What are the important raw materials for processing lithium battery separators?

①Polyethylene terephthalate Polyethylene terephthalate (PET) is a material with excellent mechanical properties, thermodynamic properties, and electrical insulation properties. The most representative product of PET separators is a composite membrane coated with ceramic particles and developed by Degussa in Germany. It exhibits excellent heat resistance and the closed cell temperature is as high as 220°C. The melting point of the electrospun PET membrane is much higher than that of the PE film, at 255℃, the maximum tensile strength is 12Mpa, the porosity reaches 89%, and the liquid absorption rate reaches 500%, which is much higher than the Celgard membrane on the market, and the ion conductivity reaches 2 ．27×10-3Scm-1, and the cycle performance is better than Celgard diaphragm, the porous fiber structure of PET diaphragm remains stable after 50 cycles of battery cycle. ②Polyimide Polyimide (PI) is also one of the polymers with good comprehensive properties. It has excellent thermal stability, higher porosity, and better high temperature resistance, which can be in the range of -200 to 300 Long-term use at ℃. Miao et al. used the electrospinning method to manufacture PI nanofiber membranes. The membrane has a degradation temperature of 500°C, which is 200°C higher than that of traditional Celgard membranes. It will not undergo aging and thermal shrinkage at a high temperature of 150°C. Secondly, due to the strong polarity of PI and good wettability to the electrolyte, the manufactured diaphragm exhibits the best liquid absorption rate. The PI diaphragm made by electrospinning has lower impedance and higher rate performance than Celgard diaphragm. The capacity retention rate is still 100% after 100 cycles of charge and discharge at 0.2C. ③Meta-aramid PMIA is an aromatic polyamide with metabenzamide-type branches on its skeleton and has a thermal resistance of up to 400℃. Due to its high flame retardancy, the diaphragm using this material can improve lithium batteries The safety performance. In addition, due to the relatively high polarity of the carbonyl group, the separator has high wettability in the electrolyte, thereby improving the electrochemical properties of the separator. Generally speaking, PMIA separators are manufactured by non-woven methods, such as electrospinning. However, due to the problems of non-woven separators, such as large pore diameters, they will cause self-discharge, which will affect the safety performance and electrochemical performance of lithium batteries. To a certain extent, the use of non-woven membranes is restricted, and the phase inversion method has commercial prospects due to its versatility and controllability. ④ PBO (poly-p-phenylene benzodiazole), a new polymer material of poly-p-phenylene benzodiazole, is an organic fiber with excellent mechanical properties, thermal stability and flame retardancy. Its matrix is u200bu200ba linear chain structure polymer, which is not analyzed below 650°C. It has ultra-high strength and modulus, and is an ideal heat-resistant and impact-resistant fiber material. Because the surface of the PBO fiber is extremely smooth and the physical and chemical inertness is extremely strong, it is difficult to change the fiber morphology. PBO fiber is only soluble in 100% concentrated sulfuric acid, methanesulfonic acid, fluorosulfonic acid, etc. After strong acid etching, the fibrils on the PBO fiber will be peeled off from the backbone, forming a split filament morphology, and improving the ratio. Surface area and interface bond strength. In order to improve the safety of the lithium battery and ensure the safe and stable operation of the battery, the diaphragm must meet the following conditions: 1. Chemical stability: does not react with electrolyte and electrode materials; 2. 2. Wetting property: It is easy to infiltrate with electrolyte without stretching or shrinking; 3. 3. Thermal stability: resistant to high temperature, with high fuse isolation; 4. Mechanical strength: good tensile strength to ensure that the strength and width of the automatic winding are unchanged; 5. Porosity: higher porosity to meet the needs of ion conductivity. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete.