What are the structural characteristics of lithium battery separators?

◆Thickness. The thickness of the lithium battery separator is generally ≤25μm. Under the premise of ensuring a certain mechanical strength, the thinner the thickness of the diaphragm, the better. At present, most of the new high-energy batteries use single-layer separators with a thickness of 20 μm or 16 μm. ◆Aperture and distribution. As a lithium battery separator material, it has a microporous structure that allows the electrolyte to be absorbed; in order to ensure consistent electrode/electrolyte interface properties and uniform current density in the battery, the micropores should be uniformly distributed throughout the separator material. The size and uniformity of the pore size have a direct impact on the performance of lithium batteries: too large a pore size, it is easy to make the positive and negative electrodes directly contact or easy to be pierced by lithium dendrites and cause a short circuit; too small a pore size will increase the resistance. The uneven distribution of micropores will cause excessive local current during operation, which will affect the performance of the battery. ◆Porosity. The permeability can be characterized by the amount of gas passing through the diaphragm under a time and pressure, which mainly reflects the patency of lithium ions through the diaphragm. Porosity is very important for membrane permeability and electrolyte capacity. The porosity of most commercial lithium battery separators is between 40%-50%. ◆Permeability. The time required for a certain amount of air to pass through the diaphragm under certain conditions is called the Gurly value. The permeability of the lithium battery separator is the result of the comprehensive factors affecting the internal pore structure of the separator such as the porosity, pore size, pore shape and pore tortuosity of the separator. ◆Thermal stability: The separator should be thermally stable within the temperature range (-20℃~60℃) used by the lithium battery. Generally speaking, PE or PP materials currently used in diaphragms can meet the above requirements. Of course, the other is that because the electrolyte is sensitive to moisture, most manufacturers will bake at about 80C before injection, which will not pose a big problem for PP/PE diaphragms. ◆Consistency: Due to different preparation processes, the consistency of lithium battery separators may be quite different. Consistency includes self-characteristics such as closing temperature, as well as apparent consistency such as the consistency of the hole and thickness of the observation under the electron microscope. 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: What are the basic types of lithium battery electrolyte?