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A preparation method of self-flame-retardant co-extruded uniaxially stretched microporous diaphragm and microporous diaphragm

A microporous diaphragm, uniaxial stretching technology, applied in structural parts, electrical components, battery pack parts, etc., can solve the problem that the characteristics of polyolefin materials cannot meet the needs of high heat-resistant lithium battery separators, and the heat resistance of the separators No improvement, poor extrusion processing performance, etc., to achieve the effects of good high temperature resistance, uniform pore size distribution, and improved safety

Active Publication Date: 2021-02-02
GUANGDONG UNIV OF TECH
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Problems solved by technology

[0004] For example, the PP / PE / PP three-layer composite separator developed by Celgard can maintain the safety of the battery to a certain extent by providing a large temperature difference between closed cells and membrane rupture, but the main materials are still polypropylene and polyethylene. , the heat resistance of the separator has not improved, and the safety of the battery is still limited
[0005] The coating method is to coat an inorganic layer on the surface of the polyolefin diaphragm, and use the inorganic layer to improve the dimensional stability of the polyolefin diaphragm at high temperature and improve the safety of the diaphragm, but the thickness of the inorganic coating is only 2- 3 microns, safety is still difficult to guarantee under instantaneous thermal shock at high temperature
At the same time, the inorganic powder is bonded to the surface of the separator with a polymer binder, which will cause the inorganic powder to fall off and dissociate under long-term immersion in the electrolyte, and the impact on battery safety is not yet clear.
[0006] At present, there is still the technology of producing polyolefin porous membrane by melt stretching method, but the material characteristics of polyolefin itself cannot meet the needs of high heat resistance lithium battery separator
Another study shows that using semi-crystalline high-temperature-resistant materials instead of existing polyolefin materials to co-extrude composite diaphragms can fundamentally solve the problem of heat resistance. However, due to the poor extrusion processing performance of materials, only a single layer Extrusion, separation of film layers due to interlaminar shear of different melts and control of initial lamella structure, the use of semi-crystalline high-temperature resistant materials to prepare multilayer microporous separators has not been reported so far

Method used

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  • A preparation method of self-flame-retardant co-extruded uniaxially stretched microporous diaphragm and microporous diaphragm

Examples

Experimental program
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Effect test

Embodiment 1

[0039] Add polyphenylene sulfide with a melt index of 3g / 10min and polypropylene with a melt index of 1g / 10min into different extruders respectively, and co-extrude through a multi-layer die head. The final temperature is 280°C and 230°C respectively, the die head temperature is 290°C, the casting roll temperature is 120°C, the melt draw ratio is 1.5, and three-layer polyphenylene sulfide / polypropylene / polyphenylene sulfide is obtained by casting Ether composite cast film. Heat treatment at 100°C for 8h. One-stage stretching was carried out at 80°C with a stretching rate of 5 mm / min and a stretching ratio of 3%, followed by two-stage stretching at 130°C with a stretching rate of 50 mm / min and a stretching ratio of 100%. The heat-setting temperature is 140°C, the heat-setting time is 3min, and thermal shock is performed in a hot air furnace at 240°C for 5 seconds to obtain a three-layer polyphenylene sulfide / polypropylene / polyphenylene sulfide microporous film. The porosity of...

Embodiment 2

[0041]Add polyphenylene sulfide with a melt index of 12g / 10min, polypropylene with a melt index of 5g / 10min, and random copolymers of propylene and ethylene with a molecular weight of 9000Da and 5% of the mass fraction of polypropylene into different extruders respectively. Layer die head co-extrusion, the end temperature of polyphenylene sulfide layer and polypropylene layer casting machine is 290 ℃ and 260 ℃, the temperature of die head is 290 ℃, the temperature of casting roll is 120 ℃, the melt draw ratio was 20, cast to obtain a three-layer polyphenylene sulfide / polypropylene mixture / polyphenylene sulfide composite cast film. Heat treatment at 150°C for 20h. One-stage stretching was carried out at 80°C with a stretching rate of 50mm / min and a stretching ratio of 20%, followed by two-stage stretching at 140°C with a stretching rate of 150mm / min and a stretching ratio of 110%. The heat-setting temperature is 145°C, the heat-setting time is 4min, and thermal shock is perfor...

Embodiment 3

[0043] Add polyphenylene sulfide with a melt index of 5g / 10min, polypropylene with a melt index of 3g / 10min, and a random copolymer of propylene and butene with a molecular weight of 20% of polypropylene and a molecular weight of 40,000Da into different extruders. Multi-layer die head co-extrusion, the end temperature of polyphenylene sulfide layer and polypropylene layer casting machine are 280 ℃ and 260 ℃ respectively, the temperature of die head is 290 ℃, the temperature of casting roll is 120 ℃, the melt draw The elongation ratio is 4, and a three-layer polyphenylene sulfide / polypropylene mixture / polyphenylene sulfide composite cast film is obtained by casting. Heat treatment at 110°C for 12h. One-stage stretching was performed at 80°C with a stretching rate of 50mm / min and a stretching ratio of 10%, followed by two-stage stretching at 130°C with a stretching rate of 50mm / min and a stretching ratio of 100%. The heat-setting temperature is 140°C, the heat-setting time is 3...

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Abstract

The invention provides a method for preparing a self-flame-retardant co-extruded uniaxially stretched microporous diaphragm, comprising the following steps: A) using three extrusion casting machines to respectively prepare polyphenylene sulfide and polypropylene or a copolymer containing polypropylene Polypropylene mixed resin is melt-extruded, and multi-layer composite cast film is obtained through multi-layer die casting; among them, polyphenylene sulfide is located in the outer layer, and polypropylene or polypropylene mixed resin containing polypropylene copolymer is located in the middle layer ; B) heat-treating the multi-layer composite cast film at 100-150°C for 8-20 hours to obtain a multi-layer heat-treated film; C) stretching the multi-layer heat-treated film at 80°C for the first stage, and the draw ratio is 3%-20 %; D) 130 ~ 140 ℃ for the second stage of stretching the multi-layer heat treatment film, the stretching ratio is 100% ~ 120%; E) the microporous film obtained after the above second stage stretching Shaping for 3 to 4 minutes, and then thermal shock shaping at 240°C for 5 to 8 seconds to obtain a microporous diaphragm.

Description

technical field [0001] The invention relates to the technical field of isolation membrane production, in particular to a preparation method of a self-flame-retardant co-extrusion uniaxially stretched microporous membrane and the microporous membrane. Background technique [0002] The diaphragm is the core component of the lithium-ion battery, accounting for about 18%-30% of the cost of the entire lithium battery. Its performance plays a vital role in the overall performance of the lithium battery. With the development of power batteries, the rapid The requirements for charging technology and battery cycle performance under high magnification are increasing day by day, and the danger of battery explosion caused by battery self-heating is becoming more and more prominent. High temperature resistant and high safety lithium battery separator has become an urgent need in the industry. [0003] At present, lithium-ion battery separators are mainly crystalline polyolefin materials ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01M50/403H01M50/417H01M50/457H01M10/0525
CPCH01M10/0525H01M50/403H01M50/411H01M50/449Y02E60/10
Inventor 徐睿杰谢嘉宜雷彩红
Owner GUANGDONG UNIV OF TECH
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