The advantages of lithium battery separator wet production process and dry production process. The production process of lithium battery separators is divided into two categories: dry production process and wet production process. The separator in lithium batteries plays a vital role in the performance of the battery. However, there are many and very complex production processes for battery separators. Which process is more advantageous, dry or wet manufacturing?

　　Advantages of lithium battery separator wet production process and dry production process:

　　In the field of wet separators, China is still in the early stages of import substitution. In the field of dry-process separators, the white paper believes that dry-process separators are currently relatively mature and the competition is more intense than that of wet-process separators. They can basically completely replace imported separators and are facing downward pressure on prices.

　　The wet production process mixes liquid hydrocarbons or some small molecular substances with polyolefin resin. After heating and melting, a uniform mixture is formed. The temperature is then cooled for phase separation, and the film is pressed to obtain a film. The film is then heated to a temperature close to the melting point, and the two-way process is carried out. Stretching orients the molecular chains, and finally it is kept warm for a certain period of time, and the remaining solvent is eluted with volatile substances to prepare an interconnected microporous membrane material.

　　The dry lithium battery process can be subdivided into uniaxial stretching process and biaxial stretching process. The dry uniaxial stretching process is a method of producing hard elastic fibers to prepare highly oriented polypropylene or polyethylene films with low crystallinity, and then annealing them at high temperature to obtain oriented films with high crystallinity. This film is first stretched at low temperatures to form micro-defects, and then at high temperatures the defects are pulled apart to form micropores.

　　The dry biaxial stretching process adds a nucleating beta crystal form modifier to polypropylene and utilizes the density difference between different phases of polypropylene to cause crystal form transformation to form micropores during the stretching process, which is used for production Single layer PP film. At present, more than one-third of China's production capacity uses the dry double drawing process, and its products occupy a large proportion of the mid- to low-end market. Application scope: large lithium-ion power battery.

　　Battery separator technology is now mature, whether it is a battery separator manufactured by dry or wet methods.

　　The many characteristics that lithium battery separators need to possess put forward special requirements for its production process, which includes raw material formula and rapid formula adjustment, micropore preparation technology, and independent design of complete sets of equipment.

　　The dry method can be subdivided into one-way stretching process and two-way stretching process. The dry uniaxial stretching process is a method of producing hard elastic fibers to prepare highly oriented polypropylene or polyethylene films with low crystallinity. During the high-temperature annealing process, a film with high crystallinity is obtained. This film is first stretched at low temperatures to form micro-defects, and then at high temperatures the defects are pulled apart to form micropores.

　　At present, more than one-third of China's production capacity uses the dry double drawing process, and its products occupy a large proportion of the mid- to low-end market. Application scope: Large lithium-ion power battery

　　Lithium battery wet production process, also known as phase separation method or thermal phase separation method, the wet process mixes liquid hydrocarbons or some small molecular substances with polyolefin resin, heats and melts them to form a uniform mixture, and then cools down to perform phase separation. , press the membrane to obtain a membrane, then heat the membrane to a temperature close to the melting point, perform biaxial stretching to orient the molecular chains, and finally keep it warm for a certain period of time, and use volatile substances to elute the remaining solvent to prepare interconnected microporous membrane materials. .

　　The wet production process can not only prepare interconnected microporous membrane materials, but also produce lithium battery separators with high longitudinal and transverse strength. At present, the wet production process is mainly used to produce single-layer lithium battery separators. Application scope: high-performance lithium batteries, etc.

　　In terms of physical and mechanical properties, the separator produced by the dry uniaxial stretching process has more advantages. However, lithium battery separators produced by wet production processes have high porosity and good air permeability, which can meet the high current charging and discharging requirements of power batteries. On the contrary, since the wet production process uses polyethylene material, the melting point of the polyethylene material is only 140°C. Therefore, compared with the lithium battery separator produced by the dry production process, the lithium battery separator produced by the wet production process is Thermal stability is poor.

　　The dry molding process requires steps such as melt extrusion → high-power stretching → cooling → heat treatment → stretching → heat setting → slitting and winding. The mold temperature controller controls the extrusion temperature during the melt extrusion process to ensure the flow of the material. sex. The chiller cools down the cooling roller in the cooling stage, and the mold temperature controller heats it in the heat treatment stage.

　　Wet production process, also known as phase separation method or thermal phase separation method, wet process mixes liquid hydrocarbons or some small molecular substances with polyolefin resin. After heating and melting, a uniform mixture is formed, and then the temperature is cooled for phase separation and pressing. The membrane is obtained, and then the membrane is heated to a temperature close to the melting point, biaxially stretched to orient the molecular chains, and finally kept warm for a certain period of time, and the remaining solvent is eluted with volatile substances.

　　In general, lithium battery separator technology is now mature, whether it is a battery separator manufactured by dry or wet methods. However, the dry method does not require the extraction step, the cost is lower than the wet method, and the stability is poorer than the wet method.

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