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High density polyethylene lithium-ion battery separator with high porosity, and preparation method thereof

A technology of high-density polyethylene and lithium-ion batteries, which is applied to battery pack parts, circuits, electrical components, etc., can solve the problems of different pore sizes, uneven distribution, and excessive local resistance, etc. Different sizes, uniform micropore distribution, and the effect of improving performance

Active Publication Date: 2019-05-21
SICHUAN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

At present, there are mainly dry and wet methods for commercially preparing separators for lithium-ion batteries. The wet method is mainly prepared by thermally induced phase separation. The products have high porosity and uniform pore size distribution, and can be formed into ultra-high molecular weight polyethylene. It is used in the field of high-end lithium-ion battery separators, but because a large amount of organic solvents are used in the extraction stage, it will cause harm to the environment; the dry method mainly adopts the principle of hard elastomer separation, and there are two kinds of uniaxial stretching and biaxial stretching. The method of preparing the separator does not require the use of solvents and has no pollution to the environment, but this method is only suitable for polymers that can crystallize
There are a large number of micropores with different sizes, uneven distribution, and small number of micropores in the product of dry uniaxial stretching, which will cause the local resistance to be too large or too small, and the unstable current distribution will lead to lithium branches at the negative electrode. Crystal, the battery performance has been greatly affected

Method used

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  • High density polyethylene lithium-ion battery separator with high porosity, and preparation method thereof
  • High density polyethylene lithium-ion battery separator with high porosity, and preparation method thereof
  • High density polyethylene lithium-ion battery separator with high porosity, and preparation method thereof

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preparation example Construction

[0031] The invention provides a preparation method of a high-density polyethylene lithium-ion battery diaphragm, including extrusion casting and stretching, wherein the stretching process adopts a uniaxial stepwise stretching method, specifically: The oriented casting base film prepared by casting is stretched at a stretching rate of 100 mm / min to 300 mm / min at room temperature to obtain a strain of 10% to 60% along the casting direction to obtain initial micropores, and then stretched at 120 Fix the initial micropores by heat setting at ℃~130℃; then cool down to room temperature, and then continue to stretch along the casting direction at 80℃~100℃ at a tensile speed of 30mm / min~50mm / min for 30%~150 % strain to expand the initial micropores, and then heat-fixed at 120°C to 130°C (that is, stretching and heat-fixing steps again), and finally cooled to obtain a high-density polyethylene lithium-ion battery separator.

[0032] The purpose of the present invention is to solve the ...

Embodiment 1

[0042] A preparation method of a high-porosity HDPE lithium-ion battery separator, comprising the steps of:

[0043] 1) Preparation of highly oriented HDPE preset film: Add the screened HDPE (weight-average molecular weight of 200,000-500,000, Mw / Mn=5-12) into a twin-screw extruder for pre-mixing to form a HDPE pre-mixed master material; then the prepared masterbatch is uniformly plasticized by a single-screw extruder, the temperature of the single-screw extruder is set to 120°C, 190°C, 200°C, and the die temperature is 190°C; the speed of the extruder is 20rpm / min; the roll speed of the three-roll calender is 50mm / s, the roll temperature of the upper and middle rolls of the calender is set at 90°C, adjust the speed of the three-roll calender, and the prepared preset film The thickness is controlled at 40μm; the degree of orientation is 0.34;

[0044] 2) Preparation of microporous membrane: Stretch the prepared preset membrane to a strain of 30% at a stretching rate of 200mm / ...

Embodiment 2

[0046] A preparation method of a high-porosity HDPE lithium-ion battery separator, comprising the steps of:

[0047] 1) Preparation of highly oriented HDPE preset film: Add the screened HDPE to a twin-screw extruder for premixing to form a HDPE premix masterbatch; then uniformly plasticize the prepared masterbatch through a single-screw extruder. The temperature of the screw extruder is set to 120°C, 190°C, 200°C, and the die temperature is 190°C; the speed of the extruder is 10rpm / min; the roll speed of the three-roll calender is 50mm / s, Set the roll temperature of the middle two rolls to 90°C, adjust the speed of the three-roll calender, and control the thickness of the prepared preset film at 20 μm;

[0048] 2) Preparation of microporous membrane: Stretch the prepared pre-membrane to a strain of 20% at a stretching rate of 200mm / min at room temperature, heat-set at 120°C for 10min, and then cool down to room temperature , and at this temperature, continue to stretch 20% of...

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Abstract

The invention belongs to the field of separators, and relates to a lithium-ion battery separator and a preparation method thereof. The invention provides a preparation method of a high density polyethylene lithium-ion battery separator with high porosity, comprising extrusion casting and stretching, wherein the stretching process adopts a uniaxial stepwise stretching method, comprising: stretchingan oriented casting base film along the casting direction at a stretching rate of 100mm / min to 300mm / min under a room temperature condition for a deformation amount of 10-60%, and performing heat setting at 120-130 DEG C; then cooling to the room temperature, and continuing to stretch the oriented casting base film along the casting direction at the same stretching rate as the first time for thesame deformation amount; stretching the oriented casting base film at a stretching rate of 30mm / min to 50mm / min for a deformation amount of 30-150%, and performing heat setting at 120-130 DEG C; and finally performing cooling to obtain the lithium-ion battery separator. The obtained separator has high porosity, uniform pore size and uniform pore distribution.

Description

technical field [0001] The invention belongs to the field of lithium battery diaphragm processing, and in particular relates to a lithium ion battery diaphragm prepared by uniaxial stretching and a preparation method thereof. Background technique [0002] At present, the world is facing the problems of energy shortage and environmental degradation. In order to meet energy demand and reduce dependence on fossil energy, many sustainable and environmentally friendly energy storage technologies have emerged in the world, such as mechanical energy storage, electrical energy storage, electrochemical energy storage, thermal energy storage and chemical energy storage. Among them, the battery is a kind of electrochemical energy storage, and its development has an important impact on the sustainability and regeneration of resources. Compared with other secondary batteries, lithium batteries have the following advantages: high specific energy, the specific energy density of lithium-io...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M2/14H01M2/18H01M2/16B29C48/08B29C48/92B29K23/00H01M50/403H01M50/417H01M50/491
CPCY02E60/10
Inventor 杨鸣波陈文博刘正英吴高高张娅丁超
Owner SICHUAN UNIV
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