What is the process technology of lithium battery diaphragm industry -Lithium - Ion Battery Equipment
What is the process technology of lithium battery diaphragm industry? Lithium-ion battery separators have complex processing techniques and high technical barriers. Lithium-ion battery separator is a critical inner layer component in a lithium-ion battery. Key properties such as battery capacity, cycle performance, and charge-discharge current density all have a direct relationship with the diaphragm, and the improvement of the performance of the diaphragm plays an important role in improving the overall performance of lithium-ion batteries.(Lithium - Ion Battery Equipment)
What is the process technology of lithium battery diaphragm industry?
At present, there are mainly four kinds of industrial lithium battery diaphragm manufacturing technologies: wet method, dry method, semi-dry method and non-woven method. Among them, there are further classifications of wet method and dry method.
1. Wet technology
Lithium battery diaphragm wet technology is mainly used in the manufacture of polyethylene (PE) diaphragm. Since paraffin oil and PE are mixed to occupy space in the process, and solvent extraction is used to remove them after the stretching process, the process is called wet method. Wet technology involves stretching the film in 2 directions, so it is divided into synchronous stretching and stepwise stretching.
There has been a debate about whether simultaneous or step stretching is more advanced. Controversy is currently focused on product quality, efficiency, and process adaptability. From the comparison of the microscopic morphology of the product, the diaphragm manufactured by the synchronous stretching process has higher porosity, more uniform pore distribution, and better thickness uniformity;
At the same time, the product of simultaneous stretching has average strength and high yield rate, and its comprehensive performance is theoretically better. If it is compared in terms of processing efficiency and lithium-ion battery process adaptability, it is temporarily impossible to give a good or bad judgment. The only difference is the difference in the equipment level of different companies and the difference in process maturity. Judging from user feedback, the difference in the performance of the two products in use is not clear.
2. Dry technology
Dry technology is mainly used in the manufacture of polypropylene (PP) diaphragms. Dry technology mainly includes three kinds of technology: blown film + uniaxial stretching, cast sheet + uniaxial stretching and biaxial stretching. Relatively speaking, dry technology is simpler than wet technology, with lower equipment costs and lower processing efficiency.
3. Semi-dry technology
The semi-dry method is used in the manufacture of polyethylene (PE) diaphragms, which is a newly introduced method in recent years. It is also filled with a pore former, which is then removed by evaporation. The non-woven fabric method (Non-Woven) is currently mainly used in the manufacture of polyester (PET) non-woven fabrics and ceramic particle composite diaphragms. The inevitable presence of large pores in nonwovens brings a higher risk of short circuits to composite separators. This defect restricts the use of non-woven diaphragms and requires a breakthrough improvement in process technology.
4. Non-woven method
Non-woven separator substrates usually use polyethylene terephthalate (PET, with a melting point of up to 225°C) and polyimide (PI, with a melting point of over 500°C), which have obvious advantages in heat resistance. At the same time, due to its three-dimensional pore structure, it can effectively prevent the short circuit phenomenon caused by acupuncture and improve the liquid retention rate.
At present, domestic and foreign companies have achieved a lot of results in the research, use and performance optimization of non-woven separators, but there is no successful case of large-scale commercial use in lithium-ion batteries.
Development Trend of Lithium Battery Diaphragm Technology
The development of power lithium batteries has clarified the direction and put forward detailed requirements for the development of diaphragms. The development of power lithium batteries consists of three elements: improving energy density, ensuring safety, and reducing costs. The specific energy of the monomer can reach more than 300Wh/kg, the specific energy of the system can reach 260Wh/kg, and the cost can be reduced to less than 1 yuan/Wh.
Correspondingly, the requirements for the lithium battery separator are two aspects: higher safety, and more conducive to battery performance. From the perspective of benefiting the performance of lithium-ion batteries, it is necessary to further optimize the structural characteristic parameters and consistency of the separator. Such as thickness, reasonable value of porosity, optimized pore size, optimized pore size distribution, etc.
What is the process technology of lithium battery diaphragm industry?
At present, there are mainly four kinds of industrial lithium battery diaphragm manufacturing technologies: wet method, dry method, semi-dry method and non-woven method. Among them, there are further classifications of wet method and dry method.
1. Wet technology
Lithium battery diaphragm wet technology is mainly used in the manufacture of polyethylene (PE) diaphragm. Since paraffin oil and PE are mixed to occupy space in the process, and solvent extraction is used to remove them after the stretching process, the process is called wet method. Wet technology involves stretching the film in 2 directions, so it is divided into synchronous stretching and stepwise stretching.
There has been a debate about whether simultaneous or step stretching is more advanced. Controversy is currently focused on product quality, efficiency, and process adaptability. From the comparison of the microscopic morphology of the product, the diaphragm manufactured by the synchronous stretching process has higher porosity, more uniform pore distribution, and better thickness uniformity;
At the same time, the product of simultaneous stretching has average strength and high yield rate, and its comprehensive performance is theoretically better. If it is compared in terms of processing efficiency and lithium-ion battery process adaptability, it is temporarily impossible to give a good or bad judgment. The only difference is the difference in the equipment level of different companies and the difference in process maturity. Judging from user feedback, the difference in the performance of the two products in use is not clear.
2. Dry technology
Dry technology is mainly used in the manufacture of polypropylene (PP) diaphragms. Dry technology mainly includes three kinds of technology: blown film + uniaxial stretching, cast sheet + uniaxial stretching and biaxial stretching. Relatively speaking, dry technology is simpler than wet technology, with lower equipment costs and lower processing efficiency.
3. Semi-dry technology
The semi-dry method is used in the manufacture of polyethylene (PE) diaphragms, which is a newly introduced method in recent years. It is also filled with a pore former, which is then removed by evaporation. The non-woven fabric method (Non-Woven) is currently mainly used in the manufacture of polyester (PET) non-woven fabrics and ceramic particle composite diaphragms. The inevitable presence of large pores in nonwovens brings a higher risk of short circuits to composite separators. This defect restricts the use of non-woven diaphragms and requires a breakthrough improvement in process technology.
4. Non-woven method
Non-woven separator substrates usually use polyethylene terephthalate (PET, with a melting point of up to 225°C) and polyimide (PI, with a melting point of over 500°C), which have obvious advantages in heat resistance. At the same time, due to its three-dimensional pore structure, it can effectively prevent the short circuit phenomenon caused by acupuncture and improve the liquid retention rate.
At present, domestic and foreign companies have achieved a lot of results in the research, use and performance optimization of non-woven separators, but there is no successful case of large-scale commercial use in lithium-ion batteries.
Development Trend of Lithium Battery Diaphragm Technology
The development of power lithium batteries has clarified the direction and put forward detailed requirements for the development of diaphragms. The development of power lithium batteries consists of three elements: improving energy density, ensuring safety, and reducing costs. The specific energy of the monomer can reach more than 300Wh/kg, the specific energy of the system can reach 260Wh/kg, and the cost can be reduced to less than 1 yuan/Wh.
Correspondingly, the requirements for the lithium battery separator are two aspects: higher safety, and more conducive to battery performance. From the perspective of benefiting the performance of lithium-ion batteries, it is necessary to further optimize the structural characteristic parameters and consistency of the separator. Such as thickness, reasonable value of porosity, optimized pore size, optimized pore size distribution, etc.
