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Technical requirements for lithium battery diaphragm

Technical requirements for lithium battery diaphragmDetermining the main indicator of lithium battery diaphragm has the thickness, mechanical properties, porosity, gas permeability, aperture size, thermal performance, and self-closing performance. The thinner the diaphragm, the smaller the resistance encountered when the solvate lithium ion is passed, the better the ion conductivity. The lower the impedance, but the diaphragm is too thin, and the oil absorbing capacity and electron insulation are lowered, and the performance of the battery can have an adverse effect. At present, the thickness of the diaphragm actually used is usually 25 ~ 35um.

The mechanical properties of the lithium battery on the diaphragm also have a high requirements, and the separator prepared by the single-axis stretching has an anisotropy in mechanical properties, and the intensity in the tensile direction is approximately 50 N, while the intensity of the vertical stretch direction is only 5n. . The double-axis stretching the diaphragm is substantially consistent in both directions. The multilayer diaphragm is uniform in different directions, making it preferred to serve as a lithium battery diaphragm.

The porosity of the diaphragm can reduce the resistance of the diaphragm on the lithium ion migration, the smaller the porosity, the smaller the curvature of the hole, the better the holes, the stronger the penetration ability of the lithium ion, but the holes will increase The mechanical properties of the material and the decrease in electron insulation, and even the active substance of the mountain is currently produced by the diaphragm. Therefore, most lithium battery diaphragms have a porosity between 4% to 5%.

The size of the aperture is closely related to the porosity. The aperture of the commercializing diaphragm is typically between 0.03 to 0. 12ua, and the aperture distribution is narrow, the aperture size is uniform, and the maximum aperture and the average aperture distribution are not more than 0,011um.

The gas permeability is also physical quantity related to ion migration properties. It is determined by a variety of factors such as the thickness of the membrane, aperture, aperture size, aperture distribution. The smaller thickness of the same material, the smaller the thickness, the more porosity, the higher the pore size, the higher the aperture of the aperture distribution, the higher the gas permeability of the material.

For diaphragm materials for lithium batteries and lithium batteries, hot melt is particularly important performance indicators because it is an important guarantee for battery safety. Due to abuse, the lithium battery is oxidation, the temperature of the electrolyte, the temperature of the battery is rapidly increased, and has become the safety of lithium batteries. To eliminate this hidden danger, the diaphragm must be able to melt the microves at the required temperature, become a non-porous ion insulating layer, to interrupted the battery, preventing the battery due to the continuous increase of the temperature, even exploding, this is Self-closed phenomenon of diaphragm.

The self-closing temperature of the polypropylene separator is about 170 ¡ã C, and the self-retained temperature of the polyethylene separator is 130-140 ¡ã C, and the self-closing temperature of the polypropylene and polyethylene multilayer composite diaphragm in recent years is 80-120 ¡ã C. between. Its strength and safety are better than the single layer film, and the impedance is high when closed, so that the lithium battery is safer. However, the self-closed temperature is too low, the battery is easy to lose performance and scrapp  Recommend: LiFePO4 Battery Manufacturer Energy storage battery Manufacturer Integrated machine energy storage battery series Manufacturer Lead lithium battery Manufacturer Outdoor Backup Battery Manufacturer Portable outdoor power supply Manufacturer Power battery Manufacturer Powerwall LiFePO4 Battery Manufacturer Battery rack Manufacturers Telecom LiFePO4 Battery Manufacturer Wall mounted battery storage Manufacturer China Lifepo4 Battery