Overview of the diaphragm

Separator, plays the role of electronic insulation and ion conduction in lithium-ion batteries; separator, as everyone knows, is one of the four major raw materials for lithium batteries, accounting for about 20% of the entire battery cost; the quality of the separator has a direct impact The performance of the battery not only contains electrical performance, but also its production performance is also deeply affected, such as: short circuit, low voltage, etc.; I believe that many manufacturers have been worrying about the low pressure and flatulence in the customer complaint. Then, the first step is to choose Good for your diaphragm; before testing the diaphragm, you need to understand the key test parameters of the diaphragm; in this post, I will only analyze the parameters that the general lithium battery manufacturers need to test. It is best to check these items: 1. Basic parameters, Including: thickness, width, areal density (calculation method), radian (winding is very important), etc.; these are very simple, not detailed; 2. Appearance: white, no burrs, no burrs, smooth and wrinkle-free, no pollution , No scratches, no gel spots, no black spots, these are mainly used to see; 3. Pinhole: use a dark box to detect, a very simple device, use a box to cover a light bulb, open a small opening on the box, a small device, For large purposes, the straightness of these pinholes affects the short-circuit rate; pinholes can be easily found with a dark box. If you can’t tell if they are pinholes, you can take SEM. The following picture is the pinhole SEM image: our company did an experiment , The same brand of diaphragms with pinholes and without pinholes were tested, and it was found that the short-circuit rate with pinholes was three times that of without pinholes, which shows how important the pinhole test is; 4. Air permeability: different The air permeability will affect the performance of the battery, such as rate performance, internal resistance, etc.; if the fluctuation is too large, it will directly affect the short circuit of the assembly process. Therefore, the air permeability range must be specified during sample certification. For batch monitoring, the fluctuation range cannot exceed 50S/100CC; if it is too large, the consistency of the product cannot be guaranteed. Just use Gurley index detector for air permeability detection. The imported one is only more than 40,000. Small investment, big return; if you really don’t want to buy it, just send it to me to help you detect it. A small fee will be charged, haha. 5. Scanning Electron Microscope: Manufacturers who do not have conditions have to send for testing at the sample stage to confirm whether the pores of the diaphragm are average and whether there are broken holes; through SEM, we can see the consistency of the manufacturer’s products straightforwardly; you can also understand this The process used in the factory is wet or dry; I have the SEM pictures of diaphragms from all over the world, and they will be updated regularly. Accumulation is very important. From these, we can also see which factories are making progress. After mass production, each batch can be sent for testing if conditions permit. 6. Other parameters: liquid absorption (that is, soak in electrolyte, see how much is absorbed, soak time is specified by yourself, do not change after the regulations, so as to facilitate comparison); heat shrinkage rate (generally 90 degrees baking 4h, standard You can refer to the supplier’s detection results, or based on the process requirements. The general diaphragm is no problem); it’s fine to detect these parameters when the samples are recognized. The first 5 items will not cause any problems, and none of these will have any problems. Too big a problem. 7. Inspection-free items: acupuncture strength, tensile strength, corrosion resistance, etc.; just follow the supplier's order, and the general problem is not big. Okay, that's all, please correct me if there are any incorrect or missing ones. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Lithium Battery-Conductive Agent