What is the difference between the dry process and the wet process of the lithium iron battery separator
The dry process can be subdivided into a uniaxial stretching process and a biaxial stretching process. The dry uniaxial stretching process is to prepare a high-oriented polypropylene or polyethylene film with low crystallinity by producing hard elastic fibers, and obtain a film with high crystallinity during high temperature annealing. The film is first stretched at low temperature to form micro-defects, and then at high temperature, the defects are pulled apart to form micro-pores.(Lithium - Ion Battery Equipment)
Dry biaxial stretching process, by adding β crystal form modifier with nucleation purpose to polypropylene, using the difference in density between different phases of polypropylene, during the stretching process, polypropylene is transformed from crystal form to form Microporous. At present, more than one-third of my country's production uses the dry double-drawing process, and the products occupy a large proportion in the low-end market. Scope of application: large lithium-ion power lithium batteries (electric vehicles, electric motorcycles, power tools, large energy storage equipment, large batteries for special purposes)
Wet production process of Fe-Li-ion battery separator
Wet production process, also known as phase separation method or thermally induced phase separation method, the 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 lowered for phase separation and pressing. The membrane is obtained, then heated to a temperature close to the melting point, biaxially stretched to orient the molecular chain, and finally kept for a period of time, and the residual solvent is eluted with volatile substances to prepare the interconnected microporous membrane material.
The wet production process can not only prepare interconnected microporous membrane materials, but also produce power iron-lithium-ion battery separators with high vertical and horizontal strengths. At present, wet production processes are mainly used to produce single-layer lithium-ion battery separators. Applications: high-performance lithium-ion batteries, etc.
In terms of physical properties and mechanical properties, the separator produced by the dry uniaxial stretching process has more advantages. However, the lithium-ion battery separator produced by the wet production process has high porosity and good air permeability, which can meet the requirements of high-current charging and discharging of power lithium batteries.