Organic/inorganic composite nanofiber membrane of lithium ion power battery and preparation method of organic/inorganic composite nanofiber membrane

Abstract

The invention belongs to the field of diaphragm materials of lithium ion power batteries, in particular to an organic / inorganic composite nanofiber membrane of a lithium ion power battery and a preparation method of the organic / inorganic composite nanofiber membrane. A non-woven fabric type nanofiber membrane is formed by compositing inorganic powder such as nanometer oxides and nitrides and organic polymer such as polyvinylidene fluoride (PVDF), polyimide (PI) and polyethylene terephthalate (PET) by using an electrostatic spinning machine with a flat roller electrode. The prepared composite nanofiber membrane has the characteristics of small fiber diameter, high porosity, light weight, small thickness and the like, thermal closure temperature can be effectively improved, and diaphragm processibility is improved. Meanwhile, the preparation method has the advantages of high yield, maintainability and high controllability.

Description

technical field [0001] The invention belongs to the field of diaphragm materials for lithium-ion power batteries, and in particular relates to organic / inorganic composite nanofiber membranes for lithium-ion power batteries and a preparation method thereof. Background technique [0002] The separator is a key component related to the safety of lithium-ion batteries; currently, the materials of commercialized lithium-ion battery separators are mainly porous polymer films (such as PP, PP / PE / PP films), but as lithium-ion power batteries With the development of large-capacity batteries, the limitations of temperature resistance, lyophilic liquid retention and gas permeability of commercialized polyolefin separators pose a major threat to the safety performance of batteries. The development of ion battery industry is of great significance. [0003] In recent years, Japan's Mitsubishi, Prince, Baoling, Germany's Degussa and other internationally renowned separator manufacturers ha...

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Problems solved by technology

[0006] In terms of improving the thermal closure effect, choose PET (polyethylene terephthalate), which is superior to PP in temperature resistance, and the heat resistance will be greatly improved. The PET single-layer diaphragm itself has good high temperature stability. , with a melting point of 256~265°C; however, due to the relatively large pore size of the single-layer PET separator, weak barrier properties and poor safety, the current development trend tends to use PET as the matrix material and compound other organic or inorganic substances on the surface. Solve its defects; for example, BYD Co., Ltd. uses PET film as the base material to make a composite film by coating method. The composite film contains at least one layer of organic polymer film. The test found that the separator is used in batteries, which is high temperature resistant and safe, and the cycle performance of the battery is also good; Degussa has produced a non-woven fabric called Separion by compounding PET polymers with inorganic particles. Cloth composite diaphragm, which combines the flexibility of organic matter and the good thermal stability of inorganic matter, has been mass-produced. Its preparation method is to coat nano-alumina or other inorganic matter on PET fiber non-woven fabric. The melting temperature of the diaphragm can reach 230 Above 200°C, there will be no heat shrinkage at 200°C, and it has high thermal stability. In the process of charging and discharging, after reaching the thermal closure temperature, even if the temperature rises further, the organic bottom film melts, and the inorganic phase can still maintain the separator. Integrity, preventing large-area positive / negative short circuit phenomenon, improving the safety of the battery

[0007] In summary: the use of electrospinning technology to prepare non-woven lithium-ion battery separators is expected to make a huge breakthrough in technology and material properties. However, traditional electrospinning equipment needs to be equipped with nozzles, and the aperture of the nozzles determines the size of the fibers. Thickness requires a large number of nozzles to meet the requirements of different fibers, the pore size distribution is difficult to control, the bonding strength between fibers is low, and the nozzles are easy to block during the production process, requiring frequent maintenance, low production efficiency, and high cost. Therefore, it is basically in the experimental stage at present. It is difficult to do large-scale production; the current inorganic oxide composite method is mainly to coat the oxide coating on the surface of the organic substrate. Due to the brittleness of the inorganic coating, the adhesion of the coating to the sheet-shaped flexible substrate is relatively weak. Poor, in the process of battery processing, the diaphragm is prone to creases, breakage and coating particles falling off, thus causing safety hazards; at the same time, when making a composite diaphragm, because the coating solution is a suspension, it is easy to cause poor coating during coating. Uniform and uneven thickness will affect battery performance

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