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Analysis of the characteristics of two polyolefin battery separators
2024-07-21
Battery separator film is an important component of the battery. It has two main functions: one is to isolate the positive and negative electrodes of the battery to prevent the two electrodes from short-circuiting due to contact, ensuring the safety performance of the battery; the other is to allow electrolyte ions to pass freely during the charging and discharging process, but the electrons or ions in other solutions are blocked. Polyolefins are widely used in the lithium battery industry because of their good chemical stability, ability to ensure the normal operation of the battery in various environments, high mechanical strength, resistance to easy damage and low cost. Among the many polyolefins, PE (polyethylene) or PP (polypropylene) is generally used to prepare lithium battery separator film. In the following, we will focus on the characteristics of these two materials.
PE lithium battery separator film, as the name implies, is a film made of polyethylene material. PE has a certain degree of electronic insulation, which can ensure that the positive and negative electrodes will not contact and short-circuit; and it has a large number of micropores, allowing electrolyte ions to pass freely during the charge and discharge process, forming a charge and discharge circuit to ensure the normal operation of the battery. Apart from the general functions of these battery separator film, its advantages can be summarized as follows:
1. It has excellent low temperature resistance, and the lowest operating temperature can be close to minus 100℃.
2. It has good chemical stability and can withstand the erosion of most acids and alkalis, ensuring that the battery remains stable during long-term use.
3. It has good mechanical properties and can withstand a certain amount of pressure without breaking or deforming, which can ensure the safety of the battery when it is subjected to external shock or vibration.
However, PE lithium battery separator film is not omnipotent. Its melting point is low, only around 130℃. If it is in a high temperature or overheating environment, additional safety measures or the selection of diaphragms of other materials may be required. Due to the high production cost, it is also a major pain point of PE that limits its use in certain low-cost applications.
After talking about PE, let's talk about the advantages of PP lithium battery separator film:
1. It has good thermal stability and its melting point can reach about 165℃, so it can adapt to high temperature environments better than PE lithium battery separator film.
2. It has good chemical stability and can withstand a certain degree of corrosion from acids, alkalis, saline solutions and their organic solvents.
3. It has high mechanical strength and can withstand sufficiently high pressure without deformation. This can effectively prevent lithium dendrites from piercing the diaphragm.
4. Low cost and high cost performance make it highly competitive in the field of battery manufacturing.
Compared with PE, PP also has its own shortcomings. For example, PP has a higher conductivity, which will increase the internal temperature of the battery and affect its service life. In addition, it has poor wettability. If the electrolyte cannot fully infiltrate the electrode surface, a "hot spot" may form, causing the lithium-ion battery to overheat, which may cause an explosion in severe cases. In summary, both diaphragms have their own advantages and disadvantages, and appropriate materials can be selected according to the working requirements of the battery. With the rapid development of the new energy industry, the demand for high-performance batteries will continue to increase. Therefore, PE lithium battery separator film and PP lithium battery separator film will also have a broad market in the future. And with the continuous advancement and innovation of technology, the performance of the two diaphragms will be optimized to make up for their respective shortcomings and provide strong support for the development of the battery industry.
