Difficulties in lithium battery separator technology and lithium battery separator production process. The core materials of lithium batteries include four parts: positive electrode, negative electrode, electrolyte, and separator. At present, domestic cathode, cathode, and electrolyte technologies are mature and basically meet the needs of the domestic market, achieving high-quality localization. However, separator manufacturing is still relatively dependent on imports, and domestic supply is low-end. Due to the high technical barriers to separator production, The entry threshold is also high, and it will become a trend to seize the diaphragm market share and seize market opportunities!

　　The separator plays a role in preventing short circuits between the positive and negative electrodes in lithium batteries, and provides a lithium ion transport channel during the charging and discharging process of lithium batteries. Simply put, a separator is a porous plastic film. But it directly affects the battery's capacity, cycle performance and safety performance. Among the components of lithium batteries, it has the highest technical content, accounting for 20% to 30% of the cost of lithium batteries. At present, 80% of lithium battery separators in our country rely on imports.

　　What are the difficulties in lithium battery separator technology?

　　Many domestic companies are trying to break through foreign technical barriers and develop lithium battery separators, but it is difficult. The difficulty is mainly reflected in the following three aspects:

　　First, the patents related to the traditional separator preparation process are basically monopolized by a few companies in the United States and Japan, and my country lacks independent intellectual property rights in production technology;

　　Second, domestic companies are lacking in key technologies for producing lithium battery separators, especially in industrialization technology. Many companies are often able to produce good samples during small trials, but the consistency of the products is poor during large-scale production;

　　Third, our country keeps pace with the world in research on new processes and new methods. However, new processes often have higher requirements for equipment and process control. Our country’s foundation for precision processing equipment is relatively weak, which limits industrialization.

　　Although difficult, domestic lithium battery separators have begun to take off. Now some domestic companies have made some technological breakthroughs in localization, such as Shenzhen Xingyuan Material Technology Co., Ltd., Foshan Jinhui Hi-Tech Optoelectronic Materials Co., Ltd., Henan Xinxiang Green New Energy Materials Co., Ltd., etc. These companies All have produced lithium battery separators with independent intellectual property rights, but currently most of them are supplied to the mid- and low-end markets, and further maturity of membrane technology is needed.

　　The high-tech barriers of separators are relatively high among the entire power lithium battery raw materials, and the core technology is monopolized by companies in some countries such as Japan and the United States. As a result, the quality of separators produced by my country's separator manufacturers still lags behind the international level.

　　Lithium battery separator production process

　　At present, there are two main methods for producing lithium battery separators: dry method (melt stretching method) and wet method (thermally induced phase separation method). Dry film mainly produces PP film. The process has experienced decades of development and is relatively mature. It is divided into uniaxial stretching and biaxial stretching. The commonly used method in my country is uniaxial stretching. Wet method is a technology that has only emerged in recent years and mainly produces PE films.

　　The dry process mainly melts polyolefin resin and extrudes it to form a crystalline polymer film. After crystallization, a high crystallinity structure is obtained, and then stretched at high temperature to peel off the crystal structure to form a porous film. This method has mature equipment, relatively simple process, and pollution-free production. The wet process mainly involves mixing liquid hydrocarbons or some high-boiling point small molecular substances with polyolefin resin and then melting them. Through extrusion, casting, biaxial stretching, extraction and other processes, an interconnected microporous membrane is prepared.

　　It can be seen that the process flow of lithium battery wet film is more complicated than that of dry film, so it is more suitable for high-power and high-capacity batteries. The increase in subsidy thresholds, consumer demand for high-mileage electric vehicles, and safety performance requirements have directly increased the requirements for battery capacity and power, thus bringing more opportunities to the wet film market.

　　The production process of lithium battery separators is complex and the technical barriers are high. The separator production process includes raw material formula and rapid formula adjustment, micropore preparation technology, independent design of complete sets of equipment, and many other processes. Among them, micropore preparation technology is the core of the lithium battery separator preparation process. According to the difference in micropore formation mechanism, the separator process can be divided into two types: dry method and wet method.

　　Wet coating is the development direction of lithium battery separators. The stability, consistency, and safety of the separators have a decisive impact on the discharge rate, energy density, cycle life, and safety of lithium batteries.

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