Advantages of dry and wet production processes for 402030 polymer battery diaphragms

Advantages of wet and dry production processes for 402030 polymer battery diaphragms. The production processes of 402030 polymer battery diaphragms are divided into two categories: dry production processes and wet production processes. The diaphragms in lithium batteries play a vital role in the performance of the battery, but there are many and very complex production processes for battery diaphragms. Which process is more advantageous, dry or wet manufacturing? Advantages of wet and dry production processes for 402030 polymer battery diaphragms: In the field of wet diaphragms, China is still in the early stages of import substitution. In the field of dry diaphragms, the white paper believes that dry diaphragms are relatively mature, the competition is more intense than wet diaphragms, and they can basically completely replace imported diaphragms, facing downward price pressure.

The wet production process mixes liquid hydrocarbons or some small molecules with polyolefin resin, heats and melts them to form a uniform mixture, then cools them down for phase separation, presses them to obtain a membrane, heats the membrane to a temperature close to the melting point, and performs biaxial stretching to orient the molecular chains. Finally, keep the temperature for a certain period of time, and use volatile substances to wash away the residual solvent to prepare a microporous membrane material that is interconnected. The dry 402030 polymer battery process can be divided into uniaxial stretching process and biaxial stretching process. The dry uniaxial stretching process is to prepare a low-crystallinity, highly oriented polypropylene or polyethylene film by producing hard elastic fibers, and then anneal at high temperature to obtain a high-crystallinity oriented film.

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 biaxial stretching process adds a β-crystal modifier with nucleation effect to polypropylene, and uses the difference in density between different phases of polypropylene to form micropores during the stretching process. It is used to produce single-layer PP film.

Currently, more than one-third of China's production capacity uses the dry biaxial stretching process, and its products occupy a large proportion in the low- and medium-end markets. Application scope: large lithium-ion power batteries. Battery separator technology is now mature, whether it is dry or wet manufacturing of battery separators. The many characteristics that 402030 polymer battery separators need to have put forward special requirements for their production process, and the production process includes raw material formula and rapid formula adjustment, micropore preparation technology, complete set of equipment independent design and other processes. The dry method can be subdivided into unidirectional stretching process and bidirectional stretching process. The dry unidirectional stretching process is a method of producing hard elastic fibers to prepare a low-crystallinity, highly oriented polypropylene or polyethylene film, 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. At present, more than one-third of China's production capacity uses the dry bidirectional stretching process, and the products occupy a large proportion in the low- and medium-end markets. Application scope: Large lithium-ion power battery The wet production process of lithium batteries, also known as phase separation or thermal phase separation, is a process in which liquid hydrocarbons or some small molecular substances are mixed with polyolefin resins, heated and melted to form a uniform mixture, then cooled for phase separation, pressed to obtain a membrane, and then 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. The residual solvent is washed away with volatile substances to prepare microporous membrane materials that are interconnected. The wet production process can not only prepare microporous membrane materials that are interconnected, but also produce 402030 polymer battery separators with high longitudinal and transverse strength.

At present, the wet production process is mainly used to produce single-layer 402030 polymer battery separators. Application scope: high-performance lithium batteries, etc. In terms of physical properties and mechanical properties, the separators produced by the dry uniaxial stretching process have more advantages. However, the 402030 polymer battery separators produced by the wet production process have higher porosity and good air permeability, which can meet the requirements of high current charging and discharging of power batteries. On the contrary, since the wet production process uses a polyethylene substrate, the melting point of the polyethylene substrate is only 140°C, so compared with the 402030 polymer battery separator produced by the dry production process, the thermal stability of the 402030 polymer battery separator produced by the wet production process is poor.

The dry molding process needs to go through the steps of melt extrusion → high-multiple 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 fluidity of the material. The chiller cools the cooling roller during the cooling stage, and the mold temperature controller heats during the heat treatment stage. The wet production process, also known as the phase separation method or the thermally induced phase separation method, 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, performs biaxial stretching to orient the molecular chains, and finally keeps them warm for a certain period of time, and uses volatile substances to wash out the residual solvent. In general, the technology of 402030 polymer battery separators 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, and its cost is lower than the wet method, but its stability is poorer than the wet method.

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