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A kind of preparation method of high temperature resistant co-extruded uniaxially stretched microporous diaphragm and microporous diaphragm

A microporous diaphragm, uniaxial stretching technology, applied in the direction of separator/film/diaphragm/spacer element, structural parts, electrical components, etc., can solve the problem of limited matrix adhesion, poor extrusion processing performance, inorganic powder Body shedding and other problems, to achieve the effect of increased closed-cell temperature and film-breaking temperature, good high temperature resistance, and uniform pore size distribution

Active Publication Date: 2020-11-13
GUANGDONG UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This type of method uses the heat resistance of high-temperature resistant polymers to improve the performance of instantaneous thermal shock resistance, but the uniformity of pores obtained by electrospinning and coating methods is poor, and the adhesion to the substrate is limited, which will cause problems during long-term cycling. Formation of lithium dendrites endangers battery safety
[0005] Another technical 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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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0036] The polyphenylene sulfide with a melting index of 3g / 10min and polytetramethyl-monopentene with a melting index of 5g / 10min were added to different extruders respectively, and co-extruded through a multi-layer die, and the polyphenylene sulfide layer and the polytetramethylene The final temperature of the methyl-pentene layer casting machine was 280°C and 230°C respectively, the die temperature was 290°C, the casting roll temperature was 120°C, and the melt stretching ratio was 1.5, and the three-layer polymer was obtained by casting. The phenylene sulfide / polytetramethylmonopentene / polyphenylene sulfide composite casting film, wherein the screw speed of the polytetramethylmonopentene layer is 40 rpm, and the screw speed of the polyphenylene sulfide layer is 20 rpm. Heat treatment at 180°C for 0.3h to obtain a multilayer heat treatment film. One-stage stretching was performed at 150°C with a stretching rate of 5 mm / min and a stretching ratio of 20%, followed by a second...

Embodiment 2

[0038] The polyphenylene sulfide with a melting index of 8g / 10min and polytetramethylmonopentene with a melting index of 30g / 10min were added to different extruders respectively, and co-extruded through a multi-layer die, and the polyphenylene sulfide layer and the polytetramethylene The final temperature of the methyl-pentene layer casting machine was 290 °C and 260 °C respectively, the die temperature was 290 °C, the casting roll temperature was 180 °C, and the melt stretching ratio was 20. The phenylene sulfide / polytetramethylmonopentene / polyphenylene sulfide composite casting film, wherein the screw speed of the polytetramethylmonopentene layer is 60 rpm, and the screw speed of the polyphenylene sulfide layer is 40 rpm. Heat treatment at 220 °C for 2 h to obtain a multilayer heat treatment film. One-stage stretching was performed at 180°C with a stretching rate of 50 mm / min and a stretching ratio of 80%, followed by a second-stage stretching at 240°C with a stretching rate...

Embodiment 3

[0040]The polyphenylene sulfide with a melting index of 5g / 10min and polytetramethyl-monopentene with a melting index of 10g / 10min were added to different extruders respectively, and co-extruded through a multi-layer die, and the polyphenylene sulfide layer and the polytetramethylene The final temperature of the methyl-pentene layer casting machine was 280 °C and 240 °C respectively, the die temperature was 290 °C, the casting roll temperature was 150 °C, and the melt stretching ratio was 10. The phenylene sulfide / polytetramethylmonopentene / polyphenylene sulfide composite casting film, wherein the screw speed of the polytetramethylmonopentene layer is 50 rpm, and the screw speed of the polyphenylene sulfide layer is 30 rpm. Heat treatment at 200 °C for 0.8 h to obtain a multi-layer heat-treated film. One-stage stretching was performed at 180°C with a stretching rate of 50 mm / min and a stretching ratio of 80%, followed by a second-stage stretching at 240°C with a stretching rat...

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Abstract

The invention provides a method for preparing a high-temperature resistant co-extruded uniaxially stretched microporous membrane, which comprises the following steps: A) using three extrusion casting machines to respectively prepare polyphenylene sulfide and polytetramethylpentene The resin is melted and extruded, and multi-layer composite cast film is obtained through multi-layer die casting; wherein, polyphenylene sulfide is located in the outer layer, and polytetramethyl-pentene resin is located in the middle layer; B) the multi-layer composite cast film The film is heat-treated at 180-220°C for 0.3-2h to obtain a multi-layer heat-treated film; C) at 150-180°C, the multi-layer heat-treated film is stretched in the first stage, and the stretch ratio is 20%-80%; D) in 220-240°C, stretch the multilayer heat-treated film in the second stage, and the stretching ratio is 100%-120%; E) The microporous film obtained after the above-mentioned second stage stretching is set at 240-250°C for 1~ 5min to obtain a microporous membrane. The invention finally obtains a microporous diaphragm with uniform structure and high temperature resistance.

Description

technical field [0001] The invention relates to the technical field of isolation film production, in particular to a preparation method of a high temperature resistant co-extrusion uniaxially stretched microporous diaphragm and the microporous diaphragm. Background technique [0002] The separator is the core component of the lithium-ion battery, accounting for about 18%-30% of the cost of the entire lithium-ion battery. The quality of its performance plays a crucial role in the overall performance of the lithium-ion battery. Charging technology and battery cycle performance requirements at high rates are increasing, and the danger of battery explosion caused by battery self-heating has become increasingly prominent. High temperature resistance and high safety lithium battery separators have become an urgent need in the industry. [0003] At present, lithium-ion battery separators are mainly crystalline polyolefin materials such as polyethylene (PE) and polypropylene (PP), w...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01M2/14H01M2/18H01M50/403H01M50/411H01M50/417H01M50/449H01M50/457H01M50/491
CPCH01M50/403H01M50/463Y02E60/10
Inventor 徐睿杰谢嘉宜雷彩红
Owner GUANGDONG UNIV OF TECH
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