa.

Comply with the standard SJ_T 10171-2016 General test method for basic performance of alkaline battery separator (permeability part) GB/T 458-2008 Determination of permeability of paper and cardboard GB/T 36363-2018 Polyolefin separator for lithium-ion batteries

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