What is the production process of 18650 lithium battery 3000mah separators?

　　Production process principle of 18650 lithium battery 3000mah separator

　　The production process of lithium iron phosphate battery separator is mainly divided into dry process and wet process. The main steps and principles of dry and wet process are:

　　1. The dry method first melts, extrudes and blows the polyolefin resin to form a crystalline polymer film, then performs crystallization heat treatment and annealing operations to obtain a highly oriented film structure, and then stretches it at high temperature for testing. The crystal cross sections are separated to form a porous structure battery separator. The dry process can also be divided into uniaxial stretching and biaxial stretching.

　　2. Wet method Traditional wet method preparation is mainly based on phase inversion method, and in recent years, TIPS thermally induced phase separation method is mainly used. The principle is to mix crystalline polymers, thermoplastic polymers and small molecule chemical diluents with high boiling points (such as paraffin oil) to form a homogeneous solution at high temperatures, and then lower the solution temperature to cause solid-liquid phase separation of the mixture. Or liquid-liquid separation, extracting and removing small molecule chemical diluents to form a porous membrane of thermoplastic and crystalline polymers.

　　Dry separators are divided into single-stretch and double-stretch according to the stretching orientation.

　　The dry separator process is the most commonly used method in the separator preparation process. This process is to mix high molecular polymers, additives and other raw materials to form a uniform melt. During extrusion, a lamellar crystal structure is formed under tensile stress. The lamellar crystal structure is heat treated. A hard elastic polymer film is obtained, which is then stretched at a certain temperature to form slit-like micropores, and then heat-set to obtain a microporous film. At present, dry processes mainly include dry uniaxial stretching and biaxial stretching.

　　The dry single drawing process flow is:

　　1) Feeding: After preprocessing raw materials such as PE or PP and additives according to the formula, they are transported to the extrusion system.

　　2) Casting: The pretreated raw materials are melted and plasticized in the extrusion system and then the melt is extruded from the die. The melt forms a base film with a specific crystal structure after casting.

　　3) Heat treatment: The base film is heat treated to obtain a hard elastic film.

　　The dry double drawing process flow is:

　　1) Feeding: Raw materials such as PP and pore-forming agent are pretreated according to the formula and then transported to the extrusion system.

　　2) Tape casting: Obtain PP cast sheets with high β-crystal content and good uniformity of β-crystal morphology.

　　3) Longitudinal stretching: The cast sheet is stretched longitudinally at a certain temperature, and the characteristics of β crystals that are prone to pore formation under tensile stress are used to cause pores.

　　4) Transverse stretching: The sample is stretched transversely at a higher temperature to expand the pores while improving the uniformity of pore size distribution.

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