What are the performance requirements of lithium battery separator materials

As one of the four important materials for lithium batteries, the lithium battery separator is generally a material with good insulation, which provides a migration channel for lithium ions in the electrolyte. The performance parameters of the separator have a significant impact on the performance of the battery. For example, in the commonly used commercial separator materials, the thickness of the material directly affects the internal resistance of the battery, and the pore size and distribution will affect the performance of lithium ion transmission. Therefore, the preparation of high-performance separator materials is related to the battery performance. Performance and actual use are crucial. The important factors that affect the performance of lithium battery separators include the chemical stability of the separator, mechanical strength, porosity and wettability, and self-sealing properties for safety protection. ⑴Mechanical strength The diaphragm must have a certain mechanical strength in the battery structure and the process of charging and discharging reactions. An important use of the diaphragm is to separate the positive and negative reactions. If the diaphragm shrinks or breaks and causes electrolyte penetration, a battery short circuit will occur, which poses a great safety hazard. Therefore, the diaphragm must have a certain degree of mechanical strength and toughness. During the charging process of lithium batteries, lithium ions are reduced to produce metallic lithium dendrites, which requires the diaphragm material to have a certain puncture resistance strength. In addition, the separator material should also have a certain tensile strength. The lithium battery will release or absorb heat during the reaction process, and the separator will expand and contract accordingly. If the tensile strength of the separator is not enough, it will cause the separator to break and cause The short circuit occurred. ⑵The thermal polarity is qualitative. In addition to water solvents, the electrolyte solution in lithium batteries will also use organic solvents and non-aqueous electrolytes. Therefore, the separator should have good chemical stability and corrosion resistance, and be able to achieve the structure during multiple charging and discharging of the battery. The completeness and stability of the reaction. In addition, the lithium battery will emit heat during the charge and discharge reaction, and the temperature of the battery will rise when the battery continues to work. The thermal stability of the separator can ensure that the shrinkage deformation is reduced when the battery is working for a long time, and the positive and negative electrodes caused by the shrinkage of the battery are guarded. Contact causes the battery to short circuit. (3) Pore distribution and porosity In order to maintain good lithium ion permeability, the material must have pores of a certain size, and ensure low resistance and high ion conductivity. The pore size will affect the internal resistance of the battery and the safety of the battery. Too small pores will reduce the ion penetration rate and increase the internal resistance of the battery. If the pores are too large, the probability of contact between the positive and negative electrodes of the battery will increase, which will easily lead to short circuits and fail to achieve the effect of the separator. A good lithium battery separator should ensure that the pore size is appropriate and evenly distributed, otherwise it will cause local current to be too large or too small, which will affect the battery performance. ⑷Other properties In addition, the self-sealing technology of the diaphragm is crucial to the safety of the battery. The self-sealing mechanism requires the diaphragm to release a large amount of heat when overloaded, and the temperature rises too high. When the material is close to the melting point, the pores in the diaphragm structure are closed to successfully isolate the ion shuttle and stop the positive and negative reactions to form a circuit breaker to prevent the battery from exploding under overheating. The wettability of the diaphragm is also one of the criteria for evaluating the performance of the diaphragm. In order to ensure the smooth transmission of ions, the diaphragm must be in sufficient contact with the electrolyte, and it has good wettability, electrolyte penetration and ion penetration. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.