What are the main lithium materials for lithium ion battery separators?
The separator is an important part of lithium-ion batteries. In the structure of lithium-ion batteries, the separator is one of the most important materials. At present, the commercial lithium-ion battery separators are mainly polyolefin separators, and the preparation process is changing from dry method. Transition to wet process, but in recent years, different material systems and separators with different preparation processes have been developed.
In the structure of lithium batteries, the lithium-ion battery separator is one of the key inner layer components. For lithium battery series, the performance of the separator determines the interface structure and internal resistance of the battery, which directly affects the capacity, cycle and safety performance of the battery. According to the differences in physical and chemical properties, lithium-ion battery separators can be divided into: woven membranes, non-woven membranes (non-woven fabrics), microporous membranes, composite membranes, separator paper, and rolled membranes. Although there are many types, polyethylene and polypropylene microporous membranes are mainly used as separator materials for commercial lithium-ion batteries so far. Polyolefin materials have excellent mechanical properties, chemical stability and relatively cheap characteristics, so polyolefin microporous membranes such as polyethylene and polypropylene have been used as lithium-ion battery separators in the early stage of lithium-ion battery research and development.
The market-oriented lithium-ion battery separator materials are mainly polyolefin (Polyolefin) separators based on polyethylene (PE) and polypropylene (PP), among which PE products are mainly made by wet process, PP products are mainly Mainly obtained by dry process. As for the characteristics of the two lithium-ion battery separator materials, PE and PP.
1. PP is relatively more resistant to high temperature, and PE is relatively resistant to low temperature;
2. The density of PP is smaller than that of PE;
3. PP has higher melting point and closed cell temperature than PE;
4. PP products are more brittle than PE;
5. PE is more sensitive to environmental stress.
Important lithium-ion battery separator materials include single-layer PP, single-layer PE, PP+ceramic coating, PE+ceramic coating, double-layer PP/PE, double-layer PP/PP and three-layer PP/PE/PP, etc. Two types of products are mainly used in the field of 3C small batteries, and the latter types are mainly used in the field of power lithium-ion batteries.
Among the diaphragm materials for power lithium-ion batteries, the double-layer PP/PP diaphragm materials are mainly produced by Chinese companies and used in mainland China. This is mainly because no Chinese company can make PP and PE into a double-layer composite film at this stage. technology and capabilities. The separators used in global automotive power lithium-ion batteries are mainly three-layer PP/PE/PP, double-layer PP/PE, and PP+ceramic coating, PE+ceramic coating and other separator materials.