Briefly describe the comparison of dry and wet production processes of button battery cr2032 diaphragms

The wet process produces small and uniform micropores, but it is not environmentally friendly. The wet process molding process is easy to control, the obtained diaphragm has high biaxial tensile strength and high puncture strength, the normal process will not cause perforation, and the micropore size is relatively small and evenly distributed. The product can be made very thin, with better mechanical properties and product uniformity, suitable for high-capacity batteries, and is mainly used in high-end mobile phones, laptops, 3C electronic products and other fields.

The high porosity and air permeability of this type of diaphragm give the battery a higher energy density and better charge and discharge performance, which can meet the high current charge and discharge of power lithium batteries. It is mainly adopted by well-known domestic lithium-ion battery manufacturers in the power lithium battery market. However, the wet process requires a large amount of solvent, which is easy to cause environmental pollution; compared with the dry process, the equipment is complex, the investment is large, the cycle is long, the cost is high, and the energy consumption is high.

As one of the four core components of lithium-ion batteries, the diaphragm accounts for 10%-14% of the cost of lithium-ion batteries, and the gross profit margin is as high as 50%-60%. The technology of lithium iron ion battery separator is now mature. Whether it is dry or wet manufacturing of battery separators, it can well meet the needs of products in different fields.

The production process of lithium iron ion battery separators includes: raw material formula, complete set of equipment independent design, micropore preparation technology, etc. Among them, the core of the lithium ion battery separator preparation process is micropore preparation technology. According to the difference in micropore formation mechanism, the separator production process can be divided into dry and wet methods.

1. Dry production process of lithium iron ion battery separator

The dry process of lithium iron ion battery separator can be subdivided into unidirectional stretching process and bidirectional stretching process. The dry unidirectional stretching process is to prepare a low crystallinity high-oriented polypropylene or polyethylene film by producing hard elastic fibers, and obtain a high crystallinity film during high temperature annealing. This film is first stretched at low temperature to form micro defects, and then the defects are pulled apart at high temperature to form micropores.

The dry bidirectional stretching process is a process with independent intellectual property rights developed by the Institute of Chemistry of the Chinese Academy of Sciences in the early 1990s. The dry biaxial stretching process adds a β crystal modifier with nucleation function to polypropylene, and utilizes the density difference between different phases of polypropylene to transform polypropylene from a crystal form to form micropores during the stretching process.

2. Wet production process

Also known as phase separation or thermal phase separation, the wet process mixes liquid hydrocarbons or some small molecular substances with polyolefin resins, heats and melts them to form a uniform mixture, then cools them for phase separation, presses them to obtain a membrane, and then heats the membrane to a temperature close to the melting point, biaxially stretches them to orient the molecular chains, and finally keeps them warm for a period of time, and uses volatile substances to wash away the residual solvent, so as to prepare a microporous membrane material that is interconnected.

The wet production process can not only prepare microporous membrane materials that are interconnected, but also produce iron-lithium ion battery separators with high longitudinal and transverse strength. At present, the wet production process is mainly used to produce single-layer lithium ion battery separators.

From a theoretical analysis, the diaphragm produced by the dry biaxial stretching process is biaxially stretched, and the transverse tensile strength is significantly higher than that of the diaphragm produced by the dry uniaxial stretching process when the longitudinal tensile strength is not much different. In terms of physical and mechanical properties, the diaphragm produced by the dry uniaxial stretching process has more advantages. However, the iron lithium ion battery diaphragm produced by the wet production process has a higher porosity and good air permeability, which can meet the requirements of high current charging and discharging of power lithium batteries.

Read recommendations:

18650 1200mAh 3.7V

Are lithium batteries assembled in parallel or in series?

Classification of low-temperature lithium batteries

522749 battery wholesale

rechargeable battery 18650 3.7v