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Polyethylene microporous membrane, preparation method and lithium ion battery

A technology of polyethylene microporous membrane and lithium-ion battery, which is applied to battery components, circuits, electrical components, etc., can solve problems such as poor air permeability and cycle performance, accelerated self-discharge speed, and slow self-discharge speed, and achieves Enhanced puncture resistance, good self-discharge performance, and the effect of preventing short circuits

Active Publication Date: 2015-02-18
乐凯胶片股份有限公司 +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, when the microporous membrane with the same pore size on both sides is used in lithium-ion batteries, there are the following problems: when the pore size is large, such as when the average pore size is greater than 150nm, its internal resistance is low, the gas permeability is good, and the cycle performance is good. , but its puncture strength is low, the safety performance is poor, and the self-discharge speed will also be accelerated
When the pore size is small, such as when the average pore size is less than 70nm, the puncture strength is high, the safety performance is good, and the self-discharge speed is slow, but due to the large internal resistance, the air permeability and cycle performance become very poor.

Method used

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  • Polyethylene microporous membrane, preparation method and lithium ion battery
  • Polyethylene microporous membrane, preparation method and lithium ion battery
  • Polyethylene microporous membrane, preparation method and lithium ion battery

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preparation example Construction

[0041] 2. Preparation method of polyethylene microporous membrane

[0042] Description of raw materials and process parameters

[0043] The present invention has no special limitation on the polyethylene resin used, generally a single resin can be used, or two or more resins can be used in combination.

[0044] In the present invention, the weight-average molecular weight of the polyethylene resin used is not particularly limited, generally speaking, it is 10,000-5 million, preferably 100,000-3 million, and more preferably 300,000-2 million.

[0045] The present invention has no special limitation on the pore-forming agent used, usually liquid paraffin, solid paraffin, dioctyl phthalate, dibutyl phthalate and other solvents that have a pore-forming effect on polyolefin resins. The pore forming agent may be used alone or in combination of two or more. Liquid paraffin and dioctyl phthalate are preferred.

[0046] The present invention is not particularly limited to the ...

Embodiment 1

[0062] (1) Extrusion casting: inject polyethylene resin and liquid paraffin into a twin-screw extruder, and melt and knead them into a uniform melt in the twin-screw. Then the melt is continuously extruded from the die, and rapidly cooled and shaped by cooling rollers to obtain thick sheets. Wherein, the weight average molecular weight of the polyethylene resin is 500,000, and the viscosity grade of the liquid paraffin is 40. The mass ratio of polyolefin resin to liquid paraffin is 1:3, the melting temperature is 200°C, and the temperature of the cooling roll is 30°C.

[0063] (2) Biaxial stretching: stretch the thick sheet in a stretching machine after preheating. Among them, the stretching temperature of the upper chamber is 120°C, the stretching temperature of the lower chamber is 115°C, and the temperature difference between the upper and lower chambers is 5°C to obtain an oily film;

[0064] (3) Extraction: Extract the liquid paraffin in the oily film with dichlorometha...

Embodiment 2

[0069] (1) Extrusion casting: inject polyethylene resin and liquid paraffin into a twin-screw extruder, and melt and knead them into a uniform melt in the twin-screw. Then the melt is continuously extruded from the die, and rapidly cooled and shaped by cooling rollers to obtain thick sheets. Wherein, the weight average molecular weight of the polyethylene resin is 1 million, and the viscosity grade of the liquid paraffin is 40. The mass ratio of polyolefin resin to liquid paraffin is 1:4, the melting temperature is 200°C, and the temperature of the cooling roll is 30°C.

[0070] (2) Biaxial stretching: stretch the thick sheet in a stretching machine after preheating. Among them, the stretching temperature of the upper chamber is 125°C, the stretching temperature of the lower chamber is 115°C, and the temperature difference between the upper and lower chambers is 10°C to obtain an oily film;

[0071] (3) Extraction: Extract the liquid paraffin in the oily film with dichlorome...

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Abstract

The invention provides a polyethylene microporous membrane, a preparation method and a lithium ion battery. The polyethylene microporous membrane comprises a front side and a reverse side, wherein the average aperture size of the front side is 100 to 200nm; the average aperture size of the reverse side is 50 to 100nm; the average aperture size ratio A:B of the front side and the reverse side is 1.1 to 4.0:1; the aperture size distribution is smaller than 30 percent. When the microporous membrane prepared through the preparation method is applied in the lithium ion battery, the front side is close to the positive pole of the battery and the reverse side is close to the negative pole of the battery, so that the polyethylene microporous membrane not only has a good high-rate discharge performance, but also has a good self-discharge performance.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to a polyethylene microporous membrane, a preparation method and a lithium ion battery using the microporous membrane. Background technique [0002] Polyolefin microporous membrane is a porous membrane with microporous structure on both sides. When used as a lithium-ion battery separator, the existence of the separator must first satisfy that it cannot deteriorate the electrochemical performance of the battery. Its suitable submicron pore size is one of the important indicators to meet the requirements of battery charge and discharge performance, safety performance, cycle performance and other aspects. [0003] For any battery application, the separator should have a uniform pore size distribution to avoid inconsistent current densities that would degrade battery performance. The submicron sized pore size is critical to prevent short circuits between positive and neg...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M2/16H01M50/403H01M50/417H01M50/491
CPCH01M50/44H01M50/403Y02E60/10
Inventor 宋红芹韩继庆张永升千昌富
Owner 乐凯胶片股份有限公司
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