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Method for preparing porous meta-aramid diaphragm through non-solvent induced phase separation method

A phase separation method and non-solvent technology, which is used in the field of preparing porous meta-aramid fiber membranes and preparing meta-aramid fiber membranes, which can solve the problems of increased battery resistance, shrinkage, and poor wettability.

Inactive Publication Date: 2021-09-10
CNOOC TIANJIN CHEM RES & DESIGN INST
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The application of polyolefin separators in small lithium-ion batteries can basically meet the requirements, but when applied to large-scale power lithium-ion batteries (electric vehicles, etc.), there are still the following defects: (1) Polyolefin separators have a negative effect on carbonate electrolytes. The wettability is poor, resulting in an increase in the internal resistance of the battery, resulting in low ionic conductivity; (2) When the battery temperature rises due to overcharge and overdischarge or external factors, the polyolefin separator will shrink or even Melting will cause the positive and negative poles to directly contact and short circuit, and even cause dangerous accidents such as fire accidents or explosions
Weihong Power System Co., Ltd. used the phase inversion method to prepare the aromatic polyamide membrane with a dense surface and a porous interior, and then removed the skin to form a three-dimensional mesh porous membrane for lithium-ion batteries (Sun Qingjin, Li Xiang, Huang Heji .An aromatic polyamide porous membrane, its preparation method and lithium-ion secondary battery [P]. China, CN201710043659.9), the film-making temperature of this scheme is easy to achieve, but the dense skin needs to be treated, and the preparation process is complicated
The Zhu Baoku team of Zhejiang University used this method to directly prepare a porous cortical sponge-like PMIA separator (Hong Zhang a, Yin Zhang a, Tiange Xu, et al. Poly(m-phenylene isophthalamide) separator for improving the heat resistance and power density of lithium- ion batteries[J].Journal of Power Sources,2016,329:8-16.), but the cycle stability of the separator can be further improved. After 50 cycles, the capacity retention rate is 91.8%, and the attenuation is 8.2%.

Method used

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  • Method for preparing porous meta-aramid diaphragm through non-solvent induced phase separation method
  • Method for preparing porous meta-aramid diaphragm through non-solvent induced phase separation method
  • Method for preparing porous meta-aramid diaphragm through non-solvent induced phase separation method

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Experimental program
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Effect test

Embodiment 1

[0031]Prepare the casting solution: blend 3% lithium bromide, 1% water and dimethylacetamide relative to the entire casting solution system, then slowly add it dropwise to the PMIA stock solution, stir, and add 0.5% glycerol , stirred for 12 hours until a uniform solution was obtained; then it was subjected to centrifugal degassing at 6000r / min to obtain a homogeneous transparent casting solution. Preparation of coagulation bath: use V (dimethylacetamide): V (glycerol) = 7: 3 to prepare coagulation bath solution C1; use V (dimethylacetamide): V (water) = 3: 7 to prepare coagulation bath solution C2; pour the prepared film casting solution on the forming substrate, and use a 100 μm scraper to scrape it into a film, and then put it in the coagulation bath C1 for 30 seconds; in the coagulation bath C2 for 30 seconds; finally put it into pure 12h in water. After the residual solvent was removed, the PMIA separator was rinsed with deionized water three times, and then dried in a v...

Embodiment 2

[0033] Prepare the casting solution: blend 1% lithium bromide, 3% water and dimethylformamide relative to the entire casting solution system, then slowly add it dropwise to the PMIA stock solution, and stir for 10 hours until a uniform solution is obtained; then It was subjected to centrifugal defoaming at 8000r / min to obtain a homogeneous transparent casting solution. Prepare coagulation bath: use V (dimethylformamide): V (glycerol) = 5:5 to prepare coagulation bath solution C1; use V (dimethylformamide): V (water) = 2:8 to prepare coagulation bath solution C2; pour the prepared film casting solution on the forming substrate, and use a 150 μm scraper to scrape it into a film, and then put it in the coagulation bath C1 for 120s; in the coagulation bath C2 for 120s; 12h in water. After the residual solvent was removed, the PMIA separator was rinsed with deionized water three times, and then dried in a vacuum oven at 60° C. for 12 hours to obtain a PMIA separator that can be us...

Embodiment 3

[0035] Prepare the casting solution: blend 4.5% calcium chloride and dimethyl sulfoxide relative to the entire casting solution system, then slowly add it dropwise to the PMIA stock solution, stir, add 1% glycerol, and stir for 6h Until a uniform solution is obtained; then it is subjected to centrifugal defoaming at 6000r / min to obtain a homogeneous transparent casting solution. Preparation of coagulation bath: use V (dimethyl sulfoxide): V (water) = 6: 4 to prepare coagulation bath solution C1; use pure water as coagulation bath solution C2; pour the prepared casting solution on the molding substrate, and use Scrape it with an 80 μm doctor blade to form a film, and then put it in the coagulation bath C1 for 30 seconds; in the coagulation bath C2 for 12 hours. After the residual solvent was removed, the PMIA separator was rinsed with deionized water three times, and then dried in a vacuum oven at 60° C. for 12 hours to obtain a PMIA separator that can be used in lithium-ion ba...

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Abstract

The invention discloses a method for preparing a porous meta-aramid diaphragm through a non-solvent induced phase separation method and an application of the porous meta-aramid diaphragm in a lithium ion battery diaphragm. According to the method disclosed by the invention, the porous meta-aramid diaphragm with an excellent epidermal pore structure and an excellent internal pore structure is prepared by adjusting the composition of a membrane casting solution, the composition of a coagulating bath and forming conditions and adopting a stepped coagulating bath. The porous meta-aramid diaphragm is high in porosity and uniform in structure, and the high-temperature-resistant diaphragm has excellent mechanical performance and wettability to an electrolyte so that reduction of a lithium ion transmission internal resistance is facilitated, and the electrochemical performance of a battery is improved; and the preparation process is simple, the forming time is short, the preparation process is easy to adjust, the energy consumption is low, and the method is suitable for large-scale industrial production.

Description

technical field [0001] The invention belongs to the technical field of polymer materials, and relates to a method for preparing a meta-aramid diaphragm, in particular to a method for preparing a porous meta-aramid diaphragm through an optimized non-solvent-induced phase separation method. Background technique [0002] Commercial lithium-ion battery separators mostly use polyolefin polymers as the preparation materials, including polyethylene, polypropylene or composite films of the above two materials. The application of polyolefin separators in small lithium-ion batteries can basically meet the requirements, but when applied to large-scale power lithium-ion batteries (electric vehicles, etc.), there are still the following defects: (1) Polyolefin separators have a negative effect on carbonate electrolytes. The wettability is poor, resulting in an increase in the internal resistance of the battery, resulting in low ionic conductivity; (2) When the battery temperature rises d...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M50/403H01M50/411H01M50/491H01M10/0525
CPCH01M50/403H01M50/411H01M50/491H01M10/0525Y02E60/10
Inventor 陈赞乔丽娜于海斌段翠佳袁标严硕郑秋红臧毅华
Owner CNOOC TIANJIN CHEM RES & DESIGN INST
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